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Lapage SP, Sneath PHA, Lessel EF, et al., editors. International Code of Nomenclature of Bacteria: Bacteriological Code, 1990 Revision. Washington (DC): ASM Press; 1992.

Cover of International Code of Nomenclature of Bacteria

International Code of Nomenclature of Bacteria: Bacteriological Code, 1990 Revision.

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Chapter 3Rules of Nomenclature with Recommendations

Section 1. General

Rule 1a

This revision supersedes all previous editions of the International Code of Nomenclature of Bacteria (see Appendix 1). It shall be cited as Bacteriological Code (1990 Revision) and will apply from the date of publication (1992).

Rule 1b

Alterations to this Code can only be made by the ICSB at one of its plenary sessions. Proposals for modifications should be made to the Editorial Secretary in sufficient time to allow publication in the IJSB before the next International Congress of Bacteriology. For this and other Provisions, see the Statutes of the ICSB, pp. 137–158.

Rule 2

The Rules of this Code are retroactive, except where exceptions are specified.

Rule 3

Names contrary to a Rule cannot be maintained, except that the International Committee on Systematic Bacteriology, on the recommendation of the Judicial Commission, may make exceptions to the Rules (see Rule 23a and the Statutes of the ICSB).

Rule 4

In the absence of a relevant Rule or where the consequences of a Rule are uncertain, a summary in which all pertinent facts are outlined should be submitted to the Judicial Commission for consideration (see Appendix 8 for preparation of a Request for an Opinion).

Section 2. Ranks of Taxa

Rule 5a

Definitions of the taxonomic categories will inevitably vary with individual opinion, but the relative order of these categories may not be altered in any classification.

Rule 5b

The taxonomic categories above and including species which are covered by these Rules are given below in ascending taxonomic rank. Those in the left-hand column should be recognized where pertinent; those in the right-hand column are optional. The Latin equivalents are given in parentheses.

Species (Species)
Subgenus (Subgenus)
Genus (Genus)
Subtribe (Subtribus)
Tribe (Tribus)
Subfamily (Subfamilia)
Family (Familia)
Suborder (Subordo)
Order (Ordo)
Subclass (Subclassis)
Class (Classis)

Rule 5c

A species may be divided into subspecies, which are dealt with by the Rules of this Code. Variety is a synonym of subspecies; its use is not encouraged as it leads to confusion, and after publication of this Code the use of the term variety for new names will have no standing in nomenclature.

Rule 5d

Taxa below the rank of subspecies (infrasubspecific subdivisions) are not covered by the Rules of this Code, but see Appendix 10.

Section 3. Naming of Taxa

GeneraI

Rule 6

The scientific names of all taxa must be treated as Latin; names of taxa above the rank of species are single words.

Recommendation 6

To form new bacterial names and epithets, authors are advised as follows.

  1. Avoid names or epithets that are very long or difficult to pronounce.
  2. Make names or epithets that have an agreeable form that is easy to pronounce when latinized.
  3. Avoid combining words from different languages, hybrid names (nomina hybrida).
  4. Do not adopt unpublished names or epithets found in authors' notes, attributing them to the authors of such notes, unless these authors have approved publication.
  5. Give the etymology of new generic names and of new epithets.
  6. Determine that the name or epithet which they propose is in accordance with the Rules.

Names of Taxa above the Rank of Genus up to and including Order

Rule 7

The name of a taxon above the rank of genus up to and including order is a substantive or an adjective used as a substantive of Latin or Greek origin, or a latinized word. It is in the feminine gender, the plural number, and written with an initial capital letter.

Example: Family Pseudomonadaceae.

Historically, all these names were feminine plural adjectives qualifying the word "plantae" plants; in modern bacterial nomenclature they qualify the word "procaryotae."

Example: Plantae pseudomonadaceae; Procaryotae pseudomonadaceae.

In practice, such names are used alone and as substantives.

Example: A member of the Pseudomonadaceae.

Names of Taxa above the Rank of Order

Rule 8

The name of each taxon above the rank of order is a Latin or latinized word preferably in conformity with Recommendation 6. It is based by choice on a combination of characters of the taxon or from a single character of outstanding importance.

Example: Kingdom—Procaryotae; Class—Schizomycetes.

Names of Taxa between Subclass and Genus (Order, Suborder, Family, Subfamily, Tribe, Subtribe)

Rule 9

The name of a taxon between subclass and genus is formed by the addition of the appropriate suffix to the stem of the name of the type genus (see Rule 15). These suffixes are as follows:

Table 1Suffixes for Categories

RankSuffixExample
Order-alesPseudomonadales
Suborder-ineaePseudomonadineae
Family-aceaePseudomonadaceae
Subfamily-oideaePseudomonadoideae
Tribe-eaePseudomonadeae
Subtribe-inaePseudomonadinae

Names of Genera and Subgenera

Rule 10a

The name of a genus or subgenus is a substantive, or an adjective used as a substantive, in the singular number and written with an initial capital letter. The name may be taken from any source and may even be composed in an arbitrary manner. It is treated as a Latin substantive.

Examples: Single Greek stem, Clostridium; two Greek stems, Haemophilus; single Latin stem, Spirillum; two Latin stems, Lactobacillus; hybrid name, Latin-Greek stems, Flavobacterium; latinized personal name, Shigella; arbitrary name, Ricolesia.

Recommendation 10a

The following Recommendations apply when forming new generic or subgeneric names.

  1. Refrain from naming genera and subgenera after persons quite unconnected with bacteriology or at least with natural science.
  2. Give a feminine form to all personal generic and subgeneric names whether they commemorate a man or a woman.
  3. Avoid introducing into bacteriology as generic names such names as are in use in botany or zoology, in particular well-known names.

Rule 10b

Generic and subgeneric names are subject to the same Rules and Recommendations, except that Rule 10c applies only to subgeneric names.

Rule 10c

The name of a subgenus, when included with the name of a species, is placed in parentheses along with the abbreviation subgen. between the generic name and specific epithet. When included, the citation should be inserted before closure of the parentheses.

Example: Bacillus (subgen. Bacillus Cohn 1872, 174) subtilis; Bacillus (subgen. Aerobacillus Donker 1926, 128) polymyxa (see Rules 43 and 46).

Names of Taxa between Subgenus and Species

Rule 11

The taxonomic categories section, subsection, series, and subseries are informal categories not regulated by the Rules of this Code. Their designations do not compete with the names of genera and subgenera as to priority and homonymy.

Note. Priority (see Section 5A) means that the name or epithet first published in accordance with the Rules is the correct name, or epithet, for a taxon (see Rule 23a). Homonymy is the term applied when the same name is given to two or more different taxa of the same rank based on different types. The first published name is known as the senior homonym and any later published name as a junior homonym.

Names of Species

Rule 12a

The name of a species is a binary combination consisting of the name of the genus followed by a single specific epithet.

If a specific epithet is formed from two or more words, then the words are to be joined. If the words were not joined in the original publication, then the epithet is not to be rejected but the form is to be corrected by joining the words, which can be done by any author. If an epithet has been hyphenated, its parts should be joined. The name retains its validity and standing in nomenclature.

Example: Salmonella typhi murium should be corrected to Salmonella typhimurium.

Rule 12b

No specific or subspecific epithets within the same genus may be the same if based on different types (see Rule 13c and Section 9).

Example: Corynebacterium helvolum (Zimmermann 1890) Kisskalt and Berend 1918 is based on the type of Bacillus helvolus Zimmermann 1890; the specific epithet helvolum cannot be used for Corynebacterium helvolum Jensen 1934, another bacterium whose name is based on a different type.

Rule 12c

A specific epithet may be taken from any source and may even be composed arbitrarily.

Example: etousae in Shigella etousae derived from European Theater of Operations of the U.S. Army.

A specific epithet must be treated in one of the three following ways.

  1. As an adjective that must agree in gender with the generic name.
    Example: aureus in Staphylococcus aureus.
  2. As a substantive (noun) in apposition in the nominative case.
    Example: radicicola in Bacillus radicicola.
  3. As a substantive (noun) in the genitive case.
    Example: lathyri in Erwinia lathyri.

Recommendation 12c

Authors should attend to the following Recommendations, and those of Recommendation 6, when forming specific epithets.

  1. Choose a specific epithet that, in general, gives some indication of a property or of the source of the species.
  2. Avoid those that express a character common to all, or nearly-all, the species of a genus.
  3. Ensure that, if taken from the name of a person, it recalls the name of one who discovered or described it, or was in some way connected with it, and possesses the appropriate gender (see Appendix 9A).
  4. Avoid in the same genus epithets which are very much alike, especially those that differ only in their last letters.
  5. Avoid the use of the genitive and the adjectival forms of the same specific epithet to refer to two different species of the same genus (see Rule 63).

Names of Subspecies

Rule 13a

The name of a subspecies is a ternary combination consisting of the name of a genus followed by a specific epithet, the abbreviation "subsp." (subspecies), and finally the subspecific epithet.

Example: Bacillus cereus subsp. mycoides (Flügge 1886) Smith et al. 1946.

For "variety" see Rule 5c.

Rule 13b

A subspecific epithet is formed in the same way as a specific epithet. When adjectival in form, it agrees in gender with the generic name.

Rule 13c

No two subspecies within the same species or within the same genus may bear the same subspecific epithet (see also Rule 12b).

Rule 13d

A subspecies that includes the type of the species must bear the same epithet as the species (see also Rules 45 and 46).

Names of Infrasubspecific Subdivisions

Rule 14a

The designations of the various taxa below the rank of subspecies are not subject to the Rules and Recommendations of this Code. (For advice on their nomenclature, see Appendix 10.)

Rule 14b

A Latin or latinized infrasubspecific designation may be elevated by a subsequent author to the status of a subspecies or species name providing that the resulting name is in conformity with the Rules. If so elevated, it ranks for purposes of priority from its date of elevation and is attributed to the author by whom it was elevated, provided that the author who elevates it observes Rule 27.

Example: Leptospira javanica Collier 1948, elevation of Leptospira sp. serovar javanica of Essevald and Mochtar 1938 by Collier in 1948.

Section 4. Nomenclatural Types and Their Designation

General

Rule 15

A taxon consists of one or more elements. For each named taxon of the various taxonomic categories (listed below), there shall be designated a nomenclatural type. The nomenclatural type, referred to in this Code as "type," is that element of the taxon with which the name is permanently associated. The nomenclatural type is not necessarily the most typical or representative element of the taxon. The types are dealt with in Rules 16–22.

Types of the various taxonomic categories can be summarized as follows:

Table 2Taxonomic Categories

Taxonomic categoryType
Subspecies Species}Designated strain; in special cases the place of the type strain may be taken by a description, preserved specimen, or an illustration
Subgenus Genus}Designated species
Subtribe Tribe
Subfamily Family
Suborder Order}
Genus on whose name the name of the higher taxon is based
Subclass Class}One of the contained orders

Rule 16

After the date of publication of this Code, the type of a taxon must be designated by the author at the time the name of the taxon is published in the IJSB (see Rule 27).

Note. Authors who intend to publish the name in the IJSB with reference to a previous effectively published description under Rule 27(2) are advised also to designate the type when publishing that description.

Rule 17

The type determines the application of the name of a taxon if the taxon is subsequently divided or united with another taxon.

Example: If the genus Bacillus is divided into the genera Bacillus and Aerobacillus, the genus which contains the type species, Bacillus subtilis, must be named Bacillus.

Type of a Species or Subspecies

Rule 18a

Whenever possible, the type of a species or subspecies is a designated strain.

A type strain is made up of living cultures of an organism which are descended from a strain designated as the nomenclatural type. The strain should have been maintained in pure culture and should agree closely in its characters with those in the original description (see Chapter 4C). The type strain may be designated in various ways (see Rule 18b, c, and d).

For a species which has not so far been maintained in laboratory culture or for which a type strain does not exist, a description, preserved specimen, or illustration (see also Rule 18f) may serve as the type.

Example: Noncultivated, Oscillospira guilliermondii Chatton and Perard 1913.

Rule 18b Designation by original author

If the author in the original publication of the name of a species or subspecies definitely designated a type strain, then this strain shall be accepted as the type strain and may be referred to as the holotype.

Rule 18c Designation as neotype

If a strain on which the original description was based cannot be found, a neotype strain may be proposed.

A neotype strain must be proposed (proposed neotype) in the IJSB, together with citation of the author(s) of the name, a description or reference to an effectively published description, and a record of the permanently established culture collection(s) where the strain is deposited (see also Note 1 to Rule 24a).

The author should show that a careful search for the strains used in the original description has been made and that none of them can be found. The author should also demonstrate that the proposed neotype agrees closely with the description given by the original author.

The neotype becomes established (established neotype) two years after the date of its publication in the IJSB, provided that there are no objections, which must be referred within the first year of the publication of the neotype to the Judicial Commission for consideration.

Rule 18d

A strain suggested as a neotype but not formally proposed in accordance with the requirements of Rule 18c (suggested neotype) has no standing in nomenclature until formally proposed and established.

Rule 18e

If an original strain that should constitute the type of a species is discovered subsequent to the formal proposal or establishment of a neotype for that species, the matter shall be referred immediately to the Judicial Commission.

Rule 18f

If a description or illustration constitutes, or a dead preserved specimen has been designated as, the type of a species (Rule 18a, para 3) and later a strain of this species is cultivated, then the type strain may be designated by the person who isolated the strain or by a subsequent author. This type strain shall then replace the description, illustration, or preserved specimen as the nomenclatural type.

Rule 18g Change in characters of type and neotype strains

If a type or neotype strain has become unsuitable owing to changes in its characters or for other reasons, then the matter should be referred to the Judicial Commission, which may decide to take action leading to replacement of the strain.

Rule 19 Reference strains

A reference strain is a strain that is neither a type nor a neotype strain but a strain used in comparative studies, e.g., taxonomic or serological, or for chemical assay.

A reference strain has no standing in nomenclature, but it may, by subsequent action, be made a neotype.

Type of a Genus

Rule 20a

The nomenclatural type of a genus or subgenus is the type species, that is, the single species or one of the species included when the name was originally validly published.

Rule 20b Designation by original author

If the author of the original publication of a generic or subgeneric name designated a type species, that species shall be accepted as the type species.

Rule 20c Genus with only one species

If the genus when originally published included only one species, then that species is the type species.

Rule 20d Designation by a subsequent author

The type species shall be selected from one of the species included when the genus was originally published.

Recommendation 20d

Authors are recommended to exclude the following species from consideration in selecting the type.

  1. Doubtfully identified or inadequately characterized species.
    Example: Lactobacillus caucasicus Beijerinck 1901 (Opinion 38).
  2. Species doubtfully referred to the genus.
    Example: No example yet found.
  3. Species which definitely disagree with the generic description.
    Example: Halococcus Utoralis (Poulsen) Schoop 1935.
  4. Species mentioned as in any way exceptional, including species which possess characters stated in the generic description as rare or unusual.
    Example: Pseudomonas mallei (Zopf) Redfearn et al. 1966.

Rule 20e Designation by international agreement

  1. If none of the species named by an author in the original publication of a generic name can be recognized, i.e., if no identifiable type species can be selected in accordance with the Rules, the Judicial Commission may issue an Opinion declaring such generic name to be a rejected name (nomen rejiciendum) and without standing in nomenclature (see Rule 23a, Note 4).
    Example: Rejection of the generic name Gaffkya Trevisan 1885 (Opinion 39).
  2. However, a generic name for which no identifiable type species can be selected in accordance with the Rules might have come into use for identifiable species which were subsequently named. In this case, one of these later species may be selected as the type species and established as such by an Opinion of the Judicial Commission. The generic name is then ascribed to the author of the name of the species selected as the type species.
    Example: Vibrio Pacini 1854 and its type species Vibrio cholerae Pacini 1854 (Opinion 31).

Rule 20f Retention of type species on publication of a new generic name

The publication of a new generic name as a deliberate substitute for an earlier one does not change the type species of the genus.

Example: The deliberate creation of Xanthomonas as a substitute for the name Phytomonas (not available, as it was already in use as the name of a protozoan genus) does not change the type species, which was Phytomonas campestris and which became Xanthomonas campestris.

Type of a Subgenus

Rule 20g

A genus and its type subgenus share the same type species.

Example: Bacillus subtilis is the type species of the genus Bacillus and of its type subgenus, Bacillus.

Type of a Taxon from Genus to Order (Subtribe, Tribe, Subfamily, Family, Suborder, and Order)

Rule 21a

The nomenclatural type of a taxon above genus, up to and including order, is the genus on whose name the name of the relevant taxon is based. One taxon of each category must include the type genus. The names of the taxa which include the type genus must be formed by the addition of the appropriate suffix to the stem of the name of the type genus (see Rule 9).

Example: Order, Rhodospirillales; suborder. Rhodospirillineae; family, Rhodospirillaceae; type genus, Rhodospirillum.

Rule 21b

If the name of a family was not made in conformity with Rule 21a but its name has been conserved, then the type genus may be fixed by an Opinion of the Judicial Commission.

Example: The genus Escherichia is the type genus of the family Enterobacteriaceae (Opinion 15).

Type of a Taxon Higher than Order

Rule 22

The type of a taxon higher than order is one of the contained orders, and if there is only one order this becomes the type. If there are two or more orders the type shall be designated by the author at the time of the proposal of the name.

Example: The order Mycoplasmatales of the class Mollicutes.

If not designated, the type of a taxon higher than order may be later designated by an Opinion of the Judicial Commission.

Example: None of the Opinions so far issued (1–63) has dealt with this subject.

Section 5. Priority and Publication of Names

A. Priority of Names

Rule 23a

Each taxon above species, up to and including order, with a given circumscription, position, and rank can bear only one correct name, that is, the earliest that is in accordance with the Rules of this Code.

The name of a species is a binary combination of a generic name and specific epithet (see Rule 12a). In a given position, a species can bear only one correct epithet, that is, the earliest that is in accordance with the Rules of this Code.

Example: The species Haemophilus pertussis bears this name in the genus Haemophilus. If placed in the genus Bordetella, it bears the name Bordetella pertussis.

Note 1. In the case of a species, Rule 23a must be applied independently to the generic name and the specific epithet. The specific epithet remains the same on transfer of a species from one genus to another unless the specific epithet has been previously used in the name of another species or subspecies in the genus to which the species is to be transferred (see Rule 41a).

Note 2. The name of a subspecies is a ternary combination of a generic name, a specific epithet, and a subspecific epithet (see Rule 13c). In a given position a subspecies can bear only one correct subspecific epithet, that is, the earliest that is in accordance with the Rules of this Code. In the case of a subspecies, Rule 23a must be applied independently to the specific and subspecific epithets. The subspecific epithet remains the same on transfer of a subspecies from one species to another, unless the subspecific epithet has been previously used in the name of another species or subspecies in the genus to which the subspecies is to be transferred (see Rule 41a).

Note 3. The date from which all priorities were determined under the previous editions of the Code was 1 May 1753. After 1 January 1980, under Rule 24a all priorities date from 1 January 1980 (see also Rule 24b).

Note 4. The Judicial Commission may make exceptions to Rule 23a by the addition of names to the list of conserved names (nomina conservandd) or to the list of rejected names (nomina rejicienda) (see Appendix 4). The Judicial Commission may correct the Approved Lists (see Rule 24a).

  1. By conserved name (nomen conservandum) is meant a name which must be used instead of all earlier synonyms and homonyms. By rejected name (nomen rejiciendum) is meant a name which must not be used to designate any taxon. Only the Judicial Commission can conserve or reject names (see also Rule 56a, b).
  2. Opinions on the conservation or rejection of names, issued by the Judicial Commission, are published with other Opinions in the IJSB. Opinions are now numbered serially.

Note 5. Names and epithets may be:

legitimate—in accordance with the Rules;

illegitimate—contrary to the Rules;

effectively published—in printed matter made generally available to the scientific community (see Rule 25);

validly published—effectively published and accompanied by a description of the taxon or a reference to a description and certain other requirements (see Rules 2732);

correct—the name which must be adopted for a taxon under the Rules.

Rule 23b

The date of a name or epithet is that of its valid publication. For purposes of priority, however, only legitimate names and epithets are taken into consideration (see Rules 32b and 54).

B. Publication of Names

Rule 24a

Valid publication of names (or epithets) which are in accordance with the Rules of this Code dates from the date of publication of the Code.

Priority of publication dates from 1 January 1980. On that date all names published prior to 1 January 1980 and included in the Approved Lists of Bacterial Names of the ICSB are treated for all nomenclatural purposes as though they had been validly published for the first time on that date, the existing types being retained (but see Rule 24b).

Note 1. Names of bacteria in the various taxonomic categories published up to 31 December 1977 were assessed by the Judicial Commission with the assistance of taxonomic experts. Lists of names were prepared together with the names of the authors who originally proposed the names. These Approved Lists of Bacterial Names were approved by the ICSB and published in the IJSB on 1 January 1980. Names validly published between 1 January 1978 and I January 1980 were included in the Approved Lists of Bacterial Names.

No further names will be added to the Approved Lists. Those names validly published prior to 1 January 1980 but not included in the Approved Lists have no further standing in nomenclature. They were not added to the lists of nomina rejicienda and are thus available for reuse in the naming of new taxa. The reuse of a particular name cannot be recommended if such reuse is likely to result in confusion due to previous or continuing use of the name as a synonym, a strain designation, or for other reasons.

The Approved Lists of Bacterial Names contain for each name a reference to an effectively published description and the type whenever possible. In the case of species or subspecies, if a type strain is available it is listed by its designation and the culture collection (s) from which it may be obtained is indicated. If such a strain is not available, a reference strain or reference material is listed if possible. Neotypes may be proposed in conformity with Rule 18c on such lists. (For citation of names on the Approved Lists, see Rules 33b and 34a.)

Note 2. These Approved Lists may contain more than one name attached to the same type (objective synonyms) since the names on the list represent those names which are considered reasonable in the present state of bacteriological nomenclature and taxonomy and represent the views of many bacteriologists who may hold different taxonomic opinions.

Note 3. Synonyms may be objective synonyms (i.e., more than one name has been associated with the same type) or subjective synonyms (i.e., different names have been associated with different types that in the opinion of the bacteriologist concerned belong to the same taxon). The synonym first published is known as the senior synonym, and later synonyms are known as junior synonyms.

Publication of objective synonyms in the Approved Lists does not affect bacterial nomenclature any more than does the valid publication of objective synonyms in different works in the bacteriological literature at present.

Examples: Objective synonymsNocardia rhodochrous and Mycobacterium rhodochrous. Subjective synonyms—Leudemann (IJSB [1971] 21:240–247) regards Micromonospora fusca Jensen 1932 as a subjective synonym of Micromonospora purpureochromogenes (Waksman and Curtis 1916) Leudemann 1971. These two species have different types.

Rule 24b

(1) If two names compete for priority and if both names date from 1 January 1980 on an Approved List, the priority shall be determined by the date of the original publication of the name before 1 January 1980.

(2) If two names published after 1 January 1980 (and therefore not included on the Approved Lists, 1980, or the Corrigenda, 1984) compete for priority, priority is determined by the date of the publication or announcement of the name in the IJSB. Where the two names appear in the same issue of IJSB, priority is determined by page number; a name appearing on a lower page number of the same issue is deemed to be the earlier. Where two names, previously published in other journals, are validated by announcement on the same Validation List in IJSB, priority is established by the sequence number on the List.

Note 1. In order to implement Rule 24b(2) in the fairest manner, names submitted for inclusion in the Validation List will include a sequence number that reflects the date of receipt of the validation request in the form that is accepted for publication.

Rule 24c

The Judicial Commission may place on the list of rejected names (nomina rejicienda) a name previously published in an Approved List.

Rule 25a Effective publication

Effective publication is effected under this Code by making generally available, by sale or distribution, to the scientific community, printed material for the purpose of providing a permanent record.

Recommendation 25a

When a name of a new taxon is published in a work written in a language unfamiliar to the majority of workers in bacteriology, it is recommended that the author(s) include in the publication a description in a more familiar language.

Rule 25b

No other kind of publication than that cited in Rule 25a is accepted as effective, nor are the following.

  1. Communication of new names at a meeting, in minutes of a meeting, or, after 1950, in abstracts of papers presented at meetings.
  2. Placing of names on specimens in collections or in listings or catalogues of collections.
  3. Distribution of microfilm, microcards, or matter reproduced by-similar methods.
  4. Reports in ephemeral publications, newsletters, newspapers after 1900, or nonscientific periodicals.
  5. Inclusion of a name of a new taxon of bacteria in a published patent application or issued patent.

Rule 26a Date of publication

The date of publication of a scientific work is the date of publication of the printed matter. The date given to the work containing the name or epithet must be regarded as correct in the absence of proof to the contrary.

Rule 26b

The date of acceptance of an article for publication if given in a publication does not indicate the effective date of publication and has no significance in the determination of the priority of publication of names.

Valid and Invalid Publication

Rule 27

A name of a new taxon, or a new combination for an existing taxon, is not validly published unless the following criteria are met.

  1. The name is published in the IJSB.
  2. The publication of the name in the IJSB is accompanied by a description of the taxon or by a reference to a previous effectively published description of the taxon (see Rules 25a and 25b and, for genus and species, Rules 2932).
  3. The type is designated for a new taxon, or cited for a new combination, in the IJSB.

Note. Valid publication of the name of a taxon requires publication in the IJSB of the name of the taxon and reference to an effectively published description whether in the IJSB or in another publication. The date of publication is that of publication in the IJSB. The name may be mentioned in a previously published description, but the name is not validly published until its publication in the IJSB.

If the initial proposal of the new name or new combination is not published in the IJSB, publication (announcement in a Validation List) of the name in the IJSB is the responsibility of the author of the name or combination together with the requirements of Rule 27(2) and (3) above.

In the case of a name of a new taxon (rather than a new combination for a taxon already described), a type must be designated in the publication. It is recommended that the type of a species or subspecies be deposited in a recognized culture collection (see Recommendation 30a) and that the description of the taxon conform to minimal standards (see Recommendation 30b).

Rule 28a

An author validly publishing a new name after 1 January 1980 may revive a name validly published prior to 1 January 1980 (see Rule 24a) but not listed in one of the Approved Lists of Bacterial Names unless the name is a nomen rejiciendum. The name may be used whether or not the new taxon is related in any way to the taxon to which the name was originally applied.

Authority for the name must be claimed by the new author. However, if the author wishes to indicate that the name is a revived name and is used to describe a taxon with the same circumscription, position, and rank as that given by the original author, this may be done by appending the abbreviation "nom.rev." (revived name) to the name (see Rule 33c).

The proposal must contain a brief diagnosis, i.e., a statement or list of those features that led the author to conclude that the proposed taxon is sufficiently different from other recognized taxa to justify its revival. The data included in the statement may be taken from the earlier description and may include newer data, when appropriate. The type must also be designated [see Rule 27(3)].

Note 1. Publication of a new name is not invalidated by previous publication of the name before 1 January 1980 unless the name is included in the Approved Lists of Bacterial Names.

Note 2. Since revived names are treated as new names, they require publication in the IJSB, and the date of valid publication of a revived name is that of the publication in the IJSB (see Rule 27).

Note 3. Search for publication of names and effectively published descriptions prior to 1 January 1980 is no longer required. The Approved Lists of Bacterial Names form the foundation of a new bacterial nomenclature and taxonomy.

Rule 28b

A name or epithet is not validly published in the following circumstances.

  1. It was not accepted at the time of publication by the author who published it.
    Example: Muellerina de Petschenko 1910 (Opinion 10).
    Names or epithets published with a question mark or other indication of taxonomic doubt yet accepted by the author are not validly published.
  2. It was merely proposed in anticipation of the future acceptance of the taxon concerned or the acceptance of a particular circumscription, position, or rank for the taxon which is being named or in anticipation of the future discovery of some hypothetical taxon.
    Examples: (a) Clostrinium Fischer 1895 (Opinion 20); (b) Corynebacterium hemophilum Svendsen et al. (J. Bacteriol. [1947] 53:758). "Its haemophilic properties might be used in coining a name, and the name Corynebacterium hemophilum is suggested in case further investigation should justify its rank as a species."
  3. It was mentioned incidentally. Incidental mention of a new name means mention by an author who does not clearly state or indicate that he is proposing a new name or combination.
    Examples: (a) Pseudobactrinium Trevisan 1888. (b) Raj (IJSB [1970] 20:79) stated: "Also, recently another organism tentatively named as Microcyclus marinus was isolated from the ocean."

Valid Publication of the Name of a Genus or Subgenus, including a Monotypic Genus

Rule 29

For a generic or subgeneric name to be validly published it must comply with the following conditions.

  1. It must be published in conformity with Rules 27 and 28b.
  2. The genus or subgenus named must include one or more described or previously described species.

Instead of a new description of the genus or subgenus, a citation to a previously and effectively published description of the genus as a sub-genus (or subgenus as a genus) may be given.

Example: Not yet found.

In the case of a genus containing a single species, a combined generic and specific description may be given.

Example: Thiobacillus thioparus Beijerinck 1904.

Recommendation 29

A description of a genus or subgenus should mention the points in which the genus or subgenus differs from related genera or subgenera. Where possible, the family to which it belongs should be mentioned.

Valid Publication of the Name of a Species

Rule 30

For the name of a species to be validly published, it must conform with the following conditions.

  1. It must be published in conformity with Rules 27 and 28b.
  2. It must be published as a binary combination consisting of a generic name followed by a single specific epithet (see Rule 12a).

Recommendation 30a

Before publication of the name of a new species, a culture of the type strain (or, if the species is noncultivable, type material, a photograph, or an illustration) should be deposited in at least one of the permanently established culture collections from which it would be readily available. The designation allotted to the strain by the culture collection should be quoted in the published description.

Recommendation 30b

Before publication of the name and description of a new species, the examination and description should conform at least to the minimal standards (if available) required for the relevant taxon of bacteria.

Note. Lists of minimal standards are being prepared for each group of bacteria by experts at the request of the Judicial Commission for consideration by the Judicial Commission and the ICSB for publication in the IJSB (see Appendix 6). Such standards include tests for the establishment of generic identity and for the diagnosis of the species, i.e., an indication of characters which would distinguish the species from others.

Rule 31a

The name of a species or subspecies is not validly published if the description is based upon studies of a mixed culture of more than one species or subspecies. This does not apply to descriptions based chiefly on morphology (e.g., Achromatium oxaliferum Schewiakoff 1893).

Rule 31b

The name of a consortium is not regulated by this Code, and such a name has no standing in nomenclature.

Example: Cylindrogloea bacterifera Perfiliev 1914.

Note. A consortium is an aggregate or association of two or more organisms.

Valid Publication of the Name of a Subspecies

Rule 32a

For the name of a subspecies to be validly published, it must conform with the following conditions.

  1. It must be published in conformity with Rules 27 and 28b.
  2. It must be published as a ternary combination consisting of the generic name followed by a single specific epithet and this in turn by a single subspecific epithet, with the abbreviation "subsp." between the two epithets to indicate the rank (see Rule 13a).
    Example: Bacillus subtilis subsp. subtilis.
  3. The author must clearly indicate that a subspecies is being named.

Recommendation 32a

Recommendations 30a and 30b apply to the name of a subspecies with replacement of the word "species" by the word "subspecies."

Publication of a Specific or Subspecific Epithet

Rule 32b

A specific (or subspecific) epithet is not rendered illegitimate by publication in a species (or subspecies) name in which the generic name is illegitimate (see also Chapter 3, Section 8, and example for Rule 20f).

Section 6. Citation of Authors and Names

Proposal and Subsequent Citation of the Name of a New Taxon

Rule 33a

An author should indicate that a name is being proposed for a new taxon by the addition of the appropriate abbreviation for the category to which the taxon belongs.

Note 1. Appropriate abbreviations are: "ord. nov." for ordo novus, "gen. nov." for genus novum, "sp. nov." for species nova, "comb, nov." for combinatio nova. Similar abbreviations may be formed as required.

Note 2. Although words or abbreviations in Latin are usually printed in italics, such abbreviations as the above are frequently printed in Roman or boldface type when they follow a Latin scientific name in order to differentiate them from the name and draw attention to the abbreviation.

Examples: Order, Actinomycetales ord. nov.; family, Actinomycetaceae fam. nov.; genus, Actinomyces gen. nov.; species, Actinomyces bovis sp. nov.

Rule 33b

The citation of the name of a taxon that has been previously proposed should include both the name of the author(s) who first published the name and the year of publication. If there are more than two authors of the name, the citation includes only the first author followed by "et al." and the year.

Example: Actinomyces bovis Harz 1877.

Note 1. Correct citation of a name enables the date of publication to be verified, the original description to be found, and the use of the name by different authors for different organisms to be distinguished.

Example: Mycobacterium terrae Wayne 1966, not Mycobacterium terrae Tsukamura 1966.

Note 2. Full citation of the publication should include reference to the page number(s) in the main text of the scientific work in which the name was proposed, not to the summary or abstract of that text even if proposal of the name is mentioned in that summary or abstract.

Example: Bacillus subtilis (Ehrenberg 1835) Cohn 1872, 174. The page number "174" is the page in Cohn's publication (Untersuchungen über Bacterien. Beitr. Biol. Pfl. Heft 2 1:127–224) on which the proposal of the new combination occurs.

Note 3.

  1. The citation of a name which is included in an Approved List can include the name of the original author and date of publication followed by the words "Approved Lists 1980" in parentheses.
    Example: Bacillus cereus Frankland and Frankland 1888 (Approved Lists 1980); Bacillus subtilis (Ehrenberg 1835) Cohn 1872 (Approved Lists 1980).
  2. Alternatively, a name which is included in an Approved List may be cited simply by the addition of the words "Approved Lists 1980" in parentheses.
    Examples: Bacillus cereus (Approved Lists 1980); Bacillus subtilis (Approved Lists 1980).
  3. If indication is given that a name is included in an Approved List without specification of that list, the abbreviation "nom. approb." (nomen approbatum) may be appended to the name of the taxon.
    Example: Bacillus subtilis nom. approb.

Rule 33c

If a name or epithet which was published prior to 1 January 1980 but not included in an Approved List is proposed by an author for a different or for the same taxon, the name or epithet must be attributed to the author of the proposal (Rule 28a), and the citation should be made according to Rules 33a, b, and 34a, b.

Note 1. If a name or epithet is revived for the same taxon (in the author's opinion), the author may indicate the fact by addition of the abbreviation "nom. rev." (nomen revictum) after the correct abbreviation (Rule 33a) for the category concerned.

Example: Bacillus palustris sp. nov. nom. rev.

Note 2. If an author wishes to indicate the names of the original authors of a revived name, he may do so by citation of the name of the taxon, followed by the word "ex" and the name of the original author and the year of publication, in parentheses, followed by the abbreviation "nom. rev."

Example: Bacillus palustris (ex Sickles and Shaw 1934) nom. rev. A subsequent author citing this revived name would use the citation Bacillus palustris Brown 1982, or Bacillus palustris (ex Sickles and Shaw 1934) Brown 1982.

Note 3. If an author wishes to indicate that a reused name has been used for a different taxon, indication is made by citation of the name and the author and year of publication followed by the word "non" (or "not") and the name and year of the publication of the author who first used the name.

Rule 33d

If a name is revived under Rule 33c it may be revived in a new combination; that is, the revived species may be transferred to another genus, or the revived subspecies may be transferred to another species, at the time the name is revived. It is not necessary first to revive the name in the original combination.

Example: Bacillus palustris may be revived by Brown as a species of the genus Pseudomonas as Pseudomonas palustris (ex Sickles and Shaw 1934) nom. rev., comb. nov. A subsequent author could cite it as Pseudomonas palustris (ex Sickles and Shaw 1934) Brown 1982.

Proposal and Subsequent Citation of a New Combination

Rule 34a

When an author transfers a species to another genus (Rule 41), or a subspecies to another species, then the author who makes the transfer should indicate the formation of the new combination by the addition to the citation of the abbreviation "comb, nov." (combinatio nova).

This form of citation should be used when the author retains the original specific epithet in the new combination; however, if an author is obliged to substitute a new specific epithet as a result of homonymy, the abbreviation "nom. nov." (nomen novum) should be used [see Rule 41a(l)]. The original name is referred to as the basonym.

Example: Actinomyces exfoliatus Waksman and Curtis 1916; Streptomyces exfoliatus (Waksman and Curtis 1916) comb. nov. (It was correctly cited this way by Waksman and Henrici in Bergey's Manual of Determinative Bacteriology, 6th ed., The Williams & Wilkins Co., Baltimore, 1948.)

Note 1. If an author transfers a species which has been included in the Approved Lists to another genus, the proposal of the new combination should be made by the addition of the abbreviation "comb, nov." (combinatio nova) followed in parentheses by the name under which it appeared in the Approved Lists.

Example: If Bordetella parapertussis appears in the Approved Lists 1980 and is transferred by Smith in 1983 to the genus Moraxella, the citation by Smith may be as follows: Moraxella parapertussis (Eldering and Kendrick 1938) comb. nov. (Bordetella parapertussis Approved Lists 1980). Another author citing this proposal would then use the citation: Moraxella parapertussis (Eldering and Kendrick 1938) Smith 1983 (Bordetella parapertussis Approved Lists 1980).

Rule 34b

The citation of a new combination which has been previously proposed should include the name of the original author in parentheses followed by the name of the author(s) who proposed the new combination and the year of publication of the new combination.

Example: Bacillus polymyxa (Prazmowski) Macé 1889 or Bacillus polymyxa (Prazmowski 1880) Macé 1889.

Note 1. The inclusion of the date of the publication of the original author of the name is to be preferred, although it is sometimes omitted since the date can be expected to be found in the publication of the author(s) who proposed the new combination.

Example: Bacillus polymyxa (Prazmowski 1880) Macé 1889 is to be preferred to Bacillus polymyxa (Prazmowski) Macé 1889.

Note 2. When, however, the author who formed the new combination was obliged to substitute a new specific epithet to avoid homonymy [see Rule 41a(l)], the name of the author of the original specific epithet is omitted.

Example: Streptamyces aurioscleroticus Pridham 1970 is correct, not Streptomyces aurioscleroticus (Thirumalachar el al. 1966) Pridham 1970 [see Example to Rule 41a(l) for explanation].

Rule 34c

When a taxon from subspecies to genus is altered in rank but retains its name or epithet, the original author(s) must be cited in parentheses followed by the name of the author(s) who effected the alteration and the year of publication.

Example: Actinomyces exfoliatus Waksman and Curtis 1916 to Actinomyces chromogenes subsp. exfoliatus (Waksman and Curtis 1916) Krasil'nikov 1941.

Citation of the Name of a Taxon whose Circumscription Has Been Emended

Rule 35

If an alteration of the diagnostic characters or of the circumscription of a taxon modifies the nature of the taxon, the author responsible may be indicated by the addition to the author citation of the abbreviation "emend." (emendavit) followed by the name of the author responsible for the change.

Example: Rhodopseudomonas Czurda and Maresch 1937 emend, van Niel 1944 (see Opinion 49).

Citation of a Name Conserved so as to Exclude the Type

Rule 36

A name conserved so as to exclude the type is not to be ascribed to the original author, but the author whose concept of the name is conserved must be cited as authority.

Example: Aeromonas liquefaciens, the original type species of the genus Aeromonas, has been excluded from Aeromonas (Opinion 48). The generic name Aeromonas is now attributed to Stanier 1943, not to Kluyver and van Niel 1936, and with a new type species, A. hydrophila.

Section 7. Changes in Names of Taxa as a Result of Transference, Union, or Change in Rank

Rule 37a

  1. The name of a taxon must be changed if the nomenclatural type of the taxon is excluded.
  2. Retention of a name in a sense which excludes the type can only be effected by conservation and only by the Judicial Commission (see also Rule 23a). At the time of conservation, the new type is established by the Judicial Commission.

Rule 37b

A change in the name of a taxon is not warranted by an alteration of the diagnostic characters or of the circumscription. A change in its name may be required by one of the following.

  1. An Opinion of the Judicial Commission [see Rule 37a(2) above].
  2. Transfer of the taxon (see Rule 41).
  3. Union with another taxon (Rules 42–44, 47a, and 47b).
  4. Change of its rank (Rules 48, 49, 50a, 50b).

Rule 38

When two or more taxa of the same rank are united, then the name of the taxon under which they are united (and therefore the type of the taxon) is chosen by the rule of priority of publication.

Example: White 1930 united Eberthella Bergey et al. 1923 with Salmonella Lignières 1900 and retained the earlier name, Salmonella

Note. Eberthella was raised by Bergey et al. 1923 to a genus from the subgeneric name, Eberthella Buchanan 1918.

If, however, this choice would lead to confusion in bacteriology, the author should refer this matter to the Judicial Commission. (For taxa above the rank of species, see also Rule 47a.)

Example: Not yet found.

Division of a Genus into Genera or Subgenera, and of a Subgenus into Subgenera

Rule 39a

If a genus is divided into two or more genera or subgenera, the generic name must be retained for one of these. If the name has not been retained (in a previous publication), it must be reestablished under Rule 39b. (See Rule 49 when a subgenus is raised to genus.)

Example: If the genus Bacillus is divided into the two subgenera Bacillus and Aerobacillus, the subgenus which includes the type species Bacillus subtilis must be named Bacillus.

Rule 39b

When a particular species has been designated as the type, the generic name must be retained for the genus which includes that species. When no type was designated a type must be chosen (Editorial Note: should not be needed in the future; see Rule 27).

Rule 39c

The principles of Rules 39a and 39b apply when a subgenus is divided into two or more subgenera, the original subgeneric name being retained for that subgenus which contains the type species.

Division of a Species into Species or Subspecies, and of a Subspecies into Subspecies

Rule 40a

When a species is divided into two or more species or subspecies, the specific epithet of the original species must be retained for one of the taxa into which the species is divided or, if the epithet has not been retained (in a previous publication), it must be reestablished. (See Rule 50a when a subspecies is elevated to a species.)

Rule 40b

The specific epithet must be retained for the species or subspecies which includes the type strain. When no type was designated, one must be chosen (see Note to Rule 39b).

Example: If the species Bacillus subtilis is divided into subspecies, the subspecies containing the type strain must be named Bacillus subtilis subsp. subtilis.

Rule 40c

The principles of Rules 40a and 40b apply when a subspecies is divided into two or more subspecies, the original subspecies name being retained for that subspecies which contains the type strain.

Note. Although the specific and subspecific epithets in the name of a type subspecies are the same, they do not contravene Rule 12b because they are based on the same type.

Transfer of a Species to Another Genus

Rule 41a

When a species is transferred to another genus without any change of rank, the specific epithet must be retained, or if it has not been retained (in a previous publication), it must be reestablished, unless:

  1. The resulting binary combination would be a junior homonym.
    Example: Pridham (1970) proposed Streptomyces aurioscleroticus for Chainia aurea Thirumalachar et al. 1966 on transfer to Streptomyces because in that genus the name Streptomyces aureus already existed.
  2. There is available an earlier validly published and legitimate specific or subspecific epithet.
    Example: Not yet found.

Rule 41b

When the name of a genus is changed, the specific epithets of the species included under the original generic name must be retained for the same species if they are transferred to the new genus.

Union of Taxa of Equal Rank

Rule 42

In the case of subspecies, species, subgenera, and genera, if two or more of those taxa of the same rank are united, the oldest legitimate name or epithet is retained.

If the names or epithets are of the same date, the author who first unites the taxa has the right to choose one of them, and his choice must be followed.

Recommendation 42

Authors who have to choose between two generic names of the same date should note the following:

  1. Prefer the one which is better known.
  2. Prefer the one which was first accompanied by the description of a species.
  3. If both are accompanied by descriptions of species, prefer the one which includes the larger number of species.
  4. In cases of equality from these points of view, prefer the more appropriate name.

Union of Genera as Subgenera

Rule 43

When several genera are united as subgenera of one genus, the sub-genus which includes the type species of the genus under which union takes place must bear the same name as that genus.

Example: The subgenus name Lactobacillus Beijerinck 1901 must be used instead of Thermobacterium for the subgenus that contains the type species Lactobacillus delbrueckii (see Bergey's Manual, 1957, p. 543, and Opinion 38).

Union of Species of Two or More Genera as a Single Genus

Rule 44

If two or more species of different genera are brought together to form a genus, and if these species include the type species of one or more genera, the name of the genus is that associated with the type species having the earliest legitimate generic name.

If no type species is placed in the genus, a new generic name must be proposed and a type species selected.

Example: Brevibacterium Breed 1953. None of the included species was a type species of the genera from which the species were transferred, so a new name, Brevibacterium, was proposed, with Brevibacterium linens as the type species.

Union of Species as Subspecies

Rule 45

When several species are united as subspecies under one species, the subspecies which includes the type strain of the species under whose name they are united must be designated by the same epithet as the species.

Example: Streptomyces griseus subsp. griseus (see Int. Bull. Bacteriol. Nomencl. Taxon. [1965] 15:214 and 224).

Rule 46

The valid publication of a subspecific name which excludes the type of the species automatically creates another subspecies which includes the type and whose name bears the same specific and subspecific epithets as the name of the type.

Example: Publication of Bacillus subtilis subsp. viscosus Chester 1904 automatically created a new subspecies, Bacillus subtilis subsp. subtilis.

The author of the species name is to be cited as the author of such an automatically created subspecific name.

Example: Bacillus subtilis subsp. subtilis (Ehrenberg 1835) Cohn 1872.

Union of Taxa above Species under a Higher Taxon

Rule 47a

When two or more taxa of the same rank from subtribe to family inclusive are united under a taxon of higher rank, the higher-ranking taxon should derive its name from the name of the earliest legitimate genus that is a type genus of one of the lower-ranking taxa.

If, however, the use of this generic name would lead to confusion in bacteriology, then the author may choose as type a genus which, in his opinion, leads to the least confusion and, if in doubt, should refer the matter to the Judicial Commission.

Note. The type of a taxon above the rank of genus is one of the contained genera (Rule 15). The name of the type subgenus is the same as that of the type genus; therefore, only the names of genera need to be considered.

Example: Buchanan in Breed et al. (1957) followed the law of priority in combining the families Beggiatoaceae Migula 1894 and Vitreoscillaceae Pringsheim 1949 into the new order Beggiatoales, whose type is Beggiatoa Trevisan 1842, which has priority over Vitreoscilla Pringsheim 1949. In contrast, Breed et al. (1957) chose Pseudomonas Migula 1894 over Spirillum Ehrenberg 1832 and Nitrobacter Winogradsky 1892 to form the name of a new suborder, Pseudomonadineae Breed et al 1957.

Rule 47b

If no type genera were placed in the taxon, a new name based on the selected type must be proposed for the taxon.

Example: Peptococcaceae Rogosa 1971 (see IJSB [1971] 21:235).

Change in Rank

Rule 48

When the rank of a taxon between subgenus and order is changed, the stem of the name must be retained and only the suffix altered unless the resulting name must be rejected under the Rules (see Rule 9).

Example: Elevation of the tribe Pseudomonadeae to the family Pseudomonadaceae.

Rule 49

When a genus is lowered in rank to subgenus, the original name must be retained unless it is rejected under the Rules. This also applies when a subgenus is elevated to a genus.

Example: If the genus Aerobacillus is lowered in rank to subgenus, the name of the subgenus is Aerobacillus.

Rule 50a

When a subspecies is elevated in rank to a species, the subspecific epithet in the name of the subspecies must be used as the specific epithet of the name of the species unless the resulting combination is illegitimate.

Example: Prapionibacterium jensenii subsp. raffinosaceum van Niel 1928 becomes Profrionibacterium rafjinosaceum (van Niel) Werkman and Kendall 1931.

Rule 50b

When a species is lowered in rank to a subspecies, the specific epithet in the name of the species must be used as the subspecific epithet of the name of the subspecies unless the resulting combination is illegitimate.

Example: Bacillus aterrimus Lehmann and Neumann 1896 becomes Bacillus subtilis subsp. aterrimus (Lehmann and Neumann 1896) Smith et al 1946.

Section 8. Illegitimate Names and Epithets: Replacement, Rejection, and Conservation of Names and Epithets

Illegitimate Names

Rule 5la

A name contrary to a Rule is illegitimate and may not be used. However, a name of a taxon which is illegitimate when the taxon is in one taxonomic position is not necessarily illegitimate when the taxon is in another taxonomic position.

Example: If the genus Diplococcus Weichselbaum 1886 is combined with the genus Streptococcus Rosenbach 1884, Diplococcus is illegitimate as the name of the combined genus because it is not the earlier name. If the genus Diplococcus Weichselbaum is accepted as separate and distinct, then the name Diplococcus is legitimate.

Rule 51b

Among the reasons for which a name may be illegitimate are the following.

  1. If the taxon to which the name was applied, as circumscribed by the author, included the nomenclatural type of a name which the author ought to have adopted under one or more of the Rules.
    Example: If an author circumscribes a genus to include Bacillus subtilis, the type species of the genus Bacillus, then the circumscribed genus must be named Bacillus.
  2. If the author did not adopt for a binary or ternary combination the earliest legitimate generic name, specific epithet, or subspecific epithet available for the taxon with its particular circumscription, position, and rank.
    Example: The name Bacillus whitmori Bergey et al. 1930 was illegitimate as Whitmore had named the organism Bacillus pseudomallei in 1913.
  3. If its specific epithet must be rejected under Rules 52 or 53.
  4. If it is a junior homonym of a name of a taxon of bacteria, fungi, algae, protozoa, or viruses.
    Example: Phytomonas Donovan 1909, a genus of flagellates, antedates Phytomonas Bergey et al 1923, a genus of bacteria (Opinion 14).

Names of bacteria validly published under this revision of the Code are not to be rejected as homonyms of names of bacteria published before 1980 and omitted from the Approved Lists.

Illegitimate Epithets

Rule 52

The following are not to be regarded as specific or subspecific epithets.

  1. A word or phrase which is not intended as a specific epithet.
    Example: Bacillus nova species Matzuschita.
  2. A word which is merely an ordinal adjective used for enumeration.
    Example: primus, secundus.
  3. A number or letter
    Example: α in Bacillus α von Freudenreich.

Rule 53

An epithet is illegitimate if it duplicates a specific or subspecific epithet previously validly published for a species or subspecies of the same genus but which is a different bacterium whose name is based upon another type.

Example: Corynebacterium helvolum (Zimmermann 1890) Kisskalt and Berend 1918 is based on the type of Bacillus helvolus Zimmermann 1890; the specific epithet helvolum cannot be used for Corynebacterium helvolum Jensen 1934, which is a different bacterium whose name is based upon another type.

Replacement of Names

Rule 54

A name or epithet illegitimate according to Rules 51b, 53, or 56a is replaced by the oldest legitimate name or epithet in a binary or ternary combination which in the new position will be in accordance with the Rules.

If no legitimate name or epithet exists, one must be chosen. Since a specific epithet is not rendered illegitimate by publication in a species name in which the generic name is illegitimate (Rule 32b), an author may use such an epithet if he wishes, provided that there is no obstacle to its employment in the new position or sense; the resultant combination is treated as a new name and is to be ascribed to the author of the combination. The epithet is, however, ascribed to the original author.

Example: Pfeifferella pseudomattei (Whitmore 1913) Ford 1928 is an illegitimate combination since Pfeifferella is a homonym of a protozoan generic name (Opinion 14). The epithet pseudomallei can be used for this organism in another genus, Pseudomonas pseudomallei (Whitmore 1913) Haynes 1957.

Rule 55

A legitimate name or epithet may not be replaced merely because of the following.

  1. It is inappropriate.
    Example: Bacteroides melaninogenicum (does not produce melanin; see J. Gen. Microbiol. 1:109–120 [1947]).
  2. It is disagreeable.
    Example: Miyagawanella lymphogranulomatis.
  3. Another name is preferable.
    Example: Not yet found.
  4. Another name is better known.
    Example: Corynebacterium pseudodiphtheriticum cannot be rejected because the synonym Corynebacterium hofmannii is better known.
  5. It no longer describes the organism.
    Example: Haemophilus influenzae (does not cause influenza).
  6. It has been cited incorrectly; an incorrect citation can be rectified by a later author.
    Example: Proteus morganii Yale 1939 (see Lessel, E. E, IJSB 21:55–57 [1971]).

Rejection of Names

Rule 56a

Only the Judicial Commission can place names on the list of rejected names (nomina rejicienda) (see Rule 23a, Note 4, and Appendix 4). A name may be placed on this list for various reasons, including the following.

  1. An ambiguous name (nomen ambiguum), i.e., a name which has been used with different meanings and thus has become a source of error.
    Example: Aerobacter Beijerinck 1900 (Opinion 46).
  2. A doubtful name (nomen dubium), i.e., a name whose application is uncertain.
    Example: Leuconostoc citrovorum (Opinion 45).
  3. A name causing confusion (nomen confusum), i.e., a name based upon a mixed culture.
    Example: Malleomyces Hallier 1870.
  4. A perplexing name (nomen perplexum), a name whose application is known but which causes uncertainty in bacteriology (see Rule 57c).
    Example: Bacillus limnophilus Bredemann and Stürck in Stürck 1935 (Greek-Greek, marsh loving) and Bacillus limophilus Migula 1900 (Latin-Greek, mud loving); see Index Bergeyana, p. 196.
  5. A perilous name (nomen periculosum), i.e., a name whose application is likely to lead to accidents endangering health or life or both or of serious economic consequences.
    Example: Yersinia pseudotuberculosis subsp. pestis (Opinion 60) is to be rejected as a nomen periculosum.

Note 1. This application is restricted to a proposed change in the specific epithet of a nomenspecies which is widely recognized as contagious, virulent, or highly toxigenic, for example, to that of a subspecies of a species having a different host range or a degree of contagiousness or virulence. If the Judicial Commission recognizes a high order of risk to health, or of serious economic consequences, an Opinion may be issued that the taxon be maintained as a separate nomenspecies, without prejudice to the recognition or acceptance of its genetic relatedness to another taxon.

Conservation of Names

Rule 56b

A conserved name (nomen conservandum) is a name which must be used instead of all earlier synonyms and homonyms.

Note 1. A conserved name (nomen conservandum) is conserved against all other names for the taxon, whether these are cited in the corresponding list of rejected names or not, so long as the taxon concerned is not united with another taxon bearing a legitimate name. In the event of union or reunion with another taxon, the earlier of the two competing names is adopted in accordance with Rules 23a, b.

Note 2. Only the Judicial Commission can place names on the list of conserved names (normina conservanda) (see also Rule 23a, Note 4, and Appendix 4).

Section 9. Orthography

Rule 57a

Any name or epithet should be written in conformity with the spelling of the word from which it is derived and in strict accordance with the rules of Latin and latinization. Exceptions are provided for typographic and orthographic errors in Rule 61 and orthographic variants in Rules 62a and 62b.

Rule 57b

In this Code, orthographic variant means a name (or epithet) which differs from another name only in transliteration into Latin of the same word from a language other than Latin or in its grammatical correctness.

Example: Haemophilus, Hemophilus.

Rule 57c

When two or more generic names or two or more epithets in the same genus are so similar (although the words are from different sources) as to cause uncertainty, they may be treated as perplexing names (nomina perplexa) and the matter referred to the Judicial Commission [see Rule 56a(4)].

Example: Bacillus limnophilus and Bacillus limophilus [see Rule 56a(4)].

Note 1. Orthographic variants may be corrected by any author.

Note 2. Perplexing names may be placed on the list of rejected names only by the Judicial Commission, because decisions on the status of names derived from different sources differing in one or more letters affect many well-known names in bacteriology.

Examples: Salmonella gamaba and Salmonella gambaga.

Rule 58

When there is doubt about different spellings of the same name or epithet, or where two spellings are sufficiently alike to be confused, the question should be referred to the Judicial Commission, which may issue an Opinion as seems fit. If one of the spellings is preferred by the Judicial Commission, this spelling should be used by succeeding authors.

Example: The epithet "megaterium" (over "megatherium") in the species name Bacillus megaterium de Bary 1884 (Opinion 1).

Rule 59

An epithet, even one derived from the name of a person, should not be written with an initial capital letter.

Example: Shigella flexneri (named after Flexner).

Rule 60

Intentional latinizations involving changes in orthography of personal names, particularly those of earlier authors, must be preserved.

Example: Pasteur may be latinized as Pastor, and Streptococcus pastorianus is derived from Pastor.

Typographic and Orthographic Errors

Rule 61

The original spelling of a name or epithet must be retained, except typographic or orthographic errors. Original spelling does not refer to the use of an initial capital letter or to diacritic signs.

Example: The original spelling was Bacillus megaterium, not megatherium (Opinion 1).

An unintentional typographical or orthographic error later corrected by the author is to be accepted in its corrected form without affecting its validity and original date of publication. It can also be corrected by a subsequent author who may or may not mention that the spelling is corrected, but the abbreviation "corrig." (corrigendum) may be appended to the name if an author wishes to draw attention to the correction. Succeeding authors may be unaware that the original usage was incorrect and use the spelling of the original author (s). Other succeeding authors may follow the correction of a previous author or may independently correct the spelling themselves, but in no case is the use of corrig. regarded as obligatory. None of these corrections affects the validity and original date of publication.

Example: Mycobacterium stercusis (sic) Bergey et al 1923. Typographic error later corrected by the authors to Mycobacterium stercoris; this maybe cited as Mycobacterium stercoris corrig.

Note. The liberty of correcting a name or epithet under Rules 61, 62a, and 62b must be used with reserve especially if the change affects the first syllable and above all the first letter of the name or epithet.

Orthographic Variants by Transliteration

Rule 62a

Words differing only in transliteration into Latin from other languages which do not use the Latin alphabet are to be treated as orthographic variants unless they are used as the names of taxa based upon different types, when they are to be treated as homonyms. For an account of possible orthographic variants, see Appendix 9.

Example: Haemophilus and Hemophilus.

Rule 62b

When there are orthographic variants based on the same type, and there is no clear indication that one is correct, then an author has the right of choice.

Personal Names

Rule 63

The genitive and adjectival forms of a personal name are treated as different epithets and not as orthographic variants unless they are so similar as to cause confusion. For the latinization of personal names, see Appendix 9.

Example: The epithets pasteurii (genitive noun) and pasteurianum (adjective) are treated as different epithets.

Diacritic Signs

Rule 64

Diacritic signs are not used in names or epithets in bacteriology.

In names or epithets derived from words with such signs, the signs must be suppressed and the letters transcribed as follows: (1) ä, ö, and ü become ae, oe, and ue; (2) é, è, and ê become e; (3) ø, œ, and å become oe, ae, and aa, respectively.

Gender of Names

Rule 65

The gender of generic names is governed by the following.

  1. A Latin or Greek word adopted as a generic name retains the classical gender of its language of origin. Authors are recommended to give the gender of any proposed generic name.
    Example: Sarcina (Latin feminine noun, a package).
    In cases where the classical gender varies, the author has the right of choice between the alternatives (but see Opinion 3 for the masculine gender of -bacter).
    Example: Not yet found.
    Doubtful cases should be referred to the Judicial Commission.
    Example: Not yet found.
  2. Generic or subgeneric names which are modern compounds from two or more Latin or Greek words take the gender of the last component of the compound word.
    Example: Lactobacillus (masculine) milk rodlet from Latin: lac, lactis (neuter), milk; and bacillus (masculine), little staff.
    If the ending is altered, the gender is that of the new ending in the language of origin.
    Example: Not yet found.
  3. Arbitrarily formed generic names or vernacular names used as generic names take the gender assigned to them by their authors. When the original author failed to indicate the gender, a subsequent author has the right of choice.
    Example: Ricolesia Rake 1957, who assigned the feminine gender.
Copyright © 1992, International Union of Microbiological Societies.
Bookshelf ID: NBK8808
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