• We are sorry, but NCBI web applications do not support your browser and may not function properly. More information
Logo of pnasPNASInfo for AuthorsSubscriptionsAboutThis Article
Proc Natl Acad Sci U S A. Oct 1981; 78(10): 6324–6328.
PMCID: PMC349031

Structured habitats and the evolution of anticompetitor toxins in bacteria.


We demonstrate that in liquid cultures, defined in this study as a mass habitat, the outcome of competition between Escherichia coli that produce an antibacterial toxin (colicin) and sensitive E. coli is frequency dependent; the colicinogenic bacteria are at an advantage only when fairly common (frequencies in excess of 2 X 10(-2)). However, we also show that in a soft agar matrix, a structured habitat, the colicinogenic bacteria have an advantage even when initially rare (frequencies as low as 10(-6)). These contrasting outcomes are attributed to the colicinogenic bacteria's lower intrinsic growth rate relative to the sensitive bacteria and the different manner in which bacteria and resources are partitioned in the two types of habitats. Bacteria in a liquid culture exist as randomly distributed individuals and the killing of sensitive bacteria by the colicin augments the amount of resource available to the colicinogenic bacteria to an extent identical to that experienced by the surviving sensitive bacteria. On the other hand, the bacteria in a soft agar matrix exist as single-clone colonies. As the colicinogenic colonies release colicin, they kill neighboring sensitive bacteria and form an inhibition zone around themselves. By this action, they increase the concentration of resources around themselves and overcome their growth rate disadvantage. We suggest that structured habitats are more favorable for the evolution of colicinogenic bacteria.

Full text

Full text is available as a scanned copy of the original print version. Get a printable copy (PDF file) of the complete article (1.3M), or click on a page image below to browse page by page. Links to PubMed are also available for Selected References.

Images in this article

Click on the image to see a larger version.

Selected References

These references are in PubMed. This may not be the complete list of references from this article.
  • FREDERICQ P. Colicins. Annu Rev Microbiol. 1957;11:7–22. [PubMed]
  • Nomura M. Colicins and related bacteriocins. Annu Rev Microbiol. 1967;21:257–284. [PubMed]
  • Hardy KG. Colicinogeny and related phenomena. Bacteriol Rev. 1975 Dec;39(4):464–515. [PMC free article] [PubMed]
  • Case TJ, Gilpin ME. Interference competition and niche theory. Proc Natl Acad Sci U S A. 1974 Aug;71(8):3073–3077. [PMC free article] [PubMed]
  • Herschman HR, Helinski DR. Comparative study of the events associated with colicin induction. J Bacteriol. 1967 Sep;94(3):691–699. [PMC free article] [PubMed]
  • Meyers JA, Sanchez D, Elwell LP, Falkow S. Simple agarose gel electrophoretic method for the identification and characterization of plasmid deoxyribonucleic acid. J Bacteriol. 1976 Sep;127(3):1529–1537. [PMC free article] [PubMed]
  • ATWOOD KC, SCHNEIDER LK, RYAN FJ. Selective mechanisms in bacteria. Cold Spring Harb Symp Quant Biol. 1951;16:345–355. [PubMed]
  • Levin BR. Coexistence of two asexual strains on a single resource. Science. 1972 Mar 17;175(4027):1272–1274. [PubMed]
  • Adams J, Kinney T, Thompson S, Rubin L, Helling RB. Frequency-Dependent Selection for Plasmid-Containing Cells of ESCHERICHIA COLI. Genetics. 1979 Apr;91(4):627–637. [PMC free article] [PubMed]
  • Ikari NS, Kenton DM, Young VM. Interaction in the germfree mouse intestine of colicinogenic and colicin-sensitive microorganisms. Proc Soc Exp Biol Med. 1969 Apr;130(4):1280–1284. [PubMed]
  • Costerton JW, Geesey GG, Cheng KJ. How bacteria stick. Sci Am. 1978 Jan;238(1):86–95. [PubMed]
  • Wireman JW, Dworkin M. Developmentally induced autolysis during fruiting body formation by Myxococcus xanthus. J Bacteriol. 1977 Feb;129(2):798–802. [PMC free article] [PubMed]

Articles from Proceedings of the National Academy of Sciences of the United States of America are provided here courtesy of National Academy of Sciences


Related citations in PubMed

See reviews...See all...

Cited by other articles in PMC

See all...


Recent Activity

Your browsing activity is empty.

Activity recording is turned off.

Turn recording back on

See more...