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Environ Sci Pollut Res Int. 2017 Aug;24(23):19223-19233. doi: 10.1007/s11356-017-9597-x. Epub 2017 Jun 30.

Bacterial periphytic communities related to mercury methylation within aquatic plant roots from a temperate freshwater lake (South-Western France).

Author information

1
Equipe Environnement et Microbiologie, UMR IPREM5254 Université de Pau et des Pays de l'Adour, Bâtiment IBEAS, BP1153, 64013, Pau Cedex, France. sophie.gentes@u-bordeaux.fr.
2
Université de Bordeaux, EPOC, UMR CNRS 5805, 33120, Arcachon, France. sophie.gentes@u-bordeaux.fr.
3
Equipe Environnement et Microbiologie, UMR IPREM5254 Université de Pau et des Pays de l'Adour, Bâtiment IBEAS, BP1153, 64013, Pau Cedex, France.
4
Equipe CIH, IMS UMR 5218, Ecole Nationale Supérieure de Cognitique, 109 Avenue Roul, 33400, Talence, France.

Abstract

Macrophyte floating roots are considered as hotspots for methylmercury (MeHg) production in aquatic ecosystems through microbial activity. Nevertheless, very little is known about periphyton bacterial communities and mercury (Hg) methylators in such ecological niches. The ability to methylate inorganic Hg is broadly distributed among prokaryotes; however, sulfate-reducers have been reported to be the most important MeHg producers in macrophyte floating roots. In the present work, the periphyton bacterial communities colonizing Ludwigia sp. floating roots were investigated through molecular methods. Among the 244 clones investigated, anaerobic microorganisms associated with the sulfur biogeochemical cycle were identified. Notably, members of the sulfur-oxidizing prokaryotes and the anoxygenic, purple non-sulfur bacteria (Rhodobacteraceae, Comamonadaceae, Rhodocyclaceae, Hyphomicrobiaceae) and the sulfate reducers (Desulfobacteraceae, Syntrophobacteraceae, and Desulfobulbaceae) were detected. In addition, 15 sulfate-reducing strains related to the Desulfovibrionaceae family were isolated and their Hg-methylation capacity was tested using a biosensor. The overall results confirmed that Hg methylation is a strain-specific process since the four strains identified as new Hg-methylators were closely related to non-methylating isolates. This study highlights the potential involvement of periphytic bacteria in Hg methylation when favorable environmental conditions are present in such ecological micro-niches.

KEYWORDS:

Bacterial diversity; Biosensor; Mercury methylation; Periphyton; Sulfate reducers

PMID:
28664497
DOI:
10.1007/s11356-017-9597-x
[Indexed for MEDLINE]

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