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Diversity and abundance of sulfate‐reducing microorganisms in the sulfate and methane zones of a marine sediment, Black Sea
Author(s) -
Leloup Julie,
Loy Alexander,
Knab Nina J.,
Borowski Christian,
Wagner Michael,
Jørgensen Bo Barker
Publication year - 2007
Publication title -
environmental microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.954
H-Index - 188
eISSN - 1462-2920
pISSN - 1462-2912
DOI - 10.1111/j.1462-2920.2006.01122.x
Subject(s) - sulfate , methanogenesis , anaerobic oxidation of methane , environmental chemistry , library , microorganism , methane , sulfate reducing bacteria , anoxic waters , sulfur cycle , biology , water column , ecology , bacteria , chemistry , 16s ribosomal rna , paleontology , organic chemistry
Summary The Black Sea, with its highly sulfidic water column, is the largest anoxic basin in the world. Within its sediments, the mineralization of organic matter occurs essentially through sulfate reduction and methanogenesis. In this study, the sulfate‐reducing community was investigated in order to understand how these microorganisms are distributed relative to the chemical zonation: in the upper sulfate zone, at the sulfate–methane transition zone, and deeply within the methane zone. Total bacteria were quantified by real‐time PCR of 16S rRNA genes whereas sulfate‐reducing microorganisms (SRM) were quantified by targeting their metabolic key gene, the dissimilatory (bi)sulfite reductase ( dsrA ). Sulfate‐reducing microorganisms were predominant in the sulfate zone but occurred also in the methane zone, relative proportion was maximal around the sulfate–methane transition, c . 30%, and equally high in the sulfate and methane zones, 5–10%. The dsrAB clone library from the sulfate–methane transition zone, showed mostly sequences affiliated with the Desulfobacteraceae . While, the dsrAB clone libraries from the upper, sulfate‐rich zone and the deep, sulfate‐poor zone were dominated by similar, novel deeply branching sequences which might represent Gram‐positive spore‐forming sulfate‐ and/or sulfite‐reducing microorganisms. We thus hypothesize that terminal carbon mineralization in surface sediments of the Black Sea is largely due to the sulfate reduction activity of previously hidden SRM. Although these novel SRM were also abundant in sulfate‐poor, methanogenic areas of the Black Sea sediment, their activities and possibly very versatile metabolic capabilities remain subject of further study.