Microbes mediating the sulfur cycle in the Atlantic Ocean and their link to chemolithoautotrophy

Daniele De Corte, Simone Muck, Johanna Tiroch, Catalina Mena, Gerhard J Herndl, Eva Sintes

Only about 10%-30% of the organic matter produced in the epipelagic layers reaches the dark ocean. Under these limiting conditions, reduced inorganic substrates might be used as energy source to fuel prokaryotic chemoautotrophic and/or mixotrophic activity. The aprA gene encodes the alpha subunit of the adenosine-5'-phosphosulfate (APS) reductase, present in sulfate-reducing (SRP) and sulfur-oxidizing prokaryotes (SOP). The sulfur-oxidizing pathway can be coupled to inorganic carbon fixation via the Calvin-Benson-Basham (CBB) cycle. The abundances of aprA and cbbM, encoding RuBisCO form II (the key CO2 fixing enzyme), were determined over the entire water column along a latitudinal transect in the Atlantic from 64°N to 50°S covering six oceanic provinces. The abundance of aprA and cbbM genes significantly increased with depth reaching highest abundances in meso- and upper bathypelagic layers. The contribution of cells containing these genes also increased from mesotrophic towards oligotrophic provinces, suggesting that under nutrient limiting conditions alternative energy sources are advantageous. However, the aprA/cbbM ratios indicated that only a fraction of the SOP is associated with inorganic carbon fixation. The aprA harboring prokaryotic community was dominated by Pelagibacterales in surface and mesopelagic waters, while Candidatus Thioglobus, Chromatiales and the Deltaproteobacterium_SCGC dominated the bathypelagic realm. Noticeably, the contribution of the SRP to the prokaryotic community harboring aprA gene was low, suggesting a major utilization of inorganic sulfur compounds either as energy source (occasionally coupled with inorganic carbon fixation) or in biosynthesis pathways. This article is protected by copyright. All rights reserved.

Functional and Evolutionary Ecology, Department of Physiological Chemistry
External organisation(s)
Carl von Ossietzky Universität Oldenburg, Instituto Español de Oceanografía, Utrecht University, Universität Wien
Environmental Microbiology
Publication date
Peer reviewed
Austrian Fields of Science 2012
106021 Marine biology
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