Microbial diversity involved in iron and cryptic sulfur cycling in the ferruginous, low-sulfate waters of Lake Pavin

摘要: Both iron- and sulfur- reducing bacteria strongly impact the mineralogy of iron, but their activity has long been thought to be spatially temporally segregated based on higher thermodynamic yields iron over sulfate reduction. However, recent evidence suggests that sulfur cycling can predominate even under ferruginous conditions. In this study, we investigated potential for bacterial metabolisms in iron-rich (1.2 mM dissolved Fe2+), sulfate-poor (< 20 μM) Lake Pavin which is expected host large populations iron-reducing iron-oxidizing microorganisms influencing precipitates its permanently anoxic bottom waters sediments. 16S rRNA gene amplicon libraries from at below oxycline revealed highly diverse sulfur/sulfate-reducing (SRB) sulfur/sulfide-oxidizing represented up 10% 5% total recovered sequences situ, respectively, together was roughly equivalent fraction putative bacteria. enrichment cultures amended with key phases identified situ (ferric phosphate, ferrihydrite) or soluble (Fe2+), SRB were most competitive microorganisms, both presence absence added sulfate. The Sulfurospirillum, are known reduce thiosulfate not sulfate, present all likely supported by Fe(III)-driven sulfide oxidation. These results support hypothesis an active cryptic cycle interacts lake. Analyses mineral showed ferric phosphate dominated transformed vivianite concomitant precipitation sulfides. As colloidal FeS have reported monimolimnion, suggest along influence water column sediments Pavin.