Iron- and sulfur- cycling bacteria in cold marine sediments from Potter Cove, Antarctica

WILLIS PORATTI GRACIANA; WUNDER LEA C.; AROMOKEYE DAVID A.; RICHTER-HEITMANN TIM; HOLZ CHARLOTTE; VÁZQUEZ SUSANA; FRIEDRICH MICHAEL; MAC CORMACK WALTER.P

Quilmes, Buenos Aires

Simposio; ISME Lat 2023 - 3er Simposio Latinoamericano de Ecología Microbiana; 2023

ISME; Universidad Nacional de Quilmes

One of the most visible signs of climate change is the melting of the glacial ice caps and the increase in meltwater fluxes, currently observed at the northern tip of the Western Antarctic Peninsula (WAP). In Potter Cove (Isla 25 de Mayo, Antarctica), the increase of melt water fluxes into the cove, especially during summer seasons, prompt the accumulation of fine-grained material with high content of metal oxides and pyrite. In organic-rich sediments, oxygen is quickly depleted by microbial respiration at the sediment surface, and sulfate reduction become the main process of anaerobic organic matter degradation, where it often co-occurs with iron reduction. However, little is known about iron and sulfate reducers and their ecology at Potter Cove and other polar regions due to the few anaerobic psychrophiles isolated. Therefore, our objective was to enrich and isolate from Potter Cove sediments potentially novel cold adapted microorganisms involved in iron- and sulfur-cycles . Enrichment cultures were set up with those sediments under anaerobic conditions in Widdel medium and incubated at 2°C. Acetate was used as the electron donor and sulfate, lepidocrocite or magnetite as the electron acceptors. From the fourth-generation cultures, total iron (II) and sulfide were measured over time. After 30 days, DNA was extracted and partial 16S rRNA genes from bacteria and archaea were sequenced by Illumina (2 x 250 bp). Microbial iron reduction was detected in cultures amended with acetate and both lepidocrocite and magnetite. On the enrichment amended with sulfate, the results indicated that sulfate reduction might not be occurring or that sulfide was produced but reoxidized again. The abundances of the 16S rRNA genes amplicon sequence variants (ASVs) from those enrichment cultures showed varying dominances of Arcobacteraceae, Desulfuromonadaceae, Sulfurspirillum spp. and Sulfurimonas spp., depending on the sediment source and electron acceptor (lepidocrocite, magnetite or sulfate) used. Particularly, the phylogenetic classification of the ASVs sometimes reached only the family level, suggesting the presence of potentially new species. From the culture amended with sulfate, sulfate reducers were not detected. From all the enrichments, several isolates were obtained, belonging to different genera: Sulfurspirillum, Poseidonibacter (former Arcobacter), Shewanella, Labilibaculum, Desulfuromusa and Desulfuromonas.