In-situ incubation of iron-sulfur mineral reveals a diverse chemolithoautotrophic community and a new biogeochemical role for Thiomicrospira

Summary Sulfide mineralprecipitation occurs at mid-ocean ridge(MOR) spreading centers, both in the form of plume particles and seafloor massive sulfide structures. A common constituent of MOR is the iron-bearing sulfide mineral pyrrhotite, which was chosen as a substrate for in-situ incubation studies in shallow waters of Catalina Island, CA to investigate the colonization of iron-oxidizing bacteria. Microbial community datasets were obtained from in-situ incubated pyrrhotite, allowing for direct comparison to microbial communities of iron-sulfidesfrom active and inactive chimneysin deep-sea environments. Unclassified Gammaproteobacteriaand Alphaproteobacteria(Magnetovibrio) largely dominated the bacterial community on pyrrhotitesamples incubated in the water column while samples incubated at the surface sediment showed more even dominance by Deltaproteobacteria(Desulfobulbus), Gammaproteobacteria( Piscirickettsiaceae), Alphaproteobacteria( Rhodobacteraceae), and Bacteroidetes( Flavobacteriia). Cultivations that originated from pyrrhotitesamples resulted in the enrichment of both, sheath-forming and stalk-forming Zetaproteobacteria. Additionally, a putative novel species of Thiomicrospira was isolated and shown to grow autotrophicallywith iron, indicating a new biogeochemical role for this ubiquitous microorganism.