Microbial imprints on sulfide minerals in submarine hydrothermal deposits

Diverse numbers of iron- and sulfur-oxidizing microbes have been found in submarine hydrothermal deposits. They have played a prominent role in weathering of seafloor sulfide deposits. However, evidence for microbe-mineral interactions in sediments is rare. Mineralogic analysis and scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM-EDX) examination of sulfide deposits from the East Pacific Rise demonstrated that (1) sulfide minerals were extensively leached, with characteristic microbial dissolution pits on mineral surfaces; (2) the possible Acidithiobacillus-like bacteria and metabolites were found closely associated with the dissolution pits in situ. The results provide direct evidence for microbial leaching on the solid mineral crystals, most likely by the contact mechanisms, in the seafloor sulfide deposits.