Evidence for the presence of thermophilic Fe(III)-reducing microorganisms in deep-sea hydrothermal vents at 13 degrees N (East Pacific Rise)

Microorganisms capable of dissimilatory Fe(III) reduction in the temperatur e range of 52-90 degreesC were enriched From outer and inner parts of chimn ey-like structures, tubes of the polychaetous annelid Alvinella sp., and hy drothermal fluids collected at 13 degreesN hydrothermal vent sites on the E ast Pacific Rise at a depth of 2650 m. Numbers of culturable Fe(III)-reduci ng thermophiles estimated by the serial dilution technique varied From 10 t o 10(7) cells per cm(3) of sample. Phylogenetic analysis of bacterial and a rchaeal PCR-amplified 16S rDNA genes obtained from Fe(III)-reducing enrichm ents and separated by denaturing gradient gel electrophoresis revealed sequ ences related to Deferibacter, Thermotogales (Bacteria) and Thermococcus (A rchaea) for which the capacity for Fe(III) reduction had been reported. Thi s was confirmed by isolating a hyperthermophilic iron reducer that belongs to the genus Thermococcus. Other bacterial thermophiles found in the enrich ments were related to so far uncultured members of the Clostridiaceae, and e-subdivision of the Proteobacteria. (C) 2001 Published by Elsevier science B.V. on behalf of the Federation of European Microbiological Societies.