Molecular characterization and diversity of thermophilic iron-reducing enrichment cultures from deep subsurface environments

Aims: The objectives of this work were to explore the diversity in Fe(III)- reducing enrichment cultures from the deep subsurface and to identify; stra ins involved in metal reduction. Methods and Results: Analyses of 16S ribosomal RNA (rRNA) of enrichments, s upplemented with hydrogen, acetate or pyruvate as an electron donor, identi fied three dominant operational taxonomic units (OTUs). All cultures exhibi ted considerable diversity (36-24 OTUs), even after being transferred at le ast nine times. Two OTUs were present in all three cultures, constituting a bout 65% of the total clones examined. Conclusions: Dominant OTUs appeared to be most closely related to Thermoana erobacter ethanolicus or T. kivui. One OTU, which is potentially responsibl e for autotrophic Fe(III) reduction, was only about 95% similar to T. ethan olicus and may represent a new species. Significance and Impact of the Study: An unexpectedly high diversity was fo und in these enrichments and this diversity may be a feature that can be ex ploited.