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