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Applied and Environmental Microbiology, December 1998, p. 4846-4856, Vol. 64, No. 12
Max-Planck-Institut für Marine
Mikrobiologie, 28359 Bremen, Germany
Received 8 June 1998/Accepted 16 September 1998
Anaerobic, nitrate-dependent microbial oxidation of ferrous iron
was recently recognized as a new type of metabolism. In order to study
the occurrence of three novel groups of ferrous iron-oxidizing, nitrate-reducing bacteria (represented by strains BrG1, BrG2, and
BrG3), 16S rRNA-targeted oligonucleotide probes were developed. In
pure-culture experiments, these probes were shown to be suitable for
fluorescent in situ hybridization, as well as for hybridization analysis of denaturing gradient gel electrophoresis (DGGE) patterns. However, neither enumeration by in situ hybridization nor detection by
the DGGE-hybridization approach was feasible with sediment samples.
Therefore, the DGGE-hybridization approach was combined with
microbiological methods. Freshwater sediment samples from different
European locations were used for enrichment cultures and
most-probable-number (MPN) determinations. Bacteria with the ability to
oxidize ferrous iron under nitrate-reducing conditions were detected in
all of the sediment samples investigated. At least one of the
previously described types of bacteria was detected in each enrichment
culture. MPN studies showed that sediments contained from 1 × 105 to 5 × 108 ferrous iron-oxidizing,
nitrate-reducing bacteria per g (dry weight) of sediment, which
accounted for at most 0.8% of the nitrate-reducing bacteria growing
with acetate. Type BrG1, BrG2, and BrG3 bacteria accounted for an even
smaller fraction (0.2% or less) of the ferrous iron-oxidizing,
nitrate-reducing community. The DGGE patterns of MPN cultures suggested
that more organisms than those isolated thus far are able to oxidize
ferrous iron with nitrate. A comparison showed that among the
anoxygenic phototrophic bacteria, organisms that have the ability to
oxidize ferrous iron also account for only a minor fraction of the population.
0099-2240/98/$04.00+0
Copyright © 1998, American Society for Microbiology. All rights reserved.
Enumeration and Detection of Anaerobic Ferrous
Iron-Oxidizing, Nitrate-Reducing Bacteria from Diverse European
Sediments
*
Corresponding author. Mailing address:
Max-Planck-Institut für Marine Mikrobiologie, Celsiusstr. 1, 28359 Bremen, Germany. Phone: 49-421-2028-736. Fax: 49-421-2028-580.
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