Phylogenetic analysis of dissimilatory Fe(III)-reducing bacteria

Abstract

Evolutionary relationships among strictly anaerobic dissimilatory Fe(III)-reducing bacteria obtained from a diversity of sedimentary environments were examined by phylogenetic analysis of 16S rRNA gene sequences. Members of the genera Geobacter, Desulfuromonas, Pelobacter, and Desulfuromusa formed a monophyletic group within the delta subdivision of the class Proteobacteria. On the basis of their common ancestry and the shared ability to reduce Fe(III) and/or S 0 , we propose that this group be considered a single family, Geobacteraceae. Bootstrap analysis, characteristic nucleotides, and higher-order secondary structures support the division of Geobacteraceae into two subgroups, designated the Geobacter and Desulfuromonas clusters. The genus Desulfuromusa and Pelobacter acidigallici make up a distinct branch within the Desulfuromonas cluster. Several members of the family Geobacteraceae, none of which reduce sulfate, were found to contain the target sequences of probes that have been previously used to define the distribution of sulfate-reducing bacteria and sulfatereducing bacterium-like microorganisms. The recent isolations of Fe(III)-reducing microorganisms distributed throughout the domain Bacteria suggest that development of 16S rRNA probes that would specifically target all Fe(III) reducers may not be feasible. However, all of the evidence suggests that if a 16S rRNA sequence falls within the family Geobacteraceae, then the organism has the capacity for Fe(III) reduction. The suggestion, based on geological evidence, that Fe(III) reduction was the first globally significant process for oxidizing organic matter back to carbon dioxide is consistent with the finding that acetate-oxidizing Fe(III) reducers are phylogenetically diverse.

Sulfurospirillum arcachonense sp. nov., a New Microaerophilic Sulfur-Reducing Bacterium

“…The 16s rRNA sequences of both microorganisms share an overall similarity of 99% and thus can be considered as phylogenetic twins. In recent publications, the dissimilatory Fe(II1)-, selenate-, and arsenate-reducing strain SES-3 has tentatively been named "Geospirillum barnesii" (23,41). However, the genus name "Geospirillum" is in conflict with the validly described taxon Sulfurospirillum (16,37), which should be considered in the further taxonomic description of strain SES-3.…”

“…With the exception of those members of the genus Pelobacter that have been tested for the ability to grow with sulfur as an electron acceptor (24), all members of group 1 completely oxidize their substrates (complete oxidizers), releasing exclusively CO, and H2S. A second group (group 2) includes members of the genera Wolinella (49), Campylobacter (37), Shewanella (27) (originally described as a member of the genus Alteromonas [30]), and Sulfurospirillum (37, 48), as well as isolates which have not been characterized taxonomically, such as free-living "Campylobacter-like organisms," (DSM 806 = CCUG 13942) (19) and the dissimilatory selenate-and arsenate-reducing strain SES-3 (21,31) that has been tentatively named "Geospirillum bamesii" (23,41). These species have in common the abilities to grow at low oxygen concentrations and to oxidize organic substrates incompletely with elemental sulfur as the electron acceptor (incomplete oxidizers).…”

Reduction of ferric iron by acidophilic heterotrophic bacteria: evidence for constitutive and inducible enzyme systems in Acidiphilium spp.

“…Significant numbers of prokaryotic micro-organisms have been shown to be able to use ferric iron as an electron acceptor for anaerobic respiration (Lovley 1995;Lonergan et al 1996;Johnson 1998). This ability appears to be particularly widespread amongst acidophilic bacteria, presumably because (i) many extremely acidic (pH < 3) environments contain elevated concentrations of iron (particularly those associated with metal mining; Banks et al 1997) and (ii) the solubility of ferric iron is far greater at lower pH (especially at pH < 2AE3) than in circum-neutral environments.…”

Desulfuromonas svalbardensis sp. nov. and Desulfuromusa ferrireducens sp. nov., psychrophilic, Fe(III)-reducing bacteria isolated from Arctic sediments, Svalbard

“…The genus Desulfuromusa is represented by three species, Desulfuromusa bakii, Desulfuromusa kysingii and Desulfuromusa succinoxidans, isolated by elemental sulfur reduction (Liesack & Finster, 1994). Together with the genera Pelobacter, Malonomonas and Geobacter, Desulfuromusa and Desulfuromonas form the family Geobacteraceae Holmes et al 2004, a monophyletic group within the Deltaproteobacteria (Holmes et al, 2004a;Lonergan et al, 1996). An important characteristic of species within this group is the ability to reduce Fe(III) and/ or elemental sulfur.…”