Desulfuromonas carbonis sp. nov., an Fe(III)-, S0- and Mn(IV)-reducing bacterium isolated from an active coalbed methane gas well.

A novel, mesophilic, obligately anaerobic, acetate-oxidizing, dissimilatory iron-, sulfur-, and manganese-reducing bacterium, designated strain ICBM(T), was obtained from an active, coalbed methane gas well in Indiana, USA. Strain ICBM(T) was a Gram-stain-negative, non-spore-forming, rod-shaped, non-motile bacterium that was rich in c-type cytochromes and formed red colonies in solid medium. Strain ICBM(T) conserved energy to support growth from the oxidation of acetate, propionate, pyruvate, malate, fumarate, succinate and dl-lactate, concomitant with dissimilatory iron reduction. Strain ICBM(T) fermented fumarate yielding succinate and acetate. Strain ICBM(T) was able to grow in the temperature range of 10 °C to 37 °C, NaCl concentration range of 0 to 1.2 M, and pH range of 6.5 to 8.0. The physiological characteristics of strain ICBM(T) indicated that it belongs to the Desulfuromonas cluster. The G+C content of its genomic DNA was 61.2 mol%. The predominant cellular fatty acids were C16 : 0 (39.3%), C16 : 1ω7c and/or iso-C15 : 0 2-OH (36.6%). The closest cultured phylogenetic relative of strain ICBM(T) was Desulfuromonas michiganensis BB1(T) with only 95% 16S rRNA gene sequence similarity. This confirmed that strain ICBM(T) is affiliated with the genus Desulfuromonas . On the basis of phenotypic and genotypic differences between strain ICBM(T) and other taxa of the genus Desulfuromonas , strain ICBM(T) represents a novel species for which the name Desulfuromonas carbonis sp. nov. is proposed (type strain ICBM(T) = DSM 29759(T) = JCM 30471(T)). Strain ICBM(T) is the first Fe(III)-, S(0)-, and Mn(IV)-reducing bacterium that was isolated from a coal bed.

Sulfur oxidation to sulfate coupled with electron transfer to electrodes by Desulfuromonas strain TZ1.

Microbial oxidation of elemental sulfur with an electrode serving as the electron acceptor is of interest because this may play an important role in the recovery of electrons from sulfidic wastes and for current production in marine benthic microbial fuel cells. Enrichments initiated with a marine sediment inoculum, with elemental sulfur as the electron donor and a positively poised (+300 mV versus Ag/AgCl) anode as the electron acceptor, yielded an anode biofilm with a diversity of micro-organisms, including Thiobacillus, Sulfurimonas, Pseudomonas, Clostridium and Desulfuromonas species. Further enrichment of the anode biofilm inoculum in medium with elemental sulfur as the electron donor and Fe(III) oxide as the electron acceptor, followed by isolation in solidified sulfur/Fe(III) medium yielded a strain of Desulfuromonas, designated strain TZ1. Strain TZ1 effectively oxidized elemental sulfur to sulfate with an anode serving as the sole electron acceptor, at rates faster than Desulfobulbus propionicus, the only other organism in pure culture previously shown to oxidize S° with current production. The abundance of Desulfuromonas species enriched on the anodes of marine benthic fuel cells has previously been interpreted as acetate oxidation driving current production, but the results presented here suggest that sulfur-driven current production is a likely alternative.

Characterization of microbial community structure and population dynamics of tetrachloroethene-dechlorinating tidal mudflat communities.

Tetrachloroethene (PCE) and trichloroethene (TCE) are common groundwater contaminants that also impact tidal flats, especially near urban and industrial areas. However, very little is known about dechlorinating microbial communities in tidal flats. Titanium pyrosequencing, 16S rRNA gene clone libraries, and dechlorinator-targeted quantitative real-time PCR (qPCR) characterized reductive dechlorinating activities and populations in tidal flat sediments collected from South Korea's central west coast near Kangwha. In microcosms established with surface sediments, PCE dechlorination to TCE began within 10 days and 100% of the initial amount of PCE was converted to TCE after 37 days. cis-1,2-Dichloroethene (cis-DCE) was observed as dechlorination end product in microcosms containing sediments collected from deeper zones (i.e., 35-40 cm below ground surface). Pyrosequencing of bacterial 16S rRNA genes and 16S rRNA gene-targeted qPCR results revealed Desulfuromonas michiganensis-like populations predominanted in both TCE and cis-DCE producing microcosms. Other abundant groups included Desulfuromonas thiophila and Pelobacter acidigallici-like populations in the surface sediment microcosms, and Desulfovibrio dechloracetivorans and Fusibacter paucivorans-like populations in the deeper sediment microcosms. Dehalococcoides spp. populations were not detected in these sediments before and after incubation with PCE. The results suggest that tidal flats harbor novel, salt-tolerant dechlorinating populations and that titanium pyrosequencing provides more detailed insight into community structure dynamics of the dechlorinating microcosms than conventional 16S rRNA gene sequencing or fingerprinting methods.

Comparison of 16S rRNA, nifD, recA, gyrB, rpoB and fusA genes within the family Geobacteraceae fam. nov.

The sequences of five conserved genes, in addition to the 16S rRNA gene, were investigated in 30 members of the Geobacteraceae fam. nov. All members of the Geobacteraceae examined contained nifD, suggesting that they are capable of nitrogen fixation, which may explain their ability to compete effectively in nitrogen-poor subsurface environments undergoing remediation for petroleum or metal contamination. The phylogenies predicted from rpoB, gyrB, fusA, recA and nifD were generally in agreement with the phylogeny predicted from 16S rRNA gene sequences. Furthermore, phylogenetic analysis of concatemers constructed from all five protein-coding genes corresponded closely with the 16S rRNA gene-based phylogeny. This study demonstrated that the Geobacteraceae is a phylogenetically coherent family within the delta-subclass of the Proteobacteria that is composed of three distinct phylogenetic clusters: Geobacter, Desulfuromonas and Desulfuromusa. The sequence data provided here will make it possible to discriminate better between physiologically distinct members of the Geobacteraceae, such as Pelobacter propionicus and Geobacter species, in geobacteraceae-dominated microbial communities and greatly expands the potential to identify geobacteraceae sequences in libraries of environmental genomic DNA.