Summary auto-generated
This study describes Pelobacter seleniigenes sp. nov., a novel anaerobic bacterium isolated from New Jersey wetland sediment. Strain KMT exhibits unique metabolic capabilities: it can respire selenate as an electron acceptor using acetate as both carbon source and electron donor, sequentially reducing selenate to selenite and then to insoluble elemental selenium. Additionally, strain KMT can ferment short-chain organic acids (pyruvate, citrate, lactate) and respire other inorganic electron acceptors including nitrate, Fe(III), and anthraquinone disulfonate. Phylogenetic analysis of 16S rRNA gene sequences places strain KMT within the family Geobacteraceae, class Deltaproteobacteria, sharing 96-97% similarity with closely related organisms. The bacterium is rod-shaped, gram-negative, motile, and strictly anaerobic, with a genomic G+C content of 54.1 mol%. Notably, strain KMT combines respiratory capability with fermentative metabolism and broad salt tolerance (0.5-3.5% NaCl), distinguishing it from closely related genera that typically lack either respiratory or fermentative abilities. The authors propose this combined phylogenetic and physiological characterization as justification for naming the organism as a novel species.
Key findings
- Pelobacter seleniigenes sp. nov. (strain KMT) uniquely couples selenate respiration to acetate oxidation, reducing selenate sequentially to elemental selenium
- Strain KMT combines both respiratory metabolism (selenate, nitrate, Fe(III), AQDS reduction) and fermentative metabolism (pyruvate, citrate, lactate fermentation), unlike closely related genera
- Phylogenetic analysis places strain KMT within the Desulfuromusa cluster of family Geobacteraceae, with 96-97% 16S rRNA gene similarity to closest relatives
- Strain KMT tolerates a wide range of NaCl concentrations (0.5-3.5%), contrasting with marine-origin related strains requiring strict salt concentrations
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Abstract
Strain KMT is a novel bacterium with the unique metabolic abilities of being able to respire selenate as the electron acceptor using acetate as the carbon substrate and possessing the ability to grow fermentatively on short-chain organic acids such as lactate, citrate and pyruvate. Strain KMT was isolated from a sediment enrichment culture of a highly impacted wetland system in New Jersey, USA. Strain KMT is able to reduce selenate as well as selenite to elemental selenium. The unique metabolic capabilities of strain KMT include the respiration of nitrate, poorly crystalline Fe(III) and anthraquinone disulfonate. Phylogenetic analysis of the 16S rRNA gene of the novel isolate indicates that strain KMT groups within the family Geobacteraceae in the class Deltaproteobacteria with approximately 96–97 % 16S rRNA gene sequence similarity to the closest known organisms Malonomonas rubra Gra Mal 1T, Pelobacter acidigallici Ma Gal 2T and species of the genus Desulfuromusa. Recognized species of the genera Malonomonas and Pelobacter cannot use any inorganic electron acceptors, while strains of the genus Desulfuromusa do not ferment organic substrates. This contrasts with the ability of strain KMT to ferment organic compounds as well as to couple selenate reduction to acetate utilization. Based on 16S rRNA gene phylogeny and metabolic properties, strain KMT represents a novel species for which the name Pelobacter seleniigenes sp. nov. (type strain KMT=DSM 18267T=ATCC BAA-1388T) is proposed. Based on the phylogenetic grouping of species of the genus Pelobacter within the Desulfuromusa cluster, it is suggested that Malonomonas rubra Gra Mal 1T should also be included in this group.