Pelobacter seleniigenes sp. nov., a selenate-respiring bacterium

Abstract

Strain KM(T) 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 KM(T) was isolated from a sediment enrichment culture of a highly impacted wetland system in New Jersey, USA. Strain KM(T) is able to reduce selenate as well as selenite to elemental selenium. The unique metabolic capabilities of strain KM(T) 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 KM(T) 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 1(T), Pelobacter acidigallici Ma Gal 2(T) 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 KM(T) to ferment organic compounds as well as to couple selenate reduction to acetate utilization. Based on 16S rRNA gene phylogeny and metabolic properties, strain KM(T) represents a novel species for which the name Pelobacter seleniigenes sp. nov. (type strain KM(T)=DSM 18267(T)=ATCC BAA-1388(T)) 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 1(T) should also be included in this group.