The Genera Desulfitobacterium and Desulfosporosinus: Taxonomy
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The Genera Desulfitobacterium and Desulfosporosinus: Taxonomy STEFAN SPRING AND FRANK ROSENZWEIG
Introduction Members of the genera Desulfitobacterium and Desulfosporosinus represent a clade of strictly anaerobic, rod-shaped, and sporeforming bacteria within the phylum Firmicutes, previously also known as the “low G+C Gram-positive bacteria.” The taxonomic and environmental significance of microorganisms belonging to this group escaped the attention of microbiologists for a long time and was only recently revealed, although the first representative species was already isolated in 1959. This species, however, was wrongly described as Desulfovibrio orientis (Adams and Postgate, 1959). Later the taxonomic affiliation of this bacterium to the Grampositive sulfate reducers was recognized and it was reclassified as Desulfotomaculum orientis (Campbell and Postgate, 1965). Under this name it was included in the Approved Lists of Bacterial Names (Skerman et al., 1980). In the course of a phylogenetic analysis of the genus Desulfotomaculum, the separate taxonomic position of this species was revealed and the novel genus Desulfosporosinus was proposed with Dsp. orientis as type species (Stackebrandt et al., 1997). Some years earlier, Utkin et al. (1994) had already established the genus Desulfitobacterium with the type species Dba. dehalogenans. The special feature of this species was the reductive dechlorination of halogenated hydrocarbons. At that time this metabolic capability was only known in very few strict anaerobic bacteria. Since then, substantial progress was made in the isolation and description of novel strains representing the genus Desulfitobacterium, mainly caused by the growing interest in microorganisms being able to degrade and detoxify halogenated environmental pollutants under anoxic conditions. Currently, five different names of Desulfitobacterium species are validly published. Besides halogenated compounds, several members of this group can also utilize heavy metals, in particular arsenic, as electron acceptor. Within this clade, strain Orex-4 was the first representative for which arsenate reduction was
demonstrated. It was originally described as Desulfotomaculum auripigmentum (Newman et al., 1997) but has been recently reclassified as Desulfosporosinus auripigmenti (Stackebrandt et al., 2003). The capacity to reduce arsenic (As[V]) was later also reported in several strains belonging to the genus Desulfitobacterium (Niggemeyer et al., 2001). Because of their unique metabolic potential, the environmental significance of species belonging to the genera Desulfitobacterium and Desulfosporosinus is obvious and has been demonstrated in numerous studies (e.g., Robertson et al., 2000; Breitenstein et al., 2001; Lanthier et al., 2001; Nevin et al., 2003). In the future, members of both genera could play a major role in the bioremediation of contaminated sites by the degradation of anthropogenic halogenated compounds or the removal of
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