PHYLOGENETIC ANALYSIS OF 5 STRAINS OF GRAM-NEGATIVE, OBLIGATELY ANAEROBIC, SULFUR-REDUCING BACTERIA AND DESCRIPTION OF DESULFUROMUSA GEN-NOV, INCLUDING DESULFUROMUSA-KYSINGII SP-NOV, DESULFUROMUSA-BAKII SP-NOV, AND DESULFUROMUSA-SUCCINOXIDANS SP-NOV

Gram-negative, mesophilic, obligately anaerobic strains Kysw2(T) (T = type strain), Kyval, and Kyprop isolated from an anoxic mud sample obtained from the Kysing Fjord south of Arhus (Denmark) and strains Gyprop(T) and Gylac(T) isolated from the Guayamas Basin (Gulf of California) all exhibit complete oxidation of a wide range of electron donors (e. g., dicarboxylic acids and amino acids) linked to stoichiometric reduction of elemental sulfur to hydrogen sulfide. A comparative 16S ribosomal DNA sequence analysis revealed that these five strains, together with a previously described isolate (strain Go11), constitute a coherent cluster of descent. This cluster belongs phylogenetically to a branch of the delta subclass of the Proteobacteria and is characterized by members of the genera Pelobacter and Desulfuromonas. Within the cluster strains Kysw2(T) and Kyval, strains Gyprop(T) and Kyprop, and strains Gylac(T) and Go11 have identical 16S ribosomal DNA sequences. The levels of DNA-DNA relatedness were 89% between strains Kysw2(T) and Kyval, 98% between strains Gyprop(T) and Kyprop, and 73% between strains Gylac(T) and Go11. The levels of DNA-DNA relatedness between members of the three DNA relatedness groups were less than 30%. On the basis of genomic data and phenotypic characteristics, a new genus, Desulfuromusa, is described; this new genus includes three new species, for which the names Desulfuromusa kysingii, Desulfuromusa bakii, and Desulfuromusa succinoxidans are proposed. The type species of the genus Desulfuromusa is D. kysingii. Strains Kysw2 (= DSM 7343), Gyprop (= DSM 7345), and Gylac (= DSM 8270) are the type strains of D. kysingii, D. bakii, and D. succinoxidans, respectively.