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 obt ained from the Kysing Fjord south of Arhus (Denmark) and strains Gypro p(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 red uction of elemental sulfur to hydrogen sulfide. A comparative 16S ribo somal DNA sequence analysis revealed that these five strains, together with a previously described isolate (strain Go11), constitute a coher ent cluster of descent. This cluster belongs phylogenetically to a bra nch of the delta subclass of the Proteobacteria and is characterized b y members of the genera Pelobacter and Desulfuromonas. Within the clus ter strains Kysw2(T) and Kyval, strains Gyprop(T) and Kyprop, and stra ins Gylac(T) and Go11 have identical 16S ribosomal DNA sequences. The levels of DNA-DNA relatedness were 89% between strains Kysw2(T) and Ky val, 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 o f genomic data and phenotypic characteristics, a new genus, Desulfurom usa, is described; this new genus includes three new species, for whic h the names Desulfuromusa kysingii, Desulfuromusa bakii, and Desulfuro musa succinoxidans are proposed. The type species of the genus Desulfu romusa 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.