Desulfotomaculum varum sp nov., a moderately thermophilic sulfate-reducing bacterium isolated from a microbial mat colonizing a Great Artesian Basin bore well runoff channel

A strictly anaerobic moderately thermophilic bacterium, designated strain RH04-3(T) (T = type strain), was isolated from a red colored microbial mat that colonizes a Great Artesian Basin (GAB) bore well (Registered Number 17263) runoff channel at 66 degrees C. The cells of strain RH04-3(T) were straight to slightly curved, sporulating, Gram-positive rods (2.0-5.0 x 1.0 mu m) that grew optimally at 50 degrees C (temperature growth range between 37 and 55 degrees C) and at pH 7 (pH growth range of 5.0 and 8.5). Growth was inhibited by NaCl concentrations >= 1.5% (w/v), and by chloramphenicol, streptomycin, tetracycline, penicillin and ampicillin. The strain utilized fructose, mannose, glycerol, lactate, pyruvate and H-2 in the presence of sulfate, and fermented pyruvate in the absence of sulfate. Strain RH04-3(T) reduced sulfate, sulfite, thiosulfate and elemental sulfur, but not nitrate, nitrite, iron(III), arsenate(V), vanadium(V) or cobalt(III) as terminal electron acceptors. The G + C content of DNA was 52.4 +/- 0.8 mol % as determined by the thermal denaturation (Tm) method. 16S rRNA sequence analysis indicated that strain RH04-3(T) was a member of the genus Desulfotomaculum and was most closely related to Desulfotomaculum putei (similarity value of 95.2%) and Desulfotomaculum hydrothermale (similarity value of 93.6%). On the basis of phylogenetic and phenotypic characteristics, strain RH04-3(T) is considered to represent a novel species of the genus Desulfotomaculum, for which the name Desulfotomaculum varum sp. nov. is proposed. The type strain RH04-3(T) = JCM 16158(T) = KCTC 5794(T).