Desulfurella amilsii sp. nov., a novel acidotolerant sulfur-respiring bacterium isolated from sediments of the Tinto River

A novel acidotolerant and moderately thermophilic sulfur-reducing bacterium was isolated from sediments of the Tinto River (Spain), an extremely acidic environment. Strain TR1T stains Gram-negative, is obligately anaerobic, non-spore forming and motile. Cells are short rods (1.5-2 by 0.5-0.7 µm),appearing single or in pairs. Strain TR1T is catalase negative and slightly oxidase positive. Urease activity and indole formation were absent. But gelatin hydrolysis occurred. Growth was observed at 20 to 52ºC with optimum close to 50ºC and a pH range of 3 to 7, with optimum between 6 and 6.5. Yeast extract was essential for growth, but extra vitamins were not required. In the presence of sulfur, strain TR1T grew on acetate, lactate, pyruvate, stearate, arginine and H2/CO2. All substrates were completely oxidized and H2S and CO2 were the only metabolic products detected. Besides elemental sulfur, thiosulfate was used as electron acceptor. The isolate also grew by disproportionation of elemental sulfur. The predominant cellular fatty acids were saturated C16:0 (26.2%), anteiso-C17:0 (13.2%) and C18:0 (21.8%). The only quinone component detected was menaquinone MK-7(H2). The G+C content of genomic DNA was 34%. The isolate is affiliated to the genus Desulfurella of the Deltaproteobacteria class showing 97% of 16S rRNA gene identity to the four species described in the Desulfurella genus. Considering the distinct physiological and phylogenetic characteristics, strain TR1T represents a novel species within the genus Desulfurella, for which the name Desulfurella amilsii sp. nov. is proposed. The type strain of Desulfurella amilsii is TR1T (= DSM 29984T = JCM 30680T)