Desulfurella amilsii sp nov., a novel acidotolerant sulfur-respiring bacterium isolated from acidic river sediments

A novel acidotolerant and moderately thermophilic sulfur-reducing bacterium was isolated from sediments of the Tinto River (Spain), an extremely acidic environment. Strain TR1(T) stained Gram-negative, and was obligately anaerobic, non-spore-forming and motile. Cells were short rods (1.5-260.5-0.7 mm), appearing singly or in pairs. Strain TR1(T) was catalase-negative and slightly oxidase-positive. Urease activity and indole formation were absent, but gelatin hydrolysis was present. Growth was observed at 20-52 degrees C with an optimum close to 50 degrees C, and a pH range of 3-7 with optimum between pH 6 and 6.5. Yeast extract was essential for growth, but extra vitamins were not required. In the presence of sulfur, strain TR1(T) grew with acetate, formate, lactate, pyruvate, stearate, arginine and H-2/CO2. All substrates were completely oxidized and H2S and CO2 were the only metabolic products detected. Besides elemental sulfur, thiosulfate was used as an electron acceptor. The isolate also grew by disproportionation of elemental sulfur. The predominant cellular fatty acids were saturated components: C-16 : 0, anteiso-C-17 : 0 and C-18 : 0. The only quinone component detected was menaquinone MK-7(H-2). The G + C content of the genomic DNA was 34 mol%. The isolate is affiliated to the genus Desulfurella of the class Deltaproteobacteria, sharing 97% 16S rRNA gene sequence similarity with the four species described in the genus Desulfurella. Considering the distinct physiological and phylogenetic characteristics, strain TR1(T) represents a novel species within the genus Desulfurella, for which the name Desulfurella amilsii sp. nov. is proposed. The type strain is TR1(T) (=DSM 29984(T)=JCM 30680(T)).