Isolation, characterization, and phylogenetic position of a new sulfur-oxidizing bacterium

Abstract

A sulfur-oxidizing bacterium was isolated from mine wastewater and characterized. The isolate was gram-negative, rod (0.2 × 1.2-1.5 μm), nonmotile, catalase positive, and oxidase positive. The optimal pH and temperature for growth were 7.0 and 30°C, respectively. The optimum thiosulfate concentration was 70 mM and the maximum growth rate was 0.081 hr-1. The major ubiquinone contained in the isolate was Q-8. The cellular fatty acid composition was C16:0, C16:1, C18:1, C17cyc, and C19cyc as nonpolar fatty acids, and 3-OH C10:0 and 3-OH C12:0 as hydroxylated fatty acids. The isolate was a facultative chemolithoautotroph which can grow autotrophically on sodium thiosulfate and sodium sulfide and which can grow heterotrophically on yeast extract. It can also grow mixotrophically on sodium thiosulfate and yeast extract. Comparison of the 16S rRNA gene sequence of the isolate with that of Thiobacillus species and Paracoccus thiocyanatus revealed that it is closely related to T. caldus which belongs to the β-subclass of the class Proteobacteria. However, the isolate could not grow at extremely low pH (pH 1-3.5). On the basis of the phenotypic, chemotaxonomic and phylogenetic data, the isolate was tentatively named Thiobacillus sp. strain C.