Physiological Characteristics And Phylogeny Of Three Sulfur-Oxidizing Bacteria (SOB) Strains

Biological oxidation of sulfur is one of the major reactions in global material cycle. Sulfur-oxidizing prokaryote can oxidaze S⁰ or reduced sulfur compounds to sulfate. Therefore, they are benefit for biohydrometallurgy and biodesulfurization. In this report, we isolated three Sulfur-oxidizing bacteria (SOB) from different mining areas in China (Guangdong, Xinjiang, Jiangxi). The aim of the present work was to unravel their physiological properties and phylogenetic relationships, then to discuss their potential role in application.By the observation of morphology, the three SOB were all Gram-negative, rods (0.5～1.5×0.2～0.4um) , motile, no capsula and spore. Optimum growth temperature was 30℃. Optimum pH of DBS-4, FY-2, YP-5 were 5.5, 4.5, 6.5, respectively. They can use sulfur, thiosulfate and tetrathionate as energy for growing, but can not utilize Fe²⁺ and any organic compound independently. If supplemented yeast extract (0.02%) when use sulfur compounds as energy, the growth would be better. Therefore, the three SOB were mixotrophic and acidotolerant microorganism.By the analysis of 16S rRNA gene, we can see that they had an overall similarity above 99% with some bacteria which were not identified to species level. The similarities of the three SOB (DBS-4, FY-2, YP-5) with At. caldus were 91.9%, 93.2%, 90.0%, respectively. Otherwise, the similarities with At.thiooxidans and At.ferrooxidans were much less than 90%. These indicated that, all the three SOB belonged to the genus Acidithiobacillus.In addition, data on tolerance of some metals showed that, DBS-4 was more tolerant of Cu²⁺ and Zn²⁺ than others, while was most sensitive to Ni²⁺. YP-5 was the most tolerant of Ni²⁺, while was the most sensitive to Cu²⁺. All the three SOB's abilities of tolerance to Mn²⁺ are similar. Besides, the SDS-PAGE analysis of whole-cell protein band profiles manifested they not only had differences with At.thiooxidans ATCC 19377^T and At.ferrooxutans ATCC 23270^T, but also had some variability among themselves. The data above indicated different environments led to different physiological characterizations and composition of protein.In short, the isolates FY-2, DBS-4, YP-5 differentiated markerly from three well-characterized species of the genus Acidithiobacillus. Additional data , such as ubiquinone analysis of cell wall, genome DNA-DNA hybridization identity and G+C mol% content,need to be acquired before these taxa can described as new species.