Isolation and phylogenetic analysis of a moderately thermophilic acidophilic sulfur oxidizing bacterium

A moderately thermophilic acidophilic sulfur-oxidizing bacterium MTH-04 was isolated from Tenchong area, Yunnan Province in China. The morphological, biochemical and physiological characters of the isolated strain was studied. The cells of the strain MTH-04 were Gram negative and rod-shaped in (0.6-0.8)#mu#m×(1-2)#mu#m. The strain can grow autotrophically by using elemental sulfur, tetrathionate and thiosulfate as sole energy sources. Growth does not occur with tryptone, yeast extract powder and glucose. The strain is not able to grow mixotrophically. The optimum growth temperature is 40℃-45℃ and the optimum pH is 2.0-3.0. The generation time of the strain is 8h. The 16S rDNA sequence (AY427958) of the strain was analysed. A phylogenetic tree was constructd by comparing with the published 16S rDNA sequences of the relative bacteria species. In the phylogenetic tree MTH-04 was the closest relative to Thiobacillus caldus with more than 99.5% sequence similarity.