Isolation, phenotypic characterization, and phylogenetic position of a novel, facultatively autotrophic, moderately thermophilic bacterium, Thiobacillus thermosulfatus sp. nov.

Abstract

Thiobacillus thermosulfatus ATCC 51520T (T = type strain) was isolated from sewage sludge samples enriched with elemental sulfur. The cells of this organism were gram negative, rod shaped, motile, facultatively autotrophic, and strictly aerobic and contained polyphosphate inclusions and polyhedral bodies. During growth on thiosulfate, the following intermediates were produced: tetrathionate, trithionate, and sulfate, and the pH was lowered from neutrality to around 2.5. Autotrophic growth was observed at pH values between 4.3 and 7.8 and at temperatures of 34 to 65 degrees C; optimum growth occurred at pH 5.2 to 5.6 and 50 to 52.5 degrees C. Ubiquinone Q8 was present in the respiratory chain. The DNA contained 61 +/- 1 mol% G+C. No denitrification was observed under autotrophic and heterotrophic conditions. The cells produced a glycocalyx during growth in the presence of S0. As determined by a 16S rRNA gene sequence analysis, T. thermosulfatus is a distinct species that belongs to the beta subdivision of the Proteobacteria and is closely related phylogenetically to Thiobacillus perometabolis. The GenBank accession number for the complete 16S rRNA gene sequence of T. thermosulfatus is U27839.