Abstract:In this study, a chemoautotrophic sulfur-oxidizing bacterial strain LS2 was isolated from brewery wastewater. The analyses of 16S rRNA gene and sulfur-oxidizing enzyme gene soxB revealed that this strain was most closely related to genus Halothiobacillus, although the genome of Halothiobacillus sp. LS2 had a complete gene cluster encoding nitrogen-fixing enzyme Nif; Its key gene nifH had the highest similarity to A. ferrooxidans and A. ferrivorans in the genus Acidithiobacillus (both of which were higher than 80%). A comparative study at the cellular level indicated that the strain LS2 was able to grow under both nitrogen and nitrogen-free conditions. The maximum growth of LS2 under the condition of 1 mM NH4+ could reach 1.98×107/mL, whilst the growth in the absence of nitrogen (up to 1.37×107/mL) was less than that in the presence of nitrogen. The gene expression analysis revealed that nifH expression of strain LS2 was down-regulated due to the presence of a nitrogen source but up-regulated with the increase of thiosulfate concentration. The expression of nifH was up-regulated by 33 times at a S2O32-concentration of 5 mM, indicating that nitrogen fixation was closely related to sulfur oxidation. In this study, a chemoautotrophic sulfur-oxidizing bacterium with nitrogen-fixing ability was obtained, and the obtained results can provide a new idea for the treatment of sulfide-containing wastewater.
