Isolation of sulfur oxidizing bacteria from polluted water and screening for their efficiency of sulfide oxidase production

Presence of sulfide in the environment represents huge concerns to biological life. The high costs and low safety of chemical and physical removal strategies lead to finding alternative strategies. Sulfur-oxidizing bacteria (SOB) are consider a promising alternative strategy, where they play a critical role in removal of such compounds from water and soil environments, as well as, they maintain the sulfur balance during natural sulfur cycle. The main objective of this study was to isolate sulfur oxidizing bacteria (SOB) from sulfide polluted water. In addition screening for sulfide oxidase producer bacteria was performed. Twenty isolates of sulfur oxidizing bacteria were isolated from eight different sulfide polluted water sources. During testing the isolates on thiosulfate broth medium, it was observed that, eleven isolates could efficiently reduce the pH of the media from 7.5 ± 0.2 to 5.0 ± 0.5 as a resulting of the oxidizing of sulfides to sulfate ion. The concentration of produced sulfate ion ranged from 76 to 155 mg/mL. The sulfur oxidase activity of the tested isolates ranged between 2.68 to 5.23 U/mL. The bacterial isolates were identified as Bacillus spp., Pseudomonas spp. and Klebsiella spp. based on their morphological and biochemical characterization.