POTENTIAL ROLE OF ARSENIC REDUCTION [AS(V) TO AS(III)] BY OSBH2 (PSEUDOMONAS STUTZERI) AND OSBH5 (BACILLUS CEREUS) IN OIL-CONTAMINATED SITE

Microbial reduction of arsenate [As(V)] plays an important role in arsenic (As) mobilization in aqueous environment. In this study, we investigated reduction characteristics of arsenate by different bacterial isolates such as OSBH₁ (GU329913), OSBH₂ (GU329914), OSBH₃ (GU329915), OSBH₄ (GU329916) and OSBH₅ (GU329917), isolated from oil sludge of sewage treatment plant, China Petroleum Refinery Company in Kaohsiung, southern Taiwan. Bacterial strains of pure culture were identified by 16S-rRNA analysis (≥99% similarity). Morphological and 16S-rRNA analysis exhibits that the isolate OSBH₁ is similar to E. coli, OSBH₂ to P. stutzeri, OSBH₃ to P. Putida, OSBH₄ to P. aeruginosa, and OSBH₅ to B. Cereus. The results also exhibited that isolates OSBH₂ and OSBH₅ reduced efficiently As(V) to As(III). The rate of arsenic reduction was found higher in the presence of OSBH₅ isolate than in the presence of OSBH₂ isolate. Also, the microbial growth (cell/ml) of OSBH₅ was noticed higher in the As(V) culture medium than that of OSBH₂. The bacteria isolates such as OSBH₁, OSBH₃ and OSBH₄ were found not capable of reducing arsenate or oxidation of arsenite. It is concluded that the activity of the described oil degrading bacterial isolates contributes to the mobilization of arsenic in the more toxic As(III) form and which affects the biotic life.