The potential for reductive mobilization of arsenic [As(V) to As(III)] by OSBH(2) (Pseudomonas stutzeri) and OSBH(5) (Bacillus cereus) in an oil-contaminated site.

Microbial reduction of arsenate [As(V)] plays an important role in arsenic (As) mobilization in aqueous environments. In this study, we investigated reduction of arsenate by different bacterial isolates such as OSBH(1) (GU329913), OSBH(2) (GU329914), OSBH(3) (GU329915), OSBH(4) (GU329916) and OSBH(5) (GU329917), isolated from the oil sludge of a sewage treatment plant operated by the China Petroleum Refinery Company in Kaohsiung, southern Taiwan. Bacterial strains of pure culture were identified by 16S rRNA analysis (≥99 % nucleotide similarity). Morphological and 16S rRNA analysis show that the isolate OSBH(1) is similar to E. coli, OSBH(2) is similar to P. stutzeri, OSBH(3) is similar to P. putida, OSBH(4) is similar to P. aeruginosa, and OSBH(5) is similar to B. Cereus. The As(V) was transformed to As(III) in the presence of isolates OSBH(2) and OSBH(5) by a detoxification process. The potential reduction rates of As(V) were higher in the presence of isolate OSBH(5) compared to the isolate OSBH(2). The microbial growth (cell/mL) of isolate OSBH(5) was significantly higher in culture medium compared to OSBH(2). The bacterial isolates such as OSBH(1), OSBH(3) and OSBH(4) were found to be incapable of transforming the As(V). It is concluded that the activity of the oil-degrading bacterial isolates described in this work contributes to the mobilization of As in the more toxic As(III) form that affects biotic life.