The potential for reductive mobilization of arsenic [As(V) to As(III)] by OSBH₂(Pseudomonas stutzeri) and OSBH₅(Bacillus cereus) in an oil-contaminated site

Abstract

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.

Natural Arsenic in Global Groundwaters: Distribution and Geochemical Triggers for Mobilization

“…Arsenic in its native form is rare in the environment. In reducing environments, completely protonated arsenite species becomes more predominant over a wide range of pHs without being ionized; hence, arsenite cannot adsorb as strongly as arsenate species [6].…”

“…Natural activities such as weathering, volcanic eruption, rock erosion, and forest fires may release As into the environment. Weathering is the main naturally occurring process through which arsenic sulfides present in ores are converted into a highly mobile form of As [As(V)], which may enter the As cycle directly as a dust or via dissolution in rain, water reservoirs, or groundwater [6,41]. As(III) also may move widely among plants and animals through the food chain.…”

“…Iron deposits, sedimentary iron ores, and manganese nodules are considered As-rich minerals [41]. Important minerals are rich in As, including arsenolite (As 2 O 3 ), olivenite (Cu 2 OHAsO 4 ), cobaltite (CoAsS), proustite (Ag 3 AsS 3 ), enargite (Cu 3 AsS 4 ), orpiment (As 2 S 3 ), realgar (As 4 S 4 ), and tennantite (Cu 6 [Cu 4 (Fe,Zn) 2 ]As 4 S 13 ), and FeAsS is the most abundant As-bearing mineral species found in nature [31,43].…”

“…As a result of such naturally occurring As and human-induced As concentrations, many groundwater systems greatly exceed the safe As guideline value of 10 μg/L recommended by the World Health Organization (WHO) [6,[9][10][11][12][13]. Thus, the elevated As concentration in groundwaters throughout the world has received much attention recently as a serious threat to public health as well as for agricultural activities [14][15][16].…”

“…The primary source of As is natural, derived mainly from the interactions between groundwater and aquifer sediments and hard rocks of minerals, particularly pyrite (FeS 2 ), arsenopyrite (FeAsS), and other unspecified sulfide minerals [4][5][6], as well as secondary As-bearing minerals or mineral coatings, whereas industrial uses, agricultural activities, coal and oil exploitation and combustion, and mining of metal ores are anthropogenic sources that release As into groundwaters [7,8].…”