Isolation and Characterization of As (V)-reducing Bacillus sp. Strain SM-B1 from Arsenic Laden Gold Mine in Malaysia

Abstract

Arsenic is a highly toxic element released into the environment naturally or through human activities. Bacteria are equipped with detoxification mechanisms that enable them to cope with the adverse effects of arsenic. These mechanisms play an important role in biogeochemical cycling of arsenic in the environment. Therefore, this study aimed to isolate arsenic resistant bacteria from arsenic-laden soils in a Malaysian gold mining environment and to characterize their arsenic-transformation ability. Culture enrichment was carried out in LB medium supplemented with As (III) or As (V), resulting in isolation of two bacterial strains. Bacillus sp. SM-B1 showed tolerance to 30 mM As (III) and 350 mM As (V). Acinetobacter sp. SM-S1 demonstrated tolerance to 25 mM As (III) and 300 mM As (V). Bacillus sp. SM-B1 completely reduced 1 mM As (V) in 36 h under aerobic conditions. Putative fragments of arsC and arsB gene were amplified from the genome of isolate SM-B1. Acinetobacter sp. SM-S1 did not show any arsenic transformation activity. Bacillus sp. SM-B1 grown at pH 9 showed potential in arsenic accumulation. Findings generated from this study provide additional details on arsenic-transforming bacteria associated with high arsenic soil and their roles in arsenic biogeochemical cycle in arsenic-contaminated mines in Malaysia.