title: Arsenite-oxidizing and arsenate-reducing bacteria associated with arsenic-rich groundwater in Taiwan.
abstract: Drinking highly arsenic-contaminated groundwater is a likely cause of blackfoot disease in Taiwan, but microorganisms that potentially control arsenic mobility in the subsurface remain unstudied. The objective of this study was to investigate the relevant arsenite-oxidizing and arsenate-reducing microbial community that exists in highly arsenic-contaminated groundwater in Taiwan. We cultured and identified arsenic-transforming bacteria, analyzed arsenic resistance and transformation, and determined the presence of genetic markers for arsenic transformation. In total, 11 arsenic-transforming bacterial strains with different colony morphologies and varying arsenic transformation abilities were isolated, including 10 facultative anaerobic arsenate-reducing bacteria and one strictly aerobic arsenite-oxidizing bacterium. All of the isolates exhibited high levels of arsenic resistance with minimum inhibitory concentrations of arsenic ranging from 2 to 200 mM. Strain AR-11 was able to rapidly oxidize arsenite to arsenate at concentrations relevant to environmental groundwater samples without the addition of any electron donors or acceptors. We provide evidence that arsenic-reduction activity may be conferred by the ars operon(s) that were not amplified by the designed primers currently in use. The 16S rRNA sequence analysis grouped the isolates into the following genera: Pseudomonas, Bacillus, Psychrobacter, Vibrio, Citrobacter, Enterobacter, and Bosea. Among these genera, we present the first report of the genus Psychrobacter being involved in arsenic reduction. Our results further support the hypothesis that bacteria capable of either oxidizing arsenite or reducing arsenate coexist and are ubiquitous in arsenic-contaminated groundwater.
authors.affiliation: Department of Bioenvironmental Systems Engineering, National Taiwan University, 1 Roosevelt Road, Sec. 4, Taipei 106, Taiwan. vivianliao@ntu.edu.tw
authors.forename: Vivian Hsiu-Chuan
authors.initials: VH
authors.lastname: Liao
authors.forename: Yu-Ju
authors.initials: YJ
authors.lastname: Chu
authors.forename: Yu-Chen
authors.initials: YC
authors.lastname: Su
authors.forename: Sung-Yun
authors.initials: SY
authors.lastname: Hsiao
authors.forename: Chia-Cheng
authors.initials: CC
authors.lastname: Wei
authors.forename: Chen-Wuing
authors.initials: CW
authors.lastname: Liu
authors.forename: Chung-Min
authors.initials: CM
authors.lastname: Liao
authors.forename: Wei-Chiang
authors.initials: WC
authors.lastname: Shen
authors.forename: Fi-John
authors.initials: FJ
authors.lastname: Chang
mesh_terms: D001149:Arsenates / Q000378:metabolism*; D018053:Arsenites / Q000378:metabolism*; D001419:Bacteria / Q000235:genetics / Q000302:isolation & purification* / Q000378:metabolism; D001483:Base Sequence; D004269:DNA, Bacterial / Q000737:chemistry / Q000235:genetics; D005618:Fresh Water; D008826:Microbial Sensitivity Tests; D008969:Molecular Sequence Data; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D012336:RNA, Ribosomal, 16S / Q000737:chemistry / Q000235:genetics; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D013624:Taiwan; D014871:Water Microbiology
chemical_list: D001149:Arsenates; D018053:Arsenites; D004269:DNA, Bacterial; D012336:RNA, Ribosomal, 16S; C015001:arsenite; C025657:arsenic acid