Arsenic-resistance mechanisms in bacterium Leclercia adecarboxylata strain As3-1: Biochemical and genomic analyses
2019
Abstract Microbial arsenic transformation is important in As
biogeochemical cyclesin the environment. In this study, a new As-resistant bacterial strain Leclercia adecarboxylata As3-1 was isolated and its associated mechanisms in As resistance and detoxification were evaluated based on genome sequencing and gene annotations. After subjecting strain As3-1 to media containing arsenate (AsV), AsV reduction occurred and an AsV-enhanced
bacterial growthwas observed. Strain As3-1 lacked
arsenite(AsIII) oxidation ability and displayed lower AsIII resistance than AsV, probably due to its higher AsIII accumulation. Polymerase chain reaction and phylogenetic analysis showed that strain As3-1 harbored a typical AsV reductase gene ( arsC ) on the plasmids. Genome sequencing and gene annotations identified four
operonsphoUpstBACS , arsHRBC , arsCRDABC and ttrRSBCA , with 8 additional genes outside the
operonsthat might have involved in As resistance and detoxification in strain As3-1. These included 5 arsC genes explaining why strain As3-1 tolerated high AsV concentrations. Besides ArsC, TtrB, TtrC and TtrA proteins could also be involved in AsV reduction and consequent energy acquisition for
bacterial growth. Our data provided a new example of diverse As-regulating systems and AsV-enhanced growth without ArrA in bacteria. The information helps to understand the role of As in selecting microbial systems that can transform and utilize As.
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