Expression of Genes and Proteins Involved in Arsenic Respiration and Resistance in Dissimilatory Arsenate-Reducing sp. Strain OR-1.

Author(s) Tsuchiya, T.; Ehara, A.; Kasahara, Y.; Hamamura, N.; Amachi, S.
Journal Appl Environ Microbiol
Date Published 2019 Jul 15
Abstract

The reduction of arsenate [As(V)] to arsenite [As(III)] by dissimilatory As(V)-reducing bacteria, such as spp., may play a significant role in arsenic release from anaerobic sediments into groundwater. The biochemical and molecular mechanisms by which these bacteria cope with this toxic element remain unclear. In this study, the expression of several genes involved in arsenic respiration () and resistance () was determined using sp. strain OR-1, the only cultured strain capable of As(V) respiration. In addition, proteins expressed differentially under As(V)-respiring conditions were identified by semiquantitative proteomic analysis. Dissimilatory As(V) reductase (Arr) of strain OR-1 was localized predominantly in the periplasmic space, and the transcription of its gene () was upregulated under As(V)-respiring conditions. The transcription of the detoxifying As(V) reductase gene () was also upregulated, but its induction required 500 times higher concentration of As(III) (500 μM) than did the gene. Comparative proteomic analysis revealed that in addition to the Arr and Ars proteins, proteins involved in the following processes were upregulated under As(V)-respiring conditions: (i) protein folding and assembly for rescue of proteins with oxidative damage, (ii) DNA replication and repair for restoration of DNA breaks, (iii) anaplerosis and gluconeogenesis for sustainable energy production and biomass formation, and (iv) protein and nucleotide synthesis for the replacement of damaged proteins and nucleotides. These results suggest that strain OR-1 copes with arsenic stress by orchestrating pleiotropic processes that enable this bacterium to resist and actively metabolize arsenic. Dissimilatory As(V)-reducing bacteria, such as spp., play significant roles in arsenic release and contamination in groundwater and threaten the health of people worldwide. However, the biochemical and molecular mechanisms by which these bacteria cope with arsenic toxicity remain unclear. In this study, it was found that both respiratory and detoxifying As(V) reductases of a dissimilatory As(V)-reducing bacterium, sp. strain OR-1, were upregulated under As(V)-respiring conditions. In addition, various proteins expressed specifically or more abundantly in strain OR-1 under arsenic stress were identified. Strain OR-1 actively metabolizes arsenic while orchestrating various metabolic processes that repair oxidative damage caused by arsenic. Such information is useful in assessing and identifying possible countermeasures for the prevention of microbial arsenic release in nature.

DOI 10.1128/AEM.00763-19
ISSN 1098-5336
Citation Tsuchiya T, Ehara A, Kasahara Y, Hamamura N, Amachi S. Expression of Genes and Proteins Involved in Arsenic Respiration and Resistance in Dissimilatory Arsenate-Reducing sp. Strain OR-1. Appl Environ Microbiol. 2019;85(14).

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