Arsenic resistance genes of As-resistant purple nonsulfur bacteria isolated from As-contaminated sites for bioremediation application.
This study aimed to identify arsenic resistant mechanisms in As-resistant purple nonsulfur bacteria (PNSB) by screening them for presence of As-resistance genes and related enzymes. Resistance to As(III) and As(V) of four As-resistant PNSB determined in terms of median inhibition concentration (IC50 values) were in the order of strains Rhodopseudomonas palustris C1 > R. palustris AB3 > Rubrivivax benzoatilyticus C31 > R. palustris L28 which corresponded to the presence of As-resistance genes in these bacteria. The strain C1 showed all As-marker genes; arsC, arsM, aioA, and acr3, while aioA was not detected in strain AB3. Strains C31 and L28 had only Arsenite-transporter gene, acr3. Translation of all these detected gene sequences of strain C1 to amino acid sequences showed that these proteins have vicinal cysteine; Cys126, Cys105, and Cys178 of Acr3, ArsC, AioA, respectively. Tertiary structure of proteins Acr3, ArsC, AioA, and ArsM showed strain C1 exhibits the high activities of arsenite oxidase and arsenate reductase enzymes that are encoded by aioA and arsC genes, respectively. Moreover, strain C1 with arsM gene produced volatile-methylated As-compounds; monomethylarsonic acid (MMA), dimethylarsenic acid (DMA), and arsenobetaine (AsB) in the presence of either As(III) or As(V). In conclusion, the strain C1 has great potential for its application in bioremediation of As-contaminated sites.
['Nookongbut|Phitthaya|P|', 'Kantachote|Duangporn|D|', 'Krishnan|Kannan|K|', 'Megharaj|Mallavarapu|M|']
D053502:Arsenate Reductases D001149:Arsenates D001151:Arsenic D001152:Arsenicals D018053:Arsenites D001673:Biodegradation, Environmental D002101:Cacodylic Acid D015964:Gene Expression Regulation, Bacterial D005798:Genes, Bacterial D010088:Oxidoreductases D017434:Protein Structure, Tertiary D012241:Rhodopseudomonas D012244:Rhodospirillaceae
purple nonsulfur bacteria As-resistance genes arsenite oxidase arsenate reductase As-methylation