Department of Genetics, Osmania University, Hyderabad 500 007, India.
Ecotoxicology. 2012 Jan;21(1):202-12. doi: 10.1007/s10646-011-0779-x. Epub 2011 Aug 31.
In the present study, 44 arsenic-resistant bacteria were isolated through serial dilutions on agar plate with concentrations ≥0.05 mM of sodium arsenite and ≥10 mM of sodium arsenate from Mandovi and Zuari--estuarine water systems. The ars genotype characterization in 36 bacterial isolates (resistant to 100 mM of sodium arsenate) revealed that only 17 isolates harboured the arsA (ATPase), B (arsenite permease) and C (arsenate reductase) genes on the plasmid DNA. The arsA, B and C genes were individually detected using PCR in 16, 9 and 13 bacterial isolates respectively. Molecular identification of the 17 isolates bearing the ars genotype was carried using 16S rDNA sequencing. A 1300 bp full length arsB gene encoding arsenite efflux pump and a 409 bp fragment of arsC gene coding for arsenate reductase were isolated from the genera Halomonas and Acinetobacter. Phylogenetic analysis of arsB and arsC genes indicated their close genetic relationship with plasmid borne ars genes of E. coli and arsenate reductase of plant origin. The putative arsenate reductase gene isolated from Acinetobacter species complemented arsenate resistance in E. coli WC3110 and JM109 validating its function. This study dealing with isolation of native arsenic-resistant bacteria and characterization of their ars genes might be useful to develop efficient arsenic detoxification strategies for arsenic contaminated aquifers.
在本研究中，通过在含有≥0.05 mM 亚砷酸钠和≥10 mM 砷酸钠的琼脂平板上进行连续稀释，从曼多维和扎里-河口水系中分离出 44 株砷抗性细菌。对 36 株（耐受 100 mM 砷酸钠）细菌分离株的 ars 基因型特征进行分析，结果表明，只有 17 株菌在质粒 DNA 上携带 arsA（ATP 酶）、B（砷酸盐透性酶）和 C（砷酸盐还原酶）基因。分别使用 PCR 在 16、9 和 13 株细菌中检测到 arsA、B 和 C 基因。使用 16S rDNA 测序对携带 ars 基因型的 17 株菌进行分子鉴定。从盐单胞菌属和不动杆菌属中分离到编码砷酸盐外排泵的全长 1300 bp arsB 基因和编码砷酸盐还原酶的 409 bp arsC 基因片段。arsB 和 arsC 基因的系统发育分析表明，它们与大肠杆菌中的质粒携带 ars 基因和植物来源的砷酸盐还原酶具有密切的遗传关系。从不动杆菌属物种中分离出的推定砷酸盐还原酶基因在大肠杆菌 WC3110 和 JM109 中补充了砷酸盐抗性，验证了其功能。本研究涉及天然砷抗性细菌的分离及其 ars 基因的特征描述，可能有助于为砷污染含水层开发有效的砷解毒策略。
