Anti-Arylsulfatase B (N-terminal) monoclonal antibody, clone 20H7.2

Arsenic resistance genes were isolated from the moderately thermophilic, Grain-positive iron and sulfur-oxidizing bacterium, Sulfobacillus thermosulfidooxidans. Only arsR and arsB genes were present and attempts to identify an arsC using degenerate PCR primers or dependent arsC genes as probes in Southern hybridization experiments were unsuccessful. Although enhanced resistance to arsenite was not detected when the ars genes were cloned in Escherichia coli, the kumamolisin-As and arsRB genes were induced by arsenite. RT-PCR experiments suggested that transcription of the cloned kumamolisin-As-like and arsRB genes is linked in Escherichia coli, but not in Sb. thermosulfidooxidans. The gene order kumamolisin-As precursor, arsR and arsB was maintained among three strains of Sb. thermosulfidooxidans isolated from three continents. Southern hybridization using a Sb. thermosulfidooxidans arsB gene fragment as a probe gave a positive hybridization signal using S. acidophilus but not with S. thermotolerans genomic DNA. Comparison of partial sequence data of the arsB and 16S rRNA genes suggested that the two types of genes have undergone a similar evolutionary history and therefore that the arsB genes were present in the ancestral Sulfobacillus before its divergence into species.

In the present study, 44 arsenic-resistant bacteria were isolated through serial dilutions on agar plate with concentrations a parts per thousand yen0.05 mM of sodium arsenite and a parts per thousand yen10 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.