Isolation and characterization of an As(III) oxidizing bacterium, Acinetobacter sp. TMKU4 from paddy field for possible arsenic decontamination

Abstract

During past few decades arsenic (As), a poisonous and carcinogenic water and soil contaminant, is perceived as a significant universal environmental snag. The exploration of As-resistant microorganisms for mitigation of As-contaminated environment has been proven to be both economical and ecologically favourable among the various techniques so far documented. Several As-resistant bacterial isolates were isolated from the soil sample of As affected area of Nadia, a district in West Bengal, India. On the basis of maximum As resistance ability, an arsenite [As(III)]-oxidizing bacterial strain, TMKU4, was selected, which could withstand 12.5 mM As(III) and 95 mM arsenate [As(V)]. The strain was noted to be closely linked to the genus Acinetobacter as per 16S rDNA sequence analysis and biochemical characterization. Within 14 h of incubation on minimal salts medium, this strain could convert ∼78% of As(III) to As(V). Kinetic evaluation of partially purified As(III) oxidase from the bacterial cells exhibited Km of 73.38 μM and Vmax of 0.3456 μM min−1 μg−1 protein. The existence of the As(III) oxidase gene was further confirmed through PCR with degenerate primers. TMKU4 exhibits potential plant growth-promoting attributes owing to which it could also be exploited as a promising As bioremediation strategy for sustainable agriculture.