ISOLATION AND CHARACTERIZATION OF ARSENIC-RESISTANT BACTERIA FROM ARSENIC-ENRICHED AGRICULTURAL SOILS OF CHIANAN PLAIN, SOUTHWESTERN TAIWAN

The health hazards associated with As-contaminated soil coupled with the high remediation cost makes it necessary to search for novel As-resistant bacteria, efficient enough for bioremediation of polluted land. Novel arsenic (As) resistant aerobic heterotrophs capable of As transformation were isolated from agricultural soil of Chianan plain, SW Taiwan by enrichment technique. Eight As(III)-oxidizing isolates (rate of oxidation from 0.029 to 0.059 μM h^-1 10^-9 cell; half-lives of 23.9 - 11.7 h) belong to Pseudomonas, Acinetobacter, Klebsiella and Comamonas genera, whereas four As(V)-reducing isolates (rate of reduction from 0.034 to 0.038 μM h^-1 10^-9 cell; half-lives of 20.4 - 18.2 h) belong to Geobacillus, Bacillus, Paenibacillus, and Enterobacter genera. Neither of the As(III)-oxidizing isolates grew in media with As(III) as primary electron donor for chemolithotrophic metabolism nor the As(V)-reducing isolates grew on media designed for dissimilatory As(V) reduction, suggesting their As transformation via detoxification mechanisms as opposed to energy generation. In addition, resistance of these isolates to high contents of As(III) and As(V) and the ability to grow on wide range of pH (pH 6, 7, 8 and 9) and temperature (20, 30 and 40 °C) signify their great potential for application in remediation of As in environment in a sustainable way.