ABSTRACT
Arsenic (As) is a toxic metalloid which exists widely in the environment. Presently, arsenic contamination from both anthropogenic and natural sources has become a global environmental concern. Arsenic exists in several oxidation states in the environment but the most abundant forms are As (III) and As (V). As (III) is more mobile in aqueous solution and about 100 times more toxic than As (V) (Knowles & Benson 1983). Several arsenic removal technologies are currently available which target the removal of As (V) following a chemical pre-oxidation. The major disadvantages of such techniques are the generation of additional pollutants and high cost. Microorganisms are known to play an important role in geochemical cycling of arsenic of which several bacteria are involved in transformation processes like oxidation, reduction and methylation (Silver & Phung 2005). Although a number of bacterial strains have been isolated since the first report by Green (1918), most of them are slow oxidizers and their physiological role is not well understood. For effective bioremediation of arsenic, it is important to know the diversity of arsenic oxidizing bacteria as well as to explore their oxidation efficiency.
