Use of Indigenous Bacteria from Arsenic Contaminated Soil for Arsenic Bioremediation

Abstract

Arsenic (As) is a ubiquitous element found in the earth’s crust. It is now ranked first in a list of 19 hazardous substances by the Agency for Toxic Substances and Disease Registry and United States Environmental Protection Agency (Goering et al. 1999; Prerna et al. 2007). Among different chemical forms of As in the environment, the most often encountered toxic forms are arsenite [As(III)] and arsenate [As(V)] (Buchet and Lauwerys 1981; Leonard 1991; Mukhopadhyay et al. 2002). The abundance of different arsenic forms and its mobility in soil depends on several factors like pH, redox potential, presence of other elements, organic matter content, texture and biotic functions therein (Woolson 1977). When environmental conditions change, the speciation and mobility of arsenic may also change. As(III) is more toxic due to its affinity to bind with functional groups, like SH⁻ and imidazolium nitrogens of different biomolecules including catalytic proteins (Krumova et al. 2008). On the other hand, arsenate (AsO₄ ³⁻) mimics phosphate (PO₄ ³⁻); thus it affects cell metabolism by interfering with phosphorylation processes (Tseng 2004).