Bioremediation of Arsenic-Contaminated Environment Using Bacteria: An Update

Recently, environmental pollution due to arsenic contamination has become a global concern. Rapid industrialization and urbanization activities along with technological advancement are continuously increasing the heavy metal (including arsenic) load in the environment. Arsenic contamination in soil, water, air, and sediment environment from various anthropogenic and geogenic sources is a major environmental issue in many regions of the world including India owing to its hazardous nature in the biological ecosystem. The content of arsenic(III/V) causes severe human health and mortality problems to millions of people worldwide annually when present at an eminent concentration (>0.05 mg/L) level. Arsenic is generally nonbiodegradable, but it can be transformed to its less toxic form through oxidation-reduction or methylation reaction and can be immobilized through sorption, complexation, and precipitation processes. Bioremediation of arsenic using bacteria is now gaining increasing global 406attention due to its greater advantages over conventional physicochemical methods. During arsenic bioremediation, bacterial biomass can interact with arsenic metal ions by passive and/or active bioremediation mechanisms including extracellular adsorption/entrapment/precipitation, intracellular absorption, methylation, and oxidation-reduction process. Indigenous arsenic-resistant bacteria (heterotrophs and chemo-litho-autotrophs) present in the arsenic-contaminated area developed resistance against arsenic toxicity, which were substantially used for arsenic detoxification processes. This chapter provides insight into recent information about the global arsenic pollution, arsenic toxicity, and successful implementation of arsenic-resistant bacteria isolated from both saline and nonsaline sources in an environmentally safe and cost-effective manner. It also gives a clear understanding about the possible mechanisms involved in the bacterial arsenic bioremediation process.