Arsenic tolerant bacteria from marine and non-marine habitats were isolated. Localization studies have shown the presence of arsenite oxidizing enzyme on membrane fractions while arsenate reductase enzyme was found in cytosolic fractions of the bacterial cells. The ars operon of marine bacterium was more enriched than the non-marine bacterium. Presence of arsenite in both the strains generates reactive oxygen species, their effect was inhibited by increased in specific activities of antioxidant enzymes. Arsenite also inhibits activities of some key enzymes of carbon metabolic pathway; to overcome this inhibition each strain adopts different alternate pathways for their survival.