Arsenite-oxidizing bacteria isolated from arsenic contaminated surface and ground water of Uttar Pradesh, India

Arsenic (As) contamination of surface and ground waters in Uttar Pradesh (UP) is geological in nature, even though some degree of As contamination may be due to anthropogenic activities. Little is known about the arsenite oxidizing bacteria in aquatic environments of UP. In this study we isolated the As resistant bacteria from both surface and ground waters of UP. Seven potential strains were isolated by culture method using chemically defined medium (CDM). Two strains (AOB-GP1 and AOB-MT1) were Gram negative and other five were found to be Gram positive. The presence of arsenite oxidizing bacteria in groundwater is limited if compared to surface waters. 16S rDNA revealed highest homology of 99 - 88%. The strains were similar with Acinetobacter sp. PGSI1, Rummeliibacillus stabekisii, Cronobacter sakazakii, Bacillus tequilensis, Brevibacillus agri strain, Bacillus thuringiensis and Virgibacillus marismortui. The 16S rDNA gene sequence analysis for the As-resistant strains in surface and ground waters points to prevalence of γ-proteobacteria and Firmicutes, solely isolated γ-Proteobacteria (Acinetobacter sp. and Cronobactersakazakii sp.) from ground water samples. Based on morphological, cultural, biochemical and physiological characteristics the arsenite oxidizing bacteria in this study were grouped into three orders viz,. pseudomonadales, enterobacteriales and bacillales.