Microcosm study of atrazine bioremediation by indigenous microorganisms and cytotoxicity of biodegraded metabolites

Intensive use of atrazine in agriculture to increase crop productivity has resulted in pollution and consequently deteriorated the environment. Three isolated bacteria, Rhodococcus sp. BCH2 (RB), Bacillus sp. PDK1 (BP1) and Bacillus sp. PDK2 (BP2) possessing capability to degrade atrazine were used in different combinations (RB + BP1, RB + BP2, BP1 + BP2, RB + BP1 + BP2) to prepare a highly effective bacterial consortium which can significantly reduce the toxicity of atrazine. Cytotoxicity tests evaluated by MTT assay on HepG2 indicated significant decrease in the toxicity of atrazine by the consortium RB + BP1 + BP2 due to its effective degradation and formation of simpler and less/nontoxic metabolites compared to other combinations of consortia. A microcosm study was conducted to check the survivability of this consortium (RB + BP1 + BP2) in the presence of atrazine and indigenous soil microflora for four weeks. LC-Q-TOF/MS analysis revealed that RB + BP1 + BP2 could degrade atrazine to various simple metabolites in the microcosm. The cluster analysis of the DGGE patterns of the microcosm of control-soil, soil exposed to atrazine and soil augmented with consortium in the presence of atrazine (1000 mg kg(-1)) revealed a shift in microbial community of soil. The microbial dynamics studies suggested that the augmented bacteria were well-thrived with natural microflora during four weeks of exposure to atrazine.