Determination of cypermethrin degradation potential of soil bacteria along with plant growth-promoting characteristics.

The pyrethroid insecticide cypermethrin is in extensive use since 1980s for insect control. However, its toxicity toward aquatic animals and humans requires its complete removal from contaminated areas that can be done using indigenous microbes through bioremediation. In this study, three bacterial strains isolated from agricultural soil and identified as Acinetobacter calcoaceticus MCm5, Brevibacillus parabrevis FCm9, and Sphingomonas sp. RCm6 were found highly efficient in degrading cypermethrin and other pyrethroids. These bacterial strains were able to degrade more than 85 % of cypermethrin (100 mg L(-1)) within 10 days. Degradation kinetics of cypermethrin (200 mg kg(-1)) in soils inoculated with isolates MCm5, FCm9, and RCm6 suggested time-dependent disappearance of cypermethrin with rate constants of 0.0406, 0.0722, and 0.0483 d(-1) following first-order rate kinetics. Enzyme assays for Carboxylesterase, 3-PBA dioxygenase, Phenol hydroxylase, and Catechol-1,2 dioxygenase showed higher activities with cypermethrin treated cell-free extracts compared to non-treated cell-free extracts. Meanwhile, SDS-PAGE analysis showed upregulation of some bands in cypermethrin-treated cells. This might suggest that cypermethrin degradation in these strains involves inducible enzymes. Besides, the isolates displayed substantial plant growth-promoting traits such as phosphate solubilization, Indole acetic acid production, and ammonia production. Implying the efficient biodegradation potential along with multiple biological properties, these isolates can be valuable candidates for the development of bioremediation strategies.