The biotransformation potential of Bacillus cereus on β- cypermethrin to protect the earthworm (Perionyx excavatus) on insecticide -contaminated soil

Abstract

ABSTRACT The pre-isolated B. cereus had shown better β-cypermethrin resistance at 100 mg L−1 dosage in the Mineral Salt Medium (MSM). Hence, it was applied for the biodegradation study on MSM. The GC-MS analysis revealed that the B. cereus had the potential to degrade β-cypermethrin and metabolize it into six predominant less or nontoxic components (benzene, 1-ethyl−3-methyl-, ethanethiol, 2-(dimethylamino)-, 1-(2-acetoxyethyl)-3,6-diazahomoadamantan-9-one, silane, 9-anthracenyltrimethyl-, 1-(3-hydroxy-3-methylbutyl)-3,6-,fumaric acid). Based on this biodegradation potential, four experimental groups, namely A, B, C, D and control, were framed and the biodegradation potential of B. cereus on β-cypermethrin and interaction with P. excavates were studied. Group C, which includes B. cereus and 10 P. excavates under β-cypermethrin stress excavates positive survival interaction. It was confirmed by the presence of metabolites such as benzene, 1-ethyl-3-methyl-, ethanethiol, 2-(dimethylamino)- and 1-(2-acetoxyethyl)-3,6-diazahomoadamantan-9-one, in P. excavates. Furthermore, these were similar to the metabolites of β-cypermethrin degraded by B. cereus. These results conclude that the biodegradation potential of B. cereus can protect the life of P. excavates from β-cypermethrin toxicity and thus, can support the balancing of soil fertility, structure and soil biotas such as flora and fauna. Abbreviations: MSM: mineral salt medium; g: gram; kg: kilogram; GC-MS: gas chromatography–mass spectrometry; mg L−1: milligram per litter; mL: milliliter; mg: milligram; min: minutes; MSTFA:N-methyl-N-(trimethylsilyl) trifluoroacetamide; EC: electric conductivity; N: nitrogen; P: phosphate; K: potassium; ECD: electron capture detector; OC: organic carbon; LB: Luria–Bertani; ºC: temperature in Celsius; pH: potential of hydrogen; R.T: retention time; NIST: National Institute of Standards and Technology; rpm: rotations per minute; TNAU: Tamil Nadu Agriculture University