BIODEGRADATION OF GLYPHOSATE CONTAINING HERBICIDE BY SOIL BACTERIA

Abstract

Sixty bacterial isolates were isolated from two herbicide contaminated soil farms (Amoyo and University of Ilorin Nursery section both in Kwara State) after enrichment with mineral salt medium (MSM) supplemented with glyphosate containing herbicide. The organophosphorus herbicide efficiently stimulated the growth of bacterial isolates. Bacteria isolated were subjected to screening using varying concentrations of the herbicide ranging from 0.1 to 3% prepared with mineral salt medium. This screening revealed that all the bacterial isolates had biodegradative potential. They however had varying degradative potentials as some had heavy growth while others had only slight growth or no growth on increased concentrations of herbicide. Screening reduces the bacterial populations with growth ranging from 5.0 x 10⁴ to 2.33 x 10⁸ while the number of bacterial isolates reduced from sixty to thirteen. These bacterial isolates were Pseudomonas putida, Bacillus safenis, Lysinibacillus fusiformis, Micrococcus sp., Arthrobacter sp., Aeromonas sp., Bacillus cereus, Flavobacterium sp., Acinetobacter rhizoshaerae, Bacillus pumilus, Achrobacterium sp., Bacillus sp., and Ochrobacterium sp. The increase in viable bacterial counts over the period of 21 days indicated the use of herbicide as carbon source for their various metabolism processes. These bacteria can be recommended as environmentally safer alternatives tools to protect soil from excessive use of glyphosate containing herbicide residues which might contaminate the soil.