Isolation, Characterization and Biodegradation Assay of Glyphosate Utilizing Bacteria from Exposed Rice Farm

Abstract

Two bacterial species capable of utilizing glyphosate were isolated from the long term glyphosate exposed rice farm and tested for their abilities to utilize glyphosate at different concentrations. The two bacterial isolates were identified by standard bacteriological methods as Pseudomonas sp and Bacillus subtilis using their morphological, biochemical and growth characteristics. The utilization of glyphosate by the isolates was studied by monitoring their biomass production in basal medium containing glyphosate as phosphorus source at 660nm wavelength using the spectrophotometer. The growth of the isolates in the medium with inorganic phosphate as phosphorus source and the effect of different concentrations of glyphosate on the growth and utilization of glyphosate were also studied by assessing the turbidity in the medium at 660nm wavelength. The isolates showed a significant growth in the basal medium containing glyphosate as phosphorus source (P<0.05). Nevertheless, the test organisms showed a better growth rate in the medium with inorganic phosphate as phosphorus source. The effect of different concentrations showed that Pseudomonas sp grew significantly at concentrations of 7.2 mg/ml to 40 mg/ml while B. subtilis showed a reduction in growth with corresponding increase in glyphosate concentration. The results of this study nonetheless underscored the efficacy of the test bacterial isolates in glyphosate utilization, hence their potential as candidates for bioremediation of glyphosate contaminated farmland in poor resource settings.

Keywords: Glyphosate herbicide, Utilization pattern, Pseudomonas sp., Bacillus subtilis.