Biodegradation of endosulfan and pendimethalin by three types of bacteria isolated from pesticides polluted soils

Biodegradation of endosulfan (α and β) and pendimethalin by Pseudomonas aeruginosa,Bacillus mycoides and Bacillus cereus isolated from pesticides polluted soil were studied in mineral salt medium. Endosulfan and pendimethalin were incubated with each of the three types of bacteria with samples drawn at 0, 3, 7, 14 and 30 days for gas chromatographic analysis. Loss in the initial concentrations, 0.663 mML^-1(for αendosulfan); 0.319 mML^-1(for β endosulfan) and 1.423 mML^-1for pendimethalin were monitored and used to compute the half Lives following a biphasic model. GC-MS was used to identify the major metabolites. Remaining amount of endosulfan and pendimethalin recovered from media inoculated with P. aeruginosa for 3, 7, 14 and 30 days were; 0.499, 0.405, 0.272 and 0.25 mML^-1 (α endosulfan); 0.25, 0.186, 0.127 and 0.114 mML^-1(β endosulfan), and  0.533, 0.233, 0.224 and 0.186 mML^-1(pendimethalin) respectively. While the amount recovered from media inoculated with B. mycoides were; 0.057, 0.046, 0.043 and 0.031 mML^-1 (α endosulfan); 0.029, 0.029, 0.025 and 0.024 mML^-1 (β endosulfan);0.628, 0.275, 0.266, and 0.230 mML^-1following the same order. On the other hand, the respective amount recovered from B. cereus culture were; 0.292, 0.271, 0.222 and 0.198 mML^-1 (α endosulfan) and 0.123, 0.122, 0.1 and 0.096 mML^-1   (β endosulfan) 0.387, 0.362, 0.301 mML^-1( pendimethalin). Despite the significant decrease in starting material in P. aeruginosa cultures no metabolites were detected, whereas two major metabolites of endosulfan; 1,2,3,4,7,7-hexachloro-5,6-dihydroxybicyclo{2.2.1}-2-heptene and 1,2,3,4,7,7-hexachloro-formaldehyde-6-methylbicyclo{2.2.1}-2-heptene,were detected in B.mycoides culture and one metabolite of pendimethalin metabolite; N-(1-ethylpropyl)-3-methyl-2, 6-diaminobenzine was detected in Bacillus cereus culture.Generally the result indicates the potential capability of these microorganisms in complete mineralization of endosulfan and pendimethalin. Based on the half-lives, the efficiency of the bacterial species can be ordered as follows; Bacillus mycoides >Bacillus cereus> Pseudomonas aeruginosa for endosulfan and Bacillus cereus >Pseudomonas aeruginosa > Bacillus mycoides for pendimethalin.