Bioremediation of Certain Organophosphorus Pesticides by Two Biofertilizers, Paenibacillus( Bacillus) polymyxa (Prazmowski ) and Azospirillum lipoferum (Beijerinck)

Continuous and excessive use of organophosphorus compounds has led to the contamination of water and soil ecosystems. The degradation of organophosphorus insecticides, chlorpyrifos, chlorpyrifos- methyl, cyanophos and malathion in mineral salts media were studied. The effect of additional biofertilizers, singly or combined with organic amendments, on chlorpyrifos and cyanophos degrading activity in soil were investigated. Paenibacillus ( Bacillus) polymyxa (Prazmowski ) and Azospirillum lipoferum (Beijerinck) were found to degrade the organophosphorus insecticides, chlorpyrifos, chlorpyrifos- methyl, cyanophos and malathion in mineral salts media as a carbon and phosphorus source. Paenibacillus ( Bacillus) polymyxa (Prazmowski ) appeared to be more effective than Azospirillum lipoferum in degrading all the tested organophosphate pesticides in mineral salts media. The half-life values (t۱/۲) of chlorpyrifos, chlorpyrifos – methyl , cyanophos and malathion were found to be undetectable , undetectable , ۲.۴, and undetectable days in mineral salts media inoculated by Paenibacillus ( Bacillus) polymyxa (Prazmowski ),while they reached ۱.۶, ۰.۱, ۵.۲, and ۰.۸ days by Azospirillum lipoferum (Beijerinck) compared to ۴.۴, ۱.۸, ۸.۸, and ۱.۴ days in non-inoculated mineral salts media. Chlorpyrifos and cyanophos degraded in soil samples inoculated by Azospirillum lipoferum (Beijerinck) plus peat- moss more rapidly than in the other treatments. Dual inoculation of Azospirillum lipoferum (Beijerinck) and Paenibacillus ( Bacillus) polymyxa (Prazmowski ) improved the rate of degradation of chlorpyrifos and cyanophos in soil. Azospirillum lipoferum (Beijerinck) appeared to be more effective than Paenibacillus ( Bacillus) polymyxa (Prazmowski ) in degrading soil-applied chlorpyrifos and cyanophos. These results highlight the potential of these bacteria to be used in the clean- up of contaminated pesticides – waste in the environment.