BIODEGRADATION AND UTILIZATION OF ORGANOPHOSPHORUS PESTICIDES BY CYANOBACTERIA

Ten strains of filamentous-heterocystous cyanobacteria were screened for their growth in and tolerance of up to 50 ppm of the organophosphorus pesticides, Monocrotophos and Malathion. Amongst them, Aulosira fertilissima ARM 68 and Nostoc muscorum ARM 221 grew maximally with the pesticides even in the absence of inorganic phosphate in the medium. These two strains were further subjected to varying concentrations of five commonly used organophosphorus pesticides, namely Monocrotophos, Malathion, Dichlorovos, Phosphomidon and Quinolphos both in the presence and absence of inorganic phosphate in the medium, to assess their tolerance as well as the optimum concentration of the pesticide-supported growth. Further experiments carried out with only A. fertilissima ARM 68 established that the pesticides were used as sole sources of P in the absence of inorganic phosphate in the medium and as additional sources of P when inorganic phosphorus was available in the medium. Phosphorus starvation increased the activity of alkaline phosphatase whilst the pesticides induced acid phosphatase activity.