Biodegradation and rapid removal of methyl parathion by the paddy field cyanobacterium Fischerella sp.

Abstract

A paddy field cyanobacterial isolate that is capable of degrading and utilizing the organophosphorus pesticide methyl parathion (MP) as a phosphate source has been characterized as Fischerella sp. To investigate the MP removal and degradation capabilities of this cyanobacterium along with the mechanism it has adopted to combat the pesticide's toxicity, different doses of MP (0, 5, 10, 20 and 30mgL−1) were applied to the cyanobacterial culture. At 20mgL−1 of MP, the cyanobacterium efficiently modulated its antioxidative defense system and its fatty acid and hydrocarbon profiles to support growth. The initial rapid removal of methyl parathion (~80%) was due to the adsorption of the pesticide onto the cyanobacterial surface. Fourier transform infrared (FTIR) spectral analysis revealed that MP interacts with the OH group on the cell surface, and this chemical interaction may lead to chemisorptions. The initial removal pattern has followed the pseudo-second-order kinetics model of biosorption that also defines the chemisorptions mechanism. The appearance of p-nitrophenol in the medium coupled with modulation of the physiological indices of this cyanobacterium has indicated that biosorption followed by the simultaneous bioaccumulation and biodegradation of MP led to its complete removal from the medium. Under phosphorus-deficient conditions, MP exposure induced the growth and intracellular alkaline phosphatase activity of the cyanobacterium, which both support the view that the organism can use this pesticide as a phosphorus source. Thus, due to its tremendous efficiency in degrading and removing the organophosphorus pesticide MP, the isolated cyanobacterium Fischerella sp. can be used as a potent bioremediation agent.