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Abstract

Agricultural soil was inoculated in a basal mineral medium (BMM) containing methyl parathion (MP) with glucose (0.5 mg/ml) and without glucose. Mixed bacterial cultures and four pure bacterial cultures, isolated from soil, were able to degrade MP (50 µg/ml) in BMM. Bacillus sp. and two unknowns, isolated from the mixed culture in the BMM with glucose, were able to degrade only the commercial grade MP in the BMM with glucose, but were able to degrade the analytical grade MP in the BMM without glucose. Burkholderia cepacia was the best MP-degrading bacterium. It was isolated from the mixed culture in the BMM without glucose. The bacterium was able to grow in the BMM at all pH ranges (pH 4-pH8) and salinity levels (0-3.5% NaCl). The addition of glucose (0.5 mg/ml) did not enhance the MP-degrading ability of Burkholderia cepacia. Burkholderia cepacia at 6x10 7 cells/ml degraded MP at 50, 100, and 150 µg/ml in standard BMM rapidly (t 1/2 = 0.55, 0.58, and 0.87 hour). Furthermore, p-nitrophenol (PNP), a hydrolysis product of MP, was completely degraded by Burkholderia cepacia. MP and PNP were carbon sources for growth of Burkholderia cepacia.