Microbial interactions with cyclodiene pesticides



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The interactions of a mixed bacterial culture of pseudomonads were investigated particularly concerning the biodegradation of the cyclodiene pesticides. Four isolates were presented in a floc forming culture which gave evidence for, at least, partial degradation of simulated technical heptachlor through isolation of acidic metabolites, evolution of labelled CO2, and isolation of metabolic by-products. Quite unique to the system was the ability of one isolate to grow by fixing CO2 as a carbon source, which was also the same isolate to degrade the pesticide to CO2. At least one isolate (Texas 2) was shown to grow best on acetone, while another (Texas 4) grew best on the acetone- pesticide. Evidence for a proposed biodegradation pathway presented was supplied by identified pesticide metabolites, nine unknown metabolites, and the literature. Results show a tremendous concentration of pesticides by the bacterial system. Experiments show the accumulation to be selective with regard to chlorination. Most significant in this investigation is the mutalistic relationship in the mixed bacterial population. Evidence was presented for a greater biological activity of the mixed culture on the pesticides than in the individual isolates. Although the total degradation achieved, even in the mixed culture, was not tremendously high for the purpose of this study, the results are very encouraging. Action of the organisms on the pesticides was significant and possibly achieved degradation completely to biological compounds.