Thesis

Microbes that degrade chloropicrin

Methyl bromide is a broad-spectrum pesticide that successfully controls insects, weeds, rodents, and several pathogens in agricultural crops; however, its use is strongly restricted by international agreement. Consequently, pesticides including inline, methyl iodide, propargyl bromide and chloropicrin have been proposed as alternatives. We have isolated and identified bacterial strains that degrade chloropicrin using traditional techniques and sequencing analysis of the 16S ribosomal subunit. These organisms are able to grow on media containing chloropicrin as a sole carbon source. The rate of chloropicrin degradation was determined using gas chromatography comparing bacterial mediated degradation to abiotic degradation in sterile pesticide media. Pesticide levels were monitored in minimal medium containing 100 ppm chloropicrin and inoculated with a chloropicrin degrading suspect. Nine organisms were characterized and identified from strawberry soils in Watsonville, California. Identified bacteria are from Frateuria, Bacillus, Sphingomonas, Streptomyces, Fulvimonas and Rhodanobacter genera. Rhodanobacter sp., Sphingomonas mali, and Bacillus firmus enhanced chloropicrin degradation compared to the abiotic control. Bacillus sp., and Sphingomonas pruni may degrade products of abiotic chloropicrin degradation that have formed from the interactions of the minimal media and chloropicrin. This study will be useful in determining the environmental fate of the pesticide and the development of bioremediation strategies for removal of pesticide.

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