Microbial Degradation of Pesticides.
Rept no. 1 (Annual), 1 Oct 77-30 Sep 78,
CORNELL UNIV ITHACA N Y DEPT OF AGRONOMY
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Fifty-two bacteria isolated from sewage, temperate soil, and various tropical soils were tested for their ability to attack 2,4-D and 2,4,5-T. Fourteen caused the disappearance of 35 to 100 of the 2,4-D and nine brought about the destruction of 20 to 100 of the 2,4,5-T. None of the organisms could use 2,4-D or 2,4,5-T as a sole source of carbon. Degradation of 2,4-D and phenoxyacetic acid in nonsterile sewage and a tropical soil was greatly enhanced by pretreating the sewage and soil with these compounds, suggesting the selection for organisms capable of attacking 2,4-D and phenoxyacetic acid. Cell yields of the three most active 2,4,5-T degraders in a medium with glucose, glycerol, and sodium succinate and in a benzoate-supplement medium with and without 2,4,5-T did not differ, suggesting cometabolic attack. Resting cell suspensions of nine of the isolates cleaved chlorine from the 2,4,5-T molecule while metabolizing more than 40 of the 2,4,5,-T, suggesting ring cleavage of the herbicide. Eight isolates produced chlorinated phenol from 2,4,5-T. Studies of the respiratory activity of three isolates also suggested ring cleavage of 2,4,5-T. By use of 14C-ring-UL 2,4,5-T, it was found that the herbicide was readily metabolized in a tropical soil. Author