MICROBIAL-DEGRADATION OF FLURIDONE

Microbial consortia collected from two lakes degraded fluridone [1-methyl-3-phenyl-5-[3-(trifluoromethyl)-phenyl]-4-(lH)-pyridinone] when placed in liquid culture. Microorganisms from Lake McLeod (no previous fluridone application) degraded 40% of the fluridone in solution while microbes from Lake Pierce (prior fluridone application) degraded 26% of the compound over a 150 day period. When heterogeneous cultures from Lake McLeod were transferred to new liquid cultures which contained fluridone, 99% of the herbicide was degraded over a 370 day period. These enriched cultures were grown using media that contained alternate carbon sources plus fluridone or minerals plus fluridone. Ninety-nine percent of the fluridone in the minerals plus fluridone medium was degraded. Cultures in the other media grew rapidly, but little fluridone was degraded. This indicates that there are carbon sources preferentially assimilated over fluridone. These degradation rates do not indicate that past fluridone use influences fluridone degradation. However, continued exposure to high rates of the compound can increase the rate of microbial breakdown under experimental conditions.