PROPACHLOR DEGRADATION BY A SOIL BACTERIAL COMMUNITY

Soil from a pesticide disposal site was used to enrich for microorganisms that degraded the acylanilide herbicide propachlor (2-chloro-N-isopropylacetanilide). After seven transfers of the enrichment, the culture contained about six strains. The highest yield of microbial biomass occurred if just two of these isolates, strains DAK3 and MAB2, were inoculated into a mineral salts medium containing propachlor. When only strain DAK3 was grown on propachlor, a metabolite (2-chloro-N-isopropylacetamide) was released into the medium. Strain MAB2 could grow on this metabolite. The results of morphological and physiological tests suggest that strains DAK3 and MAB2 most closely resemble species belonging to the genera Moraxella and Xanthobacter, respectively. Strain DAK3 can respire and grow on N-substituted acylanilides containing methyl, ethyl, or isopropyl substitutions, but is incapable of respiration or growth on acetanilide, aniline, or the acylanilide herbicides alachlor and metolachlor. Strain DAK3 appears to use the aromatic C atoms of propachlor for growth, as suggested by the growth yield on propachlor and the induction of catechol 2,3-oxygenase activity in acylanilide-grown cells.