Characterization of two novel propachlor degradation pathways in two species of soil bacteria

Propachlor (2-chloro-N-isopropylacetanilide) is an acetamide herbicide used in preemergence. In this study, we isolated and characterized a soil bacte rium, Acinetobacter strain BEM2, that was able to utilize this herbicide as the sole and limiting carbon source. Identification of the intermediates o f propachlor degradation by this strain and characterization of new metabol ites in the degradation of propachlor by a previously reported strain of Ps eudomonas (PEM1) support two different propachlor degradation pathways, Was hed-cell suspensions of strain PEM1 with propachlor accumulated N-isopropyl acetanilide, acetanilide, acetamide, and catechol, Pseudomonas strain PEM1 grew on propachlor with a generation time of 3.4 h and a K-s of 0.17 +/- 0. 04 mM. Acinetobacter strain BEM2 grew on propachlor with a generation time of 3.1 h and a K-s of 0.3 +/- 0.07 mM. Incubations with strain BEM2 resulte d in accumulation of N-isopropylacetanilide, N-isopropylaniline, isopropyla mine, and catechol. Both degradative pathways were inducible, and the princ ipal product of the carbon atoms in the propachlor ring was carbon dioxide, These results and biodegradation experiments with the identified metabolit es indicate that metabolism of propachlor by Pseudomonas sp. strain PEM1 pr oceeds through a different pathway from metabolism by Acinetobacter sp, str ain BEM2.