Degradation of the phenoxy acid herbicide diclofop-methyl by Sphingomonas paucimobilis isolated from a Canadian prairie soil

Sphingomonas paucimobilis , isolated from a soil in Manitoba, Canada, was able to utilize diclofop-methyl, (R,S)-methyl-2-4-(2,4-dichlorophenoxy)phenoxy]propionate, as the sole source of carbon and energy. An actively growing aerobic culture completely degraded 1.5 μg diclofop-methyl ml⁻¹ to diclofop acid within 54 h, at 25°C. A biphasic growth pattern indicated that this organism was capable of degrading diclofop acid to 4-(2,4-dichlorophenoxy)phenol and 2,4-dichlorophenol and/or phenol. The accumulation of 2,4-dichlorophenol in the growth medium, however, suggested that Sphingomonas paucimobilis was unable to utilize this compound as a source of carbon and energy. Received 26 April 1999/ Accepted in revised form 30 July 1999