Isolation and characterization of an alkaliphilic bacterium capable of growing on 2,4-dichlorophenoxyacetic acid and 4-chloro-2-methylphenoxyacetic acid

A bacterial strain, called P4a, was isolated from debris of concrete samples of a demolished herbicide factory. The samples were contaminated with chlorinated and methylated phenoxyalkanoic acids. Strain P4a was able to utilize 2,4-dichloro- (2,4-D) and 4-chloro-2-methylphenoxyacetic acid (MCPA) as the sole source of carbon and energy; degradation of 2,4-dichlorinated and 4-chloro-2-methylated phenoxypropionic acid and -butyric acid derivatives was not found. Growth on 2,4-D was observed from a pH of 5.6 up to a pH of about 10, with optimum growth at around 8.5. No supplements were found to be required for growth on 2,4-D, but the presence of yeast extract increased the growth rate from less than 0.05 h(-1) to 0.2 h(-1). The strain was metabolically active up to pH values of 12, which corresponded to the pH of aqueous eluates from such material. It was able to degrade 2,4-D under these conditions up to an initial concentration of 400 mg/l and in fact did degrade 1,600 mg/l of 2,4-D at an initial pH value of 11. Strain P4a was tentatively identified as Comamonas acidovorans on the basis of the substrate utilization pattern (BIOLOG), fatty acid profile (MIS) and G+C content.