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/1 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.