Degradation of 2,5- and 3,4-dichlorobenzoic acids by bacterial species indigenous to rotten onion bulb and PCB-contaminated soil

Pseudomonas sp. strain OCB-01 and Micrococcus sp. strain PCB-02 exhibiting dichlorobenzoic acid (diCBA) metabolic properties were isolated respectively from rotten onion bulb and polychlorinated biphenyl-contaminated soil by enrichment culture containing equivalent amounts of 2,5-diCBA and 3,4-diCBA. In addition to both diCBAs, organisms were subsequently found to also grow on 3-CBA, 4-CBA, and a wide range of aromatic and non-aromatic compounds. Growth on 2,5-diCBA and 3,4-diCBA resulted in two to four orders-of-magnitude cell increases with nearly 100% consumption of the substrate yielding an overall metabolic rate of 0.005 mM h−1. Although strain OCB-01 appeared to utilize the congeners better, no statistical difference was observed in all incubations. The isolation of diCBA-degrading organism from rotten onion bulb is unprecedented, and this has again reinforced the fact that degraders of organopollutants may be widely distributed across diverse environmental systems than previously thought and may offer reasons for many failures in isolation of such organisms.