Biodegradation of chlorobenzene by indigenous bacteria

Soil and ground water from four sites chronically contaminated with chlorobenzenes were examined to determine whether indigenous bacteria could degrade the contaminants and whether the addition of specific chlorobenzene-degrading bacteria enhanced the degradation rate At each site, chlorobenzene-degrading bacteria were readily isolated from chlorobenzene contaminated wells, whereas similar samples from noncontammated wells yielded no chlorobenzene degrading bacteria Isolates were tested for growth on a variety of substrates At a site contaminated with several solvents, a bioreactor was inoculated with the chlorobenzene degrading Pseudomonas sp strain JS150 Contaminated water was pumped through this bioreactor and a control bioreactor that had been colonized by indigenous microorganisms The contaminants were removed from both bioreactors, however, JS150 could not be recovered from the inoculated bioreactor after three weeks of operation A follow up lab study using ground water from the contaminated site confirmed the field results We conclude that chlorobenzene contamination of soil causes the development of indigenous degradative populations that have a competitive advantage over inoculated strains The mechanism and time course of this acclimation are poorly understood and require additional study