In situ bioremediation of organochlorine-pesticide-contaminated microcosm soil and evaluation by gene probe

BACKGROUND:Pesticide-formulating industries are contaminatingthe environment through various activities. Bioremediation is the bestmethod for decontamination, as chemical and physicalmethods are not only costly but also not very effective in open field systems. In the present study, in situ bioremediation of organochlorine-contaminated soil was demonstrated by combined biostimulation and bioaugmentation strategies, followed by evaluation using amolecular method.RESULTS: Three parameters were monitored: microbial biomass (colony-forming units (CFU) g−1 soil), residual pesticides after treatment and catabolic genes from microcosm soil. Both the biostimulation and the bioaugmentation treatments showed an initial lag phase of 80 days towards colony-forming units. Gas chromatography of soil samples showed that concentrations of residual pesticides in the soil declined by up to 85–90% after 80 days, indicating their utilisation with time. On dot-blot hybridisation of the total DNA from the same soil samples, it was observed that catabolic genes tfdC (catechol1,2-dioxygenase) and cm genes (chlorophenol monoxygenase) were predominant, whereas other catabolic genes such as catechol 2,3-dioxygenase (xylE) were negligible. CONCLUSION: The strategy of in situ bioremediation and its evaluation by gene probe and also by conventional methods was demonstrated for organochlorine-pesticide-contaminated soil in open microcosms. It showed that bioaugmentation alongwith biostimulation was effective, although initial acclimatisation for a period of almost 2–3 months was required in the open field systems