Indigenous Mixed Soil Bacteria in Presence of Compatible Plants Are More Efficient in Pcb Degradation

This paper presents data on comparative studies of unknown mixed cultures of indigenous microorganisms versus single cultures isolated from PCB-contaminated soil samples containing varying concentrations of PCBs (polychlorinated biphenyls). Remediation of PCBs was studied using isolated indigenous mixed cultures, by indigenous single colony cultures, in presence or absence of the leguminous alfalfa (Medicago sativa) plant. The congener 2 ́, 3, 4-PCB was used as known standard to spike the mixture of clean soil and vermiculite. Analytical methods such as HPLC (high performance liquid chromatography) and GC (gas chromatography) were used for PCB degradation quantification. The plant experiments were carried out in a controlled growth chamber environment with a 16-hr fluorescent and incandescent light period which mimicked day light. Results obtained suggest that higher the PCB concentration in soil, the more efficient the indigenous soil bacteria particularly in presence of plants. Mixed indigenous cultures were 2 –3 times more efficient than single cultures. When compared to known PCB co-metabolizing bacteria such as Comamonas testosteroni and Rhodococcus sp., indigenous bacteria showed not only higher amount of PCB degradation, but also significantly better growth as evidenced by the CFU (colony forming units) counts. When the alfalfa plant was present, the indigenous mixed cultures were even more effective than known and unknown single cultures. These findings suggest that a combination of endemic microorganisms utilized with alfalfa plant is a promising approach for bioremediation of PCBcontaminated soils.