engleski

Response of the PCB-contaminated soil bacterial community to applied bioremediation treatments

For full field implementation of the bioremediation as a strategy for cleaning PCB-contaminated soils, the impact of the applied treatment on the microbial community needs to be clarified. An ideal bioremediation should have positive effects on PCB-removal but should pose no treats to the health of the soil ecosystem. Microbes, playing an essential role in maintenance of the soil ecosystem, are the first indicators of a negative impact of soil manipulation to ecosystem. A small-scale bioremediation experiment was conducted in order to get insight into behavior of the microbial community during bioremediation of PCB-contaminated soil, targeting both functional PCB-degrading community (by bph catabolic genes) and total soil microbial community (by 16S-23S IGS i.e. community at lower population level and 16SrRNA i.e. community at higher phyla taxonomic level). Assay incorporated different approaches: (a) biostimulation (addition of carvone as inducer of biphenyl pathway, soya lecithin for enhancing PCB bioavailability and xylose as supplemental carbon source) and (ii) bioaugmentation (addition of mixed culture TSZ7 or pure strain Rhodococcus sp. Z6, showing substantial PCB-degrading activity). Bioremediation was shown to enhance PCB-reduction in soils, with approx. 40% of total PCBs being removed during a one-year period. Microbial community developed after 18-month bioremediation treatments had distinct genetic structure from the native community. Shift was confirmed in both PCB-degrading community and global bacterial community: (i) bph-based phylogeny revealed Rhodococcus-like bacterial populations developing as key players in PCB-degradation, (ii) bacterial communities in soils under different treatments had distinct genetic structures and (iii) abundances of 11 targeted phyla significantly changed with Actinobacteria, Bacteriodetes, α- and γ-Proteobacteria being enriched under all three bioremediated treatments. Such way of monitoring behavior of bacterial community during bioremediation could give new insight into managing of PCBs contaminated sites.

polychlorinated biphenyls; biodegradation; bioremediation; bph genes; Rhodococcus

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