Adaptation of microbial communities in soil contaminated with polychlorinated biphenyls, leading to the transformation of more highly chlorinated congeners in biofilm communities

Abstract

A site polluted for many years with polychlorinated biphenyls (PCB) was used to elucidate the metabolic adaptation of microbial communities to these xenobiotics. Soil samples taken along a gradient of PCB-pollution at this site were used to grow biofilm communities on PCB oil. The biofilm communities originating from the non-polluted soil formed rather uniform and thin bacterial layers on PCB oil, while the biofilms originating from contaminated soil samples formed agglomerated structures on the PCB droplets. Biofilm communities were very diverse but those from highly polluted soil were dominated byBurkholderiaspecies, a genus known for degrading several PCBs. All biofilm communities could transform low to medium chlorinated PCB congeners but a strong increase in the rate and degree of PCB transformation in communities from heavily polluted soil was observed. Notably, pentachlorinated congeners were transformed only by biofilms derived from the highly polluted soil but at the same time the content of trichlorinated congeners did not decrease. It is assumed that biofilms from the highly contaminated soil reductively dechlorinated PCB, converting pentachlorinated congeners to trichlorinated congeners in the spherical biofilm aggregates by diffusing to the surface of the aggregates, where aerobic transformation took place.

Implications of microbial adaptation for the assessment of environmental persistence of chemicals

“…Microbial adaptation has been observed in a variety of contaminated environments, such as aquifers (Aelion et al, 1987;Aelion, Dobbins, & Pfaender, 1989;Alidina et al, 2014), fresh water (Schwab, Maruscik, Palmisano, & Ventullo, 1992), (Larson & Davidson, 1982), estuaries (Pfaender et al, 1985), wastewater treatment plants plants (Chonova et al, 2016;Itrich et al, 2015), sediment (Shimp, 1989) and soil (Macedo, Neu, Kuhlicke, & Abraham, 2006). Below, we present five examples of directed microbial adaptation that are well described in the literature.…”

“…This may well be the result of differences in bioavailability of the compound, of differences in specific growth conditions, or of differences in metabolic potential within the bacterial community. d. Adaptation of soil communities to some congeners of polychlorinated biphenyls (PCBs) has also been observed (Macedo et al, 2006). Growth of a microbial biofilm on a highly contaminated soil leads to an increase in the transformation rate of PCBs, in comparison to a biofilm community without history of exposure.…”

“…Growth of a microbial biofilm on a highly contaminated soil leads to an increase in the transformation rate of PCBs, in comparison to a biofilm community without history of exposure. Furthermore, biofilms derived from a highly polluted site were the only ones able to transform pentachlorinated congeners (Macedo et al, 2006). In addition, genes involved in chlorobiphenyl degradation were exchanged between introduced bacteria and indigenous biphenyl degraders (Focht, Searles, & Koh, 1996).…”

Multi-Parameter Laser Imaging Reveals Complex Microscale Biofilm Matrix in a Thick (4,000 μm) Aerobic Methanol Oxidizing Community

“…Microsensors and imaging have been used to demonstrate steep oxygen and pH gradients in a variety of aerobic biofilm systems indicating the importance of diffusion processes and structure in biofilm systems (Dalsgaard and Revsbech, 1992 ; DeBeer et al, 1994 ; Lawrence et al, 2016 ). A variety of confocal microscopy studies have also confirmed the importance of cell distribution patterns, void spaces and channels in the architecture of degradative biofilm communities (Wolfaardt et al, 1994 ; Massol-Deyá et al, 1995 ; Macedo et al, 2005 , 2007 ; Wouters et al, 2010 ). Neef et al ( 1996 ) carried out an analysis of a methanol fed biofilm concentrating on the application of in situ hybridization to define populations of bacteria present in the biofilm community.…”

Advances and perspective in bioremediation of polychlorinated biphenyl-contaminated soils

“…In this line, anaerobic dechlorination of PCBs has also been reported for various contaminated sites (Pakdeesusuk et al 2005). Macedo et al (2007) observed transformation of highly chlorinated PCB congeners as an effect of adaptation of microbial communities in contaminated soil. A group of microorganisms within the dechlorinating Chloroflexi that appear to be common in PCB contaminated sites may catalyse reductive dechlorination activity (Watts et al 2005).…”