Biodegradation of mono-hydroxylated PCBs by Burkholderia xenovorans
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ORIGINAL RESEARCH PAPER
Biodegradation of mono-hydroxylated PCBs by Burkholderia xenovorans Rouzbeh Tehrani • Monica M. Lyv • Rashid Kaveh • Jerald L. Schnoor • Benoit Van Aken
Received: 3 July 2012 / Accepted: 16 August 2012 / Published online: 24 August 2012 Ó Springer Science+Business Media B.V. 2012
Abstract Three hydroxylated derivatives of PCBs, 20 hydroxy-4-chlorobiphenyl (20 -OH-4-CB), 30 -hydroxy-4chlorobiphenyl (30 -OH-4-CB), and 40 -hydroxy-4-chlorobiphenyl (40 -OH-4-CB), were transformed by the PCB degrader, Burkholderia xenovorans. When the bacterium was growing on biphenyl (biphenyl pathway-inducing conditions), all three hydroxylated isomers were transformed. However, only 20 -OH-4-CB was transformed by the bacterium growing on succinate (conditions noninductive of the biphenyl pathway). Gene expression analyses showed a strong induction of key genes of the biphenyl pathway (bph) when cells were grown on biphenyl, which is consistent with the transformation of Electronic supplementary material The online version of this article (doi:10.1007/s10529-012-1037-x) contains supplementary material, which is available to authorized users. R. Tehrani M. M. Lyv R. Kaveh B. Van Aken (&) Department of Civil and Environmental Engineering, Temple University, Philadelphia, PA 19122, USA e-mail: [email protected] R. Tehrani e-mail: [email protected] M. M. Lyv e-mail: [email protected] R. Kaveh e-mail: [email protected] J. L. Schnoor Department of Civil and Environmental Engineering, University of Iowa, Iowa City, IA 52242, USA e-mail: [email protected]
the three isomers by biphenyl-grown cells. When cells were grown on succinate, only exposure to 20 -OH-4-CB resulted in expression of biphenyl pathway genes, which suggests that this isomer was capable of inducing the biphenyl pathway. These results provide the first evidence that bacteria are able to metabolize PCB derivatives hydroxylated on the non-chlorinated ring. Keywords Biodegradation Biphenyl dioxygenase Burkholderia xenovorans Hydroxylated polychlorinated biphenyl
Introduction Polychlorinated biphenyls (PCBs) are toxic environmental contaminants that are somewhat recalcitrant to biodegradation. Due to their high chemical and physical stability and high dielectric constant, PCBs have been used widely for a variety of industrial applications, including lubricants, dielectric fluids, and plasticizers. Because of their toxicity and recalcitrance to biodegradation, the production and usage of PCBs were banned in most countries by the late seventies (Field and Sierra-Alvarez 2008; Pieper and Seeger 2008). In the meanwhile, PCBs have been largely dispersed in the environment and they are today detected in every compartment of the ecosystem. The first step of the PCB metabolism by higher organisms results in the formation of hydroxylated
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derivatives, which are increasingly suspected to be responsible for the toxicity of PCBs. Hydroxylated PCBs (OH-PCBs) are known to induce various deleterious effects, including disru
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