Centre for Environmental Studies, Anna University, CEG Campus, Chennai, Tamil Nadu, India.
Ecotoxicol Environ Saf. 2018 Aug 15;157:40-60. doi: 10.1016/j.ecoenv.2018.03.014. Epub 2018 Mar 30.
Polychlorinated biphenyls (PCBs) are xenobiotic compounds that persists in the environment for long-term, though its productivity is banned. Abatement of the pollutants have become laborious due to it's recalcitrant nature in the environment leading to toxic effects in humans and other living beings. Biphenyl degrading bacteria co-metabolically degrade low chlorinated PCBs using the active metabolic pathway. bph operon possess different genetic arrangements in gram positive and gram negative bacteria. The binding ability of the genes and the active sites were determined by PCB docking studies. The active site of bphA gene with conserved amino acid residues determines the substrate specificity and biodegradability. Accumulation of toxic intermediates alters cellular behaviour, biomass production and downturn the metabolic activity. Several bacteria in the environment attain unculturable state which is viable and metabolically active but not cultivable (VBNC). Resuscitation-promoting factor (Rpf) and Rpf homologous protein retrieve the culturability of the so far uncultured bacteria. Recovery of this adaptive mechanism against various physical and chemical stressors make a headway in understanding the functionality of both environmental and medically important unculturable bacteria. Thus, this paper review about the general aspects of PCBs, cellular toxicity exerted by PCBs, role of unculturable bacterial strains in biodegradation, genes involved and degradation pathways. It is suggested to extrapolate the research findings on extracellular organic matters produced in culture supernatant of VBNC thus transforming VBNC to culturable state.
多氯联苯（PCBs）是一种外来化合物，尽管其生产已被禁止，但它们在环境中仍能长期存在。由于其在环境中的顽固性，这些污染物的减排变得非常困难，导致人类和其他生物产生毒性效应。双苯降解菌通过主动代谢途径共代谢降解低氯代 PCBs。bph 操纵子在革兰氏阳性菌和革兰氏阴性菌中的基因排列不同。通过 PCB 对接研究确定了基因和活性位点的结合能力。bphA 基因的活性位点与保守的氨基酸残基决定了底物特异性和生物降解性。有毒中间产物的积累会改变细胞行为、生物量产生并降低代谢活性。环境中的许多细菌处于不可培养状态，但仍具有生存能力和代谢活性（VBNC）。促复苏因子（Rpf）和 Rpf 同源蛋白恢复了迄今未培养细菌的可培养性。对各种物理和化学胁迫因子的这种适应性机制的恢复，为理解环境和医学上重要的不可培养细菌的功能提供了新的思路。因此，本文综述了 PCBs 的一般特性、PCBs 对细胞的毒性作用、不可培养细菌菌株在生物降解中的作用、涉及的基因和降解途径。建议从 VBNC 细菌的培养上清液中推断出细胞外有机物的研究结果，从而将 VBNC 转化为可培养状态。
