Gene manipulation and regulation of catabolic genes for biodegradation of biphenyl compounds

Polychlorinated biphenyls (PCBs) are organic compounds that find a large number of applications at industrial level. Due to their low bioavailability and stability, they are persistent in the environment and also impose deleterious effects on animals and plants. Degradation of these compounds by microbes is a cost-effective strategy to remove these hazardous compounds from the environment and is also receiving greater attention. A number of microbes belonging to phylum Actinobacteria, Ascomycota, Bacteroidetes, Basidiomycota Firmicutes, and Proteobacteria of the genera Achromobacter, Arthrobacter, Aspergillus, Bacillus, Janibacter, Janthinobacterium, Ochrobactrum, Paenibacillus, Pseudomonas, Rhodococcus, Shigella, Sphingobium, Sphingomonas, Stenotrophomonas, Talaromyces, Trametes, and Williamsia have been reported to degrade PCBs. There are many reports on the study of the degradation pathways used by the microbes to degrade these compounds as well as the detailed enzymatic steps involved. Further, the catabolic genes (bph) responsible for the degradation in diverse microbes have been studied, which shows a greater diversity in the arrangement of these genes. Also, bph genes have been cloned from different bacterial strains. The study of biodegradation is a complex process and requires the combined study of microbial ecology, biochemistry, and genetic engineering with the aim that the efficient strains may be improved for enhanced degradation and to understand how microbes acquire novel degradation capabilities.