The crude electronic waste (e-waste) recycling activities released a large amount of persistent organic pollutants, such as polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs), into the soils posing a serious threat to the ecological environment and human health. Microbial degradation is an important way of PCBs dissipation.

However, in practical application, the bioremediation of PCBs is challenged due to limited available degrading microbial species and the toxicity of high concentrations of heavy metals in the e-waste contaminated soil.

Recently, Dr. JIANG Longfei and Prof. LUO Chunling at Guangzhou Institute of Geochemistry of Chinese Academy of Sciences used ¹³C-biphenyl as a labeled compound and combined DNA stable isotope probing (DNA-SIP), a culture independent technology, with high-throughput sequencing, which offered high-resolution identification of the functional microbial communities and bphA genes, to explore the active biphenyl-utilizing bacteria in e-waste-contaminated soil from Qingyuan city.

In this study, there were 21 OTUs including Ralstonia,Cupriavidus and DA101 identified as the PCBs degraders. Among them, Ralstonia and Cupriavidus were widely studied bacterium with a powerful ability to degrade organic pollutants. But the ability of PCBs degradation of DA101 was firstly reported.

Researchers amplified a 13.8 kb bph operon, containing a bphA gene labeled by ¹³C that was concentrated in the heavy DNA fraction. To analyze the structure of the operon, they revealed the PCBs degradation mechanism and proved the horizontal gene transfer ability of this operon which is due to the existing of the transposase encoding gene.

To fill the gap between functional microbes and genes, they employed the tetranucleotide fingerprint features as the bridge, and showed the relationship between tetranucleotide fingerprint features of bph operon and specific bacteria. It was found that the bph operon was originated from Ralstonia.

The study was published in Environmental Science & Technology. It provided a deeper insight into the mediator of aerobic PCBs degradation in heavy-metal- and PCB-co-contaminated environments, as well as the functional genes, their probable regulatory mechanisms and the relationship between functional microbes and genes. The finding would be meaningful in PCBs remediation and gene resource discovery and application.

This study was supported by National Natural Science Foundation of China and the Scientific, Technological Planning Project of Guangzhou, China, and the Department of Science and Technology of Guangdong Province.