PCB degradation potential by bacteria from lakes of the Edmondson Point area (Antarctica)

The use of polychlorinated biphenyls (PCBs) has been prohibited since the 1970s in western nations. However, their widespread use and chemical stability has led to extensive environmental contamination, even in remote areas. PCBs can be transformed into chemical substances by different microbial metabolic pathways. This work was aimed at analyzing Antarctic bacterial strains able to degrade PCBs at low temperature, with a focus on the metabolic pathways. Water and sediment samples were collected in four different lakes (EP-1, EP-2, EP-3 and EP-4) in the Edmonson Point area (Antarctica). Isolates were obtained from biphenyl enriched cultures, and preliminarily screened for their ability to use Aroclor 1242 as sole carbon source. Positive strains were identified by the 16S rRNA amplification and sequencing, and the presence of the bphA gene, involved in the first step of aerobic degradation of PCBs, was screened by PCR amplification. Results showed that 57 out of 192 isolates were able to grow in the presence of Aroclor 1242, with the 25.5% and 18.6% that were from sediment and water, respectively. Further, the 87.5% of the positive strains sowed the presence of the bphA gene and were mainly affiliated to Actinobacteria (mainly genera Salinibacterium and Arthrobacter) and Betaproteobacteria (mainly genus Alcaligenes). Obtained results showed a percentage of PCB-oxidizing bacteria higher than those previously reported in Antarctic environments. This suggests that the microbial communities of Antarctic lakes and ponds could be adapted to the presence of these pollutants.