The horizontal catabolic gene pool, or how microbial communities can rapidly adapt to environmental pollutants

Retrospective studies such as comparative DNA sequence analyses and characterization of mobile genetic elements (MGEs) in bacteria clearly indicate that horizontal gene transfer (HGT) mechanisms play an important role in the exchange and even de novo construction of degradation pathways in bacterial communities. Such HGT processes thus allow these communities to rapidly adapt to xenobiotic compounds by providing the members with the genetic information required to cope with these novel, often toxic, compounds. Direct evidence for the importance of MGEs in bacterial adaptation to xenobiotics stems from observed correlations between catabolic gene transfer and accelerated biodegradation in several habitats, or from studies that monitor catabolic MGEs in polluted sites. The combination of these different studies demonstrate that HGT and pathway assembly are key to the adaptation of bacterial communities to xenobiotics, but many questions remain about the rates at which these processes occur and the selection on the MGEs that drive this genetic exchange.