Functional genomic studies have established that even organisms harboring high numbers of homologous enzymes seem to contain few examples of true redundancy.

Analyses have indicated that recent genetic flux appears to have played a more significant role in the evolution of some large genomes, such as Burkholderia xenovorans LB400, than in others.

However, the emerging trend is that the large gene repertoires of potent pollutant degraders such as B. xenovorans LB400 have evolved principally through more ancient processes.

That this is true in such phylogenetically diverse species is remarkable and further suggests the ancient origin of this catabolic capacity.

Aromatic compounds are among the most recalcitrant of organic pollutants and much interest is seen in using microbial biodegradation to clean up contaminated sites.