Genes for the degradation of organic pollutants have usually been allocated to plasmid DNAs in bacteria or considered non-mobile when detected in the chromosome. New have shown that catabolic genes can also be part of so-called integrative and conjugative elements (ICElands), a group of mobile DNA elements also known as genomic islands and conjugative transposons. One such ICEland is the c/c element chlorobenzoate and chlorocatechol degradation in Pseudomonas sp. strain B13. Genome comparisons and data on integrase functioning reveal that the c/c element and several other unclassified ICElands belong to a group of elements with conserved features. The c/c element is unique among them in carrying the genetic information for several degradation pathways, whereas the others give evidence for pathogenicity functions. Many more such elements may exist, bridging the gap between pathogenicity and degradation functions.