Aromatic hydrocarbon degradation by Sphingomonas yanoikuyae B1

Sphingomonas yanoikuyae B1 is able to grow on a wide variety of aromatic compounds including biphenyl, naphthalene, phenanthrene, toluene, m-, and p-xylene. In addition, the initial enzymes for degradation of biphenyl have the ability to metabolize a wide variety of different polycyclic aromatic hydrocarbons. The catabolic pathways for the degradation of both the monocyclic and polycyclic aromatic hydrocarbons are intertwined, joining together at the level of (methyl)benzoate and catechol. Both upper branches of the catabolic pathways are induced when S. yanoikuyae B1 is grown on either class of compound. An analysis of the genes involved in the degradation of these aromatic compounds reveals that at least six operons are involved. The genes are not arranged in discrete pathway units but are combined in groups with genes for the degradation of both classes of compounds in the same operon. Genes for multiple dioxygenases are present perhaps explaining the ability of S. yanoikuyae B1 to grow on a wide variety of aromatic compounds. Received 10 August 1997/ Accepted in revised form 15 August 1997