Hydrocarbon-Degrading Sphingomonads: Sphingomonas, Sphingobium, Novosphingobium, and Sphingopyxis

Hydrocarbon-degrading members of the Sphingomonadaceae (Sphingomonas, Sphingobium, Novosphingobium, and Sphingopyxis) are common gram-negative, aerobic organisms that have been isolated from a wide variety of environments, including temperate and polar soils, marine sediments, and plant tissues where they occur as endophytes. They degrade a broad range of monoand polycyclic aromatic compounds, and the genetics and enzymology of these processes have been elucidated in some detail. In sphingomonads the biodegradation gene loci are often widely distributed on the genome and not co-localized as in other hydrocarbon-degrading genera, which has hindered genetic manipulation, but they are nonetheless potent candidates for bioremediation applications. Sphingomonad strains are easily cultivable, but recent results suggest that their role in degradation of recalcitrant aromatics in contaminated soils in situ may be less than previously thought.