Genetics of Accessing and Exploiting Hydrocarbons

Hydrocarbons abound in the environment and microorganisms are often capable of assimilating and degrading these normally recalcitrant molecules. In order to achieve this, bacteria have developed specific adaptive mechanisms; much of the adaptive response is brought about by transcriptional activation of genes and is controlled by one or two component regulatory systems, global regulators and DNA binding proteins. The expressed gene products are then able to degrade the molecules and often take advantage of the stored energy imparted by the physicochemical properties of the hydrocarbon structure. The response of gene regulators to the presence of hydrocarbons such as toluene in the environment allows initiation or inhibition of transcription, so that the rate of synthesis of metabolically important gene products is adaptively modified. Microorganisms which mount the most appropriate physiological adaptation are then able to proliferate in the changing environment. Here we give a comprehensive overview of adaptive regulation of the TOD and TOL pathways including the involvement of catabolite repression.