Chapter 12 Regulation of toluene catabolic pathways and toluene efflux pump expression in bacteria of the genus Pseudomonas

Abstract

All Pseudomonas strains that use toluene as a carbon source have a series of mechanisms that allow them to cope with the stress imposed by toluene itself. Nonetheless, most Pseudomonas strains are highly sensitive to aromatic hydrocarbons such as toluene, styrene, or p-xylene; however, independent laboratories have isolated Pseudomonas putida strains tolerant to these toxic compounds. This chapter reviews the regulatory networks controlling the expression of the different pathways and the mechanisms developed to regulate toluene efflux pumps. A common feature to all toluene pathways from different bacteria is that the genes involved in the different reactions are organized as operons, which are either independent for the different segments of the pathways (i.e., the TOL pathway) or transcribed as a single unit (i.e. the tod operon). In all cases, these pathways are under the control of regulatory mechanisms, which are ultimately modulated by toluene or intermediate substrates.