New insights into the activation of o-xylene biodegradation in Pseudomonas stutzeri OX1 by pathway substrates

The regulation of the tou operon of Pseudomonas stutzeri OX1, for degradation of toluene and o-xylene via phenolic intermediates, has been faithfully reconstructed in vitro with purified proteins. The set-up included the prokaryotic enhancer-binding protein TouR, the σ(54)-dependent P(ToMO) promoter and the σ(54)-containing RNA polymerase. With this system we prove that direct binding of 2-methylphenol (o-cresol) to TouR is the only regulatory step for activation of P(ToMO) in response to aromatic effectors, thereby ruling out the involvement of other factors or a need for protein processing. In addition, we found that while TouR failed entirely to activate P(ToMO) in the absence of inducers, the protein had per se a very significant ATPase activity, which was only moderately increased by o-cresol addition. The results presented here support the view that TouR-like proteins are particularly suitable as evolutionary assets to endow recently evolved pathways for the degradation of environmental pollutants with an optimal degree of transcriptional regulation

Degradation of o 12xylene by Pseudomonas stutzeri OX1 (Pseudomonas sp. OX1)

Interest in the microbial degradation of methylbenzenes arose in the early 1970s, when both toxicological and ecological data started to alert people about their wide distribution in the environment and their effects on living organisms. Most of the early studies on bacterial methylbenzene catabolism focused on bacteria belonging to the genus Pseudomonas, which proved to be endowed with a formidable metabolic versatility. Several Pseudomonas strains isolated then for their ability to degrade toluene, mand p-xylene, and 1,2,4-trimethylbenzene, later become the archetypes for the studies on the biochemistry, genetics and regulation of methylbenzene degradation (see also volume 2, Chapter 18 and volume 4, Chapter 7)