title: Transcription factor levels enable metabolic diversification of single cells of environmental bacteria.
abstract: Transcriptional noise is a necessary consequence of the molecular events that drive gene expression in prokaryotes. However, some environmental microorganisms that inhabit polluted sites, for example, the m-xylene degrading soil bacterium Pseudomonas putida mt-2 seem to have co-opted evolutionarily such a noise for deploying a metabolic diversification strategy that allows a cautious exploration of new chemical landscapes. We have examined this phenomenon under the light of deterministic and stochastic models for activation of the main promoter of the master m-xylene responsive promoter of the system (Pu) by its cognate transcriptional factor (XylR). These analyses consider the role of co-factors for Pu activation and determinants of xylR mRNA translation. The model traces the onset and eventual disappearance of the bimodal distribution of Pu activity along time to the growth-phase dependent abundance of XylR itself, that is, very low in exponentially growing cells and high in stationary. This tenet was validated by examining the behaviour of a Pu-GFP fusion in a P. putida strain in which xylR expression was engineered under the control of an IPTG-inducible system. This work shows how a relatively simple regulatory scenario (for example, growth-phase dependent expression of a limiting transcription factor) originates a regime of phenotypic diversity likely to be advantageous in competitive environmental settings.
authors.affiliation: Department of Condensed Matter Physics and Materials Science Institute 'Nicolás Cabrera', Facultad de Ciencias, Universidad Autónoma de Madrid, Madrid, Cantoblanco, Spain.|Condensed Matter Physics Center (IFIMAC), Universidad Autónoma de Madrid, Madrid, Spain.
authors.forename: Raúl
authors.initials: R
authors.lastname: Guantes
authors.affiliation: Systems Biology Program, Centro Nacional de Biotecnología CSIC, Madrid, Cantoblanco, Spain.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Benedetti
authors.affiliation: Systems Biology Program, Centro Nacional de Biotecnología CSIC, Madrid, Cantoblanco, Spain.
authors.forename: Rafael
authors.initials: R
authors.lastname: Silva-Rocha
authors.affiliation: Systems Biology Program, Centro Nacional de Biotecnología CSIC, Madrid, Cantoblanco, Spain.
authors.forename: Víctor
authors.initials: V
authors.lastname: de Lorenzo
mesh_terms: D015964:Gene Expression Regulation, Bacterial; D053858:Metabolic Networks and Pathways; D008660:Metabolism; D011401:Promoter Regions, Genetic; D016958:Pseudomonas putida / Q000235:genetics* / Q000378:metabolism*; D012988:Soil Microbiology; D013269:Stochastic Processes; D014157:Transcription Factors / Q000378:metabolism; D014992:Xylenes / Q000378:metabolism*
chemical_list: D014157:Transcription Factors; D014992:Xylenes; C031285:3-xylene