title: The expression of many chemoreceptor genes depends on the cognate chemoeffector as well as on the growth medium and phase.
abstract: Chemoreceptor-based signaling is a major bacterial signal transduction mechanism. Escherichia coli, the traditional model, has five chemoreceptors. Recent genome analyses have shown that many bacteria have a much higher number of chemoreceptors. Pseudomonas putida KT2440 is an alternative model that has 27 chemoreceptors and the cognate chemoeffector is known for many of them. Here, we address the question whether and which factors modulate chemoreceptor gene expression. We report reverse transcriptase quantitative PCR measurements of all KT2440 chemoreceptor genes. Transcript levels of individual chemoreceptors differed largely, namely up to 174-fold between the most and least abundant. The cognate chemoeffectors had three different effects on the expression of their chemoreceptor genes. In some cases, the respective chemoeffectors, shown previously to be C- and/or N-sources, induced the expression. In contrast, for the two inorganic phosphate sensing chemoreceptors, the chemoeffector caused dramatic reduction in expression. For four other receptors, including the three TCA cycle intermediate sensing receptors, the chemoeffector did not cause any significant alterations. In addition, a significant number of receptors were induced in minimal growth medium and in the stationary phase. We show here that environmental cues determine largely chemoreceptor expression. This work will serve as reference for analogous studies in other bacteria.
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, C/Prof. Albareda, 1, 18008, Granada, Spain.
authors.forename: Diana
authors.initials: D
authors.lastname: López-Farfán
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, C/Prof. Albareda, 1, 18008, Granada, Spain.
authors.forename: José Antonio
authors.initials: JA
authors.lastname: Reyes-Darias
authors.affiliation: Department of Environmental Protection, Estación Experimental del Zaidín, Consejo Superior de Investigaciones Científicas, C/Prof. Albareda, 1, 18008, Granada, Spain. tino.krell@eez.csic.es.
authors.forename: Tino
authors.identifier: http://orcid.org/0000-0002-9040-3166
authors.initials: T
authors.lastname: Krell
mesh_terms: D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics*; D002633:Chemotaxis / Q000235:genetics*; D004926:Escherichia coli / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D016680:Genome, Bacterial; D016958:Pseudomonas putida / Q000235:genetics*; D015398:Signal Transduction / Q000235:genetics
chemical_list: D001426:Bacterial Proteins
keywords: Chemoreceptor; Chemosensory pathway; Chemotaxis; Gene expression; Pseudomonas