The expression of many chemoreceptor genes depends on the cognate chemoeffector as well as on the growth medium and phase.

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.

Two different mechanisms mediate chemotaxis to inorganic phosphate in Pseudomonas aeruginosa.

Inorganic phosphate (Pi) is a central signaling molecule that modulates virulence in various pathogens. In Pseudomonas aeruginosa, low Pi concentrations induce transcriptional alterations that increase virulence. Also, under low Pi levels, P.

McpQ is a specific citrate chemoreceptor that responds preferentially to citrate/metal ion complexes.

Chemoreceptors are at the beginning of chemosensory pathways that mediate chemotaxis. Pseudomonas putida KT2440 is predicted to have 27 chemoreceptors, most of which uncharacterized. We have previously identified McpS as chemoreceptor for Krebs cycle intermediates.

Identification of a Chemoreceptor for C2 and C3 Carboxylic Acids.

Chemoreceptors are at the beginnings of chemosensory signaling cascades that mediate chemotaxis. Most bacterial chemoreceptors are functionally unannotated and are characterized by a diversity in the structure of their ligand binding domains (LBDs). The data available indicate that there are two major chemoreceptor families at the functional level, namely, those that respond to amino acids or to Krebs cycle intermediates.

Specific gamma-aminobutyrate chemotaxis in pseudomonads with different lifestyle.

The PctC chemoreceptor of Pseudomonas aeruginosa mediates chemotaxis with high specificity to gamma-aminobutyric acid (GABA). This compound is present everywhere in nature and has multiple functions, including being a human neurotransmitter or plant signaling compound. Because P.

Characterization of molecular interactions using isothermal titration calorimetry.

Isothermal titration calorimetry (ITC) is based on a simple titration of one ligand with another and the small heat changes caused by the molecular interaction are detected. From one ITC experiment the complete set of thermodynamic parameters of binding including association and dissociation constants as well as changes in enthalpy, entropy, and free energy can be derived. Using this technique almost any type of molecular interaction can be analyzed.

Qualitative and quantitative assays for flagellum-mediated chemotaxis.

A primary driving force during bacterial evolution was the capacity to access compounds necessary for growth and survival. Since the species of the genus Pseudomonas are characterized by metabolic versatility, these bacteria have developed chemotactic behaviors towards a wide range of different compounds. The specificity of a chemotactic response is determined by the chemoreceptor, which is at the beginning of the signaling cascade and to which chemoattractants and chemorepellents bind.

High specificity in CheR methyltransferase function: CheR2 of Pseudomonas putida is essential for chemotaxis, whereas CheR1 is involved in biofilm formation.

Chemosensory pathways are a major signal transduction mechanism in bacteria. CheR methyltransferases catalyze the methylation of the cytosolic signaling domain of chemoreceptors and are among the core proteins of chemosensory cascades. These enzymes have primarily been studied Escherichia coli and Salmonella typhimurium, which possess a single CheR involved in chemotaxis.

Evidence for chemoreceptors with bimodular ligand-binding regions harboring two signal-binding sites.

Chemoreceptor-based signaling is a central mechanism in bacterial signal transduction. Receptors are classified according to the size of their ligand-binding region. The well-studied cluster I proteins have a 100- to 150-residue ligand-binding region that contains a single site for chemoattractant recognition.

Bioavailability of pollutants and chemotaxis.

The exposure of bacteria to pollutants induces frequently chemoattraction or chemorepellent reactions. Recent research suggests that the capacity to degrade a toxic compound has co-evolved in some bacteria with the capacity to chemotactically react to it. There is an increasing amount of data which show that chemoattraction to biodegradable pollutants increases their bioavailability which translates into an enhancement of the biodegradation rate.

Bacterial chemotaxis towards aromatic hydrocarbons in Pseudomonas.

Bacterial chemotaxis is an adaptive behaviour, which requires sophisticated information-processing capabilities that cause motile bacteria to either move towards or flee from chemicals. Pseudomonas putida DOT-T1E exhibits the capability to move towards different aromatic hydrocarbons present at a wide range of concentrations. The chemotactic response is mediated by the McpT chemoreceptor encoded by the pGRT1 megaplasmid.

Diversity at its best: bacterial taxis.

Bacterial taxis is one of the most investigated signal transduction mechanisms. Studies of taxis have primarily used Escherichia coli and Salmonella as model organism. However, more recent studies of other bacterial species revealed a significant diversity in the chemotaxis mechanisms which are reviewed here.