The Cellular Abundance of Chemoreceptors, Chemosensory Signaling Proteins, Sensor Histidine Kinases, and Solute Binding Proteins of Pseudomonas aeruginosa Provides Insight into Sensory Preferences and Signaling Mechanisms

Abstract

Chemosensory pathways and two-component systems are important bacterial signal transduction systems. In the human pathogen Pseudomonas aeruginosa, these systems control many virulence traits. Previous studies showed that inorganic phosphate (Pi) deficiency induces virulence. We report here the abundance of chemosensory and two-component signaling proteins of P. aeruginosa grown in Pi deficient and sufficient media. The cellular abundance of chemoreceptors differed greatly, since a 2400-fold difference between the most and least abundant receptors was observed. For many chemoreceptors, their amount varied with the growth condition. The amount of chemoreceptors did not correlate with the magnitude of chemotaxis to their cognate chemoeffectors. Of the four chemosensory pathways, proteins of the Che chemotaxis pathway were most abundant and showed little variation in different growth conditions. The abundance of chemoreceptors and solute binding proteins indicates a sensing preference for amino acids and polyamines. There was an excess of response regulators over sensor histidine kinases in two-component systems. In contrast, ratios of the response regulators CheY and CheB to the histidine kinase CheA of the Che pathway were all below 1, indicative of different signaling mechanisms. This study will serve as a reference for exploring sensing preferences and signaling mechanisms of other bacteria.

Sensing preferences for prokaryotic solute binding protein families

“…We have recently published the SBP repertoire of 49 bacterial model strains that possess on average 60 ± 49 SBP genes, which frequently represent several percent of their genomes (Ortega et al, 2022 ). In addition, a proteomics study has shown that the cellular level of many SBPs is very high (Matilla et al, 2023 ).…”

Exploring solute binding proteins in Pseudomonas aeruginosa that bind to γ‐aminobutyrate and 5‐aminovalerate and their role in activating sensor kinases

“…Of the 93 SBPs, 62 SBPs were detected and quantified in a proteomics study. Among these proteins was only one of the three GABA‐responsive SBPs (PA0602) (Matilla et al, 2023b ), whereas the remaining two proteins are likely to be present at levels below the mass spectrometric detection limit, indicating that the functional redundancy of genes does not necessarily translate into a redundancy of proteins.…”

“…SBPs were shown to bind a wide range of ligands including amino‐ and organic acids, peptides, sugars, polyamines, quaternary amines, purines, metal ions, oxoanions, vitamins, quorum sensing signals and different siderophores (Cerna‐Vargas et al, 2023 ). In addition, a proteomics study has shown that the cellular levels of many SBPs are very high and generally superior to receptor levels (Matilla et al, 2023b ). The high number of SBP genes and their elevated cellular levels reflect their physiological importance.…”