Identification of a malate chemoreceptor in Pseudomonas aeruginosa by screening for chemotaxis defects in an energy taxis-deficient mutant

Abstract

We found that a robust energy taxis response mediated by the Aer receptor can sometimes mask chemotaxis mediated by other methyl-accepting chemotaxis proteins (MCPs) in Pseudomonas aeruginosa. We identified PA2652 as a chemoreceptor for malate by screening aer mcp double mutants by using swarm plate assays.

FIG. 1.

Behavioral responses of P. aeruginosa PAO1 wild-type (WT), aer, aer pctB, and pctB strains as assayed in a mineral medium swarm plate that contained 1 mM glutamine as the sole carbon and energy source. Each quadrant of the plate was stab inoculated with a single colony, and the plate was incubated for 16 h at 37°C.

FIG. 2.

Behavioral responses of P. aeruginosa PAO1 wild-type (WT), aer, aer PA2652, and PA2652 mutant strains as assayed in a mineral medium swarm plate that contained 2 mM malate as the sole carbon and energy source. Each quadrant of the plate was stab inoculated with a single colony, and the plate was incubated for 16 h at 37°C.

FIG. 3.

The chemotactic responses of P. aeruginosa PAO1 (wild type) (▴) and of a PA2652 mutant (strain PTL41758) (▪) to various concentrations of malate in a capillary assay. The data are expressed as CFU and are the averages of six assays ± standard deviations.