Fig. 1: Chemotaxis of P. aeruginosa PAO1 to AI-2 requires the chemoreceptors PctA and TlpQ.
From: Sensing of autoinducer-2 by functionally distinct receptors in prokaryotes
a A diagram of AI-2 biosynthesis by LuxS6,7. The borated AI-2 signal S-THMF-borate is recognized by the receptor LuxP in Vibrio spp.6, whereas the nonborated R-THMF binds to the receptor LsrB found in enteric bacteria and some other microorganisms belonging to the Rhizobiaceae, Bacillaceae and Clostridiaceae families7,8,9,10,11,12,13. b Plate gradient chemotaxis of P. aeruginosa. 10 μl aliquots of DPD/AI-2 (100 μM) were spotted onto M9 plates containing 2.5 mM glucose and 0.25% (w/v) Bacto agar and 2 μl aliquots of P. aeruginosa cultures with an OD600 of 0.6 in M9 medium were placed at 2 cm distance from the DPD/AI-2 spots. The distance from the site of inoculation to the colony edges closest to (D1) and furthest from (D2) the DPD/AI-2 spot was measured and the response index (RI) was calculated as follows: RI = D1/(D1 + D2). Data shown are one representative of five independent experiments with similar results (RI values are presented as mean ± s.d.; n = 5 independent experiments). c Quantitative capillary chemotaxis induced by AI-2. 230 μl aliquots of P. aeruginosa PAO1 with an OD600 of 0.1 in chemotaxis buffer were placed into the wells of a 96-well plate and capillaries filled with chemotaxis buffer or different concentrations of DPD/AI-2 solutions (0.01-1000 μM) were immersed into bacterial suspensions for 30 min. Serial dilutions of the contents from the capillaries were plated on LB agar plates and the CFU were determined. Cell numbers were corrected by subtracting the number of cells that have swum into the buffer-containing capillaries. d Optimal response to AI-2 requires PctA or TlpQ. Chemotactic responses of the wild-type (WT) PAO1 and 26 mutants to 100 μM DPD/AI-2 were measured by the quantitative capillary chemotaxis assay as described in (c). e PctA and TlpQ are required for chemotaxis induced by AI-2. The indicated strains were measured for quantitative capillary chemotaxis as described in (c). Complementation genes were expressed from derivatives of pME6032. c–e Statistical analyses were carried out by results from five independent experiments, each experiment having three technical replicates. Similar results were obtained in five independent experiments and data are presented as mean ± s.e.m. Two-sided, unpaired Student’s t-test was used for these analyses, and p values < 0.05 were considered to indicate statistically significant differences.
