The type IV pilus chemoreceptor PilJ controls chemotaxis of one bacterial species towards another
Fig 2
Methyl modification proteins for chemotaxis adaptation are necessary for full directional TFP-mediated motility towards S. aureus.
(A) Schematic of P. aeruginosa MCP protein PilJ and methyl modification proteins PilK and ChpB. The predicted methylation sites with cytoplasmic domain of PilJ are represented by the black and gray circles. In wild type, PilJ is predicted to undergo methylation and demethylation; thus, ChpA kinase activity shifts between more ON or OFF states (left). In the absence of chpB, PilJ is expected to have high methylation (filled, black circles), and, therefore, ChpA kinase activity shifted ON (middle). In the absence of pilK, PilJ is expected to have low methylation (empty, gray circles), and, therefore, ChpA kinase activity shifted OFF (right). For each analysis in B-D, an annotated schematic is shown in the leftmost column, followed by (left-to-right) P. aeruginosa WT, ΔchpB, and ΔpilK in coculture with S. aureus. (B) Rose graphs of the principal angle of motility for each cell trajectory relative to starting position. Position of S. aureus relative to the center of the P. aeruginosa microcolony is represented by the gray cocci on the perimeter. Trajectory angles are shown by colored vectors with the average angle of all trajectories, which determines the parallel positive direction (||+), represented by the dotted black line. Longer, darker vectors indicate more cells for the given principal angle. One rose graph representative of at least 3 replicates is shown. (C) PDFs of step sizes (Δr) parallel to the direction of motion (||) of moving (M) wild type, ΔchpB, and ΔpilK cells. Each PDF is for a time step (lag time) of Δt = 40 seconds and exhibits a peak of highly probable sub-micron jiggling (green region). The blue and red regions highlight the nonzero sharp-shoulder peak step size in the backward (||−) and forward (||+) directions. (D) Peak displacements (μm) over various time steps for forward and backwards displacements in both parallel and perpendicular directions. The value for each plotted step size (red and blue triangles) at a given time step corresponds with the most probable displacement value in the respective relative distribution plots (graphs in C and S3 Fig), as shown in the schematic on the left. While all strains exhibit parallel and perpendicular motion, not all strains have sharp-shoulder peak values in each direction. The underlying data can be found in S2–S4 Data. IM, inner membrane; LBD, ligand binding domain; MCP, methyl-accepting chemotaxis protein; OM, outer membrane; PDF, probability density function; PG, peptidoglycan; TFP, type IV pilus; WT, wild type.