Research ArticleBIOPHYSICS

A molecular rack and pinion actuates a cell-surface adhesin and enables bacterial gliding motility

See allHide authors and affiliations

Science Advances  04 Mar 2020:
Vol. 6, no. 10, eaay6616
DOI: 10.1126/sciadv.aay6616
  • Fig. 1 The axis of rotation is found near a GldL spot.

    (A) One tethered cell with five GldL foci is shown, with one foci numbered 5 close to the axis of rotation; we call it the “nearest neighbor” GldL. The other foci execute circular arcs, as the cell rotates. The foci were spaced about 1.4 μm apart. (B) The distribution of numbers of GldL foci per cell for 42 cells. About four GldL foci appeared per cylindrical face of a cell. (C) Distances of the GldL foci of the tethered cell shown in (A) from the axis of rotation plotted as a function of time.

  • Fig. 2 Analysis of the position of GldL spots.

    (A) A scatterplot of the positions of the nearest-neighbor GldL relative to the axis of rotation of eight tethered cells, with 60 frames on average imaged for each cell, resulting in 484 measurements. For each cell, the axis of rotation was normalized to be at the origin. (B) Frequency distribution of the distance of the nearest-neighbor GldL from the axis of rotation of eight tethered cells measured for a total of 484 image frames with about 60 image frames per cell. The peak of a Gaussian fit to this distribution is 109.7 nm with an SD of 68.47 nm.

  • Fig. 3 GldL localizes near the track on which SprB moves.

    (A) Colocalization of GldL (green circles) with the trajectory of SprB (blue dots and red line). GldL remains fixed relative to the cell. SprB moves along the trajectory shown in red. Blue dots mark the positions of SprB determined at different time points. Red lines are second-order polynomial fits to the blue dots. GldL was labeled with YFP and SprB with Cy3. The position of SprB and GldL-YFP from the same cell is determined from movie S4 and fig. S6B, respectively. The images were rotated and translated to determine the positions of SprB and GldL-YFP relative to the cell. (B) Frequency distribution of the distance of 42 motors from SprB trajectories for 10 cells, showing a peak at a distance of 90.9 nm with an SD of 63.7 nm. (C) A simulation in which 42 motors were localized at random on one cell, with the positions of the motors (green) and the track (red). (D) A frequency distribution of distances between the motors and the track.

  • Fig. 4 A model of the gliding machinery.

    (A) A cross-sectional view of a cell with a rotary gliding motor (blue), a mobile tread (green), a stationary track (red), and an adhesin (magenta). The rotary motor and the track are anchored to the peptidoglycan (PG), and the track is wound spirally around the cell. The rotary motor drives a pinion that engages a mobile tread (rack) that slides along the track. The adhesin, SprB, is attached to the tread and moves with it. The dimension d is the distance between the axis of rotation of the motor and the center of the track, and r is the radius of the pinion. OM, outer membrane; CM, cytoplasmic membrane. (B) A side view of a cell with a rotary motor powering the motion of a tread carrying SprB. See movie S5 for an animation of this model.

Supplementary Materials

  • Supplementary material for this article is available at http://advances.sciencemag.org/cgi/content/full/6/10/eaay6616/DC1

    Primers used in the study

    Computer scripts

    Fig. S1. A frequency distribution of nearest-neighbor distances between 42 GldL foci found on 10 cells.

    Fig. S2. Position of the nearest-neighbor GldL foci from the axis of rotation of eight tethered cells shown for the individual cells.

    Fig. S3. Rotation speed of a cell plotted as a function of time.

    Fig. S4. The rate for the “drop” in rotation speed after addition of CCCP (red linear regression fit) is four times faster than the rate of increase following removal of CCCP.

    Fig. S5. Speed of a smooth gliding cell measured by tracking the center of mass does not change after the addition of A22.

    Fig. S6. A cell with SprB-Cy3 and GldL-YFP labels.

    Fig. S7. Tracking the flips displayed by gliding cells.

    Movie S1. A phase-contrast image stack where GldL-YFP strain displays wild-type levels of rotation. Similar to sheared and tethered wild-type cells, two cells in the field of view display rotation. Other cells attach to glass and beads coated with anti-SprB antibody. Some cells and beads display motion over short distances.

    Movie S2. A tethered cell with five fluorescent GldL spots. The cell appears to rotate around a fixed axis.

    Movie S3. A phase-contrast image stack showing that addition of CCCP stops rotation of a tethered cell.

    Movie S4. A Cy3-tagged SprB moving along the length of a cell. For this movie, a filter that allows only Cy3 emission to pass was used.

    Movie S5. An animation of the model suggesting how a molecular rack and pinion could drive gliding. The pinion is blue, the tread is green, and the adhesin SprB is magenta.

    Movie S6. A cell gliding smoothly over a glass surface.

    Movie S7. A gliding cell displaying flips.

  • Supplementary Materials

    The PDF file includes:

    • Fig. S1. A frequency distribution of nearest-neighbor distances between 42 GldL foci found on 10 cells.
    • Fig. S2. Position of the nearest-neighbor GldL foci from the axis of rotation of eight tethered cells shown for the individual cells.
    • Fig. S3. Rotation speed of a cell plotted as a function of time.
    • Fig. S4. The rate for the “drop” in rotation speed after addition of CCCP (red linear regression fit) is four times faster than the rate of increase following removal of CCCP.
    • Fig. S5. Speed of a smooth gliding cell measured by tracking the center of mass does not change after the addition of A22.
    • Fig. S6. A cell with SprB-Cy3 and GldL-YFP labels.
    • Fig. S7. Tracking the flips displayed by gliding cells.
    • Primers used in the study
    • Computer scripts

    Download PDF

    Other Supplementary Material for this manuscript includes the following:

    • Movie S1 (.mov format). A phase-contrast image stack where GldL-YFP strain displays wild-type levels of rotation. Similar to sheared and tethered wild-type cells, two cells in the field of view display rotation. Other cells attach to glass and beads coated with anti-SprB antibody. Some cells and beads display motion over short distances.
    • Movie S2 (.mov format). A tethered cell with five fluorescent GldL spots. The cell appears to rotate around a fixed axis.
    • Movie S3 (.mov format). A phase-contrast image stack showing that addition of CCCP stops rotation of a tethered cell.
    • Movie S4 (.mov format). A Cy3-tagged SprB moving along the length of a cell. For this movie, a filter that allows only Cy3 emission to pass was used.
    • Movie S5 (.mov format). An animation of the model suggesting how a molecular rack and pinion could drive gliding. The pinion is blue, the tread is green, and the adhesin SprB is magenta.
    • Movie S6 (.mov format). A cell gliding smoothly over a glass surface.
    • Movie S7 (.mov format). A gliding cell displaying flips.

    Files in this Data Supplement:

Stay Connected to Science Advances

Navigate This Article