Research ArticleBIOPHYSICS

Surface waves control bacterial attachment and formation of biofilms in thin layers

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Science Advances  27 May 2020:
Vol. 6, no. 22, eaaz9386
DOI: 10.1126/sciadv.aaz9386
  • Fig. 1 Patterns of waves and biofilms produced by E. coli (ATCC 25966) bacteria at different accelerations.

    (A to D) Contour plots of the measured instantaneous surface elevation. Red and blue colors correspond to peaks/troughs of the waves. (E to H) Corresponding images of the CV stain of the biofilm attached to the bottom of the microplate after exposure of the bacterial suspension to the waves for 24 hours. Darker colors correspond to thicker biofilms. Microplates are vibrated at fs = 120 Hz at the vertical accelerations of (left to right) a = 2g, 3g, 5g, and 7g.

  • Fig. 2 Location of biofilms at the vertical acceleration of 2g.

    (A) Profiles of the surface elevation produced by the Faraday wave (a = 2g) at two time instants t0 and t0 = t + T/2 (where T is the wave period), and (B) corresponding profile of a CV intensity (approximately proportional to the biofilm thickness). a.u., arbitrary units. (C) Schematic of the fluid motion under a standing surface wave (41). Blue areas at the bottom indicate the locations of the biofilm growth.

  • Fig. 3 Biofilm production.

    The bacterial suspensions are vibrated for 24 hours and then incubated for another 24 hours at 37°C. (A) Total mass of the biofilms (measured as the normalized absorption or the OD of the CV stain at 550 nm) generated in a microplate well (35 mm diameter) at four different vertical accelerations (the vibration frequency is 120 Hz) (violet bars). The OD of the bacterial suspension (measured at 600 nm) is about the same in all experiments (orange bars). Measurements are performed six times with three repeats each at every vertical acceleration. The OD is normalized by the OD of the control (no-shaken) samples. The error bars show the SD of the measurements. (B) Fluorescent image of the biofilm formed in a well exposed to vibration at the vertical acceleration of 3g. Lighter colors correspond to thicker biofilm. (C and D) Reconstructed 3D surface of the biofilm using the CLSM at two regions of interest (200 × 200 μm) indicated by the red boxes in (B).

  • Fig. 4 Oscillon statistics.

    (A) Illustration of the identification of the oscillons as the local maxima in the measured wave field at 5g. (B) MSD of the oscillons at different vertical accelerations. (C to E) Trajectories of the oscillons tracked over 0.4 s (24 wave periods) at different vertical accelerations (left to right): 3g, 5g, and 7g.

  • Fig. 5 Sedimentation of passive particles and bacteria.

    (A) Image of the sedimentation of inactive E. coli bacteria at the vertical acceleration of 2g. (B) Image of the sedimentation of polyamid particles (0.005 mm diameter, specific density of 1.03) at the vertical acceleration of 2g. (C) Schematic of the streaming pattern under the standing surface waves (32). Blue and gray areas at the bottom indicate the locations of the biofilm growth and of the sedimentation of passive particles, respectively. (D to G) Sedimentation pattern of the titanium dioxide powder (0.0004 mm diameter, specific density of 3.0) at different vertical accelerations: 2g, 3g, 5g, and 7g. (H) Corresponding MSD of the sedimentation patterns at different vertical accelerations.

  • Fig. 6 Biofilm formation and wave parameters.

    (A) Amplitude of the surface elevation (red solid line) and the inverse of the diffusion coefficient of the oscillons (green dashed line), and (B) the total mass of attached biofilm, as a function of the vertical acceleration.

Supplementary Materials

  • Supplementary Materials

    Surface waves control bacterial attachment and formation of biofilms in thin layers

    Sung-Ha Hong, Jean-Baptiste Gorce, Horst Punzmann, Nicolas Francois, Michael Shats, Hua Xia

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