Figure 1.
(A) FCM scattering plot and corresponding bright field microscope images of a COO– particle sample washed in water and suspended in PBS. 80% of events were concentrated in the scattering value region R1 corresponding to a monodispersed, 10-μm-diameter population. Outliers corresponded to a population of slightly larger particles and a few doublets. Cationic (NH3+) particles displayed the same scattering characteristics as anionic (COO–) particles.
(B) Microscopic images of PYR- (2nd column) and PI- (3rd column) labeled cationic (1st row) and anionic (2nd row) particles. Dye concentration equal to 16.7 nM.
Figure 2.
Scattering (A) and fluorescence dot plots of all GFP-labeled (B), all non GFP-labeled cells (C) and a mixture (50/50) of both (D). Aliquots of exponentially growing cultures were diluted in PBS to obtain a 5 × 106 cells/ml suspension.
(E) FL1 dot plots of a slightly aggregated cell population (Rflag, right plot); in this case, 3% of the objects are considered aggregates.
Figure 3.
Bacterial Adhesion in Colloidal Suspension
(A) Microscope images of MG1655gfp E. coli cells and particles brought into contact with particles in M63B1 medium for 20 min. Bright-field and bright-field fluorescence combined images are shown. Adhesive events can be observed on the combined image; examples are indicated by white arrows.
(B) Corresponding fluorescence dot plots are shown for particles alone (left) and cells and particles brought into contact for 20 min (right). Gate R2 corresponds to bare particles, whereas gate R3 corresponds to colonized particles.
Figure 4.
Effect of Curli Production on Early Surface Adhesion
Adhesion kinetic curves of MG1655gfpompR234 (A) and MG1655gfpΔcsgA (B). Particles and cells were brought into contact at time t = 0. Cell to particle ratio was around 200 and particle concentration equal to 6 × 106/ml.
(C) Colonized particle fraction kinetics are shown for two sequential additions of fresh NH3+ particles to MG1655gfpompR234 cells. 50 μl of stock particles were added to a cell/particle sample after 9 min incubation once the first colonization phase leveled off.
(D) Charge inversion of NH3+ particle during surface colonization. FL3 intensity in time due to PI adsorption (2 × 10−8 M) is shown for MG1655gfpompR234 (▴) and MG1655gfpΔcsgA (•).
(E) Bright field and fluorescence microscope images of MG1655gfpompR234 engaged in second-phase colonization of NH3+ particles.
Figure 5.
Self-Association of Free-Floating Cells and Cooperative Effects in Curli-Producing Bacteria
Bacteria (left) and colloid (right) dot plots of MG1655gfpompR234 brought into contact with NH3+ particles before (A) and after (B) second colonization phase onset. (C) Number of events comprised in the Rflag gate in the presence (black diamond) or absence (gray diamond) of particles. Cells were taken from a culture (DO = 0.5) and resuspended by pipetting in an adequate volume of buffer at time t = 0. (D) Time dependence of cooperative index, λ, during MG1655gfpompR234 colonization.
Figure 6.
Aggregation and Surface Colonization Kinetics of Cells Expressing Different Cell Surface Adhesins
Ag43 (A and B); F-pili (C and D) were examined under the same conditions as in Figure 4. (black circles) corresponds to cells producing indicated surface adhesin and (gray circles) to cells not producing surface adhesin. (E) Cooperative index in time for F pili–expressing cell colonization of NH3+ particles.