Figure 1.
Focal adhesion in HeLa cells without vs. with EHEC infection.
Representative confocal micrographs of HeLa cells (A) without- and (C) with- EHEC infection; vinculin was detected by indirect immunofluorescence. The images of focal adhesion were segmented by setting an intensity threshold via MetaMorph software to calculate the fractional area of focal adhesion, as shown in (B) for HeLa cells without-, and (D) with- EHEC infection.
Figure 2.
Focal adhesion number and size in HeLa cells without vs. with EHEC infection.
(A) Number of focal adhesions as a function of their area. The mean values and standard deviations are indicated by the height of the thick bars and the thin lines, respectively. (B) Fraction of cell area occupied by focal adhesions. The symbol “⋄” and the horizontal bar inside each box represent the mean and the median values, respectively; and the lower and the upper sides of each box represent the values at the first and the third quartiles, respectively. *: p<0.05; **: p<0.001; data obtained from N = 15 cells.
Figure 3.
Immunofluorescence microscopy images of the apical region of HeLa cells without vs. with EHEC infection.
(A) HeLa cells without EHEC infection; (B) HeLa cells, after being infected with EHEC for 6 hours. HeLa cells were fixed, permeated and stained: green, FITC-label phalloidin for actin; blue, rabbit anti-O157 and Alexa Fluor 405-goat anti-rabbit IgG for EHEC. The merged images in turquoise represent the EHEC induced pedestal formation.
Figure 4.
Confocal micrographs of actin filaments, FITC-labeled phalloidin (green), in the basal region of (A) HeLa cells without EHEC infection; (B) HeLa cells after infected by EHEC for 6 hours.
The formation of the stress fibers in the basal region of HeLa cells after EHEC infection can be clearly observed in (B).
Figure 5.
The F-actin orientation in the basal region of HeLa cells (A to D) without, and (E to H) with EHEC infection.
Cells fixed and stained with FITC-phalloidin (green) for F-actin, imaged in HeLa cells (A) without, (E) with EHEC infection. In (B) and (F), the images of actin fibers with fluorescence intensity above a selected threshold are marked and color-coded to represent their angular orientation in radians (1 radian≈57.3 degrees). The direction along the principal axis (i.e., the direction along which the maximum number of actin filaments were aligned) is denoted as 0; (B) without, and (F) with EHEC infection. The angular plots corresponding to (B) and (F) are shown respectively in panels (C) and (G), in degrees. Similar data compiled from from 15 cells are shown in (D) and (H), respectively. The orientation distributions without and with EHEC infection are statistically significant (p<0.001, Watson's U2 test). Variance and Kurtosis of the angular distributions are given in Table 1.
Table 1.
Variance and Kurtosis of the angular distribution of stress fiber orientation shown in Fig. 6.
Figure 6.
The principal value of the mean squared displacement (PMSD) as a function of the time lag (τ).
In each diagram, the upper curve represents the result for the soft axis, and the lower curve for the stiff axis. (A) Apical region (deduced from 112 particles) of HeLa cells without EHEC infection; (B) basal region of HeLa cells without EHEC infection (deduced from 158 particles); (C) apical region of EHEC-infected HeLa cells (deduced from 66 particles); (D) basal region of EHEC-infected HeLa cells (deduced from 55 particles). The straight lines represent the power law dependence; the symbols represent the mean value of the experimental results. The vertical bars around each point represent the corresponding standard deviation.
Figure 7.
Angular distribution of the direction of maximum mean squared displacement (soft direction), θMSD,max, in the apical and the basal regions of HeLa cells without vs. with EHEC infection.
(A) Apical region of HeLa cells without EHEC infection (data deduced from 112 particles; (B) basal region of HeLa cells without EHEC infection (data deduced from 158 particles); (C) apical region of EHEC-infected HeLa cells (data deduced from 66 particles); (D) basal region of EHEC-infected HeLa cells (data deduced from 55 particles). Statistically significant differences (obtained from Watson's U2 test for angular distributions) were found between apical and basal regions of EHEC-infected cells (**, p<0.01), and between basal regions of non-infected and EHEC-infected cells (*, p<0.05). Variance and kurtosis of the angular distributions of θMSD,max are given in Table 2.
Table 2.
Variance and Kurtosis of the angular distribution of the direction of normalized maximum MSD, θMSD,max, at the apical and the basal regions of HeLa cells with and without EHEC infection.
Figure 8.
Boxplot of intracellular elastic shear modulus G′ and viscous shear modulus G″ (at 10 Hz) of HeLa cells without vs. with EHEC infection.
Left: along the soft axis, and Right: along the stiff axis; (A) the apical region, and (B) the basal region. *: p<0.05; **: p<0.001. The symbol “⋄” and the horizontal bar inside each box represent the mean and the median values, respectively; and the lower and the upper sides of each box represent the values at the first and the third quartiles, respectively.
Table 3.
The mean and the standard error of the mean (SEM) of the elastic shear modulus (G′) and viscous shear modulus (G″) at 10 Hz in the apical region of HeLa cells without vs. with EHEC infection.
Table 4.
The mean and the standard error of the mean (SEM) of the elastic shear modulus (G′) and viscous shear modulus (G″) at 10 Hz in the basal region of HeLa cells without vs. with EHEC infection.
Table 5.
The ratio of viscoelastic shear moduli in the stiff direction and the corresponding values in the soft direction for HeLa cells without vs. with EHEC infection.