Three regimes of bacterial adhesion to substratum surfaces that dictate the bacterial response to a surface.

<p>1) In the planktonic regime, adhesion forces are extremely weak as on polymer-brush coatings, and bacteria do not realize they are on a surface. Weakly adhering bacteria are mainly live (green fluorescence). This regime is called “planktonic”, because bacteria do not adapt their planktonic phenotype despite their adhering state. 2) In the “interaction” regime, bacterial responses to their adhering state increase with increasing adhesion forces, for instance by the production of EPS (blue fluorescence), encasing themselves in a protective biofilm. 3) In the “lethal regime”, strong adhesion forces, as occurring on positively charged surfaces, cause membrane deformation that causes stress de-activation of the adhering bacteria, leading to reduced growth and cell death (red fluorescence). The confocal laser scanning micrographs represent biofilms in all three regimes of adhesion forces in which bacteria were stained with <i>Bac</i>light LIVE/DEAD stain, rendering live bacteria green and membrane damaged or dead bacteria red. EPS was stained with calcofluor white, rendering blue fluorescence.</p

Summary of microbial strains for which clonal subpopulations expressing phenotypes with different cell surface properties have been found.

<p>Summary of microbial strains for which clonal subpopulations expressing phenotypes with different cell surface properties have been found.</p

Phagocytosis rate <i>versus</i> the interfacial free energy of adhesion.

<p>(A) S. epidermidis 3399, (B) S. epidermidis 7391, (C) S. epidermidis 1457, (D) <i>S. aureus</i> ATCC 12600^GFP, (E) <i>S. aureus</i> 7323, and (F) <i>S. aureus</i> LAC. Note that phagocytosis rates increase when the interfacial free energy of adhesion becomes more favorable (more negative), but phagocytosis is not ruled out by unfavorable surface thermodynamic conditions (shaded regions). Dashed lines indicate the best-fit to a linear function through the data.</p

Contact angles of water (θ_w), formamide (θ_f), methyleniodide (θ_m) and α-bromonaphthalene (θ_b) measured on lawns of the staphylococcal strains and phagocytic cell lines involved in this study(in degrees).

<p>Contact angles of water (θ_w), formamide (θ_f), methyleniodide (θ_m) and α-bromonaphthalene (θ_b) measured on lawns of the staphylococcal strains and phagocytic cell lines involved in this study(in degrees).</p

Lifshitz-Van der Waals and acid-base components of interfacial free energy of adhesion (ΔG^LW_plb and ΔG^AB_plb, respectively) between bacteria and phagocytes, calculated from measured contact angles with liquids, as presented in Table 2 (mJ/m²).

<p>Lifshitz-Van der Waals and acid-base components of interfacial free energy of adhesion (ΔG^LW_plb and ΔG^AB_plb, respectively) between bacteria and phagocytes, calculated from measured contact angles with liquids, as presented in <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0070046#pone-0070046-t002" target="_blank">Table 2</a> (mJ/m²).</p

Phagocytosis rates for six staphylococcal strains by different phagocytic cell lines (cm²/min).

<p>Phagocytosis rates for six staphylococcal strains by different phagocytic cell lines (cm²/min).</p

Comparison of direct <i>versus</i> indirect quantification of staphylococcal phagocytosis.

<p>(A) staphylococcal adhesion for 1 h to a density of approximately 1.2×10⁶ bacteria/cm² and (B) staphylococcal adhesion for 3.5 h to a density of approximately 8×10⁶ bacteria/cm². The line indicates complete correspondence between both methods. Error bars represent the standard deviations over three replicates, with separately cultured bacteria and phagocytes.</p

Direct quantification of <i>S. aureus</i> ATCC12600^GFP inside phagocytes using CLSM.

<p> (A) CLSM snapshot of <i>S. aureus</i> ATCC 12600^GFP (modified to express GFP) inside J774A.1 macrophages stained with TRITC-phalloidin and (B) reconstruction of 3D image from CLSM sections using Bitplane’s Imaris software. Note that bacteria appear green fluorescent, while the cell wall of the phagocytes is red. Bar denotes 20 µm.</p

Maximal adhesion forces as a function of surface delay.

<p>Maximal adhesion forces, obtained using the LMM on the measured data, as a function of the surface delay time for the three strains of identical staphylococcal pairs involved in this study, with their 95% confidence intervals indicated by the dotted lines.</p

Maximal adhesion force differences between L-S and S-S pairs as a function of surface delay.

<p>Differences between the maximal adhesion forces for mixed pairs of staphylococci and lactobacilli pairs (L-S) and the corresponding identical staphylococcal pairs (S-S) as a function of the surface delay time, together with their 95% confidence intervals indicated by the dotted lines. Positive values indicate stronger adhesion forces between identical S-S pairs than between mixed L-S pairs. Significant differences (confidence interval not including the zero line) from the corresponding S-S pair at individual time points are indicated by an asterisk (*).</p