Auto-aggregation capacities of <i>L</i>. <i>casei</i> BL23 wt and <i>srtA2</i> strains.

<p>Strains were grown in UF milk medium for 48 h at 37°C. Auto-aggregation was evaluated by spectrophotometry (600 nm) and expressed as the auto-aggregation percentage. Cell suspension OD after growth (48 h) and homogenization was used as a reference (100%). Data are presented as means ± standard deviations. Each experiment was done in triplicate, and differences between groups were compared using Student’s t-test. *: P < 0.05.</p

Microscopic observation of internalized <i>S</i>. <i>aureus</i>.

<p>Internalization of <i>S</i>. <i>aureus</i> N305 as observed by transmission electron microscopy. <i>S</i>. <i>aureus</i> N305 (at an MOI of 100:1) was incubated for 2 h with bMEC either alone (A, B) or in the presence of <i>L</i>. <i>casei</i> BL23 wt (C, D) or <i>srtA2</i> mutant (E, F) strains, at an MOI of 2,000:1.</p

Internalization of wild type and mutant strains of <i>L</i>. <i>casei</i> BL23 into bMEC.

<p><i>L</i>. <i>casei</i> populations internalized into bMEC were determined after 2 h of interaction at an MOI 2,000:1. The internalization assay of the <i>L</i>. <i>casei</i> BL23 wild type (wt) strain was used as a reference. Internalization rates were defined as the internalized population of mutant strains relative to the internalized <i>L</i>. <i>casei</i> BL23 wt strain population. Data are presented as mean ± standard deviations. Each experiment was done in triplicate and differences between groups were compared using Student’s t-test. *: P < 0.05.</p

Resistance of <i>L</i>. <i>casei</i> BL23 wt and <i>srtA2</i> strains to H₂O₂.

<p>Resistance of <i>L</i>. <i>casei</i> BL23 wt (●, ○) and <i>srtA2</i> (■, □) strains to H₂O₂ was evaluated in the stationary phase of growth of <i>L</i>. <i>casei</i> (24h—MRS). The residual population was evaluated at 0, 10, 20 and 30 min after exposure to 0.25% (●, ■) and 0.5% H₂O₂ (○, □). Data are presented as means ± standard deviations. Each experiment was done in triplicate, and differences between groups were compared using Student’s t-test. *: P < 0.05.</p

Impact of <i>L</i>. <i>casei</i> BL380 (BL23 <i>bnaG</i>) on <i>S</i>. <i>aureus</i> internalization into bMEC.

<p>Internalization rates of <i>S</i>. <i>aureus</i> N305 after 2 h of interaction with bMEC and co-incubation with <i>L</i>. <i>casei</i> BL23 and <i>L</i>. <i>casei</i> BL380 (<i>bnaG</i>) at an MOI of 2,000:1. <i>S</i>. <i>aureus</i> was used at an MOI of 100:1. The internalization assay of <i>S</i>. <i>aureus</i> alone was used as a reference. Internalization rates were then defined as the internalized <i>S</i>. <i>aureus</i> population in the presence of the different <i>L</i>. <i>casei</i> strains relative to the internalized <i>S</i>. <i>aureus</i> population of the reference experiment. Data are presented as means ± standard deviations. Each experiment was done in triplicate, and differences between groups were compared using one-way ANOVA with Bonferroni's Multiple Comparison Test. *: P < 0.05.</p

Cell surface proteome of <i>L</i>. <i>casei</i> BL23 wt and <i>srtA2</i> mutant as determined by enzymatic shaving.

<p>Cell surface proteome of <i>L</i>. <i>casei</i> BL23 wt and <i>srtA2</i> mutant as determined by enzymatic shaving.</p

Contribution of sortase SrtA2 to <i>Lactobacillus casei</i> BL23 inhibition of <i>Staphylococcus aureus</i> internalization into bovine mammary epithelial cells - Fig 4

<p><b>Internalization of <i>L</i>. <i>casei</i> BL23 wt (A) and <i>srtA2</i> mutant (B) strains as observed by transmission electron microscopy</b>. Degradation vesicles (white arrows) were observed in a greater proportion in cells containing mutant <i>srtA2</i>.</p