Fig 1.

The adhesion capacity of wild-type L. rhamnosus GG and its knockout mutant derivatives to IECs. (A) Overnight-grown L. rhamnosus GG cells were coincubated with the Caco-2 cells for 1.5 h, and thereafter the proportion of adherent bacteria, expressed as a percentage, was determined. Wild-type L. rhamnosus GG is indicated as LGG WT, and further details about the mutant strains are described in Table 1. The results shown are for 10⁷ CFU/ml added, but similar trends were observed with 10⁸ CFU/ml. Inclusion of anti-SpaC serum for antibody-mediated inhibition experiments is denoted by SpaC As. Each experiment was done in triplicate, and corresponding standard deviations are indicated by error bars. Data set comparisons (mutant strains versus the wild type) considered significant (P < 0.05) are indicated with an asterisk. (B) Immuno-EM analysis of L. rhamnosus GG and its EPS-deficient welE mutant (CMPG5351). SpaC-containing pili are identified by anti-SpaC antibodies conjugated to gold particles, which are seen as small dark dots (arrows). (C) Visualization of the adhesion pattern between various L. rhamnosus GG strains and epithelial Caco-2 cells by epifluorescence microscopy. Cells of wild-type L. rhamnosus GG (LGG WT) and the spaCBA (CMPG5357) and welE (CMPG5351) mutant strains are indicated. Inclusion of anti-SpaC antibody is denoted by SpaC As.