Applied and Environmental Microbiology vol:doi:10.1128/AEM.06192-11
Lactobacillus rhamnosus GG, a probiotic with good survival capacity in the human gut, has well documented adhesion properties and health effects. Recently, spaCBA-encoded pili that bind to human intestinal mucus were identified on its cell surface. Here, we report on the phenotypic analysis of a spaCBA pilus knock-out mutant in comparison with wild-type and other adhesin mutants. The SpaCBA pilus of L. rhamnosus GG showed to be key for efficient adherence to the Caco-2 epithelial cell (IEC) line and biofilm formation. Moreover, the spaCBA mutant induces an elevated level of interleukin (IL)-8 mRNA in Caco-2 cells compared to the wild-type, possibly involving an interaction of lipoteichoic acid with toll-like receptor 2. In contrast, an L. rhamnosus GG mutant without exopolysaccharides but with an increased exposure of pili leads to reduced expression of IL-8. Using Transwells to partition bacteria from Caco-2 cells, IL-8 induction is blocked completely regardless whether wild type or mutant L. rhamnosus GG cells are used. Taken together, our data suggest that L. rhamnosus GG SpaCBA pili, while promoting strong adhesive interactions IECs, have a unctional role in balancing IL-8 mRNA expression induced by surface molecules such as lipoteichoic acid.