Fig 2.

Adhesive properties of L. lactis expressing the FCT-1 M6 pilus operon and its Δap1_M6 derivative. A. Immunoelectron microscopy image of a L. lactis recombinant strain harbouring the entire FCT-1 M6 pilus operon. B. Immunoelectron microscopy image of a L. lactis recombinant strain harbouring the FCT-1 M6 pilus operon deprived of the ap1 gene. In both cases, bacteria were first incubated with polyclonal sera raised against rBP_M6, and then labelled with secondary antibodies conjugated with 5 nm gold particles. Pictures were taken at 60× magnification. C. Immunoblot analysis of L. lactis cell wall extracts incubated with antisera raised against rBP_M6 and rAP1_M6 pilus proteins. D. Binding of L. lactis recombinant strains to A549 lung epithelial cells (moi 20:1) after 30 min of incubation, expressed as percentage of cell-associated versus total bacteria. Results are presented as the mean and standard deviation values of three independent experiments run in triplicate wells. Significant differences between strains (**P < 0.01) were estimated using the Student's t-test.