Unraveling the role of surface mucus-binding protein and pili in muco-adhesion of lactococcus lactis

Doan Le (1, 2) , Thi-Ly Tran (2) , Marie-Pierre Duviau (2) , Mickael Meyrand (3) , Yann Guerardel (4) , Mickaël Castelain (2) , Pascal Loubière (2) , Marie-Pierre Chapot-Chartier (3) , Etienne Dague (1) , Muriel Mercier-Bonin (3)

1 LAAS-NBS - Équipe NanoBioSystèmes
2 LISBP - Laboratoire d'Ingénierie des Systèmes Biologiques et des Procédés
3 MICALIS - MICrobiologie de l'ALImentation au Service de la Santé
4 UGSF - Unité de Glycobiologie Structurale et Fonctionnelle - UMR 8576

Adhesion of bacteria to mucus may favor their persistence within the gut and their beneficial effects to the host. Interactions between pig gastric mucin (PGM) and a natural isolate of Lactococcus lactis (TIL448) were measured at the single-cell scale and under static conditions, using atomic force microscopy (AFM). In parallel, these interactions were monitored at the bacterial population level and under shear flow. AFM experiments with a L. lactis cell-probe and a PGM-coated surface revealed a high proportion of specific adhesive events (60%) and a low level of non-adhesive ones (2%). The strain muco-adhesive properties were confirmed by the weak detachment of bacteria from the PGM-coated surface under shear flow. In AFM, rupture events were detected at short (1002200 nm) and long distances (up to 6002800 nm). AFM measurements on pili and mucus-binding protein defective mutants demonstrated the comparable role played by these two surface proteinaceous components in adhesion to PGM under static conditions. Under shear flow, a more important contribution of the mucus-binding protein than the pili one was observed. Both methods differ by the way of probing the adhesion force, i.e. negative force contact vs. sedimentation and normal-to-substratum retraction vs. tangential detachment conditions, using AFM and flow chamber, respectively. AFM blocking assays with free PGM or O-glycan fractions purified from PGM demonstrated that neutral oligosaccharides played a major role in adhesion of L. lactis TIL448 to PGM. This study dissects L. lactis muco-adhesive phenotype, in relation with the nature of the bacterial surface determinants.

Domaines: Sciences du Vivant [q-bio]

Doan Le, Thi-Ly Tran, Marie-Pierre Duviau, Mickael Meyrand, Yann Guerardel, et al.. Unraveling the role of surface mucus-binding protein and pili in muco-adhesion of lactococcus lactis. PLoS ONE, 2013, 8 (11), ⟨10.1371/journal.pone.0079850⟩. ⟨hal-01204286⟩