Adhesive interactions between milk fat globule membrane and Lactobacillus rhamnosus GG inhibit bacterial attachment to Caco-2 TC7 intestinal cell

Abstract

Milk is the most popular matrix for the delivery of lactic acid bacteria, but little is known about how milk impacts bacterial functionality. Here, the adhesion mechanisms of Lactobacillus rhamnosus GG (LGG) surface mutants to a milk component, the milk fat globule membrane (MFGM), were compared using atomic force microscopy (AFM). AFM results revealed the key adhesive role of the LGG SpaCBA pilus in relation to MFGM. A LGG mutant without exopolysaccharides but with highly exposed pili improved the number of adhesive events between LGG and MFGM compared to LGG wild type (WT). In contrast, the number of adhesive events decreased significantly for a LGG mutant without SpaCBA pili. Moreover, the presence of MFGM in the dairy matrix was found to decrease significantly the bacterial attachment ability to Caco-2 TC7 cells. This work thus demonstrated a possible competition between LGG adhesion to MFGM and to epithelial intestinal cells. This competition could negatively impact the adhesion capacity of LGG to intestinal cells in vivo, but requires further substantiation.

In Vitro Effects of Live and Heat-Inactivated Bifidobacterium animalis Subsp. Lactis, BB-12 and Lactobacillus rhamnosus GG on Caco-2 Cells

“…The differences observed between L. rhamnosus GG and B. animalis subsp. lactis, BB-12, confirming the observations of others [26], are likely due to intrinsic properties of each organism, such as the presence of the pili in L. rhamnosus GG [27], the composition of the cell wall with components such as lipoteichoic acid [24], and the presence of proteins that contribute to coping with stress conditions such as heat-inactivation [28].…”

The surface properties of milk fat globules govern their interactions with the caseins: Role of homogenization and pH probed by AFM force spectroscopy

“…Although the WLC model is adapted to study the stretching of single molecules, it provides supplementary insights on the integrity and flexibility of molecules during multiple interactions which is likely to occur when using colloidal probes [23]. Adhesion events were therefore the signature of the stretching of polypeptides molecules, i.e.…”

“…In order to probe specific interactions, the AFM tip is functionalized with the molecule of interest. To date, investigations performed by AFM force spectroscopy to measure interaction forces between individual objects involved in food applications were essentially conducted on bacteria interacting with proteins [20][21][22] or MFGM [23], or on interacting bubbles and/or droplets [24][25][26]. However, the link between nanoscale force spectroscopy and bulk properties is not investigated, albeit identified as important [27].…”

Microbial adhesion and ultrastructure from the single-molecule to the single-cell levels by Atomic Force Microscopy

“…These signatures reflect the nanospring mechanism by which pili withstand shear forces during bacterial adhesion. This was further confirmed with tip decorated with milk proteins, the target of LGG pili for adhesion in dairy ( Guerin et al, 2018a , Guerin et al, 2018b ). Very different force distance signatures were obtained for the unfoding of pili from Gram-negative bacteria such as P. aeruginosa and E. coli ( Forero et al, 2006 , Beaussart et al, 2014a , Mulansky et al, 2017 ), resulting in plateaus preceded by a region of zero force, which are most likely due to a force-induced conformational changes within individual pili.…”