RP2E INRA Université de Lorraine

Adhesive interactions between milk glycoproteins and Lactobacillus rhamnosus GG impact bacterial attachment to intestinal cell

NanoInBio, 22-27 mai, Le Gosier (Guadeloupe), France

Burgain, J., Guerin, J., Soligot-Hognon, C., Huguet, M., Francius, G., El-kirat-chatel, S., Gomand, F., Le Roux, Y., Borges, F., Scher, J., Gaiani, C.


Human milk plays an essential role in naturally protecting the neonatal gut from infections. This beneficial effect can be attributed to the presence of biomolecules such as oligosaccharides and glycoconjugates. Amongst these fractions, human milk glycoproteins (GPs) are known to exhibit strong antiadhesive activities toward a wide variety of pathogens. GPs can act as decoys and bind to bacterial adhesive sites, which prevents them from binding to tissue.

On the opposite, direct binding of probiotic bacteria to host cells is needed to obtain a beneficial effect. Probiotic bacteria exert a variety of beneficial effects, including positive changes in the microbiota composition, regulation of the epithelial barrier function, modulation of immune responses, and interactions with the gut-brain barrier. Lactobacillus rhamnosus GG (LGG) is one of the best clinically documented and most commercialized probiotic microorganisms, with documented health benefits ranging from gastro-intestinal health to immune modulatory effects. LGG is known for its adhesive capacity. When LGG binds to enteric epithelium, the adhesion of other pathogens is inhibited. This process is called competitive colonization and stands for one of the first underlying causes of the effectiveness of LGG in preventing intestinal infection. LGG is active when adhering to mucus and this is largely due to its pili.

Milk is the most popular matrix used as a delivery system of lactic acid bacteria but the ability of GPs to prevent bacterial attachment to epithelial cells is important to consider as it would be deleterious to functional food efficiency. In the present project, LGG (wild-type strain) and three of its surface mutants were used as candidate to testthe ability of milk GPs to inhibit bacterial adhesion to intestinal cells.

First, LGG surface mutants were compared using Atomic Force Microscopy (AFM) in force spectroscopy mode with tips decorated with milk proteins to better understand adhesion mechanisms with milk GPs. Results demonstrated the ability of LGG cells to adhere via their SpaCBA pili to milk GPs. Pili also stand for the surface structure engaged in bacterial adhesion to epithelial intestinal cells. It was highlighted that the presence of GPs in the dairy matrix decrease significantly bacteria attachment ability to Caco-2 TC7 cells. It is therefore suggested that the GPs bind to the SpaCBA pili adhesion sites and inhibit further adhesion to Caco-2 TC7 cells when LGG reach the intestine in presence of this component.

This work highlights a possible competition between LGG adhesion to milk GPs and to epithelial intestinal cells. This competition impacts negatively the adhesion capacity of LGG to intestinal cells and could be detrimental to its probiotic action. However, further work is required to evaluate if the successive digestion steps can impact the bacterial adhesion to milk GPs thus allowing the strains to preserve their ability to bind enteric epithelium.

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