Surface proteins involved in the adhesion of Streptococcus salivarius to human intestinal epithelial cells

Abstract

The adhesion properties of 14 Streptococcus salivarius strains to mucus (HT29-MTX) and non-mucus secreting (Caco-2/TC7) human intestinal epithelial cells were investigated. Ability to adhere to these two eukaryotic cell lines greatly differs between strains. The presence of mucus played a major factor in adhesion, likely due to high adhesiveness to mucins present in the native human mucus layer covering the whole cell surface. Only one S. salivarius strain (F6-1), isolated from the feces of a healthy baby, was found to strongly adhere to HT-29 MTX cells at a level comparable to that of Lactobacillus rhamnosus GG, a probiotic strain considered to be highly adherent. By sequencing the genome of F6-1, we were able to identify 36 genes encoding putative surface proteins. Deletion mutants were constructed for six of them and their adhesion abilities on HT-29 MTX cells were checked. Our study confirmed that four of these genes encode adhesins involved in the adhesion of S. salivarius to host cells. Such adhesins were also identified in other S. salivarius strains.Electronic supplementary materialThe online version of this article (10.1007/s00253-018-8794-y) contains supplementary material, which is available to authorized users.

In Vitro Evaluation of Adhesion Capacity, Hydrophobicity, and Auto-Aggregation of Newly Isolated Potential Probiotic Strains

“…High auto-aggregation was also reported for the strains of L. casei and L. fermentum, ranging from 60.97% to 96.18% [19]. Some studies reported a correlation between aggregation and adhesion capacity [41]; on the contrary, other studies did not demonstrate such a correlation and link between these two properties [13]. According to our results, strains having good adhesion capacities to the cell culture, usually had good auto-aggregation properties.…”

“…Bacterial adhesion is based on non-specific physicochemical interactions between two surfaces, and therefore, it is usually associated with the characteristics of the cell surface. The adhesion ability to mucin-producing cells is better than to non-mucus-producing ones; thus, the presence of mucus seems to play a major role in adhesion [13]. Accordingly, to compare adhesive properties of bacteria in vitro, we used a co-culture of non-mucus-secreting Caco-2 cells and mucus-secreting HT-29-MTX cells in the ratio 9:1 as a model of intestinal mucosa.…”

“…To drive their differentiation in vitro, methotrexate (MTX) is used. The secreted mucus is mainly composed of the MUC5AC mucin, which is produced in the stomach [13,14]. Generally, adhesion is a complex process involving non-specific (hydrophobic interactions between cell surfaces) and specific ligand-receptor interactions [6].…”

“…Generally, adhesion is a complex process involving non-specific (hydrophobic interactions between cell surfaces) and specific ligand-receptor interactions [6]. Different structures and specific cell wall components of bacteria, such as fimbriae or pili, adhesins, mucus-binding proteins, fibronectin-binding proteins, or surface layer proteins, provide them an advantage for epithelial colonization; further, lipoteichoic acid or exopolysaccharides produced by bacteria can contribute to adhesion to host epithelial cells [12,13,15,16]. Interactions among all these properties important for adhesion provide the benefit of intestine colonization to probiotic strains.…”

“…Auto-aggregation of probiotic bacteria is necessary for adhesion to epithelial cells and mucosal surfaces, and thus for the colonization of the gastrointestinal tract [17]. Moreover, it is an important phenotype for adhesion [13].…”