## 4 Discussion
In our study, we also demonstrated a biofilm-forming capability and the capability to hydrolyze tauro-conjugated bile salts of _L. plantarum_ CNTA 628, two probiotic properties with great applications. In mammals, the main protection against pathogenic infections is the intestinal barrier, mainly composed of epithelial cells with specific characteristics. However, these cells alone are not sufficient, as the resident gut microbiota play a crucial role in preserving the integrity of the intestinal barrier. In this context, lactic acid bacteria have been extensively studied in the recent years for their capacity of \"fighting\" pathogens like _Salmonella_, _Escherichia coli_ and _Clostridium_[48]. It has been speculated that alterations in the microbiome lead to the development of conditions such as inflammatory bowel disease (IBD). In fact, IBD patients display an increased proportion of Enterobacteriaceae genus and a decreased concentration of bacteria from the phylum Firmicutes [49]. Moreover, patients suffering from [PERSON]'s disease also have an anomalous amount of adherent invasive _Escherichia coli_. Caco-2 cells have been widely used as a model for the intestinal barrier because they develop the characteristics of a mature enterocyte [50]. Previous works showed that _L. plantarum_ was able to compete and displace _E. coli_ O157:H7, indicating that _Lactobacillus_ might share binding sites with pathogenic bacteria, therefore being capable of excluding or displacing them. Such an effect is probably strain-specific, dependent on the different molecules and patterns expressed on the bacterial wall of each strain. Indeed, [PERSON] et al. demonstrated that _L. plantarum_ 299V expresses GAPDH on its surface, facilitating the adhesion and colonization of the intestinal lining [51]. Additionally, lactic acid bacteria can compete for attachment sites on intestinal epithelial cells (IECs), glycoproteins, or plasminogen within the extracellular matrix [52]. Altogether, it suggests that _L. plantarum_ strains possess great potential as treatment for proinflammatory intestinal diseases. Some mice studies have shown that only the surface proteins from _L. plantarum_ MTCC 5690, are capable of neutralizing the histopathological damages in a pathological mouse model [53]. Finally, _L. plantarum_ has been characterized to produce a bacteriocin, plantaricin, which is capable of inhibiting the growth of pathogenic bacteria like _E. coli_ or _Listeria monocytogenes_[54]. Following this trend, here, we demonstrated that our probiotic strain _L. plantarum_ CNTA 628 is capable of competing and displacing _E. coli_ O157:H7 to Caco-2 cells. _Lactobacillus_ genus has been extensively studied for modulating immune responses. The cell wall of lactic bacteria contains certain molecules that interact with immune cells in the intestine and potentially activate them [55; 56]. Such activation has been suggested to be beneficial for inhibiting viral infections. Other studies have reported that a specific strain of _L. plantarum_ enhances the immune system in an immunocompromised mouse model [57]. Moreover, additional beneficial roles of _L. plantarum_ have been identified, like the ameliorating lipidic profile of patients and decreasing atherosclerosis [58]. In fact, _L. plantarum_ decreases cholesterol and reactive protein C in older patients [59]. Interestingly, three different strains of _L. plantarum_ have been shown to exert diverse effects on modulating cytokine production in mouse splenocytes [60]. For this reason, we investigated the potential immunomododulatory activity of _L. plantarum_ CNTA 628 in RAW 264.7 and HT-29 cell lines. Once we evidenced the lack of cytotoxicity in both cell lines after exposure to hydrocortisone and _L. plantarum_ CNTA 628, we analyzed the potential activity of the probiotic modulating the LPS-induced cytokine production. Although no effect was observed on IL-10 and IL-6 production, _L.