Among the extracellular proteins detected, cell wall hydrolases, muramidases, peptidoglycan-binding polypeptides, and a precursor of the collagen-binding A protein were identified. In addition, some moonlighting proteins, such as glyceraldehyde 3-phosphate dehydrogenase, were also found. selleck The bacterial lysis of the cultures was negligible, as can be deduced from the comparison of secreted protein/total protein profiles obtained by SDS-PAGE (Fig. 3c). Analysis of the relative electrophoretic mobility of the proteins recovered after binding experiments suggested that the surface proteins ABC transporter periplasmic protein, ornithine carbamoyltransferase, and a high-affinity

cystine-binding protein bound mucin (Fig. 4a). Also, the secreted Selleckchem ABT199 GAPDH of L. plantarum Li69 and Li70 and that of L. gasseri Lv19 bound mucin, as it did muramidase and putative extracellular protein

from L. plantarum Lv69 and Li70 (Fig. 4b). One of the tests considered as crucial by the FAO/WHO for the in vitro evaluation of potential probiotic candidates is their capacity to adhere to mucin and human epithelial cells, as well as their antagonism toward pathogen establishment (FAO/WHO, 2006). The eight most adherent Lactobacillus strains were selected, and their adhesion abilities to three cell lines, their capability of interfering with the adhesion of two vaginal pathogens to a model human cell line, and the identification of their extracellular proteins and their ability to bind mucin were established. Presence of typical intestinal lactobacilli, such as L. plantarum, in vaginal environment has been reported previously and related to the decreased risk of second bacterial vaginosis (Antonio et al., 2005). Besides, the vaginal epithelium is also covered by a protective layer of mucus, which is mainly composed of mucins as the intestinal one,

although no commercial vaginal mucin is available (Dasari et al., 2007). In this context, mucins produced in the gastrointestinal and vaginal epithelium are very different. In the gut, MUC2 is mainly produced by goblet cells (McGuckin et al., 2011), whereas in the vaginal epithelium, MUC1, MUC4, MUC5AC, MUC5B, or MUC6 is produced, depending on the location (Gipson et al., 1997). Regarding the adhesion experiments to human cell lines, the four intestinal isolates presented affinities to HT-29 cells in the order of the positive control L. plantarum 229V. Therefore, this is an especially valuable probiotic property that, join to their ability to resist bile salts and acid (data not shown), might allow the use of Lv67, Li68, and Li71 in restoration of the vaginal ecosystem through oral administration. Binding of lactobacilli or their secreted compounds may either hinder colonization of the epithelium by potential pathogens, or create a barrier between them and the mucosal cells, thus excluding direct contact with the underlying epithelium.