Functional characterization of probiotic surface layer protein-carrying Lactobacillus amylovorus strains

Abstract

BackgroundAdhesiveness to intestinal epithelium, beneficial immunomodulating effects and the production of pathogen-inhibitory compounds are generally considered as beneficial characteristics of probiotic organisms. We showed the potential health-promoting properties and the mechanisms of probiotic action of seven swine intestinal Lactobacillus amylovorus isolates plus the type strain (DSM 20531T) by investigating their adherence to porcine intestinal epithelial cells (IPEC-1) and mucus as well as the capacities of the strains to i) inhibit the adherence of Escherichia coli to IPEC-1 cells, ii) to produce soluble inhibitors against intestinal pathogens and iii) to induce immune signaling in dendritic cells (DCs). Moreover, the role of the L. amylovorus surface (S) –layers - symmetric, porous arrays of identical protein subunits present as the outermost layer of the cell envelope - in adherence to IPEC-1 cells was assessed using a novel approach which utilized purified cell wall fragments of the strains as carriers for the recombinantly produced S-layer proteins.ResultsThree of the L. amylovorus strains studied adhered to IPEC-1 cells, while four strains inhibited the adherence of E. coli, indicating additional mechanisms other than competition for binding sites being involved in the inhibition. None of the strains bound to porcine mucus. The culture supernatants of all of the strains exerted inhibitory effects on the growth of E. coli, Salmonella, Listeria and Yersinia, and a variable, strain-dependent induction was observed of both pro- and anti-inflammatory cytokines in human DCs. L. amylovorus DSM 16698 was shown to carry two S-layer-like proteins on its surface in addition to the major S-layer protein SlpA. In contrast to expectations, none of the major S-layer proteins of the IPEC-1 -adhering strains mediated bacterial adherence.ConclusionsWe demonstrated adhesive and significant pathogen inhibitory efficacies among the swine intestinal L. amylovorus strains studied, pointing to their potential use as probiotic feed supplements, but no independent role could be demonstrated for the major S-layer proteins in adherence to epithelial cells. The results indicate that many intestinal bacteria may coexist with and confer benefits to the host by mechanisms not attributable to adhesion to epithelial cells or mucus.

Influence of osmotic stress on the profile and gene expression of surface layer proteins in Lactobacillus acidophilus ATCC 4356

“…We also found that the processing of the signal peptide of the SlpA protein renders a 413-amino-acid mature protein beginning with the sequence ATTINA, as described for other Lactobacillus species (Lortal et al 1992;Vidgrén et al 1992;Sillanpää et al 2000;Ventura et al 2000;Sára and Sleytr 2000;Hynönen et al 2014).…”

Colonisation potential of plantaricin-producing Lactobacillus plantarum SF9C andS-layer-carrying Lactobacillus brevis SF9B among gut microbiota

“…Previously, we monitored lactic acid bacteria (LAB) population during spontaneous fermentation of the Brassica oleracea var. capitata cultivar Varaždinski (Banić et al, 2018;Beganović et al, 2014;Beganović et al, 2011). At the onset of the spontaneous fermentation, LAB diversity was present, including Leuconostoc mesenteroides strains, while a restricted number of Lactobacillus species, mainly Lactobacillus plantarum, dominated in the latter stages (Beganović et al, 2014).…”

“…brevis SF9B was isolated from the respective spontaneous fermentation. This strain showed desirable functional and technological properties largely influenced by S-layer proteins (Slps) which were detected by SDS-PAGE (Beganović et al, 2014) and identified by 2D electrophoresis followed by LC-MS analysis. Slps have a functional role in conveying increased survival of the respective strain in simulated GIT conditions and during freeze-drying.…”

Characteristics of surface layer proteins from two new and native strains of Lactobacillus brevis

“…features of Lactobacillus strains can be interesting factor to S-layer of these bacteria [5][6][7]. Some biochemical properties of Lactobacillus S-layer are unique compared with S-layer of other bacteria, for example in their smaller size (25-71 kDa) and high predicted pI value (9.4-10.4).…”

“…SDS-PAGE analysis. Lanes(4,6), Total protein from untreated cells, (3,7) primary LiCl extracted S-layer, (2,8) Total protein from treated cells, (1,9) secondary LiCl extracted S-layer (1,9) from two strains, L. brevis KM7 and brevis KM3 respectively and (5) protein marker.…”