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

2014-07-28
BMC microbiology 14(1)

PubMed: 25070625
DOI: 10.1186/1471-2180-14-199

Study Design

Population: seven swine intestinal Lactobacillus amylovorus isolates plus the type strain (DSM 20531T)
Methods: 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); the role of the L. amylovorus surface (S)-layers in adherence to IPEC-1 cells was assessed using purified cell wall fragments of the strains as carriers for the recombinantly produced S-layer proteins

Animal Study

Background

Adhesiveness 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.

Results

Three 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.

Conclusions

We 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.

Research Insights

Supplement	Dose	Health Outcome	Effect Type	Effect Size	Source
Lactobacillus amylovorus	—	Enhanced Intestinal Epithelial Cell Adhesion	Beneficial	Small	View source Three of the L. amylovorus strains studied adhered to IPEC-1 cells
Lactobacillus amylovorus	—	Improved Immune System Modulation	Beneficial	Small	View source a variable, strain-dependent induction was observed of both pro- and anti-inflammatory cytokines in human DCs
Lactobacillus amylovorus	—	Increased Inhibition of Pathogenic Bacteria	Beneficial	Moderate	View source The culture supernatants of all of the strains exerted inhibitory effects on the growth of E. coli, Salmonella, Listeria and Yersinia