The myth and therapeutic potentials of postbiotics

Postbiotics (bioactives) are nonviable metabolites produced by probiotics that exert biological effects on the hosts. The myriad beneficial effects of postbiotics produced by six novel bacteriocinogenic Lactobacillus plantarum strains have been proven extensively since 2004, with the broad bacteriocin inhibitory activity against various pathogens, as they harbor two classes of bacteriocin structural genes (plnEF and pln W). The supplementation of the postbiotics to various animal models has significantly improved serum cholesterol, immune response, overall health, and growth, while suppressing the population of pathogenic bacteria in the digestive tract. Additionally, the postbiotics of these lactobacilli strains demonstrated novel antiproliferation and anticancer activity against various human cancer cell lines by inducing cytotoxicity via apoptotic pathway

The S-layer Associated Serine Protease Homolog PrtX Impacts Cell Surface-Mediated Microbe-Host Interactions of Lactobacillus acidophilus NCFM

Health-promoting aspects attributed to probiotic microorganisms, including adhesion to intestinal epithelia and modulation of the host mucosal immune system, are mediated by proteins found on the bacterial cell surface. Notably, certain probiotic and commensal bacteria contain a surface (S-) layer as the outermost stratum of the cell wall. S-layers are non-covalently bound semi-porous, crystalline arrays of self-assembling, proteinaceous subunits called S-layer proteins (SLPs). Recent evidence has shown that multiple proteins are non-covalently co-localized within the S-layer, designated S-layer associated proteins (SLAPs). In Lactobacillus acidophilus NCFM, SLP and SLAPs have been implicated in both mucosal immunomodulation and adhesion to the host intestinal epithelium. In this study, a S-layer associated serine protease homolog, PrtX (prtX, lba1578), was deleted from the chromosome of L. acidophilus NCFM. Compared to the parent strain, the PrtX-deficient strain (ΔprtX) demonstrated increased autoaggregation, an altered cellular morphology, and pleiotropic increases in adhesion to mucin and fibronectin, in vitro. Furthermore, ΔprtX demonstrated increased in vitro immune stimulation of IL-6, IL-12, and IL-10 compared to wild-type, when exposed to mouse dendritic cells. Finally, in vivo colonization of germ-free mice with ΔprtX led to an increase in epithelial barrier integrity. The absence of PrtX within the exoproteome of a ΔprtX strain caused morphological changes, resulting in a pleiotropic increase of the organisms’ immunomodulatory properties and interactions with some intestinal epithelial cell components

Updates on Metabolism in Lactic Acid Bacteria in Light of “Omic” Technologies

Lactic acid bacteria (LAB) comprise highly diverse bacterial genus and species characterized with a common feature, the ability to produce lactic acid from the fermentation of carbohydrates. Sugar metabolism of LAB together with other metabolic capacities such as proteolytic activity, production of aroma compounds and bioactive peptides, have been exploited throughout the world in the processing by fermentation of various food types, including milk, meat and plants. These bacteria are essential for the preservation of food and for maintaining and/or enhancing its organoleptic and nutritional quality. Studies on the wide metabolic capacity of LAB considering the use of different carbon and nitrogen sources and exploring their complex regulatory circuits are the main areas of current research on these bacteria. Moreover, high-throughput technologies and the exponentially growing data bases of complete genome sequences of different LAB species, as well as all other large-scale omic-techniques combined with systems biology, bring about a constant need for updating current knowledge in LAB biology. Furthermore, it addresses strategies to exploit such knowledge into the rational design and use of LAB strains with increased industrial and consumer functionality

Lactobacillus paracasei Comparative Genomics: Towards Species Pan-Genome Definition and Exploitation of Diversity

Contains fulltext : 119129.pdf (publisher's version ) (Open Access)Lactobacillus paracasei is a member of the normal human and animal gut microbiota and is used extensively in the food industry in starter cultures for dairy products or as probiotics. With the development of low-cost, high-throughput sequencing techniques it has become feasible to sequence many different strains of one species and to determine its "pan-genome". We have sequenced the genomes of 34 different L. paracasei strains, and performed a comparative genomics analysis. We analysed genome synteny and content, focussing on the pan-genome, core genome and variable genome. Each genome was shown to contain around 2800-3100 protein-coding genes, and comparative analysis identified over 4200 ortholog groups that comprise the pan-genome of this species, of which about 1800 ortholog groups make up the conserved core. Several factors previously associated with host-microbe interactions such as pili, cell-envelope proteinase, hydrolases p40 and p75 or the capacity to produce short branched-chain fatty acids (bkd operon) are part of the L. paracasei core genome present in all analysed strains. The variome consists mainly of hypothetical proteins, phages, plasmids, transposon/conjugative elements, and known functions such as sugar metabolism, cell-surface proteins, transporters, CRISPR-associated proteins, and EPS biosynthesis proteins. An enormous variety and variability of sugar utilization gene cassettes were identified, with each strain harbouring between 25-53 cassettes, reflecting the high adaptability of L. paracasei to different niches. A phylogenomic tree was constructed based on total genome contents, and together with an analysis of horizontal gene transfer events we conclude that evolution of these L. paracasei strains is complex and not always related to niche adaptation. The results of this genome content comparison was used, together with high-throughput growth experiments on various carbohydrates, to perform gene-trait matching analysis, in order to link the distribution pattern of a specific phenotype to the presence/absence of specific sets of genes