Preventive effects of Lactobacillus plantarum ST-III against Salmonella infection

Lactiplantibacillus plantarum ST-III and Lacticaseibacillus rhamnosus KF7 Enhance the Intestinal Epithelial Barrier in a Dual-Environment In Vitro Co-Culture Model

Intestinal barrier hyperpermeability, which is characterised by impaired tight junction proteins, is associated with a variety of gastrointestinal and systemic diseases. Therefore, maintaining intestinal barrier integrity is considered one of the effective strategies to reduce the risk of such disorders. This study aims to investigate the potential benefits of two probiotic strains (Lactiplantibacillus plantarum ST-III and Lacticaseibacillus rhamnosus KF7) on intestinal barrier function by using a physiologically relevant in vitro model of the intestinal epithelium. Our results demonstrate that both strains increased transepithelial electrical resistance, a measure of intestinal barrier integrity. Immunolocalisation studies indicated that this improvement in barrier function was not due to changes in the co-localisation of the tight junction (TJ) proteins ZO-1 and occludin. However, we observed several modifications in TJ-related genes in response to the probiotics, including the upregulation of transmembrane and cytosolic TJ proteins, as well as TJ signalling proteins. Gene expression modulation was strain- and time-dependent, with a greater number of differentially expressed genes and higher fold-change being observed in the L. plantarum ST-III group and at the latter timepoint. Further studies to investigate how the observed gene expression changes can lead to enhanced barrier function will aid in the development of probiotic foods to help improve intestinal barrier function.

Bifidobacterium animalis subsp. lactis boosts neonatal immunity: unravelling systemic defences against Salmonella

Bifidobacterium animalis subsp. lactis may be a useful probiotic intervention for regulating neonatal intestinal immune responses and counteracting Salmonella infection. However, recent research has focused on intestinal immunity, leaving uncertainties regarding the central, peripheral, and neural immune responses in neonates. Therefore, this study investigated the role and mechanisms of B. animalis subsp. lactis in the systemic immune responses of neonatal rats following Salmonella infection. Through extremely early pretreatment with B. animalis subsp. lactis (6 hours postnatal), the neonatal rat gut microbiota was effectively reshaped, especially the Bifidobacterium community. In the rats pretreated with B. animalis subsp. lactis, Salmonella was less prevalent in the blood, liver, spleen, and intestines following infection. The intervention promoted T lymphocyte subset balance in the spleen and thymus and fostered neurodevelopment and neuroimmune balance in the brain. Furthermore, metabolic profiling showed a strong correlation between the metabolites in the serum and colon, supporting the view that B. animalis subsp. lactis pretreatment influences the systemic immune response by modifying the composition and metabolism of the gut microbiota. Overall, the results imply that B. animalis subsp. lactis pretreatment, through the coordinated regulation of colonic and serum metabolites, influences the systemic immune responses of neonatal rats against Salmonella infection.

Assessments of Probiotic Potentials of Lactiplantibacillus plantarum Strains Isolated From Chinese Traditional Fermented Food: Phenotypic and Genomic Analysis

The lack of rapid and effective approaches to determine the health benefits of strains is one of the main challenges affecting the selection of probiotics from large numbers of candidates. In this study, the probiotic potential of 44 Lactiplantibacillus plantarum strains isolated from different Chinese traditional fermented foods was evaluated, including acid and bile salt resistance, adhesion ability, survival in simulated human gastrointestinal transit, antioxidant activity, bile salt hydrolase (BSH) activity, and antibacterial activity. All tested L. plantarum strains showed high antioxidant capacity, BSH activity, and antibacterial activity. Among the strains, B652, C232, D444, and E932 were identified as the best comprehensive performed strains, which were selected for whole-genome sequencing, in order to provide clear information and identify key genes responsible for functional characteristics in vitro. It demonstrated that the antioxidant activity, adhesion activity, and ability to survive in the simulated gastric environment were found to be closely correlated with antioxidant enzyme encoding genes, cell-surface protein-encoding genes, and stress response genes, respectively. The numbers of functional genes present in strains might decide their performance in probiotic profile evaluation. The outcome of the study could support the development of a novel approach for the screening and identification of probiotics.

Horizontally Acquired Polysaccharide-Synthetic Gene Cluster From Weissella cibaria Boosts the Probiotic Property of Lactiplantibacillus plantarum

Lactiplantibacillus plantarum are probiotic bacteria, maintaining the integrity of the gastrointestinal epithelial barrier, and preventing the infection of pathogenic bacteria. Exopolysaccharides (EPSs) are often involved in the probiotic property of L. plantarum. Here, we identified a new EPS-synthetic gene cluster, cpsWc, carrying 13 genes, laid on a large plasmid in a well-characterized probiotic L. plantarum strain LTC-113. The cpsWc gene cluster was horizontally acquired from Weissella cibaria, enhancing the biofilm formation ability of the host strain and its tolerance to harsh environmental stresses, including heat, acid, and bile. Transfer of cpsWc also conferred the probiotic properties to other L. plantarum strains. Moreover, cpsWc strengthened the adhesion of LTC-113 to intestinal epithelial cells. Both the cpsWc-carrying LTC-113 and its EPSs per se effectively attenuated the LPS-induced pro-inflammatory effect of intestinal epithelial cells, and inhibited the adhesion of pathogenic bacteria, such as S. typhimurium and E. coli by exclusion and competition. The newly identified cpsWc gene cluster emphasized the contribution of mobile EPS-synthetic element on the probiotic activity of L. plantarum, and shed a light on the engineering of probiotic bacteria.