In silico, in vitro and in vivo safety evaluation of Limosilactobacillus reuteri strains ATCC PTA-126787 & ATCC PTA-126788 for potential probiotic applications

Effects of Limosilactobacillus reuteri strains PTA-126787 and PTA-126788 on intestinal barrier integrity and immune homeostasis in an alcohol-induced leaky gut model

Intestinal barrier is a first line of defense that prevents entry of various harmful substances from the lumen into the systemic environment. Impaired barrier function with consequent translocation of harmful substances into systemic circulation ("leaky gut") is a central theme in many gastrointestinal, autoimmune, mental, and metabolic diseases. Probiotics have emerged as a promising strategy to maintain intestinal integrity and address "leaky gut". Using in silico, in vitro and avian in vivo analyses, we previously showed that two novel L. reuteri strains, PTA-126787 (L. reuteri 3630) and PTA-126788 (L. reuteri 3632), isolated from broiler chickens possess favorable safety profiles. Consistent with a recent study, here we show that L. reuteri 3630 and 3632 are phylogenetically similar to human L. reuteri strains. Daily administration of high doses of L. reuteri 3630 and 3632 to Sprague Dawley rats for 28 days was found to be safe with no adverse effects. More importantly, administration of L. reuteri 3630 and 3632 significantly reduced markers associated with alcohol-induced leaky gut, by downregulating inflammatory cytokines and upregulating anti-inflammatory cytokines in an alcohol model of leaky gut in mice. While L. reuteri 3630 cells and supernatant showed no activation, L. reuteri 3632 cells but not supernatant showed activation of AhR, a key transcription factor that regulates gut and immune homeostasis. L. reuteri 3630 is creamish white in morphology typical of Lactobacillus species and L. reuteri 3632 displays a unique orange pigmentation, which was stable even after passaging for 480 generations. We identified a rare polyketide biosynthetic gene cluster in L. reuteri 3632 that likely encodes for the orange-pigmented secondary metabolite. Similar to L. reuteri 3632 cells, the purified orange metabolite activated AhR. All together, these data provide evidence on the phylogenetic relatedness, safety, efficacy, and one of the likely mechanisms of action of L. reuteri 3630 and 3632 for potential probiotic applications to address "leaky gut" and associated pathologies in humans.

In vitro and in vivo genome-based safety evaluation of Lacticaseibacillus rhamnosus LRa05

The aim of this study was to comprehensively evaluate the safety of Lacticaseibacillus rhamnosus LRa05 (hereinafter "LRa05") to determine its suitability for use as a probiotic in the food industry. First, we sequenced the genome of LRa05 and then determined whether it contained genes associated with antibiotic resistance, virulence, or pathogenicity. Second, we evaluated the safety of LRa05 in vitro by performing a hemolysis assay and examining its ability to produce biogenic amines, its antimicrobial susceptibility, its capacity to transfer antibiotic resistance genes, its genomic stability, and whether it contained potential virulence factors. Third, we investigated the pathogenicity of LRa05 in mice by oral gavage and intraperitoneal injection. A bioinformatics analysis revealed no evidence that the genome of LRa05 contains genes associated with virulence or antibiotic resistance. In addition, the results of in vitro experiments showed that LRa05 does not produce d-lactic acid or exhibit hemolytic activity and is sensitive to clinically relevant antibiotics. Furthermore, a pathogenicity test revealed that LRa05 exhibits no lethality or toxicity in mice. Taken together, these findings indicate that LRa05 is sufficiently safe to be explored as a potential probiotic for use in the food industry.

Draft genome sequence of Limosilactobacillus reuteri, isolated from human breast milk

Limosilactobacillus reuteri is a lactic acid bacterium with several probiotic properties. Here, we present the draft genome sequence of L. reuteri isolated from human breast milk. The average genome size was estimated as 2,087,202 bp, with a guanine-cytosine (GC) content of 51.6%. GC content is the percentage of nitrogenous bases in a DNA or RNA molecule that are either guanine (G) or cytosine (C). De Man, Rogosa and Sharpe, often abbreviated to MRS, is a selective culture medium designed to favor the luxuriant growth of lactobacilli for lab study.

Limosilactobacillus reuteri in immunomodulation: molecular mechanisms and potential applications

Frequent use of hormones and drugs may be associated with side-effects. Recent studies have shown that probiotics have effects on the prevention and treatment of immune-related diseases. Limosilactobacillus reuteri (L. reuteri) had regulatory effects on intestinal microbiota, host epithelial cells, immune cells, cytokines, antibodies (Ab), toll-like receptors (TLRs), tryptophan (Try) metabolism, antioxidant enzymes, and expression of related genes, and exhibits antibacterial and anti-inflammatory effects, leading to alleviation of disease symptoms. Although the specific composition of the cell-free supernatant (CFS) of L. reuteri has not been clarified, its efficacy in animal models has drawn increased attention to its potential use. This review summarizes the effects of L. reuteri on intestinal flora and immune regulation, and discusses the feasibility of its application in atopic dermatitis (AD), asthma, necrotizing enterocolitis (NEC), systemic lupus erythematosus (SLE), rheumatoid arthritis (RA), and multiple sclerosis (MS), and provides insights for the prevention and treatment of immune-related diseases.

Whole-genome analysis of gamma-aminobutyric acid producing Psychobiotic Limosilactobacillus reuteri with its Untargeted metabolomics using UHPLC-Q-Tof MS/MS

The gamma amino butyric acid (GABA) is a chemical messenger and is essential for the health of the brain and muscles. Some lactic acid bacteria (LAB) have the potential to function as psychobiotic cultures because they can produce significant amounts of neuroactive compounds like GABA. Psychobiotics are known to alter bidirectional communication between the gastrointestinal tract and the central nervous system. In the present study, the Limosilactobacillus reuteri (L. reuteri) strain, isolated from human breast milk, was used to detect the GABA-producing glutamic acid decarboxylase (gad) gene and GABA production. PCR, HPLC and UHPLCQ-TOF-MS² approaches were applied to identify the gad gene, GABA content, and bioactive compounds produced by the bacterial strain, respectively. Additionally, the whole genome was sequenced to better understand the strain's psychobiotic and technological genomic properties. The gadB and gadC genes were confirmed in plasmid 1 of the whole genome. The complete genome sequence of L. reuteri comprises the genome length of 2,087,202 bp with 51.6 percent of G + C content. The results indicate that L. reuteri can be used as a starter culture for the production of GABA-enriched functional foods as well as psychobiotics for health benefits.

Development and Applications of CRISPR/Cas9-Based Genome Editing in Lactobacillus

Lactobacillus, a genus of lactic acid bacteria, plays a crucial function in food production preservation, and probiotics. It is particularly important to develop new Lactobacillus strains with superior performance by gene editing. Currently, the identification of its functional genes and the mining of excellent functional genes mainly rely on the traditional gene homologous recombination technology. CRISPR/Cas9-based genome editing is a rapidly developing technology in recent years. It has been widely applied in mammalian cells, plants, yeast, and other eukaryotes, but less in prokaryotes, especially Lactobacillus. Compared with the traditional strain improvement methods, CRISPR/Cas9-based genome editing can greatly improve the accuracy of Lactobacillus target sites and achieve traceless genome modification. The strains obtained by this technology may even be more efficient than the traditional random mutation methods. This review examines the application and current issues of CRISPR/Cas9-based genome editing in Lactobacillus, as well as the development trend of CRISPR/Cas9-based genome editing in Lactobacillus. In addition, the fundamental mechanisms of CRISPR/Cas9-based genome editing are also presented and summarized.