Evidence linking Faecalibacterium prausnitzii abundance to nonalcoholic fatty liver disease (NAFLD) is accumulating; however, the causal relationship remains obscure. In this study, 12 F. prausnitzii strains were orally administered to high fat diet fed C57BL/6J mice for 12 weeks to evaluate the protective effects of F. prausnitzii on NAFLD. We found that five F. prausnitzii strains, A2-165, LB8, ZF21, PL45, and LC49, significantly restored serum lipid profiles and ameliorated glucose intolerance, adipose tissue dysfunction, hepatic steatosis, inflammation, and oxidative stress in a mouse model of NAFLD. Moreover, two strains, LC49 and LB8, significantly enhanced short-chain fatty acid (SCFA) production and modulated the gut microbiota. Based on the combined analysis of linear discriminant analysis effect size and microbial communities, the core microbiome related to NAFLD comprised Odoribacter, Roseburia, Erysipelatoclostridium, Tyzzerella, Faecalibaculum, Blautia, and Acetatifactor, and the last five genera can be reversed by treatment with the LC49 and LB8 strains. Additionally, the LC49 and LB8 strains enriched Lactobacillus, Ileibacterium, Faecalibacterium, Dubosiella, and Bifidobacterium and downregulated pathways involving carbohydrate metabolism, amino acid metabolism, and fatty acid biosynthesis. Interestingly, LC49 supplementation also upregulated tryptophan metabolism, glutathione metabolism, and valine, leucine, and isoleucine degradation, which might be related to NAFLD prevention. Collectively, F. prausnitzii LC49 and LB8 exerted considerable anti-NAFLD and microbiota-regulating effects, indicating their potential as probiotic agents for NAFLD treatment.

Psoriasis is an immune-mediated systemic disease that may be treated with probiotics. In this study, probiotic strains that could or could not decrease interleukin (IL)-17 levels were applied to imiquimod (IMQ)-induced psoriasis-like mice via oral administration. Bifidobacterium adolescentis CCFM667, B. breve CCFM1078, Lacticaseibacillus paracasei CCFM1074, and Limosilactobacillus reuteri CCFM1132 ameliorated psoriasis-like pathological characteristics and suppressed the release of IL-23/T helper cell 17 (Th17) axis-related inflammatory cytokines, whereas B. animalis CCFM1148, L. paracasei CCFM1147, and L. reuteri CCFM1040 neither alleviated the pathological characteristics nor reduced the levels of inflammatory cytokines. All effective strains increased the contents of short-chain fatty acids, which were negatively correlated with the levels of inflammatory cytokines. By performing 16S rRNA gene sequencing, the diversity of gut microbiota in psoriasis-like mice was found to decrease, but all effective strains made some specific changes to the composition of gut microbiota compared to the ineffective strains. Furthermore, except for B. breve CCFM1078, all other effective strains decreased the abundance of the family Rikenellaceae, which was positively correlated with psoriasis-like pathological characteristics and was negatively correlated with propionate levels. These findings demonstrated effects of strain-specificity, and how probiotics ameliorated psoriasis and provide new possibilities for the treatment of psoriasis.

Gut bacteria are closely associated with the development of atopic dermatitis (AD) due to their immunoregulatory function. Indole derivatives, produced by gut bacteria metabolizing tryptophan, are ligands to activate the aryl hydrocarbon receptor (AHR), which plays a critical role in attenuating AD symptoms. Limosilactobacillus reuteri, a producer of indole derivatives, regulates mucosal immunity via activating the AHR signaling pathway. However, the effective substance and mechanism of L. reuteri in the amelioration of AD remain to be elucidated. In this research, we found that L. reuteri DYNDL22M62 significantly improved AD-like symptoms in mice by suppressing IgE levels and the expressions of thymic stromal lymphopoietin (TSLP), IL-4, and IL-5. L. reuteri DYNDL22M62 induced an increase in the production of indole lactic acid (ILA) and indole propionic acid (IPA) via targeted tryptophan metabolic analysis and the expression of AHR in mice. Furthermore, L. reuteri DYNDL22M62 increased the proportions of Romboutsia and Ruminococcaceae NK4A214 group, which were positively related to ILA, but decreased Dubosiella, which was negatively related to IPA. Collectively, L. reuteri DYNDL22M62 with the role of modulating gut bacteria and the production of indole derivatives may attenuate AD via activating AHR in mice.

Bifidobacterium bifidum strains, an important component of probiotic foods, can form biofilms on abiotic surfaces, leading to increased self-resistance. However, little is known about the molecular mechanism of B. bifidum biofilm formation. A time series transcriptome sequencing and untargeted metabolomics analysis of both B. bifidum biofilm and planktonic cells was performed to identify key genes and metabolites involved in biofilm formation. Two hundred thirty-five nonredundant differentially expressed genes (DEGs) (including vanY, pstS, degP, groS, infC, groL, yajC, tadB and sigA) and 219 nonredundant differentially expressed metabolites (including L-threonine, L-cystine, L-tyrosine, ascorbic acid, niacinamide, butyric acid and sphinganine) were identified. Thirteen pathways were identified during the integration of both transcriptomics and metabolomics data, including ABC transporters; quorum sensing; two-component system; oxidative phosphorylation; cysteine and methionine metabolism; glutathione metabolism; glycine, serine and threonine metabolism; and valine, leucine and isoleucine biosynthesis. The DEGs that relate to the integration pathways included asd, atpB, degP, folC, ilvE, metC, pheA, pstS, pyrE, serB, ulaE, yajC and zwf. The differentially accumulated metabolites included L-cystine, L-serine, L-threonine, L-tyrosine, methylmalonate, monodehydroascorbate, nicotinamide, orthophosphate, spermine and tocopherol. These results indicate that quorum sensing, two-component system and amino acid metabolism are essential during B. bifidum biofilm formation.

Epidemiological investigation confirmed that the intake of dietary fiber (DF) is closely related to human health, and the most important factor affecting the physiological function of DF, besides its physicochemical properties, is the gut microbiota. This paper mainly summarizes the interaction between DF and gut microbiota, including the influence of DF on the colonization of gut microbiota based on its different physicochemical properties, and the physiological role of gut microbiota in destroying the complex molecular structure of DF by encoding carbohydrate-active enzymes, thus producing small molecular products that affect the metabolism of the host. Taking cardiovascular disease (Atherosclerosis and hypertension), liver disease, and immune diseases as examples, it is confirmed that some DF, such as fructo-oligosaccharide, galactooligosaccharide, xylo-oligosaccharide, and inulin, have prebiotic-like physiological effects. These effects are dependent on the metabolites produced by the gut microbiota. Therefore, this paper further explores how DF affects the gut microbiota’s production of substances such as short-chain fatty acids, bile acids, and tryptophan metabolites, and provides a preliminary explanation of the mechanisms associated with their impact on host health. Finally, based on the structural properties of DF and the large heterogeneity in the composition of the population gut microbiota, it may be a future trend to utilize DF and the gut microbiota to correlate host health for precision nutrition by combining the information from population disease databases.

Faecalibacterium prausnitzii is prevalent in the human gut and is a potential candidate for next-generation probiotics (NGPs) or biotherapeutics. However, the biodiversity and physiological characteristics of Faecalibacterium prausnitzii remain unclear. This study isolated 26 novel F. prausnitzii strains from human feces using a combination of negative screening and prime-specific PCR amplification (NSPA). Based on a 16S rRNA gene analysis, F. prausnitzii strains can be classified into two main phylogroups (phylogroups I and II), which were further clustered into five subgroups (I-A, II-B, II-C, II-D, and II-E). The ultrastructure, colony morphology, growth performance, and short-chain fatty acids (SCFAs)-producing ability were found to be variable among these F. prausnitzii isolates. The optimal pH for the isolates growth ranged between 6.0 and 7.0, while most isolates were inhibited by 0.1% of bile salts. Antimicrobial resistance profiles showed that all F. prausnitzii isolates were susceptible to vancomycin, whereas >80% were kanamycin and gentamicin resistant. Additionally, all strains can utilize maltose, cellulose, and fructose but not xylose, sorbose, and 2′-FL. Overall, our work provides new insights into the biodiversity and physiological characteristics of F. prausnitzii, as well as the choices of strains suitable for NGPs.