Endogenous indole and its derivatives (indoles), considered as promising N-substituted heterocyclic compounds, are tryptophan metabolites derived from intestinal microbiota and exhibit a range of biological activities. Recent studies indicate that indoles contribute to maintaining the biological barrier of the human intestine, which exert the anti-inflammatory activities mainly through activating AhR and PXR receptors to affect the immune system’s function, significantly improving intestinal health (inflammatory bowel disease, hemorrhagic colitis, colorectal cancer) and further promote human health (diabetes mellitus, central system inflammation, and vascular regulation). However, the revealed toxic influences cannot be ignored. Indoxyl sulfate, an indole derivative, performs nephrotoxicity and cardiovascular toxicity. We addressed the interaction between indoles and intestinal microbiota and the indoles’ effects on human health as double-edged swords. This review provides scientific bases for the correlation of indoles with diseases moreover highlights several directions for subsequent indoles-related studies.

Imbalance of gut microbiota homeostasis is related to the occurrence of ulcerative colitis (UC), and probiotics are thought to modulate immune microenvironment and repair barrier function. Here, in order to reveal the interaction between UC and gut microbiota, we screened a new probiotic strain by 16S rRNA sequencing from Dextran Sulfate Sodium (DSS)-induced colitis mice, and explored the mechanism and clinical relevance. Lactobacillus johnsonii (L. johnsonii), as a potential anti-inflammatory bacterium was decreased colonization in colitis mice. Gavage L. johnsonii could alleviate colitis by specifically increasing the proportion of intestinal macrophages and the secretion of Il-10 with macrophages depleted model and in Il10^−/− mice. We identified this subset of immune cells activated by L. johnsonii as CD206⁺ macrophages^IL−10. Mechanistically, L. johnsonii supplementation enhanced the mobilization of CD206⁺ macrophages^IL−10 through the activation of STAT3 in vivo and in vitro. In addition, we revealed that TLR1/2 was essential for the activation of STAT3 and the recognition of L. johnsonii by macrophages. Clinically, there was positive correlation between the abundance of L. johnsonii and the expression level of MRC1, IL10 and TLR1/2 in UC tissues. L. johnsonii could activate native macrophages into CD206⁺ macrophages and release IL-10 through TLR1/2-STAT3 pathway to relieve experimental colitis. L. johnsonii may serve as an immunomodulator and anti-inflammatory therapeutic target for UC.

The gut microbiota and host immune response interaction influences the progression of intestinal inflammatory disease. As a well-recognized next-generation probiotic, Akkermansia muciniphila has been proved to play a crucial role in the progression of colitis, but its underlying mechanism remains inconclusive.

Background: Soil microorganisms are mainly responsible for the complete mineralization of aromatic compounds that usually originate from plant products or environmental pollutants. In many cases, structurally diverse aromatic compounds can be converted to a small number of structurally simpler intermediates, which are metabolized to tricarboxylic acid intermediates via the β-ketoadipate pathway. This strategy provides great metabolic flexibility and contributes to increased adaptation of bacteria to their environment. However, little is known about the evolution and regulation of the β-ketoadipate pathway in root-associated diazotrophs.Results: In this report, we performed a genome-wide analysis of the benzoate and 4-hydroxybenzoate catabolic pathways ofPseudomonas stutzeriA1501, with a focus on the functional characterization of the β-ketoadipate pathway. TheP. stutzeriA1501 genome contains sets of catabolic genes involved in the peripheral pathways for catabolism of benzoate (ben) and 4-hydroxybenzoate (pob), and in the catechol (cat) and protocatechuate (pca) branches of the β-ketoadipate pathway. A particular feature of the catabolic gene organization in A1501 is the absence of thecatRandpcaKgenes encoding a LysR family regulator and 4-hydroxybenzoate permease, respectively. Furthermore, the BenR protein functions as a transcriptional activator of thebenoperon, while transcription from thecatBCpromoter can be activated in response to benzoate. Benzoate degradation is subject to carbon catabolite repression induced by glucose and acetate in A1501. The HPLC analysis of intracellular metabolites indicated that low concentrations of 4-hydroxybenzoate significantly enhance the ability of A1501 to degrade benzoate.Conclusions: The expression of genes encoding proteins involved in the β-ketoadipate pathway is tightly modulated by both pathway-specific and catabolite repression controls in A1501. This strain provides an ideal model system for further study of the evolution and regulation of aromatic catabolic pathways.

Lactic acid bacteria (LAB) exopolysaccharides (EPSs) have garnered significant scientific interest due to their multifaceted roles in food technology and health promotion. This comprehensive review systematically examines the structural classification of LAB EPSs, emphasizing distinctions between homo-and heteropolysaccharides, as well as the influence of substituent groups (e. g., acetyl, phosphate) on their physicochemical and bioactive properties. Advanced isolation methodologies, including ethanol precipitation and ultrafiltration, coupled with characterization techniques such as nuclear magnetic resonance (NMR) spectroscopy and atomic force microscopy (AFM), are vital for deciphering their chemical and physical characteristics. The biosynthesis pathway, governed by eps operons and modulated by environmental factors (e.g., carbon sources, Ca²⁺), are discussed as targets for genetic engineering to enhance yield and functionality. Functionally, LAB EPSs display antioxidant, immunomodulatory, anti-tumor, anti-viral, and anti-biofilm activities, with demonstrated applications as natural additives in the food industry, prebiotics, and drug delivery systems. Despite their potential, challenges such as cost-effective production and regulatory hurdles persist. Future research should prioritize the elucidation of molecular mechanisms, clinical validation of health claims, and sustainable bioprocessing innovations to fully harness the transformative potential of LAB EPSs across food, pharmaceutical, and agricultural industries.

The potential impacts of methanol extract from Polygonatum odoratum on (YZM) colonic histopathology, gut gas production, short-chain fatty acids (SCFAs), and intestinal microbiota composition were evaluated with dextran sulfate sodium (DSS)-induced colitis mice in this study. These results indicated that YZM increased colon length and ameliorated colonic histopathology in DSS-induced colitis mice. Moreover, YZM administration reversed intestinal microbiota compositions leading to the inhibition of H₂S-related bacteria (e.g., Desulfovibrionaceae) and the lower level of H₂S and higher contents of SCFA-related bacteria (e.g., Muribaculaceae). Taken together, the effects of methanol extract from Polygonatum odoratum are studied to provide new enlightenment and clues for its application as a functional food and clinical drug. Our study first revealed the relationship between intestinal gas production and key bacteria in ulcerative colitis.