Lacticaseibacillus rhamnosus MS27 Potentially Prevents Ulcerative Colitis Through Modulation of Gut Microbiota

(1) This study explored <i>Lacticaseibacillus rhamnosus</i> MS27, a newly isolated strain, as a potential probiotic candidate for alleviating the onset and severity of ulcerative colitis (UC). (2) <i>L. rhamnosus</i> MS27 was isolated and subjected to biochemical identification, antibiotic sensitivity testing, and antibacterial activity assessment. Dextran sulfate sodium (DSS) colitis model mice were used to evaluate its alleviating effects. In this study, 16S rRNA microbiome and eukaryotes reference transcriptome analyses were conducted to investigate its impact on intestinal microbial ecology and potential molecular mechanisms. (3) <i>L. rhamnosus</i> MS27 exhibits high acid tolerance at pH 3.23 and maintains a high viable bacterial count for 24 h. It can utilize sucrose, lactose, maltose, inulin, esculin, salicin, and mannitol but not raffinose, and it is sensitive to carbenicillin, erythromycin, tetracycline, chloramphenicol, clindamycin, and penicillin. It effectively increases the abundance of beneficial microbes, particularly <i>Akkermansia</i>, <i>Muribaculaceae,</i> and <i>Limosilactobacillus reuteri</i> (<i>p</i> < 0.05), while significantly reducing microorganisms linked to human pathogens causing diarrhea and gastroenteritis (<i>p</i> < 0.05). Transcriptomic analysis demonstrated that the expression levels of <i>Igkv16-104</i> and <i>C1qtnf3</i> were significantly downregulated in the presence of <i>L. rhamnosus</i> MS27 treatment compared to DSS treatment alone (<i>p</i> < 0.05). Further analysis revealed significant differences in genes related to immune functions, antigen presentation, and immune cell markers, indicating potential protein-protein interaction networks, particularly among genes of the major histocompatibility complex (MHC). (4) <i>L. rhamnosus</i> MS27, as a novel strain, demonstrates a significant capacity to alleviate inflammatory phenotypes. <i>L. rhamnosus</i> MS27 exhibits distinctive metabolic characteristics in lactic acid utilization, acetic acid and oleic acid production. Furthermore, it contributes to systemic homeostasis regulation by modulating <i>Turicibacter</i> to link intestinal microbiota composition with host immune function.