Inbred mouse strains provide phenotypic homogeneity between individual mice. However, stochastic morphogenetic events combined with epigenetic changes due to exposure to environmental factors and ontogenic experience result in variability among mice with virtually identical genotypes, reducing the reproducibility of experimental mouse models. Here we used microscopic and cytometric techniques to identify individual patterns in gut-associated lymphoid tissue (GALT) that are induced by exposure to microbiota. By comparing germ-free (GF), conventional (CV) and gnotobiotic mice colonized with a defined minimal mouse microbiota (oMM12) MHC II-EGFP knock-in mice we quantified antigen-presenting cells (APCs) in the lamina propria, cryptopatches (CP), isolated lymphoid follicles (ILFs), Peyer's patches (PPs) and specific sections of the mesenteric lymphoid complex. We found that GF mice had a significantly larger outer intestinal surface area compared to CV and oMM12-colonized mice, which partially compensated for their lower density of the villi in the distal ileum. GF mice also contained fewer APCs than oMM12 mice in the Iamina propria of the villi and had a significantly smaller volume of the solitary intestinal lymphoid tissue (SILT). In both GF and oMM12 mice, PP follicles were significantly smaller compared to CV mice, although number was similar. Concomitantly, the number of pDCs in PPs was significantly lower in GF mice than in CV mice. Moreover, the cecal patch was dispersed into small units in GF mice whereas it was compact in CV mice. Taken together, we here provide further evidence that microbiota regulates SILT differentiation, the size and morphology of PPs, the cellular composition of mesenteric lymph nodes (MLNs) and the morphology of cecal patch. As such, microbiota directly affect not only the functional configuration of the immune system but also the differentiation of lymphoid structures. These findings highlight how standardized microbiota, such as oMM12, can promote reproducibility in animal studies by enabling microbiologically controlled experiments across laboratories.

• Keywords
• Germ-free and gnotobiotic models, Gut-associated lymphoid tissue (GALT), Lymphoid tissue morphogenesis, MHCII-EGFP knock-in mice, Microbiota-induced immunity, Phenotypic plasticity,
• MeSH
• Antigen-Presenting Cells immunology   MeSH
• Germ-Free Life MeSH
• Lymphoid Tissue * immunology   cytology   microbiology   MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Peyer's Patches immunology   cytology   MeSH
• Gastrointestinal Microbiome * immunology   MeSH
• Intestinal Mucosa immunology   microbiology   cytology   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH

A balanced microbiota is a main prerequisite for the host's health. The aim of the present work was to develop defined pig microbiota (DPM) with the potential ability to protect piglets against infection with Salmonella Typhimurium, which causes enterocolitis. A total of 284 bacterial strains were isolated from the colon and fecal samples of wild and domestic pigs or piglets using selective and nonselective cultivation media. Isolates belonging to 47 species from 11 different genera were identified by MALDI-TOF mass spectrometry (MALDI-TOF MS). The bacterial strains for the DPM were selected for anti-Salmonella activity, ability to aggregate, adherence to epithelial cells, and to be bile and acid tolerant. The selected combination of 9 strains was identified by sequencing of the 16S rRNA gene as Bacillus sp., Bifidobacterium animalis subsp. lactis, B. porcinum, Clostridium sporogenes, Lactobacillus amylovorus, L. paracasei subsp. tolerans, Limosilactobacillus reuteri subsp. suis, and Limosilactobacillus reuteri (two strains) did not show mutual inhibition, and the mixture was stable under freezing for at least 6 months. Moreover, strains were classified as safe without pathogenic phenotype and resistance to antibiotics. Future experiments with Salmonella-infected piglets are needed to test the protective effect of the developed DPM.

• Keywords
• bacterial consortium, gnotobiotic piglets, intestinal pathogens, pig intestinal bacteria, probiotic properties testing,
• Publication type
• Journal Article MeSH

Mus musculus is the classic mammalian model for biomedical research. Despite global efforts to standardize breeding and experimental procedures, the undefined composition and interindividual diversity of the microbiota of laboratory mice remains a limitation. In an attempt to standardize the gut microbiome in preclinical mouse studies, here we report the development of a simplified mouse microbiota composed of 15 strains from 7 of the 20 most prevalent bacterial families representative of the fecal microbiota of C57BL/6J Specific (and Opportunistic) Pathogen-Free (SPF/SOPF) animals and the derivation of a standardized gnotobiotic mouse model called GM15. GM15 recapitulates extensively the functionalities found in the C57BL/6J SOPF microbiota metagenome, and GM15 animals are phenotypically similar to SOPF or SPF animals in two different facilities. They are also less sensitive to the deleterious effects of post-weaning malnutrition. In this work, we show that the GM15 model provides increased reproducibility and robustness of preclinical studies by limiting the confounding effect of fluctuation in microbiota composition, and offers opportunities for research focused on how the microbiota shapes host physiology in health and disease.

• MeSH
• Bacteria classification   genetics   MeSH
• Species Specificity MeSH
• Feces microbiology   MeSH
• Phenotype MeSH
• Germ-Free Life * MeSH
• Metagenomics methods   MeSH
• Mice, Inbred C57BL MeSH
• Mice MeSH
• Specific Pathogen-Free Organisms * MeSH
• Whole Genome Sequencing methods   MeSH
• Gastrointestinal Microbiome genetics   physiology   MeSH
• Body Weight genetics   physiology   MeSH
• Animals MeSH
• Check Tag
• Male MeSH
• Mice MeSH
• Female MeSH
• Animals MeSH
• Publication type
• Journal Article MeSH
• Research Support, Non-U.S. Gov't MeSH
• Research Support, N.I.H., Extramural MeSH