The gut microbiota adapts to age-related changes in host physiology but is also affected by environmental stimuli, like diet. As a source of both pre- and probiotics, dairy and fermented foods modulate the gut microbiota composition, which makes them interesting food groups to use for the investigation of interactions between diet and ageing. Here we present the effects of excluding dairy products and limiting fermented food consumption for 19 days on gut microbiota composition and circulating metabolites of 28 healthy, young (YA) and older (OA) adult men. The intervention affected gut microbial composition in both groups, with significant increases in Akkermansia muciniphila and decreases in bacteria of the Clostridiales order. Lower fasting levels of glucose and insulin, as well as dairy-associated metabolites like lactose and pentadecanoic acid, were observed after the intervention, with no effect of age. The intervention also decreased HDL and LDL cholesterol levels. Dairy fat intake was positively associated with the HDL cholesterol changes but not with the LDL/HDL ratio. In conclusion, restricting the intake of dairy and fermented foods in men modified their gut microbiota and blood metabolites, while the impact of the dietary restrictions on these outcomes was more marked than the effect of age.

Purpose Milk-derived free fatty acids (FFAs) may act as both biomarkers of intake and metabolic effect. In this study we explored associations between different types of dairy consumption, a selection of milk-derived free fatty acids, and cardiometabolic disease (CMD) risk factors. Methods Sixty-seven FFAs were quantified in the plasma of 131 free-living Dutch adults (median 60 years) using gas chromatography-flame ionization detector. Intakes of different dairy foods and groups were assessed using a food frequency questionnaire. Twelve different CMD risk factors were analyzed. Multiple linear regressions were used to evaluate the associations under study. Results Based on the fully adjusted models, 5 long-chain unsaturated FFAs (C18:1 t13 + c6 + c7 + u, C18:2 c9t11 + u, C20:1 c11, C20:3 c8c11c14, and C20:4 c5c8c11c14), 2 medium-chain saturated FFAs (C15, C15 iso), and a trans FFA (C16:1 t9) were positively associated with at least one variable of dairy intake, as well as plasma total and LDL cholesterol, blood pressure, and SCORE (p ≤ 0.05). A long-chain PUFA associated with high-fat fermented dairy intake (C18:2 t9t12), was negatively associated with serum triglyceride levels, and a long-chain saturated FFA associated with cheese intake (C18:1 u1) was negatively associated with plasma LDL cholesterol and serum triglyceride levels. No clear associations were observed between dairy intake and CMD risk factors. Conclusion Milk-derived FFAs could act as sensitive biomarkers for dairy intake and metabolism, allowing the association between dairy and CMD risk to be more precisely evaluated.

A novel, facultatively anaerobic, Gram-stain-positive, motile, endospore-forming bacterium of the genus Paenibacillus , designated strain 2.1T, was isolated from a colony of Apis mellifera affected by European foulbrood disease in Switzerland. The rod-shaped cells of strain 2.1T were 2.2–6.5 µm long and 0.7–1.1 µm wide. Colonies of strain 2.1T were orange-pigmented under oxic growth conditions on solid basal medium at 35–37 °C. Strain 2.1T showed catalase and cytochrome c oxidase activity. Its polar lipid profile consisted of diphosphatidylglycerol, phosphatidylglycerol, phosphatidylethanolamine, aminophospholipid and phospholipid. The only respiratory quinone was menaquinone 7, and the major cellular fatty acids were anteiso-C15 : 0, anteiso-C17 : 0, iso-C15 : 0, iso-C17 : 0 and palmitic acid (C16 : 0), which is consistent with other members of the genus Paenibacillus . The G+C content of the genomic DNA of strain 2.1T was 53.3 mol%. Phylogenetic analyses based on the 16S rRNA gene sequence similarity showed that strain 2.1T was closely related to Paenibacillus dendritiformis LMG 21716T (99.7 % similarity) and Paenibacillus thiaminolyticus DSM 7262T (98.8 %). The whole-genome average nucleotide identity between strain 2.1T and the type strains of P. dendritiformis and P. thiaminolyticus was 92 and 91 %, respectively, and thus lower than the 95 % threshold value for delineation of genomic prokaryotic species. Based on the results of phylogenetic, genomic, phenotypic and chemotaxonomic analyses we propose the name Paenibacillus melissococcoides sp. nov. for this novel Paenibacillus species. The type strain is 2.1T (=CCOS 2000T=DSM 113619T=LMG 32539T).