Merle Rätsep

The aim of this study was to compare the human intestinal microbiota in different age groups, elucidating the precise stages of life in which the gut microbiota evolves its specific characteristics in terms of composition and diversity, as well as associating different bacterial groups for prediction of their intertwined metabolic role, considering their importance in human health. The quantitative composition, Bacteroidetes/Firmicutes (B/F) ratio, counts and diversity indices of faecal samples obtained from infant, child, adult and elderly individuals were assessed via quantitative real-time polymerase chain reaction (qPCR). The intestinal microbiota of infants expressed the highest B/F ratio and diversity. The total bacteria counts, Bacteroides-Prevotella and Blautia coccoides-Eubacterium rectale groups were the most abundant in adults and infants, while child and elderly individuals presented the highest counts of Firmicutes and Lactobacillus sp. In infants, the counts of Enterococcus sp., Streptococcus sp., Enterobacteriaceae, Veillonella sp. and Clostridium perfringens groups were higher, when compared to the other age groups. The tightest positive correlations between bacteria within age groups were found for the B. coccoides-E. rectale, C. leptum (incl. Faecalibacterium prausnitzii), Bacteroidetes-Prevotella and Atopobium groups. Through the stages of life, the quantitative composition and diversity of intestinal microbiota evolves with two changing maximal peaks of predominant groups, with bacterial diversity decreasing from infant to child stage, showing unitary stabilization in adults and presenting a wide individual range in the elderly. The high counts of Bacteroidetes and Clostridium from the phylum Firmicutes, present throughout all life stages, mainly influence the composition and metabolic activity of other bacteria. Recognizing age-specific differences may provide a basis for comparing different geographic populations and predicting the intertwined metabolites of various bacteria, which have certain implications for health.

Representatives of the genus Bifidobacterium are widely used as probiotics to modulate the gut microbiome and alleviate various health conditions. The action mechanisms of probiotics rely on their direct effect on the gut microbiota and the local and systemic effect of its metabolites. The main purpose of this animal experiment was to assess the biosafety of the Bifidobacterium longum strain BIOCC1719. Additional aims were to characterise the influence of the strain on the intestinal microbiota and the effect on several health parameters of the host during 15- and 30-day oral administration of the strain to mice. The strain altered the gut microbial community, thereby altering luminal short-chain fatty acid metabolism, resulting in a shift in the proportions of acetic, butyric, and propionic acids in the faeces and serum of the test group mice. Targeted metabolic profiling of serum revealed the possible ability of the strain to positively affect the hosts’ amino acids and bile acids metabolism, as the cholic acid, deoxycholic acid, aspartate, and glutamate concentration were significantly higher in the test group. The tendency to increase anti-inflammatory polyamines (spermidine, putrescine) and neuroprotective 3-indolepropionic acid metabolism and to lower uremic toxins (P-cresol-SO₄, indoxyl-SO₄) was registered. Thus, B. longum BIOCC1719 may exert health-promoting effects on the host through modulation of the gut microbiome and the host metabolome via inducing the production of health-promoting bioactive compounds. The health effects of the strain need to be confirmed in clinical trials with human volunteers.

Postbiotics are gaining increasing interest among the scientific community as well as at the level of food processing enterprises. The aim of this preliminary study was to characterise the metabolic diversity of a novel Bifidobacterium longum strain, BIOCC 1719, of human origin. The change after 24 h cultivation in three media was assessed using a metabolomic approach. Milk-based substrates favoured the activity of the strain, promoting the production of B vitamins, essential amino acids, bile acids, and fatty acids. Vitamins B1, B2, B6, B7, and B12 (with an average increase of 20–30%) were produced in both whole milk and whey; the increased production in the latter was as high as 100% for B7 and 744% for B12. The essential amino acids methionine and threonine were produced (>38%) in both milk and whey, and there was an increased production of leucine (>50%) in milk and lysine (126%) in whey. Increases in the content of docosahexaenoic acid (DHA) by 20%, deoxycholic acid in milk and whey (141% and 122%, respectively), and cholic acid (52%) in milk were recorded. During the preliminary characterisation of the metabolic diversity of the novel B. longum strain, BIOCC 1719, we identified the bioactive compounds produced by the strain during fermentation. This suggests its potential use as a postbiotic ingredient to enrich the human diet.