Abstract
Comprehensive study of the biological activity of structural components and metabolites of “beneficial” microorganisms opens the prospects of efficient and rational use of their biotechnological potential in the correction of microecological and related disorders. The study tested proliferative activity and biofilm formation by Bifidobacterium bifidum probiotic strain under the influence of cell-free extracts containing structural components and metabolites of the probiotic strains of B. bifidum and Lactobacillus reuteri. Cell-free extracts were obtained by disintegrating suspensions of probiotic cells by cyclic freezing-thawing, cultivating probiotic microorganisms in their own disintegrates and subsequent filtration of the obtained disintegrates and cultures. The proliferative activity and biofilm formation of the probiotic test culture were studied by spectrophotometric microtiter plate method with 10%vol, 30%vol and 50%vol content of cell-free extracts in the cultivation medium. All investigated extracts showed a significant concentration-dependent stimulatory effect on the proliferative activity of B. bifidum. According to the degree of stimulatory effect on the B. bifidum proliferation, cell-free extracts arranged in ascending order: MLG (filtrate of L. reuteri culture, grown in L. reuteri disintegrate supplemented with 0.8 M glycerol and 0.4 M glucose) < MB (filtrate of В. bifidum culture, grown in В. bifidum disintegrate) < B (filtrate of В. bifidum disintegrate) < ML (filtrate of L. reuteri culture, grown in L. reuteri disintegrate) < L (filtrate of L. reuteri disintegrate). With the same content in the culture medium, filtrates of disintegrates had a more pronounced stimulatory effect than filtrates of cultures grown in their own disintegrates. Cell-free extracts from L. reuteri (L and ML) exerted a more pronounced stimulatory effect than cell-free extracts from B. bifidum. Not all studied cell-free extracts stimulated the biofilm formation by B. bifidum. The effect of cell-free extracts on this process depended on their type and concentration. Extract L had a predominantly inhibitory effect on biofilm formation by B. bifidum. The most pronounced stimulatory effect on biofilm formation by B. bifidum came from extract MLG. ML, B and MB extracts stimulated this process approximately equally. The detection of significant bifidogenic effect of the studied cell-free extracts may contribute to their pharmaceutical applications. Cell-free extracts can be used as metabiotics or prebiotics for increasing the survival of the injected probiotic, facilitating its inoculation in the gastrointestinal tract when used together. The obtained data encourage further careful study of the biochemical composition of cell-free extracts and efforts to clarify the mechanism of their action.
Highlights
The gut microbiota is involved in a wide variety of physiological processes: degradation of non-digestible food compounds, absorption of nutrients, metabolism of bile acids and xenobiotics, production of essential vitamins, bioactive metabolites and signaling molecules
It should be noted that an increase in the volume of the physiological saline (PhS) replacing the nutrient medium in the control sample from 10% to 30% and from 10% to 50%, is accompanied by a decrease in the optical density gain of the culture by an average of 17% and 73.6%, respectively (Fig. 1)
Addition to the cultivation medium of L and MLcell-free extracts at a concentration of 10% leads to a significant increase in the optical density gain of the culture compared to PC10
Summary
The gut microbiota is involved in a wide variety of physiological processes: degradation of non-digestible food compounds, absorption of nutrients, metabolism of bile acids and xenobiotics, production of essential vitamins, bioactive metabolites and signaling molecules. It has a strong influence on the intestinal epithelium and immune system development, host behaviour and metabolism. Bifidobacterium bifidum, B. longum and B. breve are the predominant microbes that colonize the intestine in the first days after birth They constitute 40–80% of the gut microbiota of newborns. The loss of bifidobacteria is harmful for the health of the host: it adversely affects the remaining microorganisms, increases the risk of invasion and colonization of the gut epithelium by pathogenic and opportunistic microorganisms (Sarkar & Mandal, 2016; Rivière et al, 2016; O’Neillet al., 2017)
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