We demonstrated that rifaximin, while not altering the overall structure of the human colonic microbiota, increased bifidobacteria and led to variation of metabolic profiles associated with potential beneficial effects on the host.

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Considering the increase in the consumption of yeasts as human probiotics, the aim of this study was to broadly investigate the beneficial properties of the lactic yeast Kluyveromyces marxianus (formerly Kluyveromyces fragilis) B0399. Several potential probiotic traits of K. marxianus B0399 were investigated by using in vitro assays, including adhesion and immune modulation, and the effect of the administration of 10 7 CFU/day of K. marxianus B0399 on the composition and metabolic activity of the human intestinal microbiota was investigated in a 3-stage continuous-culture system simulating the human colon. We demonstrated that this strain was highly adhesive to human enterocyte-like Caco-2 cells and modulated the immune response, inducing proinflammatory cytokines in peripheral blood mononuclear cells (PBMCs). In the presence of inflammatory stimulation with lipopolysaccharide (LPS), K. marxianus B0399 provoked decreases in the levels of production of proinflammatory cytokines in PBMCs and Caco-2 cells, thus ameliorating the inflammatory response. Furthermore, K. marxianus B0399 impacted the colonic microbiota, increasing the bifidobacterial concentration in the stages of the colonic model system simulating the proximal and transverse colon. The amounts of the short-chain fatty acids acetate and propionate also increased following yeast supplementation. Finally, K. marxianus B0399 was found to induce a decrease of the cytotoxic potential of the culture supernatant from the first stage of the colonic model system. The effects of K. marxianus B0399 on adhesion, immune function, and colonic microbiota demonstrate that this strain possesses a number of beneficial and strain-specific properties desirable for a microorganism considered for application as a probiotic.

The human gastrointestinal tract harbors the most complex human microbial ecosystem (intestinal microbiota). The comprehensive genome of these microbial populations (intestinal microbiome) is estimated to have a far greater genetic potential than the human genome itself. Correlations between changes in composition and activity of the gut microbiota and common disorders, such as inflammatory bowel diseases, obesity, diabetes, and atopic diseases, have been proposed, increasing the interest of the scientific community in this research field. In this perspective, a comprehensive and detailed view of the human gut microbiota, in terms of phylogenetic composition as well as genetic and metabolic potential, is essential to understand the dynamics and possible mechanisms of the cause/effect relationships between gut microbiota and pathology. Metagenomics has emerged as one of the most powerful sequence-driven approaches to study the composition and the genetic potential of this complex ecosystem, and efforts in this direction have been smoothed by the implementation of next generation sequencing platforms. Here, we highlight the potential of the newest high-throughput, culture-independent approaches for the characterization of the human gut microbiome in health and disease. Recent and promising results in this field are presented, underlining the perspectives and future research direction of human gut microbial ecology.

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Our findings support the utilization of the tested ingredients in the development of a variety of potentially prebiotic food products aimed at improving gastrointestinal health.

The emerging dynamic dimensions of the human intestinal microbiota (IM) are challenging the traditional definition of healthy gut microbiota, principally based on the static concepts of phylogenetic and functional core. On the other hand, recent researches are revealing that the microbiota plasticity is strategic for several aspects of our biology, addressing the different immunological and metabolic needs at various ages, and adjusting the ecosystem services in response to different lifestyle, physiological states or diets. In light of these studies, we propose to revise the traditional concept of healthy human IM, including its degree of plasticity among the fundamental requisites for providing host health. In order to make a model taking into account the relative importance of IM core functions and plasticity for the maintenance of host health, we address to Economics, where the efficiency of a productive system is measured by computing static and dynamic parameters.