Bifidobacterial Dialogue With Its Human Host and Consequent Modulation of the Immune System

Abstract

Since bifidobacteria are among the pioneering colonizers of the human infant gut, their interaction with their host is believed to start soon following birth. Several members of the Bifidobacterium genus are purported to exert various health-promoting effects at local and systemic levels, e.g., limiting pathogen colonization/invasion, influencing gut homeostasis, and influencing the immune system through changes in innate and/or adaptive immune responses. This has promoted extensive research efforts to shed light on the precise mechanisms by which bifidobacteria are able to stimulate and interact with the host immune system. These studies uncovered a variety of secreted or surface-associated molecules that act as essential mediators for the establishment of a bifidobacteria-host immune system dialogue, and that allow interactions with mucosa-associated immune cells. Additionally, the by-products generated from bifidobacterial carbohydrate metabolism act as vectors that directly and indirectly trigger the host immune response, the latter by stimulating growth of other commensal microorganisms such as propionate- or butyrate-producing bacteria. This review is aimed to provide a comprehensive overview on the wide variety of strategies employed by bifidobacteria to engage with the host immune system.

Catching a glimpse of the bacterial gut community of companion animals: a canine and feline perspective

“…Despite this limitation in performing a straightforward comparison between findings of different studies, key bacterial players have transversely been found in feline and canine faeces in different studies, regardless of the metagenomic approaches used. Specifically, Fusobacteria, Bacteroidetes and Firmicutes were identified as the predominant and prevalent bacterial phyla characterizing the faecal microbiota of dogs and cats (Ritchie et al ., 2010; Handl et al ., 2011; Minamoto et al ., 2012; Tun et al ., 2012; Alessandri et al ., 2019a–c). Within the Firmicutes phylum, Bacilli, Clostridia and Erysipelotrichi are the most representative bacterial classes for both canine and feline gut microbiota.…”

“…In addition, the observation that differences in the proportion of macronutrients in the canine and feline diet cause gut microbiota compositional changes was confirmed from a functional point of view. Indeed, a shotgun metagenomics analysis involving a faecal sample per group of diet (commercial diet vs. BARF) revealed a higher abundance of GH families involved in the breakdown of complex plant‐derived polysaccharides being associated with a commercial food diet, while a greater proportion of genes involved in amino acid degradation and fatty acid/lipid degradation pathways was observed in the faecal samples from dog fed on a diet of raw meat (Alessandri et al ., 2019a–c). In parallel, the RMBD was shown to play a role in modulating the intestinal metabolome as a BARF‐based diet causes an increase in faecal cholesterol and other metabolites, such as isomaltose, the inhibitory neurotransmitter gamma‐aminobutyric acid (GABA) and its precursor gamma‐hydroxybutyric acid (GHB; Schmidt et al ., 2018).…”

“…In this milieu, dietary shifts, antibiotic exposure, reduced contact with nature and a concomitant close interaction with humans are only some of the multiple substantial changes imposed by domestication that may have impacted on the intestinal microbial community of animals (Ferrario et al ., 2017; McKenzie et al ., 2017). A recent study investigated the effects of artificial selection and close contact with humans on canine gut microbiota, comparing the 16S rRNA gene sequencing‐based core gut microbiota of dogs with that of humans and wolves (Alessandri et al ., 2019a–c). This comparison highlighted that while six bacterial genera belonging to the core gut microbiota of wolves, i.e.…”

Metatranscriptomic analysis to define the Secrebiome, and 16S rRNA profiling of the gut microbiome in obesity and metabolic syndrome of Mexican children

“…Other enzymes such as N-acylated homoserine lactone (AHL)-lactonase help modulate the structure of the microbiota by decreasing the quorum-sensing of pathogenic bacteria [19]. Several secreted proteins act as essential mediators for the establishment of a bifidobacteria-host immune system dialogue [20]. However, no study has been conducted to examine the total secretome of the gut microbiota, and most importantly, what is the expressed secretome codified in the metatranscriptome of the human gut microbiome.…”

Microbiota and Cancer: The Emerging Beneficial Role of Bifidobacteria in Cancer Immunotherapy

“…Bifidobacteria are among those bacteria that are currently widely used as probiotics and that are capable of interacting with the immune system (Villeger et al, 2019). A growing number of studies have highlighted bifidobacteria as commensal organisms capable of stimulating and modulating specific pathways, through which they influence the host immune responses, both innate and adaptive (Palmer et al, 2007;Arboleya et al, 2016;Hidalgo-Cantabrana et al, 2017;Pickard et al, 2017;Ruiz et al, 2017;Alessandri et al, 2019). In fact, various strains of Bifidobacterium individually or in combination with other strains have been evaluated as probiotics for different diseases and some of these have shown quite promising results in alleviating the symptoms of IBD, IBS, diarrhoa and allergy (Tojo et al, 2014).…”