Bifidobacteria or Fiber Protects against Diet-Induced Microbiota-Mediated Colonic Mucus Deterioration

Mucus: An Underestimated Gut Target for Environmental Pollutants and Food Additives

Synthetic chemicals (environmental pollutants, food additives) are widely used for many industrial purposes and consumer-related applications, which implies, through manufactured products, diet, and environment, a repeated exposure of the general population with growing concern regarding health disorders. The gastrointestinal tract is the first physical and biological barrier against these compounds, and thus their first target. Mounting evidence indicates that the gut microbiota represents a major player in the toxicity of environmental pollutants and food additives; however, little is known on the toxicological relevance of the mucus/pollutant interplay, even though mucus is increasingly recognized as essential in gut homeostasis. Here, we aimed at describing how environmental pollutants (heavy metals, pesticides, and other persistent organic pollutants) and food additives (emulsifiers, nanomaterials) might interact with mucus and mucus-related microbial species; that is, “mucophilic” bacteria such as mucus degraders. This review highlights that intestinal mucus, either directly or through its crosstalk with the gut microbiota, is a key, yet underestimated gut player that must be considered for better risk assessment and management of environmental pollution.

Role of the gut microbiota in nutrition and health

Ana M Valdes and colleagues discuss strategies for modulating the gut microbiota through diet and probiotics

Microbial networking in cancer: when two toxins collide

A recent study by Dejea et al. has demonstrated that two enterotoxigenic bacteria frequently associated with sporadic colorectal cancer, Bacteroides fragilis and pks+ Escherichia coli, are found together in biofilms on tissue from patients with familial adenomatous polyposis. In preclinical mouse models, these two bacteria and their corresponding toxins work synergistically to promote colon cancer.

Commensal Bacteria-Dependent CD8αβ+ T Cells in the Intestinal Epithelium Produce Antimicrobial Peptides

The epithelium of the intestine functions as the primary “frontline” physical barrier for protection from enteric microbiota. Intraepithelial lymphocytes (IELs) distributed along the intestinal epithelium are predominantly CD8⁺ T cells, among which CD8αβ⁺ IELs are a large population. In this investigation, the proportion and absolute number of CD8αβ⁺ IELs decreased significantly in antibiotic-treated and germ-free mice. Moreover, the number of CD8αβ⁺ IELs was correlated closely with the load of commensal microbes, and induced by specific members of commensal bacteria. Microarray analysis revealed that CD8αβ⁺ IELs expressed a series of genes encoding potent antimicrobial peptides (AMPs), whereas CD8αβ⁺ splenocytes did not. The antimicrobial activity of CD8αβ⁺ IELs was confirmed by an antimicrobial-activity assay. In conclusion, microbicidal CD8αβ⁺ IELs are regulated by commensal bacteria which, in turn, secrete AMPs that have a vital role in maintaining the homeostasis of the small intestine.

Antitumor mechanisms of bifidobacteria

Cancer remains one of the most common causes of mortality globally. Chemotherapy, one of the major treatment strategies for cancer, primarily functions by targeting the cancer cells and affecting them physiologically, but also affects normal cells, which is a major concern at present. Therefore, adverse effects of chemotherapy drugs, including myelosuppression and liver and kidney damage, are of concern. Now, microbial products have attracted attention in cancer treatment research. Notably, carcinogenesis is considered to be associated with microbial dysbiosis, particularly the positive antitumor effects of bifidobacteria. Although there remains a substantial amount to be understood about the regulation of bifidobacteria, bifidobacteria remain an attractive and novel source of cancer therapeutics. The present review focuses on introducing the latest information on the antitumor effects of bifidobacteria and to propose future strategies for using bifidobacteria in the development of cancer therapeutics.

Probiotic Species in the Modulation of Gut Microbiota: An Overview

Probiotics are microbial strains that are beneficial to health, and their potential has recently led to a significant increase in research interest in their use to modulate the gut microbiota. The animal gut is a complex ecosystem of host cells, microbiota, and available nutrients, and the microbiota prevents several degenerative diseases in humans and animals via immunomodulation. The gut microbiota and its influence on human nutrition, metabolism, physiology, and immunity are addressed, and several probiotic species and strains are discussed to improve the understanding of modulation of gut microbiota. This paper provides a broad review of several Lactobacillus spp., Bifidobacterium spp., and other coliform bacteria as the most promising probiotic species and their role in the prevention of degenerative diseases, such as obesity, diabetes, cancer, cardiovascular diseases, malignancy, liver disease, and inflammatory bowel disease. This review also discusses a recent study of Saccharomyces spp. in which inflammation was prevented by promotion of proinflammatory immune function via the production of short-chain fatty acids. A summary of gut microbiota alteration with future perspectives is also provided.