Journal of Microbiology

Volume 56(3); March 2018

Editorial

EDITORIAL] Gut microbiomes and their metabolites shape human and animal health: Woojun Park; J. Microbiol. 2018;56(3):151-153.; DOI: https://doi.org/10.1007/s12275-018-0577-8

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45 Citations

Abstract: The host genetic background, complex surrounding environments, and gut microbiome are very closely linked to human and animal health and disease. Although significant correlations between gut microbiota and human and animal health have been revealed, the specific roles of each gut bacterium in shaping human and animal health and disease remain unclear. However, recent omics-based studies using experimental animals and surveys of gut microbiota from unhealthy humans have provided insights into the relationships among microbial community, their metabolites, and human and animal health. This editorial introduces six review papers that provide new discoveries of disease-associated microbiomes and suggest possible microbiome-based therapeutic approaches to human disease.

Reviews

REVIEW] Intestinal microbiota and the immune system in metabolic diseases: Panida Sittipo , Stefani Lobionda , Yun Kyung Lee , Craig L. Maynard; J. Microbiol. 2018;56(3):154-162. Published online February 28, 2018; DOI: https://doi.org/10.1007/s12275-018-7548-y

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91 Citations

Abstract: The intestinal microbiota is comprised of millions of microorganisms that reside in the gastrointestinal tract and consistently interact with the host. Host factors such as diet and disease status affect the composition of the microbiota, while the microbiota itself produces metabolites that can further manipulate host physiology. Dysbiosis of the intestinal microbiota has been characterized in patients with certain metabolic diseases, some of which involve damage to the host intestinal epithelial barrier and alterations in the immune system. In this review, we will discuss the consequences of dietdependent bacterial dysbiosis in the gastrointestinal tract, and how the associated interaction with epithelial and immune cells impacts metabolic diseases.

REVIEW] Type 3 regulatory T cells at the interface of symbiosis: Joo-Hong Park , Gérard Eberl; J. Microbiol. 2018;56(3):163-171. Published online February 28, 2018; DOI: https://doi.org/10.1007/s12275-018-7565-x

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22 Citations

Abstract: The mammalian gastrointestinal tract accommodates trillions of bacteria, many of which provide beneficial effects to the host, including protection from pathogenic microorganisms and essential metabolites. However, the intestinal immune system needs to adapt to the constantly fluctuating microbial environment at mucosal surfaces in order to maintain homeostasis. In particular, the gut microbiota induces the differentiation of effector Th17 cells and regulatory T cells (Tregs) that express RORγt, the master regulator of antimicrobial type 3 immunity. RORγt+ Tregs constitute a major population of colonic Tregs that is distinct from thymusderived Tregs and require bacterial antigens for differentiation. The balance between Th17 cells and RORγt+ Tregs, that is, the tone of the local type 3 immune response, is regulated by the vitamin A metabolite retinoic acid produced by the host. Furthermore, Th17 cells and RORγt+ Tregs regulate intestinal type 2 immune responses, explaining how bacteria block allergic reactions. Here, we review the cellular and molecular mechanisms involved in the differentiation, regulation and function of RORγt+ (type 3) Tregs, and discuss the multiple equilibria that exist between effector T cells and Tregs, as well as between different types of immune responses, which are necessary to maintain homeostasis and health.

REVIEW] Mind-altering with the gut: Modulation of the gut-brain axis with probiotics: Namhee Kim , Misun Yun , Young Joon Oh , Hak-Jong Choi; J. Microbiol. 2018;56(3):172-182. Published online February 28, 2018; DOI: https://doi.org/10.1007/s12275-018-8032-4

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144 Citations

Abstract: It is increasingly evident that bidirectional interactions exist among the gastrointestinal tract, the enteric nervous system, and the central nervous system. Recent preclinical and clinical trials have shown that gut microbiota plays an important role in these gut-brain interactions. Furthermore, alterations in gut microbiota composition may be associated with pathogenesis of various neurological disorders, including stress, autism, depression, Parkinson’s disease, and Alzheimer’s disease. Therefore, the concepts of the microbiota-gut-brain axis is emerging. Here, we review the role of gut microbiota in bidirectional interactions between the gut and the brain, including neural, immune-mediated, and metabolic mechanisms. We highlight recent advances in the understanding of probiotic modulation of neurological and neuropsychiatric disorders via the gut-brain axis.

REVIEW] Targeting friend and foe: Emerging therapeutics in the age of gut microbiome and disease: Jin Ah Cho , Daniel J.F. Chinnapen; J. Microbiol. 2018;56(3):183-188. Published online February 28, 2018; DOI: https://doi.org/10.1007/s12275-018-8037-z

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17 Citations

Abstract: Mucosal surfaces that line our gastrointestinal tract are continuously exposed to trillions of bacteria that form a symbiotic relationship and impact host health and disease. It is only beginning to be understood that the cross-talk between the host and microbiome involve dynamic changes in commensal bacterial population, secretion, and absorption of metabolites between the host and microbiome. As emerging evidence implicates dysbiosis of gut microbiota in the pathology and progression of various diseases such as inflammatory bowel disease, obesity, and allergy, conventional treatments that either overlook the microbiome in the mechanism of action, or eliminate vast populations of microbes via wide-spectrum antibiotics need to be reconsidered. It is also becoming clear the microbiome can influence the body’s response to therapeutic treatments for cancers. As such, targeting the microbiome as treatment has garnered much recent attention and excitement from numerous research labs and biotechnology companies. Treatments range from fecal microbial transplantation to precision-guided molecular approaches. Here, we survey recent progress in the development of innovative therapeutics that target the microbiome to treat disease, and highlight key findings in the interplay between host microbes and therapy.

REVIEW] Current understanding of microbiota- and dietary-therapies for treating inflammatory bowel disease: Taekil Eom , Yong Sung Kim , Chang Hwan Choi , Michael J. Sadowsky , Tatsuya Unno; J. Microbiol. 2018;56(3):189-198. Published online February 28, 2018; DOI: https://doi.org/10.1007/s12275-018-8049-8

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87 Citations

Abstract: Inflammatory bowel disease (IBD) is a result of chronic inflammation caused, in some part, by dysbiosis of intestinal microbiota, mainly commensal bacteria. Gut dysbiosis can be caused by multiple factors, including abnormal immune responses which might be related to genetic susceptibility, infection, western dietary habits, and administration of antibiotics. Consequently, the disease itself is characterized as having multiple causes, etiologies, and severities. Recent studies have identified > 200 IBD risk loci in the host. It has been postulated that gut microbiota interact with these risk loci
result
ing in dysbiosis, and this subsequently leads to the development of IBD. Typical gut microbiota in IBD patients are characterized with decrease in species richness and many of the commensal, and beneficial, fecal bacteria such as Firmicutes and Bacteroidetes and an increase or bloom of Proteobacteria. However, at this time, cause and effect relationships have not been rigorously established. While treatments of IBD usually includes medications such as corticosteroids, 5-aminosalicylates, antibiotics, immunomodulators, and anti- TNF agents, restoration of gut dysbiosis seems to be a safer and more sustainable approach. Bacteriotherapies (now called microbiota therapies) and dietary interventions are effective way to modulate gut microbiota. In this review, we summarize factors involved in IBD and studies attempted to treat IBD with probiotics. We also discuss the potential use of microbiota therapies as one promising approach in treating IBD. As therapies based on the modulation of gut microbiota becomes more common, future studies should include individual gut microbiota differences to develop personalized therapy for IBD.

REVIEW] The Ruminococci: key symbionts of the gut ecosystem: Alex J. La Reau , Garret Suen; J. Microbiol. 2018;56(3):199-208. Published online February 28, 2018; DOI: https://doi.org/10.1007/s12275-018-8024-4

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205 Citations

Abstract: Mammalian gut microbial communities form intricate mutualisms with their hosts, which have profound implications on overall health. One group of important gut microbial mutualists are bacteria in the genus Ruminococcus, which serve to degrade and convert complex polysaccharides into a variety of nutrients for their hosts. Isolated decades ago from the bovine rumen, ruminococci have since been cultured from other ruminant and non-ruminant sources, and next-generation sequencing has further shown their distribution to be widespread in a diversity of animal hosts. While most ruminococci that have been studied are those capable of degrading cellulose, much less is known about non-cellulolytic, nonruminant- associated species, such as those found in humans. Furthermore, a mechanistic understanding of the role of Ruminococcus spp. in their respective hosts is still a work in progress. This review highlights the broad work done on species within the genus Ruminococcus with respect to their physiology, phylogenetic relatedness, and their potential impact on host health.

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