Abstract
The gut microbiota is a complex ecological community, consisting of trillions of microbes which include bacteria, viruses, fungi and protozoa. The stomach was previously considered as a sterile site uninhabited by microbes due to its hostile environmental conditions. Breaking this concept, Helicobacter pylori was the first pathogen reported to inhabit the stomach. Recent studies have suggested that the stomach harbours transient as well as certain commensal bacterial and fungal species. The five major microbial phyla in the stomach have been identified as Firmicutes, Bacteroidetes, Actinobacteria, Fusobacteria and Proteobacteria. The composition of gastric microbiota is dynamic and is affected by several factors. These include age group, dietary habits, medication use, inflammation of gastric mucosa and H. pylori colonization. Further, the role of host genetics has recently been studied in maintaining the stomach microbiota. Mutations in host genes may affect the host’s immune response towards commensal bacteria and reduce their number and diversity. The essential multiple roles of gut microorganisms include maintaining homeostasis in the gut, contributing to immune function and extraction of nutrients and energy from our diets. Loss of the normal balance between the gut microbiota and host has been associated with several abnormal conditions and disorders such as obesity, malnutrition, inflammatory bowel diseases (IBD), neurological disorders, and cancer. In the stomach, the interaction between H. pylori and the gastric microbiota can also influence gastric disease progression. Further studies should focus on addressing the role of gastric dysbiosis in health and disease. Identifying gastric microbiota is essential to understand how the gut microbiota and H. pylori affect health and disease.
Highlights
The gut microbiota consists of both commensal and pathogenic organisms residing in the gastrointestinal tract
PCR- and sequencing-based approaches have demonstrated that H. pylori-negative individuals harbor a highly diverse gastric microbiota dominated by the five predominant phyla, Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes and Fusobacteria.[45]
This study reported that the number of viable bacteria declined in the presence of acidic pH.[50]
Summary
The gut microbiota is a complex ecological community, consisting of many microbes which include bacteria and archaea, viruses, fungi and protozoa.[1,2] The gut microbiota consists of both commensal and pathogenic organisms residing in the gastrointestinal tract. The essential role of these microbiota includes nutrient and mineral absorption, immune function, synthesis of vitamins, enzymes and amino acids and production of short chain fatty acids (SCFAs) which are being increasingly elucidated.[3,4] The byproducts, mainly acetate, propionate and butyrate of the fermentation processes by these organisms are important in maintaining the health of the human gut.
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