Gut Microbiota 3



Thehuman gut microbiota comprises of 1014microorganisms including approximately 1000 different species ofbacteria with more than three million genes (Fraher, O’Toole andQuigley, 2012: 312). Most people have a third of the gut microbiotawhile two-thirds are distinct according to an individual’s geneticcharacteristics. The gut microbiota is an acquired organ becausebabies are born sterile but after birth, the microorganisms from themother quickly occupy the digestive track. After the third day, thecomposition of the intestinal flora is directly dependent on thefeeding mechanism of the baby (Sekirov et al., 2010: 861). However,at three years, the microbiota is established and similar to that ofan adult and continues to develop at a steady rate. The microbiotaregularly changes due to different environmental effects and thediet. The aging process also affects the gut microbiota’sstability. Accordingly, the microbiota of a young adult isconsiderably distinct from that of an elderly.

Thestructure and functional capability of the gut microbiota can bedetermined using different approaches. Traditionally, the gutmicrobiota composition was determined by the culture-based technique(Prakash et al., 2011: 72). The approach focused on the microbes thatwere easy to culture. Although this method is relatively cheap, ithas a significant limitation because only 10 to 50% of gut bacteriacan be cultured. Accordingly, new molecular techniques have beendeveloped to determine the structure and functionality of gutmicrobiota such a ribosomal intergenic spacer analysis and 16Sribosomal rRNA sequencing (Fraher, O’Toole and Quigley, 2012: 314).The new molecular techniques can identify mycobacteria, which canlead to the identification of novel pathogens and non-culturedbacteria. The gut microbiota performs a vital role in the bodyfunctions such as metabolic, protection, structural, andhistological. Thus, they are an essential inhibitor or contributingcause of many diseases that affects human health.

First,the gut microbiota performs important metabolic functions, which canaffect human health. Its metabolic functions include the productionof amino acids, vitamin, and bile acid biotransformation (Prakash etal., 2011: 73). The microbial enzymes carry out bile acidbiotransformation, which influences glucose and cholesterolmetabolism. The microbiota provides biochemical paths required forthe fermentation of endogenous mucus and non-digestible substrates.The fermentation process prompts the growth of bacteria, whichresults in the manufacture of short-chain fatty acids and gasses(Gill et al., 2006: 779). The short-chain fatty acids have a growtheffect on the intestinal epithelium. Bacterial fermentation occurs inthe colon where short-chain fatty acids are absorbed. Hence, itstimulates the absorption of water and salt. Therefore, the gutmicrobiota activities are essential for the metabolism and humanhealth.

Furthermore,gut microbiota provides protection to its hosts by regulating theproduction of immune mediators (Sekirov et al., 2010: 866). The gutmicrobiota uses competitive exclusion to form a physical blockade anddisplace pathogens from attachment nutrients and sites. It alsostimulates the manufacture and secretion of various antimicrobialcompounds. As a result, it lowers the level of lipopolysaccharides,bacterial CpG-DNA motifs, peptidoglycans, and superantigens. If thesechemicals are unregulated, they can harm host. The gut microbiotaenhances the growth of the immune system. A healthy person hasimmature lymphatic structures with less Peyer’s patches andisolated lymphoid follicles. Besides, the intestinal dendritic cellsare fewer in a healthy host, which shows the functions of gutbacteria in the development of B cell. In addition, the gutmicrobiota also influences the T cell repertoire of the intestine bycontrolling the production of chemokines and cytokines (Wu and Lewis,2013: 775). Consequently, it enhances a person’s immune system.

Additionally,the gut microbiota can control the local intestinal immune system.The intestinal microbes can change the gene expression in the gutmucosa eventually influencing the function of the humangastrointestinal tract (GIT). The microbiota controls themanifestation of many genes in the intestinal tract including genesinvolved in energy metabolism, immunity, nutrient absorption, andintestinal barrier function (Guinane and Cotter, 2013: 299). Theprobiotics found in the GIT can also affect systems of geneexpression. The GIT produces the antimicrobial peptides (AMPs) andproteins such as defensins, C-type lectins, and cathelicidins. TheseAMPs have a crucial role in protecting the host against pathogenicbacteria and controls invasion of indigenous microbes. Although theprimary functions of the AMPs are regulating the composition andamount of gut microbiota, the interaction between the microbiota andAMPs is bidirectional. Thus, the products of microbial metabolism andvarious microbial species accelerate the production of differenttypes of AMPs (Vos et al., 2012: 59). Besides, the microbialmetabolites can stimulate AMPs manifestation in vivo and several linecells. As such, it has a significant impact on systemic immuneresponses.

Lastly,the microbiota ensures intestinal function and structure. The mucuslayer creates an obstacle to the absorption of antigens andproinflammatory molecules. According to research, butyrate reinforcesthe colonic defence barrier by inducing the secretion of trefoilfactors, mucins, and antimicrobial peptides (Prakash et al., 2011:74). Some bacterial communities in the gut microbiota strengthen theprotein clusters that create a barrier between the lamina propria andlumen. Furthermore, the gut microbiota is involved in tissue and celldevelopment. Butyrate also regulates the growth and differentiationof cells, prevents distorted cell growth while encouraging thereversal of cells from a neoplastic phenotype to a non-neoplastic.The gut microbiota is also necessary for healthy growth and immunesystem homeostasis in the gut (Sommer and Bäckhed, 2013: 227). Forinstance, an experiment on mice showed that the TLR signals developedfrom the gut microbiota are essential for recovering tissuehomeostasis after an injury in the intestine (Sommer and Bäckhed, 2013: 234).

Nonetheless,it can also affect human health negatively if its composition isaltered. The gut microbiota can adapt to environmental or foodchanges. However, it loses balance in some particular situations dueto environment or diet resulting in dysbiosis. The microbiota ischanged due to variation in microbiota composition, localdistribution communities, or bacterial metabolic activity in thedysbiosis condition (Wu and Lewis, 2013: 777). The varied componentsof the human GIT ecosystem can cause physiological changes in theduodenal environment, which will disrupt the roles of the microbiota.Hence, result in serious consequences for human health. According toresearch, dysbiosis is linked to health problems such as inflammatorybowel disease, obesity, allergies, functional bowel disorders, anddiabetes (Guinane and Cotter, 2013: 295).

Inconclusion, the human body has vast and complex categories ofmicrobes. The gut microbiota can adapt to the environment and diet.It relates to the body’s immune system, and they elicit specificimmune responses, which affect human health. The gut microbiotaperforms necessary roles in the maintenance of health such asstructural, metabolic, and protective. Some of its vital metabolicfunctions include the production of vitamins, biosynthesis of aminoacids, bile acid transformation, and fermentation of non-digestiblemucus and substrates. It also has protective functions such asresisting colonization, inflammatory cytokine regulation, and innateand adaptive immunity activation. All these function have a positiveimpact on the human health. Therefore, the constituents of gutmicrobiota interact with each other and with the host’s immunesystem in ways that affect the occurrence of diseases. On the otherhand, it can also cause adverse effects due to dysbiosis, which canresult in autoimmune disease, allergy, irritable bowel syndrome,bacterial infection, and colorectal cancer. However, scientists arestill carrying out extensive research to determine the preciserelationship between gut microbiota and human health and learn how tomanipulate it to benefit the body.


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Guinane,C. M. and Cotter, P. D., 2013. Role of gut microbiota in health andchronic gastrointestinal disease: understanding a hidden metabolicorgan. TherapAdv Gastroenterol,6(4), 295-308.

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Vos,W. M., Engstrand, L., Drago, L. et al., 2012. ‘Human microbiota inhealth and disease.’ Selfcare,3(S1), 1-68.

Wu,D. G. and Lewis J. D., 2013. ‘Analysis of human gut microbiome andassociation with disease. ClinicalGastroenterology Hepatology,11(7), 774-777.