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My Favorite Bacteria: Intestinal Microbiome Essay

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Updated: Apr 14th, 2022


The intestinal microbiome plays a significant role in the health of human beings, and people cannot survive without these microorganisms. The intestinal microbiome refers to the entire genetic composition of all the microorganisms found in the intestines. Human beings acquire these microorganisms at birth, and studies indicate that the composition of microbes in children born through Caesarean section varies from those who are born through normal birth. Scientists point out the importance of colostrum to the health of newborn babies. For instance, colostrum consists of a wide variety of essential microbes that enhance the immune system of children and reduce their susceptibility to diseases. Children acquire more microbes as they grow old. The body of a grown person is a microcosm of a microbial universe consisting of trillions of bacterial cells in different parts of the body. The total number of microbial cells in the human body exceeds the number of human cells due to the fact that microbes are significantly smaller. The diversity of microbial species in a healthy person’s gut exceeds 1,000. Studies indicate that microorganisms occupy 60% of a healthy person’s colon. Most of the intestinal bacterial belong to Bacteroidetes and Firmicutes species. The compositions of the intestinal microbiome vary for each person due to different factors, such as diet, age, or area of residence (Human Microbiome Project Consortium, 207). However, some microbial species are common in many individuals. Intestinal microorganisms form a crucial symbiotic relationship with human beings.

Functions of Gut Microbiome

Fermentation and absorption of carbohydrates

The intestinal microbiome helps in breaking down some undigested carbohydrates. Human beings lack enzymes required to digest some types of polysaccharides, such as starch, oligosaccharides, lactose, and fiber. Incomplete digestion of such carbohydrates as oligosaccharides or lactose causes flatulence. Bacteria play a critical role in the fermentation of carbohydrates to produce butyric, propionic, and acetic acids. Such acids are important to the health of human beings because they assist in the absorption of vital dietary minerals and provide nutrients and energy. Butyric acid acts as a source of energy to intestinal cells, while the liver depends on propionic acid in the production of ATP. Intestinal bacteria assist their hosts to absorb and store lipids. The intestinal microbiome helps in the production and absorption of important vitamins, such as vitamin K. Intestinal microbiome improves water absorption in the gut, stimulates the growth of intestinal cells, and lowers the abundance of harmful bacteria in the intestines. However, studies also indicate that some intestinal microbes may cause proteolytic fermentation that could produce toxins. Proteolytic fermentation refers to the process that results in the breakdown of proteins into amino acids.

Trophic Effects

Fermentation of carbohydrates into fatty acids stimulates the increase of the epithelial cells in the intestines. The fatty acids also help in regulating the differentiation and proliferation of the epithelial cells. The presence of fatty acids in the intestines increases the growth of lymphoid tissue in the gut. The intestinal microbiome prevents the occurrence of gut mucosal damages.

Destruction of Pathogenic Microbes

One of the most significant functions of the intestinal microbiome is the prevention of the growth of pathogenic microbial species in the gut. The beneficial intestinal microorganisms exclude the harmful microbes through the barrier effect where the beneficial microbes deny the harmful bacteria access to nutrients and space on the intestinal mucosal lining. People with little or no beneficial intestinal microbiome are susceptible to attacks by harmful species of bacteria and yeast. The barrier effect prevents invading harmful species from attacking the intestinal mucosal lining while maintaining the abundance of existing harmful species at low levels. The conditions in the intestines favor the establishment of beneficial intestinal microbial colonies, and this enables the beneficial gut microbes to outcompete the harmful microbes for vital resources. The beneficial intestinal microorganisms also produce toxic bacteriocins at levels that destroy the harmful bacteria without affecting the host cells. Fermentation produces acids that increase colon acidity and prevents the increase of harmful microbial species in the colon. The acidity also helps in the removal of toxic and carcinogenic materials from the human body.


Intestinal microbes play a significant role in stimulating mucosal immune system development and maintaining the functioning of this immune system. The first microbes that settle in the intestinal linings of newborn babies initiate immune responses that help the newborn babies respond to attacks by harmful microbes in the future (Dimmitt et al., 2). The beneficial intestinal microorganisms trigger immune responses involving dendritic cells, M cells, and surface enterocytes whenever the abundance of pathogenic microbes increases in the gut. The intestinal microbes facilitate the tolerance to various antigens ingested by the host. Such tolerance is crucial because it helps in reducing autoimmune reactions to allergies. Intestinal microbiome also assists in the repair of damaged intestinal cells. People with few beneficial intestinal microbes are susceptible to Clostridium difficile infections that result in excessive diarrhea and intestinal pain that may kill the patients. Currently, the “poop pills” treatment offers the best option for treating Clostridium difficile infections (Van Nood et al., 407). “Poop pills” contain beneficial intestinal microbes that reduce bouts of diarrhea in patients suffering from Clostridium difficile infections.

Metabolic Function

The beneficial intestinal microbes help in facilitating the synthesis of some vitamins including folate and biotin, and the absorption of iron, calcium, and magnesium ions (Canny and McCormick, 3360). The intestinal microorganisms are crucial in the metabolism of dietary carcinogens that result from consuming foods cooked at high temperatures.

Impacts of Taking Antibiotics

Taking antibiotics lowers the abundance and diversity of intestinal microbes, and this may have negative impacts on the host. For instance, an individual using antibiotic medication may have trouble digesting certain types of food. The reduction in intestinal microbial diversity increases the risk of suffering from metabolic disorders. People consuming antibiotics cannot ferment carbohydrates properly and may experience flatulence. Such individuals may also suffer from antibiotic-associated diarrhea. Ingesting antibiotics may also increase the abundance of intestinal microorganisms that are resistant to antibiotics, and this is dangerous because it increases the severity of microbial diseases. The reduction in the abundance of beneficial intestinal microbes allows pathogenic microbial species, such as Salmonella spp, to increase in the gut and cause diarrheal diseases.

Inflammatory Bowel Disease (IBD)

Extensive changes in the composition of intestinal microbes result in the occurrence of the inflammatory bowel disease. The microbial composition changes occur due to factors, such as antibiotic use, intestinal or stomach infections, and use of probiotics. The major subtypes of inflammatory bowel disease include Crohn’s disease and ulcerative colitis. As Morgan et al. (1) point out, Crohn’s disease affects the digestive tract randomly, while ulcerative colitis only affects the colon.

Intestinal Microbes and Cancer Treatment

In addition to influencing the susceptibility to various diseases, the balance that exists in the intestinal microbiome is important to an individual’s health because it affects the response to various medications. Researchers point out the significance of intestinal microbes to the effectiveness of cancer treatment. Scientific studies indicate that the absence or inadequacy of intestinal microorganisms makes cancer treatment less effective. Intestinal microbes influence the susceptibility to cancer by modifying an individual’s immune system. Studies also link several harmful intestinal microbes to different cancers. For instance, the hepatitis C virus causes hepatocellular carcinoma while Salmonella enterica infections increase the risks of developing gallbladder cancer. Scientific research studies suggest that Heliobacter pylori bacteria boost the risk of contracting gastric cancer (Holmes, 352). However, the presence of microbial species, such as Bifidobacteria spp. and Lactobacillus spp, reduces the probability of developing intestinal tumors.


Intestinal microbiome plays a crucial role in the well-being of human beings because they participate in numerous metabolic activities in the gut. The high abundance and diversity of intestinal microbes help in preventing several diseases, such as IBD and various forms of cancer. Studies indicate that intestinal microbes help in increasing the immunity of individuals and destroying pathogenic microorganisms that cause illnesses. Newborn children who do not receive colostrum from their mothers are likely to suffer from numerous diseases throughout their lives. Consequently, mothers must ensure that they breastfeed their children to protect them from diarrheal diseases. Ingestion of antibiotics changes the abundance and diversity of intestinal microorganisms, and this may have negative impacts on the health of an individual. Patients relying on antibiotics should follow their doctors’ instructions to avoid interfering with the composition of their intestinal microorganisms.

Works Cited

Canny, Geraldine, and Beth A. McCormick. “Bacteria in the intestine, helpful residents or enemies from within?” Infection and immunity, 76.8 (2008): 3360 – 3373.

Dimmitt, Reed, Elizabeth Staley, Scott Tanner, Thomas Soltau, and Robin Lorenz. “The Role of Postnatal Acquisition of the Intestinal Microbiome in the Early Development of Immune Function.” Journal of pediatric gastroenterology and nutrition 51.3 (2010): 262 – 273.

Holmes, Elaine, Jia Li, Thanos Athanasiou, Hutan Ashrafian, and Jeremy Nicholson. “Understanding the role of gut microbiome–host metabolic signal disruption in health and disease.” Trends in microbiology, 19.7 (2011): 349 – 359.

Human Microbiome Project Consortium. “Structure, function and diversity of the healthy human microbiome.” Nature, 486.7402 (2012): 207 – 214.

Morgan, Xochitl, Timothy Tickle, Harry Sokol, Dirk Gevers, Kathryn Devaney, Doyle Ward, Joshua Reyes, Samir Shah, Neal LeLeiko, Scott Snapper, Athos Bousvaros, Joshua Korzenik, Bruce Sands, Ramnik Xavier, and Curtis Huttenhower. “Dysfunction of the intestinal microbiome in inflammatory bowel disease and treatment.” Genome Biology, 13.9 (2012): 1 – 18.

Van Nood, Els, Anne Vrieze, Max Nieuwdorp, Susana Fuentes, Erwin Zoentendal, Caroline Visser, Ed Kujiper, Joep Bartelsman, Jan Tijssen, Peter Speelman, Marcel Dijkgraaf, and Josbert Keller. “Duodenal infusion of donor faeces for recurrent Clostridium difficile.” New England Journal of Medicine, 368.5 (2013): 407 – 415.

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