Human Microbiome

Zachary Snelson

The Host Microbiome Regulates and Maintains Human Health: A Primer and Perspective for Non-Microbiologists


General audience:

Human beings have always seen themselves as superior organisms that can operate on their own. However, would you ever think that even small parts of your body can have an entire ecosystem of microbes? Those interacting microbes can effect not just each other, but they can also have effects on the human host too. This research paper gives details on how the amount of diversity of microbes in the human microbiome can lead to adaptations against certain diseases and the changes in microbiome overtime can also help maintain the host’s development. Changes in the human host in terms of aging, diet and even what kind of environment that they are in have important roles in how the human microbiome is composed. The ongoing research over the diversity and composition of microbes on the human host can help us to further understand the molecular mechanics in disease.

The diverse variety of microbes in the human microbiome consists of not only bacteria and viruses, but also archaea and fungi as well. What kinds of benefits the microbes in the human microbiome can offer in terms of survival can range from The microbiome changes as the host ages, such as when a newborn is introduced to a foreign environment and when it eventually grows up to be an adult. When a baby is born, it can have a different structure in its microbiome depending on how it was born. For example, when born vaginally, the baby will have bacteria that helps aid in the digestion of lactose in milk products due to microbes in the vaginal cavity coming into contact with the baby during birth. Even other types of interaction with the human host can alter the microbial communities in the microbiome. In this case, the human host having a different diet can promote changes in the gut microbiota, an example such as animal products can increase the abundance of bile resistant bacteria in the gut. The human microbiome can play a crucial role in providing other benefits that can help maintain the host’s health. Such examples are the gut microbiome acting as a safeguard against cardiovascular disease, Inflammatory Bowel Syndrome, and pathogens. Cancer is also another threat to the health of the human host and negatively impact the microbiome. Changes in the gut microbiome from foreign bacteria, antibiotics, and age related symptoms can lead to the development of cancer in the human host’s gut.

Microbes in the human host that were genetically engineered have potential that can even assist with cancer prevention. It is important to help assess the advances in the diversity of microbes in the human microbiome to accommodate the emerging methods of surveillance and detection of different strains of microbes on the human body. Looking into how and why the interacting microorganisms in the human microbiome will be able to help us further understand the implication that microbes have on important medical fields such as disease management, cancer research, and even aging.


To emphasize the size and scale of microbes, the amount of eukaryotic cells in the human body is estimated to be 3 × 1013   and there are about 3.9 × 1013 colonizing microorganisms, in which would imply that the amount of microbes is larger than the human host. There is compelling evidence that the interaction between microorganisms in the human biome and the host is important to maintaining the individual host’s survival. The diversity of the microbiome is determined using metagenomic data. The bioinformatic results from the targeted metagenomic sequencing are available from various sources such as the Human Oral Microbiome Database, SILVA, and the Ribosomal Database Project. Prokaryotic microbes such as bacteria, archaea, fungi and even viruses like Bacteriophages play a role in the ecology and community of prokaryotes and eukaryotes in the human gut. Even eukaryotic microbes such as fungi, Protozoa, algae, and nematodes are prevalent in the skin microbiota.

The human microbiome in terms of diversity can change over time as the host develops and ages during its lifetime. When it comes to the development microbiota of babies, for instance, changes depending on the human host being exposed to a different environment over time. When the human baby is born, for instance, the microbiome can change depending on how the host is born and what types of microbes are related to those types of exposure. Babies that were born through the Cesarean section method were found to have Streptococcus spp. and other bacteria that were associated with the mother’s skin, while babies born vaginally have Lactobacillus which can aid in the digestion of milk. Aging over time can lead susceptibility to disease that correlates with changes in the immune system such as increase in inflammatory states in the gut, Lactobacillus bacteria increasing with low fat diets and oxidative stress that encourages virulence of anaerobic bacteria. The human microbiome can play a role in the health of the heart in regards to cardiovascular health, obesity and even behavior. The human microbiome, especially the gut microbiota, are vital for the metabolic potential to alter the chance of the human host having cancer. The microbiome can be changed by dysbiosis, which is the disruption of interactions between the gut flora and the human host. Smoking, foreign pathogens, and immunosenescence from aging are major factors that can disrupt the gut microbiome, and can eventually result in negative results such as tumor progression.

While evidence for the interplay is not fully understood, there have been evidence to show that microbes can affect the rate of carcinogenesis, the progression of tumors and the overall response to immunotherapy treatment. Through the co-evolution between the human host and the microbiome, the immune system is inherently modulated by microorganisms that inhabit the human host from selective pressure from invading pathogens in the environment. The applications of microbes in the gut microbiome can help provide insight on how microbes can help benefit the human host in preventing irritable bowel syndrome and In order to help improve cancer treatments, researchers will need to keep thoroughly examining the human microbiome. While there have been astounding achievements in developing the taxonomy of the human microbiome, there are still challenges in Studying the human microbiome can help us become more familiar with the genetics, biology, physiology and immunologic effects of the interacting microorganisms in the human host.

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