In third grade, the word ‘fart’ was completely off-limits. A mere utterance of the forbidden term would incite thunderous laughter, incapacitating the class with a serious case of the giggles. Because of the entire hubbub around this natural body process, I distinctly remember one revolutionary third grade lesson. When our teacher informed us that the majority of flatulence is produced by intestinal bacteria, I was astounded. The idea that puny creatures call our bodies home and have such a large (and, admittedly, smelly) impact on us, shocked me. I was also terribly confused: why do bacteria — which typically cause diseases like typhoid and cholera — live inside humans?
Looking back, this was my first encounter with the human microbiome. In broad terms, our microbiome consists of the ecological community of microbes (bacteria, archaea, fungi, protists and viruses) that live in and on our bodies. Though we have one trillion human cells, the 100 trillion microbial cells contained inside our own bodies drastically outweigh this number. In joint association, human and microbe cells work together, playing a pivotal role in keeping us healthy. Our microbiome uses the human body as an environment to carry out crucial processes that help us stay alive. These roles are so central to normal body functioning that the American Society for Microbiology characterizes the microbiome as a newly discovered organ.
Though adults harbor over thousands of microbes, we are not born with this preset community of microorganisms. Infants first start to amass a microbiome when they are colonized by their mother’s placental collection. After this initial stage, a baby’s microbial community exponentially increases; exposure to the world, to different caregivers and to varied environments is a significant factor in this step. Breast milk is one of the most important avenues through which an infant establishes a microbiome: though the substance contains some complex carbohydrates that the baby cannot fully digest, certain microbes can digest them. As a result, bacteria coat the infant gut and prevent harmful pathogens from attaching to the intestines. Beyond the infant stage, our microbiome species diversity continually shifts in response to dietary changes, age, environment, lifestyle and microbial community ecology interplay.
The microbiome performs countless functions for our bodies; to name just a few, it helps synthesize necessary vitamins, train our immune systems and ward off pathogens. Given these vital microbial functions, it is important to study this branch of science because there are countless microbiome-based medical applications that we can use to treat disease and promote human health. The key to the microbiome is its changeable nature; since our microbe collection changes from time to time, we can develop treatments that alter a patient’s microbiome to contain more favorable species and thus function at an optimal level. This has the potential to restore health and eradicate disease.
Sometimes, however, patients need to prevent their natural microbiome from radically changing and therefore preserve their microbe collections. Doctors have found that cancer patients recover much faster if their microbiomes are protected; as a result, many physicians have started to save patient gut microbiomes in the form of stool samples and then re-inoculate patients with their own microbiota after harsh treatments like chemotherapy. This helps patients re-establish their microbe equilibrium faster than before.
Since my initial introduction to the microbiome, my passion for this funky and promising field has only grown. I hope my passion for the microbiome broadens your appreciation for this stunningly rich community. And, moving forwards, we will begin to understand why it is important to take good care of our 1000+ microbe friends and how we should go about doing so.
Nikita Deshpande is a rising sophomore in the College. Microbial Explorations is published every other Wednesday.
