Role of the Human Microbiome in Precision Medicine
What does it mean to be human? At the fundamental biological level, we all share a core set of DNA contained inside our cells, and the material held in these cells defines us as “humans.” In fact, we have over 30 trillion cells in our bodies. However, it’s not just cells that reside inside of us–our bodies are also home to a vast array of microorganisms. These bacteria outnumber our cells more than 10 to 1–so on a biological basis, we’re really more bacteria than human. Gross.
These microorganisms that live inside of us, known collectively as our “microbiome,” are an integral part of our health and wellbeing, thought to influence everything from gastrointestinal diseases to our immune system. Our microbiome is also constantly changing. We receive our first set of organisms from our mother as we’re born, transferred through direct skin-to-skin contact. As we interact with the world, we pick up different species of bacteria along the way, diversifying our microbiome as we interact with different environments. While our microbiome changes a lot during childhood, these changes become less and less frequent as we age, though we can still change our microbiome as adults. And because each person’s microbiome is unique, these diverse clusters of organisms can act like living fingerprints, not only identifying an individual but also providing information about their health and wellbeing.
Variation in the microbiome is common among all people and oftentimes benign. However, certain variations in the microbiome are associated with diseases, like Crohn’s disease, colorectal cancer, eczema, and acne, among others. One potential method of treatment, or at least mitigation, involves genetically modifying the microbiome. This movement exists in the context of a new era of precision medicine centered around the individual. For example, genetic engineering technologies attempt to modify the human genome, an integral and unique part of each person’s identity. While there are many methods of altering the microbiome, like dietary changes and fecal transplants, neither has the precision of gene editing, the accuracy of which has already been tested in the editing of various organisms using CRISPR-Cas9 technology. We know it’s possible to edit the human genome–but what if we were to edit the bacterial genome inside of humans? Could we restore a healthy microbiome to individuals whose organismal ecosystem is unbalanced and potentially treat dozens of diseases?
Yes–possibly. But there are also potential consequences to editing our microbiome. First, our microbiome isn’t well understood. While there is ongoing research regarding the effects of altering the microbiome and its potential implications, we currently lack a comprehensive understanding about the human microbiome. Given the pervasiveness of the microbiome in our body and its systems, I would argue that it is unsafe to edit the organisms living inside of us.But what about the future? What if we reach a point where editing the microbiome is not only safe but can also act as a potential treatment for a multitude of ailments? Not so fast. We still don’t know the long-term effects of microbiome-alteration, or whether the change is permanent. Additionally, as more microbiome research is conducted, enough data will eventually be gathered that it could be possible to identify a person and their specific environmental history based on a simple swab of their skin microbiome. What does this mean for our privacy as individuals? What does this mean for convicts or others who might suffer from stigmatization and discrimination? What would you do if, with a simple touch of your hand and some lab experiments, someone could figure out every place you’ve visited in the past week?
There are also questions about access. Like genome editing technology, it’s likely that microbiome-editing, if ever approved for medical use, would have a large, competitive market. Access to these elusive tools would be limited to only a few with the financial resources to afford such treatment, broadly excluding most people and worsening pre-existing socioeconomic disparities.
Unlike genome editing technology; however, microbiome-editing has potential group-wide effects. While genome editing at the somatic level only affects the individual who has undergone the treatment, microbiome editing has the potential to rapidly affect hundreds of thousands of people. Edited bacteria could be passed from not only from parent to child, but from person to person via a simple touch or even a doorknob. This ability to pass on genetic changes to others raises strong issues of consent–after all, while one person may have agreed to having genetically-modified bacteria living inside of your body, the others who they come into contact with have not and cannot consent to that invisible and inevitable transmission.
Microbiome editing holds great promise for the future to treat a multitude of chronic diseases. But we should also be cautious as we move forward about the potential harm it could cause to us not only as individuals, but as a society.
Edited By: Elissa Gorman
Graphic Designed By: Eugene Cho
 Bianconi, E., Piovesan, A., Facchin, F., Beraudi, A., Casadei, R., Frabetti, F., Vitale, L., Pelleri, M. C., Tassani, S., Piva, F., Perez-Amodio, S., Strippoli, P., & Canaider, S. (2013). An estimation of the number of cells in the human body. Annals of human biology, 40(6), 463–471. https://doi.org/10.3109/03014460.2013.807878
 U.S. Department of Health and Human Services (2015). NIH Human Microbiome Project Defines Normal Bacterial Makeup of the Body. National Institutes of Health. https://www.nih.gov/news-events/news-releases/nih-human-microbiome-project-defines-normal-bacterial-makeup-body#:~:text=The%20human%20body%20contains%20trillions,vital%20role%20in%20human%20health.