On this episode of Science to Save the World, Lifespan.io’s general science show, we discuss how our bodies interact with microbes and how much of our biology relies on the microbiome.
Since their discovery in the late 1600’s, we have fostered a relationship of fear and contention with the microscopic organisms living around and within us. Today, this relationship has culminated in the fervent use of antibiotics and a wave of “germaphobia” driven by the COVID-19 pandemic. Can understanding the interconnected, symbiotic relationship we share with microbes lead to better understanding of ourselves?
When most people consider microorganisms such as bacteria, fungi, and viruses, they immediately associate their presence with infectious disease. But that’s not always so. Though invisible to the naked eye, microbes live all around us, as well as within us. And counterintuitively, they are a critical component of what makes us… well… human.
In fact, in terms of total content of cells and DNA, we are more microbial than human. Emerging research suggests that we can be thought of as a tube of human cells housing a complex and dynamic ecosystem of microbes that are wired into every aspect of our biology. Collectively, this ecosystem is known as our microbiome.
The Human Microbiome Project and the Metagenomics of the Human Intestinal Tract initiatives were the first large-scale microbiome projects to define the composition and function of the healthy human microbiome. These studies found that there are literally hundreds of trillions of microbes living on our skin and within our gastrointestinal (GI) tract. These microbes survive by feeding on a wide array of substances, from the sweat on our skin to carbohydrates that we can not ourselves digest.
To place this into a human biology perspective, consider that our microbiome consists of thousands of different species and each of these species consists of a genome containing thousands of genes. This means that in addition to our biology being affected by our own genes, it is affected by billions of microbial genes.
Recent research highlights the complexity of our microbial ecosystem. Not only does our body contain thousands of different species of microbes, but the same species of microbe can perform varying beneficial or pathogenic roles in the body depending on its unique genome. To further add to this complexity, the exact same microbe may be beneficial in one physiological context and detrimental in another. For example, particular bacterial compositions have been shown to be beneficial in full term babies but detrimental to health in premature babies.
How are we to make sense of what is a “healthy” or “unhealthy” microbiome? Efforts to understand healthy microbiomes have revealed that their composition varies widely between healthy individuals. There is no such thing as a single healthy microbiome. Instead, research shows that biodiversity, or the number of different types of bacteria and their metabolic signatures, is more important than the specific types of bacteria that inhabit our microbiome. In other words, a healthy microbiome consists of a core of functional reactions and roles, rather than a core of specific microbial species.
So, how do we acquire our personalized microbiomes in the first place? Do they change over time?