Microbiology
Level: Introductory
Zachary Yuan
It’s eight AM. Alarms sound in households as people get ready for school. On the street below, cars and buses honk in the streets as people rush to get to work or their appointments. Students ride the bus to school. If you imagine what this could look like at a microscopic level, you might have a slight idea of what a microbiome looks like. But what exactly are microbiomes?
What are microbiomes?
Microbiomes are large collections of microbes, including bacteria, viruses, fungi, and microorganisms. These microbes coexist naturally inside our bodies, and together, they can greatly contribute to our health. The human body is home to around 39 trillion microbes, which is more than the number of cells we have!
Some have even referred to microbiomes as a supporting organ in our body due to their importance in maintaining their function and operations. Every human being has a unique group of microbiota that depends on their DNA. The human microbiome potentially holds 500 times more genes than our cells!
The microbiome consists of a lot of microbes that are beneficial to our health– most microbes being symbiotic, meaning the benefits are shared between the body and the microbes– but some can be harmful. Occasionally, the microbes are pathogenic and are able to lead to disease. Usually, pathogenic and symbiotic microbiota can coexist, and disease doesn’t occur. However, if the body they exist in isn’t healthy, or there is an external factor that affects the balance, including diseases, antibiotics, medication, or unhealthy habits, the balance can be thrown off, and the body may be more susceptible to disease.
Where do these microbes come from?
Most of your microbes come from your mother when you exit the birth canal during birth, and research has shown that these bacteria are vital to a healthy first few years in life. Babies who are born through a cesarean section are more likely to develop allergies, asthma, obesity, and other health issues later in life. Scientists suspect that many common allergies, like hay fever, happen due to the lack of exposure to microorganisms when young.
In addition to your mother’s microbes, every single bite of food we consume is home to millions of microbes, and so our diet can have a massive impact on our gut microbiome. If we constantly change diets, the bacteria in our gut microbiomes change as well. Similarly, environmental changes can also affect our microbiomes, as different people and places are home to different microbes. Furthermore, people who live in houses with pets are exposed to a lot more microbes, which isn’t a bad thing.
Where can you find these microbiomes?
Microbiomes can be found in almost every body site, as microbes are capable of living in many different environments. Our body is somewhat like a planet with different climates and biomes– each part of our body like different habitats– and each inhabitant adapts to their location. For example, there are microbiomes in our hands, under our armpits, on our scalp, and many more. One of the most interesting microbiomes is the gut microbiome, which can be found in the small and large intestines. The microbes here live in a dark environment of low oxygen and high acidity.
What do our microbiomes do?
So much! The gut microbiome is incredibly important to our body, and one of the main reasons why is its ability to break down food and aid digestion. The gut microbiome controls the storage of fat and assists in activating genes that break down toxins and absorb nutrients. Moreover, the gut microbiome can create new blood vessels and replenish the linings of the gut and skin when cells get damaged or die during digestion.
Furthermore, the microbiome plays a crucial role in preventing illnesses. When humans are born, their immune systems are only partially formed. It’s through interacting with microbes that our body learns to tell the difference between a harmless symbiont and a pathogen, and exposing our body to new foods is an easy way to introduce new microbes to our body through the gut microbiome!
Our microbiomes even affect how we smell, with different microbe species conveying different scents. This highly personal scent can then act as a unique identification for people. Studies have found that people can be identified just from their sweaty T-shirts!
Scientists also think that our microbiome could affect our mood and behavior, including through sleep and jet lag. When one experiences jet lag, it’s because the change in sleep time puts our gut bacteria out of sync, and our microbiome may be active at the wrong times. In fact, the microbiome even helps us after death. As the immune system stops working, our microbes can spread freely, and our gut bacteria start digesting all our organs inside out, feeding on the chemicals of the damaged cells.
How do our microbiomes affect us?
Our microbiome affects our health in many ways that we are still not certain about. Scientists have found that our microbiomes could influence the brain and specifically our mental health in several ways, as microbes can stimulate nerves, regulate neuro-immune signaling, mediate metabolism, control our neuroendocrine system, and produce neuroactive compounds. In addition, the gut microbiota could produce and regulate neurotransmitters, such as serotonin, dopamine, and glutamate, which play important roles in neurological and immunological activities in the brain.
Furthermore, differences in the landscape of different peoples’ microbiomes may determine their vulnerability to certain diseases and health effects. For example, different environmental exposures can disrupt a person’s microbiome, which might increase the chance of diabetes, neurological and cardiovascular diseases, obesity, allergies, and inflammatory bowel disease. Our microbiota also aid in breaking down toxic food compounds and synthesizing vitamins and amino acids that we digest. For instance, key enzymes needed to form vitamin B12 are found only in our bacteria. Some carbohydrates like starches and fibers are not easy to digest, so the microbiota help to break down these compounds with their digestive enzymes.
The microbiota also protects us from pathogens that enter the body through drinking or eating contaminated water or food. Some microbes that live in our colon prevent the overgrowth of harmful bacteria by competing for nutrients and attachment sites to the mucous membranes of the gut, a major site of immune activity and the production of antimicrobial proteins.
