Hi guys welcome back to MicroBioMe insights today is Day 3 of our journey to understanding the gut microbiome. After researching the connection between energetics and microbiomes I thought it would be interesting to research the connection to evolution. So today we’re going to dive deeper into how evolution impacts our gut microorganisms today. The human gut microbiome interaction is a prime illustration of mutualism. What is a mutualistic relationship?: A mutualistic relationship is when two organisms “work together” to benefit each other—we provide a habitat and nutrients for these microorganisms, and in return, they assist us in breaking down food, maintaining our immune system, and supporting overall health. So now let’s see how evolution has shaped and aided in this relationship.
Natural Selection inside the Intestine
What is natural selection, then? It’s a process by which more successfully adapted organisms reproduce and survive in their surroundings. In our gut, natural selection is impacted by factors which are our diet and our immune system, creating an environment where bacteria are constantly adapting.
Diet as a selection Pressure
Our diet is one of the most important factors that shape our gut microbiomes to how they are right now. Different bacteria species do well on different diets. For example, some bacteria thrive in high-fiber diets whereas some are better suited for high-fat diets. This dietary differences leads to every individual having a unique microbiome composition, there will definitely be overlap although the composition will always be unique to each individual. The gut environment, influenced by diet, will determine which bacterial population thrive. For example, if we take a high-fiber diet it promotes bacteria that effectively break down fiber, while a high fat diet favors those that metabolize fast.
Immune System as a selection Pressure
The immune system also acts as a selection pressure in our gut. But how?: this is because bacteria that can avoid the immune response have a higher chance of survival and can establish themselves, while the bacteria that can’t are eliminated. This cycle of interactions ensures that only the bacteria with adaptive traits, such as immune avoidance capabilities, survive in the gut. This selection process works to maintain a healthy balanced microbiome that supports overall health.
Evolution of antibiotic resistance:
Our gut bacteria have evolved ways to resist antibiotics, a process which is driven by natural selection and genetic exchange. The most important method that bacteria use to gain antibiotic resistance is through the transfer of plasmids: which are small circular DNA molecules that can be shared between bacteria.
F Plasmids and Antibiotic Resistance F plasmids usually carry genes that provide antibiotic resistance. Through a process called conjugation, bacteria with F plasmids can transfer and give these resistance genes to other bacteria. When antibiotics are introduced, they act as a selection pressure like i just previously discussed. Bacteria without resistance genes are killed and are obviously not able to reproduce, while those with resistance genes survive and reproduce. These resistant bacteria can then spread their resistance traits to other bacteria, leading to the development of antibiotic-resistant populations, so the populations are evolving with this resistance.
