Prompt 2.1

 What I prediction I chose to base my example around was species changing through time (microevolution). The example I chose was the evolution of MRSA. I think this example is interesting as it bears a similarity as to why researchers are anticipating COVID-19 to evolve. MRSA can be a good example of microevolution as one dominant strain, healthcare associated MRSA (HA-MRSA) type ST239, has been evolving locally at hospitals and reaching global proportions as it gains antibiotic resistance. Now, why specifically is it this strain that is important? The reason why this strain is integral is in part due to its environment. Hospitals often are able to have access to higher-end treatments, such as antibiotics. The frequent usage of antibiotics, especially in cases of over-prescription or unfinished treatment, gives bacteria an opportunity to adapt. As a result, HA-MRSA is able to evolve at a rapid pace due to an increased exposure to antibiotics than it would encounter in most environments.

The reason why MRSA serves as such a compelling piece of evidence for evolution starts with its discovery in the 1940s. Unsurprisingly, the current strain of resistant MRSA was not the same as the initial strain discovered in the 1940s. In fact, the initial MRSA strain had evolved as it gained increasing exposure to the antibiotic treatments that were used to combat it. By the 1950s, MRSA was found to be resistant to penicillin and methicillin, which are the antibiotics that were initially used to treat the disease. In today's MRSA strains, not only they are related to the aforementioned strains of antibiotics and others, but also one of the most potent antibiotics today, vancomycin. Vancomycin is often merely a last resort, which shows the scope that this bacteria has been able to evolve to gain resistance. This is quite a terrifying amount of evolution that has been observed in such a short amount of time. As each bacterial generation reproduces, new mutations introduced that favor resistance can quickly spawn as the generation time of bacteria is shorter than that of many other larger species. The resulting consequence is a bacteria that is capable of greater antibiotic resistance than its predecessors as advantageous mutations allow for more survivability and proliferation.

This phylogenetic tree shows evidence for the spread and transmission of ST239 as it occurred intercontinentally. The scale bar shows substitutions that occurred in three SNP sites. 

Citations:

Enright, M. C., Robinson, D. A., Randle, G., Feil, E. J., Grundmann, H., & Spratt, B. G. (2002). The evolutionary history of methicillin-resistant Staphylococcus aureus (MRSA). Proceedings of the National Academy of Sciences, 99(11), 7687-7692.

Harris, S. R., Feil, E. J., Holden, M. T., Quail, M. A., Nickerson, E. K., Chantratita, N., ... & Bentley, S. D. (2010). Evolution of MRSA during hospital transmission and intercontinental spread. Science, 327(5964), 469-474.

Hiramatsu, K., Cui, L., Kuroda, M., & Ito, T. (2001). The emergence and evolution of methicillin-resistant Staphylococcus aureus. Trends in microbiology, 9(10), 486-493.