Evolutionary Medicine

Content Objective:

The unit will have students’ focus on the following:

Case study:

In 2013, Addie Rerecich was an active 11-year-old girl in Tucson, Arizona.⁷ One night, she mentioned to her mom, Tanya Rerecich, that she was feeling pain in her hip. Her mom figured that she must have injured herself a bit while doing one of her activities. Tanya only gave Addie ibuprofen, in hopes that this would help her with her pain. Later that night, the pain got worse and they had to take her to the emergency room. That is when they found out she had a methicillin-resistant Staphylococcus aureus (MRSA) bacterial infection in her body. At this point, the bacteria had already spread to Addie’s bloodstream. The doctors would give her a series of antibiotics to fight the bacteria. The treatment would leave Addie in a state of recovery-relapse scenario, where she would be fine for a series of days, but then fall back ill until the doctors gave her a different set of antibiotics. Afterwards, the doctors had exhausted all their options and had the idea of administering an Extracorporeal Membrane Oxygenation (ECMO) procedure. ECMO is an invasive procedure where a machine oxygenates blood for the patient, then returns it back to their body. There are many risks to this “last-resort” procedure, as medical equipment may not be clean enough for such an invasive treatment. Unfortunately, this was the case for Addie who contracted a new antibiotic resistant bug, Stenotrophomonas maltophilia. S. maltophilia is commonly found in healthcare facilities and is a serious threat to human health because of antibiotic resistance as well. Tanya had to beg and fight for a lung transplant for her daughter, as it was possibly the remaining option for her daughter to live. Which ended up working! However, not without consequences. Addie has to take a treatment mixture of different medications to ensure her health after her fight with the superbug, and has gone through a lung transplant at a very young age.

Evolution Terminology:

Evolution terminology will be taught first to the students, to make sure they have a handle on the relevant definitions. The terms include natural selection, genetic variation, mutations, phylogenetics, etc. Beyond making sure that students have an understanding of known terminology expected during this unit, additionally these terms will be used when focused on the medical information of antibiotic resistant bacteria.

1. Natural Selection-Differential survival or reproduction of different genotypes in a population leading to changes in the gene frequencies of a population. The conditions required for the operation of evolution by natural selection include variation, a system of heredity, differential reproduction, and time.¹⁷ Students need to know that bacteria that are antibiotic resistant can be favored for fitness relative to other variants, and thus can replicate and proliferate in antibiotic environments.
2. Artificial Selection-the method where particular traits are changed in populations by humans choosing which individuals are allowed to breed, thus designing traits according to human preferences. This is seen in domestication. Students need to know the difference between Natural Selection and Artificial Selection, with examples of how to identify a species that evolved via one or the other process.
3. Adaptation-A trait that evolved because it fosters better survival or reproduction in the environment. This term is to help students understand how a population of organisms can react to changes in an environment, if it is selected to better survive and reproduce.
4. Genetic Variation-the presence of differences in sequences of genes between individual organisms of a species. It enables natural selection, one of the primary forces driving the evolution of life.¹² Students need to understand how genetic variation is “created” in an organism with examples of what that looks like
5. Mutations: Random events in DNA/RNA that can occur during mitosis/meiosis/Cell division. There are different types of mutations, such as:
1. Silent Mutation: A mutation where a nucleotide substitution that codes for the same amino acid; therefore, there is no change in the amino acid sequence or protein function.¹¹
2. Nonsense Mutation: A mutation where protein production has stopped prematurely. Could have serious consequences, where the protein is not functioning properly.
3. Frameshift Mutation: A mutation where an extra nucleotide (either insertion or deletion) shifts the original mRNA, could lead to a Nonsense mutation or an overproduction of amino acids for a protein that will not work properly. VERY SEVERE
6. Phylogenetics or Phylogeny: A method of analyzing how organisms can be related, on a genomic level. A phylogenetic tree is used often when explaining how species share common ancestry shown by a branching pattern. This term is for students to understand about bacteria (or multicellular organisms) being able to evolve from an earlier ancestor or form and what it currently is today.
7. DNA/RNA (Deoxyribose Nucleic Acids/Ribose Nucleic Acids): Genetic Code for all living organisms. Students should know that evolution is focused on an organism’s genetic code. DISCLAIMER: You can mention what DNA/RNA is, however be careful not to go full in detail. We will discuss DNA/RNA during the genetics unit.

Students need to know this term and the subcategories to know when a mutation occurs.  Mutations in any species is a sign of potential evolutionary change, if it is favorable to survive⁷.

Microorganism Biodiversity:

For this content, it is important for students to understand that although we do get sick from bacteria, most bacteria are not relevant for human health. I would not worry so much about the different types of bacteria that exist, but to focus on the observation that bacteria exist everywhere and that some are “bad”, whereas most are “good” bacteria in terms of Earth’s ecosystems and for interactions with other organisms, such as our beneficial microbiome. The Bacteria Lab will help with this understanding for the students that bacteria are everywhere (more under the activity section). That being said, the following information should be taught to your students when focused on bacteria:

• Gram Positive vs. Gram Negative Bacteria-Gram-Positive versus Gram-Negative bacteria details a key difference in the cell wall structure of the two major bacteria groups. The outer membrane of the cell wall of the bacteria is present in one (Gram Negative) versus the other (Gram Positive). This plays a part in human health because one group of bacteria can trigger the immune response and can evolve resistance to antibiotics (Gram Negative). And although Gram Positive bacteria can still trigger diseases, they can be more often treated successfully using antibiotics because of the lack of the protective outer membrane. Students need to understand that the outer membrane layer of the cell wall structure is the reason why antibiotic resistant bacteria (Gram Negative) are more favored for fitness in disease, thus the issue of dealing with them can be difficult¹⁰.
• Bacteria vs. Viruses-Bacteria are living, single-celled organisms that can survive and reproduce on their own. They have similarities to other cellular species, such as the ability to maintain homeostasis, use nutrients to survive, and reproduce. Bacteria can often be treated with antibiotics. In contrast, viruses are not made of cells; they are composed of genetic material (RNA or DNA) surrounded by a protein coat called a capsid. Unlike bacteria, viruses cannot function or reproduce without infecting a host cell. This fundamental difference makes viruses more challenging to treat, as they require a host to multiply, and most treatments focus on supporting the immune system rather than directly targeting the virus.^1,4

DO NOT talk about the total structure or morphology of the bacteria, as that is all for the cell unit. Focus more on the evolution of bacteria and less about the functionality of bacteria.

Medical Information:

Students will be getting a lot of medical terminology and information that would need to be broken down/scaffolded for them to understand better:

1. Antibiotics-medication prescribed to treat bacterial infection. Explain to students what they are, the history of antibiotics, the advancement of modern life and human existence, and their current problem about overusing or underuse of antibiotics.
2. Superbug-A bacteria that is Multi-drug resistant. Elaborate on what a “superbug” is, why it got its name, and how come they are our current issue.
3. MRSA (Methicillin-resistant Staphylococcus aureus)-A “superbug” strain of S. aureus that is resistant to methicillin and typically other antibiotics as well. This is necessary when focused on the case study.
4. ECMO (Extracorporeal Membrane Oxygenation)-A medical procedure where a machine filters and oxygenates a patient's blood. This is necessary when focused on the case study
5. The rate of bacterial growth-The speed of proliferation for any bacteria. The students need to understand how quickly bacteria can grow in a matter of hours. A graph detailing the rate of growth would be ideal. I would get examples of different types of cells and bacteria species that have different rates of growth.

Evolutionary Medicine:

The content and focus of the unit is on Evolutionary Medicine. Evolutionary Medicine is defined as the use of modern evolutionary approaches to better understand human health and improve disease treatment. A central question in evolutionary medicine is this: Why has natural selection left our bodies vulnerable to disease?¹⁶ For this, you must use the concepts of traditional evolution content normally taught at a high school level, and combine with the information of how bacteria are organisms who are currently evolving to build a resistance towards  .

Last Resort:

I plan on having my students do a research project involving different types of superbugs. The final thing I want them to consider, is a patient’s last resort option. You may need to have a list of options for them to consider. Last Resort options could be the following:

1. Organ Transplant-Organ transplants can have a series of risks including the body rejecting the organ or the organ giving the patient cancer, if the donated organ was from someone who either has a history of cancer or a family history of cancer⁷
2. Invasive Procedure-Procedures that may have high risk include general surgery in a highly infected area or a method, like ECMO, where risk of sepsis exists (Sepsis is a life-threatening condition that arises when the body's response to an infection causes widespread inflammation.) Essentially, it's the body's extreme reaction to an infection. or other “superbug” infections can occur. Added risk may include if the patient is immunocompromised or if the patient is an older patient.
3. Experimental Medication-The high risks of experimental medication can result in a medication not working or a medication with extremely volatile results such as other organs or cells being targeted versus the actual pathogen causing the problem. Chemotherapy is a prime example of this, but other drugs can also have this effect.
4. Amputation-This option is considered when the infection is located on and spreading to the extremities of the human body. However, amputation may not always resolve the issue, so regular reexaminations are crucial for ongoing care. It’s important to note that the patient will lose a limb permanently.⁸
5. Death-This is if there are no other options and up to the patient to decide. It is the job of the medical professionals to make sure the patient is comfortable during “end of care” treatment. 

Research and Note taking:

A unit assessment that I will perform with my students is to do a research project about a “superbug”, the antibiotic that is failing to treat the bacteria infection, the moment the bacteria become resistant to the antibiotic, and possible last resort ideas. I mainly have incoming 9th graders in a high school class, who likely have not done a research project before. So, it is best to talk about doing proper research.

I would collaborate with the school librarian when talking with students about their research. I would invite the librarian as a guest speaker and come up with an exercise with the students to practice how to do proper research. For example, they could do an activity where they research a personal interest to them that is culturally relevant ^2,3.

Note taking should also be taught when doing research. Teach the students on different methods of note taking and practice.¹⁹ It is important to talk about linear note taking (i.e. outlines or transcribing) versus non-linear (i.e. mind maps or Cornell notes) and have your students self-assess what works best for them³ .  Talk to the librarian, or an English or History teacher about how they prepare their students to do research for their classes, if you need more assistance.

Graphing:

Rate of growth is important to understand the speed of how all cells can proliferate. According to Next Generation Science Standards (NGSS) HS-LS3-3, HS-LS4-1, HS-LS4–2, and HS-LS4-3, these standards focus on a student’s ability to use statistical data, analyze the data, and communicate the explanation of growth of an organism. This requires students to understand and interpret scientific models, such as graphs and images. For students to understand this, they must understand how to read a graph. Teach students the difference between an independent and dependent variable, how to properly label a graph, the different types of graphs that they overall may see in the class or in society (such as bar, line, and pie charts), and practice how to make a graph using an example dataset (more during the activities section). Later, give them an exercise on how to communicate on the graphs. All of this will prepare them to understand the rate of growth of different types of bacteria species.

Claim, Evidence, Reasoning (CER)-CER is an argumentative style of writing. In science classes, CERs help students practice their writing to support their scientific claims using evidence that they have found, and why they are using this particular evidence. I do this almost every opportunity in my lessons, but for this unit, it helps you execute NGSS standard HS-LS3-2, HS-LS4-2, HS-LS4-4, And HS-LS4-5.