Biology: Human Microbiome and Health
Exploring how microbial communities affect the body
Biology: Human Microbiome and Health
Exploring how microbial communities affect the body
Biology - Grade 9-12
- 1
Define the human microbiome. Include both the organisms and the genetic material involved in your answer.
Think beyond bacteria alone. Include what the microbes carry inside their cells.
The human microbiome is the collection of microorganisms that live in and on the human body, including bacteria, archaea, fungi, viruses, and other microbes. It also includes the genes and genetic material of those microorganisms. - 2
The gut, skin, mouth, and vagina each have distinct microbial communities. Explain why different body sites tend to have different microbiomes.
Different body sites have different microbiomes because each site has unique conditions, such as moisture, pH, oxygen level, temperature, nutrients, and immune activity. Microbes that survive well in one environment may not survive well in another. - 3
A student says, "All bacteria in the human body are harmful." Explain why this statement is incorrect.
Consider what beneficial microbes do in the digestive system and on body surfaces.
This statement is incorrect because many bacteria in the human body are harmless or helpful. Some bacteria help digest food, produce vitamins, train the immune system, and prevent harmful microbes from growing. - 4
Describe two ways that gut bacteria can contribute to human digestion and nutrition.
Gut bacteria can help break down complex carbohydrates, such as fiber, that human enzymes cannot fully digest. They can also produce useful compounds, such as short-chain fatty acids and certain vitamins, including vitamin K and some B vitamins. - 5
Short-chain fatty acids are produced when certain gut bacteria ferment dietary fiber. Explain one way short-chain fatty acids can support human health.
Focus on the connection between fiber, bacterial fermentation, and the cells of the colon.
Short-chain fatty acids can support human health by providing energy to cells lining the colon, helping maintain the gut barrier, and influencing inflammation and metabolism. They are one reason that fiber-rich diets can support a healthy gut microbiome. - 6
Compare a diverse gut microbiome with a low-diversity gut microbiome. Why is microbial diversity often considered beneficial?
A diverse gut microbiome contains many different types of microbes, while a low-diversity microbiome contains fewer types. Diversity is often beneficial because a wider range of microbes can perform more useful functions and may make it harder for harmful species to dominate. - 7
Explain what dysbiosis means and give one example of a factor that can contribute to it.
The prefix dys- often means abnormal, difficult, or impaired.
Dysbiosis is an imbalance or disruption in the normal microbial community of the body. It can be caused by factors such as antibiotic use, poor diet, infection, illness, stress, or major changes in the environment. - 8
Antibiotics can be life-saving, but they may also affect the microbiome. Explain how antibiotic treatment can increase the risk of an opportunistic infection such as Clostridioides difficile.
Antibiotics can kill harmful bacteria, but they can also kill helpful gut bacteria. When normal gut microbes are reduced, there may be less competition for space and nutrients, allowing an opportunistic pathogen such as Clostridioides difficile to grow and cause disease. - 9
A researcher collects microbiome samples from students before and after a 2-week high-fiber diet. Identify the independent variable and one possible dependent variable in this study.
The independent variable is what is changed or tested. The dependent variable is what is measured.
The independent variable is the high-fiber diet or the change in diet over the 2-week period. A possible dependent variable is the composition, diversity, or abundance of specific microbes in the students' microbiome samples. - 10
The table shows the relative abundance of three bacterial groups in a person's gut before and after antibiotics. Before antibiotics: Group A 40%, Group B 35%, Group C 25%. After antibiotics: Group A 70%, Group B 10%, Group C 20%. Describe one major change and explain what it suggests about the microbiome.
One major change is that Group A increased from 40% to 70%, while Group B decreased from 35% to 10%. This suggests that antibiotics changed the balance of the microbial community, possibly reducing some groups more than others and allowing Group A to become more dominant. - 11
Explain the difference between a probiotic and a prebiotic. Give one example of each.
Pro- refers to adding helpful living microbes, while pre- refers to feeding microbes already present.
A probiotic is a live microorganism that may provide a health benefit when consumed in adequate amounts, such as certain Lactobacillus or Bifidobacterium strains in yogurt. A prebiotic is a substance that feeds beneficial microbes, such as dietary fiber found in foods like beans, oats, onions, or bananas. - 12
Why should people be cautious about claims that one probiotic product can cure many unrelated diseases?
People should be cautious because probiotic effects are often strain-specific and condition-specific. A product that helps with one condition may not help with another, and health claims should be supported by controlled scientific studies rather than advertising alone. - 13
Describe how the microbiome can interact with the immune system.
Think about both protection from pathogens and regulation of inflammation.
The microbiome can help train the immune system to recognize normal microbes and respond properly to harmful ones. It can also influence inflammation, help maintain barriers such as the gut lining, and compete with pathogens that might trigger immune responses. - 14
A newborn delivered vaginally is often exposed to different microbes than a newborn delivered by C-section. Explain how birth method might influence the early microbiome, and why later factors still matter.
Birth method can influence the early microbiome because vaginal delivery exposes the newborn to microbes from the birth canal, while C-section delivery may expose the newborn more to skin and hospital-associated microbes. Later factors still matter because feeding method, environment, antibiotics, contact with caregivers, and diet continue shaping the microbiome over time. - 15
Design a controlled experiment to test whether a specific prebiotic fiber increases the abundance of a beneficial gut bacterial group in high school volunteers. Include a control group, a variable to measure, and one ethical consideration.
A strong experiment compares groups that are treated the same except for the factor being tested.
A controlled experiment could randomly assign volunteers to a prebiotic fiber group and a control group that receives a similar food without the added prebiotic fiber. Researchers could measure the abundance of the beneficial bacterial group in stool samples before and after the study. An ethical consideration is obtaining informed consent, protecting privacy of biological data, and making sure the supplement is safe for participants.