Picture source: Bacteria in the ecology of the human body Guiding questions: Why do we care about microbes in the human body? How is the human microbiome like an ecosystem? Why is understanding the human microbiome as an ecosystem helpful to our health? 1 GK-12 Global Watersheds Program, Brenda Gail Bergman, 2013

Source: photo-dictionary.com What are bacteria? Are they in your body right now?

3 What could microbiome mean? What kinds of microbes are in humans?

Group 1: c. What percentage of all the cells in your body are non-human microbial cells? d. For every 100 pounds of your body weight, approximately how many pounds are microbial cells? Group 2: e. The human genome has about 22,000 protein- coding genes. Given this, how many protein-coding genes do you think microbes in the human body have? All groups: a.What role do bacteria play in your body? b.About how many species of bacteria have been identified as living in the human body? 4

Answers More than 10,000 microbial species have been identified as living in human bodies thus far. Microbial cells outnumber human cells in a human body 10:1! Microbes account for only 1-3% of human body weight. The microbiome contributes 8 million protein- coding genes. 5

Group 1: Microbial cells outnumber human cells in a human body 10:1! a.Recalculate the percentage of all the cells in your body that are non-human microbial cells. b. Yet these microbes account for only 1-3% of human body weight. For every 100 pounds of body weight, how many pounds are microbes? c.What does this imply in terms of the weight of microbial cells compared to that of human cells? Group 2: Microbes that occur in the human body have 8 million protein-coding genes, while the human genome has 22,000. d. What percentage of potential protein-coding genes in human bodies are from the microbiome? e.Microbes in the human body contribute how many times more of this vital genetic material than do humans? 6

Summary of what we’ve learned about bacteria in our bodies: More than 10,000 microbial species have been identified as living in human bodies thus far. Approximately 91% of the cells in our bodies are non-human microbial cells The microbiome contributes 99.7% of the genetic material that encodes protein in our bodies. 7 How would you summarize the main point of these statements in one sentence?

source: Scientific American 8 What do scientists mean when they refer to the body as an ecosystem?

Ecosystem What is an ecosystem? 9

Principle of interdependence Organisms in a terrestrial ecosystem. Arrows connect prey to consumer. Colored dots indicate colors in the triangle at the upper right. source: 10 Are each of the members surviving independently?

11 Bacteria in human guts are similar to members of an ecosystem. They have specific nutrient requirements and have a complex dependence on one-another. This is why affecting one group can affect another Principle of interdependence in our bodies

Source: The Great Lakes: An Environmental Atlas and Resource Book Extremely simplified food web What do living organisms use carbon for? How does carbon get from a plant into an animal, or from one animal into another? Principle of energy flow 12

Are these nutrients staying in one place? Are they staying in one form (electron state)? 13 Principle of ecological cycles

Review of the ecological principles we have discussed (note that these are only a subset): An ecosystem is a network of interactions between organisms and their environment Principle of interdependence: members of ecosystems are interdependent Principle of energy flow: energy flows through the system. Principle of ecological cycles: resources are exchanged in continual cycles. As part of this, nutrients move through the ecosystem and are changed into different forms. 14

Source: Society for microbiology General functions of bacteria in the human body Digestive system Source: University of Maryland Medical Center

What is transforming the organic matter into ammonium? What is transforming the N 2 gas into NO 2 ? 16 Principle of ecological cycles applied to the human microbiome: Microbes process B and K vitamins into forms usable by humans.

Source: learnaboutfoodwebs.blogspot.com Where are bacteria on this food web? With respect to food, what is another important role that bacteria could play for animals? 17

2. Immune system Source: University of Maryland Medical Center General functions of bacteria in the human body What is the relationship between bacteria and disease? 18

Pakistan Sweden 19 Why might some kids have less bacteria than others?

Principle of interdependence source: 20 Source: University of Maryland Medical Center Bacteria can train our immune system to recognize and destroy pathogens, especially in early childhood.

 train our immune system to recognize and destroy pathogens.  decrease cancer-causing (carcinogenic) activity  protect against harmful bacteria  produce some antibiotics  reduce respiratory infections, like the common cold Some functions of helpful bacteria to our immune system: 21

General functions of bacteria in the human body 3. Nervous system Have you ever noticed your moods changing based on what you eat? What foods affect your moods? Why could this be? source: histologyolm.stevegallik.org 22

23 affect human and animal psychology, particularly levels of anxiety Some functions of bacteria in our nervous system: What is ‘your second brain’?

24 Medical ecology Many microorganisms in our bodies are critical for our lives Goal: Promote an internal environment that enables helpful bacteria to thrive and outcompete unhelpful bacteria

“Antibiotics are losing their effectiveness at a rate that is both alarming and irreversible... Bacteria are adapting and finding ways to survive the effects of antibiotics, ultimately becoming resistant so they no longer work.” –Sally Davies, PhD Solution for the antibiotic crisis? Source lolalollipop.com

Quorum sensing Bacteria can alter their behavior through chemical interactions. Use chemicals as cooperative signals, cues, and chemical manipulations that affect inter and intra species behavior

27 Some health conditions that have been found to be directly related to the balance of bacteria in the human body: obesity, type 1 diabetes, childhood asthma, inflammatory bowel disease, colorectal cancer, cardiovascular disease, human immunodeficiency, anxiety, respiratory infections. Janoff, Edward N., Claire Gustafson, and Daniel Frank. "The world within: living with our microbial guests and guides." Translational Research (2012).

28 1. Has your doctor mentioned the issue of balancing their bacteria as a possible remedy for health concerns in your family? 2. Have you taken antibiotics over the past 5 years? 3. Does anyone in your family eat certain foods (vegetables, potato chips, sugar, yogurt) much more than other members of your family? 4. Does the person with a different diet get stressed or sick more or less often than the rest of you? 5. Look back on your answers from the beginning of class regarding the role of bacteria in your bodies. Did you think that bacteria are mostly harmful?

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