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?
Picture source: http://healthylifestylealternatives.com/archives/tag/healthy-eating
GK-12 Global Watersheds Program, Brenda Gail Bergman, 2013
1
Source: photo-dictionary.com
What are bacteria?
Are they in your body right now?
𝑆𝑜𝑢𝑟𝑐𝑒: 𝑁𝑎𝑡𝑖𝑜𝑛𝑎𝑙 𝐼𝑛𝑠𝑡𝑖𝑡𝑢𝑡𝑒𝑠 𝑜𝑓 𝐻𝑒𝑎𝑙𝑡ℎ
What could microbiome mean?
What kinds of microbes are in humans?
3
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?
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 proteincoding genes . Given this, how many protein-coding
genes do you think microbes in the human body have?
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 proteincoding genes.
http://commonfund.nih.gov/hmp/overview.aspx
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.
How would you summarize the main point of
these statements in one sentence?
7
source: Scientific American
What do scientists mean when they refer to the body as an
ecosystem?
8
Ecosystem
http://www.chesapeakebay.net/discover/bayecosystem
What is an ecosystem?
9
Are each of the members surviving independently?
Organisms in a terrestrial ecosystem. Arrows connect prey to consumer. Colored dots indicate colors in the triangle at the upper
.
right source: http://wwwrcamnl.wr.usgs.gov
Principle of interdependence
10
Principle of interdependence in our bodies
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
http://scitechdaily.com/hmp-maps-the-healthy-human-microbiome/
11
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
Source: The Great Lakes: An Environmental Atlas and Resource Book
12
Principle of ecological cycles
http://www.eea.europa.eu/
Are these nutrients staying in one place?
Are they staying in one form (electron state)?
13
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
General functions of bacteria in the human body
1. Digestive system
Source: Society for microbiology
Source: University of Maryland Medical Center
15
http://www.eea.europa.eu/
What is transforming the organic matter into ammonium?
What is transforming the N2 gas into NO2?
Principle of ecological cycles applied to the human microbiome:
Microbes process B and K vitamins into forms usable by humans.
16
Where are
bacteria on this
food web?
With respect to
food, what is
another
important role
that bacteria
could play for
animals?
Source: learnaboutfoodwebs.blogspot.com
17
General functions of bacteria in the human body
2. Immune system
What is the
relationship
between
bacteria and
disease?
Source: University of Maryland Medical Center
18
Pakistan
Why might some kids
have less bacteria than
others?
http://wondersofpakistan.wordpress.com/
Sweden
http://yourlivingcity.com/
19
source: http://wwwrcamnl.wr.usgs.gov
Bacteria can train our immune
system to recognize and destroy
pathogens, especially in early
childhood.
Principle of interdependence
Source: University of Maryland Medical Center
20
Some functions of helpful bacteria to our immune
system:
 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
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
What is
‘your second
brain’?
Some functions of bacteria in our nervous system:
affect human and animal psychology, particularly levels
of anxiety
23
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
www.quora.com
24
Solution for the antibiotic crisis?
Source lolalollipop.com
“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
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
http://www.bmglabtech.com/application-notes/luminescence/quorum-sensing-199.cfm
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).
http://www.sciencemag.org/content/326/5960/1694.abstract
27
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?
28
http://wenchwisdom.blogspot.com/2012/06/this-just-in-and-awesometending-human.html
29