Bacteria: the good, the bad and the
ugly
Anne Todgham and Annick Gauthier
University of British Columbia
What are bacteria?
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Small organisms - several µm
(1/1000 of a cm, can only see
1/100)
They have all they need to live
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DNA
Energy
Food
Can make proteins
Good and bad bacteria!!!!!!
Bacteria can be killed with
antibiotics
Viruses are different - need host
to “live”
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Can’t kill virus with antibiotics
Rod-like Bacteria
Pictures of Bacteria
Bacteria from Fish
Anthrax
Anabena
Where are bacteria?
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On our skin
In our intestinal tract
 Help us digest food
In our mouth, throat
In the soil
In the ocean
In the forest
On plants
Everywhere!
Good vs Bad
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Some bacteria cause disease
 meningitis
 pneumoniae
 diarrhea
Good bacteria too: for example E. coli
 there are disease-causing strains
 there are digestion-helping strains
Why we should love
bacteria
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Live happily in the guts and lungs of animals
 aid in digestion of food and vitamin production
 stimulate the growth of some of our tissues
Fight foreign disease causing bacteria and prevent them
from infecting us
Important in the cycling of nutrients in the environment ex.
nitrogen and carbon
Make up the bottom of most food webs
 critical for the survival of most living organisms
 thought to be the origin of multicellular organisms
Why bacteria love us
Our bodies provide bacteria with:
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Constant supply of nutrients
Stable environment and constant temperature
Protection
Transportation
We are a great home to live in!!
Interesting tidbits
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1013 bacteria in/on human body, and only 1012
human cells
109 bacteria per gram of feces (population of
world)
Only a very small number of “bad” bacteria
We breathe in 3-4 bacteria per breath
Number one infection: cavities
50% of worlds population dies of infectious
diseases (20% in our society)
Infectious diseases are the leading cause for
taking time off of work
More people died in the Civil War of infectious
disease that by bullets.
More cool bacteria
numbers
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Oldest fossil known is bacteria-like organisms that are 3.5
billion years old!!
100 000 bacteria in each cm2 of skin
1 billion bacteria in a teaspoon of soil
80 distinguishable species of bacteria living in the mouth
alone
Greater than 200 species of bacteria living on the entire
body
Can reproduce every 20 min
Uses for Bacteria
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Production of antibiotics like streptomycin and
nocardicin
Put the tang in yogurt and the sour in sour cream
Vaccination (dead or weak bugs used to boost our
immune system)
Can be used to break down oil after an oil spill
Growing Bacteria
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All the bacteria that we will grow are normal
bacteria that do not cause disease
Bacteria grow in colonies on a substance called
agar that contains sugars and salts
We have poured these agar plates for you
CONDUCT EXPERIMENT
Incubate plates at 37oC at UBC for 2 days
Plates will be stored in fridge until October 23
when we will return to discuss results with you
Materials and Methods
Objective: to culture bacteria from around the classroom and
your body
Materials: 1 LB agar plate, 4 cotton swabs, pencil and paper to
take notes, marker
Method:
1. Using black marker, divide plate into 4 quadrants, label plate
with your name and the date in small letters
2. Choose which 4 areas you will swab and record this in your
science duotang
3. Label the plate with the areas you will swab
 note label the bottom (i.e. agar containing part of the plate)
4. Remove one sterile swab from its packaging (do not touch it),
swab area of choice by gently rubbing cotton swab on it, and
then transferring this to the LB agar plate by gently rubbing
the agar in the designated quadrant
5. Repeat step 4 for 3 other areas of choice
6. Clean up: put LB plate and marker into middle of your table,
put all cotton swabs and wrappers into orange garbage bag
Pictorial of Procedure
Next class:
Growing Bacteria
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thumb
mouth, nose or ear
floor
table
phone
keyboard
light switch
sink
sink faucet
toilet handle
toilet
Culturing Bacteria
Identification of Bacteria
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Grow bacteria on different
media
 Different bacteria grow on
different types of plates
 Check for antibiotic
resistance
Jessica’s expt
Use stains or antibodies
 Gram stain
 Antibodies “agglutinate”
 Clump up bacteria
DNA
 amplify certain genes
How do we defend ourselves?
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Non-specific
 Skin
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Hair
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Shedding cells
 Tears
 Macrophages
 Good bacteria!
Specific
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Antibodies
 B cells
 T cells
Picture of Gastrointestinal Tract
Bacteria of the mouth
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Dental plaque, cavities and periodontal disease
result from the actions initiated by our normal
bacterial flora
60-70% of the volume of plaque is made of
bacteria -- these bacteria release lactic acid that
breaks down the enamel of the teeth and can
cause cavities and further infection of your mouth
Picture of Respiratory System
Life without bacteria
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Normal bacterial flora are very important in protecting our bodies
from pathogenic or disease-causing bacteria
Administration of broad-spectrum antibiotics has a profound
effect on our “good” bacteria and can result in “bad” antibioticresistant bacteria infecting our bodies
Animals raised in an environment filled with bacteria are much
healthier than those raised in a sterile environment
Clean hypothesis
 People need bacteria to live
How can we stay healthy?
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Good nutrition
Low stress
Age
Cleanliness
 but we need bacteria
 antibacterial soaps
Regular doctor and dental
visits
Vaccines up to date