Microorganisms
Where do microbes live?
Where do microorganisms live?
Where in the classroom do you think we would
find the most microorganisms?
Gather Round
How can we grow microorganisms?
Microbiologists grow bacteria and fungi on agar
plates.
Agar is special jelly; it contains all the nutrients
bacteria and fungi need to grow.
Molten agar is poured in Petri dishes.
Step 1
bottom with agar
lid
lid
bottom with agar
Turn your Petri dish upside down
Step 2
bottom
On the bottom of your Petri dish write your initials and the date
Step 3
bottom
Mark the bottom of your Petri dish into quarters
Step 4
bottom
In each quarter write what you are swabbing
Step 5
lid
bottom with agar
bottom with agar
lid
Flip over your Petri dish so the lid is back on top
Dip one of your cotton buds in water and rub what you want to test
Step 6
Take the lid off your Petri dish
Wiggle your cotton bud on the agar GENTLY
Remember to
put it in the
right quarter
Step 7
Put the lid back on your Petri dish between each test
Put the used cotton bud in Vircon and use a new one for the next test
Step 8
When you have tested 4 objects seal your dish with 4 pieces of sellotape
Tips
 Write around the edge of the Petri dish
 The dustiest objects don’t necessarily have the most
microbes
 Only seal the Petri dish at 4 points
 When you’re finished wash your hands
Complete record sheet
Include:
- your name
- what you swabbed
Remember to
write around
the edge
Predictions
What do you think the dirtiest object in the
classroom is going to be?
What do you think the agar plates will look like
on Thursday?
Microorganism Reproduction
The number of microorganisms doubles
every 20 minutes…
…if you start with 1 microbe how many will
there be after 4 hours?
0 minutes = 1 Bob
20 minutes = 2 Bobs
40 minutes = 4 Bobs
60 minutes = 8 Bobs
80 minutes = 16 Bobs
100 minutes = 32 Bobs
120 minutes = 64 Bobs
140 minutes = 128 Bobs
160 minutes = 256 Bobs
180 minutes = 512 Bobs
200 minutes = 1024 Bobs
220 minutes = 2048
240 minutes = 4096
260 minutes = 8192
280 minutes = 16,384
Microbe Multiplication Song!
http://www.youtube.com/watch?v=5Xi2Nc1UicQ
Where do microbes live?
DO NOT open your Petri dishes
Is it round and smooth? You have found bacteria
Is it hairy or fuzzy? You have found fungi
What colour is it? What size is it?
Different colours and size mean different types of
bacteria/fungi.
Where do microbes live?
1.
2.
3.
4.
Write the title “where do microbes live?” in your jotter
Stick the records of your swabbing in your jotter
Draw your results on your record sheet
Copy the table below (use a ruler)
Object
Scale of microbial growth
How much growth?
Complete your results table using the diagram below
to help you decide how much growth is on your plate.
Completely covered in growth
3
2
Mostly covered in growth
Nothing is growing
0
1
A couple areas of growth
What is the dirtiest object in the classroom?
Object
Scale of microbial growth
Average growth
Next day...
What do microorganisms need to live?