Meet the Microbes!!
Hina´s magical mystery Microbiology
lab!
As you watch the film clip....
Ask yourself the following questions...
a) What THREE words come to mind when you first
see the flat
b) Why do you think James´s flat makes you feel
the way you do?
c) What health risks are posed by keeping the flat
in this condition?
Now look at these pictures...
In groups list 5 differences between them!
Microbes are everywhere!
What is microbiology?
• Discuss the word with the person next to you!
• A little introduction!
• So what are we doing this session?
a)learning ASEPTIC technique
b)learning how to CULTURE bacteria
c) understanding how to classify bacteria
Working with micro-organisms
To produce useful products,
uncontaminated cultures of microbes
are required.
This requires certain precautions and
sterile techniques to be used.
autoclave
Before we begin!
Using micro-organisms
Micro-organisms can be grown by man. They need certain nutrients
which are often contained in an agar medium:
 carbohydrates (energy source)
 mineral ions
 sometimes +protein, vitamins
This is poured into a petri dish.
Contamination
Is when unwanted, possibly harmful
microbes grow. You don’t want this to
happen.
Microbiological techniques
Aberdeen University
1
Lab coat to
protect clothing
Microbes not carried out
2
Hands washed
before & after,
gloves worn
Microbes not carried out
3
5
Sterile petri dishes of
nutrient agar ready
Less chance of unwanted
microbes getting in
(contamination)
4
Autoclave /
pressure cooker
to sterilise
glassware
(>120oC, 20min)
Smooth, non-absorbent
work surface (plastic)
cleaned with disinfectant
before & after
Microbes killed
Microbes killed
Techniques (continued)
6
7
Wire loop &
bottles flamed
before use
Lid held over petri dish
during inoculation
Less chance of unwanted
microbes getting in
Microbes killed
8
Inoculated dish
sealed with tape
Prevents microbes
getting in or out
9
Bin lined with
plastic bag for
safe disposal of
used materials
by autoclaving
Prevents microbes getting
out.
Microbes killed
Now it´s your turn!
1. Find a partner
2. Decide what aspects of bacterial culture you are going to investigate
e.g. The difference between soap and disinfectant
Effectiveness of handwashing?
Bacteria from different parts of your body
Effect of chemicals on bacterial growth
Anything else you can think of!
3. Prepare your work surface and agar plate
4. Innoculate!
5. Seal your petri dish and don´t forget to label it with your names and the date
6. Re-sterilise your work surface
7. Wash your hands!
Classification is the grouping together of things on the basis of
features they have in common.
• In 1996 scientists found the reasons for the reclassification of living
organisms into three domains.
•
Large collaboration of scientists deciphered the full DNA sequence of
every gene of bacteria called Methanococcus jannaschii.
• This archaebacterium lives at 85oC, a temperature lethal for regular
bacteria as well as multicellular plants and animals.
•
Only 44% of this archaebacterium genes resemble those in eubacteria or
eukaryotes.
Differences between organisms of three
domains:
• Histones – proteins associated with the three dimensional structure
of chromosomal DNA, present only in eukaryotic cells.
• Introns – segments of non-coding DNA within genes that are
removed before translation
• Size of ribosomes – bacterial ribosomes (70S) – smaller than
eukaryotic ones (80S).
• Structure of cell walls
• Structures of cell membranes
Classification of Bacteria
• Archaebacteria: extremists
• Eubacteria:
–Heterotrophs
–Photosynthetic autotrophs
–Chemosynthetic autotrophs
Archaea
Archaebacteria (archaios – ancient, bakterion – rod) live in
extreme environments where few other organisms survive.They are
believed to have been the first forms of life on Earth.
•Methanogenic archaebacteria – inhabit anaerobic
habitats and give off methane as a product of their
metabolism. They live in the guts of cattle and are
responsible for the intestinal gases that cattle
produce.
•Halophilic archaebacteria – live only in very salty
conditions such as salt flats, where heat from the
Sun has evaporated sea water.
•Thermoacidophilic archaebacteria – live in hot
acidic springs where temperatures may exceed
100oC and the pH may be as low as 2.
Eubacteria
•Eubacteria (eu –good, true, bakterion – rod) make up the
remaining bacteria.
•They are found in all but the most extreme environments, in soils,
sediments, floating free in air or water, in and on the other
organisms.
•They occur mainly as single cells but also group together in chains
or clusters.
We identify them by:
• Investigating their growth requirements
• Looking at their size and shape
• Studying their reactions to specific stains (such as Gram stain)
To summarise:
• What is meant by the five kingdom
classification system?
• What evidence is there that archaebacteria
were the first forms of life on Earth?
• What are the main differences between
archaebacteria and eubacteria?