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Types of Bacteria
Label each of the pictures below as either:



Cocci
Bacilli and/or
Spirilla
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Definition of bacteria
Diagram of A bacterial Cell
Diagram of the three different types of bacteria
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Structure and Function of a bacterial cell
Structure
Function
Cell Wall
Cell Membrane
Cytoplasm
Nuclear Material (DNA, RNA,
Chromosomes)
Flagella
Differences between bacteria and animal and Plants Cells
Bacteria
Animal
Plant
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Bacteria reproduce simply by dividing in two in a process called binary fission. The daughter
cells produced are genetically identical to the parent cells unless a mutation occurs when
the DNA is being copied. wo identical DNA molecules migrate to opposite ends of the cell as
a transverse wall forms, dividing the cell in two. The cells can now separate and enlarge to
original size. Under ideal conditions, a bacterium can undergo binary fission every 10-20
minutes producing over 1030 progeny in a day and a half. If sources are unlimited,
exponential growth would be expected.
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Conditions that encourage the of Reproduction in Bacteria
Conditions
Nutrients/ available
food supply
Effect on bacterial rate of reproduction
Oxygen
pH
Moisture Conditions
Temperature
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Growth Rate of different species of bacteria
The time interval required for a bacterial cell to divide or for a population of bacterial cells
to double is called the generation time. Generation times for bacterial species growing in
nature may be as short as 15 minutes or as long as several days.
Generation times for some common bacteria under optimal conditions of growth.
Bacterium
Medium
Generation Time (minutes)
Escherichia coli
Glucose-salts
17
Bacillus megaterium
Sucrose-salts
25
Streptococcus lactis
Milk
26
Streptococcus lactis
Lactose broth
48
Staphylococcus aureus
Heart infusion broth
27-30
Lactobacillus acidophilus
Milk
66-87
Rhizobium japonicum
Mannitol-salts-yeast extract 344-461
Mycobacterium tuberculosis Synthetic
792-932
Treponema pallidum
1980
Rabbit testes
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Bacterial Reproduction Rates
A typical bacterium, Like E. Coli can reproduce at amazing rates. For examples, many divide
at a rate of once every 20 minutes. Using this as an example, complete the table below to
show how many bacteria you would have after 12 hours. Use the graph paper on the
following page to plot this information
Time (Minutes)
0
20
40
60 (1 hour)
Number of
Bacteria
1
2
4
8
Time (Minutes)
Number of
Bacteria
380
400
420 (7 hours)
440
80
460
100
480 (8 hours)
120 (2 hours)
500
140
520
160
540 (9 hours)
180 (3 hours)
560
200
580
220
600 (10 hours)
240 (4 hours)
620
260
640
280
660(11 hours)
300 (5 hours)
680
320
700
340
720 (12 hours)
360 (6 hours)
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Pasture’s Experiment
http://bcs.whfreeman.com/thelifewire/content/chp03/0302003.html
In the 1800’s, the great French scientist Louis Pasture testes the validity of a widely
held belief in spontaneous generation. Or centuries, the general population and
naturalists alike believed that a variety of organisms could arise spontaneously,
without being generated from similar organisms.
Louis pasture was not the first to conduct experiments on spontaneous generation.
For examples, two centuries earlier, in 1668, an Italian physician named Francesco
Redi showed that maggots do not emerge from rotting meat by spontaneous
generation, but instead develop from eggs laid by flies. Although Redi’s experiment
was convincing, most people applies its conclusions only to certain organisms. By
Pasteur’s time, for examples, naturalists generally rejects spontaneous generation
when it came to macroscopic life, such as insects and molluscs, but help on to the
notion when in applied to microscopic life, such as bacteria.
In 1862, Pasteur set up an experiment to refute the notion of spontaneous
generation for microscopic life. He based his experimental design on a number of
observations. He knew that bacteria grow in open containers of meat broth. He also
knew that if the broth is boiled for an hour in a sealed container that remains sealed,
no bacteria will grow in it. Additionally he observes that bacteria are found in dust
particles that float in the air. Armed with this information, Pasture set up a definitive
experiment to test whether microbes arise from pre-existing microbes or are
generated spontaneously.
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Koch’s Postulates
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Penicillium notatum
Gather information about the discovery and the identification of penicillin from the fungus
Penicillium notatum. In the boxs below summarise your research and then present in a 1000
word essay titled ‘Identifying penicillin as an antibiotic.’ Make sure you focus your essay on
the circumstances surrounding the identification of penicillins properties rather than on the
life histories of the men involved. You may include diagrams in your essay where
appropriate.
Louis Pasture
Joseph Lister
Ernest Duchesne
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Alexander Flemming
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Howard Florey
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How Penicillium works
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Other Types of Antibiotics
Name of Antibiotic
Source
Mode of Action
Bacteria that they effect
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 plan, choose equipment and resources for, analyse the risk, implement appropriate
procedures for and perform a first-hand investigation to culture bacteria present in
our surroundings and relate the growth rate to environmental conditions of
temperature
Experiment: Bacteria and their growth rate
Aim: To culture bacteria at different temperatures and compare their growth rate
Hypothesis: If bacteria are grown at 30° C and 4 °C then ..........................................................
……………………………………………………………………………………………………………………………………………….
.
Equipment:



agar plates
Incubator x 2
Known samples of:
o
o
o
o






Inoculating loop
Gloves
Para film to seal agar plates
Bunsen burner
Matches
Permanent Marker
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Risk Assessment:
Risk
Spores released from agar
plates could be breathed in
Prevention
Agar plates are sealed and
never reopened
Growing unknown cultures
that are potentially harmful
Sterilise the tools, lab bench
and hands before inoculating
agar plate
Justification
Bacteria multiply rapidly and
can mutate into forms of
bacteria harmful or even
deadly. The bacteria that
grown may be resistant to
antibiotics.
Do not expose the agar late
to the air unnecessary
amount of time
Do not incubate the plates at
human body temperature
(37 C)
Never reopen the plates
Dispose of the plates
correctly
Method:
1.
2.
3.
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4.
5.
6.
7.
8.
9.
10.
11.
12.
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Results:
Growth rate of different species of bacteria incubated at different temperatures
Number of Cultures/Day
Plate
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1. Compare the growth rate of bacteria at different temperatures in general (2M)
2. In general, did you see any identifiable differences in the growth rate of different
species of bacteria? Explain these observations using your research(2M)
3. Identify the risks associated with culturing bacteria and outline how these risks can
be eliminated or reduced. (4M)
4. Outline how you carried out an investigation to determine the effect of
temperature on the rate of reproduction of bacteria. (5M)
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5. Identify the dependent and independent variables in the investigation you carried
out to determine the effect of temperature on the rate of reproduction of
bacteria. (2M)
6. Explain how the reliability and validity of your experiment could be improved upon
(4M)
7. Write a hypothesis and a matching conclusion related to your investigation carried
out to determine the effect of temperature on the rate of reproduction of
bacteria. (2M)
8. Propose how the investigation you carried out applies the processes that scientists
use to test and validate scientific ideas (such as models, theories or laws). (4M)
9. Identify three factors that determine the rate of reproduction of bacteria and
explain the effect of each. (6M)
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10. Outline the role of “good bacteria” on the skin in inhibiting the reproduction of
disease-causing bacteria on the skin. (4M)
11. From your research, what general conclusions did you reach about the rate of
reproduction of different bacteria? (3M)
12. Write a conclusion (1M)
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The Problem with Penicillin
Read ‘The problem with Penicillin’ on page 213 of Spotlight Senior Science, write a
summary of the information and answer the following questions.
Summary
1. Suggest reasons why a person may require two different types of antibiotic to a
fight a particular infection
2. Propose reasons why a combination of antibiotics with penicillin followed by
erythromycin might be used to treat a particularly difficult or reoccurring infection
3. List the names of 10 different types of antibiotics
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Read March of the Superbugs in Spotlight Senior Science Pages 214-125 and questions 1-7 on
page 215
1.
2.
3.
4.
5.
6.
7.
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