Download Nature of Microbes

Wellsway School Science Team
Curriculum 2006
Triple Science - Biology workbook
NATURE OF
MICROBES
WORKBOOK
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Tutor Group:____________
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Wellsway School Science Team
Microbes and Mankind
Curriculum 2006
Triple Science - Biology workbook
4. NATURE OF MICROBES
1.
OBJECTIVES:
What are microbes and are there different types?
How are they seen?
How can they be grown?
How were their effects first proved?
By the end of this topic you should:
(a) Know that microbes include bacteria, viruses and fungi. A bacterial cell consists of
cytoplasm, cell membrane and a cell wall. There is no distinct nucleus. Bacteria reproduce by
dividing into two.
(b) Know that viruses are smaller than bacteria. They consist of a protein coat surrounding a
small number of genes and can only reproduce inside a host cell. The production of new viruses
results in the destruction of the host cell and the release of new viruses which can then attack
new cells.
(c) Know that yeasts are fungi. Yeast cells are larger than bacteria and have a nucleus,
cytoplasm and a membrane surrounded by a cell wall. Yeasts reproduce by budding.
(d) Understand the safe use of basic aseptic techniques involved in inoculating, plating and
incubating microbes.
(e) Investigate the presence of bacteria in milk using agar plates.
(f) Explore information about the effect of temperature on the growth of bacteria and understand
its application in food storage.
(g) Understand how Pasteur used scientific method to devise experiments and make
deductions. This resolved the controversy about the, traditionally held, theory of
'spontaneous generation', whereby non-living substances could give rise to life, and proved the
role of micro organisms as the source of food spoilage.
2.
Look at the video, OR MSS presentation OR PowerPoint presentation, OR read your textbook
on GROUPS OF MICROBES. Discuss the different groups of microbes with your teacher.
a. Make a list of the 3 main groups of microbe.
3.
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Construct a BACTERIA FACTFILE, including a LABELLED DRAWING showing the structure of
a bacterium; where bacteria grow; how they reproduce; examples of useful bacteria; common
diseases caused by pathogenic bacteria.
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4.
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Triple Science - Biology workbook
Construct a VIRUSES FACTFILE including a LABELLED DRAWING showing the structure of a
virus; where viruses grow; how they reproduce; the effect of viruses on host cells; common
diseases caused by pathogenic viruses.
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5.
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Construct a YEAST FACTFILE, including a LABELLED DRAWING showing how the size and
the structure of yeast differs from that of a bacterium; where yeasts grow naturally; how they
reproduce; examples of uses made by yeast.
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6.
Curriculum 2006
Triple Science - Biology workbook
Look at the video, OR MSS presentation OR PowerPoint presentation, OR read your textbook
on GROWING MICROBES. Discuss with your teacher how bacteria can be grown on agar
plates. If possible, watch the demonstration of inoculating an agar plate.
Answer the following questions carefully:
a. What is agar?
b. What is nutrient agar?
c. What is a Petri dish?
d. What is a nutrient agar plate?
e. Explain the meaning of the term “aseptic techniques”.
f. Suggest 3 ways of maintaining aseptic conditions when culturing bacteria.
g. Explain clearly how to inoculate bacteria onto a nutrient agar plate.
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Wellsway School Science Team
Curriculum 2006
Triple Science - Biology workbook
h. Explain how bacteria are cultured on a nutrient agar plate.
i.
7.
Draw a typical agar plate which has been inoculated and cultured. Label the small “circles”
and explain how each circle develops.
Investigating the presence of bacteria in milk using agar plates.
You are provided with samples of milk of different freshness. It has been suggested that milk
turns sour because of large numbers of bacteria growing in the milk.
Plan and carry out an experiment to find out whether there are more bacteria in sour milk.
a. Outline of plan.
b. Independent variable.
c. Dependent variable.
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Curriculum 2006
Triple Science - Biology workbook
d. Control variables.
Once you have had your plan approved, set up your agar plates and leave them to incubate for
24 hours at 37°C. Once your plates are set up, cont inue with section 8.
Once your plates have incubated, examine each one (N.B. DO NOT TAKE OFF THE LIDS!),
and draw or describe the appearance of each plate in the results section.
Results.
Conclusion. Explain whether your results support the original idea.
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Curriculum 2006
Triple Science - Biology workbook
Evaluation. Suggest limitations of the techniques used and possible improvements you could
make.
8.
The effect of temperature on the growth of bacteria
In common with all living organisms, the activity of bacteria is controlled by ENZYMES. This
activity includes GROWTH and REPRODUCTION.
In an investigation, harmless bacteria were inoculated onto nutrient agar plates and then
incubated at different temperatures for 24 hours. The number of colonies of bacteria which grew
were counted and recorded. The results are shown in the table below:
Temperature (°C)
No of bacterial
colonies after 24
hrs
0
10
20
30
40
50
60
70
80
0
5
20
43
91
20
4
2
1
a. Draw a line graph in the space below:
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Triple Science - Biology workbook
b. EXPLAIN fully the shape of the graph, at:
(i) Low temperatures
(ii) Medium temperatures
(iii) High temperatures
c. How have the results of this investigation been put to good use by people in the food industry
attempting to find ways of preventing food being spoiled by bacterial decay? List as many
different examples as you can think of to support your answer.
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9.
Curriculum 2006
Triple Science - Biology workbook
Independent research: Louis Pasteur.
Produce 1 or 2 A4 pages highlighting some of the important discoveries made by Louis Pasteur
in the 19th Century.
One of these MUST be the way he proved that microbes (bacteria) did not arise by
'spontaneous generation'.
Another MUST be how he proved the role of micro organisms as the source of food spoilage.
Ensure you include information about how Pasteur used the scientific method to devise
experiments and make deductions.
10. Well done! You have now completed the ‘Nature of Microbes’ topic.
Now you need to revise your work in preparation for the ‘Nature of Microbes’ test.
11. Useful web links:
http://www.bbc.co.uk/schools/gcsebitesize/biology/humansasorganisms/maintaininghealthrev1.shtml
http://www.biotopics.co.uk/pot/yeast1.html
http://www.s-cool.co.uk/topic_principles.asp?loc=pr&topic_id=5&subject_id=17&ebt=49&ebn=&ebs=&ebl=&elc=4
http://www.purchon.com/biology/blood.htm
http://www.revisionworld.co.uk/gcse/biology/humans-organisms/maintaining-health/fighting-infection (general revision site)
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Glossary. (Muddled – sort them out!)
Agar
Outer layer of bacterial, fungal and plant cells
Aseptic
Method of asexual reproduction in yeast
Bacteria
Techniques which prevent the spread of unwanted microbes
Budding
Jelly-like material made from seaweed which bacteria grow on
Group
of simple, single-celled microbes, some of which cause disease
Cell wall
Colony
Breakdown of sugars to alcohol & CO2, e.g. by yeast enzymes
Culture
Varied group, all with microscopic threads or cells e.g. yeast
Decay
Grow microbes (e.g. bacteria or fungi) on a nutrient agar plate
Fermentation
Visible circle containing millions of bacteria, all grown from one
Rotting. Large molecules digested to small ones by bacterial or fungal enzymes
Fungi
Famous French scientist who proved that some microbes cause disease
Inoculate
Incubate
Petri dish containing agar with nutrients for bacterial growth
Louis Pasteur
Microscopic organism, e.g. bacteria, fungi, viruses
Microbe
Introduce microbes onto an area e.g. put bacteria on an agar plate
Nutrient agar plate
Grow microbes at a fixed temperature, usually 37°C
Pathogen
Smallest of all microbes. Can only grow inside other living cells
Petri dish
Completely free from microbes e.g. by boiling or disinfectant
Protein coat
Any microbe capable of causing disease
Spontaneous generation
Group of single-celled fungi important in brewing and baking
Sterile
(False) Idea than living cells can arise from non-living materials
Virus
Outer layer of viruses, surrounding a length of genes
Yeast
Glass or plastic container into which agar is poured to form a plate
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13. Questions.
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Triple Science - Biology workbook
Wellsway School Science Team
10.
Curriculum 2006
Triple Science - Biology workbook
11.
GCSE - WJEC
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