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AGRICULTURAL MICROBIOLOGY
(101 AMB)
• Module 1: history and development
• Module 2: Microorganisms: taxonomic
approach: types of living cells, eukaryotes and
prokaryotes
• Module 3, 4,5: The prokaryotic cell: structure
and function
• Module 6: The prokaryotic cell: Nutrition and
growth
• Module 7: The viruses: structure and
replication
• Module 8,9: Environmental microbiology;
Microorganisms in soil, and microorganisms in
food
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MICROBIOLOGY is a
specialized area of
biology (Gr. bios-life+
logos-to study) that
concerns with the
study of microbes ordinarily
too small to be seen without
magnification.
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Microorganisms
are large and diverse group of
microscopic organisms that
exist
as single cell or cell clusters
(e.g., bacteria, fungi, algae and
protozoa) and the
viruses, which are microscopic
but not cellular.
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Antony van Leeuwenhoek
(pronounced Layu-wen- hoek) was
born on
October 24, 1632 in Delft, Holland (now
Netherlands). In 1674, he made first
observation of microorganisms and was the
first person to observe and
accurately describe and measure
bacteria and protozoa, termed by him,
as
“animalcules” which he thought were
tiny animals.
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Anton Van Leeuwenhoek
First person to see
bacteria
Single lens microscope
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Leeuwenhoek became the
first person to describe spermatozoa
and was one of the earliest to describe
red blood corpuscles. In 1680, he was
elected a fellow of the Royal Society
of London, and with Isaac Newton and
Robert Boyle. He is considered
the father of bacteriology and
protozoology.
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Robert Hooke
Robert Hooke
First report of cell
structure 1665
‘Little boxes’ in
cork : CELL
First illustrated
book on
microscopy
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Spontaneous generation OR Abiogenesis
A doctrine holds that lifeless objects give rise
to living organisms
In another words : living things spontaneously
originated from non-living things
Or living things do not need parents
This concept was believed by scientists
for 2000 years
Life origin debates
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proves of Spontaneous
Generation
1-Maggots arise from rotten
(putrid) meat
2- Rates from dirty hey and
trash
3- Frogs from mud
4- Sour juice by microbes
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Francesco Redi
Italian poet physician 1668
Tested hypothesis of Spontaneous
Generation
– Meat in jars
jars open to air> maggots
jars sealed >no maggots
jars fine net>no maggots
Concluded spontaneous generation did not
still occur
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Louis Pasteur
Confirmed experiments of
Redi
Filtration Experiments
– air filtered through guncotton
– dissolve guncotton
– Examined residue
– contained microbes and dust
Conclusion: microbes in
the dust not in air
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Final Proof
Swan-Necked Flask Experiment
Add broth to flask
Bend the neck of the flask(air can enter but
dust cannot)
Heat broth
No bacterial growth
Break neck of flask
– dust enters
– Growth occurs
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Fermentation
Vintners thought sugar chemically
converted to alcohol in air
Pasteur, a chemist, was asked to help
Discovered
– Yeast convert sugars to alcohol
– Bacteria change alcohol to vinegar
Fermentation is a biological process
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Fermentation and Pasteurization
Pasteur- why did wine sour?
Believed at time, that converted sugars
into alcohol
Yeasts do the work of fermentation
Bacteria cause spoilage (Lactic acid
bacteria)
Pasteurization
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Pasteurization
Pasteur connected food
spoilage and microbes
Pasteurization: Destroy
microbes that cause
spoilage by heat
– Beer, wine, milk
Critical to development
of Germ theory
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Germ Theory of Disease
Causal relationship between microbes and
disease
Disinfection controls surgical infection
Microbes cause disease
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Robert Koch
Confirmed germ theory
Discovered cause of
– anthrax
– cholera
– tuberculosis
Developed
– pure culture techniques
– staining techniques
– solid media
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Koch’s postulates
1) Pathogen is present in abundance only in
the sick animal showing disease symptoms.
2) The pathogen can be isolated from the sick
organism and cultivated on artificial medium.
3)The same symptoms appear on healthy
animal infected with the pathogen
4) Pathogen can be isolated again from
artificially infected animal
Rules to prove an organism
causes a disease
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Two reasons for rapid
Advances in Microbiology
1- Rapid advances in Microscopy :
Light microscopes:
A- Simple Leeuwenhook “Single lens
microscope” magnifies 300X
B- Roobert Hook compound
microscope with multi-lens
structure magnifies 1000 X
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Fluorescent microscope
1- uses Ultra violet light
2- Lenses are quartz
3- Needs monitors with U.V sensitive
screens
4- magnification “few thousands X “
5- Can visualize particles of as low as
0.1 µ diameter
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Electron microscope
1- Uses electron radiations (e- beam)
2- Has electromagnetic fields instead of
lenses
3- Needs monitors with e- sensitive
screens.
4- Magnification 10 – 100,000 X
5- Can visualize nano-sized particles” 10
nanometer.
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The five Major Groups of the Microbial
World
1. Bacteria, actinomycetes and Archeae
2. Fungi
3. Algae
4. Protozoa
5. Viruses
Major Features
1- Small size 2- Diverse
appearance 3-Diverse genetics
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Branches of Applied
Microbiology
1- Medical Microbiology including
immunology
2- Food and dairy Microbiology
3- Public health Microbiology
4- Industrial Microbiology
5- Agricultural Microbiology
6- Environmental Microbiology
7- Soil Microbiology
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Modern developments in
Microbiology
Bacteriology
Mycology
Parasitology
Immunology
Virulogy
Recombinant DNA technology
