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Introduction
Microbiology 2011
What is a microbiology?
• Study of living organisms of microscopic size, which
include bacteria, fungi, algae, protozoa and the
infectious agents at the borderline of life that are
called viruses.
Why study microbiology?
• Nutrient production
• Decomposition
• Biotechnology
– production of foods, drugs and vaccines
• Genetic engineering
• Bioremediation
• Infectious disease
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Why study microbiology?
• Microorganism are closely associated with the health
and welfare of human beings; some are beneficial and
others are detrimental.
• Microorganisms have some characteristics which
make them ideal specimen for the study of numerous
fundamental life processes.
• Microorganisms have a wider range of physiological
and biochemical potentialities than all other
organism.
• Eg. Some bacteria are able to utilize atmospheric
nitrogen for the synthesis of proteins and other
complex nitrogenous compounds.
• Some microorganisms synthesize all their vitamins.
Major Field of applied Microbiology
1. Medical Microbiology- causative agents of disease
and diagnostic procedure for identification of
causative agent; preventive measures.
2. Aquatic microbiology: water
microbiological
examination;
degradation of waste, ecology.
purification,
biological
3. Aero microbiology: contamination and spoilage,
dissemination of diseases.
4. Food microbiology: food preservation and
preparation, food borne diseases and their prevention.
5. Agricultural microbiology: soil fertility, plant and
animal disease.
6. Industrial microbiology: production of medicinal
products such as antibiotics and vaccines, fermented
beverages, industrial chemicals, production of
proteins and hormones by genetically engineered
microorganisms.
7. Exomicrobiology: exploration for life in outer space.
8. Geochemical microbiology: coal, minerals and gas
formation, prospect for deposits of coal, oil and gas;
recovery of minerals from low grade ions.
History of microbiology
• Microbiology began when people learnt to
grind lenses from pieces of glass and combine
them to produce magnification great enough to
enable microbes to be seen.
Antonie van Leeuwenhoek
• First to observe living
microbes
• His single-lens
magnified up to 300X
(1632-1723)
History
• In 13th century Roger Bacon (1220-1292)Diseased is produced by invisible living
creatures.
• Girolamo Fracastro (1483-1553)- First to
recognize the existence of tiny particles. These
tiny particles cause a contagious disease by
direct contact.
Spontaneous Generation versus Biogenesis.
• Aristotle (384-322 B.C)- animal might originate
spontaneously from the soil, decaying food, warm rain and
even dirty shirts.
• Virgil (70-19B.C)- maggot could be produced by exposing
meat to air and warmth.
• Francesco Redi (1626-1697): he placed a meat in a jar and
covered with a gauge. Attracted by the odor of the meat, flies
laid eggs on the covering, and from the egg maggot developed.
1947, John Needham- while experimenting with meat exposed
to hot ashes,
• observed the appearance of organism not present at the start of
the experiment.
• He concluded that the bacteria originated from meat.
• Lazarro Spallanzani(1729-1790): Boiled beef broth
for an hour and then sealed the flasks.
• No microbes appeared following incubation.
• It failed to convince Needam, who insisted that air is
essential to the spontaneous production of
microscopic beings and that it had been excluded
from the flask by sealing them.
• Frantz Schule (1815-1873) passed air into his flask
through red-hot tubes. In neither case did microbes
appear.
• H.Schroder and T. Von Dusch: performed a more
convincing experiment by passing air through cotton
into flask containing heated broth.
Thus, the microbes were filtered out of air by the
cotton fibres
so that the growth did not occur and
a basic technique of plugging bacteria culture.
Spontaneous Generation Theory
• Spontaneous generation
– “Living things arise from nonliving things”
– Belief that some forms of life could arise from vital forces
present in nonliving or decomposing matter
• Maggots found in rotting meat arose from a nonliving factor
• Microorganisms found in broth that made it cloudy appeared from a
nonliving factor
• Germ theory of disease:
– “Microorganisms can invade other organisms and cause
disease”
– Many diseases are caused by the growth of microbes in the
body and not by sins, bad character, or poverty, etc.
Germ Theory of Disease
Theory of biogenesis
• Louis Pasteur:
– Worked in the wine industry
• Had knowledge about yeast
producing alcohol
-Goose-neck flasks
– Tipping the flask would allow the
microbes to enter the infusion
• Cause them to become cloudy
• Main experiment that helped
disprove spontaneous
generation
Louis Pasteur
• Louis Pasteur performed experiment that ended the
argument of all time.
• “There is no condition today in which you can affirm
that microscopic beings come into the world without
germ, without parents like themselves”
• he prepared a flask with a long narrow goose neck
opening.
• The nutrient were heated in the flask
• air untreated and unfiltered could pass in or out but
germ settle in the goose neck and
• no microbes appeared in the solution.
Louis Pasteur
•Pasteur discovered that some yeasts made good
tasting wine
•Mixtures of microbes competed with yeast and
made wine taste oily or sour
•Developed Pasteurization to deal with this
problem
–Heated the wine to 56°C without oxygen present for
30 minutes
•Developed a rabies vaccine
• Fermentation- with the final result of Pasteurization
• He found fermentation of fruits and grains resulting
in alcohol was brought about by microbes.
• He suggested that undesirable types of microbes
might be removed by heating not enough to hurt the
flavor of the fruit juice but enough to destroy a very
high percentage of microbial population.
• Heating juice at a temperature of 62.8 degree (145ºF)
for half an hour did the job.
• Developed immunization for anthrax in cattle and
rabies in human.
• No one knew what caused infections when Louis
Pasteur was a boy in the early 1800s.
• No one knew that germs spread disease.
• There were no antibiotics or other drugs.
• Many people died from infections.
• Pasteur discovered that bacteria cause many diseases.
• He showed that bacteria get into living things and
then multiply.
• He proved that diseases could be cured by stopping
the spread of bacteria.
• This important discovery is called the germ theory of
disease.
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HOW PASTEUR HELPED INDUSTRY
Louis Pasteur was born in France in 1822.
He studied physics and chemistry in Paris.
As a professor of chemistry, he worked on problems
that affected French industry.
The wine-making industry in France was in trouble
during the mid-1800s because much of the wine was
spoiling.
Pasteur discovered that germs were getting into the
wine and turning it sour.
He found that heat killed these germs and prevented
the wine from spoiling..
• Pasteur later applied his discovery to milk.
• His way of heating foods to kill bacteria is
now called pasteurization.
• Pasteur then discovered how to make vaccines to
protect people and animals against disease.
• He observed that animals infected with a disease
sometimes became immune to the disease—that is,
protected from getting the disease again.
• Pasteur found that he could weaken germs in his
laboratory.
• When he put weakened germs into the bodies of
animals, the animals became immune to the disease
caused by the germs.
• Pasteur made a vaccine to protect sheep against a
disease called anthrax.
Louis Pasteur (1822-1895)
• Showed microbes caused fermentation and spoilage
• Disproved spontaneous generation of
microorganisms
• Developed pasteurization
• Demonstrated what is now known as Germ Theory
of Disease
• Developed a rabies vaccine and
vaccine for Anthrax in cattle.
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Robert Koch
• Robert Koch
– Linked a microscopic organism with a
specific disease (anthrax)
– Developed method to grow bacteria in
pure cultures (cultures containing only
one kind of organism)
• Used solidified gelatin from potato
slices mixed with agar
• Creates a firm surface that microbes
could grow on
Robert Koch
Robert Koch- Microbes cause disease in animals.
•
While studying the anthrax disease in cattle, Koch
found rod shaped organisms in the blood of the
disease animals.
• To test if these organisms were the causative agent
of the disease, he injected healthy mice with the
blood of the diseased animal.
• To his surprise he found that the disease was
transmissible to the mice.
• He removed a piece of spleen from the diseased
mice and transferred it to a sterile serum and obtained
a good growth of the rod-shaped organism.
• By injecting these organism into healthy animals, he
was able to reproduce the disease.
• from these studies he was able to lay down certain
basic criteria for the identification of microorganism
as causative agent of disease.
• These criteria are known as Koch’s postulates.
Koch’s Postulates
1. A specific organism can always be found in
association with a given disease.
2. The organism can be isolated and grown in pure
culture in the laboratory.
3. The pure culture will produce the disease when
inoculated into a susceptible animal.
4. It is possible to recover the organism in pure culture
from the experimentally injected animals.
Koch’s Postulate
• The microorganism must be present in every case of
the disease but absent from healthy organism.
• The suspected microorganism must be isolated and
grown in a pure culture.
• The same disease must result when the isolated
microorganism is inoculated into a healthy host.
• The same microorganism must be isolated from the
diseased host.
END