history and scope1
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The Microbial World and You
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What is Microbiology?
Microbes, or microorganisms are minute
living things that are usually unable to be
viewed with the naked eye.
What are some examples of microbes?
Bacteria, fungi, protozoa, algae, viruses
are examples!
Some are pathogenic
³Germ´ refers to a rapidly growing cell.
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What is Microbiology?
Microbes:
Decompose organic waste
Are producers in the ecosystem byphotosynthesis
Produce industrial chemicals such asethyl alcohol and acetone
Produce fermented foods such as vinegar,cheese, and bread
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: Introduction to Microbiology, History & scope
Microbiology:
- In the broadest sense, microbiology is the study of all organisms that are invisible to
the naked eye-that is the study of microorganisms.
- Its subjects are viruses, bacteria, many algae and fungi, and protozoa.
- The importance of microbiology and microorganisms can not be overemphasized.
- Microorganisms are necessary for the production of bread, cheese, beer, antibiotics,
vaccines, vitamins, enzymes, etc.
- Modern biotechnology rests upon a microbiological foundation.
Microorganisms:
- Microorganisms are everywhere; almost every natural surface is colonized by
microbes, from body to ocean. Some microorganisms can live hot springs, and others in
frozen sea ice.
- Most microorganisms are harmless to humans; You swallow millions of microbes
every day with no ill effects. In fact, we are dependent on microbes to help us digest our food.
- Microbes also keep the biosphere running by carrying out essential functions such as
decomposition of dead animals and plants. They make possible the cycles of carbon,
oxygen, nitrogen and sulfur that take place in terrestrial and aquatic systems.
- Microorganisms have also harmed humans and disrupted society over the millennia.
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What is Microbiology?
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What is Microbiology?
Knowledge of Microbes allows humans to
Prevent food spoilage
Prevent disease occurrence
Led to aseptic techniques to prevent
contamination in medicine and in
microbiology laboratories.
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History of Microbiology
Ancestors of bacteria were the first life on Earth.
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History of Microbiology
The first microbes were observed in 1673.
In 1665, Robert Hooke (Englishman) reportedthat living things were composed of little
boxes or cells.
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History of Microbiology
1673-1723, Antoni van
Leeuwenhoek (Dutch)
described live
microorganisms thathe observed in teeth
scrapings, rain water,
and peppercorn
infusions.
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History of Microbiology
Many believed spontaneous generation:
life can arise from non-living matter
In 1668, the Italian physician Francesco
Redi performed an experiment to disprove
spontaneous generation.
Can you think of an experiment that could
disprove spontaneous generation?
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History of Microbiology
Conditions Results
3 jars covered with fine
net
No maggots
3 open jars Maggots appeared
From where did the maggots come?
What was the purpose of the sealed jars?S pontaneous generation or biogenesis?
Redi filled six jars with decaying meat.
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Supported by:
Aristotle (384-322 BC) ± Believed that simple invertebrates
could arise by spontaneous generation
John Needham (1713-1781) ± Boiled mutton broth, then
sealed and still observed growth after a period of time
LazarroS
pallanzani (1729-1799) No growth in sealed flask after boiling ± proposed that air was needed for growth of
organisms
Felix Pouchet (1859) ± Proved growth without
contamination from air
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Disproved by:
Francesco Redi (1626-1697) ± maggotunable to grown on meat if meat was
covered with gauze Schwann, Friedrich Schroder and vonDusch (1830s) ± Air allowed to enter flask but only after passing through a heated
tube or sterile wool
John Tyndall (1820-1893) ± Omission of dust no growth. Demonstrated heatresistant forms of bacteria (endospores)
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Spontaneous Generation Myths
Snakes from horse hairs in stagnant water
Mice from grain and cheese wrapped in a sweater
Maggots from rotting meat
Fleas from hair
Flies from fresh and rotting fruit Mosquitoes from stagnant pondwater
Eels from slimy mud at the bottom of the ocean
Locusts from green leaves
Raccoons from hollow tree trunks
Termites are generated from rotting wood
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History of Microbiology
Rudolf Virchow (German) presented
biogenesis: living cells can arise only from
preexisting cells.
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History of Microbiology
So now there are two hypotheses:
The hypothesis that living organisms arise
from nonliving matter is called spontaneousgeneration. According to spontaneous
generation, a ³vital force¶ Forms life.
The Alternative hypothesis, that the living
organisms arise from preexisting life, is
called biogenesis.
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History of Microbiology
1861: Louis Pasteur demonstrated that
microorganisms are present in the air.
Conditions ResultsNutrient broth placed in
flask, heated, not sealed
Microbial growth
Nutrient broth placed in
flask, heated, thensealed
No microbial growth
S pontaneous generation or biogenesis?
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History of Microbiology
Next experiment, Pasteur¶s S-shaped flask kept
microbes out but let air in. These experiments
form the basis of aseptic technique
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History of Microbiology
The Golden Age of Microbiology
1857-1914
Beginning with Pasteur¶s work, discoveries
included the relationship between microbes
and disease, immunity, and antimicrobialdrugs
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History of Microbiology
Pasteur showed that microbes are
responsible for fermentation.
Fermentation is the conversation of sugar toalcohol to make beer and wine.
Microbial growth is also responsible for
spoilage of food.
Bacteria that use alcohol and produce acetic
acid spoil wine by turning it to vinegar (acetic
acid).
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History of Microbiology
Pasteur demonstrated that
these spoilage bacteria
could be killed by heat that
was not hot enough to
evaporate the alcohol in
wine. This application of a
high heat for a short time
is called pasteurization.
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History of Microbiology
The Germ Theory of Disease
1835: Agostino Bassi showed a silkworm
disease was caused by a fungus.
1865: Pasteur believed that another silkworm
disease was caused by a protozoan.
1840s: Ignaz Semmelwise advocated
handwashing to prevent transmission of
puerperal fever from one patient to another.
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Chapter 1 The Microbial World and You
History of Microbiology
The Germ Theory of Disease
1860s: Joseph Lister used a chemical
disinfectant to prevent surgical woundinfections after looking at Pasteur¶s work
showing microbes are in the air, can spoil
food, and cause animal diseases.
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History of Microbiology
The Germ Theory of Disease
1876: Robert Koch provided proof that a
bacterium causes anthrax and provided the
experimental steps, Koch¶s postulates, used
to prove that a specific microbe causes a
specific disease.
Koch was a physician and Pasteur¶s youngrival
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K och¶s Postulates:
- Microorganism must be present in every case of the disease but absent from healthy
individuals.
- The suspected microorganism must be isolated and grown in pure cultures.
- The disease must result when the isolated microorganism is inoculated into a healthy
host.
- The same microorganism must be isolated from the disease host.
Isolation of Microorganisms:
- During Koch¶s studies, it became necessary to isolate suspected bacterial pathogens.- He cultured bacteria on the sterile surfaces of cut, boiled potatoes Not satisfactory.
- Regular liquid medium solidified by adding gelatin gelatin melted @ T>28°C.
- Fannie Eilshemius suggested use of agar; 100°C to melt, 50 °C to solidify.
- Richard Petri developed petri dish, a container for solid culture media.
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Louis Pasteur (1822 1895):
- Developed vaccines for Chickenpox, anthrax, rabies
- Demonstrated that all fermentations were due to theactivities of specific yeasts and bacteria.- Developed Pasteurization to preserve wine duringstorage. Important: Foods
- Discovered that fermentative microorganisms wereanaerobic and could live only in absence of oxygen.
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OtherDevelopments«
- Winogradsky made many contributions to soil microbiology; discovered that soil
bacteria could oxidize Fe, S and ammonia to obtain energy.
- Isolated Anaerobic nitrogen-fixing bacteria; studied the decomposition of cellulose.
- Together with Beijerink , developed the enrichment-culture technique and the use of selective media.
- Early 40¶s, Microbiology established closer relationship with Genetics and
Biochemistry; microorganisms are extremely useful experimental subjects.
- e.g. Study of relationship between genes and enzymes; evidence that D NA is the
genetic material;- Recently, Microbiology been a major contributor to the rise of Molecular Biology.
- Studies on Genetic code; mechanisms of D NA, R NA, and Protein synthesis;
regulation of gene expression; control of enzyme activity.
- Development of RecombinantDNA Technology and Genetic Engineering.
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Scope of Microbiology:
- Many microbiologists are primarily interested in the biology of microorganisms, while others focus on specific groups;
- Microbiology has an impact on medicine, agriculture, food science, ecology,
genetics, biochemistry, immunology, and many other fields.
- Virologists - viruses
- Bacteriologists - bacteria
- Phycologists ± algae
- Mycologist -fungi
- Protozoologists ± protozoa
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- Medical Microbiology: deals with diseases of humans and animals; identify and plan
measures to eliminate agents causing infectious diseases.
- Immunology: study of the immune system that protects the body from pathogens.
- Agricultural Microbiology: impact of microorganisms on agriculture; combat plant
diseases that attack important food crops.
- Food and Dairy Microbiology: prevent microbial spoilage of food & transmission of
food-borne diseases (e.g. salmonellosis); use microorganisms to make food such as
cheeses, yogurts, pickles, beer, etc.
- Industrial Microbiology: using microorganisms to make products such as antibiotics,
vaccines, steroids, alcohols & other solvents, vitamins, amino acids, enzymes, etc.
- Genetic Engineering: Engineered microorganisms used to make hormones,
antibiotics, vaccines and other products.
- Since viruses are acellular and possess both living and nonliving characteristics, theyare considered neither prokaryotic nor eukaryotic. They will be discussed in separate
section of the course.