Biology of microorganisms

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Chapter 1
Microorganisms and Microbiology
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Chapter outline
1.1 What is a microbe? 1.2 The importance of
Microbiology 1.3 Microbes in our lives 1.4 The
history of microbiology 1.5 Important events in
the development of microbiology
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Concepts

• Microorganisms are responsible for many of the
  changes observed in organic and inorganic matter
  (e.g., fermentation and the carbon, nitrogen and
  sulfur cycles that occurred in nature.
• The development of microbiology as a scientific
  discipline has depended on the availability of
  the microscope and the ability to isolate and
  grow pure cultures of microorganisms.
• Microbiology is a large discipline, which has a
  great impact on other areas of biology and
  general human welfare

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1.1 What is a microbe?
The word microbe (microorganism) is used to
describe an organism that is so small that can
not be seen without the use of a microscope.
Viruses, bacteria, fungi, protozoa and some algae
are all included in this category.
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Our world is populated by invisible
creatures too small to be seen with the unaided
eye. These life forms, the microbes or
microorganisms, may be seen only by magnifying
their image with a microscope.
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Microbial world
Organisms (living)
Infectious agents (non-living)
Prokaryotes (unicellular)
eukaryotes
viruses
viroids
prions
Eubacteria
Archaea
Algae (unicellular or multicellular)
Fungi (unicellular or multicellular)
Protozoa (unicellular)
Other (multicellular organisms)
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The size and cell type of microbes
Most of the bacteria, protozoa, and fungi are
single-celled microorganisms, and even the
multicelled microbes do not have a great range of
cell types. Viruses are not even cells, just
genetic material surrounded by a protein coat and
incapable of independent existence.
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The size and cell type of microbes
Microbe Approximate range of sizes Cell type
Viruses 0.01-0.25µm Acellular
Bacteria 0.1-10µm Prokaryote
Fungi 2µm-gt1m Eukaryote
Protozoa 2-1000µm Eukaryote
Algae 1µm-several meters Eukaryote
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1.2 The importance of microbiology
Microbes impinge on all aspects of life, just a
few of these are listed below
Food
The environment
Medicine
Biotechnology
Research
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• The environment
• Medicine
• Food
• Biotechnology
• Research

Press here to continue
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Microbes are responsible for the geochemical
cycles. They are found in association with plants
in symbiotic relationships. Some microbes are
devastating plant pathogens, but others may act
as biological control agents against diseases.
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The disease-causing ability of some microbes is
well known. However, microorganisms have also
provided us with the means of their control in
the form of antibiotics and other medically
important drugs.
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Microbes have been used to produce food, from
brewing and wine making, through cheese
production and bread making, to the manufacture
of soy sauce. But microbes are also responsible
for food spoilage.
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Traditionally microbes have been used to
synthesize important chemicals. The advent of
genetic engineering techniques has led to the
cloning of polypeptides into microbes.
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Microbes have been used as model organisms for
the investigation of biochemical and genetical
processes. Millions of copies of the same single
cell can be produced very quickly and give plenty
of homogeneous experimental material. Most people
have no ethical objections to experiments with
these microorganisms.
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1.3 Microbes in our lives

• Microorganisms as Disease Agents
• Microorganisms and Agriculture
• Microorganisms and the Food Industry
• Microorganisms, Energy, and the Environment
• Microorganisms and the Future

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Microbial physiology
Microbial genetics
Microbial Morphology
Virology
Parasitology
Branches of Microbiology
Mycology
Protozoology
Bacteriology
Microbial ecology
Molecular biology
Microbial taxonomy
Phycology or Algology
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The future of microbiology is bright
Microbiology is one of the most rewarding of
professions, because it gives its practitioners
the opportunity to be in contact with all the
other natural science and thus to contribute in
many different ways to the betterment of human
life.
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1.4 The history of microbiology
In the field of observation, chance favors only
prepared minds.
------ Louis Pasteur
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The discovery of microorganisms
The spontaneous generation conflict
The recognition of microbial role in disease
The discovery of microbial effects on organic and
inorganic matter
The development of microbiology in this century
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The discovery of microorganisms
Antony van Leeuwenhock (1632-1723)
The first person to accurately observe and
describe microorganisms
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The first person to observe and describe
microorganisms was the amateur microscopist
Antony van leeuwenhoek of Delft, Holland.
Leeuwenhock made his simple, single-lens
microscope which could amplify the object being
viewed 50 300 times. Between 1673-1723, he
wrote a series of letters to the Royal Society of
London describing the microbes he observed from
the samples of rainwater, and humam mouth.
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lens
Object being viewed
A drawing of one of the microscopes showing the
lens a mounting pin b and focusing screws c and
d.
adjusting
screws
Leeuwenhoeks drawings of bacteria from the human
mouth.
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Louis Pasteur (1822 1895)
Pasteurs contributions

• Pasteur (1857) demonstrated that lactic acid
  fermentation is due to the activity of
  micro-organisms
• Pasteur (1861) conflict over spontaneous
  generation birth of microbiology as a science
• Pasteur (1881) developed anthrax vaccine
• Pasteurization

Louis Pasteur working in his laboratory
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The spontaneous generation conflict

• Spontaneous generation that living
  organisms could develop from nonliving or
  decomposing matter.

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Pasteurs swan neck flasks used in his
experiments on the spontaneous generation of
microorganisms
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Conclusion Microorganisms are not spontaneously
generated from inanimate matter, but are
produced by other microorganisms
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Robert Koch (1843 1910)
The recognition of microbial role in disease
Robert Koch in his laboratory
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Kochs demonstration of special organisms cause
special diseases
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Kochs postulates

• The microorganisms must be present in every case
  of the disease but absent from healthy organisms.

• The suspected microorganisms must be isolated and
  grown in a pure culture.

• The disease must result when the isolated
  microorganisms is inoculated into a healthy host.

• The same microorganisms must be isolated again
  from the diseased host

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The Golden age of microbiology

• Koch and pure cultures

• Fermentation and Pasteurization

• Germ theory of disease

• Vaccination

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The discovery of microbial effects on organic and
inorganic matter

• The Russian microbiologist Winograsky discovered
  that soil bacteria could oxidize iron, sulfur and
  ammonia to obtain energy, and also isolated
  nitrogenfixing bacteria.
• Beijerinck made fundamental contributions to
  microbial ecology. He isolated Azotobacter and
  Rhizobium.

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Alexander Fleming (1881-1955)
Sir Alexander Fleming discovered the antibiotic
penicillin. He had the insight to recognize the
significance of the inhibition of bacterial
growth in the vicinity of a fungal contaminant.
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1.5 Important events in the development of
microbiology

• Date Microbiological History
• 1676 Leeuwenhoek discovers
  "animalcules"
• Pasteur shows that lactic acid
  fermentation is due to a
• microorganism
• Pasteur shows that microorganisms do
  not arise by
• spontaneous generation
• 1867 Lister publishes his work on
  antiseptic surgery
• 1869 Miescher discovers nucleic acids
• 1876-1877 Koch demonstrates that anthrax is
  caused by Bacillus
• anthracis
• Laveran discovers Plasmodium, the
  cause of malaria
• 1881 Koch cultures bacteria on gelatin
• Pasteur develops anthrax
  vaccine

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• 1884 Koch's postulates first published
  Metchnikoff describes
• phagocytosis Gram stain developed
• 1887 Petri dish (plate) developed by Richard
  Petri
• Beijerinck isolates root nodule bacteria
• Beijerinck proves that a virus particle
  causes the tobacco
• mosaic disease
• 1921 Fleming discovers lysozyme
• 1923 First edition of Bergey's Manual
• 1928 Griffith discovers bacterial
  transformation
• 1929 Fleming discovers penicillin
• Ruska develops first transmission electron
  microscope
• 1935 Stanley crystallizes the tobacco mosaic
  virus

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• Avery shows that DNA carries
  information during
• transformation Waksman
  discovers streptomycin
• Watson and Crick propose
  the double helix structure
• for DNA
• 1961-1966 Cohen et al use plasmid vectors to
  clone genes in
• bacteria
• 1980 Development of the scanning
  tunneling microscope
• 1983-1984 The polymerase chain reaction
  developed by Mullis
• 1990 First human gene-therapy testing
  begun
• Discovery of Thiomargarita
  namibiensis, the largest
• known bacterium Escherichia
  coli genome sequenced
• Discovery that Vibrio cholerae has
  two separate
• chromosomes

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REVIEW QUESTIONS
1.How did Pasteur's famous experiment defeat
the theory of spontaneous generation? 2.How
can Koch's postulates prove cause and effect in a
disease? 3.Who was the first person to use
solid culture media in microbiology? What
advantages do solid media offer for the culture
of microorganisms?
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• 4.What is the enrichment culture technique
  and why was it a useful new method in
  microbiology?
• 5.When and how Alexander Fleming
  discovered antibiotics?

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APPLICATION QUESTIONS
1. Pasteur's experiments on spontaneous
generation were of enormous importance for the
advance of microbiology, having an impact on the
methodology of microbiology, ideas on (he origin
of life, and the preservation of food,to name
just a few. Explain briefly how the impact of his
experiments was felt on each of the topics listed.
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2. Describe the various lines of proof Robert
Koch used to definitively associate the bacterium
Mycobacterium tuberculosis with the disease
tuberculosis. How would his proof have been
flawed if any of the tools he developed for
studying bacterial diseases had not been
available for his study of tuberculosis?
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