Chapter 1
Microorganisms and Microbiology
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
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
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.
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.
Microbial world
Organisms
Infectious agents
(non-living)
(living)
Prokaryotes
(unicellular)
Eubacteria
Archaea
eukaryotes
Algae
(unicellular
or
multicellular
)
viruses
viroids
Fungi
Protozoa
(unicellular
(unicellular
or
)
multicellular)
prions
Other
(multicellular
organisms)
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.
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->1m
Eukaryote
Protozoa
2-1000µm
Eukaryote
Algae
1µm-several meters
Eukaryote
1.2 The importance of microbiology
Microbes impinge on all aspects of life, just a few
of these are listed below:
The environment
Biotechnology
Medicine
Research
Food
• The environment
• Medicine
• Food
• Biotechnology
• Research
Press here to continue
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.
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.
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.
Traditionally microbes have been used to
synthesize important chemicals. The
advent of genetic engineering techniques
has led to the cloning of polypeptides into
microbes.
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.
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
Microbial physiology
Microbial genetics
Microbial Morphology
Virology
Parasitology
Branches of
Microbiology
Mycology
Protozoology
Bacteriology
Microbial ecology
Microbial taxonomy
Molecular biology
Phycology or Algology
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.
1.4 The history of microbiology
In the field of observation, chance favors
only prepared minds.
------ Louis Pasteur
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
The discovery of microorganisms
Antony van Leeuwenhock
(1632-1723)
The first person to
accurately observe and
describe microorganisms
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 16731723, 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.
lens
Object
being
viewed
adjusting
screws
A drawing of one
of the microscopes
showing the lens a;
mounting pin b;
and focusing
screws c and d.
Leeuwenhoek’s
drawings of
bacteria from the
human mouth.
Louis Pasteur (1822 – 1895)
Pasteur’s contributions:
• Pasteur (1857) demonstrated
that lactic acid fermentation is
due to the activity of microorganisms
• Pasteur (1861) conflict over
spontaneous generation – birth
of microbiology as a science
• Pasteur (1881) developed
anthrax vaccine
Louis Pasteur working in his
laboratory
• Pasteurization
The spontaneous generation conflict
Spontaneous generation – that living
organisms could develop from nonliving
or decomposing matter.
Pasteur’s swan neck flasks used in his experiments
on the spontaneous generation of microorganisms
Conclusion:
Microorganisms are not spontaneously
generated from inanimate matter, but
are produced by other microorganisms
Robert Koch (1843 – 1910)
The recognition of microbial role in disease
Robert Koch in his laboratory
Koch’s demonstration of special organisms
cause special diseases
Koch’s 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
The Golden age of microbiology
• Koch and pure cultures
• Fermentation and Pasteurization
• Germ theory of disease
• Vaccination
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 nitrogen–fixing
bacteria.
• Beijerinck made fundamental
contributions to microbial
ecology. He isolated Azotobacter
and Rhizobium.
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.
1.5 Important events in the development
of microbiology
Date
1676
1857
Microbiological History
Leeuwenhoek discovers "animalcules"
Pasteur shows that lactic acid fermentation is due to a
microorganism
1861
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
1880
Laveran discovers Plasmodium, the cause of malaria
1881
Koch cultures bacteria on gelatin
Pasteur develops anthrax vaccine
1884
1887
1889
1899
1921
1923
1928
1929
1933
1935
Koch's postulates first published Metchnikoff describes
phagocytosis Gram stain developed
Petri dish (plate) developed by Richard Petri
Beijerinck isolates root nodule bacteria
Beijerinck proves that a virus particle causes the tobacco
mosaic disease
Fleming discovers lysozyme
First edition of Bergey's Manual
Griffith discovers bacterial transformation
Fleming discovers penicillin
Ruska develops first transmission electron microscope
Stanley crystallizes the tobacco mosaic virus
1944
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
1997
Discovery of Thiomargarita namibiensis, the largest
known bacterium Escherichia coli genome sequenced
2000
Discovery that Vibrio cholerae has two separate
chromosomes
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?
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?
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.
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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赵斌 何绍江. 2002 微生物学实验。科学出版社。
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