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Chapter 1
The History and Scope of
Microbiology
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The Importance of
Microorganisms
• most populous group of organisms and
are found everywhere on the planet
• play a major role in recycling essential
elements
• source of nutrients and some carry out
photosynthesis
• benefit society by their production of
food, beverages, antibiotics and vitamins
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What is microbiology?
• study of organisms too small to be
clearly seen by the unaided eye (i.e.,
microorganisms)
• these organisms are relatively simple
in their construction and lack highly
differentiated cells and distinct
tissues
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Members of the microbial world
• procaryotic cells lack a true
membrane-delimited nucleus
• eucaryotic cells have a membraneenclosed nucleus, are more complex
morphologically and are usually
larger than procaryotic cells
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Classification schemes
• five kingdom scheme includes Monera,
Protista, Fungi, Animalia and Plantae with
microbes placed in the first three kingdoms
• three domain alternative, based on a
comparison of ribosomal RNA, divides
microorganisms into Bacteria (true
bacteria), Archaea and Eucarya (eucaryotes)
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Figure 1.1
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Domain Bacteria –
all procaryotic
•
•
•
•
most are single-celled
most have peptidoglycan in cell wall
can survive broad range of environments
most are non-pathogenic and play major
role in nutrient recycling
• cyanobacteria produce oxygen as a result
of photosynthesis
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Domain Archaea –
all procaryotic
• procaryotic
• distinguished from Bacteria by
unique ribosomal RNA sequences
• lack peptidoglycan in cell wall
• many found in extreme
environments
• no pathogenic species known
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Domain Eucarya –
all eucaryotic
• animals, plants and eucaryotic
microorganisms
– Microorganisms include protists
(unicellular algae, protozoa, slime
molds and water molds) and fungi
– Most are larger than procaryotic cells
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Viruses
• acellular
• smallest of all microbes
• cause a range of diseases including
some cancers (e.g. hepatitis B & C)
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Figure 1.2a
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Figure 1.2b
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Figure 1.2c
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Discovery of Microorganisms
• Antony van
Leeuwenhoek (16321723)
– first person to
observe and describe
microorganisms
accurately
Figure 1.3 (a)
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Figure 1.3 (b) and (c)
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The Conflict over
Spontaneous Generation
• spontaneous generation
– living organisms can develop from
nonliving or decomposing matter
• Francesco Redi (1626-1697)
– disproved spontaneous generation for
large animals
– showed that maggots on decaying meat
came from fly eggs
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But could spontaneous generation
be true for microorganisms?
• John Needham (1713-1781)
– his experiment:
mutton broth in flasks  boiled sealed
– results: broth became cloudy and contained
microorganisms
• Lazzaro Spallanzani (1729-1799)
– his experiment:
water and seeds in flasks  sealed  placed in boiling water
for 45 min
– results: no growth of microorganisms
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Louis Pasteur (1822-1895)
• his experiments
– filtered air through cotton
: found objects resembling plant spores
– placed nutrient solution in flasks
– created flasks with long, curved necks
– boiled the solutions
– left flasks exposed to air
• results: no growth of microorganisms
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Louis Pasteur (1822-1895)
Figure 1.4
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Figure 1.5
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Final blow to theory of
spontaneous generation
• John Tyndall (1820-1893)
– demonstrated that dust carries germs
(microorganisms)
– showed that if dust was absent, nutrient
broths remained sterile, even if directly
exposed to air
– also provided evidence for the existence of
exceptionally heat-resistant forms of
bacteria (endospore)
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The role of microorganisms
in disease
• was not immediately obvious
• establishing connection depended on
development of techniques for
studying microbes
• once established, led to study of host
defenses - immunology
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The golden age of
microbiology (1857-1914)
• Many disease producing organisms
discovered
• Microbial metabolism studies undertaken
• Microbiological techniques refined
• A better understanding of the role of
immunity and ways to control and
prevent infection by microbes
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Recognition of the
relationship between
microorganisms and disease
• Agostini Bassi (1773-1856)
– showed that a disease of silkworms was
caused by a fungus
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More evidences…
• M. J. Berkeley (ca. 1845)
– demonstrated that the great Potato Blight of
Ireland was caused by a water mold
• Heinrich de Bary (1853)
– showed that smut and rust fungi caused cereal
crop diseases
• Louis Pasteur
– showed that the pébrine disease of silkworms was
caused by a protozoan
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Other evidences…
• Joseph Lister
– provided indirect evidence that
microorganisms were the causal agents of
disease
– developed a system of surgery designed to
prevent microorganisms from entering
wounds as well as methods for treating
instruments and surgical dressings
– his patients had fewer postoperative
infections
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Final proof…
• Robert Koch (1843-1910)
– established the relationship between Bacillus
anthracis and anthrax
– used criteria developed by his teacher Jacob
Henle (1809-1895)
– these criteria now known as Koch’s postulates
• still used today to establish the link between a
particular microorganism and a particular disease
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Koch’s postulates
• The microorganism must be present in every
case of the disease but absent from healthy
individuals.
• 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
again from the diseased host.
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Figure 1.6
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The development of
techniques for studying
microbial pathogens
• Koch’s work led to discovery or
development of:
– agar
– petri dish
– nutrient broth and nutrient agar
– methods for isolating microorganisms
(streak plate method)
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Other developments…
• Charles Chamberland (1851-1908)
– developed porcelain bacterial filters used by
Ivanoski and Beijerinck to study tobacco
mosaic disease
• determined that extracts from diseased plants
had infectious agents present which were smaller
than bacteria and passed through the filters
• Infectious agents were eventually shown to be
viruses
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Immunological Studies
• Edward Jenner (ca. 1798)
– used a vaccination procedure to protect
individuals from smallpox
* This work preceded the work establishing
the role of microorganisms in disease
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Other developments…
• Pasteur and Roux
– discovered that incubation of cultures
for long intervals between transfers
caused pathogens to lose their ability to
cause disease
• Pasteur and his coworkers
– developed vaccines for chicken cholera,
anthrax, and rabies
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More developments…
• Emil von Behring (1854-1917) and
Shibasaburo Kitasato (1852-1931)
– developed antitoxins for diphtheria and
tetanus
– evidence for humoral immunity
• Elie Metchnikoff (1845-1916)
– discovered bacteria-engulfing phagocytic
cells in the blood
– evidence for cellular immunity
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The Development of
Industrial Microbiology and
Microbial Ecology
• Louis Pasteur
– demonstrated that alcohol
fermentations and other fermentations
were the result of microbial activity
– developed the process of pasteurization
to preserve wine during storage
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Additional Developments…
• Sergei Winogradsky (1856-1953) and
Martinus Beijerinck (1851-1931)
– studied soil microorganisms and discovered
numerous interesting metabolic processes
(e.g., nitrogen fixation, chemolithotrophy)
– pioneered the use of enrichment cultures and
selective media
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The Scope and Relevance
of Microbiology
• importance of microorganisms
– first living organisms on planet
– live everywhere life is possible
– more numerous than any other kind of
organisms
– global ecosystem depends on their activities
– influence human society in many ways
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Microbiology has
basic and applied aspects
• Basic aspects are concerned with
individual groups of microbes,
microbial physiology, genetics,
molecular biology and taxonomy
• Applied aspects are concerned with
practical problems – disease, water,
food and industrial microbiology
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Microbiology actually represents
many fields of study
• Examples
– medical microbiology is concerned
with diseases of humans and animals
– immunology is concerned with how the
immune system protects a host from
pathogens
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More fields…
– microbial ecology is concerned with the
relationship of organisms with their
environment
– microbial genetics and molecular
biology are concerned with the
understanding of how genetic
information functions and regulates
the development of cells and organisms
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The Future of Microbiology:
Challenges and opportunities for
future microbiologists
• infectious disease
• new and improved industrial processes
• microbial diversity and microbial ecology
– less than 1% of earth’s microbial population
has been cultured
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More challenges and
opportunities…
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•
•
•
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biofilms
genome analysis
microbes as model systems
assessment of implications of new
discoveries and technologies