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9/6/2016
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Presentations prepared by
Mindy Miller-Kittrell,
North Carolina State University
The Early Years of Microbiology
• What Does Life Really Look Like?
• Antoni van Leeuwenhoek
CHAPTER
1
• Began making and using simple microscopes
• Often made a new microscope for each specimen
• Examined water and visualized tiny animals, fungi, algae,
A Brief
History of
Microbiology
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Figure 1.1 Antoni van Leeuwenhoek.
and single-celled protozoa: "animalcules"
• By end of 19th century, these organisms were called
microorganisms; now they are also called microbes
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Figure 1.2 Reproduction of Leeuwenhoek's microscope.
Lens
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Figure 1.3 The microbial world.
Specimen holder
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The Early Years of Microbiology
• How Can Microbes Be Classified?
• Carolus Linnaeus developed taxonomic system for
naming plants and animals and grouping similar
organisms together
• Leeuwenhoek's microorganisms are now grouped into
six categories:
• Bacteria
• Archaea
• Fungi
• Protozoa
• Algae
• Small multicellular animals
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The Early Years of Microbiology
Figure 1.4 Cells of the bacterium Streptococcus (dark blue) and two human cheek cells.
Prokaryotic
bacterial cells
Nucleus of
eukaryotic cheek cell
• How Can Microbes Be Classified?
• Bacteria and Archaea
• Prokaryotic (lack nuclei)
• Much smaller than eukaryotes
• Found everywhere there is sufficient moisture; some have
been isolated from extreme environments
• Reproduce asexually
• Bacterial cell walls contain peptidoglycan; some lack cell
walls
• Archaeal cell walls are composed of polymers other than
peptidoglycan
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The Early Years of Microbiology
Figure 1.5 Fungi.
Hyphae
Spores
Budding cells
• How Can Microbes Be Classified?
• Fungi
• Eukaryotic (have membrane-bound nucleus)
• Obtain food from other organisms
• Possess cell walls
• Include
• Molds – multicellular; grow as long filaments;
reproduce by sexual and asexual spores
• Yeasts – unicellular; reproduce asexually by budding;
some produce sexual spores
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The Early Years of Microbiology
Figure 1.6 Locomotive structures of protozoa.
Nucleus Pseudopods
Cilia
• How Can Microbes Be Classified?
• Protozoa
• Single-celled eukaryotes
• Similar to animals in nutrient needs and cellular structure
• Live freely in water; some live in animal hosts
• Asexual (most) and sexual reproduction
Flagellum
• Most are capable of locomotion by
• Pseudopods – cell extensions that flow in direction of
travel
• Cilia – numerous short protrusions that propel
organisms through environment
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• Flagella – extensions of a cell that are fewer, longer,
and more whiplike than cilia
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Figure 1.7 Algae.
The Early Years of Microbiology
• How Can Microbes Be Classified?
• Algae
• Unicellular or multicellular
• Photosynthetic
• Simple reproductive structures
• Categorized on the basis of pigmentation and composition
of cell wall
• Scientists and manufacturers use many algae-derived
products
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Figure 1.8 An immature stage of a parasitic worm in blood.
The Early Years of Microbiology
Red blood cell
• How Can Microbes Be Classified?
• Other Organisms of Importance to Microbiologists
• Parasites
• Viruses
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Figure 1.9 A colorized electron microscope image of viruses infecting a bacterium.
The Early Years of Microbiology
Virus
• Tell Me Why
Bacterium
• Other Organisms of Importance to Microbiologists
Viruses
assembling
inside cell
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The Golden Age of Microbiology
The Golden Age of Microbiology
• Scientists searched for answers to four questions
• Does Microbial Life Spontaneously Generate?
• Is spontaneous generation of microbial life possible?
• What causes fermentation?
• What causes disease?
• How can we prevent infection and disease?
• Some philosophers and scientists of the past thought
living things arose from three processes:
• Asexual reproduction
• Sexual reproduction
• Nonliving matter
• Aristotle proposed spontaneous generation
• Living things can arise from nonliving matter
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The Golden Age of Microbiology
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Figure 1.10 Redi's experiments.
• Does Microbial Life Spontaneously Generate?
• Redi's experiments
• When decaying meat was kept isolated from flies,
maggots never developed
• Meat exposed to flies was soon infested
• As a result, scientists began to doubt Aristotle's theory
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The Golden Age of Microbiology
The Golden Age of Microbiology
• Does Microbial Life Spontaneously Generate?
• Does Microbial Life Spontaneously Generate?
• Needham's experiments
• Scientists did not believe that animals could arise
• Spallanzani's experiments
• Results contradicted Needham's findings
• Concluded that
spontaneously, but that microbes could
• Needham failed to heat vials sufficiently to kill all
microbes or had not sealed vials tightly enough
• Needham's experiments with beef gravy and infusions of
• Microorganisms exist in air and can contaminate
experiments
plant material reinforced this idea
• Spontaneous generation of microorganisms does not
occur
• The debate continued until the experiments conducted by
Louis Pasteur
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Figure 1.11 Louis Pasteur.
The Golden Age of Microbiology
• Does Microbial Life Spontaneously Generate?
• Pasteur's experiments
• Performed investigations of spontaneous generation
• When the "swan-necked" flasks remained upright, no
microbial growth appeared
• When the flask was tilted, dust from the bend in the neck
seeped back into the flask and made the infusion cloudy
with microbes within a day
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Figure 1.12 Pasteur's experiments with "swan-necked flasks."
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The Golden Age of Microbiology
• Does Microbial Life Spontaneously Generate?
• The scientific method
• Debate over spontaneous generation led in part to
development of scientific method
• Observation leads to question
• Question generates hypothesis
• Hypothesis is tested through experiment(s)
• Results prove or disprove hypothesis
• Accepted hypothesis can lead to theory/law
• Disproved hypothesis is rejected or modified
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Figure 1.13 The scientific method, which forms a framework for scientific research.
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The Golden Age of Microbiology
• What Causes Fermentation?
• Spoiled wine threatened livelihood of vintners
• Some believed air caused fermentation; others insisted
living organisms caused fermentation
• Vintners funded research of methods to promote
production of alcohol and prevent spoilage during
fermentation
• This debate also linked to debate over spontaneous
generation
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Figure 1.14 How Pasteur applied the scientific method in investigating the nature of fermentation.
The Golden Age of Microbiology
• What Causes Fermentation?
• Pasteur's experiments
• Led to the development of pasteurization
• Process of heating liquids just enough to kill most
bacteria
• Began the field of industrial microbiology
• Intentional use of microbes for manufacturing products
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The Golden Age of Microbiology
• What Causes Fermentation?
• Buchner's experiments
• Demonstrated fermentation does not require living cells
• Showed enzymes promote chemical reactions
• Began the field of biochemistry
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The Golden Age of Microbiology
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Figure 1.15 Robert Koch.
• What Causes Disease?
• Pasteur developed germ theory of disease
• Robert Koch studied disease causation (etiology)
• Anthrax
• Examined colonies of microorganisms
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The Golden Age of Microbiology
Figure 1.16 Bacterial colonies on a solid surface (agar).
Bacterium 6
• What Causes Disease?
Bacterium 5
Bacterium 4
• Koch's experiments
Bacterium 7
Bacterium 8
Bacterium 9
Bacterium 3
• Simple staining techniques
Bacterium 2
Bacterium 10
Bacterium 11
Bacterium 1
Bacterium 12
• First photomicrograph of bacteria
• First photomicrograph of bacteria in diseased tissue
• Techniques for estimating CFU/ml
• Use of steam to sterilize media
• Use of Petri dishes
• Techniques to transfer bacteria
• Bacteria as distinct species
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The Golden Age of Microbiology
• What Causes Disease?
• Koch's postulates
• Suspected causative agent must be found in every case
of the disease and be absent from healthy hosts
• Agent must be isolated and grown outside the host
• When agent is introduced into a healthy, susceptible host,
the host must get the disease
• Same agent must be found in the diseased experimental
host
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Figure 1.17 Results of Gram staining.
Gram-positive
Gram-negative
The Golden Age of Microbiology
• How Can We Prevent Infection and Disease?
• Many great advances in disease prevention came after
it was shown that microbes can cause disease
• Modern principles of hygiene not widely practiced in the
mid-1800s
• Healthcare associated infections were common
• Six health care practitioners were instrumental in
changing health care delivery methods
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The Golden Age of Microbiology
The Golden Age of Microbiology
• How Can We Prevent Infection and Disease?
• How Can We Prevent Infection and Disease?
• Semmelweis and handwashing
• Ignaz Semmelweis required medical students to wash
their hands in chlorinated lime water
• Resulted in higher patient survival rates
• Lister's antiseptic technique
• Nightingale and nursing
• Florence Nightingale introduced cleanliness and
antiseptic techniques into nursing practice
• Advocated for hospital and public health policy reform
• Snow and epidemiology
• Joseph Lister advanced antisepsis in health care settings
• John Snow mapped cholera epidemic in London in 1854
• Sprayed wounds, surgical incisions, and dressings with
• His work was the foundation for infection control and
carbolic acid (phenol)
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Figure 1.18 Florence Nightingale.
epidemiology
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The Golden Age of Microbiology
• How Can We Prevent Infection and Disease?
• Jenner's vaccine
• Edward Jenner developed a vaccine against smallpox
• Demonstrated the validity of vaccination
• Began the field of immunology
• Ehrlich's "magic bullets"
• Paul Ehrlich worked to identify "magic bullets" that would
destroy pathogens but not harm humans
• Discoveries began the field of chemotherapy
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Figure 1.19 Some of the many scientific disciplines and applications that arose from the pioneering work of scientists
just before and around the time of the Golden Age of Microbiology.
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The Golden Age of Microbiology
• Tell Me Why
• Some people consider Pasteur or Koch to be the Father
of Microbiology, rather than Leeuwenhoek. Why might
they be correct?
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The Modern Age of Microbiology
The Modern Age of Microbiology
• What Are the Basic Chemical Reactions of Life?
• What Are the Basic Chemical Reactions of Life?
• Biochemistry
• Study of metabolism: the chemical reactions that occur in
• Biochemistry
• Practical applications
living organisms
• Design of herbicides and pesticides
• Began with Pasteur's work on fermentation and Buchner's
• Diagnosis of illnesses and monitoring of patients'
discovery of enzymes in yeast extract
responses to treatment
• Kluyver and van Niel proposed basic biochemical reactions
• Treatment of metabolic diseases
shared by all living things
• Drug design
• Microbes used as model systems for biochemical reactions
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The Modern Age of Microbiology
The Modern Age of Microbiology
• How Do Genes Work?
• How Do Genes Work?
• Genetics: scientific study of inheritance
• Many advances in the discipline made through the study
of microbes
• Microbial genetics
• Avery, MacLeod, and McCarty determined that genes are
contained in molecules of DNA
• Beadle and Tatum established that a gene's activity is
related to protein function
• Explained translation of genetic information into protein
• Investigated rates and mechanisms of genetic mutation
• Determined how cells control genetic expression
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The Modern Age of Microbiology
The Modern Age of Microbiology
• How Do Genes Work?
• How Do Genes Work?
• Molecular biology
• Explanation of cell function at the molecular level
• Pauling proposed that gene sequences could
• Provide understanding of evolutionary relationships
and processes
• Establish taxonomic categories to reflect these
relationships
• Identify existence of microbes that have never been
cultured
• Woese determined that cells belong to domains Bacteria,
Archaea, or Eukarya
• Cat scratch disease caused by unculturable organism
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• Recombinant DNA technology
• Genes in microbes, plants, and animals manipulated for
practical applications
• Production of human blood-clotting factor by E. coli to aid
hemophiliacs
• Gene therapy
• Inserting a missing gene or repairing a defective one in
humans by inserting desired gene into host cells
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The Modern Age of Microbiology
The Modern Age of Microbiology
• What Role Do Microorganisms Play in the
• How Do We Defend Against Disease?
• Serology
Environment?
• Bioremediation uses living bacteria, fungi, and algae to
detoxify polluted environments
• The study of blood serum
• Von Behring and Kitasato – presence in the blood of
chemicals and cells that fight infection
• Recycling of chemicals such as carbon, nitrogen, and
• Immunology
• The study of the body's defenses against specific
sulfur
• Most microbes in the environment are not pathogenic
pathogens
• Chemotherapy
• Fleming discovered penicillin
• Domagk discovered sulfa drugs
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Figure 1.20 The effects of penicillin on a bacterial "lawn" in a Petri dish.
The Modern Age of Microbiology
Fungus colony
(Penicillium)
Zone of inhibition
Bacteria
(Staphylococcus)
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• What Will the Future Hold?
• Microbiology is built on asking and answering questions
• The more questions we answer, the more questions we
have
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The Modern Age of Microbiology
• Tell Me Why
• Why are so many modern questions in microbiology
related to genetics?
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