Chapter 1.pdf

© 2015 Pearson Education, Inc.
Chapter 1

The Early Years of Microbiology
• What Does Life Really Look Like?
• Antoni van Leeuwenhoek
• Began making and using simple microscopes
• Often made a new microscope for each specimen
• Examined water and visualized tiny animals, fungi, algae,
and single-celled protozoa: "animalcules"
• By end of 19th century, these organisms were called
microorganisms; now they are also called microbes

Figure 1.1 Antoni van Leeuwenhoek.

Lens Specimen holder
Figure 1.2 Reproduction of Leeuwenhoek's microscope.

Figure 1.3 The microbial world.

• 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

• 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

Prokaryotic
bacterial cells
Nucleus of
eukaryotic cheek cell
Figure 1.4 Cells of the bacterium Streptococcus (dark blue) and two human cheek cells.

• 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

Spores
Hyphae Budding cells
Figure 1.5 Fungi.

• 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
• Most are capable of locomotion by
• Pseudopods – cell extensions that flow in direction of
travel
• Cilia – numerous short protrusions that propel
organisms through environment
• Flagella – extensions of a cell that are fewer, longer,
and more whiplike than cilia

Pseudopods
Nucleus Cilia
Flagellum
Figure 1.6 Locomotive structures of protozoa.

• 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

Figure 1.7 Algae.

• Other Organisms of Importance to Microbiologists
• Parasites
• Viruses

Red blood cell
Figure 1.8 An immature stage of a parasitic worm in blood.

Virus
Bacterium
Viruses
assembling
inside cell
Figure 1.9 A colorized electron microscope image of viruses infecting a bacterium.

• Tell Me Why
• Other Organisms of Importance to Microbiologists

The Golden Age of Microbiology
• Scientists searched for answers to four questions
• Is spontaneous generation of microbial life possible?
• What causes fermentation?
• What causes disease?
• How can we prevent infection and disease?

• Does Microbial Life Spontaneously Generate?
• 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

• 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

Figure 1.10 Redi's experiments.

• Needham's experiments
• Scientists did not believe that animals could arise
spontaneously, but that microbes could
• Needham's experiments with beef gravy and infusions of
plant material reinforced this idea

• Spallanzani's experiments
• Results contradicted Needham's findings
• Concluded that
• Needham failed to heat vials sufficiently to kill all
microbes or had not sealed vials tightly enough
• Microorganisms exist in air and can contaminate
experiments
• Spontaneous generation of microorganisms does not
occur
• The debate continued until the experiments conducted by
Louis Pasteur

Figure 1.11 Louis Pasteur.

• 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

Figure 1.12 Pasteur's experiments with "swan-necked flasks."

• 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

Figure 1.13 The scientific method, which forms a framework for scientific research.

• 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

Figure 1.14 How Pasteur applied the scientific method in investigating the nature of 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

• Buchner's experiments
• Demonstrated fermentation does not require living cells
• Showed enzymes promote chemical reactions
• Began the field of biochemistry

• What Causes Disease?
• Pasteur developed germ theory of disease
• Robert Koch studied disease causation (etiology)
• Anthrax
• Examined colonies of microorganisms

Figure 1.15 Robert Koch.

• Koch's experiments
• Simple staining techniques
• 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

Bacterium 1
Bacterium 2
Bacterium 3
Bacterium 4
Bacterium 5
Bacterium 6 Bacterium 7
Bacterium 8
Bacterium 9
Bacterium 10
Bacterium 11
Bacterium 12
Figure 1.16 Bacterial colonies on a solid surface (agar).

• 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

Gram-positive Gram-negative
Figure 1.17 Results of Gram staining.

• 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

• 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
• Joseph Lister advanced antisepsis in health care settings
• Sprayed wounds, surgical incisions, and dressings with
carbolic acid (phenol)

• Nightingale and nursing
• Florence Nightingale introduced cleanliness and
antiseptic techniques into nursing practice
• Advocated for hospital and public health policy reform
• Snow and epidemiology
• John Snow mapped cholera epidemic in London in 1854
• His work was the foundation for infection control and
epidemiology

Figure 1.18 Florence Nightingale.

• 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

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.

• Tell Me Why
• Some people consider Pasteur or Koch to be the Father
of Microbiology, rather than Leeuwenhoek. Why might
they be correct?

The Modern Age of Microbiology
• What Are the Basic Chemical Reactions of Life?
• Biochemistry
• Study of metabolism: the chemical reactions that occur in
living organisms
• Began with Pasteur's work on fermentation and Buchner's
discovery of enzymes in yeast extract
• Kluyver and van Niel proposed basic biochemical reactions
shared by all living things
• Microbes used as model systems for biochemical reactions

• What Are the Basic Chemical Reactions of Life?
• Biochemistry
• Practical applications
• Design of herbicides and pesticides
• Diagnosis of illnesses and monitoring of patients'
responses to treatment
• Treatment of metabolic diseases
• Drug design

• 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

• 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

• 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

• What Role Do Microorganisms Play in the
Environment?
• Bioremediation uses living bacteria, fungi, and algae to
detoxify polluted environments
• Recycling of chemicals such as carbon, nitrogen, and
sulfur
• Most microbes in the environment are not pathogenic

• How Do We Defend Against Disease?
• Serology
• The study of blood serum
• Von Behring and Kitasato – presence in the blood of
chemicals and cells that fight infection
• Immunology
• The study of the body's defenses against specific
pathogens
• Chemotherapy
• Fleming discovered penicillin
• Domagk discovered sulfa drugs

Fungus colony
(Penicillium)
Zone of inhibition
Bacteria
(Staphylococcus)
Figure 1.20 The effects of penicillin on a bacterial "lawn" in a Petri dish.

• What Will the Future Hold?
• Microbiology is built on asking and answering questions
• The more questions we answer, the more questions we
have

• Tell Me Why
• Why are so many modern questions in microbiology
related to genetics?

Important topics
 Antoni van Leeuwenhoek’s and Semmelweis findings
 The general characteristics of bacteria, archaea, virus,
protozoa, fungus, algae
 To differentiate the prokaryotes and eukaryotes
 Enzyme, a protein that runs the chemical reactions in the
cell.

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