11949247.ppt

© 2012 Pearson Education Inc.
Lecture prepared by Mindy Miller-Kittrell
North Carolina State University
Chapter 1
A Brief
History of
Microbiology

“We used to see from the elephant down
to the mite; thenceforth we had a world
populated with tiny animalcules to whom
the mite was elephant.”
-F. Gonzales-Crussi

The Early Years of Microbiology
• What Does Life Really Look Like?
– Antoni van Leeuwenhoek (Dutch, late 1600s)
– 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

Figure 1.1 Antoni van Leeuwenhoek

Figure 1.2 Reproduction of Leeuwenhoek’s microscope
Specimen holder
Lens

• How Can Microbes Be Classified?
– Carolus Linnaeus developed taxonomic system
for grouping similar organisms together
– Leeuwenhoek’s microorganisms grouped into six
categories:
– Bacteria
– Archaea
– Fungi
– Protozoa
– Algae
– Small multicellular animals

Classification
• 3 Domains:
– Domain Bacteria
– Domain Archaea
– Domain Eukarya
– 4 Kingdoms
– Kingdom Animalia
– Kingdom Plantae
– Kingdom Fungi
– Kingdom Protista

• Bacteria and Archaea
– Unicellular and lack nuclei
– Much smaller than eukaryotes
– Found everywhere there is sufficient moisture
– Reproduce asexually
– Two kinds
– Bacteria – cell walls contain peptidoglycan
– Archaea – cell walls composed of polymers
other than peptidoglycan

Figure 1.4 Cells of the bacterium Streptococcus
Nucleus of
eukaryotic cheek cell
Prokaryotic
bacterial 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 by budding or
sexual spores

• Protozoa
– Single-celled eukaryotes in kingdom Protista.
– 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
– Pseudopodia
– Cilia
– Flagella

Figure 1.6 Locomotive structures of protozoa-overview

• Algae
– Unicellular or multicellular
– Photosynthetic
– Simple reproductive structures
– Categorized on the basis of pigmentation,
storage products, and composition of cell wall

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

Figure 1.9 Viruses infecting a bacterium
Virus
Bacterium
Viruses
assembling
inside cell

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?

• Some 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
Flask unsealed Flask sealed Flask covered
with gauze

• Needham’s Experiments
– Scientists now thought microbes, but not
animals, could arise spontaneously
– Needham’s experiments reinforced this idea
– He boiled flasks of gravy and corked them.
Microorganisms were later found to be in the
gravy, demonstrating spontaneous
generation.

• Spallanzani’s (1729-1799) Experiments
– Conclusions
– Needham failed to heat vials sufficiently to kill all
microbes and had not sealed vials tightly enough
– Microorganisms exist in air and can contaminate
experiments
– Spontaneous generation does not occur
– Critics argued against Spallanzani’s experiments
– Sealed vials did not allow enough air for organisms to
survive
– Prolonged heating destroyed “life force”

• Pasteur’s (1822-1895) Experiments
– 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
Steam escapes
from open end
of flask.
Infusion
is heated.
Infusion sits;
no microbes appear.
Months
Air moves in
and out of flask.
Infusion remains
sterile indefinitely.
Dust from
air settles
in bend.

• The Scientific Method
– Spontaneous generation debate led in part to
scientific method
– Observation leads to question
– Question generates hypothesis
– Hypothesis is tested through experiment(s)
– Results prove or disprove hypothesis
– Accepted hypothesis leads to theory/law
– Reject or modify hypothesis

Figure 1.13 The scientific method
Observations
Question
Hypothesis
Repeat
Experiment,
including
control groups
Modified
hypothesis
Observations
Experimental
data support
hypothesis
Experimental
data do not
support
hypothesis
Accept
hypothesis
Reject
hypothesis
Modify
hypothesis
Theory
or law

• What Causes Fermentation?
– Spoiled wine threatened livelihood of vintners
– Some believed air caused fermentation
– Others insisted living organisms caused
fermentation
– Vintners funded research to prevent spoilage
during fermentation
– This debate also linked to debate over
spontaneous generation

Figure 1.14 Pasteur's application of the scientific method
Observation:
Hypothesis Experiment Observation Conclusion
Fermenting
grape juice
Microscopic analysis
shows juice contains
yeasts and bacteria.
Day 1: Flasks of grape
juice are heated sufficiently
to kill all microbes.
Day 2
I. Spontaneous
fermentation
occurs.
II. Air ferments
grape juice.
III. Bacteria ferment
grape juice
into alcohol.
IV. Yeasts ferment
grape juice
into alcohol.
Juice in flask is
inoculated with
yeast and sealed.
Juice in flask is
inoculated with
bacteria and sealed.
Flask remains
open to air
via curved neck.
Flask is
sealed.
No fermentation;
juice remains
free of microbes
No fermentation;
juice remains
free of microbes
Bacteria reproduce;
acids are produced.
Yeasts reproduce;
alcohol is produced.
Reject
hypothesis I.
Reject
hypothesis II.
Modify hypothesis
III; bacteria ferment
grape juice into
acids.
Accept hypothesis
IV; yeasts ferment
grape juice into
alcohol.

Table 1.1 Some Industrial Uses of Microbes

• What Causes Disease?
– Pasteur developed germ theory of disease
– Robert Koch (1843-1910) studied causative
agents of disease
– Anthrax
– Also determined that anthrax can form
endospores that allow them to survive
harsh conditions.
– Examined colonies of microorganisms
growing on potatoes—pure cultures.
– Discovered the causative agent of
tuberculosis.

Figure 1.16 Bacterial colonies on agar
Bacterium 1
Bacterium 2
Bacterium 3
Bacterium 4
Bacterium 5
Bacterium 6 Bacterium 7
Bacterium 8
Bacterium 9
Bacterium 10
Bacterium 11
Bacterium 12

• 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

• How Can We Prevent Infection and
Disease?
– Semmelweis and handwashing
– Ignaz Semmelweis required medical students
to wash their hands between procedures,
greatly reducing the incidence of women
contracting puerperal fever during childbirth.
– Lister’s antiseptic technique
– First to use antiseptics during surgery.

How Can We Prevent Infection and Disease?
– Nightingale and nursing
– Florence Nightingale was a nurse who
emphasized cleanliness in hospitals.
– Snow – infection control and epidemiology
– Jenner’s vaccine – field of immunology
– Edward Jenner developed the first vaccine. It
was for smallpox

John Snow (1813-1858)
and cholera
• John Snow is considered the
father of epidemiology.
• He went door to door in
London and realized that
people who were contracting
cholera were getting their
water from a contaminated
source and he eventually
convinced city officials to
remove the handle from the
pump, which helped end the
cholera epidemic.

Two competing theories
Miasma Theory
• Most people and
scientists held to this.
• Disease is caused by
“bad air.”
Germ Theory
• Took a while to be
accepted.

Vibrio cholerae
• Causative agent
was isolated by
Robert Koch in
1883.
• He actually wasn’t
the first to isolate it,
but he received
credit for it.

Paul Ehrlich
• “We must learn to
shoot microbes with
magic bullets.”
• Developed the first
chemotherapeutic
agent.
• It was called
salvarsan and was
used to treat
syphilis.

Paul Ehrlich
• Ehrlich began his
work studying
various dyes.
• He was pals with
Robert Koch and
showed Koch how
to stain the bacteria
that causes
tuberculosis.

The Modern Age of Microbiology
• The “Golden Age of Microbiology” yielded
many important discoveries and opened
several new fields such as immunology,
epidemiology, chemotherapy, and genetic
engineering.
• Scientists had a grand hope that they would
be able to eliminate microbial disease.
• This has proven more difficult than previously
thought.
• Why?

• How Do Genes Work?
– Microbial genetics
– Molecular biology
– Recombinant DNA technology

• How Do We Defend Against Disease?
–Immunology
– The study of the body’s defense against specific
pathogens
–Chemotherapy
– Alexander Fleming discovered penicillin

Figure 1.20 Effects of penicillin on a bacterial “lawn” in a petri dish
Fungus colony
(Penicillium)
Zone of inhibition
Bacterial colonies
(Staphylococcus)

• 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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