Transcript unit i notes

Unit 1
The Development of Microbiology
Do Now
• What was the last illness you had?
• How sick did you feel?
• Do you know if it was caused by a
microorganism? Which one?
The Beginnings
• Robert Hooke 1665:
• Introduced the world to small objects and
creatures when he published his journal –
Micrographie
• It contained illustrations of
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Eye of a fly
Stinger of a bee
Shell of a protozoan
Plant-like mold
Cork cells
The Beginnings
•Zacharias Janssen:
•Spectacle maker from the
Netherlands
•Invented the microscope
The Beginnings
• Anton van Leeuwenhoek 1670’s
• Seller of silk, wool, and cotton in the
Netherlands
• Enhanced Jansenn’s microscope for use in his
business
• But his fascination with the microscope led
him to examine hair fibers, blood cells and
even his own feces
The Beginnings
• Anton van Leeuwenhoek (continued)
• Looked at marshy lake water which teemed with
microorganisms – he called them animalcules
• He contacted the Royal Society of London and
sent them letters and drawings of his studies
• But, he was very suspicious and didn’t let any
one know how to make his lenses
• He also never made the connection between
microorganisms and disease
The Transition Period
• Biology of the 1700’s consisted of observations of plant
and animal life and attempts to classify them (Linnaeus)
• Scientists did not think of infection in terms of tiny
living organisms
• Believed that an infectious disease spread by a miasma an altered chemical quality of the atmosphere which
arose from diseased bodies - miasmas
• This miasma theory was believed well into the 1800’s
and gradually dissipated with the realization that
microorganisms caused infectious disease
Spontaneous
Generation
• In the 1700’s many scientists believed that
life comes from non-living things
• Living conditions - Why does meat get
maggots?
• They come from the meat!
• Francesco Redi did not agree with this
Spontaneous
Generation
• REDI’S EXPERIMENT 1668
John Needham 1748
• Needham agreed with spontaneous generation
• He boiled bottles of broth (gravy) and said
heating would kill any organisms already in it
• He then capped the bottles of broth – no air
could enter
• After several days, the bottles were
contaminated with microorganisms
• He concluded that they arose from the broth
and spontaneous generation does occur
LAZZARO
SPALLAZANI b. 1729
• He knew about Redi and Needham’s
experiments and he thought Needham was
wrong
• So, Spallanzani did not believe in
spontaneous generation
• What mistake do you think he thought
Needham had made in his experiment?
LAZZARO
SPALLAZANI b. 1729
• He thought Needham hadn’t boiled the broth
enough
• He decided to run his own version of the
experiment
• He thoroughly boiled the broth and stored
some in an open container and some in a closed
container
• After several days he saw……
• No microorganisms in the sealed bottle, and
tons in the unsealed bottle
Spallanzani’s
Experiment
LAZZARO
SPALLAZANI b. 1729
• Microorganisms do not come from broth –
non-life
• They come from the air!
• If this were not so then both jars would have
organisms
• But many still believed in Spontaneous
Generation – they said that it required
oxygen and Spallanzani had blocked it out
Disease Transmission
• People still believed the Miasma Theory of
infection because then people were not at fault
for spreading disease
• In 1847 Ignaz Semmelweis, a Hungarian doctor,
reported that the agent of blood poisoning was
transmitted to maternity patients by doctors
that had just performed autopsies
• He said that hand washing in chlorine water
would stop the spread of disease – no one
listened
Disease Transmission
• John Snow, a British doctor traced the source of
an 1854 cholera epidemic to London’s
municipal water supply
• He said that if people avoided the water, they
would avoid the disease
• People listened and the spread of the disease
was stopped
• These 2 doctors showed that disease was
caused by an unseen object in the environment
– not a miasma.
Do Now
• 1. Briefly describe Francesco Redi’s
experiment. What was he trying to
disprove?
• 2. Did John Needham agree with Redi?
• 3. Briefly describe Lazzaro Spallanzani’s
experiment. What was his conclusion?
The Golden Age
• The science of microbiology blossomed for
about 60 years, beginning in 1857
• It began with a scientist named Louis
Pasteur and ended about the time of WWI
• Numerous branches of microbiology were
established and the foundations for modern
microbiology were laid down
Louis Pasteur’s World
• In the 1800’s, the world was ravaged by
plague, tuberculosis, typhoid fever, and
diphtheria.
• It was necessary to have a large family to
ensure the next generation
• Even royalty could not avoid disease
• No one was sure what caused disease – no
cures
Louis Pasteur Fermentation
• Believed that scientific discoveries should have
practical applications
• He wanted to find out why local wines were
turning sour
• At the time people thought that wine
fermentation resulted from the chemical
breakdown of grape juice into wine.
• They didn’t know any living creatures were
involved
Louis Pasteur –
Fermentation
• But Pasteur’s microscope revealed large
numbers of tiny yeast cells
• He correctly believed that the yeasts played
a major role in fermentation
• In an experiment he removed all yeast from
grape juice and it did not ferment
• Then he added the yeast back and it did
ferment into wine
• He suggested that grape juice be heated to
destroy all life before fermentation was
begun - pasteurization
Louis Pasteur - Bacteria
• Pasteur also noticed that the sour wines
contained tiny sticks and rods known as
bacteria
• He did an experiment where he removed all
bacteria from grape juice
• The when he mixed it with yeast it could
ferment and not turn sour
Louis Pasteur – Germ
Theory
• Pasteur’s discoveries shook the scientific
community
• He demonstrated that yeast cells and bacteria
were tiny living factories where important
chemical changes were occurring
• He also showed microorganisms could be
agents of change – they could cause a disease
rather than being an effect of the disease
• Germ Theory of Disease – microorganisms are
responsible for infectious diseases
LOUIS PASTEUR
•People still believed in spontaneous generation!
•Pasteur decided to end the debate once and for all with
an ingenious experiment
LOUIS PASTEUR
Pasteur’s Conclusion
• He said that life comes from LIFE!
• This is called Bio-genesis
• Pasteur’s work brought to an end the debate
of spontaneous generation
• Now scientists had to concentrate on
connecting certain microorganisms to
specific diseases
Robert Koch
• Koch was a country doctor from East Prussia
(now Germany) who was concerned with
anthrax which infected cattle and sheep
• In a lab in his home, he injected mice with the
blood of diseased cattle, then performed
autopsies on the dead mice
• Next he isolated a few bacteria from a mouse’s
blood and placed it in the sterile aqueous
humor from an ox’s eye
Robert Koch
• He watched as the bacteria multiplied and
then turned into resistant spores
• Next he took several of the spores and
injected them into healthy mice
• The symptoms of anthrax appeared within
hours
• Koch autopsied the mice and found their
blood swarming with bacteria
Robert Koch
Robert Koch’s
Postulates
Solid Culture Media
• Koch developed a solid culture media on which
bacteria would grow by solidifying beef broth
and gelatin
• When inoculated onto the surface, bacteria
grew vigorously and produced discrete visible,
colonies
• Now agar is used instead of gelatin because it
can resist digestion by certain bacteria and it
remains solid when incubated at high
temperatures
End of the Golden Age
• The Golden Age witnessed a series of discoveries
unparalleled in the identification of the agents of
disease
• Scientists developed an awareness that infectious
disease was caused by microorganisms and that the
chains of transmission could be broken
• These discoveries led to calls for sterile practices in
hospitals, pasteurization of milk, purification of
water, control of insects and care in the preparation
of foods
• This led to a substantial reduction in the incidence
of bacterial diseases – but viruses were still to come!
Compound Light
Microscope
Light Path
Light Path
Oil Immersion
Wheat Rust
• A disease of wheat caused by a fungus of the
genus Puccinia
• Infections can lead up to 20% yield loss exacerbated by dying leaves which fertilize the
fungus
• Small brown pustules develop on the leaf
blades in a random scatter distribution. They
may group into patches in serious cases.
Infectious spores are transmitted via the soil.