2. Spontaneous Generation
• Spontaneous Generation is the Theory that
life come from inanimate objects or non-
living things.
• The Theory of Spontaneous Generation was
disproved and Microbiology was founded
by some amazing scientists. Let’s briefly
review some of these scientists.
3. • In 1668-Redi devised an experiment to
disprove the Theory of Spontaneous
Generation
– He put some meat inside jars and covered them.
No maggots grew.
– Antagonists claimed life needed fresh air to
grow so the experiment was invalid.
– Redi repeated the experiment but used gauze to
cover the jars allowing fresh air in, but keeping
flies out. No maggots grew.
4. • Antony Leeuwenhoek: owned dry-good
store (Holland 1632)
– Heard about grinding lenses out of glass to
make things look larger
• Visited spectacle makers to learn how to grind
lenses
• Visited alchemists and apothecaries to learn how to
get metal from ore
• Visited gold- and silversmiths to learn their trade
• Put it together to make a microscope
5. Animalcules
• Leeuwenhoek discovered living cells while
looking under his microscope.
• He called the living cells, “Animalcules”.
• Animalcules were defined as tiny animals
simple enough to be derived from non-
living material.
6. “Vegetative-Force”
• Spallanzani vs. Needham:
– Spallanzani: Italy 1729, became a priest to the
Catholic Church
• Inspired by Redi’s research
– Needham: Western Europe, priest to catholic
church (same years as Spallanzani)
• Boiled mutton gravy and corked flasks, returned to
discover that their were microbes swimming in the
gravy
– Concluded that the juice created the microbes
7. – Spallanzani: He did not believe Needham’s
conclusions and devised his own experiment to
disprove the theory.
• Spallanzani put various seeds and pure water into
flasks, sealed them and boiled them for hours
– Sealed flasks, No microbes
– Corked flasks, microbes
– Needham: In return, Needham published a
paper about the vegetative force, “the force that
is the source of creation”.
• He claimed that Spallanzani’s experiments were
invalid because boiling the juice for so long
weakens the vegetative force
8. The Theory of Biogenesis
• 1858-Pasteur proved that living cells arise only from preexisting living
cells.
– In other words, life only comes from life.
• His experiment consisted of flasks with S-curve in the neck of the
bottle
– The S-curve would allow air into the bottle but would trap any
contaminants, such as mold spores, in the air in the neck of the flask.
– He boiled some broth and it remained sterile.
• Pasteur’s experiment became the basis of aseptic techniques
– For example, pasteurization of milk and other food products. Bacteria
cause spoilage of food products but by raising the temperature high
enough to kill the organisms, the food remains unspoiled for a longer
period of time.
– Pasteurization is still used today
9. Germ Theory of Disease
• Germ Theory of Disease is the idea that microorganisms
may cause disease.
• This theory was hard for many people to accept because
disease was believed to be punishment for crimes or
misdeeds
• In the 1860’s Lister, a physician, applied Germ Theory to
medical procedures
– He noticed that many patients would die following surgery, not
from the original problem but from infection following the surgery.
– He treated surgical wounds with phenol (carbolic acid) and other
surgeons eventually adopted.
– Many lives were saved once this procedure was adopted.
10. Proof that Bacteria Cause
Disease
• Koch worked with Bacillus anthracis, the organism that
causes anthrax.
– 1. He found the organism in blood of dead animals.
– 2. Cultured organisms
– 3. Injected culture into healthy animals
– 4. Animals developed disease and died
– 5. Found same organism in blood
• Koch developed the steps for identifying the causative
agent (organism that causes the disease) of disease. These
steps are called Koch’s Postulates.
• Koch’s postulates led to development of Scientific Method
which is still used today in conducting research.
11. Smallpox (1st vaccination)
• Milkmaid worked around cows with cowpox.
• She informed Edward Jenner (British Physician)
that couldn’t get smallpox because she had been
exposed to cowpox.
• Jenner put her theory to the test by using scrapings
from cowpox blisters.
• A mother volunteered her son to be experimented
on because she desperately wanted him to be safe
from smallpox.
12. • Jenner scraped his arm and put in scrapings
from the cowpox blister into the wound.
The boy developed a small sore that quickly
cleared up. Then Jenner injected him with
smallpox to see if he would get sick. He
was immune to the disease.
• This procedure was called vaccination. The
word vaccination was derived from the latin
word vacca, meaning cow.
13. Some Understanding of
Immunity
• 1880-Pasteur noticed that the organism that causes fowl
cholera lost ability to cause disease after grown in lab for
long periods.
• Pasteur was experimenting with fowls and fowl cholera.
He started with a very virulent (see definition below) strain
of the disease. Each time he would inject a new bird with
the organism it would die.
• Over time he noticed that the birds began to live in spite of
the injections with the disease.
• Then he noticed that when he injected them again with a
fresh new strain, they still didn’t get sick.
14. • Pasteur conluded that the strain that had
been grown in the lab for a long period of
time was still able to cause an immune
response, but it wasn’t strong enough to
make the bird sick. Thus the animals
became immune to the disease.
• Definitions:
– Virulent: able to cause disease
– Avirulent: unable to cause disease
15. Drug Treatment
• Sulfa drugs were the first type of medicine prescirbed for
infections.
– Made from dyes used for fabrics
• Antibiotics were discovered first in 1928.
– Alexander Fleming was conducting experiments with bacteria on
agar plates. In the process of one experiment he discovered that
his plates had been contaminated with mold (Penicillium notatum).
He threw those plates in the trash.
– Then he started to think about what he had seen on those plates and
retrieved them from the trash can. He noticed that all around the
mold was an area where bacteria was not growing. It occurred to
him that the mold must be killing the bacteria. That was how
penicillin was discovered.
– Many antibiotics that we use today are made by other organisms.
16. • A problem that physicians and scientists face
today is microorganisms becoming resistant to
antibiotics
• Vancomycin resistant Staphylococcus areus and
Enterococcus faecalis, may become untreatable if
they continue to acquire drug resistance. Then the
infection will not be able to be stopped.
• Unfortunately it is very time consuming to
conduct the research necessary to discover new
antibiotics and costly to manufacture synthetic
drugs. So it may be years before a new family of
antibiotics is available to use.
17. Microbes and Human Disease
• Definiton: Normal microbiota or flora
– Normal variety of microbes that live on or inside our
bodies
– Occassionally normal microbiota can make us sick or
infect people with whom we come in contact
(opportunistic pathogen)
• An opportunistic pathogen is one that can cause disease
when the conditions are right, the immune system is
suppressed or the body is weakened in some way.
• Emerging Infectious Diseases
– BSE, AIDS, Hanta, Ebola, Dengue, Cryptosporidum
18. Modern Microbiology
• Microbiology is now divided into several separate fields of
study.
• Bacteriology: study of bacteria.
– 1997-new bacterium discovered, Thiomargarita namibiensis
– All organisms going through reclassification due to genomic
studies
– Previously classified according to visual characteristics and
metabolic characteristics
• Mycology: study of fungi.
– Increase in fungal infections by Coccidioides immitis
• Parisitology: study of parasites.
– protozoa and parasitic worms continually found.
19. • Immunology: study of the immune system
– Dates back to Edward Jenner (1796)
– Some vaccines developed since, but new
vaccine research is rapidly growing due to
ability to manipulate DNA
– Eradication of Smallpox
– Biggest challenge is AIDS, still no known cure
and no vaccine possibilities yet.
• Destroys immune system
20. • Virology: study of viruses
– Tobacco Mosaic Disease: disease that kills tobacco
plants that is caused by a virus
– When scientists first tried to study it, they tried looking
for it under the microscope but couldn’t see anything.
– Then they tried isolating it by grinding up the leaves
and passing the mixture through a bacterial filter.
– It was believed that infectious organisms would not
pass through an unglazed filter made of porcelain
because the pore size is so small.
– The infecting organism passed right through the filter
and they could not isolate it at that time.
– The juice that passed through the filter still containing
the virus was called a “Contagious living fluid”, which
is what the latin word virus means.
21. Leading up to Genetic
Engineering
• 1944-Discovery of DNA as genetic material
of the cell
• 1946-Discovery of conjugation, a method of
transfering DNA between living bacterial
cells.
• 1953-Watson and Crick proposed model for
structure and replication of DNA
22. Conclusion
• There are many men and women who have
contributed to our understanding of Microbiology
over the years. I am constantly amazed by the
brilliance of their experiments and the fascinating
discoveries they made.
• I hope that through this course you will discover
and understand the amazing world of
Microbiology is too.
