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01 | A Brief History of Microbiology



THE GOLDEN AGE OF MICROBIOLOGY:
BENEFICIAL MICROBES:
Bread, wine and beer


• One that has a greater impact or culture and society than that of any disease or
epidemic - was domestication of the yeast used by bakers and Brewers
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1: Is spontaneous generation of microbial life possible?

No, Louis Pasteur showed that broth only became cloudy with bacteria when
exposed to bacteria, not just air, using swan neck flasks to trap bacteria
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Observed yeast cells arising from other
yeast cells, showing that life comes from life
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Robert Koch developed the 4 principles to guide scientists in isolating a
disease causing pathogen
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Joseph Lister

instituted sterilization of wounds with a phenol

Florence Nightingale

pioneered for sanitary conditions in hospital wards, including removing
dirty clothes of patients to remove sources of infection
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Edward Jenner

created vaccination to prevent the spread of diseases by injecting small
particles of the virus into people to create an immune response
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- Begin to doubt Aristotle's theory and adopt the view that animals come only
from other animals
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Some days later, Needham observed that the vials were cloudy, and
examination revealed an abundance of "microscopical animals of most dimensions" as
he explained it there must be a "life force" that caused inanimate matter to
spontaneously come to life b/c he had heated the vial sufficiently to kill everything
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01 | A Brief History of Microbiology



Spallanzani's Experiments:
• Boiled infusion for almost an hour and sealed the vials by melting their slender news
closed
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• He concluded 3 things:

- Needham either had failed to heat his vials sufficiently to kill all microbes or had
not sealed the mightily enough
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Pasteur's Experiments:
• Demonstrated spontaneous generation did not exist



• Boiled infusion long enough to kill everything
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• Reported that his "swan-necked flasks" remained free of microbes even 18 months
later
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- The next day, all of these flasks were cloudy with microbes
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01 | A Brief History of Microbiology







The Scientific Method:
The Scientific Method:

Provides a framework for conducting an investigation rather
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2: The scientist generates a hypothesis - that is, a potential answer to the
question
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The scientist then returns to earlier steps in the method, either modifying
hypotheses and then testing them or repeatedly testing accepted hypotheses until
the evidence for a hypothesis is convincing
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• To accept experiments (& their results) as valid:

They must include appropriate control groups - groups that are treated exactly the
same as the other groups in the experiment except for the one variable that the
experiment is designed to test
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01 | A Brief History of Microbiology

(B/c exposure to the dust was the only difference between the control and
experimental groups, Pasteur was able to conclude that the microbes
growing in the infusion arrived from the dust particles)



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Aristotle & John T
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Francisco Redi:

Developed experiments to detect whether flies arose from rotting meat, or from
flies themselves
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One open to air,
one sealed, and another overhead with gauze
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Demo that flies
arose from neither the air nor meat
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Boiled beef grey and infusion of plant material and slewed the vials with
corks
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Concluded there must be a life force cratering
bacteria
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Did not have control vial that was exposed
to air, but not bacteria)



Lorenzo Spallanzani:

Boiled infusion for much longer and sealed them by melting the vial necks closed
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Only proved broth did not creat
bacteria



Louis Pasteur:

Used a goose neck flask to test whether air can create life
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The neck allowed air to move in and out, but trap dust and
microbes in the bend neck
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Showed that
air can be in contact with the broth, but not cause the appearance of bacteria
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9 List 4 steps in the scientific method of investigation



Step 1:

The scientist collects observations that lead to question about a
phenomenon
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Step 2:

Generates hypothesis, or educated guess about the answer to the question
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And info gathered during observations
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(Highly secured experiments and only
test one variable at a time)


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01 | A Brief History of Microbiology





Step 4:

If hypothesis is rejected, revisit observations and question from step 1 to
create another hypothesis
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WHAT CAUSES FERMENTATION?
Pasteur's Experiment
• Discovered that yeast are facultative anaerobes



Facultative Anaerobes:

organisms that can live with or without oxygen
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Industrial Microbiology (biotechnology):

Microbes are intentionally used to manufacture products
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01 | A Brief History of Microbiology































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Shows that yeast could ferment the sugars in grape juice with or without oxygen
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Further discovered bacteria can also ferment grape juice producing acid
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Juices are heated to the right temperature to kill bacteria
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Disproved the theory that air had a life
force
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Developed the process of pasteurization, which is used to preserve food and drink and
create Alcohol
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Eduard Buchner investigated the chemical cause of fermentation
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Showed that fermentation does not require living cells
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(B/c a particular disease is
typically accompanied by the same symptom in all affected individuals)



Pathogen:

A bacterium, virus, or other microorganism that causes disease

→ pathos = disease

→ genein = to produce


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01 | A Brief History of Microbiology



Etiology:

The cause, set of causes, or manner of causation of a disease or condition
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- Observed the formation of resting stages (endoscopes) within the bacterial cells
and showed that the endoscopes always produced anthrax when they were
injected into mice
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• He solved the problem by taking specimens (blood, pus, sputum) from disease
victims and then spearing the specimens onto a solid surface such as a slice of potato
or a gelatin medium
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- Inoculated samples from each colony into laboratory animals to see which
caused disease
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Koch's Postulates


Koch's Postulates

A series of steps that must be taken to prove the cause of any infectious disease






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01 | A Brief History of Microbiology

1: The suspected causative agent must be found in every case of the disease
and be absent from healthy hosts
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3: When the agent is introduced to a healthy, susceptible host, the host must
get the disease
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Gram's Stain
• Danish scientist Christian Gram's procedure involved the application of a series of
dyes, leaving some microbes purple and other pink
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2: Created simple staining techniques for bacteria that allowed scientists to view the
colorless bacteria under a microscope
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4: Used steam for sterilization to prevent infection





5: developed techniques for estimating the number of bacteria in solution based on the
number of colonies that form on a surface after colonization
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6: Used Petri dishes with solid media to culture bacteria



7: ID bacteria as individual species



8: Developed laboratory techniques to transfer bacteria between media using a metal
wire sterilized by that (by sterilizing metal wire, eliminated outside contaminants so he
could grow specific bacteria in the lab)



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1: The disease causing agent must be found in all patients and hot healthy individuals



2: The agent must be able to be isolated and grown in the lab



3: When the agent is introduced to a healthy subject, it must cause the same disease
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Developed a more complicated staining technique called gram stain
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Cells that have a thick cell wall stain purple and are
considered gram positive
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Gram negative bacteria can cause
serious infections in humans
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• In late August 1793, a female Aedes aegypti mosquito bit an infected refugee and
then bit a healthy Philadelphian
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Victims suffered from high fever, nausea, skin eruptions, black vomit, and jaundice
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Explain why
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People who moved away from the area were less exposed to the
vector ∴ less likely to be infected
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Discuss the possible reasons why this would provide at least temporary
relief from the epidemic
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Semmelweis and Handwashing
• Semmelweis hypothesized that medical students carried "cadaver particles" from
their autopsy studies into the delivery rooms and that these "particles" resulted in
puerperal fever
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Who sliced his finger during an
autopsy died after showing symptoms similar to those of puerperal fever
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• Semmelweis be gain requiring medical students to wash their hands with chlorinated
lime water, a substance long used to eliminate the smell of cadavers
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3 - 1
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• He began spraying wounds, surgical incisions, and dressings with carbolic acid
(phenol), a chemical that had previously proven effective in reducing odor and decay in
sewage
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01 | A Brief History of Microbiology

Nightingale and Nursing
• Florence Nightingale was a dedicated English nurse who introduced cleanliness and
other antiseptic techniques into nursing practice
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• Greatest achievements were in nursing education
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Infectious Control & Epidemiology:

The study of the occurrence, distribution, and spread of disease in humans
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After he intentionally inoculated a boy
with pus collected from a milkmaid's cowpox lesion, the boy developed cowpox and
survived
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• Because vaccination stimulates long-lasting response by the body's protective
immune system, the term immunization is often used synonymously today
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Ehrlich's "Magic Bullet"
• Certain procedures and chemicals can limit, prevent and cure infectious diseases
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→ Discovered a chemical active agent that causative agent of syphilis, through
the arsenic-based drug was toxic to humans
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Some people consider Pasteur or Koch to be the Father of Microbiology, rather than
Leeuwenhoek
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01 | A Brief History of Microbiology

Koch developed the Koch's postulates for determining the etiology kcal agent for a
give disease
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His lab developed techniques for isolating colonies on agar
containing media
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The 6 key health practitioners that pioneered public health
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Ignaz Semmelweis:

Observed that women giving birth that were tended by medical students were
dying form puerperal fever at a higher rate than other women
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Hypothesis were further confirmed when a doctor that lived his finger
during surgery died from the same disease days later
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Joseph Lister:

Introduced the concept of antiseptics

Started spraying surgical equipment with phenol that was known to
reduce odor in sewage
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Suspected that infection was coming from contaminated water
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Created awareness for the need to clean water and proper sewage
systems
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Edward Jenner:

Created vaccines

Vaccines are small pieces of infectious viruses, injected into people to
create an immune response to the virus
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Infected a boy with a sample of cowpox
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Opened the field of immunology








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01 | A Brief History of Microbiology

Paul Ehrlich:

Hypothesized that since bacteria were different they could be killed
preferentially without harming the host or non-pathogenic bacteria
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Opened the field of chemotherapy



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Found that immune system
creates a long lasting response when exposed to a pathogen
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Pasteur furthered Jenner's work by producing weakened strains of the same virus to
prevent serious disease
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Hypothesized that different bacteria could be killed preferentially, leaving other
cells unharmed
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Did not find the "magic bullet" but did open up the field of chemotherapy, which is
used to fight off cancer

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