August 27 notes

Announcements
Oral quiz on Koch vs. Pasteur

About Pasteur, vaccines: Here's an interesting story about how unfounded vaccine fears are leading lots of parents to not get their kids vaccinated against measles, which has led to a resurgence of measles cases in the U.S. According to the World Health Organization, about 27 children die every hour of measles worldwide.

I. Some background on bacteria, the dominant form of life on planet earth
a. Numerical and mass dominance
i. Numerical: one colony has more then 1 billion individual bacteria
ii. Mass dominance: all the bacteria in the world weigh more than all other non-bacteria life on earth
b. Longevity dominance
i. 3.5 billion years on earth
ii. single bacterium can sometimes survive millions of years (spore)
c. Environmental dominance
i. bacteria created our current 20% oxygen atmosphere thru development of photosynthesis
d. Infectious diseases
i. diseases caused by bacteria and viruses
ii. leading cause of death in history and present times
e. Normal flora
i. bacteria that are symbionts of humans that live on/in us
ii. symbionts —> live together and help each other survive
iii. What do the normal do for humans?
a. digest our food
b. make vitamins ex. Vit. K
c. occupy niches on body, outcompete pathogens
II. Spontaneous generation
a. The evidence for spontaneous generation
i. Of mice and maggots
ii. “Putrefaction” of food
iii. Falsifiability and the nature of science
Was it reasonable for people to believe in spontaneous generation? Yes-people only supported spontaneous generation and for the longest time didn't try to disprove it
b. Spallanzani experiment
c. Pasteur’s swan-necked flasks

III. The Germ Theory of Disease
a. Previous ideas about disease causation: Humors-the body has fluids: blood, bile, phelm, etc & imbalance of these fluids caused disease
Was it reasonable to believe in humoral imbalances as a cause for diseases? What support did doctors have for that belief? Once again, yes it was bcuz ppl were only looking to support this belief. Doctors would bleed a patient suffering from a severe headache & the next day it was gone, therefore, supporting this belief.
b. Previous ideas about disease causation: Miasmas
Was it reasonable to believe in Miasmas as a cause for epidemics? What support is there for this belief?
c. John Snow ad the Broad Street Pump
i. In 1849 stopped an epidemic by stopping ppl from drinking the contaminated river water
d. Koch’s Postulates-How can we tell if a particular set of symptoms are caused by a particular germ?
i. Must find microbe in every patient with disease
ii. Must take sample of microbe from patient & grow in a pure culture
iii. Inoculate healthy animal with microbe & see the same symptoms
iv. Must be able to culture same microbe from the experimental, infected animal
Are there diseases caused by microorganisms that are exceptions to Koch’s Postulates? Why?

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