SOC GEN 5 Lecture Notes - Lecture 2: Louis Pasteur, Crystal Violet, Germ Theory Of Disease
Professor Landecker
SocGen5
9/29/16 part2
Basis of Antibiotics
Objectives:
1) Basic Biology: microbes and antibiotics
2) “Miracle drug”
The Germ Theory of Disease (end of 19th century)
1) Before antibiotics→ some diseases are caused by microorganisms→ focus on
prevention and hygiene
2) Rise of Laboratory/experimental science
3) Transition from macro to micro science
4) Louis Pasteur:
a) Discovered “pasteurization”: temperature increase kills bacteria
b) Began use of the term “microbe”; defined as contagious and replicable
5) Robert Koch: search for biological laws→ founder of microbiology
a) Thermodynamics inspired Koch’s Postulates
i) Serve as basis of germ theory
(1) Abundance of microorgs. should be found in all orgs suffering from
disease but not in healthy organisms
(2) Microorg must be isolated in a pure culture
(3) Cultured microorg should cause disease when placed in a healthy
org.
(4) Microorg must be reisolated from the experimental host and
identified as identical to original species
Macro→ micro, whole problem→ isolation of small parts of the whole
1) Problem: needed to prove which bacteria causes what symptom or disease
2) Solution: isolate and retest
a) UNDERSTANDING = INTERVENING
How to Isolate:
1) Streaking bacteria on agar plate to spread out the bacteria→ colonies grow from each
bacterium→ able to identify more clearly which bacteria is which
2) Use coloration to distinguish shapes
3) Use of trial and error
Overview of Germ Theory
1) Key assumption: bacteria are pathogenic
2) Method: isolate + re-inoculate
Document Summary
Macro micro, whole problem isolation of small parts of the whole: problem: needed to prove which bacteria causes what symptom or disease, solution: isolate and retest, understanding = intervening. How to isolate: bacterium able to identify more clearly which bacteria is which: streaking bacteria on agar plate to spread out the bacteria colonies grow from each, use coloration to distinguish shapes, use of trial and error. Overview of germ theory: key assumption: bacteria are pathogenic, method: isolate + re-inoculate. The magic bullet-- kills the evil thing, but not the normal thing: concept of selective toxicity, observation that dyes selectively taken up by some cells or cell parts and not, discovered gram-neg. = takes up crystal violet and shows purple ( stays same color ) = counterstains to pink ; shows purple but fades (1) thicker cell membrane (1) thinner membrane: began question of whether something can kill bacterial cell but not a human cell.
