BIOC17H3 Lecture Notes - Lecture 2: Microbial Metabolism, Petri Dish, Carbohydrate
5 Jul 2018
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C17 LECTURE #2
- Cover wounds to prevent “dirty” air from flowing in
- Animalcules were found in healthy people why associate with disease?
oIf small, how could they take over a human being?
Germs cause disease
- Allowed to lower rate of
disease caused by
infection once identified
what caused disease
What allowed to develop
microbiology as a science?
-Microscopy
-Pleomorphism
-Spontaneous generation
Invisible germs and contagion
- Was concept of germs Fracastoroius something in the air that can carry disease
oCalled it contagion
oThought it could transfer between people
oThe plague
- Older concept was to search for miasmas, didn’t know that microbes caused it
-Louis Pasteur
oImportant person in germ theory of disease
oEliminated the idea of spontaneous generation b/c this flask showed that despite
air flow, there was no microbial growth in organic matter
oWas chemist worked on practical aspects of biology
oTried to solve contamination problems in the production of alcohol, wine, beer
found: alcohol produced in wine and beer was produced by microbes yeast
oBefore the idea was that alcohol just appeared b/c chemical reactions
oPasteur showed that it was done by yeast
oDifferentiated between alcoholic and acid fermentation
Some convert it into acid, others convert it into acid
oProblem in France: wanted to produce wine, but it was ruined b/c instead of
producing alcohol, it kept producing acid (vinegar)
Associated alcohol fermentation with presence of yeast (fungi)
oFound: yeast was being lost and being replaced by bacteria the bacteria was
converting the acid
This was causing disease
oFound similar problem in silk production silkworms were dying found that
there was a fungus that was killing the silkworms
oHelped to develop the pasteurization process (eg. Milk heat milk at 70*C,
could kill the majority of bacteria that were responsible for converting it into
yogurt or cheese)
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oAll of these ideas led to him thinking that germs produce disease (germ theory
of disease)
oFather of food microbiology, industrial microbiology, and biotechnology
oAlso involved in the production of vaccines
- Needed direct evidence to link microbes to disease
oRequires: to isolate a particular microbe and prove that it produces a disease
oDone by Koch and Pasteur
-Koch: identified and described pathogenic bacteria, Pasteur was interested in how to
protect animals and humans from disease
- Both
-Pasteur’s methods yield cultures enriched w/ the bacteria of interest (have more of that
bacteria of interest than those you don’t want)
oKoch managed to isolate microorganism to pure culture
Found TB caused tuberculosis
The etiology of anthrax disease
- Both Koch and Pasteur worked on anthrax
- Anthrax killed animals like cows
1. Pasteur
a. Inoculated sick rabbit (experimental animal model) in neutral urine (culture
media) takes bacteria from animal grows it in culture media did not
directly put bacteria tissue from sick rabbit and inject into healthy rabbit
rather, grew the bacteria after 100 gen still infected after 100 gen., which
means that tissue itself wasn’t responsible, rather that it was just the
bacteria itself causing disease in the health rabbit
a.i. Didn’t inject b/c that would mean that it might be possible that tissue
might be responsible
b. Culture maintained for many gen. in the medium
c. Bacteria grown in condition for 100 gen = cause anthrax in rabbits
d. Developed vaccine for anthrax
2. Koch
a. Passed bacteria through
successive cycle in vitro
and in vivo (animal
model) provided
anthrax injected into
animals cause disease
b. Developed isolation
method to isolate bacteria
pure culture
c. Method: take bacteria
from spleen on cow
inject into healthy mouse
mouse will die recover
bacteria from that mouse repeat process several times (controlling that the
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same bacteria is there) after passing bacteria from several generations, he
took bacteria from mice, put into culture media (liquid from Ox eyes)
found bacteria was growing there in injected into health mouse again, it
dies
c.i. Control: inject bacteria from healthy cow into healthy rat = healthy
- Naturally, bacteria grow in complex mixed populations can’t study them in a mixed
culture
-A pure culture: a population of cells arising from a single cell (composed of a single
species)
- To provide direct link between a microbe and disease, need a pure microbial culture
- Koch found: grow bacteria on a surface where they can spread a population of
microbes grow to the point where you have single cells there
oSpread the mix on the surface of solid media that contains all the nutrients
required for microbial growth
oTried to spread them on:
1. potato starch ------- X (there are many enzyme that can liquefy
starch)
2. Gelatine + culture broth ----- X (gelatine at 37-40* will naturally
liquefy)
3. Coagulated blood serum ----- X
4. Agar-agar + nutrient ----- GOOD (why? Carbohydrate is very resistant
to microbial activity, and can keep a nice gel at 37-40* & can sterilize at
very high temperature)
How to grow?
- Start media w/ nutrients pour agar-agar sterilize it pour it into petri dish (cover
dish) once it solidifies, add the microbial samples using the spreader that can isolate
bacterial cells from eachother they will multiply/grow until you can see with your eyes
- If the cells from a mixture of microbes
can be spatially confined and isolated
from eachother, each cell will divide
to produce a colony (cluster of cells
occurring in or oon solid media)
- Each one of the dots is a colony pure
culture if that bacteria produced
disease, then it would be causal agent
of disease
- Process: colony of bacteria will be
formed from a single cell wil now
have a pure culture of strain
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Document Summary
Cover wounds to prevent dirty air from flowing in. Allowed to lower rate of disease caused by infection once identified what caused disease. Was concept of germs fracastoroius something in the air that can carry disease: called it contagion, thought it could transfer between people, the plague. Older concept was to search for miasmas, didn"t know that microbes caused it. Some convert it into acid, others convert it into acid: problem in france: wanted to produce wine, but it was ruined b/c instead of producing alcohol, it kept producing acid (vinegar) Associated alcohol fermentation with presence of yeast (fungi: found: yeast was being lost and being replaced by bacteria the bacteria was converting the acid. Needed direct evidence to link microbes to disease: requires: to isolate a particular microbe and prove that it produces a disease, done by koch and pasteur. Koch: identified and described pathogenic bacteria, pasteur was interested in how to protect animals and humans from disease.
