Transcript PPT - kimscience.com

UNIT 2: HISTORY OF
MICROBIOLOGY &
BACTERIAL GENETICS
Unit 2 Overview:
• 1. History of Microbiology
• Video
• Koch’s postulates
• 2. Bacterial Growth and Metabolism
• Growth Requirements for Bacteria
• Bacterial Metabolism
• Culturing Bacteria and Sterile Technique
• 3. Bacterial Genetics
• Central Dogma in Bacteria
• Bacterial Transformation
• Bacterial Conjugation
HOW DID MICROBIO
BECOME A FIELD?
• 1665: Robert Hooke reported that living
things were composed of little boxes, or
cells
• 1858: Rudolf Virchow said cells arise
from preexisting cells
• Cell theory: All living things are
composed of cells and come from
preexisting cells
The First Observations
• 1673-1723:
Antonie van
Leeuwenhoek
described live
microorganisms
• http://www.ucmp.berkeley.edu/history/lee
uwenhoek.html
Figure 1.2a
Leeuwenhoek’s microscope
The Debate over Spontaneous Generation (
a very long lasting debate….)
• Spontaneous generation: The hypothesis
that living organisms arise from nonliving
matter; a “vital force” forms life
• Biogenesis: The hypothesis that the living
organisms arise from preexisting life
Evidence Pro and Con
• 1668: Francesco Redi filled 6 jars with
decaying meat
Conditions
Results
Three jars covered with fine
net
No maggots
Three open jars
Maggots appeared
From where did the maggots come?
What was the purpose of the sealed jars?
Spontaneous generation or biogenesis?
Evidence Pro and Con
• 1745: John Needham put boiled
nutrient broth into covered flasks
Conditions
Results
Nutrient broth heated, then
placed in sealed flask
Microbial growth
From where did the microbes come?
Spontaneous generation or biogenesis?
Evidence Pro and Con
• 1765: Lazzaro Spallanzani boiled
nutrient solutions in flasks
Conditions
Results
Nutrient broth placed in
flask, heated, then sealed
No microbial growth
Spontaneous generation or biogenesis?
Evidence Pro and Con
• 1861: Louis Pasteur demonstrated that
microorganisms are present in the air
Conditions
Results
Nutrient broth placed in
flask, heated, not sealed
Microbial growth
Nutrient broth placed in
flask, heated, then sealed
No microbial growth
Spontaneous generation or biogenesis?
The Theory of Biogenesis
• Pasteur’s S-shaped flask kept microbes out
but let air in
Figure 1.3
The Golden Age of Microbiology
• 1857–1914
• Beginning with Pasteur’s work, discoveries
included the relationship between microbes
and disease, immunity, and antimicrobial
drugs
The Germ Theory of Disease
• 1835: Agostino Bassi showed that a silkworm
disease was caused by a fungus
• 1840s: Ignaz Semmelweis advocated hand
washing to prevent transmission of puerperal
fever from one OB patient to another
• 1860s: Applying Pasteur’s work showing that
microbes are in the air, can spoil food, and
cause animal diseases, Joseph Lister used a
chemical disinfectant to prevent surgical
wound infections
Thomas Eakins
The Gross Clinic 1875
The Agnew Clinic 1889
Lister and Semmelweis
Fermentation and Pasteurization
• Pasteur showed that microbes are responsible for
fermentation
• Fermentation is the conversion of sugar to
alcohol used to make beer and wine
• Microbial growth is also responsible for spoilage
of food
• Bacteria that use alcohol and produce acetic acid
spoil wine by turning it to vinegar (acetic acid) and
bacteria that utilize lactose to produce lactic acid
transform milk into yogurt
Fermentation and Pasteurization
• Pasteur demonstrated that
these spoilage bacteria could
be killed by heat that was not
hot enough to evaporate the
alcohol in wine
• Pasteurization is the
application of a high heat for
a short time
Figure 1.4
Pasteurization
• Reduces spoilage organisms and pathogens
• Equivalent treatments
• 63°C for 30 min
• High-temperature short-time: 72°C for 15
sec
• Ultra-high-temperature: 140°C for <1 sec
• Thermoduric organisms survive
The Germ Theory of Disease
• 1865: Pasteur believed that another silkworm
disease was caused by a protozoan
• 1876: Robert Koch proved that a bacterium
causes anthrax and provided the
experimental steps, Koch’s postulates, to
prove that a specific microbe causes a
specific disease
The Germ Theory of Disease
Robert Koch
(pronounced “coke”)
-
German physician and
bacteriologist
- Lived 1843-1910
- Developed a criteria for
determining whether a given
bacteria is the cause of a
given disease:
- Known as Koch’s Postulates
The Germ Theory of Disease
Koch’s Postulates
1. The microorganism must be found in all
organisms suffering from the disease, but not in
healthy organisms.
2. The microorganism must be isolated from a
diseased organism and grown in pure culture.
3. The cultured microorganism should cause
disease when introduced into a healthy
organism.
4. The microorganism must be again isolated from
the inoculated, diseased experimental host and
identified as identical to the original specific
causative agent.
Koch’s Postulates
Figure 14.3
Koch’s Postulates
Figure 14.3
Procedures Overview
Postulate 1
The microorganism must
be found in all
organisms suffering from
the disease, but not in
healthy organisms.
1. Compare yogurt and milk and define the symptoms
of “yogurtness”:
- microscopic observations
- textures, consistency
- smell
- pH
Milk simulates a “healthy” sample
Yogurt simulates a “diseased” sample
Postulate 2
The microorganism must
be isolated from a
diseased organism and
grown in pure culture.
2. Observe the cultures using a microscope and
compare the different types of colonies.
3. Inoculate 3 separate petri dishes:
Heathy individual- milk
Diseased individual- yogurt
Control bacteria- E.coli (control)
4. Grow cultures overnight at 370C
Postulate 3
The cultured microorganism
should cause disease when
introduced into a healthy
organism.
5. Inoculate fresh milk with bacteria colonies from the
petri dishes
6. Incubate overnight 370C
7. Assess symptoms of the subject (pH, smell, texture).
Are these the same symptoms of “yogurtness”?
Postulate 4
The microorganism must
be again isolated from the
inoculated, diseased
experimental host and
identified as being
identical to the original
specific causative agent
8. Observe yogurt and milk under the microscope: Can
the bacteria be matched to the original culture?
Got Yogurt?