Download Chapter 1/Introduction

What Is Microbiology About and Why Is It
Important?
Microbiology is the study of very small organisms
Microorganisms aka microbes
Microbes play important roles in medicine,
agriculture, and industry
Microbes dominate the environment
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Key Concepts in Microbiology
Form and Function
Metabolism
Genetic Systems
Evolution
Impact on Humans
Communities
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Microbiology History
First observed in 1600’s
Could not be systematically studied until 1800’s due
to technical limitations
The role of microbes in nature was not clear at first
Most early studies focused on the role of microbes in
disease
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Influence of Robert Koch
Rigorously demonstrated the link between
microbes and infectious diseases
Identified causative agents of anthrax and
tuberculosis
Developed rules called “Koch's Postulates”
Developed techniques (solid media) for obtaining
pure cultures of microbes, some still in existence
today
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KOCH'S POSTULATES
Experimental aspects
Theoretical aspects
Postulates:
Laboratory
tools:
1. The suspected pathogen
must be present in all
cases of the disease
and absent from healthy
animals.
Microscopy
,
staining
2. The suspected pathogen
must be grown in pure
culture.
Laboratory
cultures
Diseased
animal
Red
blood
cell
Suspected
pathogen
Colonies
of suspected
pathogen
3. Cells from a pure culture
of the suspected
pathogen must cause
disease in a healthy
animal.
Observe
blood/tissue
under the
microscope.
Streak agar plate
with sample
from either a
diseased or a
healthy animal.
Healthy
animal
Red
blood
cell
No
organisms
present
Inoculate healthy animal with
cells of suspected pathogen.
Experimental
animals
Diseased animal
Remove blood or tissue sample
and observe by microscopy.
4. The suspected pathogen
must be reisolated and
shown to be the same
as the original.
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Laboratory
reisolation
and culture
Suspected
pathogen
Laboratory
culture
Pure culture
(must be
same
organism
as before)
Figure 1.20
Koch, Infectious Disease, and Pure Cultures
Koch’s Postulates and techniques dominated the
science of microbiology for almost a century
His emphasis on pure cultures grown under lab
conditions misled microbiologists
Modern microbiology has shifted to more of an
emphasis on microbial communities in natural
conditions
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Koch, Infectious Disease, and Pure Cultures
Koch’s work was “culture-dependent”
So was the science of microbiology for its first 120
years.
Modern methodology is “culture-independent”.
© 2015 Pearson Education, Inc.