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Chapter 1
The Main Themes of Microbiology
Microbiology
Microbiology
is a specialized area of biology that deals with
living organisms ordinarily too small to be seen without
magnification
Such
microscopic organisms are collectively referred to as
microorganisms or microbes
Microorganisms
include:

bacteria

viruses

fungi (microscopic, fungal spores)

protozoa (unicellular)

helminths (parasitic worms)

algae
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Microbiology
Microbiology
is one of the largest and most complex of the
biological sciences because it integrates subject matter from
many diverse disciplines
Microbiologists
study every aspect of microbes

their genetics

their physiology

characteristics that may be harmful or beneficial

the ways they interact with the environment and with their hosts

their uses in industry and agriculture
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Microbiological Endeavors-A sampler
Immunology
Public
health microbiology and epidemiology
Food,
dairy and aquatic microbiology
Agricultural
microbiology
Biotechnology
Genetic
engineering and recombinant DNA technology
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Specialty Professions of Microbiology
Geomicrobiologists
- focus on the roles of microbes in the
development of earth’s crust
Marine
microbiologists - study the oceans and its smallest
inhabitants
Pharmaceutical
microbiologists - discover and develop new
drugs from microbial sources
Nurse
epidemiologists - analyze
infectious diseases in hospitals
Astrobiologists
the
occurrence
of
- study the possibilities of organisms in
space
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The Impact of Microbes on Earth
For
billions of years, microbes have extensively shaped the
development of the earth’s habitats and the evolution of
other life forms
Procaryotes
Eucaryotes
(no nucleus) appeared first
(with nucleus) appeared later
Microbes
can be found nearly everywhere, from the deep in
the earth’s crust, to the polar ice caps and oceans, to the
bodies of plants and animals
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Microbial Involvement
Nutrient
Energy
production (photosynthesis)
flow through the earth’s ecosystems
Decomposition
and nutrient recycling
Biotechnology

production of foods, drugs and vaccines
Genetic
engineering
Bioremediation
Infectious
diseases
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Infectious Diseases and the Human
Condition
Humanity
is plagued by nearly 2,000 different microbes that
can cause various types of diseases - pathogens
Infectious
diseases still devastate human populations
worldwide, despite significant strides in understanding and
treating them
10
B new infections/year worldwide (WHO)
12
M deaths from infections/year worldwide
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The General Characteristics of
Microorganisms
Prokaryotes
and eukaryotes

prokaryote – microscopic, unicellular organisms, lack nuclei and
membrane-bound organelles

eukaryote – unicellular (microscopic) and multicellular, nucleus
and membrane-bound organelles
Viruses

acellular, parasitic particles composed of a nucleic acid and
protein
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Microbial Dimensions
Prokaryotes
Viruses
are measured in micrometers (10-6 m)
in nanometers (10-9 m)
Helminths
are measured in millimeters (10-3 m)
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Insert figure 1.7
measurements
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Lifestyles of Microorganisms
The
majority of microorganisms live a free existence in
habitats such as soil and water, where they are relatively
harmless and often beneficial
A
free-living organism can derive all required foods and
other factors directly from a nonliving environment
Many
microorganisms have close associations with other
organisms

parasites - harbored and nourished in the bodies of larger
organisms called hosts

a parasite’s actions may cause damage to its host through
infection and disease
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Historical Foundations of Microbiology
300
years of contributions by many microbiologists
Prominent
discoveries include:

microscopy

The rise of the scientific method

development of medical microbiology

germ theory

modern microbiological techniques
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Antonie van Leeuwenhoek
Dutch
First
Insert figure 1.8
(1632-1723)
linen merchant
to observe living microbes
Single-lens
magnified up to 300X
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Insert figure 1.9 (a)
microscope
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Spontaneous Generation
Early
belief that some forms of life could arise from vital
forces present in nonliving or decomposing matter (flies
from rotten meat, mushrooms on rotting tree, rats and mice
from piles of litter. etc)
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Scientific Method
A
general approach to explain a natural phenomenon
Form
a hypothesis - a tentative explanation that can be
supported or refuted by observation and experimentation
A
lengthy process of experimentation, analysis and testing
either supports or refutes the hypothesis
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Scientific Method
Results
must be published and repeated by other
investigators
If
hypothesis is supported by a growing body of evidence
and survives rigorous scrutiny, it moves to the next level of
confidence - it becomes a theory
If
evidence of a theory is so compelling that the next level of
confidence is reached - it becomes a Law or principle
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Discovery of Spores and Sterilization
John
Tyndall and Ferdinand Cohn each demonstrated the
presence of heat resistant forms of some microbes

Cohn determined these forms to be endospores
Sterility
requires the elimination of all life forms including
endospores and viruses
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Development of Aseptic Techniques
Oliver Wendell Holmes – observed that mothers of
home births had fewer infections than those who gave birth
in hospital
Dr.
Ignaz Semmelweis – correlated infections with
physicians coming directly from autopsy room to maternity
ward
Dr.
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Development of Aseptic Techniques
Lister – introduced aseptic techniques reducing
microbes in medical settings to prevent infections
Joseph

involved disinfection of hands using chemicals prior to surgery

use of heat for sterilization
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Pathogens and Germ Theory of
Disease
Many
diseases are caused by the growth of microbes in the
body and not by sins, bad character, or poverty, etc.
Two

major contributors:
Louis Pasteur and Robert Koch
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Louis Pasteur (1822-1895)
Showed
microbes caused fermentation
and spoilage
Disproved
spontaneous generation of
microorganisms
Developed
Insert figure 1.11
pasteurization
Demonstrated
what is now known as
Germ Theory of Disease
Developed
a rabies vaccine
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Robert Koch (1843-1910)
Established
Koch’s postulates - a
sequence of experimental steps that verified
the germ theory
Identified
cause of anthrax, TB, and
cholera
Insert figure 1.12
Developed
pure culture methods
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Taxonomy: Organizing, Classifying and
Naming Living Things
Formal
system originated by Carl von Linné (1701-1778)
Concerned
with:

classification – orderly arrangement of organisms into groups

nomenclature – assigning names

identification – discovering and recording traits of organisms for
placement into taxonomic schemes
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Levels of Classification
Domain
- Archaea, Bacteria & Eukarya
Kingdom
Phylum
-
or Division
Class
Order
Family
Genus
species
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Naming Microrganisms
Binomial
Gives
(scientific) nomenclature
each microbe 2 names:

Genus - noun, always capitalized

species - adjective, lowercase
Both
italicized or underlined

Staphylococcus aureus (S. aureus)

Bacillus subtilis (B. subtilis)

Escherichia coli (E. coli)
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Evolution - living things change gradually
over millions of years
Changes
favoring survival are retained and less beneficial
changes are lost
All
new species originate from preexisting species
Closely
related organisms have similar features because
they evolved from common ancestral forms
Evolution
usually progresses toward greater complexity
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3 Domains
Bacteria
- true bacteria, peptidoglycan
Archaea
- odd bacteria that live in extreme environments,
high salt, heat, etc.
Eukarya-
have a nucleus and organelles
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Insert figure 1.15
Woese-Fox System
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