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Introduction to
Microbiology
(BIOL 260)
Microbes in Our Lives
• Microorganisms or microbes:
organisms that are too small to be seen
with the unaided eye
─Bacteria
─Fungi
─Protozoa
─Viruses
Microorganisms:
What do they do?
• Decompose organic waste as well as environmental
pollutants and toxins (bioremediation)
• Are producers in the ecosystem by photosynthesis
• Produce industrial chemicals such as ethyl alcohol and
some enzymes
• Produce fermented foods such as vinegar, cheese,
and bread
• Normal intestinal flora aid in our food digestion and
produce vitamins B and K for us (normal microbiota)
• A minority are pathogenic
Why study microbiology?
• Allows humans to
─ Prevent food spoilage
─ Prevent disease occurrence
◦ Develop aseptic techniques to prevent
contamination in medical environments
─ Treat infectious diseases
─ Understand certain body processes
─ Produce foods and therapeutic agents
Examples of microorganisms
Haemophilus influenzae
Mucor (bread mold)
Amoeba
Volvox (pond algae)
HIV particles budding
from a T cell
Figure 1.1
Classification of Organisms
• Three domains:
─ Bacteria (cell walls contain peptidoglycan)
─ Archaea (if present, cell walls lack peptidoglycan)
─ Eukarya
◦ Protists (slime molds, protozoa, algae)
◦ Fungi (unicellular yeasts, multicellular molds and
mushrooms)
◦ Plants
◦ Animals (sponges, worms, insects and vertebrates)
Taxonomic Hierarchy
Scientific naming
(binomial nomenclature):
Genus species
Figure 10.5
Naming and Classifying Microorganisms:
Scientific Nomenclature
• Each organism has two names: the genus and
specific epithet (underlined or italicized)
─ Saccharomyces cerevisiae
─ Escherichia coli
─ Staphylococcus aureus
─ S. cerevisiae, E. coli, S. aureus
• Scientific names of organisms may be descriptive or
honor a scientist
Major groups of microorganisms:
Bacteria
• Prokaryotic
• Unicellular organisms
• Peptidoglycan cell walls
• Reproduction: Binary
fission
• Diverse range of
energy sources
Figure 1.1a
Major Groups of Microorganisms:
Archaea
• Prokaryotic
• Lack peptidoglycan
• Often live in extreme
environments
─ Extreme halophiles
─ Extreme thermophiles
Figure 4.5b
Major Groups of Microorganisms:
Fungi
• Eukaryotic
• Chitin cell walls
• Unicellular or multicellular
organisms
─ Molds and mushrooms are
multicellular
─ Yeasts are unicellular
Figure 1.1b
Major Groups of Microorganisms:
Protozoa
• Eukaryotic
• Unicellular
• May be motile via
pseudopods, cilia, or
flagella
Figure 1.1c
Major Groups of Microorganisms:
Microscopic Algae
• Eukaryotic
• Cellulose cell walls
• Energy source:
photosynthesis
Figure 1.1d
Major Groups of Microorganisms:
Viruses
• Acellular
• DNA/RNA core
surrounded by a protein
coat
─ Coat may be enclosed
in a lipid envelope
• Replicate only when they
are in a living host cell
─ Obligate intracellular
parasites
Figure 1.1e
Major Groups of Microorganisms:
Animal Parasites
• Eukaryotic
• Multicellular animals
• Helminths: Parasitic
flatworms and round
worms
• Microscopic stages
in life cycles
Adult tapeworm
Figure 12.28
A Brief History of Microbiology
The first observations…
• 1665: Robert Hooke reported that life’s smallest
structural units are “cells”
─ Cell Theory: All living things are composed of cells
• 1673-1723: Anton van Leeuwenhoek describes
“animalcules”
─ Observed live organisms in rainwater,
tooth scrapings, feces, etc. etc.
─ Opened up the world of previously
invisible microorganisms
Figure 1.2b
The Debate Over Spontaneous
Generation
From where does such microscopic life
arise?
• Spontaneous generation: the long-held hypothesis
that some living organisms arise from nonliving matter
─ An intangible “vital force” in the air triggers
spontaneous generation
─ Subject of controversy among supporters and
opponents
The Biogenesis Hypothesis
• 1858: Rudolf Virchow challenged the spontaneous
generation hypothesis with the concept of biogenesis
─ Biogenesis: Living organisms arise only from
preexisting life
• Spontaneous generation vs. Biogenesis debate
continued until 1861…
The Theory of Biogenesis Supported
• Pasteur’s S-shaped flask kept microbes out but let
air in
Figure 1.3
Support for the Biogenesis Theory
• 1861: Louis Pasteur demonstrated that microorganisms
─ Are present in the air
─ Can contaminate sterile solutions
─ BUT the air cannot CREATE microorganisms
Applications to current laboratory
and medical practices
• Pasteur’s work also demonstrated that living microbes
can be killed by heat (sterilization)
• These and other discoveries form the basis of aseptic
techniques
─ Techniques that prevent contamination from
unwanted microorganisms
The Golden Age of Microbiology
• 1857-1914
• Immunity
• Antimicrobial drugs
• Fermentation
• Pasteurization
• Relationship between microbes and disease
─ “Germ theory of disease”
The Golden Age of Microbiology:
The Germ Theory of Disease
Theory that microbes can cause disease
• 1865: Pasteur found that a silkworm disease was caused by a
protozoan
• 1867: Joseph Lister began treating surgical wounds with
phenol
─ Significant reduction in surgical wound infections and
deaths
─ Proved that microorganisms cause surgical wound
infections
The Golden Age of Microbiology:
The Germ Theory of Disease
• 1876: Robert Koch provided proof that a bacterium
causes anthrax
─ Koch’s Postulates: the experimental steps used to
prove that a specific microbe causes a specific
disease
The Golden Age of Microbiology:
Vaccination
• 1880: Pasteur coined the term vaccination
─ From vacca, Latin for cow
─ 1796: Edward Jenner inoculated an 8-year-old with
cowpox pustule
◦ The child was protected from smallpox infection
for life (immunity)