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Welcome to BIO 244
What is microbiology?
Microbiology, traditionally, is the study of "small life forms",
those that are not easily observable with the unaided eye.
These organisms include viruses, bacteria, protists, and even
some fungi and animals. Many of these organisms are
pathogenic, so a large portion of the course will deal with them
in this arena. We will discuss microorganisms in many contexts.
The major topics with which we will be concerned include:
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Biochemistry and Cell Biology
Bacteriology
Virology
Immunology
Pathogenesis and epidemiology
Human infectious diseases
Organisms too small to be seen
with the naked eye are called
microorganisms
(microbes)
Why are they so important?
Significance of Microorganisms
ECOLOGY
•  Primary photosynthesizers in aquatic
environments (account for more than half of
the earth’s total photosynthesis and
molecular oxygen production)
•  Primary decomposers in the soil
•  In terms of biomass and niche-utilization,
microbes (especially bacteria) are the
dominant organisms on earth. Over half of
the biomass on the planet is comprised of
bacteria!
Significance of Microorganisms
SYMBIOSIS
•  E. coli in our large intestines
•  Bacteria and protozoans in termite and cow
guts (allow digestion of cellulose, etc.)
Significance of Microorganisms
COMMERCIAL
•  Yeasts are involved in making alcoholic
beverages and bread
•  Some bacteria are involved in making
cheeses and yogurt
•  Bacteria are genetically engineered to
produce useful chemicals (like insulin)
Significance of Microorganisms
DISEASE - Pathogens
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Viruses - HIV, "the flu”
Bacteria - “Strep throat", tuberculosis
Fungi - "ringworm", yeast infections
Protozoa - malaria
History of Microbiology
...the greatest story ever told
The early days
•  1665 - Robert Hooke observed cells (and
invented the term).
•  1673 - Antoni van Leeuwenhoek observed
microorganisms under the microscope.
•  1796 - Edward Jenner performed the first
“vaccination” by exposing a person to the
cowpox virus. The person was then
protected from smallpox infection.
Spontaneous generation
Can life come from non-life?
•  Most people thought so, until…
•  Rudolf Virchow introduced the cell theory
(cells can come only from other cells,
1858).
•  Subsequently, Louis Pasteur disproved
spontaneous generation in 1861!
Louis Pasteur - the most famous
microbiologist
•  Disproved spontaneous generation - 1861
•  Discovered fermentation
•  Developed pasteurization to make liquid
foods safer
Other milestones
•  Joseph Lister introduced disinfectants to clean
human wounds and prevent surgical infections
(aseptic technique) - 1860's
•  Robert Koch introduced Koch's Postulates, a set of
procedures to determine the causative agent of a
particular disease - 1876
•  Alexander Fleming discovered the first antibiotic Penicillin (1928). It has been used clinically since
the 1940's.
WHO ARE THEY
(Classification of
microorganisms)
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Bacteria (Kingdom Monera)
Protozoa and Algae (Kingdom Protista)
Yeasts and other Fungi (Kingdom Fungi)
Worms (Kingdom Animalia)
Viruses (no kingdom, since they are not
considered to be alive!!)
Kingdom Monera
•  Unicellular Prokaryotes (no nucleus)
•  Bacteria, Archaea
•  Usually have cell wall of peptidoglycan
Kingdom Monera
KINGDOM MONERA
Single-celled prokaryotes (bacteria)
Kingdom Protista
•  Unicellular Eukaryotes
•  Protozoa - Animal like protists (amoeba,
paramecia, no cell walls)
•  Algae - Plant like protists (can photosynthesize,
usually have cell wall of cellulose)
Single-celled eukaryotes (algae, protozoa)
KINGDOM PROTISTA
Kingdom Fungi
•  Multicellular eukaryotic heterotrophs with
external digestion
•  Yeasts are unicellular fungi (an exception
for every rule)
•  Usually have cell wall made of chitin
Kingdom Fungi
Multicellular eukaryotes that exhibit “absorptive digestion”
KINGDOM FUNGI
Multicellular eukaryotes that photosynthesize
KINGDOM PLANTAE
Kingdom Animalia
•  Multicellular eukaryotic heterotrophs with
internal digestion
•  Most microorganisms are microscopic
worms and rotifers.
•  No cell walls
Multicellular eukaryotes that exhibit “ingestive digestion”
KINGDOM ANIMALIA
Viruses
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Acellular obligate parasites
Consist of nucleic acid and protein
Infect all known types of cells
NOT ASSIGNED TO A KINGDOM OF
LIFE!
So… Microbiology is the most important
class ever and by far the most fascinating
topic one could ever imagine!!