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The Microbial World and You
Chapter 1
BIO 220
What is microbiology?
• This is the study of microorganisms
(microbes), which are “living” organisms that
can not be visualized with the naked eye.
• We will discuss beneficial as well as disease-
causing microbes.
What are the characteristics of life?
• Composed of one or more cells, which are
made of biomolecules
• Growth
• Reproduction
• Metabolism
• Respond to their environment
• Evolve and adapt
Do all microbes fulfill all of these
conditions of life?
• No
• i.e. prions and viruses
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Nomenclature of living microbes
• Binomial nomenclature – Carolus Linnaeus
• Genus and specific epithet
– i.e. Bacillus anthracis
– Genus name is capitalized, specific epithet is not
– Underlined or italicized
– Genus can be abbreviated after first use
How are microbes named?
• Shape and arrangement of cells (bacteria)
– Staphylococcus aureus
• Scientist
– Escherichia coli (Theodor Escherich)
• Microbe habitat
• Appearance
– Micrococcus luteus
Fig. 10.1
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Types of microbes
• Bacteria
– Prokaryotic cells
– Common shapes include bacillus, coccus, spiral
– Cell walls contain peptidoglycan
• Archaea
– Prokaryotic cells
– Cell walls
– Some, but not all, live in extreme environments (methanogens, extreme halophiles, extreme thermophiles)
– Not known to cause disease in humans
Types of microbes
• Fungi
– Eukaryotic cells
– Mushrooms, molds, yeasts
• Protozoa
– Unicellular eukaryotic cells
– Cell walls
– Move by cilia, flagella, or pseudopods
– Free-living or parasitic
• Amoeba proteus vs. Entamoeba histolytica
Types of microbes
• Algae
– Eukaryotic cells
– Perform photosynthesis
• Viruses
– Acellular
– Nuclei acid and protein
• Prions
– Acellular
– Infectious proteins
Areas of study within microbiology
• Bacteriology – study of bacteria
• Mycology – study of fungi
• Parasitology – study of protozoa & parasitic
worms
• Virology – study of viruses
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Robert Hooke
• 1665 published Micrographia, which was a series of detailed observations on a variety of organisms
• Used a compound microscope
• Hook observed individual cells in thin slices of cork
• Cell theory – all living things are composed of cells
Cell Theory
• All living organisms are composed of cells.
• The cell is the fundamental unit of structure
and function of living organisms.
• Cells arise from pre-existing cells.
Anton van Leeuwenhoek
• 1673-1723 observed “animalcules” through
simple microscopes he constructed
• Probably first to observe living cells
Spontaneous Generation
• For centuries, some scientists believed in the
theory of spontaneous generation, which said
that some forms of life (i.e. flies, maggots,
toads, snakes, mice) could be produced from
non-living material.
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Francesco Redi
• In 1668, he conducted a series of experiments
in an attempt to discount the theory of
spontaneous generation.
The controversy continued . . .
• John Needham (1745) – Theory of
spontaneous generation lives!
• Lazzaro Spallanzani (1765)
(problems)
Theory of Biogenesis
• In 1858, Rudolf Virchow came up with the
concept of Biogenesis, which hypothesizes
that living cells arise only from preexisting
living cells.
Is it biogenesis or spontaneous generation?
• In 1861, Louis Pasteur conducted a series of
experiments that resolved the question.
Fig. 1.3
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Germ theory of disease
• Maybe microorganisms could cause disease
• 1807-1835, Agostino Bassi – identified a
fungus (Beauveria bassiana) as the causative
agent of white muscardine in silkworms
• 1865, Luis Pasteur identified a protozoan
(Nosema bombycis) as another infective agent
of silkworms
Germ theory of disease – applications to
medicine
• 1840s, Hungarian physician Ignaz
Semmelweis noted an unacceptibly high
percentage of patients in the obstetrics ward
died shortly after childbirth
• Hand washing greatly reduced deaths due to
“childbed fever” but Semmelweis’s
conclusions were not welcomed by the
medical establishment
Germ theory of disease – applications to
medicine
• 1860s, Joseph Lister, an English surgeon, was aware of the work done by Semmelweis and Pasteur
• Experimented with using dressings soaked in carbolic acid on patients, which ultimately significantly reduced the loss of patients due to postoperative infections
• Microbes caused surgical wound infections
• Father of antiseptic surgery
Germ theory of disease – applications to
medicine
• 1876, Robert Koch, a German physician, was
the first to definitively show that bacteria
could cause disease
• Koch isolated a bacterium (Bacillus anthracis)
from the blood of cattle that had died of
anthrax
• He isolated and cultured the bacteria and
injected it into healthy cows, which then died
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Koch’s postulates
Fig. 14.3
A series of experimental steps for directly relating a specific
microbe to a specific disease.
Vaccination
• 1796, Edward Jenner collected skin scrapings
from a dairy maid with cowpox
• To test his hypothesis that infection with
cowpox would convey protection against
smallpox, Jenner scraped the skin of a healthy
boy with a cowpox-infected needle
• The boy did not get smallpox
• Pasteur also did some work with vaccinations
against anthrax, chicken cholera, and rabies
Disease-causing microbes
• Bacillus anthracis – anthrax
• Neisseria gonorrhoeae – gonorrhea
• Trypanosoma brucei – African sleeping
sickness
• Prions – Creutzfeldt – Jakob disease
• Giardia lamblia – giardiasis
• Human immunodeficiency virus (HIV)
Good microbes
• Foods and beverages – Saccharomyces
cerevisiae, Penicillium roquefortii
• Pharmaceuticals – Penicillium, Bacillus,
Streptomyces
• Sewage treatment
• Bioremediation
• Insect pest control – Bacillus thuringiensis
• Biotechnology
