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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