Chapter 1:

An Invisible World

2. A Systematic Approach

3. Types of Microorganisms

1. What Our Ancestors Knew

1.1 – What Our Ancestors Knew

Fermented Foods & Beverages

Evidence for fermented foods (e.g., yogurt, beer, wine, etc) dates

back as far as 7000 BC!

• the microbial basis (i.e., yeast and bacteria) was, of course, not known

Health & Disease

Hippocrates (400 BC)

• Diseases have

natural causes

• First cause no harm

Thucydides (400 BC)

• Evidence-based

• plagues survivors

immune

Varro (36 BC)

• Proposed unseen

“minute creatures”

cause disease

Anton van Leeuwenhoek (1673)

The first to observe microorganisms using his “magnifying lenses”.

• essentially began the

field of microbiology

• the importance of

microorganisms for

human welfare was not

appreciated until almost

200 years later!

The Discovery of Microorganisms

Contributions of Louis Pasteur

2. disproved concept of spontaneous generation (1861)

• i.e., microbes do NOT arise from non-living material

1. Proposed “Germ Theory” of disease (1857)

3. Showed fermentation to be

carried out by microbes (1861)

4. Developed technique of

pasteurization to prevent food

and beverage spoilage

5. Developed several attenuated

vaccines

Contributions of Robert KochIdentified the first bacterial pathogens:

Developed numerous advances in

microbiological techniques:

• simple staining methods

• fixation of specimens to slides

• pure culture techniques

• methods for counting microbes

• Bacillus anthracis (anthrax – 1876)

• Mycobacterium tuberculosis (tuberculosis – 1882)

• use of solid growth media

• accomplished by applying “Koch’s Postulates”

1.2 – A Systematic Approach

The Taxonomic Hierarchy

First proposed by Carolus Linnaeus in 1735.

*

*

* Added later

Binomial Nomenclature

To avoid confusion, Linnaeus also proposed a way of

naming organisms that is still used today:

• every type of organism is referred by its genus name

followed by its specific epithet (i.e., species name)

Tyrannosaurus rex (T. rex) Escherichia coli (E. coli)

• names are Latin (or “Latinized” Greek) with the genus being a noun

and the specific epithet an adjective

• name should be in italics and only the genus is capitalized

which can also be abbreviated

**strain info can be listed after the specific epithet (e.g., E. coli O157:H7)**

“Evolution” of the Tree of Life

Modern Tree of Life

* *

* organisms

covered in

this course

*

(helminths)

Dinoflagellates

Carl Woese & George

Fox (1970s):

• discovered the

Archaea

• created the taxon

“Domain”

• based on rRNA

analysis

1.3 – Types of Microorganisms

Prokaryotes – Bacteria

• colonize all but the most extreme environments

• come in a variety of morphologies and arrangements

• chemically and metabolically very different from archaea…

Prokaryotes – Archaea

• direct ancestors of all Eukaryotes

• not very well studied or understood

• many species

colonize very

harsh or extreme

environments

(e.g., high temp,

acid or salt)

Eukaryotes - Protists

Protists are mostly single-celled eukaryotes:

Algae

photosynthetic protists (“plant-like”)

Diatoms

Protozoa

heterotrophic protists (“animal-like”)

Giardia lamblia

Eukaryotes – Fungi

• all are eukaryotic heterotrophs with cell walls made of chitin

• unicellular (yeasts) or multicellular (molds, mushrooms)

Saccharomyces cerevisiae

Molds

Eukaryotes – Helminths

Parasitic worms in the Animal Kingdom:

Flatworms (Platyhelminthes) Roundworms (Nematodes)

Taenia saginata (tapeworm) Dracunculus medinensis (Guinea worm)

Viruses

Non-cellular, “non-living” pathogens consisting of a protein capsid

containing genetic material in the form of DNA or RNA.

Coronavirus Ebolavirus

Key Terms for Chapter 1

• heterotroph

• helminth

• protozoa, algae

• archaea

• pathogen

• morphology, arrangement