Page 17 - MNU microbiology theoritical 2025

General Microbiology & Immunology (PM 401) Second level Semester 4 2024/2025

• Some microorganisms cause Food poisoning that can result in illness and

even death.

• Some microorganisms spoil materials like clothing, leather, wood etc.

Nomenclature of Microorganisms
Carl Linnaeus developed the system for naming organisms referred to as

binominal nomenclature

The name of microorganisms consists of two parts

• The first word is the genus (first letter always capitalized)

• The second word is the species (not capitalized).

• Both words are always italicized or underlined

ex: Escherichia coli or Escherichia coli

The genus name is commonly abbreviated, with the first letter capitalized: that is,

E. coli.

Morphology of Prokaryotic Cells

1) Size

- Bacteria are prokaryotic organisms

- Bacterial cells are about 10 times smaller

than eukaryotic cells and are typically 1–

10 micrometers in length.
- Among the smallest bacteria are members

of the genus Mycoplasma which measure
only 0.3 micrometers.

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General Microbiology & Immunology (PM 401) theoretical handbook Page 6