Classification of Microbes

Types of microbes and their discovery

What is Microbiology?

Microbiology - The study of microscopic (very small) forms of life called microbes.

Microorganism (aka microbe)- an organism or virus too small to be seen without the aid of a microscope.


Life as we know it would not exist without microorganisms.


  • Help obtain nitrogen essential for the survival of plants
  • Aid in digestion
  • Decompose wastes and enriches soil
  • Used in production of food such as wine and cheese
  • Used to produce vaccines and antibodies
  • Cause disease (colds, tuberculosis, malaria, and AIDS)
  • Threats of bio-terrorism and epidemics/pandemics

Early Years of Microbiology

Antonie van Leeuwenhoek (1632-1723)


Dutch tailor, merchant, and lens grinder. Learned to make glass lenses to examine the quality of the cloth he was using as a tailor. Curiosity ensued and Leeuwenhoek began observing other other items under the lens.


The lenses Leeuwenhoek created were able to see 200x the actual size of the items observed.


Leeuwenhoek made detailed observations of the specimens he saw in his lenses. He called the specimen "animalcules" which we now know as microbes.

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Types of Microbes

Other Organisms of Importance to Microbiologists

Parasitic worms


  • many cause disease
  • lab technicians diagnose infections of parasitic worms by finding microscopic eggs and immature stages in blood, fecal, urine, and lymph specimens.

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Critical Thinking

A few bacteria produce disease because they derive nutrition from human cells and produce toxic wastes. Algae do not cause disease. Why not?

Using your notes take 5 minutes to complete the following

  • Describe the world-changing scientific contributions of Leeuwenhoek.
  • List six groups of microorganisms
  • Explain why protozoa, algae, and non-microbial parasitic worms are studied in microbiology.