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Diatom shell

Microorganisms

Here we take a look at where microorganisms fit in with other organisms using the Three Domains System.

There three Domains:
  • Archaea
  • Bacteria
  • Eukarya

Each Domain consists of one or more Kingdoms:
  • Archaea - Kingdom Archaebacteria
  • Bacteria - Kingdom Eubacteria
  • Eukarya - Kingdom - Protista
  • Eukarya - Kingdom - Fungi
  • Eukarya - Kingdom - Plantae
  • Eukarya - Kingdom - Animalia

Each Kingdom is divided into one or more of Phyla (singular Phylum), each Phylum is divided into one or more Classes, each Class is divided into one or more Orders, each Order is divided into one or more Families, each Family is divided in to one or more Genera (singular Genus), and each Genus is divided into one more Species. Each Species can then consist of a number of strains.

See:
A higher level classification of all living organisms, 2015

[A mnemonic to help in remembering this classification system is Do Keep Plates Clean Or Family Gets Sick.]
Commercial microorganisms are found in a number of these Kingdoms so we will take a quick look at each of them.

Kingdom - Archaebacteria

These are minute, single-cell prokaryotes (cells lacking a membrane-bound nucleus or mitochondria) that have an ancient ancestry of living in extreme conditions such as sulphur-rich deep-sea vents. A number are used commercially.
Kingdom - Archaebacteria

Kingdom - Eubacteria

These are the ‘true’ bacteria that are also prokaryotes. They are single cells and are different from the Archaebacteria in many ways, including the chemistry of their cell walls. Many bacteria play a major role in commercial microbiology.
Kingdom - Eubacteria

Kingdom - Protista

These are minute eukaryotes (cells have a membrane-enclosed nucleus containing chromosomes, and other membrane-bound structures) that are mainly single cells. A number of species have a commercial role.
Kingdom - Protista

Kingdom - Fungi

These are also eukaryotes and include yeasts, moulds and mushrooms. They may be single cells or may form large, multi-cellular structures. Many fungi have been used for thousands of years to make food and drink and have an increasing commercial role.
Kingdom - Fungi

Kingdom - Plantae

Also eukaryotes, this Kingdom includes all multi-cellular plants. Plantae are not covered further in this website except for some algae.

Kingdom - Animalia

Also eukaryotes, this Kingdom includes all multi-cellular animals. Animalia are not covered further in this website.

Images of commercial microorganisms

Microorganisms vary widely in their morphology. This section illustrates some of the main types.
Images of commercial microorganisms

Videos of commercial microorganisms

There are many videos available that show microorganisms in action. This section looks at some of the best.
Videos of commercial microorganisms
If you have any comments on the contents of this page please email me. I value feedback.
David Border - Consultant Microbiologist

Microorganisms 

David Border - Consultant Microbiologist