Bacteria

All living organisms are composed of cells and although there are many different types of cell they basically divide into two groups; prokaryotic cells and eukaryotic cells. Prokaryotes are bacteria and eucaryotes are all other groups (protocistans, fungi, plants, animals).

The Prokaryotae are divided into Eubacteria (true bacteria) and Archaebacteria (ancient bacteria), and are an extremely successful and diverse group. They occupy almost all terrestrial and aquatic environments from the permafrost layer of the Arctic to the boiling sulphurous hot springs of Yellowstone, they are present in soil, in the air and in and on the bodies of plants and animals.

When present in plants and animals, bacteria may have a positive effect such as helping to break down waste products in the gut or they may have a negative effect such as causing disease. In soil bacteria also have many different roles, they help break down organic matter which enriches the soil with nutrients and allows plants to grow. An important soil bacteria (Bacillus radicicola) turns nitrogen from the air into a form that can be utilised by plants.

Characteristics of prokaryote cells:

1. Less complex than eukaryotes.
2. Smaller than eukaryotes (ranging in size from 1 to 5 m).
3. Evolved long before eukaryotes.
4. Lacks a nucleus and genetic material is confined to a region of the cell called the nucleoid.
5. Lack membrane-bound organelles (carry out metabolic tasks) that the eukaryotes have.
6. Have very short generation times (as little as 20min/generation for some species) and they can increase from 1 cell to 17,000,000 cells at the end of a 24 hour period. This rapid multiplication occurs generally by the bacteria splitting in two.

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File last modified Thursday, October 3, 1996