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[Michaelangelica]

A great "wee beastie" site

The Bacteria: an Introduction.

The present kingdom Bacteria represents those organisms most fundamentally important to the existence and nature of life on Earth. There are a number of ways in which this is apparent, but probably the most crucial is the role played by bacteria in the supply of nitrogen to other living creatures.

The element nitrogen is an essential constituent of all protein (and DNA), and protein is essential to the structure, metabolism and growth of all living things. (Nitrogen is about 16% of the weight of protein).
The Bacteria are the only creatures which are able to convert the nitrogen gas of the atmosphere into chemical forms (ammonia, nitrites and nitrates) which can be utilized by other organisms. Their ability to "fix" nitrogen constitutes a major contribution to the environment in which all other creatures have developed, and upon which those creatures are now, as in the distant past, totally dependent.
The ability of the bacteria to process nitrogen is at least as important to the present state of life on Earth as the ability of plants to produce oxygen.
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Another clear example of dependence upon bacteria is seen in the gut organisms which facilitate much of the food digestion in animals from termites to elephants.
Deprived of their gut flora, none of these animals could survive. In our own case, it has been estimated that we humans carry a larger number of bacterial cells than we possess human cells.
Animal existence at this level is very clearly a partnership. We are each a microcommunity, made up of cells which are themselves the descendants of microcommunities (also involving bacteria) established very early in the history of life on Earth.
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Micrographia: Specimens: Bacteria (Monera).
Index
Micrographia: A Light Microscopy Resource: Directory to photomicrographs of micro organisms and other specimens.