Bacteria are microscopic, unicellular organisms. A typical bacterium is only a few micrometers in size. Because of their small size, large numbers of bacteria can be found even in a small volume. For example, there are often a billion bacteria in one gram of soil (less than one-quarter teaspoon). Bacteria are ubiquitous in the environment. They are present in the atmosphere, in soil, in water, and associated with the other organisms. In fact, there are types of bacteria that flourish in the depths of the ocean, in boiling hot springs, deep beneath the Earth in ground-water aquifers, and in habitats as extreme as battery acid or drain cleaner.
Bacteria are classified as prokaryotes because their DNA is not contained in nuclei. Recent taxonomic work, based on sequences of ribosomal RNA, divides the bacteria into two groups: eubacteria and archaebacteria. These are as different from each other as they are from eukaryotes. At finer taxonomic levels, over 200 genera and...
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© 1999 Kluwer Academic Publishers
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Myrold, D.D. (1999). Bacteria. In: Environmental Geology. Encyclopedia of Earth Science. Springer, Dordrecht. https://doi.org/10.1007/1-4020-4494-1_26
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DOI: https://doi.org/10.1007/1-4020-4494-1_26
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