|MadSci Network: Microbiology|
An article appeared in the October 1996 issue of National Geographic concerning the symbiotic mussels living near brine pools in the deep ocean off the coast of Texas. The existence of the pools and the diversity of life near them is a relatively new discovery so there's not a lot of information. Bacteria live in the mussels' gill tissues. The bacteria find a "safe place" to live, but are also a source of food for the mussel. Most of the bacteria found in these locations are methanogens (PDF file of a thesis, see p. 18), a subset of microbes referred to as Archaebacteria.
Bacteria also form the basis of other deep ocean ecosystems such as the geothermal vents found off the Galapagos Islands. Here too, the microbes live off of inorganic compounds released from the vents. The microbes use these inorganic compounds (mostly sulfur-based) to create energy for their cellular processes. No light penetrates to these depths, so photosynthesis is not an option.
In addition, methanogens live in a variety of terrestrial habitats. A cow's stomach is one good place to find them as they assist with the digestion of grasses eaten by the cow.
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