Temperature as a Regulating Factor

The sea floor is mostly a cold environment with 85% of the global ocean having temperatures below 5°C. At the other extreme, hydrothermal 

Surprisingly, sulfate reducers adapted to the normal low temperatures of the main sea floor were also unknown until recently. Such cold-adapted (psychrophilic) bacteria are generally scarce among the culture collections in spite of their major biogeochemical significance. This is partly because of their slow growth which makes them difficult to isolate and cumbersome to study. A number of psychrophilic sulfate reducers were recently isolated which have temperature optima down to 7°C and are unable to grow above 10-15°C because it is too hot (Knoblauch et al. 1999). 

These examples demonstrate a general problem in marine microbiology, namely that the large prokaryotic diversity comprises adaptations to very diverse environments and that only a very small fraction, maybe less than one percent, of the bacterial species in the ocean is known to science today. Many of the unknown microorganisms may 

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