MadSci Network: Microbiology

Re: hottest temp and greatest pressure for living organism?

Date: Fri Oct 27 11:42:41 2000
Posted By: Andrew D. Brabban, Faculty, Biology, The Evergreen State College
Area of science: Microbiology
ID: 970626165.Mi

Life is now considered by most scientists to have arisen as thermophilic 
organism, (The word thermophile means to love heat). When most people 
first hear this statement view as weird. But we are looking at life from 
our perspective, because we are a mesophile (warm loving) we think 
everything should be that way. However all organisms, including you, have 
an optimum temperature for growth. Outside of that optimum they die, or 
cease to grow. So what causes this to occur? Well, the nature of the cell. 
Organisms have to have the ability to adapt to worldly changes but all 
abilities have limits. Too cold: Fluidity of the membrane is reduced to 
such as state that the membrane no longer allows the transport of 
molecules. Another reason is that enzymes are adapted to operate at 
certain temperatures. At too low of a temperature their effectiveness as a 
catalyst is reduced. Too hot and again lipid and protein function is 
impaired. As the temperature rises the membrane becomes too liquid while 
proteins start to denature.

So who can grow the hottest. 

Pyrolobus: The Pyrolobus group is said to hold the world record for growth 
temperature, growing at 113 oC (Pyrolobus fumarii). It will not grow below 
90 oC because it is too cold. These organisms are found in the walls of 
black smokers on the ocean's floor. I suspect that one of these organisms 
also holds the record for pressure but pressure is not such a problem to 
cells and I have no data here. Although we mainly consider proteins and 
membranes when we mention stability and therefore the extreme temperatures 
of life, as we are all aware that proteins denature etc., perhaps the 
biggest limit to the extremes of life is monomers. The two biggest are ATP 
and NADH, which are highly unstable at temperature above 120 oC. This is 
thought to be the biggest hurdle to life at high temperatures and although 
we suspect there may be organisms out there that can grow up to 150 oC, 
tests of black smokers at 250 oC have shown them to be sterile, so far.

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