MadSci Network: General Biology

Re: Are we all sun-suckers?

Date: Mon Dec 9 18:32:18 2002
Posted By: Ron Morgan, Staff, Health Physics/Radiological Engineering
Area of science: General Biology
ID: 1014614532.Gb

Hi Ben,
Actually, as I understand it, even the organisms around deep-sea vents 
are dependant on the sun as well, because the end of their chain of 
metabolism requires oxygen (an electron donor).  Therefore, unless there 
was an oxygen reservoir in the deep ocean in "the early days," i.e. four 
billion years or so ago, the organisms around deep-sea vents are relative 
newcomers to the Earth (unless they evolved to exploit oxygen) and 
are "sun-suckers" as much as we are (a very old reservoir of oxygen is 
possible, but I'm not familiar with one).

However, there are organisms in the crust of the Earth that MAY not be 
connected to the sun in any way.  Organisms (bacteria) have been found in 
deep boreholes that metabolize sulfur found in the host rocks.  Bacteria 
(and perhaps other organisms) evidently dwell in small cracks very deep 
in the crust (tens of thousands of feet), but I'm not familiar enough 
with their metabolism to know if the end of the chain is oxygen.

With respect to "fundamental differences," I'm not sure at the level 
where bacteria operate that using oxygen or using some other electron 
donor as a step in the chain of metabolism could be 
considered "fundamentally different."  In fact, metabolism as we know it 
requires a transfer of charge (electrons).  In order to be fundamentally 
different, I would expect metabolism to operate in a "closed loop" of 

Great talking with you, Ben.  Keep the questions coming.  ron

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