Life w/o oxygen?

[Wiley]

Here's a link to an interesting little article that appeared in the NY Times. The link is to the NY Times and registration is required.

Apparently scientists have found microbes that don't need either sunlight or oxygen. Hence, these little guys could live on Mars. Hmmm...

[Donnie B.]

Hi, Wiley,

I believe this has been discussed elsewhere on the board.

What's unique about this discovery is not that the microbes are anaerobic and don't photosynthesize, but that the entire ecological niche is based on such organisms.

[lpetrich]

What was discovered was a whole ecosystem of microbes living in an underground hot spring; the primary producers are methanogens, which do not need to consume either light or organic compounds.

Instead, methanogens live of energy tapped from this reaction

CO2 + 4*H2 -> CH4 + 2*H2O

and use it in plantlike fashion to help build all the organic molecules that they need: nucleic acids, proteins, lipids, sugars, cofactors; the usual stuff.

[Wiley]

On 2002-01-23 15:06, Donnie B. wrote:
I believe this has been discussed elsewhere on the board.

Indeed

Oops.

[David Simmons]

On 2002-01-23 15:49, lpetrich wrote:
What was discovered was a whole ecosystem of microbes living in an underground hot spring; the primary producers are methanogens, which do not need to consume either light or organic compounds.

Instead, methanogens live of energy tapped from this reaction

CO2 + 4*H2 -> CH4 + 2*H2O

and use it in plantlike fashion to help build all the organic molecules that they need: nucleic acids, proteins, lipids, sugars, cofactors; the usual stuff.

Isaac Asimov discussed several possible chemical cycles for living things in his article Planets Have An Air About Them

[Joey Crow]

its impossible to live without it!

[kmarinas86]

On other worlds, can there be life that does not need H20? We don't know.

CO2 + 4*H2 -> CH4 + 2*H2O

Does this signal a possibility that H20 is not a presquite as a building block for life?

However, in either case... isn't an oxygen based compound needed?

[Glom]

CO2 + 4*H2 -> CH4 + 2*H2O

Isn't that reaction endothermic?

[kmarinas86]

CO2 + 4*H2 -> CH4 + 2*H2O

Isn't that reaction endothermic?

i dunno dood, i think you have it right. (does this mean that the reaction requires -delta G, free energy?)

Did the formation of the first DNA and protiens require free-energy? If so, where does this free energy come from?

[gritmonger]

I don't think they required "Free" energy- but energy is the primary resource in any ecosystem, that and a place to dump heat. A system at equilibrium can't really support life: there has to be an influx of energy into the system. In underground CO2/4*H2 to CH4/2*H20, the influx is heat energy which is stored in the chemical bonds of CH4, in a stable form that can be moved to a lower ambient energy system and do work. In the case of "methanogenic" bacteria, they are doing in one short step what plants do in several long steps: plants use photons to fuse CO2 and H2O to make carbohydrates as the building blocks of organic from inorganic molecules. Methanogenic bacteria do the same thing. It's a case of proton donors and acceptors, and for this purpose sulfer will do in the place of oxygen, along with a couple of other less efficient (but also less internally damaging) chemicals.

Solar energy, for instance : our model of the first "life" (replicating RNA chains, for instance...) can rely upon cycling hot-and-cold (similar to the PCR process that is used to "amplify" DNA for testing).

[Glom]

i dunno dood, i think you have it right. (does this mean that the reaction requires -delta G, free energy?)

We were never taught about Gibbs Free energy. It means that the enthalpy change is positive.

I remember doing a Hess cycle for the extraction of hydrogen from methane and it was exothermic.

[tuffel999]

You guys release that the only real purpose oxygen serves in bacteria is as an electron acceptor, the use of other elements is not new. Organisms that use Iron and Manganese as well as others have been described many times before.

The fact that an entire niche is based on this isn't surprising either, and I will look but I believe it has been described before in more scientific sources.