First Cell Nutrition

[DavidJames]

Is there a well versed researcher here that can explain if there is any known living organism that consumes inorganic material as its only source of nutrition in today's world. I've heard it said that inorganic material had to be the only likely source of nutrition available to the first living cell, eons ago.

 

Following are two answers I received from another part of SF. Can anyone add to it or comment on the answers?:

 

Thanks, David James

 

Chemoautotrophs (or chemotrophic autotroph), (Gr: Chemo (χημία) = chemical, auto (αὐτός) = self, troph (τροφιά) = nourishment) in addition to deriving energy from chemical reactions, synthesize all necessary organic compounds from carbon dioxide. Chemoautotrophs use inorganic energy sources, such as hydrogen sulfide, elemental sulfur, ferrous iron, molecular hydrogen, and ammonia. Most are bacteria or archaea that live in hostile environments such as deep sea vents and are the primary producers in such ecosystems. Evolutionary scientists believe that the first organisms to inhabit Earth were chemoautotrophs that produced oxygen as a by-product and later evolved into both aerobic, animal-like organisms and photosynthetic, plant-like organisms.[citation needed] Chemoautotrophs generally fall into several groups: methanogens, halophiles, sulfur oxidizers and reducers, nitrifiers, anammox bacteria, and thermoacidophiles.

 

http://en.wikipedia....wiki/Chemotroph

 

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#3 Today, 02:36 AM LawfulBlade

 

Quark DavidJames, on 22 September 2011 - 10:50 PM, said:

 

If by only source of nutrition, you mean that they have no source of carbon, then, no, that doesn't exist. All living things require carbon in their diets, as they, their proteins that they create, and all of their offspring, will be carbon-based as well.

 

Many things (collectively called lithotrophs) can readily consume inorganic compounds, however, and some extremophiles can only live in inorganic evironments, like the boiling sulfur springs at Yellowstone. One such thing, an archaea called Thermus aquaticus, has attained fame as being the creator of an enzyme used in pcr, so you may already be familiar with them.

 

Not sure if you've done this, but I think this question will gather more answers if you repost it in the biology section. Microbiologists work a lot with archaea, and they're of interest to geneticists as well, as well as anyone using pcr.

 

Thank you

 

[quote)

[CharonY]

The answers as well as the question mix up two distinct elements. The first is nutrition uptake, e.g. the material required to generate biomass. This is what you would generally understand if you talk about consumption. The ability to rely purely on inorganic substances is called autotrophy. The inorganic source for carbon is, as shown in the first part of the OP, obtained by CO2 fixation.

 

However, CO2 fixation requires energy. And here is the second part, some organisms can also rely on inorganic sources for energy production. The one you have heard most about is most likely photosynthesis (where the light reaction provides energy, whereas the CO2 fixation is light independent).

 

In general most respiration (the mechanism that creates energy) requires reductions equivalents that are shuffled through a membrane system to create a proton gradient, which in turn, is used by an ATP synthetase to create energy (I will leave out fermentation here).

Thus you essentially need an electron donor and and acceptor for the respiratory chain to work. If the donor is inorganic, (an example is e.g. oxidation of ammonia to nitrite) then it is referred to as lithotrophic. Note that in this case the inorganic substance is used as an electron donor, but is usually not consumed (i.e. internalized to build biomass) and can also (of course) not serve as a carbon source.

[supersapien]

Can I say Pseudomonas, I'm not sure though. It think it is not exclusively on inorganic substances.

[ewmon]

Is there a well versed researcher here that can explain if there is any known living organism that consumes inorganic material as its only source of nutrition in today's world.

Isn't the answer quite obvious — DNA, RNA and amino acids contain/require carbon, thus organisms at any point in history require an external source of carbon. Even viruses and prions must contain/obtain carbon.

Edited October 2, 2011 by ewmon

[CharonY]

Yes, but the carbon source can be inorganic. I.e. CO2.