[notfed]

I think for the purpose of this topic, we only care about the nutrition (to use your word) question. We can assume humans can intelligently bootstrap past the other abiogenesis problems.

And surely this shouldn't be a difficult question to answer, right? Put an autotroph (the simplest that we know of) in a test tube and give it a ever-stricter diet and observe how far you can go without it dying off.

[throwawaymaths]

mimimal prototroph media is glucose, phosphate, ammonium, and trace metals that you just assume are in the water source. this is called m9 media. many known organisms can live on m9, including iirc bakers yeast and e coli.

if its fully autotrophic you dont need to add glucose. i think some forms of nocardia can live on m9 minus glucose.

of course anything that can live on m9 has way more genes in it just to biosynthesize the necessary amino acids and nucleic acids. That's why syn1 is a mycobacterium -- fewer genes because it has almost no metabolism. if you look at the biochemical pathways for mycobacterium its laughable how much is greyed out

[notfed]

What a great answer for a fascinating subject.