[meepmorp]

> IIUC most of the mass required to build plants comes out of the air (CO2).

Fungi aren't plants, though.

edit: they're heterotrophs - they get their food from more complex materials than autotrophs, which generate their raw material largely from carbon extracted from the atmosphere.

[littlestymaar]

> edit: they're heterotrophs

Except not these ones! These are autotrophs fungi, they do some kind of photosynthesis (it's absolutely not the same metabolic path, though) gaining their energy from gamma rays instead of food.

Edit: The above comment is wrong, I though autotroph vs heterotroph was about energy input (as a matter of fact I'm very convinced it was how my college teacher explained it) but from wikipedia it looks like I'm wrong, and such fungi would be classified as Photoheterotroph[1]

[1]: https://en.wikipedia.org/wiki/Photoheterotroph

[meepmorp]

Yes, but they're still fungi. They might be extracting some amount of energy from radiation, but they still get most of their energy (and cellular raw material) the old fashioned, biological way. It's not like they suddenly evolved replacement pathways to synthesize all the products they need.

[samus]

For fungi, the carbon source is actually even more straightforward than with plants: we can just feed them biowaste. Depends on the species of course, and probably requires some treatment to not encourage growth of less desirable species instead. If they turn out to be edible, this could prove to be ideal.

[account-5]

Don't fungi "breath" out CO2 as well, I think I remember reading that somewhere. That might be an issue in space.