Note: This is the second part of a question. The first part can be found here.

Incorporating some feedback from the answers I got to the question above, I have made a few changes.

Here is some background. So, 200 million years before the present day on my planet, a massive asteroid rich in indium and gallium hits my planet. Due to wind currents and stuff like that, the indium and gallium spread all over the planet. However, indium and gallium compounds are range from toxic to possible carcinogens and life starts to have problems.

However, an extremophile adapts to this problem and develops a symbiotic relationship with almost all life.

Basically here's what they do:

$$FeIn_2S_4 + enzyme \rightarrow In_2 + other \, stuff$$ $$CuGaS_2 + enzyme \rightarrow Ga + other \, stuff$$

Once they have the plain indium and gallium, they combine it with tin to create some sort of galinstan like alloy, which is then excreted. From my understanding, galinstan is totally non-toxic. However, it is synthetic. Would this work? If not, can you suggest other mechanisms?

Remember, since the gallium and indium arrived from an asteroid, it isn't enough to say that they will just adapt over billions of years. The organisms have to cope with the gallium and indium somehow.

  • 5
    $\begingroup$ Indium and gallium... "and iodine and thorium and thulium and thallium." $\endgroup$
    – A. R.
    Sep 12 at 15:46
  • $\begingroup$ You forgot nihonium. $\endgroup$
    – Neil Iyer
    Sep 13 at 14:29
  • 2
    $\begingroup$ Nihonium is one of the ones that had "still to be discahvahd" in 1959. $\endgroup$
    – A. R.
    Sep 13 at 14:43
  • $\begingroup$ @A.R. That sounds like some modern major general lyrics, yes? $\endgroup$
    – Qami
    Sep 15 at 13:32
  • 1
    $\begingroup$ @Qami It's Tom Lehrer, yes. I thought it a good coincidence that Neil stumbled across two consecutive elements in order, especially odd given that both alphabetically and by atomic number, gallium would come before indium. $\endgroup$
    – A. R.
    Sep 15 at 13:37

1 Answer 1


It is certainly possible for organisms to form symbiotic relationships with bacteria. It has happened a great many times, either intracellularly (most notably with mitochondria and chloroplasts), and many times extracellularly, with gut bacteria and others.

The part of this question that is difficult to answer is the energetics of the processes to extract Indium and Gallium from the compounds in which they occur. Certainly it does not matter that galinstan is synthetic, it only matters that it can be produced without too great a consumption of energy. However, if it is the case that it does require a significant energy input, there is a solution.

Having Copper, Indium and Gallium already present, all that is required is the addition of Selenium in order to produce a CIGS solar cell material, and if you have a symbiote that can deal in non-ionic metals, then it is not too great a stretch to suppose that it might be able to produce a tiny solar cell that it could use to power the conversion of the Indium and Gallium containing materials into either more solar cell material or inert galinstan for elimination.

While CIGS material is produced by humans at high temperatures, there is no reason why enzymes could not have evolved to produce this material at more reasonable temperatures.

So, if we had this symbiote with its CIGS-mediated photoelectric dissociation of indium and gallium from relevant compounds - and probably production of free energy, it would make sense for organisms to associate with it as a symbiote in order to reduce concentrations of toxic compounds.... either an endosymbiote or an exosymbiote, either way, as long as it was exposed to light.

This wouldn't be likely on Earth... but there is no reason why it couldn't work in another biome entirely.

  • 1
    $\begingroup$ That actually seems like a great idea. Using indium and gallium and selenium to make solar cells and excreting the rest is ingenious. $\endgroup$
    – Neil Iyer
    Sep 12 at 17:54
  • 1
    $\begingroup$ @NeilIyer I'm glad you liked it. It came up when I was searching Google for the energetics of breaking down gallium compounds, just add Selenium, which is a micronutrient in terrestrial organisms. $\endgroup$
    – Monty Wild
    Sep 13 at 0:56
  • $\begingroup$ How could I make sure then that the selenium isn't harming the organism (it's toxic)? $\endgroup$
    – Neil Iyer
    Sep 13 at 1:13
  • $\begingroup$ Considering that the symbiote can sequester the Selenium in its solar arrays, I doubt that it'll be a problem. $\endgroup$
    – Monty Wild
    Sep 13 at 1:15
  • 1
    $\begingroup$ @NeilIyer I would expect CIGS arrays to be part of the symbiotic bacterial cell, so that the cell can harness the electrical potential to produce energy carrying molecules, i.e. an ATP analogue. I wouldn't expect actual adenosine triphosphate. $\endgroup$
    – Monty Wild
    Sep 14 at 2:03

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