> Just curious, are there lifeforms today that rely on these metals to live in anaerobic environments? Maybe the hydrothermal vents that are talked about?

Yes! There are a few interesting variants called, "dissimilatory metal-reducing microorganisms"[1] and "sulfate-reducing microorganisms." They're a class that's being studied as a model for non-Terran life.

There are actually quite a few environments on Earth that are time capsules / have little ship bottles of very different life inside of them. For example, the Movile cave, https://en.wikipedia.org/wiki/Movile_Cave

    Life in the cave has been separated from the outside for the past 5.5 million years and it is based completely on chemosynthesis. Due to its extreme environment, access to Movile Cave is strictly controlled, and a limited number of researchers have permission to study its conditions.

It's my dream to find one of these sites. I think there are quite a few locations out there yet to be discovered.

[1] https://en.wikipedia.org/wiki/Dissimilatory_metal-reducing_m...

[2] https://en.wikipedia.org/wiki/Sulfate-reducing_microorganism

There could be deep subsurface microbes that are exposed to both pure metal and anoxic conditions that are similar, but note, it’s not “metal or protein” for catalysis. Many protein catalysts have metals incorporated.

What proto life did, it seems, was completely depend on metal surfaces to speed up some reactions. But that’s messy. The same metal can’t distinguish different components, so there would be competition for these surfaces, even within the same “cell”. That’s not ideal.

Enzymes are much more specific. You can actually sequester different reactions. And once you have life that’s learned to do that, it will out compete any proto life like matter that may access such environments.

Anaerobic microbes have enzymes also. So don’t think that reducing conditions mean no enzymes. It’s merely that in reduced conditions, you have metal that’s not oxidized available for early life -like goo to make use of. Over time, once this life learns to make newer and newer enzymes, the need to be metal dependent went away.

Somewhat separately, you also had some of this lineage learn to photosynthesize, and that lead to bulk oxygen in the atmosphere, and that was initially catastrophic, then highly beneficial because oxygen based chemistry is way more energetic than anaerobic chemistry.

It would be wrong to think of either condition as “better” though. They’re different. They force different tradeoffs. And both demand fine balance and dependence on the environment, eventually.