How plausible are my metal eating life forms and their impact on civilization?

Question

This question is a continuation of two prior ones.

1. How to render much of a world's metal unusable?
2. What minerals and metals in particular were vital to the development of early civilization?

The setting of my WIP is by no means Hard Science Fiction, it is Science-Fantasy I refuse to chose between the genre's that I love and sought to incorporate elements of both into my own work.

Because my world is fantastical I want it to have as few fridge logic invoking elements as possible. I don't want to break the audiences' "suspension of disbelief", so everything needs to flow together.

I ask is the following at least semi-plausible and what conceptual holes need to be plugged for it to work assuming that it could work at all.

After the development of higher life forms such as plants and animals, there was another great evolutionary leap forward. Some extremophiles began to leave their caustic pools for a much less hostile environment. These creatures were tenacious and complex, relying upon multiple vectors to attain the energy and raw material that they needed.

One linage evolved to become plant like,the botanicals, they absorbed minerals through a form of chemosynthesis and possessing a special apatite for the metals copper,tin,lead and iron, which were abundant in their birth region They also absorbed light and to a lesser extent heat, to among other things help process their metal diet into a pure state which was then used as both a skeleton and armor.

The other linage evolved to become animal like,the zoologicals, they were far more mobile than the botanicals but were but were less efficient at absorbing nutrients. So they began stealing what they needed from the the florals, the refined metals. This began an evolutionarily arms race between metal phages flora that wouldn't end until around the time that sapient races emerged. The botanical metal phages won the war through over kill, they began to produce a miasma that was powerful enough to kill anything around them, and worse this miasma would bond to pure metal(the very thing that florals bark/skin was composed of). Unable to feed the zoological linage of metal phages went extinct.

The Florals are immotile in their adult and form spread via their germ, which takes the form of airborne mites that would travel vast distance looking for rich metal deposits in which to germinate.

It is do to the evolution of a defensive miasma which the kills everything in its vicinity and contaminates pure metal. That early civilization was prevented from making a significant usage of metal and eventually lead to the development non metallic alternatives.

Answer 1

It doesn't appear too-crazy. There are metal-eating bacteria in the real world.

https://en.wikipedia.org/wiki/Microbial_corrosion

Though normally they use metals as a form of food, gaining energy from combining them with oxygen.

There are plants which take up and concentrate metals, though none to my knowledge that generate solid lumps of metal. You might have to hand-wave that a little.

http://www.livescience.com/28676-plants-grow-gold.html

Extremophiles can adapt to almost anything up to and including living inside running nuclear reactors.

I would guess that any creature trying to use metal armour would need to grow it bellow a thin layer of tissue to protect it from oxygen to avoid rust and growing it would be slow and energy-intensive.

The only thing that strikes me as absurd is your miasma being 100% effective. Nothing is every 100% effective on a large population. Organisms are really good at evolving to resist any poisons their food sources produce.

Your 2 species just sound like plants and herbivores to some extent with metal refinement thrown in. Plants evolved a huge array of poisons to defend themselves, grow thick hard costly layers of lignin and cellulose in part to defend themselves from herbivores but herbivores always evolved ways of dealing with defenses. Sometimes as simple as walking upwind while feeding.

Answer 2

1- The main problem with metal eating microbes is that most metals are already found in oxidized, low energy states. This means that you would have to transform low-energy compounds to even lower energy compounds in order to use them for food.

This means that if you eat iron oxide (rust) and convert it to pure iron, you would actually have to provide it energy instead of hoping to obtain any energy from it. However if you convert oxides into chlorides and chlorides into sulphates/flourides, you can obtain energy from the process.

However remember that you cannot obtain energy from converting oxidized metal compounds back into pure metal. Suggesting that would send waves of angry chemistry professors at your door.

2- The lethal miasma issue. While some metal compounds are extremely deadly, there is no compound which is equally deadly to all creatures.

Plus, even if you do have a highly lethal miasma, it automatically suggests it would be a reactive compound. Which means that if you leave it be, it will react with water vapor, oxygen, carbon dioxide or something else in the environment (specially in the soil) and become non-toxic. There is NO toxic compound which you cannot turn non-toxic by treating it with other chemicals.

3- A self sustainable cycle always involves recycling. If you have a process that only goes in one direction, there would be only so much time before the reactants finish and the process stops.

For example, in your scenario, you have plants processing metallic compounds into lethal, unusable compounds.

plants find metallic compounds and utilize them => plants proliferate and render more and more metal reserves unusable as their (plants) number grows => all metal reserves are soon rendered unusable and all plants die.

You see the problem with this scenario? There is no recycling involved. Incorporate it and your ecosystem would be more practical and believable.

Edit To Add

4- A very serious problem with your world would be that all complex life forms on Earth require some seriously large amounts of metals in their bodies. For example, take the case of chordates (backboned animals). All chordates require several grams of iron in their bodies for blood (haemoglobin). All chordates also require metals (calcium) for bones and teeth formation.

You cannot have complex life on your planet where metals are out of reach.