[dayglored]

> There are bacteria on Earth that live deep underground that oxidize iron instead of oxygen.

Whatever you were trying to convey in that sentence, it came out wrong. In particular the "oxidize iron instead of oxygen" part.

[E. Pluribus Unum]

Whatever. Just ignore the obvious meaning and nitpick.

What is the word that describes the process?

PS - Rust is oxidized iron.

[Svartalfiar]

Whatever you were trying to convey in that sentence, it came out wrong. In particular the "oxidize iron instead of oxygen" part.

Oxidization means gaining an oxygen atom. Oxidation is the chemical process by which electrons are lost, and does not require oxygen. It was just named such because way back when, scientists only knew about oxygen forcing this process mainly. Unfortunately, the name stuck even after it was realized other atoms do it too, especially fluorine, or in this case, accomplished by iron.