Some heavy metals share a long history with microbes. Many of the metabolic processes that sustain life are believed to have originated from spontaneous reactions involving metals present in the early Earth. Our microbial ancestors figured out quickly how to use those metal catalysts to generate energy and make cellular components. And so catalytic centers were incorporated into proteins to make a wide variety of metal-containing enzymes and diversify their activities. Some of those enzymes were passed down to us and have become integral to our functioning. They are the reason why we, like microbes, require some metals as micronutrients in our diet: zinc, copper, selenium, molybdenum, and cobalt (as vitamin B12).
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