Researchers discovered this by accident: when the bacteria left manganese oxide in a dirty lab jar:
Leadbetter knew that scientists had long suspected that bacteria could use manganese to fuel growth. Over a century ago, researchers discovered that bacteria could borrow electrons from chemical elements like nitrogen, sulfur, iron — and manganese. In some cases, bacteria could even use these electrons to fuel growth in much the same way that humans use electrons from carbohydrates in the diet for energy. But no one had identified bacteria that could turn electrons from manganese into energy…
Leadbetter suspects that similar bacteria may also be responsible for grapefruit-sized balls of manganese oxide on the ocean floor, first spotted in the 1870s, that have puzzled scientists. He wants to search there and other places for more examples of bacteria that use manganese for energy.
Carolyn Beans, “Scientists stumbled across the first known manganese-fueled bacteria” at ScienceNews
Paper. (open access)
One wonders, is there any natural element that no life form uses?