Scientists have accidentally discovered bacteria that eat and take calories from metal, although they suspect they have existed for more than a hundred years, but simply could not prove their existence.
Microbiologists from the California Institute of Technology accidentally discovered the bacteria while conducting experiments using a type of manganese (chemical element, metal) in the form of chalk. Dr. Jared Leadbetter, professor of environmental microbiology, left a glass jar with the substance submerged in tap water from the office sink. He left the jar in the office for several months after going to work off-campus. When he returned, he found the jar with a dark material.

"I told myself what it would be like," Leadbetter said in a press release. The researchers found that the black coating found in the jar was oxidized manganese which was generated by bacteria that have been present in tap water.
In research published in the journal Nature, scientists note that these are the first bacteria to use manganese as an energy source. The new study also reveals that bacteria can use manganese for a process called chemosynthesis, which converts carbon dioxide into biomass.
Scientists believe the findings will help them better understand groundwater.
Source: CNN