Are there bacteria or other types of lifeforms that feed on rocks and other ground minerals? And if there aren't, is it technically possible? It can eat other things but the majority of its diet should be rocks or ground minerals.
Lithotrophs are a diverse group of organisms using inorganic substrate (usually of mineral origin) to obtain reducing equivalents for use in biosynthesis (e.g., carbon dioxide fixation) or energy conservation (i.e., ATP production) via aerobic or anaerobic respiration." - Wikipedia
My understanding of inorganic substrate of mineral origin is that it uses rock and/or minerals as a source of food, however small those meals might be
I should preface by stating I am a geobiochemist with a focus on ferrolithotophic bacteria, or bacteria that gain their energy from rocks and minerals that contain iron with ‘extra’ electrons. While it is colloquially stated that these organisms ‘eat’ rocks and minerals, they are only able to derive energy from this process, and must obtain carbon for biomass from additional sources, often carbon dioxide. In this way it is analogous to plants growing using sunlight, but in the stead of light, these organisms alter rocks.
Specifics and nerdiness aside, the answer is yes; it is possible. It is suspected the majority of organisms on Earth ‘eat’ rocks and minerals for a living, and this likely constitutes the majority of their energy intake. Bacteria (and Archaea) are commonly able to ‘eat’ minerals containing sulfur, iron, nitrogen, hydrogen of specific types. Less common examples have been found to ‘eat’ uranium, arsenic, and mercury. As an interesting aside, many of these minerals can be breathed as well. No known macroscopic organisms are known to do this (i.e. animals, lichen.. etc..)