It doesn’t have much to do with backyard forest restoration, but I want to share something I learned about soil, simply because it surprised and amazed me. In one of her last blogs for the Artful Ameoba, Jennifer Frazer wrote about microbial bacteria that help create soil by eating solid rock. Yes, microbes that eat rocks! I had no idea, not only that such life exists, but that scientists have learned so much about it.
Lithotrophs
The formation of soil begins with various “weathering” processes that break down bedrock into small mineral particles. One of these processes involves microbes called lithotrophs (from the Greek rock + consumer) which get the energy they need to live by harvesting electrons from minerals. This process was not proven experimentally until some scientists added lithotrophic bacteria to crushed rocks and waited 30 months. Evidence that the bacteria had been consuming the rock included photos from an electron microscope showing pitted surfaces of the minerals and lots of Adenosine Triphosphate (ATP), a chemical that apparently only comes from metabolizing cells.
No Reliance on Sunlight
Many different types of lithotrophs are found both in topsoil and subsoils, and some are even found at the very bottom of soil profiles next to underlying bedrock. Like some of the microbes in deep-ocean hydrothermal vents, lithotrophs can live in environments where there is no sunlight. Unlike fungi, they don’t require inputs of organic matter from plants, but they help support plant life by contributing “significantly to carbon and nitrogen cycles in soils.”
Capturing Electrons Outside Their Bodies
Lithotrophs can consume many different minerals, but iron is popular because its electrons are easy to catch. They actually capture the electrons outside their bodies, like reaching out a virtual arm and snagging a fly ball! I’ll end by stealing another idea from Jennifer Frazer’s blog — if the microbes had to actually swallow the iron molecules, they might rust!