‘Iron Microbes’ Confirm Vernadsky’s View of the Ubiquity of Life

A recent article in the Proceedings of the National Academy of Sciences reveals the activity of living microbes in the darndest of places. A study by Clark Johnson, a professor of geosciences at the University of Wisconsin, and Li Weiqiang, now at Nanjing University, reports the discovery of microbes in the formation of iron deposits 2.5 billion years old, found at a depth of 150 meters in a mine in Australia. Advances in laser technology and spectrometry at the University of Wisconsin have permitted more advanced isotope measurement of the finds, which have indicated the existence of microbes in the formation of the iron, something that was totally unexpected. Bursts of light less than one-trillionth of a second long vaporized thin sections of the sample without heating the sample itself. “It’s like taking an ice cream scoop and quickly pulling out material before it gets heated,” Johnson explains. “Heating with traditional lasers gave spurious results,” he said. Johnson and Li show by their results that half of the iron in the banded iron was metabolized by ancient bacteria living along the continental shelves!

The idea that an organism could metabolize iron may seem strange today, but Earth was very different 2.5 billion years ago, the study continues. With little oxygen in the atmosphere, many organisms derived energy by metabolizing iron instead of oxygen. Biologists say this process “is really deep in the tree of life, but we’ve had little evidence from the rock record until now,” Johnson says. “These ancient microbes were respiring iron just like we respire oxygen. It’s a hard thing to wrap your head around, I admit.” The research also clarifies the evolution of our planet and of life itself during the “iron-rich” era 2.5 billion years ago. “What vestiges of the iron-rich world remain in our metabolism?” Johnson asks. “It’s no accident that iron is an important part of life, that early biological molecules may have been iron-based.”

While Vernadsky created, almost a century ago, the study of biogeochemistry, stressing the all-important function of life in the formation of Earth’s geology, this revolutionary idea has largely remained foreign to the teaching of the universities, as Johnson himself admits. “In my introductory geochemistry textbook from 1980,” Johnson said, “there is no mention of biology, and so every diagram showing what minerals are stable at what conditions on the surface of the Earth is absolutely wrong.” Research results like these affect how classes are taught, Johnson says. “If I only taught the same thing, I would be teaching things that are absolutely wrong. If you ever wonder why we combine teaching and research at this university, geomicrobiology gives you the answer. It has completely turned geoscience on its ear.”