Bacteria turn CO₂ into stone
At more than 470 times the atmospheric concentration of CO₂, a humble soil bacterium does something extraordinary: it turns gas into stone (Photo: EPFL)
July 8, 2025 – Researchers from EPFL’s Soil Mechanics Laboratory, the University of Applied Sciences and Arts of Southern Switzerland (SUPSI), and the EPFL spin-off Medusoil SA have demonstrated that Bacillus megaterium – a versatile microorganism commonly found in soil, freshwater, seawater, and even on plant surfaces – can convert CO₂ into calcium carbonate (CaCO₃), the mineral that forms limestone and marble. The findings were published in Scientific Reports.
What makes this study unique, according to EPFL, is not only the biological process itself but also the quality and origin of the resulting mineral. Under extremely high CO₂ concentrations – over 470 times higher than atmospheric levels – B. megaterium adjusted its metabolic strategy. Using the enzyme carbonic anhydrase, it converted CO₂ into bicarbonate, which then reacted with calcium ions to form solid calcite. Remarkably, 94 percent of the resulting mineral was derived directly from CO₂, rather than from nitrogen-based compounds such as urea.
