Weathering rocks naturally pull carbon dioxide from the atmosphere, but the process is too slow to make much of a dent in human emissions of the greenhouse gas. Even olivine, which is considered a relatively fast-weathering silicate, dissolves at rates on the order of just micrometers per year.
Researchers have now engineered marine bacteria to keep producing siderophores, molecules that microbes use to scavenge iron from their surroundings, even when iron is abundant, speeding up the dissolution of olivine. The study describes how the engineered bacteria accelerate olivine weathering in seawater reactors and increase the water’s alkalinity, allowing it to absorb more CO2 from the atmosphere (Nat. Biotechnol. 2026, DOI: 10.1038/s41587-026-03288-w).
“These rocks rust almost immediately,” says Neil Dalvie, a Harvard Medical School chemical engineer and the study’s first author. As olivine dissolves, it releases Fe(II), which oxidizes to Fe(III) in oxygenated water. Iron oxides then precipitate onto the mineral surface, inhibiting further dissolution of the rocks, but siderophores can bind Fe(III), keeping the iron soluble and helping prevent the buildup.
Researchers engineered Alteromonas macleodii bacteria to boost production of siderophores, which clear rust from olivine and lead it to continue dissolving. Credit:
Hansjörg Wyss Institute for Biologically Inspired Engineering at Harvard University
The researchers used the marine bacterium Alteromonas macleodii, which is abundant in seawater and naturally produces the siderophore petrobactin. But bacteria typically make siderophores only when iron is scarce, which is not the case inside a reactor packed with iron-containing olivine. Dalvie and the team genetically engineered the microbes to continuously produce petrobactin, which increased olivine dissolution 2.6-fold in small seawater reactors compared with an abiotic control.
The researchers then scaled the system to reactors containing more than 4 kg of construction-grade olivine and unprocessed seawater from Boston Harbor. They found that the engineered bacteria increased magnesium release, a measure of olivine dissolution, by a factor of 3.1 compared with the control. The additional alkalinity generated was equivalent to removing about 0.5 g of atmospheric CO2 per day.
The researchers envision eventually flowing seawater through large reactors containing crushed rock and engineered microbes, then returning the alkaline water to the ocean. But further work is needed: after several weeks, biofilms and a hardened mineral crust accumulated on the olivine, potentially creating new barriers to weathering.
Dalvie says the work grew out of combining ideas from geochemistry, microbiology, and chemical engineering, fields that approach the same process at different scales. “A lot of what we’ve uncovered is just from taking perspectives and fields that don’t talk to each other and putting them together,” he says.
Ana Georgescu covers a wide range of topics in Physical Sciences. She is also a frequent contributor to the Business desk and is probably working on a short video project at any given time.
