Kent Keller

PULLMAN, Wash.—Washington State University researchers have received half a million dollars to study a microscopic slime that they believe plays an outsized role in life on the planet.

The slime, also known as biofilm, forms a super-thin layer gluing the roots of plants to mineral surfaces and serves as a reactor in which a plant can break down the rock for vital nutrients. The process, says Kent Keller, was central to the start of land-based plant life as plants invaded the continents 350 million years ago. It continues to take place on modern volcanic ground and receding glaciers—anywhere a plant can’t get enough to eat.

 “The magic of all of this is plants come in that are adapted to make the slime,” says Keller, co-director of the Center for Environmental Research, Education, and Outreach (CEREO) and professor in the School of Earth and Environmental Sciences. “Within 100 years, you’ve got soil. That’s an amazing thing. And it’s these slimes that are a key part of the mechanism.”

Wait, there’s more: The biofilm reactor also facilitates the most fundamental process on the planet for packing away carbon, as seen in the greenhouse gas carbon dioxide. As the plant dissolves minerals, the plant’s natural carbonic acids, made from CO2 through photosynthesis, are transformed into bicarbonate that is carried in runoff to the oceans. There it precipitates as calcium carbonate.

In other words, the biofilm acts as an intermediary between carbon from the atmosphere and its storage in the earth’s crust. Absent that process, carbon dioxide would continue building up in the atmosphere until oxygen-dependent life forms suffocated in a “runaway greenhouse.”

“Without that we wouldn’t be here,” says Keller. “We’d be Venus, because Venus has no mechanism to sequester volcanic CO2.”

But there’s a mystery to the process, which Keller and a group of colleagues will explore with $492,000 from the National Science Foundation. Somehow plants employ biofilms to build up nutrients for plants to use while also releasing them for long-term storage, and they’ve done this in a way in which plants thrive and the chemistry of oceans and the atmosphere is kept in balance.

The researchers—a team of earth, life, and soil scientists—plan to grow trees in different nutrient conditions, including pure sand, to see which are best at inducing the formation of biofilm. One indicator of that will be microbial communities, which essentially generate the biofilms for shelter. The researchers hypothesize that plants in the worst conditions will be predisposed to hosting the most diverse microbial communities, the better to generate slime and nutrients.

One experiment will rely entirely on fertilized irrigation as a proxy for conventional agriculture, which is less reliant on large microbial communities for nutrients. Comparing this system with those generating their own nutrients could help open the door to agricultural systems that can use fewer artificial fertilizers.

In addition to Keller, the project’s other principle investigators are: Jim Harsh, Crop and Soil Sciences; Linda Thomashow, Plant Pathology; Rick Gill, Brigham Young University; and Zsuzsanna Balogh-Brunstad, Hartwick College. Collaborating with them are: Michael Knoblauch, School of Biological Sciences and Franchesci Microscopy and Imaging Center; Chongxuan Liu, Pacific Northwest National Laboratory; and Bernard Bormann, US Forest Service Pacific Northwest Laboratory in Corvallis, Ore.