Biochar quiets microbes, including some plant pathogens

Rice University News: In the first study of its kind, Rice University scientists have used synthetic biology to study how a popular soil amendment called “biochar” can interfere with the chemical signals that some microbes use to communicate. The class of compounds studied includes those used by some plant pathogens to coordinate their attacks.

Biochar is charcoal that is produced — typically from waste wood, manure or leaves — for use as a soil additive. Studies have found biochar can improve both the nutrient- and water-holding properties of soil, but its popularity in recent years also owes to its ability to reduce greenhouse gases by storing carbon in soil, in some cases for many centuries.

The new study, published online this month in the journal Environmental Science and Technology, is the first to examine how biochar affects the chemical signaling that’s routinely used by soil microorganisms that interact with plants. “A potted plant may look tranquil, but there are actually a lot of conversations going on in that pot,” said study co-author Joff Silberg, associate professor of biochemistry and cell biology and of bioengineering at Rice. “In fact, there are so many different conversations going on in soil that it was impractical for us to determine exactly how biochar was affecting just one of them.”

So Silberg and colleagues used the tools of synthetic biology — and a refined experimental setup that Silberg initially drafted with his son’s spare Lego bricks — to establish a situation where just one microbial conversation was taking place and where biochar’s effects on that conversation could be measured.

The study is the latest from Rice’s interdisciplinary Biochar Research Group, which formed in the wake of Hurricane Ike in 2008 when the city of Houston called for ideas about how to get rid of the estimated 5.6 million cubic yards of fallen trees, broken branches and dead greenery left behind by the storm. The Rice Biochar Group won the $10,000 grand prize in the city’s “Recycle Ike” contest and used the money to jump-start a wide-ranging research program that has since received support from the National Science Foundation, the Department of Energy, Rice’s Faculty Initiative Fund, Rice’s Shell Center for Sustainability and Rice’s Institute of Bioscience and Bioengineering....

Rice University graduate student Shelly Hsiao-Ying Cheng shows the tool she created with Rice biochemist Joff Silberg to conduct two experiments in the same dish, one where biochar had a chance to interfere with a microbial conversation and another where it didn’t. CREDIT: Jeff Fitlow/Rice University