These bacteria perform a trick that could keep plants healthy

Written by
Molly Sharlach
Molly Sharlach, School of Engineering and Applied Science
Jan. 2, 2025

To stay healthy, plants balance the energy they put into growing with the amount they use to defend against harmful bacteria. The mechanisms behind this equilibrium have largely remained mysterious.

Now, engineers at Princeton have found an answer in an unexpected place: the harmless, or sometimes beneficial, bacteria that cluster around plants’ roots.

In an article published Dec. 24 in the journal Cell Reports, researchers showed that some types of soil bacteria can influence a plant’s balance of growth and defense. The bacteria produce an enzyme that can lower a plant’s immune activity and allow its roots to grow longer than they would otherwise.

“This is trying to get at a really big biological question where there are not good answers — about how microbiomes interface with host immune systems,” said senior study author Jonathan Conway, an assistant professor of chemical and biological engineering. “It’s a small step in the direction of trying to understand how microbes live on hosts — either plants or humans or other animals — all the time and don’t activate our immune responses constantly.”

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