Israeli Scientists Find Bacteria That Can Help Trees Survive Drought

(l-r) Dr. Tamir Klein and Dr. Yaara Oppenheimer (Weizmann Institute of Science)

Israeli scientists may very well be on the cusp of finding a new way to help deal with the growing problems of drought caused by climate change. Dr. Tamir Klein and Dr. Yaara Oppenheimer-Shaanan from the Weizmann Institute of Science researched the resilience of cypress trees in drought conditions and found that a strain of bacteria could actually help.

The scientists found that cypresses get help from soil-beneficial bacteria in a kind of cooperation that enables them to survive and even flourish. They said their research helps to better understand how the underground mechanisms keep trees alive in extreme weather. This, they say, will help find a way to mitigate the rising mortality of trees in Israel and beyond.

The world is getting hotter. July has already set a number of world records and an ongoing heatwave has yet to break.

“Our study might have supplied the best evidence so far that trees and bacteria can really coexist symbiotically,” says Dr. Tamir Klein, head of the research team. “This has huge ecological significance.”

For one month the researchers grew cypress saplings in custom-made boxes filled with forest soil, which were placed in a greenhouse at the Weizmann Institute of Science. The cypresses were divided into two groups: one was regularly watered, and the other was deprived of water. In each group, half of the cypresses were exposed to soil bacteria that had been collected from the Harel Forest, where these cypresses grow.

The research team examined the interactions between the trees’ roots and the bacteria using several methods, including measuring physiological reactions of the trees to dryness, performing bacterial counts, imaging the bacterial colonies in the root zones using fluorescent markers, analyzing the compounds emitted by the seedlings through their roots and assessing the mineral composition of the cypress foliage. Through this multidisciplinary approach, which combines microbiology, plant physiology and organic chemistry, the researchers identified what they described as a surprising cooperation happening underground between trees and soil bacteria: The bacteria help the trees cope with the shortage of water and in return, benefit from the secretions from tree roots.

“When we added nine of the compounds to the bacteria, as sources of carbon and nitrogen, eight of them encouraged bacterial growth,” Oppenheimer-Shaanan says. “This is evidence that the secretions are a source of food for the bacteria.”

“The next step is to determine the exact contribution of each bacterium or each group of bacteria, and which bacteria benefit which trees,” says Oppenheimer-Shaanan.

“This is only the beginning,” says Klein. “The more we learn about these interactions, the more we will be able to formulate a comprehensive and accurate dictionary, and this should allow us to arrive at desired results, or prevent unwanted ones, in taking care of our forests.”