Soil microbes play an important role in soil fertility, plant growth, and carbon storage, but these tiny organisms are vulnerable to drought. Microbes can’t pack their bags to improve their environmental conditions, but they have developed various approaches to deal with this environmental stress. Some organisms produce compounds to help ease the stress caused by drought, while others go into a dormant state and wait until conditions improve.
Despite the research community’s best efforts, past studies on soil microbes have been limited by the destructive nature of most experiments and the limited quantitative information from most methods. As a result, researchers have been prevented from comparing how the same cell reacts when exposed to differing conditions to understand how the organism changes over time. A new study overcomes these limitations to clarify the role of microbes in the environment.
“We sought to understand how organisms respond to drought, and whether that drought response is shaped by their evolutionary history or local adaptation,” said Nicholas Bouskill, associate professor at Oregon State University and first author on the study.
Bouskill and his team collected soil-dwelling microbes from two locations—a humid tropical forest in Panama and a dry, high-elevation plateau in Colorado. They isolated and selected eight bacteria that included two organisms—one from the tropical forest soil and one from the semi-arid soil—of four common microbial groups: Actinobacteria, Bacilli, Enterobacter, and Sphingomonas.
At the Advanced Light Source (ALS) at Berkeley Lab, the research team used infrared spectroscopy at Beamline 1.4 to monitor the same microbial cells in a non-destructive manner. During the experiments, the team tracked the detailed changes in the cell’s biochemistry under different conditions. This approach allowed them to witness how microbes respond to changing environmental conditions in real time.
The team anticipated changes in osmolytes, compounds that help cells manage water stress, but they also observed shifts in signaling molecules and energy storage compounds. These results provide a more complete picture of how microbes adapt to water stress.
Bouskill believes this work provides a deeper insight into how organisms adapt to water stress and shape how these organisms evolved. This information can help scientists understand how different ecosystems might respond to changing environmental conditions, especially as it relates to questions of nutrient cycling, plant growth, and soil carbon storage.
“Thanks to the advanced tools at the ALS, we could watch these changes happen in real time, without harming the microbes,” said Bouskill. “That’s a big deal—it gives scientists a clearer window into how life responds to stress.”
This research also opens up new possibilities for harnessing microbes to improve soil health in dry regions that can guide better land management practices, inform conservation efforts, and even help develop drought-resistant agriculture.
N.J. Bouskill, S.S. Chacon, D.F. Cusack, L.H. Dietterich, L. Chen, A. Khurram, J. Voříšková, H.N. Holman, “Climate history modulates stress responses of common soil bacteria under experimental drought,” The ISME Journal, 19, 1, doi.org/10.1093/ismejo/wraf075.