PNNL

The Science

Extreme environmental shifts, such as drying-rewetting cycles through drought, can impact microbial metabolism and ecosystem level processes. Microbial lipids, in particular, play a critical role in regulating microbial response to stress, but little is known about those found in soil and how they influence individual characteristics—or phenotypes—that microbes express during drying- rewetting cycles. The findings from this study suggest that lipids may be critical in orchestrating the broad differences in stress response strategies used by bacteria and fungi to survive environmental stress.

The Impact

This study revealed specific changes in lipids and metabolites that are indicative of stress adaptation, substrate use, and cellular recovery during soil drying and subsequent rewetting. These results underscore the importance of the soil lipidome—the collection of lipids—as a robust indicator of microbial community responses to short time scales (minutes) of cell-environment reactions.  

Summary

Drought is a drastic environmental change that affects soil microbes, which play important roles in biogeochemical cycling. Until now, however, little was known about specific physiological changes the microbes undergo during the rewetting that follows a period of drought.

Following a drought, the first three hours of rewetting brings with it a burst of respiration that is much higher than commonly observed basal levels. In this study, researchers simulated the simultaneous temperature and moisture stress of summer drought, followed by rewetting. They evaluated the collection of lipids and the polar metabolome—water-loving metabolites—of arid grassland soil.

Results revealed specific changes in lipids and metabolites that are indicative of stress adaptation, substrate use, and cellular recovery during soil drying and subsequent rewetting. Specifically, lipids and the polar metabolites indicated drought-induced nutrient limitations in dry soil and upon rewetting the rapid remodeling (within minutes) of the lipids suggested reactivation and growth in bacteria. Altogether, the study’s results demonstrate that lipids play an important role in how soil microbes respond to changes in the environment.

PNNL Contact

Kirsten S. Hofmockel, Pacific Northwest National Laboratory, kirsten.hofmockel@pnnl.gov

Funding

This program is supported by the Department of Energy, Office of Science, through the Genomic Science program, Biological and Environmental Research program, under FWP 70880. A portion of this work was performed in the Environmental Molecular Sciences Laboratory, DOE Office of Science at Pacific Northwest National Laboratory.