“Sensitivity of soil microbial volatile organic compound metabolism to drought and rewet”

Soil microbes cycle volatile organic compounds (VOCs) as metabolites and signaling molecules, and VOCs represent the volatile portion of their metabolome coined the ‘volatilome’. Soil sources and sinks of VOCs contribute to ecosystem-scale interactions with the atmosphere where VOCs influence air quality and cloud formation. Identifying microbial VOC pathways and their behavior in the environment is foundational to understanding and predicting soil VOC fluxes, including their responses to environmental drivers such as drought. 

To explore the sensitivity of microbial soil VOC metabolism to drought, we conducted an ecosystem-scale drought in the tropical rainforest biome at the University of Arizona Biosphere 2 during the 5-month Water, Atmosphere, and Life Dynamics (WALD) campaign. Within the context of this campaign, we designed experiments to quantify soil VOC fluxes via autochambers and subsurface soil VOC concentrations using our recently developed non-invasive, online soil gas sampling approach. Moreover, to identify the up- and down-regulation of microbial VOC cycling, we used a combination of 13C stable isotope labeling and ‘omics approaches that characterize the gene content (metagenomes), gene expression (metatranscriptomes), and organic matter composition (metabolomics) of soil. 

We observed dynamic and diverse patterns in soil VOC fluxes in response to drought and rewet. Soil microbes consumed atmospheric isoprene and monoterpenes. Other VOCs exhibited a strong flux enhancement in response to rewetting, including both increased emissions (e.g., dimethyl sulfide) and uptake (e.g. acetone). Stable isotope labeling revealed surprising up-regulation of VOC-producing fermentation pathways during drought. With the ongoing integrative analysis of these data, we aim to contribute to the growing understanding of microbial VOC pathways in soil and their sensitivity to shifts in ecosystem moisture conditions.

 Bio

Dr. Laura Meredith, is an assistant professor at the University of Arizona BIO5 Institute and School of Natural Resources and the Environment. She leads a research team that focuses on resolving gene to function links in microbial trace gas metabolism, developing improved methods for sensing trace gas signals in the soil, and scaling microbial processes driving biosphere-atmosphere trace gas exchange.

Dr. Meredith received her PhD from the Massachusetts Institute of Technology Program on Oceans, Atmospheres, and Climate. She was awarded the Carl-Gustaf Rossby Prize for her dissertation work that pioneered measurements of biosphere-atmosphere H2 exchange, leading to new constraints on microbial drivers of the overwhelming H2 soil sink. She was awarded a NSF Postdoctoral Research Fellowship in 2013 to work at Stanford University to resolve genomic underpinnings of the microbial capacity to drive soil-atmosphere exchange of atmospheric carbonyl sulfide (OCS) and CO2 oxygen isotopes—two promising carbon cycle tracers. In 2015, she joined the University of Arizona, as a postdoc to study shifts in soil microbial CH4 cycling to land use in the Brazilian Amazon using stable isotopes. In 2017, she joined the faculty of the University of Arizona as an Assistant Professor of Ecosystem Genomics and Director of Rainforest Research at Biosphere 2. 

Dr. Meredith received the NSF CAREER award in 2021 and has been awarded grants from NSF Atmospheric Chemistry, NSF Signals in the Soil, and DOE Biological and Environmental Research programs. In 2019-2020, she co-led the Water, Atmosphere, and Life Dynamics Campaign (WALD), a controlled whole-ecosystem drought and rewet campaign in the Tropical Rainforest biome at Biosphere 2 that involved ecosystem-scale isotope labeling. Dr. Meredith’s work has been recognized by various media outlets including Science Magazine, NPR Science Friday, BBC and others. 

Websites:

https://www.laurameredith.com/

Twitter: @DrLauraMeredith

Next week we will end the spring seminar series  with a VIRTUAL seminar format. Please join us Thursday for our Spring Seminar Series with our guest speaker Laura Meredith, Ph.D. A special thanks to Professor Paula Welander for bringing this speaker to us for this seminar. Also, thanks to Professor Morgan O’Neill & Professor Jamie Jones for co-instructing and running this Seminar Series this Spring by bringing you experts in the fields as we learn from them.