Unraveling the Molecular Mechanisms Underlying the Soil Microbiome Response to Soil Moisture
Abstract
Soil microorganisms are highly sensitive to changes in their environment, and rapidly measuring their physiological responses is necessary to fully understand the biological processes that they mediate. Drought is an increasing relevant environmental stress that soil microbiomes experience and understanding the mechanisms by which the soil microbiome responds to soil dehydration is vital. Here, we used 13C as a tracer of nutrient fluxes through microbiomes in desiccated soil after rewetting by measuring aerobic respiration using Real Time Mass Spectrometry (RTMS) and tracking the metabolic fate of the substrate using Isotope Ratio Mass Spectrometry.
The molecular mechanism(s) underlying the rapid mineralization of soil organic matter and increased rate of CO2 release upon rewetting dry soil (termed the `Birch Effect') are yet to be fully defined. One known microbial mechanism to protect against dehydration is the production of intracellular compounds known as osmolytes. We hypothesize that the rapid release of CO2 arises from the microbial processing of these intracellular compounds rather than extracellular carbon. RTMS allows for the simultaneous, highly temporally resolved (every 2 sec) evaluation of the production and consumption of multiple gasses including 12CO2,13CO2, O2, N2 and H2O. We compared the hydration response (real time CO2 production) between water and 13C labeled glucose dissolved in water amendments. The initial burst of 12CO2 (5 min) followed by a leveling off was identical in both treatments. An increase in 13CO2 production was observed later (2-4 h) in the 13C glucose experiment. When solid phase 13C glucose was amended to the soils, the 13CO2 production delay was much longer, potentially indicating that the solubilization rate is important to the respiration process. By contrast, amending the soil with 13C labeled alanine, either in solution or solid phase, produced negligible amounts of 13CO2, potentially indicating usage of the amino acid is not being used for energy production and respiration, but diverted to another pathway. We are currently exploring this divergence between substrates using IRMS to track the ultimate fate of the 13C label. Together these results demonstrate the importance of substrate form in regulating metabolic pathways that contribute to soil respiration.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2020
- Bibcode:
- 2020AGUFMB094.0015L
- Keywords:
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- 0402 Agricultural systems;
- BIOGEOSCIENCES;
- 0414 Biogeochemical cycles;
- processes;
- and modeling;
- BIOGEOSCIENCES;
- 0428 Carbon cycling;
- BIOGEOSCIENCES;
- 0486 Soils/pedology;
- BIOGEOSCIENCES