Using Multi-Omics and RTMS to Unravel the Microbiome Molecular Mechanisms of Carbon and Nutrient Cycling during Rewetting after Drought

Microbial response to changing environmental factors influence the fate of soil organic carbon and drought has been shown to affect microbial metabolism and respiration. We hypothesized that the access of microbes to different carbon pools in response to dry - rewet events occur sequentially at different rates.  We amended desiccated soils with 13C labeled glucose and measured the rates of 12CO2 and 13CO2 respiration in real time after rewet. Using these differentiated 12CO2 and 13CO2 respiration rates soils after rewet, we were able to deduce when microbes are accessing different pools of carbon. Immediately upon rewet, respiration of 12CO2 occurred first, with negligible 13CO2 respiration. Appreciable metabolism and respiration of the added 13C glucose did not occur until 15 minutes after rewet. We conclude that while all carbon pools are being accessed in the first 9 hours after rewet, the rate and timing that new and existing carbon pools are being accessed varies. Additionally, The metaphenome was evaluated by measuring metabolite, protein and transcript profiles through the dehydration and rewetting time course. We found that that soil microbial communities can quickly react to changes in soil moisture by shifting their metabolite compositions and this response is directly proportional to the length of drought exposure time. This may have important implications for carbon allocation within and between organisms and the soil environment.  Within this study, using stable isotope labeled substrates and multi-omics analysis to discern which carbon pools are metabolized first uniquely illustrates how microorganisms access different carbon pools which has implications into understanding how carbon metabolism can further affect climate, carbon sequestration, and soil health.