Collaborative Research: Do Expected Evolutionary Trade-Offs in Ezyme Activities Manifest at the Level of Microbial Community Function?

The question as to whether responses of soil microorganisms to environmental change translate to responses at the level of ecosystem processes has become a central theoretical question in ecosystem ecology. One reason for this is that if microbial responses are relevant to understanding ecosystem-level responses then understanding teh mechanisms might facilitate effective management of services ecosystems provide. The idea that microbial responses might translate to the ecosystem level is ingrained when it comes to ecosystem carbon dynamics through such phenomena as increases in heterotrophic soil respiration rates with short-term termperature rise. Uncertainty arises when considering whether changes in factors such as microbial community composition, and/or individual physiologies, might serve to modify the response to environmental changes of the process we measure at the ecosystem level. Yet there are a number of phenomena where a linkage between microbial community composition, microbial physiology, and an ecosystem-level process could be potentially important. At the physiological level, the most fundamental is the trade-off between the binding ability of an enzyme and its maximum catalytic rate. At higher temperatures enzymes need a more rigid structure to hold themselves in a binding state, but this rigidity comes at the cost of reducing their conformational flexibility and hence their maximum catalytic rate. Using observational and experimental approaches, the proposed work tests whether spatial and temporal variation in heterotrophic, soil respiration rates is explained, in part, by these fundamental, evolutionary trade-offs in enzyme structure and function.