The temperature response of fungal enzyme kinetics

Extracellular enzymes produced and excreted by microbes mediate the decomposition of carbon (C), nitrogen (N), and phosphorus (P) -containing compounds in their environment. Climate change has the potential to alter the rate of decomposition especially in high latitude regions where stocks of recalcitrant, or long-lived, C are abundant. This project compares extracellular enzyme activity (EEA) across ten fungi strains within the model family Neurospora in order to assess the range of variation in temperature sensitivities of fungal enzyme Vmax and Km. Vmax values of most enzymes tested increased exponentially,which was hypothesized and consistant with thermodynamic principles. We also hypothesized that Neurospora strains would exhibit different EEA temperature sensitivities based on their native climate. We observed strain-dependent variation in enzyme temperature responses consistent with strain-specific adaptation to local conditions. Since fungi are the major decomposers of organic carbon in high-latitude ecosystems, an increase in EEA in-situ would result in higher carbon dioxide emissions. These findings suggest a shift in fungal processing of soil organic carbon and nutrients in response to changing climate.