FIGURE 4.

Theoretical framework and hypotheses. In this figure, we demonstrate how the Arrhenius and MMRT frameworks fit together conceptually and how that impacts our view of the temperature response, which in our case refers to the reaction rate of extracellular enzymes. Under the Arrhenius framework, activation energy is the singular factor driving the apparent temperature response. MMRT expands upon this framework, suggesting that the temperature response is a function of the heat capacity of an enzyme, which is related to the enzyme’s flexibility. While there is already evidence for substrate type influencing activation energy (solid arrow connecting substrate to activation energy), in this experiment (red lettering) we extend this framework and hypothesize that the enzyme flexibility is also a product of the substrate type and genetic variation among different enzymes (dashed arrows). We posit that this overarching framework could be applied in a variety of situations relating to the temperature response.