The environment selects: Modeling energy allocation in microbial communities under dynamic environments

ABSTRACT What will be the best metabolic strategy in a competitive environment where oxygen is periodically unavailable? A few decades ago, an accidental, man-made cyclic anaerobic/aerobic environment selected for Polyphosphate Accumulating Organisms (PAOs) and this strategy is now widely used to allow for Enhanced Biological Phosphorus Removal (EBPR) of wastewater. But could it have been predicted? Here, a dynamic resource allocation modeling formalism was used to analyze the impact of selection pressures on metabolic function. With the same meta-network but modified selective pressures, different successful strategies can be predicted: Polyphosphate-AOs, Glycogen-AOs, Polyhydroxyalkanoate-AOs, and regular aerobic heterotrophs. The results demonstrate how storage metabolism allows for different trade-offs between growth yield, robustness, and competitiveness, and highlight how each metabolic function is an important determining factor for a selective advantage in a given environment. This can be seen as an example of when “Unity in biochemistry” by A.Kluyver meets “Everything is everywhere, but the environment selects” by B.Becking and how microbial ecosystems may be described by the energy allocation phenotype instead of a detailed description of each organism.