Community metabolism in dynamic redox landscapes.

Microbial communities are fundamentally shaped by the diverse metabolic processes through which microbes extract energy from the chemical and light-driven potential gradients in their environment. Thus, predicting microbial community dynamics requires a quantitative framework grounded in bioenergetics and accounting for the key factors influencing metabolite concentrations in microbes' local environment. Here, we present a perspective based on three tightly coupled factors governing microbial community metabolism: (i) the thermodynamics of redox reactions, that is, the redox tower, as a universal constraint on energy yield and reaction feasibility; (ii) external environmental and host-driven factors that set the availability of key metabolites that can act as electron donors and acceptors; and (iii) intracommunity cellular responses that alter metabolic outputs and feedback with local conditions. We emphasise that all three factors have to be integrated and considering any one without the others will only provide limited insights into community metabolisms. This integrative view needs to be incorporated into tightly coupled experiments and modelling to enable a mechanistic understanding of microbial community metabolism across environments.