The latent simplicity of microbial ecological interactions

This is the authors' abstract. We don't add key points for this paper.

Microbial communities carry out functions of critical ecological, clinical and biotechnological significance. These functions arise from individual species contributions and from pairwise and higher-order interactions, whose number grows exponentially with community size. Despite this apparent complexity, community function is often surprisingly predictable. Here we show that this predictability does not require weak or sparse interactions. Instead, high-order interactions are strongly coordinated with pairwise interactions and additive effects, following simple linear laws. This coordination causes species effects in community function to vary together across community backgrounds, allowing function to be described by only one or two collective variables. We demonstrate this organization across dozens of combinatorial bacterial experiments and multiple environments. For total biomass, consumer–resource models and experiments identify the dominant collective variable with species yield, a trait that remains stable as abundances change through community dynamics. Microbial community functions are therefore predictable not because interactions are simple, but because their complexity is coherently organized. This provides a theoretical framework for understanding and ultimately designing community function.