Stability of multi-species consortia during microbial metabolic evolution

Explaining multi-genic adaptations is a major objective of evolutionary theory. Metabolic pathways require multiple functional enzymes to generate a phenotype, and their evolution in microbes remains underexplored. In particular, sites polluted with manmade chemicals or “xenobiotics”, like plastic or pesticides, provide evidence for the rapid adaptation of novel metabolic pathways in microbes, which degrade these xenobiotics into utilizable nutrients. Decades of microbiological studies revealed that these pathways often are not consolidated within a single microbial species, but are rather distributed across several different ones, which cooperatively degrade xenobiotics. These species form remarkably stable consortia in the laboratory, but the determinants of this stability have not been hereto addressed. In this study, we show that trade-offs in microbial life history explain stable co-existence in a mathematical model of a three-species consortium, growing on a xenobiotic as the sole source of a limiting nutrient. Stability is predicted to hinge on a specific “ecological matching” between a species’ metabolic role in the novel metabolic pathway and its nutrient utilization strategy.