Kehila, D. | Search bioRxiv

bioRxiv2025

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.

evolutionary biology↗

bioRxiv2023

Neutral Drift and Threshold Selection Promote Phenotypic Variation

Phenotypic variations within a population exist on different scales of biological organization and play a central role in evolution by providing adaptive capacity at the population-level. Thus, the question of how evolution generates phenotypic variation within an evolving population is fundamental in evolutionary biology. Here we address this question by performing experimental evolution of an antibiotic resistance gene, VIM-2 {beta}-lactamase, combined with diverse biochemical assays and population genetics. We found that neutral drift, i.e., evolution under a static environment, with a low antibiotic concentration can promote and maintain significant phenotypic variation within the population with >100-fold differences in resistance strength. We developed a model based on the phenotype-environment-fitness landscape generated with >5,000 VIM-2 variants, and demonstrated that the combination of "mutation-selection balance" and "threshold-like fitness-phenotype relationship" is sufficient to explain the generation of large phenotypic variation within the evolving population. Importantly, high-resistance conferring variants can emerge during neutral drift, without being a product of adaptation. Our findings provide a novel and simple mechanistic explanation for why most genes in nature, and by extension, systems and organisms, inherently exhibit phenotypic variation, and thus, population-level evolvability.

evolutionary biology↗