Metabolic complexity increases adaptability

Abstract

Bacteria show a striking ability to adapt to new environments through horizontal gene transfer. Anecdotal evidence suggests that some bacteria are more adaptable than others: e.g., intestinal E. coli frequently spin off pathogenic strains adapted to other human tissues, while gastric Helicobacter pylori do not. However, it is unclear what determines the ability of individual strains or species to adapt to new environments. Here, we use pan-genome scale modeling to explore the ability of 102 different unicellular organisms to adapt to each of 5000+ diverse nutritional environments. While the small metabolic systems of specialized endosymbionts typically require 50+ additional metabolic reactions to adapt to new environments, different strains of the generalist E. coli require on average less than 5 new reactions. Thus, there is a positive feedback between metabolic complexity and adaptability, contrary to speculations that complex systems are generally less adaptable.