Single mutation makes Escherichia coli an insect mutualist

"Insect essential symbiotic bacteria have evolved from free-living bacteria." – This is an insightful hypothesis advocated in the early days of symbiotic research. The hypothesis has been reinforced by incorporating the outcomes of molecular phylogeny and comparative genome analyses and has become generally accepted. However, the empirical research supporting this hypothesis is scarce. Moreover, it is an unsolved riddle what factors prompted bacteria to change their lifestyle from free-living to obligate symbiosis at a very early stage of the evolution of symbiotic relationships. In this presentation, I will report that a single mutation occurred in the Escherichia coli genome significantly improved the performance of host stink bugs. It is possible that this kind of mutation represents one of the evolutionary entrances to establish obligatory symbioses and I will discuss its importance in the evolution of insect-microbe systems.