Experimental evolution of insect-microbe mutualism

Obligate insect-bacterium mutualism is among the most sophisticated forms of symbiosis. However, such obligate symbiotic bacteria must have been originally derived from free-living environmental bacteria. How have highly specialized obligate mutualists arisen from less-specialized free-living microorganisms? To address this fundamental evolutionary question, we recently established a novel experimental model system that enables laboratory evolution of mutualism between the stinkbug Plautia stali and the model bacterium Escherichia coli.
The insect-E. coli experimental symbiotic system opens a window to directly observe and analyze the evolutionary processes and mechanisms of mutualistic symbiosis in real time. Considering that E. coli is among the best understood cellular organisms, laboratory evolution of mutualism using such a model bacterium with ample technological and genetic resources will lead to understanding of previously unapproachable evolutionary aspects of symbiosis. Since E. coli is a universal component of the gut microbiome of human, mouse and other vertebrates, the insect-E. coli system in comparison with the germ-free mouse-E. coli experimental evolution system would enable us to pursue not only the differences but also the commonality underpinning the mechanisms of gut symbiosis across vertebrates and invertebrates. Under the ERATO project, we aim at drastically promoting our understanding of symbiosis using the novel insect-E. coli and mammal-E. coli experimental symbiotic systems in combination with genome engineering technologies, ex vivo microfluidic bacterial culture technologies, and high-throughput robotic experimental evolutionary systems.