Single mutation makes Escherichia coli an insect mutualist

Abstract

We report an experimental system in which Escherichia coli evolves into an insect mutualist. When the essential gut symbiont of the stinkbug Plautia stali was replaced by E. coli, a few survivor insects exhibited specific localization and vertical transmission of E. coli. Through trans-generational maintenance with P. stali, several hyper-mutating E. coli lines independently evolved host's high adult emergence and improved body color. Such "mutualistic" E. coli lines exhibited independent mutations disrupting the carbon catabolite repression (CCR) global transcriptional regulator. Each of the mutations reproduced the mutualistic phenotypes when introduced into wild-type E. coli, confirming that the single CCR mutations instantly make E. coli an insect mutualist. Our discovery uncovers that evolution of elaborate mutualism can proceed more easily and rapidly than conventionally envisaged.

Bacterial c-di-GMP plays a key role in the evolution of host-association

“…4, Supplementary Table 4, Supplementary Table 5). The latter result is consistent with a decrease in motility described for E. coli that evolved to become a mutualist in stinkbugs 17 , but contrasts with findings that sufficient swarming is required for colonization initiation of zebrafish and bobtail squid 18,19 . These contrasts are likely due to differences in symbiont recruitment between the host systems, defined by either aquatic environments for zebrafish and squid, and terrestrial environments for C. elegans and stinkbug, respectively.…”

Weevil carbohydrate intake triggers endosymbiont proliferation: a trade-off between host benefit and endosymbiont burden

“…In insects, endosymbiont acquisition generally starts with domestication of parasites or commensals 43-45 . Host control over endosymbionts is often observed, as endosymbionts gradually lose the ability of autonomous life through genome shrinkage 46,47 and point mutations 48 , sometimes retaining only the metabolic pathways that confer fitness advantage for the host 20 . Endosymbiont loss and/or replacement generally occur in concomitance with excessive genome shrinkage limiting host advantages 49–52 .…”