Interspecific Transfer of Bacterial Endosymbionts between Tsetse Fly Species: Infection Establishment and Effect on Host Fitness

Tsetse flies (Glossina spp.) can harbor up to three distinct species of endosymbiotic bacteria that exhibit unique modes of transmission and evolutionary histories with their host. Two mutualist enterics,Wigglesworthia andSodalis , are transmitted maternally to tsetse flies' intrauterine larvae. The third symbiont, from the genusWolbachia , parasitizes developing oocytes. In this study, we determined thatSodalis isolates from several tsetse fly species are virtually identical based on a phylogenetic analysis of theirftsZ gene sequences. Furthermore, restriction fragment-length polymorphism analysis revealed little variation in the genomes ofSodalis isolates from tsetse fly species within different subgenera (Glossina fuscipes fuscipes andGlossina morsitans morsitans ). We also examined the impact on host fitness of transinfectingG. fuscipes fuscipes andG. morsitans morsitans flies with reciprocalSodalis strains. Tsetse flies cleared of their nativeSodalis symbionts were successfully repopulated with theSodalis species isolated from a different tsetse fly species. These transinfected flies effectively transmitted the novel symbionts to their offspring and experienced no detrimental fitness effects compared to their wild-type counterparts, as measured by longevity and fecundity. Quantitative PCR analysis revealed that transinfected flies maintained theirSodalis populations at densities comparable to those in flies harboring native symbionts. Our ability to transinfect tsetse flies is indicative ofSodalis ' recent evolutionary history with its tsetse fly host and demonstrates that this procedure may be used as a means of streamlining future paratransgenesis experiments.