TC1 symbiont suppresses malaria transmission by anopheline mosquitoes.

Malaria control demands the development of a wide range of complementary strategies. We describe the properties of a naturally occurring, non-genetically modified symbiotic bacterium, TC1, which was isolated from mosquitoes incapable of sustaining the development of parasites. TC1 inhibits early stages of development and subsequent transmission by the mosquito through secretion of a small-molecule inhibitor. We have identified this inhibitor to be the hydrophobic molecule harmane. We also found that, on mosquito contact, harmane penetrates the cuticle, inhibiting development. TC1 stably populates the mosquito gut, does not impose a fitness cost on the mosquito, and inhibits development for the mosquito's life. Contained field studies in Burkina Faso and modeling showed that TC1 has the potential to complement mosquito-targeted malaria transmission control.