Project description:Endosymbiotic bacteria associated with eukaryotic hosts are omnipresent in nature, particularly in insects. Studying the bacterial side of host-symbiont interactions is, however, often limited by the unculturability and genetic intractability of the symbionts. Spiroplasma poulsonii is a maternally transmitted bacterial endosymbiont that is naturally associated with several Drosophila species. S. poulsonii strongly affects its host’s physiology, for example by causing male killing or by protecting it against various parasites. Despite intense work on this model since the 1950s, attempts to cultivate endosymbiotic Spiroplasma in vitro have failed so far. Here, we developed a method to sustain the in vitro culture of S. poulsonii by optimizing a commercially accessible medium. We also provide a complete genome assembly, including the first sequence of a natural plasmid of an endosymbiotic Spiroplasma species. Last, by comparing the transcriptome of the in vitro culture to the transcriptome of bacteria extracted from the host, we identified genes putatively involved in host-symbiont interactions. This work provides new opportunities to study the physiology of endosymbiotic Spiroplasma and paves the way to dissect insect-endosymbiont interactions with two genetically tractable partners.
Project description:Ticks are ectoparasites that have co-evolved with their hosts for millions of years. Unlike other blood-feeders, hard ticks take several days to complete a blood-meal, which makes them especially susceptible to the detection by host immune responses. To overcome this, ticks have developed a vast array of salivary effectors with immune modulatory properties. These effectors not only benefit tick survival but also influence pathogen transmission. We have characterized the extracellular vesicle protein cargo secreted within tick saliva. Extracellular vesicles were purified through density gradient from salivary gland cultures dissected from partially fed adult female Ixodes scapularis. Molecules present in the vesicles were then characterized using label-free proteomics. In this protein dataset, we have identified several tick immune modulatory proteins. This dataset demonstrates that arthropods secrete extracellular vesicles for the translocation of effectors during blood-feeding.