Comparative genomics and transcriptomics of the Spiroplasma glossinidia strain sGff reveal insights into host interaction and trypanosome resistance in Glossina fuscipes fuscipes

Tsetse ( Glossina spp.) are vectors of African trypanosomes, the causative agents of Human and African Animal trypanosomiases, diseases that remain significant medical and socioeconomic challenges in sub-Saharan Africa. In addition to trypanosomes, tsetse harbor both obligate and facultative symbiotic bacteria that can influence vector competence and reproductive biology. One such facultative symbiont, Spiroplasma glossinidia , infects several tsetse species within the Palpalis subgroup. In Glossina fuscipes fuscipes ( Gff ), the Spiroplasma glossinidia strain s Gff induces a trypanosome-refractory phenotype and negatively impacts reproductive fitness by reducing female fecundity. However, the mechanisms behind these Spiroplasma -derived phenotypes remain poorly understood. Here, we report successful in vitro cultivation of s Gff and present complete genomes from three sources: in vitro cultured s Gff and s Gff isolated from both laboratory-maintained and wild-caught (Uganda) Gff flies. Comparative genomic analyses revealed a high degree of similarity in gene content and synteny among these s Gff samples, confirming that they represent isolates of the same strain. Phylogenomic analyses placed s Gff within the Spiroplasma poulsonii clade. The s Gff genome is highly dynamic, containing numerous mobile genetic elements. Additionally, in silico annotations indicate that s Gff relies on its host for both lipids and carbohydrates and produces several toxins, all of which could be implicated in the observed trypanosome refractory phenotype. Finally, comparative transcriptomic analysis of s Gff from host hemolymph versus in vitro culture provided insights into potential factors relevant to host-symbiont interactions. Our findings provide a foundation for understanding the nutritional dialogue between s Gff and its host and identify symbiotic products that may contribute to trypanosome resistance. Furthermore, the establishment of an in vitro culture system for s Gff represents a significant resource for future functional studies with potential implications for vector control.