In vitro cultivation and genomic insights into the Spiroplasma symbiont of the tsetse fly Glossina fuscipes; implications for trypanosome transmission control

Here, we report on the in vitro cultivation of the Spiroplasma strain infecting Glossina fuscipes fuscipes (Gff) and the whole genome sequence of the bacterium from different sample types: in vitro culture, as well as from a laboratory maintained line of Gff and from a natural population of Gff obtained in Uganda, using Oxford Nanopore technology (ONT) sequencing. Comparative analysis of these bacterial genomes revealed a high degree of similarity in gene content and structure, indicating that they belong to the same strain, designated sGff. Phylogenomic analyses placed sGff within the Spiroplasma poulsonii clade, which includes other Dipteran-infecting strains. The sGff genome contained genes involved in nutrient transport, indicating that sGff relies on its host for essential metabolites. We also identified numerous mobile genetic elements and putative defensive genes, including prophages, plasmids, and toxin genes. Our transcriptomic analysis, using an rRNA subtraction approach, characterized the putative proteome of sGff in different fly compartments and highlighted abundant expression of Spiroplasma products in the hemolymph and reproductive tissues of Gff, such as, shedding light on potential factors contributing to the symbiosis.