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

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.

本研究报道了感染舌蝇（Glossina fuscipes fuscipes，缩写Gff）的螺原体属（Spiroplasma）菌株的体外培养体系，以及采用牛津纳米孔技术（Oxford Nanopore Technology，ONT）测序，对三类样本中的该细菌完成全基因组测序的相关工作：三类样本分别为体外培养物、实验室维持的Gff种群，以及从乌干达采集的野生Gff种群。对上述细菌基因组的比较分析显示，其基因组成与结构高度相似，表明它们属于同一菌株，将其命名为sGff。系统基因组学分析结果显示，sGff隶属于螺原体（Spiroplasma poulsonii）进化枝，该进化枝同时包含其他感染双翅目昆虫的菌株。sGff基因组携带参与营养转运的基因，提示该菌株依赖宿主获取必需代谢产物。本研究还鉴定出大量可移动遗传元件与潜在防御基因，包括前噬菌体、质粒以及毒素基因。本研究采用核糖体RNA（rRNA）减法技术开展转录组分析，对Gff不同组织分区中的sGff潜在蛋白质组进行了表征，并发现螺原体相关产物在Gff血淋巴与生殖组织中大量表达，这为阐明该共生关系的潜在驱动因素提供了新的研究视角。