A highly divergent Wolbachia with a tiny genome in an insect-parasitic tylenchid nematode

Wolbachia symbionts are the most successful host-associated microbes on the planet, infecting arthropods and nematodes. Their role in nematodes is particularly enigmatic, with filarial nematode species either 100% infected and dependent on symbionts for reproduction and development, or not at all infected. We have discovered a highly divergent strain of Wolbachia in an insect-parasitic tylenchid nematode, Howardula sp., in a nematode clade that has not previously been known to harbour Wolbachia. While this nematode is 100% infected with Wolbachia, we did not detect it in related species. We sequenced the Howardula symbiont (wHow) genome and found that it is highly reduced, comprising only 550 kilobase pairs of DNA, ~35% smaller than the smallest Wolbachia nematode symbiont genomes. The wHow genome is a subset of all other Wolbachia genomes and has not acquired any new genetic information. While it has lost many genes, including genes involved in cell wall synthesis and cell division, it...沃尔巴克氏体（Wolbachia）共生体是地球上最成功的宿主相关微生物，可感染节肢动物与线虫。其在线虫中的作用尤为神秘莫测：丝虫线虫类群要么100%被感染且依赖共生体完成繁殖与发育，要么完全未被感染。我们在一种昆虫寄生性垫刃目线虫——霍华德线虫属（Howardula sp.）物种中，发现了一株高度趋异的沃尔巴克氏体菌株；该线虫所属的演化支此前从未被报道携带沃尔巴克氏体。尽管该线虫100%被沃尔巴克氏体感染，但我们并未在其近缘物种中检测到该共生体。我们对该霍华德线虫共生体（wHow）的基因组进行了测序，发现其基因组高度缩减，仅包含550千碱基对的DNA，比已知最小的沃尔巴克氏体线虫共生体基因组小约35%。wHow基因组是所有其他沃尔巴克氏体基因组的子集，未获得任何新的遗传信息。尽管它丢失了诸多基因，包括参与细胞壁合成与细胞分裂的基因，但……