Wolbachia and Spiroplasma are both maternally inherited endosymbionts in arthropods, and they can co‐infect the same species. However, how they interact with each other in the same host is not clear. Here we investigate a co‐infected Tetranychus truncatus spider mite strain that shares the same genetic background with singly infected and uninfected strains to detect the impacts of the two symbionts on their host. We found that Wolbachia‐infected and Spiroplasma‐infected mites can suffer significant fitness costs involving decreased fecundity, although with no effect on lifespan or development. Wolbachia induced incomplete cytoplasmic incompatibility in T. truncatus both in singly infected and doubly infected strains, resulting in female killing. In both females and males of the co‐infected spider mite strain, Wolbachia density was higher than Spiroplasma density. Transcriptome analysis of female adults showed that the most differentially expressed genes were found between the co‐infected strain and both the singly infected Spiroplasma strain and uninfected strain. The Wolbachia strain had the fewest differentially expressed genes compared with the co‐infected strain, consistent with the higher density of Wolbachia in the co‐infected strain. Wolbachia, therefore, appears to have a competitive advantage in host mites over Spiroplasma and is likely maintained in populations by cytoplasmic incompatibility despite having deleterious fitness effects.

中文翻译：

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在共感染的红蜘蛛Tetranychus truncatus中，Wolbachia支配了螺旋体。

Wolbachia和Spiroplasma都是节肢动物中母本遗传的内共生体，它们可以共同感染同一物种。但是，它们在同一主机中如何相互交互尚不清楚。在这里，我们研究了一种共同感染的Tetranychus truncatus蜘蛛螨菌株，该菌株与单独感染和未感染的菌株具有相同的遗传背景，以检测两个共生体对其寄主的影响。我们发现，感染了沃尔巴克氏菌和感染了螺旋藻的螨虫可能会遭受巨大的健身费用，包括生育力下降，尽管这不会影响其寿命或发育。沃尔巴克氏菌引起的T. truncatus细胞质不完全不相容无论是单独感染还是双重感染菌株，都导致女性死亡。在共同感染的红蜘蛛品系的雌性和雄性中，Wolbachia密度均高于螺旋体密度。雌性成虫的转录组分析表明，在共同感染的菌株与单独感染的螺旋体菌株和未感染的菌株之间发现了差异最大的基因。将沃尔巴克氏体与共同感染的菌株，具有较高的密度一致比较菌株具有最少的差异表达基因沃尔巴克氏体在共同感染的菌株。因此，Wolbachia在寄主螨虫方面似乎比螺旋体尽管具有有害的健身作用，但仍可能因细胞质不相容而在人群中维持。