Characterising within-host microbial interactions is essential to understand the drivers that shape these interactions and their consequences for host ecology and evolution. Here, we examined the bacterial microbiota hosted by the seabird soft tick Ornithodoros maritimus (Argasidae) in order to uncover bacterial interactions within ticks and how these interactions change over tick development. Bacterial communities were characterised through next-generation sequencing of the V3–V4 hypervariable region of the bacterial 16S ribosomal RNA gene. Bacterial co-occurrence and co-exclusion were determined by analysing networks generated from the metagenomic data obtained at each life stage. Overall, the microbiota of O. maritimus was dominated by four bacterial genera, namely Coxiella, Rickettsia, Brevibacterium and Arsenophonus, representing almost 60% of the reads. Bacterial diversity increased over tick development, and adult male ticks showed higher diversity than did adult female ticks. Bacterial networks showed that co-occurrence was more frequent than co-exclusion and highlighted substantial shifts across tick life stages; interaction networks changed from one stage to the next with a steady increase in the number of interactions through development. Although many bacterial interactions appeared unstable across life stages, some were maintained throughout development and were found in both sexes, such as Coxiella and Arsenophonus. Our data support the existence of a few stable interactions in O. maritimus ticks, on top of which bacterial taxa accumulate from hosts and/or the environment during development. We propose that stable associations delineate core microbial interactions, which are likely to be responsible for key biological functions.

表征宿主内微生物相互作用对于了解塑造这些相互作用的驱动因素及其对宿主生态和进化的影响至关重要。在这里，我们检查了由海鸟软蜱Ornithodoros maritimus（Argasidae）宿主的细菌微生物群，以揭示蜱内的细菌相互作用以及这些相互作用如何随着蜱的发育而变化。通过对细菌 16S 核糖体 RNA 基因的 V3-V4 高变区进行下一代测序来表征细菌群落。通过分析从每个生命阶段获得的宏基因组数据生成的网络，确定细菌共生和共排除。总体而言，O. maritimus的微生物群以四种细菌属为主，即Coxiella、Rickettsia、Brevibacterium和Arsenophonus，占读数的近 60%。细菌多样性随着蜱的发育而增加，成年雄性蜱比成年雌性蜱表现出更高的多样性。细菌网络表明，共同出现比共同排除更频繁，并突出了蜱虫生命阶段的重大变化；互动网络从一个阶段转变为下一个阶段，互动次数随着发展而稳步增加。尽管许多细菌相互作用在整个生命阶段似乎都不稳定，但有些在整个发育过程中都保持着，并且在两性中都发现了，例如Coxiella和Arsenophonus。我们的数据支持在O. maritimus蜱中存在一些稳定的相互作用，在发育过程中细菌类群从宿主和/或环境中积累。我们建议稳定关联描绘了核心微生物相互作用，这可能是关键生物功能的原因。