Amoebae interact with bacteria in multifaceted ways. Amoeba predation can serve as a selective pressure for the development of bacterial virulence traits. Bacteria may also adapt to life inside amoebae, resulting in symbiotic relationships. Indeed, particular lineages of obligate bacterial endosymbionts have been found in different amoebae. Here, we screened an extensive collection of Dictyostelium discoideum wild isolates for the presence of these bacterial symbionts using endosymbiont specific PCR primers. We find that these symbionts are surprisingly common, identified in 42% of screened isolates (N = 730). Members of the Chlamydiae phylum are particularly prevalent, occurring in 27% of the amoeba isolated. They are novel and phylogenetically distinct from other Chlamydiae. We also found Amoebophilus symbionts in 8% of screened isolates (N = 730). Antibiotic-cured amoebae behave similarly to their Chlamydiae or Amoebophilus-infected counterparts, suggesting that these endosymbionts do not significantly impact host fitness, at least in the laboratory. We found several natural isolates were co-infected with multiple endosymbionts, with no obvious fitness effect of co-infection under laboratory conditions. The high prevalence and novelty of amoeba endosymbiont clades in the model organism D. discoideum opens the door to future research on the significance and mechanisms of amoeba–symbiont interactions.

中文翻译：

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新型衣原体和变形虫内共生菌在模型社会变形虫的野生分离物中普遍存在盘基网柄菌

变形虫以多种方式与细菌相互作用。变形虫的捕食可以作为细菌毒力性状发展的选择压力。细菌也可能适应阿米巴体内的生活，从而形成共生关系。事实上，已经在不同的变形虫中发现了特定的专性细菌内共生菌谱系。在这里，我们使用内共生体特异性 PCR 引物筛选了大量盘基网柄菌野生分离株中这些细菌共生体的存在。我们发现这些共生体非常普遍，在 42% 的筛选分离株中发现（N = 730)。衣原体门的成员特别普遍，发生在 27% 的分离的变形虫中。它们是新颖的并且在系统发育上与其他衣原体不同。我们还在8% 的筛选分离株中发现了 Amoebophilus共生体 ( N  = 730)。抗生素治愈的变形虫的行为与其衣原体或变形虫感染的对应物相似，这表明这些内共生菌不会显着影响宿主的适应性，至少在实验室中是这样。我们发现几种天然分离株与多种内共生菌共感染，在实验室条件下共感染没有明显的适应度效应。模式生物D. discoideum中变形虫内共生进化枝的高流行率和新颖性为未来研究变形虫-共生体相互作用的意义和机制打开了大门。