Unit of Food Microbiology, Institute of Food Safety, Food Technology and Veterinary Public Health, Department for Farm Animals and Veterinary Public Health, University of Veterinary Medicine Vienna, 1210 Vienna, Austria.
Centre for Microbiology and Environmental Systems Science, University of Vienna, 1030 Vienna, Austria.
FEMS Microbiol Ecol. 2022 Feb 10;98(1). doi: 10.1093/femsec/fiac001.
Free-living amoebae often harbor obligate intracellular bacterial symbionts. Amoebophilus (A.) asiaticus is a representative of a lineage of amoeba symbionts in the phylum Bacteroidota. Here, we analyse the transcriptome of A. asiaticus strain 5a2 at four time points during its infection cycle and replication within the Acanthamoeba host using RNA sequencing. Our results reveal a dynamic transcriptional landscape throughout different A. asiaticus life cycle stages. Many intracellular bacteria and pathogens utilize eukaryotic-like proteins (ELPs) for host cell interaction and the A. asiaticus 5a2 genome shows a particularly high abundance of ELPs. We show the expression of all genes encoding ELPs and found many ELPs to be differentially expressed. At the replicative stage of A. asiaticus, ankyrin repeat proteins and tetratricopeptide/Sel1-like repeat proteins were upregulated. At the later time points, high expression levels of a type 6 secretion system that likely prepares for a new infection cycle after lysing its host, were found. This study reveals comprehensive insights into the intracellular lifestyle of A. asiaticus and highlights candidate genes for host cell interaction. The results from this study have implications for other intracellular bacteria such as other amoeba-associated bacteria and the arthropod symbionts Cardinium forming the sister lineage of A. asiaticus.
自由生活的变形虫通常含有必需的细胞内细菌共生体。亚洲变形虫（A.）是变形虫共生体门中的一个代表。在这里，我们使用 RNA 测序分析了在棘阿米巴宿主内感染周期和复制过程中四个时间点的 A. asiaticus 菌株 5a2 的转录组。我们的结果揭示了不同 A. asiaticus 生命周期阶段的动态转录景观。许多细胞内细菌和病原体利用真核样蛋白（ELPs）进行宿主细胞相互作用，而 A. asiaticus 5a2 基因组显示出特别高丰度的 ELP。我们展示了所有编码 ELP 的基因的表达，并发现许多 ELP 存在差异表达。在 A. asiaticus 的复制阶段，锚蛋白重复蛋白和四肽/ Sel1 样重复蛋白上调。在稍后的时间点，发现了一种 6 型分泌系统的高表达水平，该系统可能在裂解宿主后为新的感染周期做准备。本研究全面揭示了 A. asiaticus 的细胞内生活方式，并突出了宿主细胞相互作用的候选基因。这项研究的结果对其他细胞内细菌（如其他与变形虫相关的细菌和与 A. asiaticus 形成姐妹谱系的节肢动物共生体 Cardinium）具有重要意义。
