Gomaa Fatma, Gersh Maxim, Cavanaugh Colleen M
Department of Organismic and Evolutionary Biology, Biological Laboratory, Harvard University, Cambridge, Massachusetts, 02138, USA.
J Eukaryot Microbiol. 2018 Jul;65(5):661-668. doi: 10.1111/jeu.12511. Epub 2018 Mar 7.
Diverse species of Legionella and Legionella-like amoebal pathogens (LLAPs) have been identified as intracellular bacteria in many amoeboid protists. There are, however, other amoeboid groups such as testate amoeba for which we know little about their potential to host such bacteria. In this study, we assessed the occurrence and diversity of Legionella spp. in cultures and environmental isolates of freshwater arcellinid testate amoebae species, Arcella hemispherica, Arcella intermedia, and Arcella vulgaris, via 16S rRNA gene sequence analyses and fluorescent in situ hybridization (FISH). Analysis of the 16S rRNA gene sequences indicated that A. hemispherica, A. intermedia, and A. vulgaris host Legionella-like bacteria with 94-98% identity to other Legionella spp. based on NCBI BLAST search. Phylogenetic analysis placed Legionella-like Arcella-associated bacteria (LLAB) in three different clusters within a tree containing all other members of Legionella and LLAPs. The intracellular localization of the Legionella within Arcella hosts was confirmed using FISH with a Legionella-specific probe. This study demonstrates that the host range of Legionella and Legionella-like bacteria in the Amoebozoa extends beyond members of "naked" amoebae species, with members of the testate amoebae potentially serving an ecological role in the dispersal, protection, and replication of Legionella spp. in natural environments.
多种嗜肺军团菌属细菌及类嗜肺军团菌变形虫病原体（LLAPs）已被鉴定为许多变形虫原生生物中的细胞内细菌。然而，还有其他变形虫类群，如壳吸管虫，我们对它们容纳此类细菌的潜力知之甚少。在本研究中，我们通过16S rRNA基因序列分析和荧光原位杂交（FISH），评估了嗜肺军团菌属细菌在淡水半球圆壳虫、中型圆壳虫和普通圆壳虫这三种淡水有壳变形虫物种的培养物和环境分离物中的存在情况及多样性。16S rRNA基因序列分析表明，基于NCBI BLAST搜索，半球圆壳虫、中型圆壳虫和普通圆壳虫容纳的类嗜肺军团菌细菌与其他嗜肺军团菌属细菌的同源性为94%-98%。系统发育分析将类嗜肺军团菌圆壳虫相关细菌（LLAB）置于包含嗜肺军团菌和LLAPs所有其他成员的一棵树中的三个不同簇中。使用嗜肺军团菌特异性探针通过FISH证实了嗜肺军团菌在圆壳虫宿主细胞内的定位。本研究表明，变形虫门中嗜肺军团菌和类嗜肺军团菌细菌的宿主范围超出了“裸”变形虫物种成员，有壳变形虫成员可能在自然环境中嗜肺军团菌属细菌的传播、保护和复制中发挥生态作用。
