Ingle Danielle J, Walsh Calum J, Samuel Genevieve R, Wick Ryan R, Davidovich Nadav, Fiocchi Eleonora, Judd Louise M, Elliman Jennifer, Owens Leigh, Stinear Timothy P, Basso Andrea, Pretto Tobia, Newton Hayley J
Department of Microbiology and Immunology, The University of Melbourne at The Peter Doherty Institute for Infection and Immunity, Melbourne, Victoria, Australia.
Centre for Pathogen Genomics, University of Melbourne, Parkville, Victoria, Australia.
mSphere. 2025 Apr 29;10(4):e0100224. doi: 10.1128/msphere.01002-24. Epub 2025 Mar 10.
The Coxiellaceae bacterial family, within the order Legionellales, is defined by a collection of poorly characterized obligate intracellular bacteria. The zoonotic pathogen and causative agent of human Q fever, , represents the best-characterized member of this family. Coxiellaceae establish replicative niches within diverse host cells and rely on their host for survival, making them challenging to isolate and cultivate within a laboratory setting. Here, we describe a new genus within the Coxiellaceae family that has been previously shown to infect economically significant freshwater crayfish. Using culture-independent long-read metagenomics, we reconstructed the complete genome of this novel organism and demonstrate that the species previously referred to as Candidatus represents a novel genus within this family, herein denoted Candidatus . Interestingly, we demonstrate that Candidatus encodes a complete, putatively functional Dot/Icm type 4 secretion system that likely mediates the intracellular success of this pathogen. analysis defined a unique repertoire of Dot/Icm effector proteins and highlighted homologs of several important effectors, including a homolog of CpeB that was demonstrated to be a Dot/Icm substrate in .IMPORTANCEUsing long-read sequencing technology, we have uncovered the full genome sequence of Candidatus , a pathogen of economic importance in aquaculture. Analysis of this sequence has revealed new insights into this novel member of the Coxiellaceae family, demonstrating that it represents a new genus within this poorly characterized family of intracellular organisms. Importantly, the genome sequence reveals invaluable information that will support diagnostics and potentially both preventative and treatment strategies within crayfish breeding facilities. Candidatus also represents a new member of Dot/Icm pathogens that rely on this system to establish an intracellular niche. Candidatus possesses a unique cohort of putative Dot/Icm substrates that constitute a collection of new eukaryotic cell biology-manipulating effector proteins.
军团菌目内的考克斯氏体科细菌家族由一群特征描述不完善的专性细胞内细菌组成。人类Q热的人畜共患病原体 是该家族中特征描述最完善的成员。考克斯氏体科在多种宿主细胞内建立复制龛，依赖宿主生存，这使得它们在实验室环境中难以分离和培养。在此，我们描述了考克斯氏体科内的一个新属，该属先前已被证明可感染具有经济重要性的淡水小龙虾。利用不依赖培养的长读长宏基因组学，我们重建了这种新生物体的完整基因组，并证明先前称为“候选 ”的物种代表该家族内的一个新属，在此命名为“候选 ”。有趣的是，我们证明候选 编码一个完整的、可能具有功能的Dot/Icm 4型分泌系统，该系统可能介导这种病原体在细胞内的成功感染。 分析确定了Dot/Icm效应蛋白的独特组成，并突出了几种重要 效应蛋白的同源物，包括CpeB的一个同源物，该同源物在 中被证明是一种Dot/Icm底物。
重要性
利用长读长测序技术，我们揭示了候选 的全基因组序列，这是水产养殖中具有经济重要性的病原体。对该序列的分析为考克斯氏体科这个新成员提供了新的见解，表明它代表了这个特征描述不完善的细胞内生物家族中的一个新属。重要的是，基因组序列揭示了宝贵的信息，将支持小龙虾养殖设施内的诊断以及潜在的预防和治疗策略。候选 也是依赖该系统建立细胞内龛的Dot/Icm病原体的新成员。候选 拥有一组独特的假定Dot/Icm底物，它们构成了一组新的操纵真核细胞生物学的效应蛋白。
