A Coxiella-like endosymbiont is a potential vitamin source for the Lone Star tick.
A Coxiella-like endosymbiont is a potential vitamin source for the Lone Star tick.
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DOI：
10.1093/gbe/evv016
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发表时间：
2015-01-23
影响因子：
3.3
通讯作者：
Raghavan R
中科院分区：
文献类型：
--
作者：
Smith TA;Driscoll T;Gillespie JJ;Raghavan R
Amblyomma americanum（孤星星蜱）在美国是一种重要的疾病媒介。它传播几种人类病原体，包括人类单核细胞埃立克体病、土拉菌病和南方蜱相关皮疹疾病的病原体。吸血昆虫（昆虫纲）依靠细菌内共生体提供血液中缺乏的维生素和辅因子。目前还不清楚这种缺陷是如何补偿蜱（蛛形纲），饲料只对哺乳动物的血液。以前在A.美国。清除这种细菌（CLEAA，A. americanum）与抗生素一起降低了蜱的繁殖力，表明它是一种必需的内共生体。为了确定它在这种共生关系中的作用，我们对CLEAA基因组进行了测序。与C. burnetii（1，995，281 bp），CLEAA基因组编码大多数主要的维生素和辅因子生物合成途径，暗示CLEAA是维生素供应内共生体。相反，CLEAA缺乏任何可识别的毒力基因，表明它不是病原体，尽管它存在于蜱唾液腺中。作为两个C.贝氏体和众多的“类柯克斯体细菌”已被报道从几种蜱中，我们确定了这两种细菌之间的进化关系。系统发育估计表明CLEAA是C.我们的研究结果对控制A. burnetii的策略具有重要意义。americanum和它所携带的病原体，并且还贡献了关于蜱及其营养供应内共生体的代谢相互依赖性的新信息。
Amblyomma americanum (Lone star tick) is an important disease vector in the United States. It transmits several human pathogens, including the agents of human monocytic ehrlichiosis, tularemia, and southern tick-associated rash illness. Blood-feeding insects (Class Insecta) depend on bacterial endosymbionts to provide vitamins and cofactors that are scarce in blood. It is unclear how this deficiency is compensated in ticks (Class Arachnida) that feed exclusively on mammalian blood. A bacterium related to Coxiella burnetii, the agent of human Q fever, has been observed previously within cells of A. americanum. Eliminating this bacterium (CLEAA, Coxiella-like endosymbiont of A. americanum) with antibiotics reduced tick fecundity, indicating that it is an essential endosymbiont. In an effort to determine its role within this symbiosis, we sequenced the CLEAA genome. While highly reduced (656,901 bp) compared with C. burnetii (1,995,281 bp), the CLEAA genome encodes most major vitamin and cofactor biosynthesis pathways, implicating CLEAA as a vitamin provisioning endosymbiont. In contrast, CLEAA lacks any recognizable virulence genes, indicating that it is not a pathogen despite its presence in tick salivary glands. As both C. burnetii and numerous “Coxiella-like bacteria” have been reported from several species of ticks, we determined the evolutionary relationship between the two bacteria. Phylogeny estimation revealed that CLEAA is a close relative of C. burnetii, but was not derived from it. Our results are important for strategies geared toward controlling A. americanum and the pathogens it vectors, and also contribute novel information regarding the metabolic interdependencies of ticks and their nutrient-provisioning endosymbionts.