Symbiotic Rickettsia Species as a Model System for the Study of Folate Biosynthes

共生立克次体作为叶酸生物合成研究的模型系统

基本信息

批准号：
8289045
负责人：
Jianmin Zhong
金额：
$ 35.35万
依托单位：
HUMBOLDT STATE UNIVERSITY
依托单位国家：
美国
项目类别：
财政年份：
2012
资助国家：
美国
起止时间：
2012-09-01 至 2017-08-31
项目状态：
已结题

项目摘要

DESCRIPTION (provided by applicant): Nonpathogenic nutrient-providing bacterial endosymbionts have been shown to contribute to their hosts' fitness by supplying them with essential vitamins and amino acids. The metabolic basis for the symbiotic relationship of endosymbionts in ticks has been unknown. Recent metabolic reconstruction, PCR, and DNA sequencing results in our lab have shown that a Rickettsia species in Ixodes pacificus carries genes for the anabolism of cofactors and vitamins. The biosynthetic pathway of folate (vitamin B9) is of particular interest because previous bioinformatic metabolic reconstruction in our lab indicates that the pathway exists in its entirety in the genome of the Rickettsia species. The overall objective of the project is to study bacterial vitamin biosynthetic genes that are essentia for the symbiotic relationship with the tick host. We hypothesize that the endosymbiotic Rickettsia species synthesizes folate, and that the vitamin is utilized by the tick host. The proposed work has three major aspects: 1) Characterization of genes in the folate pathway of the Rickettsia species in Ixodes pacificus using PCR, cloning, and sequencing. 2) Characterization of gene expression patterns of genes in the folate pathway of the Rickettsia species in Ixodes pacificus using quantitative reverse transcriptase PCR (qRT-PCR). 3) Characterization of function of gene products in the folate biosynthetic pathway of the Rickettsia species in Ixodes pacificus by complementation and in vitro enzymatic assay. The research will increase our understanding of the metabolism of folate in ticks, as well as the metabolic basis of symbiotic interactions between the symbiotic Rickettsia species and Ixodes pacificus ticks. Describing the functions of the biosynthetic genes and defining the capacity of the vitamins contributed by the Rickettsia species in Ixodes pacificus, will provide important insights into molecular mechanisms of the endosymbiotic relationship in Ixodes pacificus. PUBLIC HEALTH RELEVANCE: Lyme borreliosis and anaplasmosis are the most common tick-borne diseases in the United States, and prevention of these diseases has become the focus of current tick research. Bacteria that live within eukaryotic cells have allowed their hosts to acquire metabolic capabilities otherwise unavailable. These bacterial partners contribute to their hosts' fitness by providing essential nutrients such as vitamins and amino acids. Arthropods that feed primarily or entirely on blood are virtually a breeding ground for these types of partnerships because vertebrate blood rarely contains sufficient quantities of essential B-vitamins and amino acids. Therefore, the diet of blood feeding arthropods is complemented with bacterially synthesized vitamins (2, 5, 76). The sole diet of most ticks is blood from vertebrates, but the sources of B-vitamins for Ixodes pacificus ticks are unknown. The recent sequencing of the Ixodes scapularis genome revealed genomic sequences of the tick's bacterial partner. Using freely available computer software, as well as computer algorithms written in our lab, we have discovered all six genes involved in the vitamin B9 biosynthetic pathway. The pathway is from a Rickettsia species in Ixodes pacificus, the West Coast relative of Ixodes scapularis. In this proposal, we hypothesize that the Rickettsia species, living within Ixodes pacificus cells, produces essential B9 vitamin that is not synthesized by Ixodes pacificus. We will determine if all genes in the B9 vitamin pathway of the Rickettsia species are actively transcribed in Ixodes pacificus ticks, and if these bacterial genes encode proteins that synthesize vitamin B9. The proposed studies will offer an ideal model system to study the impact of bacterial endosymbionts on the metabolism of ticks and more specifically, the effect of the Rickettsia endosymbiont on Ixodes pacificus fitness.

描述（由申请人提供）：已证明具有非致病性营养的细菌性内共生植物可以通过为其提供必需的维生素和氨基酸，从而有助于其宿主的适应性。壁虱中内共生体共生关系的代谢基础尚不清楚。在我们实验室中，最近的代谢重建，PCR和DNA测序结果表明，ixodes pacificus中的立克氏症物种携带辅助因子和维生素的合成代谢基因。叶酸（维生素B9）的生物合成途径特别令人感兴趣，因为我们实验室中先前的生物信息学代谢重建表明，该途径的整体存在于立克斯氏症物种的基因组中。该项目的总体目的是研究细菌维生素生物合成基因，这些基因是与tick宿主共生关系的实质性。我们假设内共生体物质物种合成了叶酸，并且tick宿主利用了维生素。所提出的工作具有三个主要方面：1）使用PCR，克隆和测序的ixodes Pacificus中立克氏菌种类的基因表征。 2）使用定量逆转录酶PCR（QRT-PCR），在ixodes太平洋中立克属物种的叶酸途径中基因表达模式表征了基因表达模式。 3）通过互补和体外酶试验，在ixodes太平洋ixodes Pacificus中立克物种的叶酸生物合成途径中基因产物的功能表征。这项研究将提高我们对壁虱中叶酸代谢的理解，以及共生人力体物种与ixodes pacificus tick虫之间共生相互作用的代谢基础。描述生物合成基因的功能以及定义ixodes pacificus中的立克氏症物种贡献的维生素的能力，将为ixodes pacificus中内共生关系的分子机制提供重要的见解。公共卫生相关性：莱姆毛毛虫病和肿瘤病是美国最常见的tick传播疾病，预防这些疾病已成为当前tick研究的重点。生活在真核细胞内的细菌使他们的宿主允许获得代谢能力，否则就无法获得。这些细菌伴侣通过提供诸如维生素和氨基酸的必需营养素来为宿主的适应性做出贡献。主要以血液为基础的节肢动物实际上是这些类型的繁殖地伙伴关系是因为脊椎动物的血液很少含有足够数量的必需B-Vitamin和氨基酸。因此，血液喂养节肢动物的饮食与细菌合成的维生素相辅相成（2、5、76）。大多数壁虱的唯一饮食是脊椎动物的血液，但是，ixodes ticks tick的b-vitamins的来源尚不清楚。 ixodes肩cap骨基因组的最新测序揭示了壁虱细菌伴侣的基因组序列。使用可自由使用的计算机软件以及在我们的实验室中编写的计算机算法，我们发现了涉及维生素B9生物合成途径的所有六个基因。该途径来自ixodes肩cap骨的西海岸亲戚ixodes pacificus的立克物种。在此提案中，我们假设生活在ixodes pacificus细胞内的立克症物种会产生必需的B9维生素，而ixodes pacificus却不合成。我们将确定立克氏菌的B9维生素途径中的所有基因是否均在ixodes pacificus tick中积极转录，以及这些细菌基因是否编码合成维生素B9的蛋白质。拟议的研究将提供一个理想的模型系统，以研究细菌内共生体对壁虱代谢的影响，更具体地说，是人力体内共生体对ixodes pacificus适应性的影响。

项目成果

期刊论文数量（5）

专著数量（0）

科研奖励数量（0）

会议论文数量（0）

专利数量（0）

The Rickettsia Endosymbiont of Ixodes pacificus Contains All the Genes of De Novo Folate Biosynthesis.

DOI：
10.1371/journal.pone.0144552
发表时间：
2015
期刊：
PloS one
影响因子：
3.7
作者：
Hunter DJ;Torkelson JL;Bodnar J;Mortazavi B;Laurent T;Deason J;Thephavongsa K;Zhong J
通讯作者：
Zhong J