Data from: The Rickettsia endosymbiont of Ixodes pacificus contains all the genes of de novo folate biosynthesis

Ticks and other arthropods often are hosts to nutrient providing bacterial endosymbionts, which contribute to their host’s fitness by supplying nutrients such as vitamins and amino acids. It has been detected, in our lab, that Ixodes pacificus is host to Rickettsia species phylotype G021. This endosymbiont is predominantly present, and 100% maternally transmitted in I. pacificus. To study roles of phylotype G021 in I. pacificus, bioinformatic and molecular approaches were carried out. MUMmer genome alignments of whole genome sequence of I. scapularis, a close relative to I. pacificus, against completely sequenced genomes of R. bellii OSU85-389, R. conorii, and R. felis, identified 8,190 unique sequences that are homologous to Rickettsia sequences in the NCBI Trace Archive. MetaCyc metabolic reconstructions revealed that all folate gene orthologues (folA, folC, folE, folKP, ptpS) required for de novo folate biosynthesis are present in the genome of Rickettsia buchneri in I. scapularis. To examine the metabolic capability of phylotype G021 in I. pacificus, genes of the folate biosynthesis pathway of the bacterium were PCR amplified using degenerate primers. BLAST searches identified that nucleotide sequences of the folA, folC, folE, folKP, and ptpS genes possess 98.6%, 98.8%, 98.9%, 98.5% and 99.0% identity respectively to the corresponding genes of Rickettsia buchneri. Phylogenetic tree constructions show that the folate genes of phylotype G021 and homologous genes from various Rickettsia species are monophyletic. This study has shown that all folate genes exist in the genome of Rickettsia species phylotype G021 and that this bacterium has the genetic capability for de novo folate synthesis.

蜱虫及其他节肢动物通常为提供营养的细菌内共生体（bacterial endosymbionts）的宿主，这类共生体通过供给维生素、氨基酸等营养物质，提升宿主的生存适配性。本实验室已检测证实，太平洋硬蜱（Ixodes pacificus）体内携带有立克次体属系统型G021（Rickettsia species phylotype G021）。该内共生体在太平洋硬蜱体内广泛存在，并通过母系途径实现100%的垂直传播。为探究该系统型G021在太平洋硬蜱体内的功能，本研究采用了生物信息学与分子生物学研究方法。通过对亲缘关系与太平洋硬蜱相近的肩突硬蜱（Ixodes scapularis）的全基因组序列，与贝氏立克次体OSU85-389（Rickettsia bellii OSU85-389）、康氏立克次体（Rickettsia conorii）以及猫立克次体（Rickettsia felis）的完整基因组进行MUMmer基因组比对（MUMmer genome alignments），本研究在NCBI序列追踪档案库（NCBI Trace Archive）中鉴定出8190条与立克次体序列同源的独特序列。MetaCyc代谢重构（MetaCyc metabolic reconstructions）分析显示，肩突硬蜱体内布氏立克次体（Rickettsia buchneri）的基因组中，包含从头叶酸生物合成所需的全部叶酸基因直系同源基因（folate gene orthologues）：folA、folC、folE、folKP及ptpS。为检测太平洋硬蜱体内系统型G021的代谢能力，研究人员利用简并引物通过聚合酶链式反应（PCR）扩增了该细菌的叶酸生物合成通路基因。BLAST序列比对搜索（BLAST searches）结果显示，folA、folC、folE、folKP及ptpS基因的核苷酸序列，与布氏立克次体对应基因的序列一致性分别为98.6%、98.8%、98.9%、98.5%及99.0%。系统发育树构建结果表明，系统型G021的叶酸基因与各类立克次体物种的同源基因构成单系群（monophyletic）。本研究证实，立克次体属系统型G021的基因组中存在全部叶酸基因，且该细菌具备从头叶酸生物合成的遗传能力。