Wolbachia are alpha-proteobacteria symbionts infecting a large range of arthropod species and two different families of nematodes. Interestingly, these endosymbionts are able to induce diverse phenotypes in their hosts: they are reproductive parasites within many arthropods, nutritional mutualists within some insects and obligate mutualists within their filarial nematode hosts. Defining Wolbachia ‘species’ is controversial and so they are commonly classified into 17 different phylogenetic lineages, termed supergroups, named A–F, H–Q and S. However, available genomic data remain limited and not representative of the full Wolbachia diversity; indeed, of the 24 complete genomes and 55 draft genomes of Wolbachia available to date, 84 % belong to supergroups A and B, exclusively composed of Wolbachia from arthropods. For the current study, we took advantage of a recently developed DNA-enrichment method to produce four complete genomes and two draft genomes of Wolbachia from filarial nematodes. Two complete genomes, wCtub and wDcau, are the smallest Wolbachia genomes sequenced to date (863 988 bp and 863 427 bp, respectively), as well as the first genomes representing supergroup J. These genomes confirm the validity of this supergroup, a controversial clade due to weaknesses of the multilocus sequence typing approach. We also produced the first draft Wolbachia genome from a supergroup F filarial nematode representative (wMhie), two genomes from supergroup D (wLsig and wLbra) and the complete genome of wDimm from supergroup C. Our new data confirm the paradigm of smaller Wolbachia genomes from filarial nematodes containing low levels of transposable elements and the absence of intact bacteriophage sequences, unlike many Wolbachia from arthropods, where both are more abundant. However, we observe differences among the Wolbachia genomes from filarial nematodes: no global co-evolutionary pattern, strong synteny between supergroup C and supergroup J Wolbachia, and more transposable elements observed in supergroup D Wolbachia compared to the other supergroups. Metabolic pathway analysis indicates several highly conserved pathways (haem and nucleotide biosynthesis, for example) as opposed to more variable pathways, such as vitamin B biosynthesis, which might be specific to certain host–symbiont associations. Overall, there appears to be no single Wolbachia –filarial nematode pattern of co-evolution or symbiotic relationship.

中文翻译：

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小型、退化但不同：丝虫线虫的沃尔巴克氏体基因组不符合单一范式

Wolbachia 是α-变形菌共生体，可感染范围广泛的节肢动物物种和两个不同的线虫科。有趣的是，这些内共生体能够在宿主中诱导不同的表型：它们是许多节肢动物中的生殖寄生虫，一些昆虫中的营养共生者，以及它们的丝状线虫宿主中的专性共生者。定义Wolbachia 的“物种”是有争议的，因此它们通常分为 17 个不同的系统发育谱系，称为超群，命名为 A-F、H-Q 和 S。然而，可用的基因组数据仍然有限，不能代表完整的Wolbachia多样性；事实上，在Wolbachia的 24 个完整基因组和 55 个基因组草图中 迄今为止，84% 属于超群 A 和 B，完全由节肢动物的Wolbachia组成。对于当前的研究，我们利用最近开发的 DNA 富集方法从丝虫线虫中产生四个完整的基因组和两个Wolbachia基因组草图。两个完整的基因组w Ctub 和w Dcau 是迄今为止测序的最小Wolbachia基因组（分别为 863 988 bp 和 863 427 bp），以及代表超群 J 的第一个基因组。这些基因组证实了这个超群的有效性，一个由于多位点序列分型方法的弱点而引起争议的进化枝。我们还制作了第一稿Wolbachia 从一个超组˚F丝虫线虫代表（基因组瓦特MHIE），两个基因组从超组d（瓦特Lsig中和瓦特LBRA）和的完整基因组瓦特DIMM从超组C.我们的新数据确认较小的范例沃尔巴克氏体基因组从丝状线虫含低水平的转座因子和完整的噬菌体序列的缺失，这与节肢动物中的许多Wolbachia不同，后者两者都更丰富。然而，我们观察到丝虫线虫Wolbachia基因组之间的差异：没有全球共同进化模式，超群 C 和超群 J Wolbachia之间的强同线性， 与其他超群相比，在超群 D Wolbachia 中观察到更多的转座因子。代谢途径分析表明有几种高度保守的途径（例如血红素和核苷酸的生物合成），而不是更可变的途径，例如维生素 B 生物合成，后者可能对某些宿主-共生体关联具有特异性。总体而言，似乎没有单一的Wolbachia -丝虫线虫共同进化或共生关系模式。