Faculty of Agriculture, Kyushu University, 744 Motooka, Fukuoka, 819-0395, Japan.
Department of Bacteriology, Faculty of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan.
Microb Ecol. 2021 Aug;82(2):512-522. doi: 10.1007/s00248-021-01686-y. Epub 2021 Jan 16.
Intracellular bacteria that are mainly transmitted maternally affect their arthropod hosts' biology in various ways. One such effect is known as cytoplasmic incompatibility (CI), and three bacterial species are known to induce CI: Wolbachia, Cardinium hertigii, and a recently found alphaproteobacterial symbiont. To clarify the taxonomic status and provide the foundation for future studies to reveal CI mechanisms and other phenotypes, we investigated genetic and morphological properties of the third CI inducer that we have previously reported inducing CI in the coconut beetle Brontispa longissima. The draft genome of the bacteria was obtained from the oocytes of two isofemale lines of B. longissima infected with the bacteria: one from Japan (GL2) and the other from Vietnam (L5). Genome features of the symbionts (sGL2 and sL5) were highly similar, showing 1.3 Mb in size, 32.1% GC content, and 99.83% average nucleotide sequence. A phylogenetic study based on 43 universal and single-copy phylogenetic marker genes indicates that they formed a distinct clade in the family Anaplasmataceae. 16S rRNA gene sequences indicate that they are different from the closest known relatives, at least at the genus level. Therefore, we propose a new genus and species, "Candidatus Mesenet longicola", for the symbionts of B. longissima. Morphological analyses showed that Ca. M. longicola is an intracellular bacterium that is ellipsoidal to rod-shaped and 0.94 ± 0.26 μm (mean ± SD) in length, and accumulated in the anterior part of the oocyte. Candidates for the Ca. M. longicola genes responsible for CI induction are also described.
主要通过母系传播的细胞内细菌以各种方式影响其节肢动物宿主的生物学。其中一种效应称为细胞质不亲和性 (CI)，已知有三种细菌会诱导 CI：沃尔巴克氏体、Cardinium hertigii 和最近发现的α变形菌共生体。为了澄清分类地位，并为未来研究揭示 CI 机制和其他表型提供基础，我们研究了我们之前报道过的在椰子象甲 Brontispa longissima 中诱导 CI 的第三种 CI 诱导物的遗传和形态特征。细菌的基因组草图是从感染细菌的两个 Brontispa longissima 同雌系线的卵母细胞中获得的：一个来自日本 (GL2)，另一个来自越南 (L5)。共生体 (sGL2 和 sL5) 的基因组特征非常相似，大小为 1.3 Mb，GC 含量为 32.1%，平均核苷酸序列为 99.83%。基于 43 个通用和单拷贝系统发育标记基因的系统发育研究表明，它们在立克次体科中形成了一个独特的分支。16S rRNA 基因序列表明，它们与最接近的已知亲缘关系至少在属级水平上不同。因此，我们为 B. longissima 的共生体提出了一个新的属和种，“Candidatus Mesenet longicola”。形态分析表明，Ca. M. longicola 是一种细胞内细菌，呈椭圆形到杆状，长 0.94 ± 0.26 μm（平均值 ± SD），并在卵母细胞的前部分积累。还描述了候选的 Ca. M. longicola 基因，这些基因负责诱导 CI。
