Wolbachia as a bacteriocyte-associated nutritional mutualist
Wolbachia as a bacteriocyte-associated nutritional mutualist
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DOI：
10.1073/pnas.0911476107
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发表时间：
2010-01-12
影响因子：
11.1
通讯作者：
Fukatsu, Takema
中科院分区：
文献类型：
--
作者：
Hosokawa, Takahiro;Koga, Ryuichi;Fukatsu, Takema
许多昆虫依赖于细菌共生体提供必需的营养素（例如，蚜虫-布赫内拉和舌蝇-Wiglesbiaassociations），其中共生体被窝藏在构成共生器官细菌组的称为细菌细胞的特定细胞中。像沃尔巴克氏体这样的兼性和寄生性细菌共生体被认为在进化上与这种专性营养互惠共生体不同。然而，我们发现，在臭虫Cimex lectularius中，Wolbachia存在于细菌组中，似乎是一种专性营养互利主义者。从不同的臭虫菌株中鉴定出两种细菌共生体，一种是沃尔巴克氏体菌株，另一种是未命名的γ-变形杆菌。Wolbachia共生体被检测到从所有的昆虫检查，而γ-变形杆菌被发现在其中的一部分。Wolbachia共生体特异性地定位于细菌组中，并通过胚芽的体细胞干细胞龛垂直传播到卵母细胞，在胚胎发生的早期阶段感染初始的共生器官。消除沃巴赫菌共生体导致宿主昆虫生长迟缓和不育。这些缺陷通过口服补充B族维生素而得到补救，证实了共生体对宿主的重要营养作用。估计共生体的基因组大小约为1.3 Mb，这几乎相当于其他昆虫的寄生Wolbachia菌株的基因组大小。这些结果表明，细菌细胞相关的营养互惠共生可以从兼性和普遍的微生物协会，如沃尔巴克氏体，突出了一个以前未知的方面的寄生互惠共生进化连续体。
Many insects are dependent on bacterial symbionts that provide essential nutrients (ex. aphid-Buchnera and tsetse-Wiglesworthia associations), wherein the symbionts are harbored in specific cells called bacteriocytes that constitute a symbiotic organ bacteriome. Facultative and parasitic bacterial symbionts like Wolbachia have been regarded as evolutionarily distinct from such obligate nutritional mutualists. However, we discovered that, in the bedbug Cimex lectularius, Wolbachia resides in a bacteriome and appears to be an obligate nutritional mutualist. Two bacterial symbionts, a Wolbachia strain and an unnamed gamma-proteobacterium, were identified from different strains of the bedbug. The Wolbachia symbiont was detected from all of the insects examined whereas the gamma-proteobacterium was found in a part of them. The Wolbachia symbiont was specifically localized in the bacteriomes and vertically transmitted via the somatic stem cell niche of germalia to oocytes, infecting the incipient symbiotic organ at an early stage of the embryogenesis. Elimination of the Wolbachia symbiont resulted in retarded growth and sterility of the host insect. These deficiencies were rescued by oral supplementation of B vitamins, confirming the essential nutritional role of the symbiont for the host. The estimated genome size of the Wolbachia symbiont was around 1.3 Mb, which was almost equivalent to the genome sizes of parasitic Wolbachia strains of other insects. These results indicate that bacteriocyte-associated nutritional mutualism can evolve from facultative and prevalent microbial associates like Wolbachia, highlighting a previously unknown aspect of the parasitism-mutualism evolutionary continuum.