日本产业技术综合研究所在《美国国家科学院学报》网络版上报告说，他们发现臭虫必须与一种寄生细菌共生，才能正常生长和繁殖。这项成果将帮助人们防治臭虫。

从20世纪20年代起就有一些报告称，臭虫的精巢或卵巢附近有一种特殊细胞群，里面的细胞内存在大量细菌。产业技术综合研究所的研究人员以生长在日本和澳大利亚的105只臭虫为研究对象，解剖它们精巢或卵巢附近的上述细胞群，并进行基因测试，结果发现了名为尖音库蚊沃尔巴克氏体的寄生细菌基因。研究人员说，这说明105只臭虫体内都有这种寄生细菌。

研究人员除去这些臭虫体内的尖音库蚊沃尔巴克氏体，然后让它们以吸食混入抗生物质的血液为生，结果这些臭虫的卵的孵化率急剧下降，即便孵化出幼虫，也都不能发育为成虫。这表明，感染尖音库蚊沃尔巴克氏体对臭虫的正常生长和繁殖非常重要。

那么，尖音库蚊沃尔巴克氏体到底为臭虫提供了什么东西呢？臭虫以脊椎动物的血液为生。血液看似营养丰富，实际上却缺乏昆虫所必需的B族维生素。研究人员发现，在喂食臭虫的血液中添加B族维生素，这样即使臭虫体内的尖音库蚊沃尔巴克氏体被清除，臭虫照样能够正常发育。

大约60％至70％的昆虫体内都寄生着尖音库蚊沃尔巴克氏体，而这次研究是人们首次发现这种寄生细菌与臭虫有互利共生关系。研究人员指出，今后可以研制通过消除尖音库蚊沃尔巴克氏体来防治臭虫的方法。

原始出处：

PNAS December 22, 2009, doi: 10.1073/pnas.0911476107

Wolbachia as a bacteriocyte-associated nutritional mutualist

Takahiro Hosokawa, Ryuichi Koga, Yoshitomo Kikuchi, Xian-Ying Meng and Takema Fukatsu1

National Institute of Advanced Industrial Science and Technology (AIST), Tsukuba 305-8566, Japan

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 γ-proteobacterium, were identified from different strains of the bedbug. The Wolbachia symbiont was detected from all of the insects examined whereas the γ-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.