Almost there: transmission routes of bacterial symbionts between trophic levels.
Almost there: transmission routes of bacterial symbionts between trophic levels.
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DOI：
10.1371/journal.pone.0004767
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发表时间：
2009
期刊：
影响因子：
3.7
通讯作者：
Hunter MS
中科院分区：
文献类型：
--
作者：
Chiel E;Zchori-Fein E;Inbar M;Gottlieb Y;Adachi-Hagimori T;Kelly SE;Asplen MK;Hunter MS
节肢动物的许多细胞内微生物共生体严格垂直传播，并以增强自身传播的方式操纵宿主的繁殖。尽管如此，罕见的水平传播事件对于共生体传播到新的寄主谱系是必要的。水平传播主要是从系统发育研究中推断出来的，但传播机制在很大程度上仍然是一个谜。本文研究了两种亲缘关系较远的细菌共生体立克次体和哈密通体从它们的宿主——甘薯粉虱，烟粉虱——到三种拟白蝇的传播：埃米尔白蝇，Eretmocerus eremicus和pergandiella Encarsia。我们还研究了这些白蝇共生体在寄生蜂世代之间垂直传播的可能性。利用荧光原位杂交（FISH）和透射电镜技术，我们发现立克次体在立克次体感染宿主的发育过程中侵入伊雷螨幼虫，在成虫和雌虫中持续存在，并到达卵巢。然而，立克次体似乎不穿透卵母细胞，而是局限于滤泡上皮细胞。因此，立克次体不是垂直传播的埃氏马蜂，结果支持诊断聚合酶链反应（PCR）。相比之下，立克次体在恩卡西亚的消化道中只是短暂的，并在黄蜂化蛹之前随粪排出体外。这三种拟寄生物的成虫经常通过与受感染的白蝇接触而感染立克次体，最有可能是通过取食宿主的血淋巴（宿主取食），但在将黄蜂从受感染的白蝇身上移走后的几天内，感染率急剧下降。与立克次体相比，哈密通体没有在任何被试的拟寄生虫中建立，并且没有寄生蜂通过寄主摄食获得哈密通体。本研究展示了共生体跨营养水平传播的潜在途径和障碍。讨论了导致共生体物种在宿主物种间传播差异的可能机制。
Many intracellular microbial symbionts of arthropods are strictly vertically transmitted and manipulate their host's reproduction in ways that enhance their own transmission. Rare horizontal transmission events are nonetheless necessary for symbiont spread to novel host lineages. Horizontal transmission has been mostly inferred from phylogenetic studies but the mechanisms of spread are still largely a mystery. Here, we investigated transmission of two distantly related bacterial symbionts – Rickettsia and Hamiltonella – from their host, the sweet potato whitefly, Bemisia tabaci, to three species of whitefly parasitoids: Eretmocerus emiratus, Eretmocerus eremicus and Encarsia pergandiella. We also examined the potential for vertical transmission of these whitefly symbionts between parasitoid generations. Using florescence in situ hybridization (FISH) and transmission electron microscopy we found that Rickettsia invades Eretmocerus larvae during development in a Rickettsia-infected host, persists in adults and in females, reaches the ovaries. However, Rickettsia does not appear to penetrate the oocytes, but instead is localized in the follicular epithelial cells only. Consequently, Rickettsia is not vertically transmitted in Eretmocerus wasps, a result supported by diagnostic polymerase chain reaction (PCR). In contrast, Rickettsia proved to be merely transient in the digestive tract of Encarsia and was excreted with the meconia before wasp pupation. Adults of all three parasitoid species frequently acquired Rickettsia via contact with infected whiteflies, most likely by feeding on the host hemolymph (host feeding), but the rate of infection declined sharply within a few days of wasps being removed from infected whiteflies. In contrast with Rickettsia, Hamiltonella did not establish in any of the parasitoids tested, and none of the parasitoids acquired Hamiltonella by host feeding. This study demonstrates potential routes and barriers to horizontal transmission of symbionts across trophic levels. The possible mechanisms that lead to the differences in transmission of species of symbionts among species of hosts are discussed.
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