For the insect pathogen Photorhabdus luminescens, which end of a nematode is out?
For the insect pathogen Photorhabdus luminescens, which end of a nematode is out?
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DOI：
10.1128/aem.69.4.1890-1897.2003
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发表时间：
2003-04-01
影响因子：
4.4
通讯作者：
Ensign, JC
中科院分区：
文献类型：
--
作者：
Ciche, TA;Ensign, JC
细菌异小杆线虫是昆虫病原细菌发光小杆菌在昆虫幼虫间传播的媒介。Dauer juvenile（DJ）阶段线虫选择性地将发光假单胞菌保留在其肠道中，直到其将细菌释放到昆虫宿主的血腔中。我们报告了研究该细菌通过其线虫载体传播的结果。用绿色荧光蛋白标记的发光假单胞菌的细胞优先定殖在紧靠基底球后面的DJ肠的区域，向肛门延伸不同的距离。DJ线虫在昆虫血淋巴中的体外孵育引起细菌的反流。在30分钟的滞后之后，细菌以逐渐和交错的运动向口腔迁移并最终离开口腔。这种反流反应是由节肢动物血淋巴和昆虫细胞培养物上清液中存在的低分子量、热和蛋白酶稳定的阴离子成分引起的。用左旋咪唑麻醉或用抗蠕虫剂伊维菌素处理的线虫不会将其细菌释放到血淋巴中。在DJ线虫肠道中观察发光假单胞菌的能力为昆虫幼虫感染期间细菌释放的机制提供了第一条线索。这一点以及血淋巴中触发细菌释放的成分的部分特征，使这个互利共生和疾病传播的迷人例子适合未来的遗传和分子研究。
The nematode Heterorhabditis bacteriophora is the vector for transmitting the entomopathogenic bacterium Photorhabdus luminescens between insect larvae. The dauer juvenile (DJ) stage nematode selectively retains P. luminescens in its intestine until it releases the bacteria into the hemocoel of an insect host. We report the results of studying the transmission of the bacteria by its nematode vector. Cells of P. luminescens labeled with green fluorescent protein preferentially colonized a region of the DJ intestine immediately behind the basal bulb, extending for various distances toward the anus. Incubation of DJ nematodes in vitro in insect hemolymph induced regurgitation of the bacteria. Following a 30-min lag, the bacteria migrated in a gradual and staggered movement toward and ultimately exited the mouth. This regurgitation reaction was induced by a low-molecular-weight, heat- and protease-stable, anionic component present in arthropod hemolymph and in supernatants from insect cell cultures. Nematodes anesthetized with levamisole or treated with the antihelmenthic agent ivermectin did not release their bacteria into hemolymph. The ability to visualize P. luminescens in the DJ nematode intestine provides the first clues to the mechanism of release of the bacteria during infection of insect larvae. This and the partial characterization of a component of hemolymph triggering release of the bacteria render this fascinating example of both a mutualistic symbiosis and disease transmission amenable to future genetic and molecular study.