This Article Full Text Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Reprints and Permissions Copyright Information Books from ASM Press MicrobeWorld Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Ciche, T. A. Articles by Ensign, J. C. Search for Related Content PubMed PubMed Citation Articles by Ciche, T. A. Articles by Ensign, J. C. Agricola Articles by Ciche, T. A. Articles by Ensign, J. C.

 Previous Article  |  Next Article 

Applied and Environmental Microbiology, April 2003, p. 1890-1897, Vol. 69, No. 4
0099-2240/03/$08.00+0     DOI: 10.1128/AEM.69.4.1890-1897.2003
Copyright © 2003, American Society for Microbiology. All Rights Reserved.

For the Insect Pathogen Photorhabdus luminescens, Which End of a Nematode Is Out?

Todd A. Ciche and Jerald C. Ensign^*

Department of Bacteriology, University of Wisconsin—Madison, Madison, Wisconsin 53706

Received 25 July 2002/ Accepted 17 December 2002

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.

Present address: Hopkins Marine Station of Stanford University, Pacific Grove, CA 93950.