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All of the animals (including the human) shown above have a symbiotic relationships with bacteria. The digestive-tract of the medicinal leech, Hirudo verbana, is simple in comparison to other animals and dominated by Aeromonas veronii biovar sobria and a Rikenella-like bacterium. This simplicity provides the opportunity to investigate the interaction of the partners. Some animals have special organs where they house the symbionts. A well-studied example is the Hawaiian squid, Euprymna scolopes. The symbiotic bacteria, Vibrio fischeri, produce light and are housed in a light organ. The light produced by the bacteria is used by the squid to camouflage themselves. Other symbioses are so intimate that the symbionts live inside the host cells. An example of this is the symbiosis of Aphids, Aphidoidea. The genomes of the symbionts from the aphid and squid have been sequenced.

Click on the picture to find out more information about these symbioses:

Link
Symbiont

Aeromonas veronii

Rikenella-Like Bacteria

Vibrio fischeri Buchnera Species Xenorhabdus nematophilus
Host Hirudo verbana Euprymna scolopes Aphidiodea Steinernema carpocapsae
Type Diestive-Tract Symbiosis Light Organ Symbiosis Nutritional Symbiosis Digestive-Tract Symbiosis
Location Extracellular Extracellular Intracellular Extracellular
Function Unknown Light Production Amino Acid Synthesis Digestion of insect host

For each symbiosis, there is a general introductory paragraph, followed by information on the current research and certain other aspects that we find exciting. Direct links to the home pages of investigators are provided, where you can find out more information about them, their research interests, and how to contact them. The reference section lists recent reviews and selected research articles, often with links to the abstract or the online articles.
For a general introduction to the subject of symbiosis and some general articles and links click on symbiosis. Another useful resource is the website from the International Symbiosis Society.

We are continuously improving and updating this site. If you have comments, corrections, links, or suggestions, please send them to us. We are gradually adding descriptions of other symbioses, so come back and visit again.

If your favorite symbiosis is missing, please send us information, pictures, publications and links to the homepages of the investigators.

We would like to express our thanks to the investigators / authors / photographers who have permitted us to use their images. Please do not use any of the images without prior permission.

This web site has been created by Joerg Graf from the Department of Molecular and Cell Biology at the University of Connecticut and Elaine S. Mirkin, a free-lance writer in Willington, CT. We began working on this web site at the Institute for Infectious Diseases of the University of Berne.