The XVIIIth (New) International Congress of Zoology
Le XVIIIème (Nouveau) Congrès International de Zoologie
ATHENS, GREECE
28 August - 2 September 2000
The symposium on symbiosis (B8) is devoted to the presentation of different models of symbiotic associations, and their role in physiology and especially evolution of organisms. The association host/symbiotes creates a new biological unit, the symbiocosm, itself submitted to natural selection.
Different types of associations exist. The symbiotes can be outside (ectosymbiosis) or inside the host in the intestine or in some invaginations of the tegument (endosymbioses), or inside the cells (endocytobioses). In integrated symbioses the symbiote (a bacterium) is perfectly controlled by the host (location and number), and look likes a new cell organelle, only transmitted to the progeny by the mother. In other cases the symbiote is not perfectly controlled and invade most cells (Wolbachia), but not all the host population. Six models will be presented: in the Squid-Vibrio model (extracellular symbiosis), the bacterium is transmitted horizontally, or cyclically, and can be grown in vitro. The colonization of the luminous organ modifies this one. There are processes of recognition and specificity. Another endosymbiosis is the termite symbiosis. The gut lumen harbours protozoa and/or bacteria. They help the digestion. Transmission is horizontal. A coevolution host/symbiotes is highly probable.
Among endocytobioses the first model will be a protozoan, the amoebae, living symbiotically with a bacterium. The formation of the symbiosis has been observed in the laboratory: the bacterium which was firstly a parasite, has coevolved with the host cell so that to become obligate. We have the story of an integration. The role of symbiote in co-evolution is also spectacular with the Wolbachia model, a bacterium associated with a lot of insects and other invertebrates.
An integrated and obligate symbiosis in insect will be presented with the aphid model. The changes of the symbiotic bacterium during symbiosis are spectacular (notably the reduction of the genome). Furthermore, for the 1st time, this prokaryotic genome has been sequenced. The first conclusions, at the molecular level, will be communicated. A last model is the weevil (Coleoptera), where symbiosis is perfectly integrated, but surprisingly not always obligate. The comparison of symbiotic and aposymbiotic (= without symbiotes) strains allows to appreciate the exact role of symbiosis. The symbiocosm is there controlled by interactions of four different genomes: nuclear, mitochondrial and symbiotic ones (principal endocytobiotes and Wolbachia).
Symbioses appear as important factors of evolution. Symbiology must be recognized as an important field of zoology, botany and genetics.
What about a weevil's symbiocosm and its four intracellular genomes?
Dr. Abdelaziz Heddi
Institut National des Sciences Appliquée de Lyon, France
Characteristic features of the genome of an aphid endosymbiotic bacterium, Buchnera
Dr. Hajime Ishikawa
Department of
Biological Sciences, University of Tokyo, Tokyo, Japan
Integration of bacterial endosymbionts in amoebae
Dr. Kwang W. Jeon
Department of
Biochemistry, University of Tennessee, Knoxville, TN, USA
Evolving with a prokaryotic partner: Insight from the squid/vibrio model system
Dr. M. McFall-Ngai
Pacific Biomedical Research Center, University of Hawaii, HI, USA
Wolbachia: symbionts as reproductive parasites
Dr. Kostas Bourtzis
Institute of Molecular Biology and Biotechnology, Greece
Gut symbiosis in Isoptera
Dr. Corinne Rouland-Lefevre
Institut de recherche pour le développment - Laboratoire de Microbiologie, Dakar, Sénégal
POSTER CONTRIBUTIONS
Bacterial Endocytobionts of Paramecium
S. I. Fokin
How Patterns of Ants-Aphids Interactions Are Shaping in Early Development of Ants' Behaviour
T. Novgorodova
Experimental Study of Ants' Inter-Relations with Symbionts and Competitors at the Individual Level
Z. Reznikova, T. Novgorodova, E. Dorosheva, S. Panteleeva and E. Sleptzova