Abstract

Among associations between marine invertebrates and chemoautotrophic bacteria, one involves Lucinidae and sulfur-oxidizing intracellular symbionts. The genetic diversity of symbionts associated to Lucinidae was studied using sequencing of 16S rDNA (Durand and Gros 1996) and show six host species harboring the same bacterial species which is in discrepancy with the specific association hypothesis due to co-evolution between hosts and symbionts (Distel et al. 1994). So we sought to know if at intraspecific level it exist a strain diversity which could be structured within the bacterial species, in order to know if it really exist a specificity of association within Lucinidae or if the association is constituted function of the bacterial strain(s) present in the environment. Using a MLST (Multi Locus Sequence Typing) analysis, we analyzed species used by Durand and Gros (1996) and collected at the same sites. It appears that it exists different haplotypes which one specific to two host species (Codakia orbiculata and C. pectinella). This specificity is independent from the geographic localization; because two other host species colonizing sea-grass beds; and seems not constitute a phylotype, these two species being not the two phylogenetic most closely relative. So these results translate a specificity of association between these two species and this bacterial strain which could be due to: (i) environmental conditions where are retrieved these two hosts, or (ii) co-adaptation of these two hosts to this bacterial strain. Bibliographie DISTEL et al. (1994). Journal of Molecular Evolution 38:533-542. DURAND & GROS, (1996). FEMS Microbiological Letters 140 (2-3):193-198

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