Physical Proximity May Promote Lateral Acquisition of Bacterial Symbionts in Vesicomyid Clams

Type Article
Date 2013-07
Language English
Author(s) Decker Carole1, Olu KarineORCID1, Arnaud-Haond SophieORCID1, Duperron Sebastien2, 3
Affiliation(s) 1 : IFREMER, Ctr Brest, Lab Environm Profond, REM EEP, Plouzane, France.
2 : UPMC CNRS IRD MNHN, UMR Systemat Adaptat Evolut Adaptat Milieux Extre, Paris, France.
3 : Univ Paris 06, Paris, France.
Source Plos One (1932-6203) (Public Library Science), 2013-07 , Vol. 8 , N. 7 , P. -
DOI 10.1371/journal.pone.0064830
WOS© Times Cited 19
Abstract Vesicomyid clams harbor intracellular sulfur-oxidizing bacteria that are predominantly maternally inherited and co-speciate with their hosts. Genome recombination and the occurrence of non-parental strains were recently demonstrated in symbionts. However, mechanisms favoring such events remain to be identified. In this study, we investigated symbionts in two phylogenetically distant vesicomyid species, Christineconcha regab and Laubiericoncha chuni, which sometimes co-occur at a cold-seep site in the Gulf of Guinea. We showed that each of the two species harbored a single dominant bacterial symbiont strain. However, for both vesicomyid species, the symbiont from the other species was occasionally detected in the gills using fluorescence in situ hybridization and gene sequences analyses based on six symbiont marker genes. Symbiont strains co-occurred within a single host only at sites where both host species were found; whereas one single symbiont strain was detected in C. regab specimens from a site where no L. chuni individuals had been observed. These results suggest that physical proximity favored the acquisition of non-parental symbiont strains in Vesicomyidae. Over evolutionary time, this could potentially lead to genetic exchanges among symbiont species and eventually symbiont displacement. Symbiont densities estimated using 3D fluorescence in situ hybridization varied among host species and sites, suggesting flexibility in the association despite the fact that a similar type of metabolism is expected in all symbionts.
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