Research article

Comparative genomics of vesicomyid clam (Bivalvia: Mollusca) chemosynthetic symbionts

Irene LG Newton^1,2*, Peter R Girguis¹ and Colleen M Cavanaugh¹

• * Corresponding author: Irene LG Newton garcia@fas.harvard.edu

Author Affiliations

¹ Harvard University, Organismic and Evolutionary Biology, 16 Divinity Avenue, Cambridge, MA 02138, USA

² Department of Microbiology, Tufts University, 136 Harrison Avenue, Boston, MA 02111, USA

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BMC Genomics 2008, 9:585 doi:10.1186/1471-2164-9-585

Published: 4 December 2008

Abstract

Background

The Vesicomyidae (Bivalvia: Mollusca) are a family of clams that form symbioses with chemosynthetic gamma-proteobacteria. They exist in environments such as hydrothermal vents and cold seeps and have a reduced gut and feeding groove, indicating a large dependence on their endosymbionts for nutrition. Recently, two vesicomyid symbiont genomes were sequenced, illuminating the possible nutritional contributions of the symbiont to the host and making genome-wide evolutionary analyses possible.

Results

To examine the genomic evolution of the vesicomyid symbionts, a comparative genomics framework, including the existing genomic data combined with heterologous microarray hybridization results, was used to analyze conserved gene content in four vesicomyid symbiont genomes. These four symbionts were chosen to include a broad phylogenetic sampling of the vesicomyid symbionts and represent distinct chemosynthetic environments: cold seeps and hydrothermal vents.

Conclusion

The results of this comparative genomics analysis emphasize the importance of the symbionts' chemoautotrophic metabolism within their hosts. The fact that these symbionts appear to be metabolically capable autotrophs underscores the extent to which the host depends on them for nutrition and reveals the key to invertebrate colonization of these challenging environments.