Endosymbiotic gamma-proteobacteria act as energy transformer inside the trophosome of the tubeworm Lamellibrachia satsuma

Abstract

Vestimentiferan tubeworms Lamellibrachia satsuma is a common member of faunal communities in the Kagosima Bay. Endosymbiotic bacteria are living inside a specialized tissue called the trophosome. In this study, the trophosome content from the tubeworm was sequenced by Illumina HiSeq 2000. Data assembled by SOAP de novo were submitted to the IMG/MER for annotation. Metagenomic analysis suggests that they harbor mostly γ-proteobacterial endosymbiont contain all genes required for oxidizing reduced sulfur compounds mediated through the cytoplasmic enzyme adenylylsulfate reductase (AprA/AprB). Surprisingly, the endosymbiont harbors genes for two different carbon fixation pathways, the Calvin cycle as well as the rTCA cycle, as has been reported in the endosymbiont of the various tubeworms from hydrothermal vent and cold seep. This study suggests that, endosymbiont uptake inorganic material supplied by tubeworm and transform in to organic compounds which fulfil the energy requirement of the tube worm.