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Here we report the complete genome sequence of Teredinibacter turnerae T7901. T. turnerae is a marine gamma proteobacterium that occurs as an intracellular endosymbiont in the gills of wood-boring marine bivalves of the family Teredinidae (shipworms). This species is the sole cultivated member of an endosymbiotic consortium thought to provide the host with enzymes, including cellulases and nitrogenase, critical for digestion of wood and supplementation of the host's nitrogen-deficient diet. T. turnerae is closely related to the free-living marine polysaccharide degrading bacterium Saccharophagus degradans str. 2-40 and to as yet uncultivated endosymbionts with which it coexists in shipworm cells. Like S. degradans, the T. turnerae genome encodes a large number of enzymes predicted to be involved in complex polysaccharide degradation (>100). However, unlike S. degradans, which degrades a broad spectrum (>10 classes) of complex plant, fungal and algal polysaccharides, T. turnerae primarily encodes enzymes associated with deconstruction of terrestrial woody plant material. Also unlike S. degradans and many other eubacteria, T. turnerae dedicates a large proportion of its genome to genes predicted to function in secondary metabolism. Despite its intracellular niche, the T. turnerae genome lacks many features associated with obligate intracellular existence (e.g. reduced genome size, reduced %G+C, loss of genes of core metabolism) and displays evidence of adaptations common to free-living bacteria (e.g. defense against bacteriophage infection). These results suggest that T. turnerae is likely a facultative intracellular ensosymbiont whose niche presently includes, or recently included, free-living existence. As such, the T. turnerae genome provides insights into the range of genomic adaptations associated with intracellular endosymbiosis as well as enzymatic mechanisms relevant to the recycling of plant materials in marine environments and the production of cellulose-derived biofuels.

Natural products (secondary metabolites) found in marine invertebrates are often thought to be produced by resident symbiotic bacteria, and these products appear to play a major role in the symbiotic interaction of bacteria and their hosts. In these animals, there is extensive variation, both in chemistry and in the symbiotic bacteria that produce them. Here, we sought to answer the question of what factors underlie chemical variation in the ocean. As a model, we investigated the colonial tunicate Lissoclinum patella because of its rich and varied chemistry and its broad geographic range. We sequenced mitochondrial cytochrome c oxidase 1 (COXI) genes, and found that animals classified as L. patella fall into three phylogenetic groups that may encompass several cryptic species. The presence of individual natural products followed the phylogenetic relationship of the host animals, even though the compounds are produced by symbiotic bacteria that do not follow host phylogeny. In sum, we show that cryptic populations of animals underlie the observed chemical diversity, suggesting that the host controls selection for particular secondary metabolite pathways. These results imply novel approaches to obtain chemical diversity from the oceans, and also demonstrate that the diversity of marine natural products may be greatly impacted by cryptic local extinctions. [ABSTRACT FROM AUTHOR]

Natural products (secondary metabolites) found in marine invertebrates are often thought to be produced by resident symbiotic bacteria, and these products appear to play a major role in the symbiotic interaction of bacteria and their hosts. In these animals, there is extensive variation, both in chemistry and in the symbiotic bacteria that produce them. Here, we sought to answer the question of what factors underlie chemical variation in the ocean. As a model, we investigated the colonial tunicate Lissoclinum patella because of its rich and varied chemistry and its broad geographic range. We sequenced mitochondrial cytochrome c oxidase 1 (COXI) genes, and found that animals classified as L. patella fall into three phylogenetic groups that may encompass several cryptic species. The presence of individual natural products followed the phylogenetic relationship of the host animals, even though the compounds are produced by symbiotic bacteria that do not follow host phylogeny. In sum, we show that cryptic populations of animals underlie the observed chemical diversity, suggesting that the host controls selection for particular secondary metabolite pathways. These results imply novel approaches to obtain chemical diversity from the oceans, and also demonstrate that the diversity of marine natural products may be greatly impacted by cryptic local extinctions. [ABSTRACT FROM AUTHOR]