Featured Project:Wood-eating clams fuel energy and cancer research.
As fuel prices and global temperatures steadily increase, researchers are intensifying their search for renewable energy alternatives. One promising avenue of research (bioconversion) seeks to convert cellulose, a major component of domestic and agricultural wastes, into ethanol, a fuel that can supplement or replace fossil fuels used in cars and trucks. A critical part of this research is the search for new and better cellulases, the enzymes that convert cellulose into sugar which in turn is fermented to ethanol. Researchers at the Ocean Genome Legacy are turning to an unlikely source for such enzymes: marine clams that eat wood!
The shipworm, Lyrodus pedicellatus, is an ideal candidate in this search. Although it looks like a worm, It is actually a worm-like marine clam, closely related to New England's beloved "steamer clam", Mya arenaria. Unlike its steamer clam cousin, however, shipworms can live on a diet composed solely of wood! This unusual diet is made possible by bacterial symbionts that live inside cells of a specialized organ within its gills. The bacteria make enzymes that convert cellulose, which is indigestible to most animals, into glucose, a sugar that is easly used by all animals and also easily fermented to ethanol.
One of theses symbionts is called Teredinibacter turnerae. This bacterium can be grown in the laboratory and is the subject of intense scrutiny at OGL. One important project, currently underway, seeks to clone an unusual cellulase enzyme from T. turnerae and to overproduce it in an alternate host. Now cloned and purified, this enzyme is being tested for its potential utility for converting cellulose to sugar on an industrial scale.
A second project involving T. turnerae, seeks to determine the complete nucleotide sequence of the T. turnerae genome. Although not yet completely sequenced, this genome appears to be about half the size of the common human symbiont and pathogen, E. coli. Already over a dozen candidate genes for pathways that involve cellulose degradation, have been identified in T. turnerae, and await exploration. We expect this genome to bear other fruit as well, including insights into mechanisms of infection and the evolution of intracellular symbiosis. The T. turnerae genome may also contribute to cancer research. Dr. Margo Haygood, one of OGL's many collaborators on this project, has identified potential Bryostatin genes in T. turnerae. Bryostatins, are potential anticancer agents first identified in an unculturable symbiont of a very different marine invertebrate, the bryozoan, Bugula neritina. Dr. Haygood hopes to determine if T. turnerae can indeed produce Bryostatin, and whether its production in a culturable bacterium could improve its chances to be developed as a successful theraputic agent.
The shipworm genomics projects demonstrate that the genomes of marine organisms can contain many unexpected treasures and that such treasures are often found in the most unpredictable species. Who would guess that a clam that eats wood might hold keys to energy production and cancer therapy? This work underscores the fact that we must make every effort to protect, preserve, study and share the valuable, but highly threatened, genomic diversity of the oceans, and that no species may be too insignificant to warrant our interest and concern.
