Composition and Function of a Novel Consortial Endosymbiosis in the Shipworm Lyrodus pedicellatus.

University Of Maine, Orono ME

Investigators

Abstract

Enormous quantities of wood and other woody plant materials (including leaves, bark, shoots, stems and nuts) are produced annually in the environment. In fact, cellulose, the major component of woody materials, is thought to be the most abundant biological material on earth. This remarkably strong and enduring molecule is a polymer of glucose (sugar) linked by a type of chemical bond that makes it indigestible to most living organisms. Therefore, this rich source of food energy is available to only a few animals (e.g., termites and ruminants) that can digest cellulose with the aid of microbes living in their guts. Surprisingly, some marine animals can also digest wood. The most important group is the wood-boring clams, commonly known as shipworms. Unlike termites and ruminants, these animals lack microorganisms in their gut. Instead they harbor enormous numbers of symbiotic bacteria inside the cells of their gills. These bacteria fall into at least four closely related families based on DNA analyses. The PIs have proposed that these bacteria produce cellulolytic enzymes that are transported from the gills to the gut. The purpose of this investigation is to explore the diversity and distribution of symbiont types in the shipworm gills, to determine if each symbiont type contributes different cellulolytic enzymes, and to discover how the host uses these bacterial products to exploit cellulose as a food source. These investigations should result in the discovery of new cellulolytic enzymes that may have industrial applications in such areas as paper and textile processing and fuel (ethanol) production via biomass conversion of agricultural wastes. These efforts will also help the PIs to understand the physiology of symbiotic bacterial infections that are beneficial rather than harmful to their hosts.