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

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Enormous quantities of wood and other woody plant materials(including leaves, bark, shoots, stems and nuts) are produced annually inthe environment. In fact, cellulose, the major component of woodymaterials, 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 tomost living organisms. Therefore, this rich source of food energy isavailable to only a few animals (e.g., termites and ruminants) that candigest cellulose with the aid of microbes living in their guts. Surprisingly, some marine animals can also digest wood. The mostimportant group is the wood-boring clams, commonly known as shipworms. Unliketermites and ruminants, these animals lack microorganisms in their gut.Instead they harbor enormous numbers of symbiotic bacteria inside the cellsof their gills. These bacteria fall into at least four closely relatedfamilies based on DNA analyses. The PIs have proposed that these bacteriaproduce cellulolytic enzymes that are transported from the gills to thegut. The purpose of this investigation is to explore the diversity anddistribution of symbiont types in the shipworm gills, to determine if eachsymbiont type contributes different cellulolytic enzymes, and to discoverhow the host uses these bacterial products to exploit cellulose as a foodsource. These investigations should result in the discovery of newcellulolytic enzymes that may have industrial applications in such areas aspaper and textile processing and fuel (ethanol) production via biomassconversion of agricultural wastes. These efforts will also help the PIs tounderstand the physiology of symbiotic bacterial infections that arebeneficial rather than harmful to their hosts.