March 15, 2000-February 29, 2004
Level of Access
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
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.
Distel, Daniel L., "Composition and Function of a Novel Consortial Endosymbiosis in the Shipworm Lyrodus pedicellatus" (2003). University of Maine Office of Research and Sponsored Programs: Grant Reports. 117.