Termites, cellulose digestion

Glycogen and starch ingested in the diet are hydrolyzed by a-amylases, enzymes in saliva and intestinal secretions that break (al—>4) glycosidic bonds between glucose units. Most animals cannot use cellulose as a fuel source, because they lack an enzyme to hydrolyze the (fil—>4) linkages. Termites readily digest cellulose... 

Termites digest glucose produced by cellulose-digesting microorganisms living in the termites digestive tract. 

As termites relentlessly digest cellulose (wood) throughout the world, they produce methane gas, which enters the atmosphere. Although now present in comparatively small amounts, methane is counted as one of the greenhouse gases. 

Termites without cellulose-digesting bacteria cannot survive. Antibiotics will kill termites. 

Notice another thing about cellulose and starch. The only way they differ is in how the glucose units are attached to each other. This minor change makes the difference between a potato and a tree. (Okay, it s not quite that simple.) Human beings can digest (metabolize) starches but not cellulose. A termite can digest cellulose just fine. In natural polymers, just like in synthetic ones, a minor change sometimes makes a big difference in the properties of the polymer. 

So far no significant evidence of cellulose digestion by bacteria has been found in termites which contain protozoans, and Baldacci could not demonstrate cellulolytic bacteria in defaunated termites. 

Termites can eat wood because they contain specific microorganisms that, in turn, contain bacteria that actually digest the wood. These bacteria have enzymes that can break the bonds of cellulose. 

Humans and other mammals lack the /3-glucosidase enzyme needed to hydrolyze cellulose, so they cannot use it directly for food. Several groups of bacteria and protozoa can hydrolyze cellulose, however. Termites and ruminants maintain colonies of these bacteria in their digestive tracts. When a cow eats hay, these bacteria convert about 20% to 30% of the cellulose to digestible carbohydrates. 

The >3(1 — 4) linkage is particularly stable with respect to hydrolysis. Cellulose cannot be digested by mammals, but some insects (notably termites and wood-eating cockroaches), protozoans and fungi possess celluloses, enzymes that can hydrolyze the /3(1—>4) linkages. Ruminants, such as sheep and cattle, can digest cellulose because of the protozoans that live symbiotically in their digestive system. 

Nitrogen fixation also occurs within the digestive tracts of some animals (as termites). The fixation of nitrogen in organisms that primarily consume nitrogen-free cellulose is especially important for the formation of proteins. Ammonia is assimilated into amino acids that are then polymerized into proteins. 

CelluiO >e molecules tend to be straight chains, and the fibers which result from collections of cellulose molecules have the strength to form the supporting structures of plants. Even though human digestion carmot break down cellulose for use as a food, animals such as cattle and termites rely on the energy content of cellulose. They have protozoa and bacteria with the necessary enzymes in their digestive systems. Cellulose in the human diet is needed for fibre. 

For the same reason it is difficult to prepare vaccines against them. Other flagellates live in a symbiotic relationship within the alimentary canals of termites (Fig. 1-9) and roaches. Termites depend upon bacteria that live within the cells of these symbiotic protozoans to provide the essential enzymes needed to digest the cellulose in wood. 

Cellulose, the structural biopolymer found in plants, contains the 1,4-linkage of glucose units. Our digestive systems are incapable of breaking the 8-1,4-linkage, so we cannot utilize cellulose as a source of stored glucose. Some animals such as termites and cattle are able to digest cellulose. 

Bacteria in the digestive tracts of termites and cattle produce an enzyme that allows them to digest the cellulose in wood and... 

The ability to digest cellulose is found only in microorganisms that possess the enzyme cellulase. Certain animal species (e.g., termites and cows) use such organisms in their digestive tracts to digest cellulose. The breakdown of the cellulose... 

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