The Termite-Symbionts System

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The termites, who have symbiotic relationship with bacteria, protozoa and fungi, have succeeded in utilizing cell-wall component of dead plants, which contains cellulose, the most abundant organic matter on the earth, but contains only a little nitrogen.The present international cooperative research project intends to clarify the "Termite-Symbionts System" with special reference to (1) cellulose decomposition process and nitogen acquisition, (2) environmental factors and ecological traits of termites promoting the macroevolution in termites from lower to higher termites, and (3) the role of termites in nitrogen flow of terrestrial ecosystems in Thailand, Australia and Japan. Most important questions and answers are as follows.1) Why are xylophagous termites able to subsist on a diet containing very little nitrogen? Thirty to fifty percent of nitrogen of bodies of a xylophagous termite (Neotermes koshunensis, Kalotermitidae) come from atmospheric nitrogen.2) Who produce cellulases? In lower termites (Reticulitermes speratus) cellulases are produced by protozoa (in hind gut) and by themselves (in salivary gland and midgut), while in higher termites cellulases are produced by themselves (in midgut).3) Who decompose hemicellulose? In a lower termite (Reticulitermes speratus), enzymes to decompose hemicellulose are produced by protozoa and termites themselves.4) What kind of factors have promoted the macroevolution in termites? Based on comparative studies on biology of termites in reinforests and adjacent Eucalyptus savanna in Australia, 'Lignin cover hypothesis' was proposed, suggesting the importance of climatic change in Cretaceous period (moist to dry) as well as the change in nest site and food of termites.