Termites have a symbiotic relationship with Protozoa of the Genus Trichonympha, belonging to the Phylum Parabasalia. The termite by itself could not break down the cellulose in the wood that it ingests since it does not produce enzymes to do this.  To overcome this problem the termite has built this symbiotic relationship with the Trichonympha.  The Trichonympha produces enzymes that break down the wood ingested by the termite. In turn, the Trichonympha benefit from the energy they gain from the steady supply of cellulose provided by the termite. 

If the termites did not have the aid of the Trichonympha they would be filled with cellulose they could not digest and die.  This is due to the fact that sugars cannot be extracted from the wood until the Trichonympha has first extracted the cellulose.  This is one of the marvels of nature.  Although how this relationship first began is relatively unknown, without it this termite would not be able to survive.