Role of Microorganisms in the Metabolism of Termites

Abstract

This article reviews the current knowledge of the role of symbiotic microorganisms in the metabolism of termites. The symbiotic microorganisms, comprising bacteria (higher and lower termites) and protozoa (lower termites) are in the hindgut. Cellulose digestion in higher termites appears to be mediated solely by cellulolytic enzymes secreted by the termites. In the lower termites, cellulose is digested by enzymes secreted both by the termites and by the protozoa. The end products of protozoal metabolism (acetate and butyrate) are thought to be used by termites as energy sources. Another method of cellulose digestion is that of the Macrotermitinae which have a symbiotic relationship with fungi of the genus Termitomyces. The termites acquire cellulase from the fungus. The bacteria found in the hindgut are usually facultative even though the hindgut is anaerobic. Some of these bacteria appear to be involved in dinitrogen-fixation in the gut, but do not play any part in cellulose metabolism. Some evidence suggests that termites may be able to re-utilize the nitrogen in the uric acid stores in their fat body using hindgut bacteria. While there is evidence that lignin can be degraded in termite tissues it is difficult to assess the role of the hindgut micro biota in this process.