Cellulose and Xylan Utilisation in the Lower Termite Reticulitermes speratus.

ABSTRACT

The distribution of the enzymes of cellulose and xylan metabolism namely endo-beta-1,4-glucanase, beta-glucosidase, endo-beta-1,4-xylanase and beta-xylosidase activities, in Reticulitermes speratus (Kolbe) was measured both in the salivary glands and in the major gut sections and along the length of the gut in freshly collected termites. The majority of the endo-beta-1,4-glucanase activity (77.8%) was found in the salivary glands which also contained 23.9% of the beta-glucosidase activity. At least 70% of the remaining activity was located in the anterior section of the hindgut. A small amount of endo-beta-1,4-xylanase activity (2.4%), but no beta-xylosidase activity, was present in the salivary glands. The majority of these activities were in the anterior section of the hindgut. The RQ of freshly collected termites at 25 degrees C was 1.03+/-0.01. Maintaining termites for 16 days on wood, cellulose and xylan showed that the RQ values of termites fed on wood or xylan were not significantly different from those of freshly collected termites but significantly increased when maintained on cellulose. The RQ of starved termites after 11 days was 0.81+/-0.02. There were three effects on protozoan populations of feeding termites xylan for 20 days. One species, Dinenympha parva was not affected, while five others, Pyrsonympha grandis, Holomastigotes elongatum, Dinenympha rugosa, Dinenympha leidy and Dinenympha porteri survived for 20 days but slowly decreased in numbers. The numbers of P. grandis and D. leidy surviving for 20 days were significantly different from those in starved termites. The third group comprising the two large species, Teratonympha mirabilis and Trichonympha agilis and three small species, Pyrsonympha modesta, Dinenympha exilis and Dinenympha nobilis disappeared within 15 days as in starved termites. It is suggested that protozoa in the first two groups are xylanolytic. Protozoan populations on wood and cellulose diets were not markedly affected. Selective removal of the protozoa by u.v. irradiation led to the loss of xylanolytic activity and a life span comparable to starved termites. Copyright 1997 Elsevier Science Ltd. All rights reserved