THE EFFECT OF CARBOHYDRATES ON THE EXPRESSION OF THE PREVOTELLA-RUMINICOLA 1,4-BETA-D-ENDOGLUCANASE

The beta-1,4-endoglucanase of the ruminal bacterium, Prevotella rumini cola B(1)4, hydrolysed carboxymethylcellulose and barley glucan but no t xylan or mannan. Endoglucanase activity was present in 88- and 82-kD a proteins, and there was at least a 20-fold variation in endoglucanas e activity when P. ruminicola B(1)4 was grown on different sugars. The highest activities were observed with mannose, cellobiose or xylose a nd little activity was observed with sucrose, arabinose or rhamnose. P . ruminicola B(1)4 also had significant xylanase and mannanase activit ies, but these activities were present in proteins that had lower mole cular masses than the endoglucanase and these proteins did not cross-r eact with antibody made against the endoglucanase. Mannanase activity has a similar pattern of expression to the endoglucanase, while the xy lanase was not induced or repressed by the same sugars or combinations of sugars. The xylanase activity was greatest when xylan was the ener gy source for growth, but xylose was a very poor inducer of xylanase a ctivity.