SUMMARY: () (ncib 418, no. 240) was grown at dilution rates between 0.1 and 1.0 hr in a variety of nutrient-limited chemostats and the activities of dehydrogenases, particularly glucose (R), fructose (R), sucrose (R), maltose (R) and gluconate (R) dehydrogenases, were determined in intact organisms. Their activities varied from system to system, but, with a few exceptions, were largely independent of the dilution rate. R was generally high when sugars provided the carbon for growth but when intermediates of the tricarboxylic acid cycle were used it was often low. R behaved like R but R, R, and R were more variable. In general the activities were higher in C-limitation than in other nutrient-limited conditions.

Specific activities of α- and β-glucosidase were also determined in some of the systems. Organisms grown in a maltose-limited system had the highest α-glucosidase activity but 40% of this level was observed in those from a cellobiose-limited system although cellobiose is a β-glucoside. Glucose, fructose, sucrose, lactose or disaccharides containing an α 1 → 6 linkage as carbon sources induced little activity. As expected, growth in cellobiose-limited conditions led to high β-glucosidase activity but melibiose-grown cells were about 50% as active. Replacing NH+, the usual N source in the medium, by NO- in a glucose-limited system increased the β-glucosidase activity five- to sixfold, while NO- led to a tenfold decrease. α-Glucosi-dase was less affected.


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