On the “Activation” of the Lactase of Escherichia coli-mutabile

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Abstract
Lactase activity of dried and non-dried cells-was compared by measuring the amt. of O2 consumed ("oxidase system") in the oxidation of the monose split products. Vacuum-dried cell suspensions of the white strain consumed 3-6 times as much O2 in lactose as did the non-dried suspensions. By drying suspensions of the red strain, the amount of O2 consumed in lactose was doubled. Injury to the cells by drying releases the lactase. With both the red and white strains, preliminary cultivation on agar containing fermentable carbohydrates (glucose or lactose) brought about an inhibition of the oxidase system. Failure of the white strain to ferment lactose is held to be due. not to the absence of lactase in the cells, but rather to the impermeability of the cells to lactose.