[Study of the cell walls of yeasts Rhodotorulamv'nfluence of the conditions of culture on the phosphatases of Rh; rubra (author's transl)].

1. Acid and alkaline phosphatase activities have been characterized on intact yeast cells and isolated cell walls Rh. rubra. These activities are sensitive to inhibition by orthophosphate. 2. The mechanical disruption does not increase the acid phosphatase activity and almost the entire activity is in the particular fraction. Its response to physicochemical factors is uniform, whatever the state of the preparation. It seemed to be entirely localized in the cell wall. The mechanical disruption of Rh. rubra yeast cells provokes only a small increase in alkaline phosphatase activity. Almost all the activity is in the particular fractions after centrifuging. The response to the physicochemical factors studied differs according to the state of the preparation. This alkaline phosphatase activity is for the most part cell wall localized, but seems also to be located in the periplasmic space or inside the plasmic membrane of Rh. rubra. 3. Trypsine or "beta-glucanase complex" treatments of the yeast cells eliminate much of peptidic and glucidic compounds and provoke a more important increase of the phosphatase activities of yeasts cultivated in rich phosphate media than that obtained after treatments of yeast cultivated in poor phosphate medium. These treatments which affect only the superficial structures of the cell envelope and do not touch the enzymic molecule (the phosphatase Km values are unchanged after treatments, and Ki values are the same before and after treatments) are favourable to a masking of the cell wall phosphatases by culture of Rh. rubra with high concentrations of phosphate. This phenomenon is corroborated by electron microscopy studies.