Cellular and extracellular structures in Cryptococcus laurentii and Rhodotorula species

Abstract

A comparative study was made of yeast cells by microchemical reactions carried out under the light microscope and with the aid of electron microscopy.Two of the yeast species chosen (Cryptococcus laurentii and Rhodotorula glutinis) formed extracellular lipid and slime, whereas the third species (R. gracilis) was a non-lipid excreting strain of R. glutinis. A fourth yeast strain (R. graminis) lost the property of extracellular lipid formation during cultivation under laboratory conditions. The yeast cultures used were 1 and 2 days old.To preserve the original contact of the external products with the yeast cell proper, preparation techniques for electron microscopy without centrifugation were used. Special attention was paid to the formation of internal and external lipids, the age of the cells being taken into account. The differences in the fine structure of the cells, whether or not excreting lipid and slime, are described also. On the basis of these data and those from the literature, the process of the lipid production and the formation of the cell wall is discussed.