Plastids of the yellow y-1 strain ofEuglena gracilis

Summary A yellow strain, called y-1, was isolated during heat-induced bleaching ofEuglena gracilis strain Z.The ultrastructure, growth, and carotenoid content of this strain were studied and compared with those of the wild-typeEuglena and the heat-bleached colourless strain.The yellow, xanthophyll-containing strain y-1 resembles in many respects the etiolated wild-typeEuglena which has lost the ability to form chloroplasts in the light. It represents a transitional stage in the process of progressive degradation of plastids induced by bleaching treatments between the wild-typeEuglena and the colourless strain.Both bleached strains differ mainly in their carotenoid content formed in the light and especially in the dark, and the size and distribution of undeveloped plastids. In the yellow bodies of both strains PLB structure appears in accordance with their plastid nature.Thus, as shown in the present paper, the structural changes, appearing in the plastids of bleachedEuglena, seem to be at least morphologically very similar to the structural changes occuring in transforming plastids of higher plants.