A Bleached Variant of Euglena gracilis showing a Doubling of the Content of Deoxyribonucleic Acid

Abstract

WHEN certain strains of the green flagellate Euglena gracilis are grown at 34–35°, cultures devoid of chloroplasts are obtained¹. These cells, which we term bleached, resemble the normal organisms cultivated in the dark (designated colourless), but they have lost a hereditary character necessary for the formation of the plastids². In the course of a study of the chemical changes attending the loss of the photosynthetic apparatus in Euglena, a bleached culture (‘Bleached II’) derived from the normal strain z by thermal treatment, which had been carried through frequent liquid transfers for about three years, was found to contain twice the amount of deoxyribonucleic acid that is present in the original green or colourless cells. A comparison of the properties of this bleached variant with those of colourless cells showed the first to contain also more ribonucleic acid and protein and to have a slower rate of growth. Although the nuclei of these two cell types, when treated by the Feulgen method, appeared of equal size, those of the bleached organisms were coloured more intensely.