The role of sulfur in the cell division of chlorella

Abstract

1. The role of sulfur in the process of cell division of Chlorella was studied using the technique of synchronous culture. When the “dark cells” (smaller and strongly photosynthesizing cells), which had been grown in a normal nutrient medium, were further cultured in an S-deficient medium under photosynthesizing conditions, the cells grew up to some extent, showing about two-fold increase of DNA-content followed by the division of nucleus into two. At this stage, however, the cells fell into a stalemate, being unable to complete cellular division. 2. When such cells were transferred to a medium containing potassium sulfate only, some synthesis of DNA and further division of nuclei occurred. Under non-photosynthesizing conditions, the process of cellular division ensued, giving rise to a formation of small daughter cells. Under photosynthesizing conditions, on the other hand, the cells increased appreciably in size, without, however, being able to perform cellular division. The process of cellular division thus halted could be resumed when the cells were further supplied with nitrate and sulfate under photosynthesizing condition. 3. Based on these observations, it was concluded that sulfur plays, in cooperation with some nitrogenous substance(s), an essential role in the process of DNA-formation and nuclear division as well as in the process of cellular division.