CHANGES IN CONTENTS OF CARBOHYDRATE AND FATTY ACID IN THE CELLS OF CHLORELLA PROTOTHECOIDES DURING THE PROCESSES OF DE- AND RE-GENERATION OF CHLOROPLASTS

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Abstract
Previous work has demonstrated that when cells of Chlorella protothecoides are grown mixotrophically under illumination in a medium rich in nitrogen source (urea) and poor in glucose, normal green cells are obtained, while in a medium rich in glucose and poor in the nitrogen source, strongly bleached cells containing apparently no discernible chloroplast structures — called “glucose-bleached” cells — are produced either in the light or in darkness. When the green cells are incubated in a glucose-enriched mineral medium without added nitrogen source, they are fairly rapidly bleached with concomitant degeneration of chloroplast structures (“ bleaching ”). When, on the other hand, the “glucose-bleached” cells are transferred in a nitrogen-enriched medium without added glucose under illumination, they turn green with regeneration of chloroplasts (“ greening ”). In the present study changes in contents of carbohydrate and fatty acid in algal cells were followed during these processes of “bleaching” and “greening.”. During the process of “bleaching”, the quantity of glucose existing in the insoluble carbohydrate fraction of algal cells increased rapidly and markedly. A considerable increase was also observed in the contents of cells in oleic, linoleic and palmitic acids. It was noted, however, that linolenic acid decreased in quantity during the most active phase of cell bleaching. During the process of “greening”, the glucose in the insoluble carbohydrate fraction rapidly decreased, suggesting that it is utilized, as carbon and energy sources, for the chloroplast regeneration. Linolenic acid was found to be synthesized in parallel with formation of chlorophyll. A peculiar pattern of change in contents was observed with oleic and palmitic acids, which was interpreted as being related with the process of cellular division occurring incidentally during the process of greening.