OBSERVATIONS ON THE NITROGEN METABOLISM OF PROTOTHECA KRÜGER

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Abstract
Summary: Four strains of the putative apochlorotic algal genus Prototheca Krüger (P. chlorelloides, P. moriformis, P. portoricensis and P. zopfii), could utilize either ammonium sulphate or adenine as sole nitrogen source for growth but neither potassium nitrate nor sodium nitrite could be utilized. P. zopfii could also utilize the purines hypoxanthine and guanine, and both P. zopfii and P. chlorelloides could utilize a wide range of l‐ and d‐amino acids as sole nitrogen sources for growth in media containing glucose. P. zopfii and P. chlorelloides behave similarly to one another in the experiments and may, therefore, not be separate species, while P. moriformis and P. portoricensis behaved differently from them and from each other.Cell‐free extracts of P. zopfii had transaminase and nicotinamide adenine dinucleotide phosphate (NADP) dependent glutamate dehydrogenase activities. An attempt to show that ammonium assimilation involves a coupling between the NADP glutamate dehydrogenase and the oxidative pentose phosphate pathway was complicated by the fact that uptake of exogenously supplied glucose was inhibited during ammonium assimilation. The production of [14C] carbon dioxide from [1‐14C] glucose was inhibited less than both the uptake of glucose and the production of [14C] carbon dixoide from [6‐14C] glucose, suggesting that the oxidative pentose phosphate pathway provides the reduced coenzyme for ammonium assimilation.