green hydra symbiosis and ammonium. III. Characteristics of ammonium release by a high maltose-releasing symbiotic strain of Chlorella

Nitrogen-replete cultures of a high maltose-releasing strain of Chlorella (3N813A) released ammonium at pH 4; no ammonium was released by, a low maltose-releasing strain (NC64A). Ammonium release by 3N813A was markedly stimulated in darkness and was sustained over 48 h. Release in light was enhanced...

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Bibliographic Details
Published in:Proceedings of the Royal Society of London. Series B, Biological sciences Biological sciences, 1990, Vol.242 (1305), p.249-253
Main Author: Rees, T.A.V
Format: Article
Language:English
Subjects:
amino acids
ammonium compounds
Chlorella
dark
light
maltose
photorespiration
release
strains
symbiosis
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Summary:Nitrogen-replete cultures of a high maltose-releasing strain of Chlorella (3N813A) released ammonium at pH 4; no ammonium was released by, a low maltose-releasing strain (NC64A). Ammonium release by 3N813A was markedly stimulated in darkness and was sustained over 48 h. Release in light was enhanced in the presence of methionine sulphoximine, an inhibitor of glutamine synthetase, but there was only a minor increase in darkness. Amino acids, in particular alanine and glutamine, increased ammonium release in light. Ammonium release in darkness was markedly decreased in the presence of acetate and inhibitors of the Krebs cycle and gluconeogenesis. It is suggested that ammonium release by high maltose-releasing strains is due to deamination and an inability to reassimilate ammonium because of a limited supply of 2-oxoglutarate. It is further suggested that the carbon skeletons of the amino acids are utilized as gluconeogenic precursors for maltose biosynthesis.
ISSN:0080-4649
2053-9193