Phosphate deprivation of Saccharomyces cerevisiae

Ramsay, Andrew Melvin (1977) Phosphate deprivation of Saccharomyces cerevisiae. PhD thesis, University of Glasgow.

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Substantial changes have been reported in both the cell-wall and lipid composition of a variety of bacteria when these organisms were grown under conditions of phosphate limitation. Similar detailed studies with yeasts have not yet been described, however. The major objective of the present work was therefore an analysis of changes in the content and composition of these components resulting from growth of Saccharomyces cerevisiae NCYC 366 under phosphate-limiting conditions. Phosphate-limited cells obtained by either batch or continuous culture of the yeast contained less total phosphorus than did cells grown in medium with an optimum concentration of phosphate. Detailed analysis of these cells revealed complex changes in both cell-wall and lipid composition although the changes observed were less dramatic than those described for bacteria. Walls prepared from phosphate-limited cells had a lower phosphate content than did those from control cells. No evidence was obtained for the presence in these walls of uronic acid or succinyl residues although they did appear to contain an increased proportion of one or more unidentified anionic components. Walls prepared from chemostat-grown, phosphate-limited cells contained less carbohydrate than did those from control cells and this was reflected in a considerably decreased glucan content. The glucosamine content of the walls was only slightly affected however, while that of protein increased. The most striking change observed in the lipid composition of phosphate-limited cells was a decrease of both sterol esters and triacylglycerols. Phospholipid synthesis, overall, appeared to be stimulated, leading to an increased proportion of phosphatidylethanolamine and phosphatidylcholine. The phosphatidylserine content on the other hand was decreased. These changes in both cell-wall and composition were interpreted in terms of a diminished population of small or large vesicles in the phosphate-limited yeast. A secondary objective of this study was to investigate the reported occurrence of teichoic acid in Candida intermedia and then to extend the survey for these polymers to other yeast species. Trichloroacetic acid extracts of C. intermedia, C. utilis and Sacch. cerevisiae were subjected to acid hydrolysis and the hydrolysates examined for products characteristic of a glycerol teichoic acid. Traces of glycerol v/ere found in almost all of the hydrolysates, but glycerol phosphate was only identified in the hydrolysate of one extract from C. intermedia. Glycerol diphosphate was not detected. Some evidence was obtained for the synthesis of a polymeric product from CDP-glycerol by subcellular fractions of C. intermedia. These results were considered too equivocal to support a claim for the presence of teichoic acids in yeasts.

Item Type: Thesis (PhD)
Qualification Level: Doctoral
Additional Information: Adviser: Julia Douglas
Keywords: Microbiology
Date of Award: 1977
Depositing User: Enlighten Team
Unique ID: glathesis:1977-72282
Copyright: Copyright of this thesis is held by the author.
Date Deposited: 24 May 2019 15:12
Last Modified: 24 May 2019 15:12

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