β-Glucan biosynthesis in synchronous cells of Prototheca zopfii

Synchronous cultures of the colorless chlorophyte Prototheca zopfii Kruger were obtained by a shift-down of the basal medium plus addition of 1.5 mM ethylenediaminetetracetic acid for a 10-14-h period, followed by periodic dilutions with the basal medium. The cell cycle has a duration of 10-12 h at 25°C and an average of eight autospores are produced at the end of each cycle. The incorporation of [(14)C]glucose into β-glucans was determined in vivo. Very high incorporation occurs between hours 3 and 4 of culture, coincident with maximal cell expansion. The incorporation of glucose from uridine 5'diphospho-[(14)C]glucose into lipid-linked sugars and glycoproteins, as well as the activity of guanosine 5'-diphosphoglucose:β-glucan synthase found in cell-free preparations are in good agreement with the in-vivo incorporation of glucose into β-glucans.