Determination of nucleosides and nucleotides in seawater by HPLC; application to phosphatase activity in cultures of the alga Phaeocystis pouchetii

Abstract

Nucleosides and nucleotides, dissolved in artificial and natural seawater, were separated by HPLC (High Pressure Liquid Chromatography) on a C- 18 reversed phase column. Test compounds in concentrations as low as 5 to 25 nM were directly detectable by UV-absorption. Determinations of nucleosides and nucleosidemonophosphates were used to analyse the alkaline phosphatase activity (APA) in cultures of Phaeocystis pouchetii. Phosphate-depleted cultures of this colonial phytoplankter hydrolysed uridine mono-phosphate at a rate 7 times higher than 3-0-methylfluorescein phosphate, a commonly used artificial test substance for APA. The uridine, cytidine and guanosine moieties of nucleoside monophosphates were partially assimilated by the cultures, probably in connection with enzymatic hydrolysis. The application of HPLC analysis of cellular and dissolved nucleotides in both cultures and natural communities of planktonie organisms is discussed.