title: Bioavailability of organic phosphorus to Pseudokirchneriella subcapitata as affected by phosphorus starvation: an isotope dilution study.
abstract: Phosphorus (P) starved algae have a capacity to rapidly take up P when resupplied to P. This study was set-up to measure to what extent P starvation enhances the potential of algae to utilize organic P forms. The initial (<0.5 h) PO4 uptake rates of cells of Pseudokirchneriella subcapitata increased up to 18-fold with increasing starvation. Algae from different levels of P starvation were subsequently exposed to different model organic P forms and carrier-free (33)PO4. Uptake (1h) of P from organic P-increased up to 5-fold with increasing P starvation. The bioavailability of organic P, relative to PO4, was calculated from uptake of (31)P and (33)P isotopes assuming no isotopic exchange with organic P-forms. This relative bioavailability ranged from 0 to 57% and remained generally unaffected by the extent of P-starvation. This result was found for cells that were either or not treated by a wash method to remove extracellular phosphatases. Short-term P uptake rate sharply increases with decreasing internal P content of the algal cells but the bioavailability of organic P, relative to PO4, is not enhanced. Such finding suggests that P-starvation enhances PO4 uptake capacity and organic P hydrolysis capacity to about the same extent.
authors.affiliation: Division of Soil and Water Management, Department of Earth and Environmental Sciences, KU Leuven, Kasteelpark Arenberg 20, 3001 Heverlee, Belgium. Christoff.VanMoorleghem@ees.kuleuven.be
authors.forename: Christoff
authors.initials: C
authors.lastname: Van Moorleghem
authors.forename: Nynke
authors.initials: N
authors.lastname: De Schutter
authors.forename: Erik
authors.initials: E
authors.lastname: Smolders
authors.forename: Roel
authors.initials: R
authors.lastname: Merckx
mesh_terms: D001682:Biological Availability; D019149:Bioreactors; D000460:Chlorophyta / Q000166:cytology / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism*; D008954:Models, Biological; D009930:Organic Chemicals / Q000493:pharmacokinetics*; D010758:Phosphorus / Q000172:deficiency* / Q000493:pharmacokinetics* / Q000494:pharmacology; D010761:Phosphorus Radioisotopes; D011865:Radioisotope Dilution Technique; D013997:Time Factors
chemical_list: D009930:Organic Chemicals; D010761:Phosphorus Radioisotopes; D010758:Phosphorus