Aquatic Sciences Meeting, Albuquerque 2001

SS16 Iron Bioavailability and Limitation to Primary Production (Disciplinary Connections)

Date: Monday, February 12, 2001, Time: 4:00:00 PM

Location: Mesilla

Milligan, A, J, Princeton University, Princeton, USA, allenm@princeton.edu

Mioni, C, E, Princeton University, Princeton, USA, cecile.mioni@voila.fr

Morel, F, M, Princeton Univeristy, Princeton, USA, morel@princeton.edu

THE RESPONSE OF CARBON METABOLISM TO IRON DEFICIENCY IN THE MARINE DIATOM THALASSIOSIRA WEISSFLOGII

Strategy I vascular plants respond to iron deficiency by inducing ferric chelate reductase activity, effluxing protons and increasing organic acid synthesis, primarily citrate and malate. Proton extrusion and organic acid synthesis are linked through the regulation of cytoplasmic pH. According to the pH-stat theory the increase in cytoplasmic alkalinization during proton efflux causes an increase in the activity of PEPcarboxylase which synthesizes an organic acid (malate) and maintains optimal pH. Because low CO2 also elicits an increase in PEPcase activity, we grew cultures under low (100 ppm) and high (750 ppm) CO2 with low (pFe 20.75) and high (pFe 19) iron availability. We found that the activity of PEPcase is greatest relative to carbon demand under either low CO2 (C4 response) or low Fe (pH response) and greatest when both are low. Low iron grown cultures also exhibit ferric chelate reductase activity. This suggests that diatoms may use a method of Fe acquisition similar to strategy I vascular plants.

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Aquatic Sciences Meeting, Albuquerque 2001

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