TY - JOUR

T1 - Inorganic carbon acquisition in potentially toxic and non-toxic diatoms: the effect of pH-induced changes in the seawater carbonate chemistry.

AU - Trimborn, S

AU - Lundholm, Nina

AU - Thoms, S

AU - Richter, K-U

AU - Hansen, Per Juel

AU - Krock, B

AU - Rost, B

PY - 2008

Y1 - 2008

N2 - The effects of pH-induced changes in seawater carbonate chemistry on inorganic carbon (C-i) acquisition and domoic acid (DA) production were studied in two potentially toxic diatom species, Pseudo-nitzschia multiseries and Nitzschia navis-varingica, and the non-toxic Stellarima stellaris. In vivo activities of carbonic anhydrase (CA), photosynthetic O-2 evolution and CO2 and HCO3- uptake rates were measured by membrane inlet MS in cells acclimated to low (7.9) and high pH (8.4 or 8.9). Species-specific differences in the mode of carbon acquisition were found. While extracellular carbonic anhydrase (eCA) activities increased with pH in P. multiseries and S. stellaris, N. navis-varingica exhibited low eCA activities independent of pH. Half-saturation concentrations (K-1/2) for photosynthetic O-2 evolution, which were highest in S. stellaris and lowest in P. multiseries, generally decreased with increasing pH. In terms of carbon source, all species took up both CO2 and HCO3-. K-1/2 values for inorganic carbon uptake decreased with increasing pH in two species, while in N. navis-varingica apparent affinities did not change. While the contribution of HCO3- to net fixation was more than 85% in S. stellaris, it was about 55% in P. multiseries and only approximately 30% in N. navis-varingica. The intracellular content of DA increased in P. multiseries and N. navis-varingica with increasing pH. Based on our data, we propose a novel role for eCA acting as C-i-recycling mechanism. With regard to pH-dependence of growth, the 'HCO3- user' S. stellaris was as sensitive as the 'CO2 user' N. navis-varingica. The suggested relationship between DA and carbon acquisition/C-i limitation could not be confirmed.

AB - The effects of pH-induced changes in seawater carbonate chemistry on inorganic carbon (C-i) acquisition and domoic acid (DA) production were studied in two potentially toxic diatom species, Pseudo-nitzschia multiseries and Nitzschia navis-varingica, and the non-toxic Stellarima stellaris. In vivo activities of carbonic anhydrase (CA), photosynthetic O-2 evolution and CO2 and HCO3- uptake rates were measured by membrane inlet MS in cells acclimated to low (7.9) and high pH (8.4 or 8.9). Species-specific differences in the mode of carbon acquisition were found. While extracellular carbonic anhydrase (eCA) activities increased with pH in P. multiseries and S. stellaris, N. navis-varingica exhibited low eCA activities independent of pH. Half-saturation concentrations (K-1/2) for photosynthetic O-2 evolution, which were highest in S. stellaris and lowest in P. multiseries, generally decreased with increasing pH. In terms of carbon source, all species took up both CO2 and HCO3-. K-1/2 values for inorganic carbon uptake decreased with increasing pH in two species, while in N. navis-varingica apparent affinities did not change. While the contribution of HCO3- to net fixation was more than 85% in S. stellaris, it was about 55% in P. multiseries and only approximately 30% in N. navis-varingica. The intracellular content of DA increased in P. multiseries and N. navis-varingica with increasing pH. Based on our data, we propose a novel role for eCA acting as C-i-recycling mechanism. With regard to pH-dependence of growth, the 'HCO3- user' S. stellaris was as sensitive as the 'CO2 user' N. navis-varingica. The suggested relationship between DA and carbon acquisition/C-i limitation could not be confirmed.

U2 - 10.1111/j.1399-3054.2007.01038.x

DO - 10.1111/j.1399-3054.2007.01038.x

M3 - Journal article

C2 - 18405335

VL - 133

SP - 92

EP - 105

JO - Physiologia Plantarum

JF - Physiologia Plantarum

SN - 0031-9317

IS - 1

ER -