Inorganic-carbon uptake by the marine diatom Phaeodactylum tricornutum.
Air-grown cells of the marine diatom Phaeodactylum tricornutum showed only 10% of the carbonic-anhydrase activity of air-grown Chlamydomonas reinhardtii. Measurement of carbonic-anhydrase activity using intact cells and cell extracts showed all activity was intracellular in Phaeodactylum. Photosynthetic oxygen evolution at constant inorganic-carbon concentration but varying pH showed that exogenous CO2 was poorly utilized by the cells. Sodium ions increased the affinity of Phaeodactylum for HCO 3 (-) and even at high HCO 3 (-) concentrations sodium ions enhanced HCO 3 (-) utilization. The internal inorganic-carbon pool (HCO 3 (-) +CO2] was measured using a silicone-oil-layer centrifugal filtering technique. The internal [HCO 3 (-) +CO2] concentration never exceeded 15% of the external [HCO 3 (-) +CO2] concentration even at the lowest external concentrations tested. It is concluded that an internal accumulation of inorganic carbon relative to the external medium does not occur in P. tricornutum.
Plant and Microbial Metabolism Research Group, School of Biological Sciences, University College of Swansea, Singleton Park, SA2 8PP, Swansea, UK.
B N
BN
Patel
M J
MJ
Merrett