ISSN:
1432-2048
Keywords:
Carbon, inorganic (transport)
;
Carbonic anhydrase
;
Marine microalgae
;
Monallantus
;
Nannochloropsis
;
Stichococcus
Source:
Springer Online Journal Archives 1860-2000
Topics:
Biology
Notes:
Abstract Inorganic-carbon transport was investigated in the eukaryotic marine microalgaeStichococcus minor, Nannochloropsis oculata and aMonallantus sp. Photosynthetic O2 evolution at constant inorganic-carbon concentration but varying pH showed thatS. minor had a greater capacity for CO2 rather than HCO 3 − utilization but forN. oculata andMonallantus HCO 3 − was the preferred source of inorganic carbon. All three microalgae had a low affinity for CO2 as shown by the measurement of inorganic-carbon-dependent photosynthetic O2 evolution at pH 5.0. At pH 8.3, where HCO 3 − is the predominant form of inorganic carbon, the concentration of inorganic carbon required for half-maximal rate of photosynthetic O2 evolution [K 0.5 (CO2)] was 53 μM forMonallantus sp. and 125 μM forN. oculata, values compatible with HCO 3 − transport. Neither extra- nor intracellular carbonic anhydrase was detected in these three microalgal species. It is concluded that these microalgae lack a specific transport system for CO2 but that HCO 3 − transport occurs inN. oculata andMonallantus, and in the absence of intracellular carbonic anhydrase the conversion of HCO 3 − to CO2 may be facilitated by the internal pH of the cell.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00963814
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