Evidence for HCO3− Transport by the Blue-Green Alga (Cyanobacterium) Coccochloris peniocystis1

AUTOR(ES)

Miller, Anthony G.

RESUMO

The possibility of HCO3− transport in the blue-green alga (cyanobacterium) Coccochloris peniocystis has been investigated. Coccochloris photosynthesized most rapidly in the pH range 8 to 10, where most of the inorganic C exists as HCO3−. If photosynthesis used only CO2 from the external solution the rate of photosynthesis would be limited by the rate of HCO3− dehydration to CO2. Observed rates of photosynthesis at alkaline pH were as much as 48-fold higher than could be supported by spontaneous dehydration of HCO3− in the external solution. Assays for extracellular carbonic anhydrase were negative. The evidence strongly suggests that HCO3− was a direct C source for photosynthesis.

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