Abstract
The intracellular pH and membrane potential were determined in the acidophilic algae Cyanidoschyzon merolae as a function of extracellular pH. The alga appear to be capable of maintaining the intracellular pH at the range of 6.35 to 7.1 over the extracellular pH range of 1.5 to 7.5. The membrane potential increase from −12 millivolts (negative inside) to −71 millivolts and thus Δμ̃H+ decreased from −300 to −47 millivolts over the same range of extracellular pH. It is suggested that the Δμ̃H+ may set the upper and lower limits of pH for growth. Photosynthetic performance was also determined as a function of pH. The cells appeared to utilize CO2 from the medium as the apparent Km(co2) was 2 to 3 micromolar CO2 over the pH range of 1.5 to 7.5 C. merolae appear to possess a `CO2 concentrating' mechanism.
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Selected References
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