Contributions of Respiratory and Photosynthetic Pathways during Growth of a Facultative Photoautotrophic Cyanobacterium, Aphanocapsa 6714

Comparison of the growth parameters and photosynthetic capacities of cells of Aphanocapsa 6714 under various growth conditions led to the following conclusions: (a), no enzymic regulation of CO₂/glucose assimilation takes place in this strain; (b), functioning of photodependent phosphorylating pathways turns off oxidative ATP synthesis; (c), no efficient regulation of pigment synthesis exists in these cells; (d), most modulations of photosynthetic activities probably occur through structural modifications of the photosynthetic membranes (a small proportion of the pigments might appear as a nonintegrated pool in the cell and be sensitive to synthesis regulation); and (e), photosystem II activity would be dependent on light intensity in a discontinuous way, the consequence of this property being the appearance of two successive exponential phases during phototrophic growth in adequate light conditions.