Growth requirements of blue-green algae under blue light conditions

1. Growth requirements of blue-green algae containing only the c-phycocyanin + chlorophyll a pigment system have been studied under blue light (380–540 nm) which approximates light conditions existing in subsurface waters in nature.
2. While a few species were capable of very slow photosynthetic growth on minimal medium with NO₃ ^- as nitrogen source, most species were dependent on organic compounds for comparable growth under this condition. Some organisms did quite well with only Casamino Acids as a supplement, others did well with only glucose. One species, Agmenellum quadruplicatum strain PR-6, grew only when glucose and Casamino Acids were supplied simultaneously.
3. Inhibitory effects of blue light on CO₂ fixation and nitrogen metabolism are noted as possible explanations of these responses.