Variation in Photosynthetic Membrane and Pigment Content with Light Intensity for Anacystis nidulans Grown in Continuous Cultures

Photosynthetic membrane and chlorophyll content of the cyanobacterium Anacystis nidulans were determined after growth at different light intensities in Mg2+-limited and non-Mg2+-limited continuous cultures. Decreasing the light intensity from 445 to 31 μE m−2 s−1 resulted in a threefold increase of chlorophyll per unit cell volume. The photosynthetic lamellar structure, on the other hand, increased twofold under the same conditions. The specific chlorophyll content of the photosynthetic membrane increased when the light intensity was decreased from 445 to 282 μE m−2 s−1 and was constant at lower light intensities. The results indicate that the maximum chlorophyll content in the thylakoids of A. nidulans was about 1μ5 fg m−2, which means that the membrane contained 1 chlorophyll molecule per nm2 under these conditions.