%0 Journal Article %A Utkilen, Hans Christian %A Briseid, Tormod %T The Response of Mg2+-limited Anacystis nidulans to Alterations in Photon Fluence Rate When Grown in Chemostats: a Suitable System for Studies of Mg2+-controlled Cell Division %D 1984 %J Microbiology, %V 130 %N 12 %P 3079-3083 %@ 1465-2080 %R https://doi.org/10.1099/00221287-130-12-3079 %I Microbiology Society, %X The effect of photon fluence rate on Anacystis nidulans grown in Mg2+- and non-Mg2+-limited continuous cultures was studied. A decline in photon fluence rate from 445 to 30 μE m−2 s−1 resulted in a decrease of the mean cell volume from 2 to 0·8 μm3 in the Mg2+-limited culture. Compared with non-Mg2+-limited cultures, this was the only obvious difference found when decreasing the photon fluence rate. Altering the photon fluence rate for a Mg2+-limited chemostat therefore seems to be a suitable system for studies of the Mg2+-controlled events in cell division of A. nidulans. At constant dilution rate, the DNA content per unit cell volume was independent of photon fluence rate, while the RNA content decreased with this factor. The RNA/protein ratio decreased by a factor of 3 in both Mg2+- and non-Mg2+-limited cultures, when decreasing the photon fluence rate from 445 to 100 μE m−2 s−1. The RNA efficiency therefore varied with photon fluence rate and the organism seemed to have surplus RNA at high light intensities. %U https://www.microbiologyresearch.org/content/journal/micro/10.1099/00221287-130-12-3079