The DNA, RNA and protein composition of the cyanobacterium Anacystis nidulans grown in light- and carbon dioxide-limited chemostats.

The DNA, RNA and protein content of the cyanobacterium Anacystis nidudlans was determined in light-limited and carbon dioxide-limited chemostat cultures over the dilution rate range, D = 0.02 h-1 to 0.19 h-1. The macromolecular contents as a percentage of the dry weight and on a per cell basis varied significantly as a function of organism growth rate and the nature of the growth conditions. For both limitations the RNA content per cell increased [20-55 fg RNA (cell)-1] with increasing dilution rate and also showed an increase as a percentage of the dry weight. The DNA content as a percentage of the dry weight showed a 2-fold decrease with incresing dilution rate over the range examined. On a per cell basis DNA reached a peak at D = 0.1 h-1 [4.5 fg DNA (cell)-1] for light-limited organisms and at D = 0.08 h-1 [8.0 fg DNA (cell)-1] for carbon dioxide-limited organisms. The qRNA increased with increasing dilution rates over the complete growth rate examined whilst qDNA reached a maximum at D = 0.09 to 0.10 h-1. The protein content as a percentage of the dry weight was greater in CO2-limited organisms than light-limited organisms but in both cultures declined as the dilution rate was increased above D = 0.10 h-1.