Growth and macromolecular composition of Anacystis nidulans at different temperatures in Mg2+- and K+-limited chemostats

Abstract

Alterations in dry weight, macromolecular composition and cell volume with temperature, were examined for Mg2+- and K+-limited Anacystis nidulans. The experiments were performed in chemostats with constant dilution rate. Increasing the temperature from 30–40°C resulted in a 2.1 times increase in yield (g dry weight/g ion) for the Mg2+-limited culture, while it increased 1.3 times in the K+-limited culture. This difference in yield increase with temperature was caused by a large accumulation of carbohydrate in the Mg2+-limited cells. The relation between RNA and protein was found to be independent of temperature in both cultures. This indicated that A. nidulans contained “extra” inactive RNA under the growth conditions used. These results are discussed to indicate that A. nidulans regulates the rate of protein synthesis by activating/inactivating RNA in protein synthesis. The filament size and cellular DNA content both increased 1.6 times in the Mg2+-limited cells when decreasing the temperature from 40 to 30°C. The chlorophyll content of A. nidulans was found to be independent of temperature in both cultures.