Characterization of Cell Cycle Events in Synchronized Cultures of Anacystis nidulans

Synchronized cultures of Anacystis nidulans (Synechococcus PCC 6301) were induced by a light-dark incubation scheme under moderate light intensity (3·2 J m −2s−1). At incubation temperatures of 32 °C. 35 °C and 38 °C, typical step-wise growth cycles were observed at growth rates of 8, 6 and 4 h doubling times, respectively. Using the same method of inducing cell synchrony but under increased light intensity (4·8 J m −2s−1), cell number increased exponentially and growth rates were twice as high as those at the lower light intensity, at incubation temperatures of 32 °C, 35 °C and 38 °C. At 32 °C under high light intensity, the synthesis of protein, RNA, DNA and cell wall material occurred periodically in a temporal order, although cell number increased exponentially. The data suggested that the growth of Anacystis under these conditions could essentially be characterized as synchronized. The macromolecular synthesis periods (cell cycle events) are apparently controlled by complex sets of genetic and metabolic controls that allow Anacystis to take advantage of changing environmental conditions.