Drifts in DNA level in the cyanobacterium Anacystis nidulans during synchrony induction and in synchronous culture

Cultures of the cyanobacterium Anacystis nidulans were synchronized by using alternating light-dark cycles. The DNA level in the cells was determined, at intervals, during pre-synchrony treatment and subsequent synchronous growth. The DNA content/cell gradually increased during synchrony induction and reached a maximum value after about 9–10 dark-light cycles, coinciding with the minimum length of pre-synchrony treatment necessary for obtaining good synchrony of cell division in our system. DNA synthesis was found to be discontinuous in the synchronous cultures. The results suggest two gaps in DNA synthesis, one occurring before and one after cell division. The results are compared with the relevant data published on the life cycle of other prokaryotic microorganisms.