Fig. 6.
Induction of high levels of active Spo0A blocks growth. A Pspac-kinA fusion construct was used to induce a high level of Spo0A activity during exponential growth; strains contained a PspoIIG-gfp fusion construct for the visualization of Spo0A-directed transcription. Bacteria of the parental and spoIIR backgrounds in early-exponential growth were placed on agarose pads containing the inducer IPTG (1 mM). After 2 h, their behavior was monitored by time lapse microscopy. (a) Images of the parental strain (SL15373). GFP levels increased gradually, and monosporic organisms were observed at high frequencies. In all the monosporic organisms tested, there was no growth of the mother cell. (b) Images of a spoIIR-null strain (SL15376). After induction, GFP levels increased gradually, and asymmetric septation was observed; this was followed by the formation of a second polar septation. In all these biseptate organisms tested, there was no growth of the mother cell. (c) Images of the spoIIR-null strain (SL15376), which continues to grow vegetatively in the absence of the inducer. Membranes were visualized by staining with FM4-64. Images were taken every 30 min. Bar, 3 μm.