Reversion sporulierender Bacillus megaterium ‐Zellen zum Wachstum

In carbohydrate‐limited, sporulating B. megaterium cultures reversion to growth was initiated by transfer into medium containing glucose and yeast‐extract. From cultures grown with different doubling times the iknetics of commitment to sporulation and loss of reversibility were studied both by phase‐contrast and electron microscopy. Commitment to refractility occurred about 20 min after formation of the spore septum and 140 min before spores became refractil. Not all of the cells which did not reach this stage of commitment until the time of transfer were able to revert. Reversibility was already lost during formation of the spore septum. Stage II‐cells which had formed the spore septum before transfer were committed to stage III despite the presence of nutrients, but their further development was blocked. Thus, like in other spore‐formers the condition for undisturbed spore development was the formation of the forespore under starvation. As only stage I‐cells were able to undergo reversion to growth, commitment to refractility did not correspond to loss of reversibility, as could be shown with other spore‐formers. Before in reverting cells the first division septum appeared (about one hr after transfer) the cells doubled in length. During that time in about 50% of the cells additional wall material was laid down at the younger poles. The first division septum was not formed in the middle of the cell, but the part with the older pole which would have built the spore was larger. In the presence of penicillin G the parts of the reverting cells were influenced differently. The part containing the younger pole got thicker, while the other showed the normal diameter.