Pattern of meso-dl-2,6-diaminopimelic acid incorporation during the division cycle of Escherichia coli.

The topography of meso-DL-2,6-diaminopimelic acid incorportion into the cell envelope of Escherichia coli W7 (doubling time, tau, = 70 min) has been studied by autoradiography. To follow the incorporation pattern during the division cycle, cells have been classified according to length and the silver grain distributions have been determined in the two cell halves. In particular, the question of equivalence (with respect to the grain distributions) of the two cell halves has been investigated statistically. The grain localizations have been determined separately for the left cell halves (highest number of grains) and right cell halves. The highest probability of finding grains was in the central area for cells of all length classes. In the longest cells (dividing or nondividing) incorporation occurred in the future septal regions of the prospective daughter cells. Autoradiography of tritiated thymidine-labeled cells indicated the presence of an atypical deoxyribonucleic acid replication cycle (at tau = 70 min). Initiation of deoxyribonucleic acid replication occurred during the latter part of the division cycle, and its termination occurred in the next cycle.