Study of pole assembly in Bacillus subtilis by computer reconstruction of septal growth zones seen in central, longitudinal thin sections of cells.

摘要: The septal growth of Bacillus subtilis 168/s has been studied by making a number observations from thin sections cells exponentially growing cultures. process was initiated the formation new cross wall under preexisting layer cylindrical wall. An annular notch appeared to cut through overlying and presumably allowed split into two layers peripheral During this initial notching process, raised bands material were produced which resembled those previously observed in morphological studies Streptococcus faecalis. Through an improved fixation technique, it possible preserve seen B. extent that they used as markers study subsequent stages growth. These included (i) continued displacement (as nascent polar surfaces enlarged diameter decreased), (ii) closure wall, (iii) final severance common connection between completed poles. To more quantitative manner, three-dimensional reconstructions envelope pairs made axial cells. reconstruction based on technique x, y coordinates taken rotated around cell's central axis. estimate surface area or volume reconstructed zones their parts. A round then simulated arranging 118 order increasing volume. topology noting how various measurements thickness, length, area, varied function zone size. This analysis several assumptions, three most important are: are separate growth; is up poles single wall; develop terms relative age increase size (volume area) amount data suggested S. faecalis model (in occurs regulated constrictive separation expansion wall) also seems applicable pattern here for subtilis. indicated showed increases correlated with decreases diameter. explanation these may be due progressive splitting removed outer circumference converted surface. Calculations further if sizeable variable would required convert separating curved structures. Measurements thickness locations within while constant over its surface, width considerably during synthesis. Again, one simplest explanations compatible brought (possibly remodeling precursor addition) before separation. Although fit growth, differences when organisms compared. have discussed regulation respective sites basic mechanisms assembly modification.