New Insights into the Final Stage of Bacterial Cell Division

Abstract

In Escherichia coli, cytokinesis is driven through the formation of the divisome, envelope invagination, peptidoglycan synthesis/degradation and daughter-cell separation. Although many proteins are implicated, the order and time needed for each involved protein's intervention remains ambiguous. One protein, Penicillin-Binding-Protein PBP3 (FtsI), seems particularly important for this process. In this paper, we describe a reproducible protocol to observe E. coli K-12 by Transmission Electron Cryo-Microscopy (cryo-TEM) on whole cells. We observed IM and OM invaginations during cell division and then analyzed the effects of PBP3 inhibitors on membrane-constrictive processes. Our results suggest that synthesis and invagination of the inner membrane can be completely dissociated from those of the outer membrane during a short time at a specific moment of the bacterial cell cycle, leading to the formation of two separate cytoplasms. These results help clarify the timing of PBP3 action during the bacterial cell cycle.

Riboregulation of the bacterial actin-homolog MreB by DsrA small noncoding RNA

“…Cells grown at 16 1C or 37 1C were prepared for cryo-transmission electron microscopy as described previously. 61 Z-loss images (25 eV slit) of each sample were recorded on a JEOL 2200FS cryo-transmission electron microscope operated at 200 kV by using a Gatan 2kx2k Ultascan ssCCD camera at average defocus and nominal magnification of À10 mm and 5000Â respectively. Length and width of bacteria were measured using ImageJ software (http://rsb.info.nih.gov/ij/) 62 to determine their roundness defined as the ratio between the minimal and the maximal axes of each cell.…”