The Escherichia Coli is Capable of Large-Scale Translocation of its Chromosome

Abstract

Accurate placement of the cell division plane is essential for a bacterial cell to produce viable progeny. In the commonly accepted view, the Escherichia coli chromosome functions as a structural template that determines the placement of its cell division apparatus, the divisome [1]. This function is thought to be achieved by the nucleoid occlusion mechanism, which is mediated by SlmA proteins. In addition to nucleoid occlusion, a direct coordination between the nucleoid and the divisome is also provided the Ter region of the chromosome that promotes localization of Z-ring in its vicinity [2]. Here, we show that E. coli lacking these coordination mechanisms, and therefore failing to place their divisomes correctly relative to nucleoids, can still successfully propagate. We show that the propagation is possible because the nucleoid translocates across the closing division septum in late stages of cytokinesis. Using quantitative fluorescence imaging, we determine that more than half of chromosome can be translocated across the septum at peak rate of about 4000 bps/second. The last part of the translocation, which involves the replication terminus region, occurs approximately 5 minutes after early divisome proteins have dissociated from the cytokinetic ring. Our findings suggest that closing septum physically pushes chromosomes away from the division plane and this action prevents severing (guillotining) the chromosome even when the division plane is strongly misplaced.[1] Mannik J, Bailey MW (2015) Spatial coordination between chromosomes and cell division proteins in Escherichia coli. Front. Microbiol. 6 (2015) 306. http://dx.doi.org/10.3389/fmicb.2015.[2] Bailey MW, Bisicchia P, Warren BT, Sherratt DJ, Mannik J (2014) Evidence for divisome localization mechanisms independent of the Min system and SlmA in Escherichia coli. PLOS Genetics 10 (2014) e1004504. http://dx.doi.org/10.1371/journal.pgen.1004504.