E. coli division machinery drives cocci development inside host cells

Abstract

Escherichia coli is arguably one of the most studied bacterial model systems in modern biology. Under normal laboratory conditions E. coli adopts its characteristic rod-shape. However, during stress conditions E. coli has been shown to undergo conditional morphology changes to inhibit division and grow into highly elongated forms. Here, on the other end of the morphology spectra, using an in-vitro infection model system combined with advanced imaging we show uropathogenic E. coli rods dividing to form and proliferate as cocci inside human bladder epithelial cells. In these intracellular bacterial communities, the frequency of cell division outpaced the rate of cell growth, resulting in smaller cocci cells. This mechanism was guided by an active FtsZ-governed division machinery, directed to midcell by division-site placement systems. These results show how a previously uncharacterised level of morphological plasticity occurs in bacteria with traditionally well-defined rod shape.