Fig 1.
Simplified schematic of the UPEC morphology cycle during UTIs.
(1) Rod-shaped bacteria adhere to BECs. (2) Invasion via endocytosis. (3) Rods undergo shape changes to a cocci-like form and densely cluster together in biofilm-like IBCs. In a second step, a subpopulation of the bacteria reinitiate growth, without dividing, to become filamentous. The exact molecular ques regulating this are unknown, but the cell division protein DamX is essential for filamentation [38]. (4) The growth of IBCs and filaments overwhelms the bladder cell, which ruptures whereby UPEC of various morphologies are expelled. (5) Exfoliated filaments (A) can continue to elongate to 100s of micrometers (B) before the cell division machinery is “switched on” and reversal is initiated (C). DamX also has a function during reversal (filament division); DamX tagged with a fluorescent protein forms stable rings at division sites along the filaments [31,38]. Daughter cells are pinched off from the mother filament at an increasing rate during the early stages of reversal, which would allow reinitiation of the infection cycle by invasion of noninfected bladder cells (1). BEC, bladder epithelial cell; IBC, intracellular bacterial community; UPEC, uropathogenic Escherichia coli; UTI, urinary tract infection.