Cell division is an essential cellular process that requires an assortment of known and unknown proteins for its spatial and temporal regulation. However, in response to environmental and immune factors, many species of bacteria continue to grow in the absence of cell division, resulting in filamentous cells. This cellular morphology has been shown to provide a selective advantage for a number of bacterial species in a wide range of environmental niches and is important for uropathogneic Escherichia coli during its infective cycle.
In this study we have developed a novel, high-throughput screening method for the identification of bacterial cell division genes and regulators. The method combines the over-expression of an E.coli shotgun genomic expression library to perturb the cell division process with high-throughput flow cytometry sorting to screen many thousands of clones. Genetic analysis of filamentous clones revealed that our screen identified both known cell division genes, and genes that have not previously been identified to be involved in cell division. Further investigation of one clone confirmed that expression of ytfB, a gene of unknown function with homology to the colonisation factor opacitiy-associated protein A of Haemophilus, resulted in filamentous cells. Since this cellular morphology is associated with the UPEC infective cycle, the role of ytfB during urinary tract infections was further investigated. The effect of deletion of ytfB on growth, motility, lysozyme sensitivity and adherence to immortalised human bladder and kidney epithelial cells was examined and revealed that loss of YtfB resulted in hypermotility and a 10-fold reduction in adherence to human embryonic kidney cells. Further studies will aim to characterise the link between filamentation and UPEC infections. Thus, this novel screening study has allowed the identification of cell division genes and regulators that effect cellular morphology and may contribute to pathogenesis during urinary tract infections.