Blocking virulence in enteroaggregative Escherichia coli

Enteroaggregative Escherichia coli (EAEC) is an important human pathogen, responsible for causing diarrhoea in both adults and children in industrialised and developing countries. EAEC biofilm formation, characterised as a 'stacked brick' structure, can disrupt the treatment of disease by antibiotics and allow evasion of the immune system response. Many of the virulence determinants are plasmid-encoded, and EAEC plasmids can be regarded as mobile vehicles of virulence. Previous studies have shown that the expression of plasmid-encoded virulence genes is tightly regulated at the level of transcript initiation, and the 'master' regulator, which is also plasmid-encoded, is AggR, a transcription activator that directly activates at least forty promoters controlling the expression of virulence determinants. AggR is thought to be a Class II activator and the structure of the protein is not known, its activity is inhibited by a small anti-activator protein, Aar (AggR-activated regulator).
The study will investigate the mechanisms by which AggR activates transcription, its regulation and the role of Aar. The genes aggR and aar will be subject to mutational analysis with a view of finding AggR and Aar mutants that can be used to interfere with the virulence pathway. These mutants will be exploited by cloning into vectors in order to counteract diarrhoeal disease. The aim of the project is to provide a therapeutic option not involving antibiotics.