Isolating two regulatory mutants involved in controlling the E. coli k5 capsule gene expression

ABSTRACT

Extra intestinal isolates of Escherichia coli associated with disease often express high molecular weight acidic polysaccharide capsules, or K antigens, on their cell surface. Over 80 such K antigens have been identified, and these have been divided into four principal groups based on serological, biochemical, and genetic data. The K5 polysaccharide is commonly associated with strains causing urinary tract infections and belongs to Group 2. These capsules resemble those possessed by Neisseria meningitides and hemophilic influenza. The K5 capsule gene cluster is composed of three principal regions, [1-3] and their transcription is driven by two convergent temperature-regulated promoters located upstream of regions 1 and 3. In this paper, working on the region 1 promoter evidence is presented of a role for two transcriptional regulators in the regulation of transcription of the Escherichia coli K5 capsule gene cluster and demonstrate, using a combination of reporter gene fusions, random transposon mutagenesis, P-Galactosidase assays, PCR and Southern blotting that mutations in any of these two genes markedly reduced transcription from region 1 promoter. Sequencing of these two mutated genes is required for full characterization