Isolation and characterisation of inducible Salmonella virulence genes.

Genes responsible for the pathogenicity of the facultative intracellular bacterium Salmonella will be isolated. Recent research demonstrated that several virulence genes of Salmonella are not constitutively expressed, but are induced upon contact with the host. We will make use of this observation for the isolation of new Salmonella virulence genes. RNA will be extracted from different organs of infected animals and the induced genes will be isolated by subtractive cloning. A second approach makes use of transposons that generate gene fusions upon insertion. For the isolation of specific virulence genes, only genes that are not expressed under standard growth conditions and are not present in the genome of the related bacterium Escherichia coli will be further investigated. These genes will be inactivated by directed in vitro mutagenesis or by insertion of a transposon and the interaction of the resulting mutants with their host will be studied in detail. Interesting new virulence genes will be sequenced and further characterised. This study can contribute to the development of new diagnostics and vaccines.