As. Pac. J. Mol. Biol. & Biotech., Dec 1999 Vol. 7(1) : 1-12

Integration of virulence genes into bacterial chromosomes

V. Krishnapillai

>Department of Biological Sciences,
Monash University, Clayton, Victoria 3168, Australia

(Received 28 May 1999 / Accepted I June 1999)

Abstract.

This review focuses on bacterial virulence genes, both of plants and animals, in relation to their location and organization in bacterial chromosomes, These genes commonly occur in contiguous gene clusters that are referred to as "pathogenicity islands". Their DNA sequences are often different to that of the surrounding chromosomal DNA sequences. This G + C content difference has been interpreted as being due to their mobility between genomes by horizontal gene transfer perhaps mediated by temperate bacteriophages, plasmids, or transposable elements. A,striking aspect of the sites of integration of these gene clusters is their site specific recombination into transfer RNA genes. The fact that bacterial chromosomes have many such genes implies that there must be genetic advantage for these virulence genes to be integrated into transfer RNA genes as it ensures co expression of virulence genes with a fundamental function of the cell, namely translation/protein synthesis.

Key Words: Bacterial chromosomes, virulence genes