Overview of Bacterial Genome Analysis, and Genomic Diversity and Virulence of Staphylococcus aureus

Abstract

A bacterial genome is characteristic to its circular chromosomal DNA most of which consist of coding sequences, showing clear contrast to eukaryotic cells carrying multiple numbers of linear chromosomes with lower ratio of the coding sequences than bacteria. The genes involved in a common biochemical pathway often form a polycistronic unit called operon, which is not seen in the eukaryotic cells. By knowing such unique characters of a bacterial genome, we can infer physiological features of a bacterium from its genome sequence, and the work is probably much simpler than that for eukaryotic cells.
The department of Bacteriology of the Juntendo Univ. determined the whole genome sequence of Staphylococcal aureus, a causative microorganism of nosocomial infections, for the first time in the world in collaboration with other domestic groups. By employing the obtained genome information, we performed comparative analyses with genomes of other S. aureus strains as well as those of related species of staphylococci. We thereby found that (i) a S. aureus genome carries its unique domains designated genomic islands that has been presumably acquired horizontally and are often accompanied with virulence or drug-resistant genes, in addition, (ii) the genomic islands show polymorphism among S. aureus strains, leading to carriage of different sets of the virulence determinants, indicating the toxicity of a S. aureus strain upon infection differs form the others.