| Abstract | The availability of whole genome sequences of bacteria has brought about fundamental changes in microbiology and is paving the way for novel applications of this information that will benefit epidemiology, pathobiology, diagnosis and prevention of infectious diseases. Hard on the heels of the completion of about a dozen whole genome sequences of bacteria are plans to sequence the chromosomes of parasites such as Plasmodium falciparum. Increasingly, investigators will have available a catalogue of gene sequences that include every virulence factor, every potential drug target and every vaccine candidate for a particular pathogenic microbe. In addition, the explosion of sequence data will have major implications for population biologists, ecologists and evolutionary biologists.
The availability of the whole genome sequence of Haemophilus influenzae strain Rd (1.83 megabase pairs) has facilitated significant progress in characterising the biosynthetic pathway of its lipopolysaccharide (LPS). LPS is a critical structural and functional component of the cell envelope, a major virulence factor that is involved in every stage of the pathogenesis of serious H. influenzae infections such as meningitis (inflammation of the linings of the brain). By searching the H. influenzae genomic data base with sequences of known LPS biosynthetic genes from other organisms, we identified and then cloned 25 candidate LPS genes. This has allowed the construction of mutant strains and analysis of the LPS by reactivity with monoclonal antibodies and PAGE fractionation patterns. Electrospray mass spectrometry comparative analysis has confirmed a potential role in the LPS biosynthesis for the majority of these candidate genes. Studies in the infant rat have allowed us to investigate the role of LPS in pathogenicity and to estimate the minimal structure required for intra vascular dissemination. This is one of the first studies to demonstrate the power of whole genome sequencing to extend biological knowledge of a pathogenic microbe (in silico to in vivo). The speed and ease of detection of genes is significantly greater than that by classical molecular genetic analysis and, in particular, allows the identification of genes found even under circumstances of weak amino acid homology. |
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