RESUMO
Genome maps have been constructed for the mycobacterial pathogens Mycobacterium leprae and Mycobacterium tuberculosis, as well as for the attenuated vaccine strain Mycobacterium bovis BCG Pasteur. While the chromosomes of M. tuberculosis and M. bovis BCG Pasteur show extensive conservation at the gross level, comparison with M. leprae revealed a high degree of diversification, with a mosaic-like pattern apparent. The ordered libraries of M. tuberculosis and M. leprae produced during the course of these studies played a central role in the genome sequencing projects of these two bacilli, showing the utility of this approach for systematic sequencing of bacterial genomes.
Assuntos
Genoma Bacteriano , Mycobacterium/genética , Mapeamento Cromossômico , Cromossomos BacterianosRESUMO
An integrated map of the genome of the tubercle bacillus, Mycobacterium tuberculosis, was constructed by using a twin-pronged approach. Pulsed-field gel electrophoretic analysis enabled cleavage sites for Asn I and Dra I to be positioned on the 4.4-Mb circular chromosome, while, in parallel, clones from two cosmid libraries were ordered into contigs by means of fingerprinting and hybridization mapping. The resultant contig map was readily correlated with the physical map of the genome via the landmarked restriction sites. Over 165 genes and markers were localized on the integrated map, thus enabling comparisons with the leprosy bacillus, Mycobacterium leprae, to be undertaken. Mycobacterial genomes appear to have evolved as mosaic structures since extended segments with conserved gene order and organization are interspersed with different flanking regions. Repetitive sequences and insertion elements are highly abundant in M. tuberculosis, but the distribution of IS6110 is apparently nonrandom.
Assuntos
Cromossomos Bacterianos , Genoma Bacteriano , Mycobacterium leprae/genética , Mycobacterium tuberculosis/genética , Mapeamento Cromossômico , Cosmídeos , Elementos de DNA Transponíveis , Desoxirribonucleases de Sítio Específico do Tipo II , Biblioteca Gênica , Marcadores Genéticos , Mapeamento por Restrição , Especificidade da EspécieRESUMO
To facilitate comparison of the genome maps of Mycobacterium tuberculosis and M. leprae, sequence data from the M. leprae sequencing project were used to design primers suitable for the amplification of short segments from conserved genes by the polymerase chain reaction. In most cases, both organisms yielded products of identical size that were then used as probes for a comparative genomic walk. The hybridization data often, but not always, revealed a similar organization of various regions of both genomes. This approach should be useful for systematic comparisons of (myco)bacterial genomes.