Mycobacterial genome structure

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.

Comparative analysis of B- and T-cell epitopes of Mycobacterium leprae and Mycobacterium tuberculosis culture filtrate protein 10

Stewart Cole

Culture filtrate protein 10 (CFP-10) from Mycobacterium tuberculosis is a well-characterized immunodominant 10-kDa protein antigen known to elicit a very potent early gamma interferon response in T cells from M. tuberculosis-infected mice and humans. The sequence of the Mycobacterium leprae homologue of CFP-10 shows only 40% identity (60% homology) at the protein level with M. tuberculosis CFP-10 and thus has the potential for development as a T- or B-cell reactive antigen for specific diagnosis of leprosy. Antisera raised in mice or rabbits against recombinant M. leprae and M. tuberculosis CFP-10 proteins reacted only with homologous peptides from arrays of overlapping synthetic peptides, indicating that there was no detectable cross-reactivity at the antibody level. Sera from leprosy and tuberculosis patients were also specific for the homologous protein or peptides and showed distinct patterns of recognition for either M. leprae or M. tuberculosis CFP-10 peptides. At the cellular level, only 2 of 45 mouse T-cell hybridomas raised against either M. leprae or M. tuberculosis CFP-10 displayed a cross-reactive response against the N-terminal heterologous CFP-10 peptide, the region that exhibits the highest level of identity in the two proteins; however, the majority of peptide epitopes recognized by mouse T-cell hybridomas specific for each protein did not cross-react with heterologous peptides. Coupled with the human serology data, these results raise the possibility that peptides that could be used to differentiate infections caused by these two related microorganisms could be developed. Immunohistochemical staining of sections of M. leprae-infected nude mouse footpads resulted in strongly positive staining in macrophages and dendritic cells, as well as weaker staining in extracellular areas, suggesting that M. leprae CFP-10, like its homologue in M. tuberculosis, is a secreted protein.

2004

Macro-array and bioinformatic analyses reveal mycobacterial 'core' genes, variation in the ESAT-6 gene family and new phylogenetic markers for the Mycobacterium tuberculosis complex

Stewart Cole

To better understand the biology and the virulence determinants of the two major mycobacterial human pathogens Mycobacterium tuberculosis and Mycobacterium leprae, their genome sequences have been determined recently. In silico comparisons revealed that among the 1439 genes common to both M. tuberculosis and M. leprae, 219 genes code for proteins that show no similarity with proteins from other organisms. Therefore, the latter 'core' genes could be specific for mycobacteria or even for the intracellular mycobacterial pathogens. To obtain more information as to whether these genes really were mycobacteria-specific, they were included in a focused macro-array, which also contained genes from previously defined regions of difference (RD) known to be absent from Mycobacterium bovis BCG relative to M. tuberculosis. Hybridization of DNA from 40 strains of the M. tuberculosis complex and in silico comparison of these genes with the near-complete genome sequences from Mycobacterium avium, Mycobacterium marinum and Mycobacterium smegmatis were undertaken to answer this question. The results showed that among the 219 conserved genes, very few were not present in all the strains tested. Some of these missing genes code for proteins of the ESAT-6 family, a group of highly immunogenic small proteins whose presence and number is variable among the genomically highly conserved members of the M. tuberculosis complex. Indeed, the results suggest that, with few exceptions, the 'core' genes conserved among M. tuberculosis H37Rv and M. leprae are also highly conserved among other mycobacterial strains, which makes them interesting potential targets for developing new specific anti-mycobacterial drugs. In contrast, the genes from RD regions showed great variability among certain members of the M. tuberculosis complex, and some new specific deletions in Mycobacterium canettii, Mycobacterium microti and seal isolates were identified and further characterized during this study. Together with the distribution of a particular 6 or 7 bp micro-deletion in the gene encoding the polyketide synthase pks15/1, these results confirm and further extend the revised phylogenetic model for the M. tuberculosis complex recently presented.

2004

The complete genome sequence of Mycobacterium bovis

Stewart Cole

Mycobacterium bovis is the causative agent of tuberculosis in a range of animal species and man, with worldwide annual losses to agriculture of $3 billion. The human burden of tuberculosis caused by the bovine tubercle bacillus is still largely unknown. M. bovis was also the progenitor for the M. bovis bacillus Calmette-Guérin vaccine strain, the most widely used human vaccine. Here we describe the 4,345,492-bp genome sequence of M. bovis AF2122/97 and its comparison with the genomes of Mycobacterium tuberculosis and Mycobacterium leprae. Strikingly, the genome sequence of M. bovis is >99.95% identical to that of M. tuberculosis, but deletion of genetic information has led to a reduced genome size. Comparison with M. leprae reveals a number of common gene losses, suggesting the removal of functional redundancy. Cell wall components and secreted proteins show the greatest variation, indicating their potential role in host-bacillus interactions or immune evasion. Furthermore, there are no genes unique to M. bovis, implying that differential gene expression may be the key to the host tropisms of human and bovine bacilli. The genome sequence therefore offers major insight on the evolution, host preference, and pathobiology of M. bovis.

2003

Macro-array and bioinformatic analyses reveal mycobacterial 'core' genes, variation in the ESAT-6 gene family and new phylogenetic markers for the Mycobacterium tuberculosis complex

Stewart Cole

2004

Comparative analysis of B- and T-cell epitopes of Mycobacterium leprae and Mycobacterium tuberculosis culture filtrate protein 10

Stewart Cole

2004