bioA mutant of Mycobacterium tuberculosis shows severe growth defect and imparts protection against tuberculosis in guinea pigs.

Owing to the devastation caused by tuberculosis along with the unsatisfactory performance of the Bacillus Calmette-Guérin (BCG) vaccine, a more efficient vaccine than BCG is required for the global control of tuberculosis. A number of studies have demonstrated an essential role of biotin biosynthesis in the growth and survival of several microorganisms, including mycobacteria, through deletion of the genes involved in de novo biotin biosynthesis. In this study, we demonstrate that a bioA mutant of Mycobacterium tuberculosis (MtbΔbioA) is highly attenuated in the guinea pig model of tuberculosis when administered aerogenically as well as intradermally. Immunization with MtbΔbioA conferred significant protection in guinea pigs against an aerosol challenge with virulent M. tuberculosis, when compared with the unvaccinated animals. Booster immunization with MtbΔbioA offered no advantage over a single immunization. These experiments demonstrate the vaccinogenic potential of the attenuated M. tuberculosis bioA mutant against tuberculosis.

Disruption of mycobactin biosynthesis leads to attenuation of Mycobacterium tuberculosis for growth and virulence.

BACKGROUND: Low iron availability in the host upregulates the mbt gene cluster of Mycobacterium tuberculosis, which is responsible for mycobactin biosynthesis. However, the biological significance of mycobactins in the growth of this pathogen and in disease progression has not been elucidated. METHODS: We have disrupted the mbtE gene (Rv2380c) in the mbt cluster to evaluate the importance of mycobactin biosynthesis in the growth and virulence of M. tuberculosis. RESULTS: The mbtE mutant (MtbΔmbtE) was unable to synthesize mycobactins, displayed an altered colony morphology, and was attenuated for growth in broth culture and in macrophages. Transmission electron microscopy revealed that MtbΔmbtE displayed an altered cell wall permeability. The growth characteristics and colony morphology of MtbΔmbtE were similar to wild type when the medium was supplemented with mycobactins or when MtbΔmbtE was genetically complemented with the mbtE gene. Moreover, guinea pigs infected with MtbΔmbtE exhibited a significantly reduced bacillary load and histopathological damage in the organs, in comparison to M. tuberculosis-infected animals. CONCLUSIONS: This study highlights the importance of mycobactins in the growth and virulence of M. tuberculosis and establishes the enzymes of mycobactin biosynthesis as novel targets for the development of therapeutic interventions against tuberculosis.

Identification of inhibitors against Mycobacterium tuberculosis thiamin phosphate synthase, an important target for the development of anti-TB drugs.

Tuberculosis (TB) continues to pose a serious challenge to human health afflicting a large number of people throughout the world. In spite of the availability of drugs for the treatment of TB, the non-compliance to 6-9 months long chemotherapeutic regimens often results in the emergence of multidrug resistant strains of Mycobacterium tuberculosis adding to the precariousness of the situation. This has necessitated the development of more effective drugs. Thiamin biosynthesis, an important metabolic pathway of M. tuberculosis, is shown to be essential for the intracellular growth of this pathogen and hence, it is believed that inhibition of this pathway would severely affect the growth of M. tuberculosis. In this study, a comparative homology model of M. tuberculosis thiamin phosphate synthase (MtTPS) was generated and employed for virtual screening of NCI diversity set II to select potential inhibitors. The best 39 compounds based on the docking results were evaluated for their potential to inhibit the MtTPS activity. Seven compounds inhibited MtTPS activity with IC(50) values ranging from 20-100 µg/ml and two of these exhibited weak inhibition of M. tuberculosis growth with MIC(99) values being 125 µg/ml and 162.5 µg/ml while one compound was identified as a very potent inhibitor of M. tuberculosis growth with an MIC(99) value of 6 µg/ml. This study establishes MtTPS as a novel drug target against M. tuberculosis leading to the identification of new lead molecules for the development of antitubercular drugs. Further optimization of these lead compounds could result in more potent therapeutic molecules against Tuberculosis.