Key Role for the Alternative Sigma Factor, SigH, in the Intracellular Life of Mycobacterium avium subsp. paratuberculosis during Macrophage Stress
Copyright policy )Key Role for the Alternative Sigma Factor, SigH, in the Intracellular Life of Mycobacterium avium subsp. paratuberculosis during Macrophage Stress
ABSTRACT Mycobacterium avium subsp. paratuberculosis causes Johne's disease, an enteric infection in cattle and other ruminants, greatly afflicting the dairy industry worldwide. Once inside the cell, M. avium subsp. paratuberculosis is known to survive harsh microenvironments, especially those inside activated macrophages. To improve our understanding of M. avium subsp. paratuberculosis pathogenesis, we examined phagosome maturation associated with transcriptional responses of M. avium subsp. paratuberculosis during macrophage infection. Monitoring cellular markers, only live M. avium subsp. paratuberculosis bacilli were able to prevent phagosome maturation and reduce its acidification. On the transcriptional level, over 300 M. avium subsp. paratuberculosis genes were significantly and differentially regulated in both naive and IFN-γ-activated macrophages. These genes include the sigma factor H ( sigH ) that was shown to be important for M. avium subsp. paratuberculosis survival inside gamma interferon (IFN-γ)-activated bovine macrophages. Interestingly, an sigH -knockout mutant showed increased sensitivity to a sustained level of thiol-specific oxidative stress. Large-scale RNA sequence analysis revealed that a large number of genes belong to the sigH regulon, especially following diamide stress. Genes involved in oxidative stress and virulence were among the induced genes in the sigH regulon with a putative consensus sequence for SigH binding that was recognized in a subset of these genes ( n = 30), suggesting direct regulation by SigH. Finally, mice infections showed a significant attenuation of the Δ sigH mutant compared to its parental strain, suggesting a role for sigH in M. avium subsp. paratuberculosis virulence. Such analysis could identify potential targets for further testing as vaccine candidates against Johne's disease.
- University of Wisconsin–Madison United States
- University of Wisconsin System United States
- University of Wisconsin–Oshkosh United States
- Cairo University Egypt
Mice, Inbred BALB C, Macrophages, Mycobacterium smegmatis, Chromosome Mapping, Sigma Factor, Gene Expression Regulation, Bacterial, Chromosomes, Bacterial, Hydrogen-Ion Concentration, Regulon, Cell Line, Specific Pathogen-Free Organisms, Mycobacterium avium subsp. paratuberculosis, Mice, Bacterial Proteins, Phagosomes, Paratuberculosis, Escherichia coli, Animals, Cattle, Female
Mice, Inbred BALB C, Macrophages, Mycobacterium smegmatis, Chromosome Mapping, Sigma Factor, Gene Expression Regulation, Bacterial, Chromosomes, Bacterial, Hydrogen-Ion Concentration, Regulon, Cell Line, Specific Pathogen-Free Organisms, Mycobacterium avium subsp. paratuberculosis, Mice, Bacterial Proteins, Phagosomes, Paratuberculosis, Escherichia coli, Animals, Cattle, Female
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