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The response of Mycobacterium tuberculosis to reactive oxygen and nitrogen species

ABSTRACT: The bacteriostatic and bactericidal effects and the corresponding expression profiles of Mycobacterium tuberculosis to representative oxidative and nitrosative stresses were investigated by growth and survival studies and whole genome expression analysis. The response of M. tuberculosis to a range of hydrogen peroxide (H2O2) concentrations tended to fall into three distinct categories: (1) low level exposure resulted in induction of few H2O2 sensitive genes, (2) intermediate exposure resulted in massive transcriptional changes without an effect on growth or survival, and (3) high exposure resulted in a muted transcriptional response and eventual death. Nitric oxide (NO) exposure initiated much of the same transcriptional response as H2O2. However, unlike H2O2 exposure, NO exposure affected a dose-dependent bacteriostatic activity without killing and induction of dormancy-related genes. Included in the shared response to H2O2 and NO was the induction of genes encoding oxidative stress detoxification and iron-sulfur cluster repair functions. Expression of several key oxidative stress defense genes was constitutive, or increased moderately from an already elevated level, suggesting bacilli that are continually primed for oxidative stress defense. Deletion of the known oxidative stress responsive regulator, FurA, resulted in the constitutive expression of furA, katG, and Rv1907c; while other genes do not appear to be solely controlled by FurA. In contrast to Escherichia coli, M. tuberculosis appears highly resistant to DNA damage-dependent killing caused by low mill molar levels of H2O2. Furthermore, instead of limiting access to iron to prevent hydroxyl radical formation from H2O2 and thus DNA damage, M. tuberculosis induced iron uptake genes in response to H2O2 and NO. Set of arrays that are part of repeated experiments Compound Based Treatment: H2O2 or DETA/NO treatment

ORGANISM(S): Mycobacterium tuberculosis

SUBMITTER: Martin Voskuil

PROVIDER: E-GEOD-16146 | biostudies-arrayexpress |

REPOSITORIES: biostudies-arrayexpress

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Project description:Background: Conflicting results have been reported about the role of the two-component sensor and transcriptional regulator DosS/DosR, controlling the expression of the dormancy DosR regulon, for in vivo virulence of M. tuberculosis. Here, we have used a new approach to further analyze the relevance of the dosRS system, by driving DosR (Rv3133c) expression under the control of a constitutive promoter (phsp60). Methodology/Principal Findings: M. tuberculosis H37Rv constitutively expressing the transcriptional regulator DosR (Mtb::DosR) was compared to wild type M. tuberculosis (Mtb+/+) for in vitro growth kinetics and expression of the target genes of the DosR dormancy regulon, for in vivo virulence and for immunogenicity in mice. Under aerobic conditions, hsp60-driven DosR induced the expression of 28 out of 39 tested DosR regulon genes. In vitro growth characteristics were comparable for both strains, but Mtb::DosR showed an attenuated in vivo phenotype in immunocompetent mice, as indicated by reduced bacterial replication, reduced pulmonary immunopathology, reduced cachexia and significantly prolonged survival time as compared Mtb+/+. In immunodeficient SCID mice, Mtb::DosR was fully virulent. RT-qPCR analysis revealed a strong and comparable pulmonary TNF-?? and IL-23 expression following intratracheal infection, whereas IL-12 and IL-17 expression was slightly higher with wild type Mtb+/+. Finally, mice persistently infected with Mtb::DosR for 8 months showed five to tenfold higher lung IFN-?? responses against ten of the 48 DosR regulon encoded antigens (Rv1733c, Rv1734, Rv1738, Rv1996, Rv1997, Rv2029c, Rv2623, Rv2627c, Rv2628 and Rv3127) than mice actively infected with Mtb+/+. In spleen however, DosR regulon encoded antigen specific IFN-?? responses were similar in both groups. Conclusions/Significance. Collectively, these results suggest that increased DosR regulon encoded antigen specific pulmonary T cell responses are responsible for the attenuated phenotype of Mtb::DosR and that infection with Mtb::DosR could be used as a new animal model for studying key aspects of latent tuberculosis. Set of arrays that are part of repeated experiments

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The response of Mycobacterium tuberculosis to reactive oxygen and nitrogen species

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