Project description:Mycobacterium tuberculosis employs several strategies to combat and adapt to adverse conditions encountered inside the host. The non-replicative dormant state of the bacterium is linked to drug resistance and slower response to anti-tubercular therapy. It is known that alterations in lipid content allow dormant bacteria to acclimatize to cellular stress. Employing comparative lipidomic analysis we profiled the changes in lipid metabolism in M. tuberculosis using a modified Wayne's model of hypoxia-induced dormancy. Further we subjected the dormant bacteria to resuscitation, and analyzed their lipidomes until the lipid profile was similar to that of normoxially grown bacteria. An enhanced degradation of cell wall-associated and cytoplasmic lipids during dormancy, and their gradual restoration during reactivation, were clearly evident. This study throws light on distinct lipid metabolic patterns that M. tuberculosis undergoes to maintain its cellular energetics during dormancy and reactivation.
Project description:Lysates of Mycobacterium tuberculosis (H37Rv auxotroph mc(2)6020) grown under various conditions (normoxia, hypoxia, reactivation from hypoxia) probed the serine hydrolase probe with ActivX-desthiobiotin FP.
Project description:Tuberculosis, caused by Mycobacterium tuberculosis, still remains a major global health problem. The main obstacle in eradicating this disease is the ability of this pathogen to remain dormant in macrophages, and to get reactivated later under immuno-compromised conditions. The physiology of hypoxic nonreplicating M. tuberculosis is well studied using many in vitro dormancy models. However, the physiological changes that take place during the shift from dormancy to aerobic growth (reactivation) have rarely been subjected to a detailed investigation. In this study, we developed an in vitro reactivation system by re-aerating bacteria that were made dormant employing Wayne’s dormancy model, and compared the proteome profiles of dormant and reactivated bacteria using label-free one-dimensional LC/MS/MS analysis.
Project description:Reaeration timecourse from a defined hypoxia model in Mycobacterium tuberculosis. The mechanism by which mycobacteria return to a replicating state upon re-exposure to favorable conditions is not well understood. In this study, we utilized reaeration from a defined hypoxia model to characterize the adaptive response of Mycobacterium tuberculosis (MTB) following a return to favorable growth conditions. Global transcriptional analysis identified the ~100 gene Reaeration Response, induced relative to both log-phase and hypoxic MTB. This response includes chaperones and proteases, as well as the transcription factor Rv2745c, a Clp protease gene regulator (ClgR) orthologue. During reaeration, genes repressed during hypoxia are also upregulated in a wave of transcription that includes genes crucial to transcription, translation and oxidative phosphorylation.
Project description:Reaeration timecourse from a defined hypoxia model in Mycobacterium tuberculosis. The mechanism by which mycobacteria return to a replicating state upon re-exposure to favorable conditions is not well understood. In this study, we utilized reaeration from a defined hypoxia model to characterize the adaptive response of Mycobacterium tuberculosis (MTB) following a return to favorable growth conditions. Global transcriptional analysis identified the ~100 gene Reaeration Response, induced relative to both log-phase and hypoxic MTB. This response includes chaperones and proteases, as well as the transcription factor Rv2745c, a Clp protease gene regulator (ClgR) orthologue. During reaeration, genes repressed during hypoxia are also upregulated in a wave of transcription that includes genes crucial to transcription, translation and oxidative phosphorylation. Each reaerating culture compared at multiple timepoints to a sample from the same culture at seven days of hypoxia. Three or more replicates at each timepoint.
Project description:The isogenic Mtb:ΔRv2745c mutant is significantly more sensitive normoxia conditions after a period of hypoxia, relative to wild-type Mtb, implicating a role for ClgR in response to reactivation, in vivo. Both hypoxia and reaeration treatment led to dysregulation of the σH regulon in the isogenic mutant, Mtb:ΔRv2745c. Induction of clgR in Mtb did lead to Clp protease induction, indicating that clgR plays a role in differntially activating downstream genes in a condition dependent manner. Disruption of genes involved in the dosR regulon, the Enduring Hypoxia Response, lipid synthesis, and mycolic acid synthesis also occurred in the knock out, implicating clgR as a possible regulator of downstream signaling cascades that facilitate Mtb survival. There was also a differnetial response of genes that are known Clp protease targets, in addition to potential Clp protease targets that had similar induction patterns as known Clp protease targets. At different time points, following hypoxia (day 1, day 5, and day 7) and reaeration (1 hour, 4 hour, 6 hour, 12 hour, 24 hour, and 48 hour) treatments M. tuberculosis CDC1551 cultures, RNA was extracted and labeled with Cy5. RNA was also extracted from pre-hypoxia (t=0) time points and labeled with Cy3. These samples were cohybridized on M. tuberculosis CDC1551 whole genome microarrays using biological triplicate samples (i.e. samples derived from three distinct cultures and treatments) and thus three unique datasets were generated for each of the three time points for Mtb. Similar experiments were performed for an isogenic Rv2745c (clgR) mutant in Mtb CDC1551 which was generated by allelic exchange.
Project description:Tuberculosis caused by Mycobacterium tuberculosis (Mtb) infection remains a huge global public health problem. One striking characteristic of Mtb is its ability to adapt to hypoxia, and thus ensuing transition to dormant state for persistent infection, but how the hypoxia responses of Mtb is regulated remains largely unknown. Here, we performed a quantitative acetylome analysis to compare the acetylation profile of Mtb under aeration and hypoxia, and showed that 377 acetylation sites in 269 proteins of Mtb were significantly change under hypoxia. Especially, deacetylation of Dormancy Survival Regulator (DosR) at K182 promoted the hypoxia response of Mtb and enhanced transcription of DosR-targeted genes. Mechanistically, recombinant DosRK182R protein demonstrated enhanced DNA-binding activity in comparison with DosRK182Q protein. Moreover, Rv0998 was identified as an acetyltransferase that mediates the acetylation of DosR at K182. Deletion of Rv0998 also promoted the adaption of Mtb to hypoxia and transcription of DosR-targeted genes. Mice infected with Mtb strain containing acetylation-defective DosRK182R or lacking Rv0998 had much lower bacterial counts, and less severe histopathological impairments compared with those infected with the wild-type strain. Our findings suggest that hypoxia induces the deacetylation of DosR, which in turn increases its DNA binding ability to promote the transcription of target genes, allowing Mtbto transit to dormancy under hypoxia.
Project description:Mycobacterium tuberculosis is the causative agent of tuberculosis, a disease that affects one-third of the world’s population. The sole extant vaccine for tuberculosis is the live attenuated Mycobacterium bovis bacille Calmette-Guerin (BCG). We examined 13 representative BCG strains from around the world to ascertain their ability to express DosR-regulated dormancy antigens. These are known to be recognized by T-cells of M. tuberculosis infected individuals, especially those harboring latent infections. Differences in expression of these antigens could be valuable for use as diagnostic markers to distinguish BCG vaccination from latent tuberculosis. We determined that all BCG strains were defective for induction of two dormancy genes, narK2 (Rv1737c) and narX (Rv1736c). NarK2 is known to be necessary for nitrate respiration during anaerobic dormancy. Analysis of the narK2/X promoter region revealed a base substitution mutation in all tested BCG strains and M. bovis in comparison to the M. tuberculosis sequence. We also show that nitrate reduction by BCG strains during dormancy was greatly reduced compared to M. tuberculosis and varied between tested strains. Several dormancy regulon transcriptional differences were also identified among the strains, as well as variation in their growth and survival. These findings demonstrate defects in DosR regulon expression during dormancy and phenotypic variation between commonly used BCG vaccine strains. 12 different BCG strains were examined as well as M. tuberculosis H37Rv and M. bovis. Two arrays per strain were analyzed, one with the addition of nitric oxide and the other utilizing hypoxia treatment, both conditions shown to induce expression of the dormancy regulon. The reference sample for each array was log phase M. tuberculosis H37Rv.
Project description:These data represent the expression patterns of Mycobacterium tuberculosis in progressive hypoxia, nutrient depletion, and in-vivo hollow fiber models of dormancy. The assumptions are that the set of genes that respond to INH treatment during Log phase growth would not be differentially regulated during INH treatment in the dormancy models, and that the overall number of differentially regulated genes would be reduced do to the low metabolic state of the cells. Keywords: Dormancy Model Drug Response Comparison
Project description:In Mycobacterium tuberculosis, the sensor kinases DosT and DosS activate the transcriptional regulator DosR, resulting in the induction of the DosR regulon, important for anaerobic survival and perhaps latent infection. The individual and collective roles of these sensors has been postulated biochemically, but their roles have remained unclear in vivo. This work demonstrates distinct and additive roles for each sensor during anaerobic dormancy. Both sensors are necessary for wild type levels of DosR regulon induction, and concomitantly, full induction of the regulon is required for wild type anaerobic survival. In the anaerobic model, DosT plays an early role, responding to hypoxia. DosT then induces the regulon and with it DosS, which sustains and further induces the regulon. DosT then loses its functionality as oxygen becomes limited, and DosS alone maintains induction of the genes from that point forward. Thus, M. tuberculosis has evolved a system whereby it responds to hypoxic conditions in a stepwise fashion as it enters an anaerobic state. Various DosS and DosT mutant strains were analyzed against wild type (reference strain H37Rv, identical conditions as mutant) under various conditions: day 6 in an anaerobic dormancy model, 4 or 24 hours in a GasPak model, or log phase with the addition of a nitric oxide donor. Experiments were repeated in triplicate or quadruplicate.