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Mycobacterium tuberculosis gene expression during adaptation to stationary phase and low-oxygen dormancy

ABSTRACT: The innate mechanisms used by Mycobacterium tuberculosis to persist during periods of non-proliferation are central to understanding the physiology of the bacilli during latent disease. We have used whole genome expression profiling to expose adaptive mechanisms initiated by M. tuberculosis in two common models of M. tuberculosis non-proliferation. The first of these models was a standard growth curve in which gene expression changes were followed from exponential growth through the transition to stationary phase. In the second model, we followed the adaptive process of M. tuberculosis during transition from aerobic growth to a state of anaerobic non-replicating persistence. The most striking finding from these experiments was the strong induction of the entire DosR dormancy regulon over approximately 20 days during the long transition to an anaerobic state. This is contrasted by the muted overall response to aerated stationary phase with only a partial dormancy regulon response. From the results presented here we conclude that the respiration-limited environment of the oxygen-depleted NRP model recreates at least one fundamental factor for which the genome of M. tuberculosis encodes a decisive adaptive program. Keywords: comparative genome hybridization design and stimulus or stress design

ORGANISM(S): Mycobacterium tuberculosis

PROVIDER: GSE8786 | GEO | 2007/08/15

SECONDARY ACCESSION(S): PRJNA102083

REPOSITORIES: GEO

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Project description:A comparative transcriptome approach was used to assess genes involved in metabolism and pathogenesis that are specifically activated during anaerobic growth of the spore-forming food-borne human pathogen Bacillus cereus ATCC 14579. Growth under anaerobic conditions in Brain Heart Infusion broth revealed a reduced growth rate and a lower yield as compared to that under aerobic conditions. Comparative transcriptome analysis of cells harvested at early- and mid-exponential growth phase, transition phase and stationary phase, subsequently showed hundreds of genes to be induced under anaerobic condition. These included novel genes identified for anaerobic growth of B. cereus, encoding metabolic pathways, such as the arginine deiminase pathway (ArcABDC), a formate dehydrogenase (FdhF) and a pyruvate fomate lyase (Pfl), and alternative respiratory proteins, such as arsenate reductases. Furthermore, the nitrosative stress response was induced in the anaerobic transition phase of growth, conceivably due to the production of nitric oxide as a by-product of nitrite and nitrate respiration. Notably, both hemolytic enzyme and enterotoxin encoding genes were activated in different oxygen limiting conditions, i.e. hemolytic enzyme encoding genes were induced during anaerobic growth, whereas enterotoxin encoding genes were induced in the transition and stationary phase of aerobic cultures reaching a high cell density. These data point to metabolic rearrangements, stress adaptation and activation of the virulent status of B. cereus under anaerobic conditions, such as encountered in the human GI-tract. B. cereus ATCC 14579 was grown in BHI in 50 ml. Aerobic in a Erlenmeyer flask, shaking at 200 rpm. Anaerobic in a closed flask, flushed with Nitrogen-gas for 30 min, also shaking at 200 rpm. Transcriptome analyses Phase compared to mid-exponential phase Anaerobic (OD600) 0.2 compared to 0.4 Early-exponential 1.0 compared to 0.4 Transition 1.1 compared to 0.4 Stationary Aerobic (OD600) 0.2 compared to 0.8 Early-exponential 4.0 compared to 0.8 Transition 8.0 compared to 0.8 Stationary Aerobic to anaerobic (OD600) Anaerobic 0.6 to aerobic 0.6

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Mycobacterium tuberculosis gene expression during adaptation to stationary phase and low-oxygen dormancy

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