Dataset Information

Hypoxia Is Not a Main Stress When Mycobacterium tuberculosis Is in a Dormancy-Like Long-Chain Fatty Acid Environment.

ABSTRACT: The capacity of Mycobacterium tuberculosis (Mtb) to sense, respond and adapt to a variable and hostile environment within the host makes it one of the most successful human pathogens. During different stages of infection, Mtb is surrounded by a plethora of lipid molecules and current evidence points out the relevance of fatty acids during the infectious process. In this study, we have compared the transcriptional response of Mtb to hypoxia in cultures supplemented with a mix of even long-chain fatty acids or dextrose as main carbon sources. Using RNA sequencing, we have identified differential expressed genes in early and late hypoxia, defined according to the in vitro Wayne and Hayes model, and compared the results with the exponential phase of growth in both carbon sources. We show that the number of genes over-expressed in the lipid medium was quite low in both, early and late hypoxia, relative to conditions including dextrose, with the exception of transcripts of stable and non-coding RNAs, which were more expressed in the fatty acid medium. We found that sigB and sigE were over-expressed in the early phase of hypoxia, confirming their pivotal role in early adaptation to low oxygen concentration independently of the carbon source. A drastic contrast was found with the transcriptional regulatory factors at early hypoxia. Only 2 transcriptional factors were over-expressed in early hypoxia in the lipid medium compared to 37 that were over-expressed in the dextrose medium. Instead of Rv0081, known to be the central regulator of hypoxia in dextrose, Rv2745c (ClgR), seems to play a main role in hypoxia in the fatty acid medium. The low level of genes associated to the stress-response during their adaptation to hypoxia in fatty acids, suggests that this lipid environment makes hypoxia a less stressful condition for the tubercle bacilli. Taken all together, these results indicate that the presence of lipid molecules shapes the metabolic response of Mtb to an adaptive state for different stresses within the host, including hypoxia. This fact could explain the success of Mtb to establish long-term survival during latent infection.

SUBMITTER: Del Portillo P

PROVIDER: S-EPMC6333855 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Hypoxia Is Not a Main Stress When Mycobacterium tuberculosis Is in a Dormancy-Like Long-Chain Fatty Acid Environment.

Del Portillo Patricia P García-Morales Lázaro L Menéndez María Carmen MC Anzola Juan Manuel JM Rodríguez Juan Germán JG Helguera-Repetto Addy Cecilia AC Ares Miguel A MA Prados-Rosales Rafael R Gonzalez-Y-Merchand Jorge A JA García María Jesús MJ

Frontiers in cellular and infection microbiology 20190109

The capacity of Mycobacterium tuberculosis (Mtb) to sense, respond and adapt to a variable and hostile environment within the host makes it one of the most successful human pathogens. During different stages of infection, Mtb is surrounded by a plethora of lipid molecules and current evidence points out the relevance of fatty acids during the infectious process. In this study, we have compared the transcriptional response of Mtb to hypoxia in cultures supplemented wit ...[more]

PMID: 30687646

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Project description:The capacity of Mycobacterium tuberculosis (Mtb) to sense, respond and adapt to variable and hostile environment within the host, has made it one of the most successful human pathogens. During different stages of infection, the bacillus is surrounding by a plethora of lipid rich molecules and current evidence points out the relevance of fatty acids during the Mtb infectious process. In this study, we have compared the transcriptional response of Mtb to hypoxia in cultures grown in both, a mix of even long-chain fatty acids and dextrose as carbon sources. Using RNA sequencing, we have identified the differential expressed genes in early and late hypoxia defined according to the in vitro Wayne model and compared the results with the exponential phase of growth in both carbon sources. Our results showed that, different to dextrose, the number of genes overexpressed in hypoxia in the lipid medium was quite low in both, early and late hypoxia in all functional categories describes for Mtb. The exception were the transcripts of stable and non-coding RNAs which were more expressed in the fatty acid medium. We found that SigB and SigE were overexpressed in the early phase of hypoxia, confirming their pivotal role in early adaptation to low oxygen concentration independently of the carbon source. A drastic contrast was found with the transcriptional regulatory factors at early hypoxia. Only 2 transcriptional factors were overexpressed in early hypoxia in the lipid medium compared to 37 that were overexpressed in the dextrose medium. Instead of Rv0081, known to be the central regulator of hypoxia in dextrose, Rv2745c, (ClgR), is playing a main role in hypoxia in the fatty acids medium. The low level of genes associated to stress-response, showed by Mtb during their adaptation to hypoxia in fatty acids, suggested that this lipid environment makes hypoxia a less stressful condition for the tubercle bacilli. Therefore, when the bacillus is surviving in that environment, its metabolism seemed to be already adapted to different stresses within the host, including hypoxia. This fact could explain the success of Mtb to establish long-term survival during latent infection.

Project description:UnlabelledStrong evidence supports the idea that fatty acids rather than carbohydrates are the main energy source of Mycobacterium tuberculosis during infection and latency. Despite that important role, a complete scenario of the bacterium's metabolism when lipids are the main energy source is still lacking. Here we report the development of an in vitro model to analyze adaptation of M. tuberculosis during assimilation of long-chain fatty acids as sole carbon sources. The global lipid transcriptome revealed a shift toward the glyoxylate cycle, the overexpression of main regulators whiB3, dosR, and Rv0081, and the increased expression of several genes related to reductive stress. Our evidence showed that lipid storage seems to be the selected mechanism used by M. tuberculosis to ameliorate the assumed damage of reductive stress and that concomitantly the bacilli acquired a slowed-growth and drug-tolerant phenotype, all characteristics previously associated with the dormant stage. Additionally, intergenic regions were also detected, including the unexpected upregulation of tRNAs that suggest a new role for these molecules in the acquisition of a drug-tolerant phenotype by dormant bacilli. Finally, a set of lipid signature genes for the adaptation process was also identified. This in vitro model represents a suitable condition to illustrate the participation of reductive stress in drugs' activity against dormant bacilli, an aspect scarcely investigated to date. This approach provides a new perspective to the understanding of latent infection and suggests the participation of previously undetected molecules.ImportanceMycobacterium tuberculosis establishes long-lasting highly prevalent infection inside the human body, called latent tuberculosis. The known involvement of fatty acids is changing our understanding of that silent infection; however, question of how tubercle bacilli globally adapt to a lipid-enriched environment is still an unanswered. With the single change of providing fatty acids as carbon sources, the bacilli switch on their program related to dormant stage: slowed growth, accumulation of lipid bodies, and development of drug tolerance. In this stage, unexpected and previously unknown participants were found to play putatively important roles during the process. For the first time, this work compares the global transcriptomics of bacteria by using strand-specific RNA sequencing under two different growth conditions. This study suggests novel targets for the control of tuberculosis and provides a new straightforward in vitro model that could help to test the activity of drugs against dormant bacilli from a novel perspective.

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 then reactivate 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 the virulent laboratory strain of M. tuberculosis that was 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. The proteome of dormant bacteria was analyzed at nonreplicating persistent stage 1 (NRP1) and stage 2 (NRP2), whereas that of reactivated bacteria was analyzed at 6 and 24 h post re-aeration. Proteome of normoxially grown bacteria served as the reference. In total, 1871 proteins comprising 47% of the M. tuberculosis proteome were identified, and many of them were observed to be expressed differentially or uniquely during dormancy and reactivation. The number of proteins detected at different stages of dormancy (764 at NRP1, 691 at NRP2) and reactivation (768 at R6 and 983 at R24) was very low compared with that of the control (1663). The number of unique proteins identified during normoxia, NRP1, NRP2, R6, and R24 were 597, 66, 56, 73, and 94, respectively. We analyzed various biological functions during these conditions. Fluctuation in the relative quantities of proteins involved in energy metabolism during dormancy and reactivation was the most significant observation we made in this study. Proteins that are up-regulated or uniquely expressed during reactivation from dormancy offer to be attractive targets for therapeutic intervention to prevent reactivation of latent tuberculosis.

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Hypoxia Is Not a Main Stress When Mycobacterium tuberculosis Is in a Dormancy-Like Long-Chain Fatty Acid Environment.

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Hypoxia Is Not a Main Stress When <i>Mycobacterium tuberculosis</i> Is in a Dormancy-Like Long-Chain Fatty Acid Environment.

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