Project description:Respiratory ATP-synthesis is at present the only known mechanism for ATP synthesis in Mtb. This makes Mtb particularly vulnerable to inhibition of respiratory ATP synthase inhibitors such as TMC207, a novel compound for treatment of tuberculosis. We now provide first evidence that Mtb possesses a pathway that is fermentative in nature that could compensate lack of respiratory ATP synthesis. We identified acetate as a fermentation product in Mtb. Production of acetate was mediated by phosphotransacetylase (Pta) and acetate kinase (AckA). In acetate fermenting Mtb cultures, ATP levels remained stable despite inhibition of respiratory ATP synthase. Deletion of the PtaAckA pathway in Mtb decreased ATP content and impaired survival. This study provides evidence that in Mtb substrate level phosphorylation can compensate lack of oxidative phosphorylation, and thus facilitates survival of Mtb in the absence of respiration. Acetate fermentation contributes to adaptation to respiration-limiting conditions, and plays an important role in the emerging field of fermentative metabolism of Mtb.
Project description:Respiratory ATP-synthesis is at present the only known mechanism for ATP synthesis in Mtb. This makes Mtb particularly vulnerable to inhibition of respiratory ATP synthase inhibitors such as TMC207, a novel compound for treatment of tuberculosis. We now provide first evidence that Mtb possesses a pathway that is fermentative in nature that could compensate lack of respiratory ATP synthesis. We identified acetate as a fermentation product in Mtb. Production of acetate was mediated by phosphotransacetylase (Pta) and acetate kinase (AckA). In acetate fermenting Mtb cultures, ATP levels remained stable despite inhibition of respiratory ATP synthase. Deletion of the PtaAckA pathway in Mtb decreased ATP content and impaired survival. This study provides evidence that in Mtb substrate level phosphorylation can compensate lack of oxidative phosphorylation, and thus facilitates survival of Mtb in the absence of respiration. Acetate fermentation contributes to adaptation to respiration-limiting conditions, and plays an important role in the emerging field of fermentative metabolism of Mtb. We performed DNA microarray analysis to validate the reduction of oxygen concentration by comparing aerobic and hypoxic cultures. RNA was prepared from Mtb after two days of cultivation in aerobic and in hypoxic cultures. At each condition, Mtb were cultured in medium supplemented with glycerol and glucose. Labelled cDNA from three independent experiments was subjected to array analysis.
Project description:Interferon (IFN)-γ-producing CD8+ T cells are involved in control of Mycobacterium tuberculosis (Mtb) infection, in part by promoting antimicrobial activities of macrophages. Whether Mtb counters these responses, particularly during the hypoxic conditions that arise within granulomas during infection, remains unknown. Using metabolomic, proteomic and genetic approaches, here we show that Mtb induces Rv0884c (SerC), a Mtb phosphoserine aminotransferase, to produce D-serine. This activity increased Mtb pathogenesis in mice but did not directly affect intramacrophage Mtb survival. Instead, D-serine inhibited IFN-γ production by CD8+ T cells, which indirectly reduced the ability of macrophages to restrict Mtb upon coculture. Mechanistically, D-serine interacted with WDR24, a subunit of GATOR2, and inhibited mTORC1 activation in T cells. This decreased T-bet transcription factor expression by CD8+ T cells and reduced IFN-γ production. Our findings suggest a mechanism of mycobacterial metabolic adaptation to hypoxia which leads to amino acid-dependent suppression of adaptive anti-TB immunity.
Project description:Mycobacterium tuberculosis (Mtb) is evolutionarily equipped to resist exogenous reactive oxygen species but shows vulnerability to an increase in endogenous ROS (eROS). Since eROS is an unavoidable consequence of aerobic metabolism, understanding how Mtb manages eROS levels is essential yet needs to be characterized. By combining the Mrx1-roGFP2 redox biosensor with transposon mutagenesis, we identified 368 genes (redoxosome) responsible for maintaining homeostatic levels of eROS in Mtb. Integrating redoxosome with a global network of transcriptional regulators revealed a hypothetical protein (Rv0158) as a critical node managing eROS in Mtb. Disruption of rv0158 (rv0158 KO) impaired growth, redox balance, respiration, and metabolism of Mtb on glucose but not on fatty acids. Importantly, rv0158 KO exhibited enhanced growth on propionate, and the Rv0158 protein directly binds to methylmalonyl-CoA, a key intermediate in propionate catabolism. Metabolite profiling, ChIP-Seq, and gene-expression analyses indicate that Rv0158 manages metabolic neutralization of propionate toxicity by regulating the methylcitrate cycle. Disruption of rv0158 enhanced the sensitivity of Mtb to oxidative stress, nitric oxide, and anti-TB drugs. Lastly, rv0158 KO showed poor survival in macrophages and persistence defect in mice. Our results suggest that Rv0158 is a metabolic integrator for carbon metabolism and redox balance in Mtb.
Project description:Circular RNAs (circRNAs) play a critical role in pathological mechanisms of Mycobacterium tuberculosis (Mtb) and can be used as a new biomarker for active tuberculosis (ATB) diagnosis. Therefore, we identified significantly dysregulated circRNAs in ATB patients and healthy controls (HC) and explored its molecular mechanism. We found that hsa_circ_0002371 was significantly up-regulated in PBMCs of ATB patients and H37Rv- or BCG-infected THP-1 human macrophages. Functional experiments demonstrated that hsa_circ_0002371 inhibited autophagy of BCG-infected THP-1 human macrophages and promoted intracellular BCG survival rate. Mechanistically, hsa_circ_0002371 promoted the expression of hsa-miR-502-5p, and hsa_circ_0002371 overexpression-induced protective effects in BCG-infected THP-1 human macrophages was largely overturned by the inhibition of hsa-miR-502-5p. Notably, hsa-miR-502-5p inhibited autophagy via suppressing autophagy related 16 like 1 (ATG16L1) in BCG-infected macrophages and thus promoting intracellular BCG growth. In summation, hsa_circ_0002371 increased the suppression of hsa-miR-502-5p on ATG16L1 and inhibited autophagy to promote Mtb growth in macrophages. In Conclusion, our data suggested that hsa_circ_0002371 was significantly up-regulated in the PBMCs of ATB patients compared with HC. The hsa_circ_0002371/hsa-miR-502-5p/ATG16L1 axis promoted the survival of intracellular Mtb and inhibited autophagy in macrophages. Our findings suggested hsa_circ_0002371 could act as a potential diagnostic biomarker and therapeutic target.
Project description:Mycobacterium tuberculosis (Mtb) displayed cording phenotypes during intracellular infection. RNA-Seq was used to identify transcriptional programmes expressed by hLEC that actviates pathways relating to cellular pro-survival and cyosolic surveillance of intracellular Mtb. Mtb cording was found to be a mechanism to evade xenophagy in the cytosol of endothelial cells.
Project description:Lactococcus lactis is the main bacterium used for food fermentation and is a candidate for probiotic development. In addition to fermentation growth, supplementation with heme in aerobic conditions activates a cytochrome oxidase, which promotes respiration metabolism. In contrast to fermentation in which cells consume energy to produce mainly lactic acid, respiration metabolism dramatically changes energy metabolism, such that massive amounts of acetic acid and acetoin are produced at the expense of lactic acid. Our goal was to investigate the metabolic changes that correlate with significantly improved growth and survival during respiration growth. Using transcriptional time course analyses, mutational analyses, and promoter reporter fusions, we uncover two main pathways that can explain the robust growth and stability of respiration cultures: The acetate pathway contributes to biomass yield in respiration, without affecting medium pH. The acetoin pathway allows cells to cope with internal acidification, which directly affects cell density and survival in stationary phase. Our results suggest that manipulation of these pathways could lead to fine tuning respiration growth, with improved yield and stability.
Project description:The world’s second deadliest disease tuberculosis is caused by the organism Mycobacterium tuberculosis. Mtb has 4173 genes (Mycobrowser) and some of these genes are essential for its survival. There are many uncharacterized genes in Mtb which play an important role in its survival strategies to combat the immune system of the host. In order to identify vital genes required for its survival were characterized by in silico approach. Based on computational analysis, we have identified 2 proteins which are only present in Mtb complex and named as Signature Protein 1 & 2. The Signature protein 2 (Rv000) has DNA methyltransferase activity and also protects the DNA from DNase-I digestion. Knock in of this gene in Mycobacterium smegmatis modulates its transcriptome and thereby enhances the survival. RNA seq analysis of M. smegmatis showed that more than 3000 genes were up regulated at the transcriptional level. These results suggested that the gene encoding signature protein 2 (Rv000) is acting as a global transcriptional regulators. These genes encode proteins that belong to different categories of biological and molecular function i.e. transcriptional regulators, regulatory proteins, conserved hypothetical proteins, transporter proteins (ABC transporters, antiporter, sugar transporter and Major facilitator superfamily genes) and TonB dependent receptors (required for iron scavenging) were upregulated. The proteins encoded by these genes may be targeted for drug development against Mtb..
Project description:During lung infection Mycobacterium tuberculosis (Mtb) resides in macrophages and subverts the bactericidal mechanisms of these professional phagocytes. In this work we have analyzed by DNA microarray technique the global transcription profile of Mtb infecting primary human macrophages in order to identify putative bacterial pathogenic factors that can be relevant for the intracellular survival of Mtb. Keywords: time course
Project description:During lung infection Mycobacterium tuberculosis (Mtb) resides in macrophages and subverts the bactericidal mechanisms of these professional phagocytes. In this work we have analyzed by DNA microarray technique the global transcription profile of Mtb infecting primary human macrophages in order to identify putative bacterial pathogenic factors that can be relevant for the intracellular survival of Mtb. Keywords: time course We compared the global gene expression of the H37Rv strain of Mtb after 4 hours and 24 hours of infection of human macrophage-like THP-1 cells with the gene expression profile of the strain growing exponentially in broth cultures.