scholarly journals A Mycobacterium tuberculosis Rpf Double-Knockout Strain Exhibits Profound Defects in Reactivation from Chronic Tuberculosis and Innate Immunity Phenotypes

2008 ◽  
Vol 76 (9) ◽  
pp. 4269-4281 ◽  
Author(s):  
Eleanor Russell-Goldman ◽  
Jiayong Xu ◽  
Xiaobing Wang ◽  
John Chan ◽  
JoAnn M. Tufariello
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Axenic Culture ◽  
Colony Morphology ◽  
Double Knockout ◽  
Drug Induced ◽  
Necrosis Factor Alpha ◽  
Knockout Strain ◽  
Primary Mouse

ABSTRACT Resuscitation-promoting factors (Rpfs), apparent peptidoglycan hydrolases, have been implicated in the reactivation of dormant bacteria. We previously demonstrated that deletion of rpfB impaired reactivation of Mycobacterium tuberculosis in a mouse model. Because M. tuberculosis encodes five Rpf paralogues, redundant functions among the family members might obscure rpf single-knockout phenotypes. A series of rpf double knockouts were therefore generated. One double mutant, ΔrpfAB, exhibited several striking phenotypes. Consistent with the proposed cell wall-modifying function of Rpfs, ΔrpfAB exhibited an altered colony morphology. Although ΔrpfAB grew comparably to the parental strain in axenic culture, in vivo it exhibited deficiency in reactivation induced in C57BL/6 mice by the administration of nitric oxide synthase inhibitor (aminoguanidine) or by CD4+ T-cell depletion. Notably, the reactivation deficiency of ΔrpfAB was more severe than that of ΔrpfB in aminoguanidine-treated mice. A similar deficiency was observed in ΔrpfAB reactivation from a drug-induced apparently sterile state in infected NOS2−/− mice upon cessation of antimycobacterial therapy. Secondly, ΔrpfAB showed a persistence defect not seen with the ΔrpfB or ΔrpfA single mutants. Interestingly, ΔrpfAB exhibited impaired growth in primary mouse macrophages and induced higher levels of the proinflammatory cytokines tumor necrosis factor alpha and interleukin 6. Simultaneous reintroduction of rpfA and rpfB into the double-knockout strain complemented the colony morphology and macrophage cytokine secretion phenotypes. Phenotypes related to cell wall composition and macrophage responses suggest that M. tuberculosis Rpfs may influence the outcome of reactivation, in part, by modulating innate immune responses to the bacterium.

scholarly journals Synthetic Lethality Reveals Mechanisms of Mycobacterium tuberculosis Resistance to β-Lactams

mBio ◽  
2014 ◽  
Vol 5 (5) ◽  
Author(s):  
Shichun Lun ◽  
David Miranda ◽  
Andre Kubler ◽  
Haidan Guo ◽  
Mariama C. Maiga ◽  
...  
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Synthetic Lethality ◽  
Multidrug Resistant ◽  
Cell Wall Biosynthesis ◽  
Drug Resistant ◽  
Content Type ◽  
Innate Resistance ◽  
Extensively Drug Resistant

ABSTRACT Most β-lactam antibiotics are ineffective against Mycobacterium tuberculosis due to the microbe’s innate resistance. The emergence of multidrug-resistant (MDR) and extensively drug-resistant (XDR) strains has prompted interest to repurpose this class of drugs. To identify the genetic determinants of innate β-lactam resistance, we carried out a synthetic lethality screen on a transposon mutant library for susceptibility to imipenem, a carbapenem β-lactam antibiotic. Mutations in 74 unique genes demonstrated synthetic lethality. The majority of mutations were in genes associated with cell wall biosynthesis. A second quantitative real-time PCR (qPCR)-based synthetic lethality screen of randomly selected mutants confirmed the role of cell wall biosynthesis in β-lactam resistance. The global transcriptional response of the bacterium to β-lactams was investigated, and changes in levels of expression of cell wall biosynthetic genes were identified. Finally, we validated these screens in vivo using the MT1616 transposon mutant, which lacks a functional acyl-transferase gene. Mice infected with the mutant responded to β-lactam treatment with a 100-fold decrease in bacillary lung burden over 4 weeks, while the numbers of organisms in the lungs of mice infected with wild-type bacilli proliferated. These findings reveal a road map of genes required for β-lactam resistance and validate synthetic lethality screening as a promising tool for repurposing existing classes of licensed, safe, well-characterized antimicrobials against tuberculosis. IMPORTANCE The global emergence of multidrug-resistant and extensively drug-resistant M. tuberculosis strains has threatened public health worldwide, yet the pipeline of new tuberculosis drugs under development remains limited. One strategy to cope with the urgent need for new antituberculosis agents is to repurpose existing, approved antibiotics. The carbapenem class of β-lactam antibiotics has been proposed as one such class of drugs. Our study identifies molecular determinants of innate resistance to β-lactam drugs in M. tuberculosis, and we demonstrate that functional loss of one of these genes enables successful treatment of M. tuberculosis with β-lactams in the mouse model.

scholarly journals InhA inhibitors have activity against non-replicating Mycobacterium tuberculosis

PLoS ONE ◽  
2020 ◽  
Vol 15 (11) ◽  
pp. e0239354
Author(s):  
Lindsay Flint ◽  
Aaron Korkegian ◽  
Tanya Parish
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Nutrient Starvation ◽  
Cell Wall Biosynthesis

We previously identified a diazaborine series with potential for development as a new tuberculosis drug. This series has activity in vitro and in vivo and targets cell wall biosynthesis via inhibition of InhA. The overall aim of this study was to determine whether InhA inhibitors have activity against non-replicating Mycobacterium tuberculosis. We tested the ability of two molecules of the diazaborine series to kill non-replicating M. tuberculosis in the nutrient starvation model; both molecules were bactericidal, reducing viability by >3 logs in 21 days. Activity showed similar kill rates to other InhA inhibitors (isoniazid and NITD-916). We conclude that inhibition of InhA is bactericidal against nutrient-starved non-replicating M. tuberculosis.

scholarly journals The aceE involves in mycolic acid synthesis and biofilm formation in Mycobacterium smegmatis

2020 ◽  
Author(s):  
Suting Chen ◽  
Tianlu Teng ◽  
Shuan Wen ◽  
Tingting Zhang ◽  
Hairong Huang
Keyword(s):  
Cell Wall ◽  
Biofilm Formation ◽  
Morphological Changes ◽  
Acid Synthesis ◽  
Mycolic Acid ◽  
Colony Morphology ◽  
Wall Structure ◽  
Wild Type ◽  
Mycobacterial Cell Wall

Abstract Background: The integrity of cell wall structure is highly significant for the in vivo survival for mycobacteria. However, the mechanisms underlying the biosynthesis of mycobacterial cell wall remain poorly understood. aceE encodes the E1 component of pyruvate dehydrogenase (PDH)complex. This study aimed to know the functional role of aceE gene in cell wall biosynthesis in M. smegmatis.Results: We observed that the colony morphology of aceE-deficient mutants(aceE-mut)was quite different from the wild-type(WT) strain during the transposon library screening of M.smegmatis, smaller and smoother on the solid culture medium. Notably, the aceE-mut lost its ability of growing aggregately and biofilm forming, which are two very important features of mycobacteria.The morphological changes of the aceE-mut strain were further confirmed by electron microscopy that presented shorter, smoother and thinner images in contrast withWT strain.Additionally, the analysis of mycolic acid(MA)using LC-MS indicated deficiency of alpha-MA and epoxy-MA in aceE-mut strain whereas complementation of the aceE-mut with a wild-type aceEgene restored the composition of MA. Conclusions: Overall, this study indicates that aceE gene plays a significant role in the mycolic acid synthesis and affects the colony morphology and biofilm formation of M.smegmatis.

scholarly journals Abolishing Cell Wall Glycosylphosphatidylinositol-Anchored Proteins in Candida albicans Enhances Recognition by Host Dectin-1

2015 ◽  
Vol 83 (7) ◽  
pp. 2694-2704 ◽  
Author(s):  
Hui Shen ◽  
Si Min Chen ◽  
Wei Liu ◽  
Fang Zhu ◽  
Li Juan He ◽  
...  
Keyword(s):  
Cell Wall ◽  
Candida Albicans ◽  
Fungal Infections ◽  
Nuclear Factor Κb ◽  
Mitogen Activated Protein Kinase ◽  
Host Recognition ◽  
Necrosis Factor Alpha ◽  
Content Type ◽  
Opportunistic Human Pathogen

Fungi can shield surface pathogen-associated molecular patterns (PAMPs) for evading host immune attack. The most common and opportunistic human pathogen,Candida albicans, can shield β-(1 3)-glucan on the cell wall, one of the major PAMPs, to avoid host phagocyte Dectin-1 recognition. The way to interfere in the shielding process for more effective antifungal defense is not well established. In this study, we found that deletion of theC. albicansGPI7gene, which was responsible for adding ethanolaminephosphate to the second mannose in glycosylphosphatidylinositol (GPI) biosynthesis, could block the attachment of most GPI-anchored cell wall proteins (GPI-CWPs) to the cell wall and subsequently unmask the concealed β-(1,3)-glucan. Neutrophils could kill the uncloakedgpi7mutant more efficiently with an augmented respiratory burst. Thegpi7mutant also stimulated Dectin-1-dependent immune responses of macrophages, including activation of nuclear factor-κB (NF-κB) and mitogen-activated protein kinase (MAPK) pathways and secretion of specific cytokines, such as tumor necrosis factor alpha (TNF-α), interleukin 6 (IL-6), and IL-12p40. Furthermore, thegpi7null mutant could induce an enhanced inflammatory response through promoting significant recruitment of neutrophils and monocytes and could stimulate stronger Th1 and Th17 cell responses to fungal infectionsin vivo. Thesein vivophenotypes also were Dectin-1 dependent. Thus, we assume that GPI-CWPs are involved in the immune mechanism ofC. albicansescaping from host recognition by Dectin-1. Our studies also indicate that the blockage of GPI anchor synthesis is a strategy to inhibitC. albicansevading host recognition.

scholarly journals Regulation of Mycobacterium tuberculosis whiB3 in the Mouse Lung and Macrophages

2006 ◽  
Vol 74 (11) ◽  
pp. 6449-6457 ◽  
Author(s):  
N. Banaiee ◽  
W. R. Jacobs ◽  
J. D. Ernst
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Mouse Lung ◽  
Wild Type ◽  
Necrosis Factor Alpha ◽  
Environmental Signals ◽  
Immunodeficient Mice ◽  
Reverse Transcription Pcr ◽  
Factor Alpha

ABSTRACT Mycobacterium tuberculosis is a highly successful human pathogen, with ∼2 × 109 individuals infected globally. To understand the responses of M. tuberculosis to the in vivo environment, we studied the in vivo regulation of M. tuberculosis genes whose M. marinum homologs are induced in chronically infected frog tissues. The expression of 16S rRNA was shown to remain constant in M. tuberculosis under in vivo and in vitro conditions and therefore could be used for internal normalization in quantitative reverse transcription-PCR assays. We found whiB3, a putative transcriptional regulator implicated in mediating tissue damage, to be maximally induced at 2 weeks postinfection in the lungs of wild-type and immunodeficient (gamma interferon receptor−/−, Rag1−/−, and tumor necrosis factor alpha−/−) mice. At later time points in wild-type mice, whiB3 induction was decreased and gradually declined over the course of infection. In immunodeficient mice, whiB3 induction declined rapidly and was completely abolished in moribund animals. whiB3 was also found to be induced in naïve bone marrow-derived macrophages after 6 h of infection. whiB3 expression in vivo and in vitro was found to be inversely correlated with bacterial density. These results indicate that M. tuberculosis regulates the expression of whiB3 in response to environmental signals present in vivo and are consistent with a model of regulation by quorum sensing.

scholarly journals TLR9 regulates Th1 responses and cooperates with TLR2 in mediating optimal resistance to Mycobacterium tuberculosis

2005 ◽  
Vol 202 (12) ◽  
pp. 1715-1724 ◽  
Author(s):  
Andre Bafica ◽  
Charles A. Scanga ◽  
Carl G. Feng ◽  
Cynthia Leifer ◽  
Allen Cheever ◽  
...  
Keyword(s):  
Mycobacterium Tuberculosis ◽  
Ex Vivo ◽  
Double Knockout ◽  
Susceptibility To Infection ◽  
Pathogen Challenge ◽  
In Vitro Response ◽  
Ifn Γ ◽  
Aerosol Infection

To investigate the role of Toll-like receptor (TLR)9 in the immune response to mycobacteria as well as its cooperation with TLR2, a receptor known to be triggered by several major mycobacterial ligands, we analyzed the resistance of TLR9−/− as well as TLR2/9 double knockout mice to aerosol infection with Mycobacterium tuberculosis. Infected TLR9−/− but not TLR2−/− mice displayed defective mycobacteria-induced interleukin (IL)-12p40 and interferon (IFN)-γ responses in vivo, but in common with TLR2−/− animals, the TLR9−/− mice exhibited only minor reductions in acute resistance to low dose pathogen challenge. When compared with either of the single TLR-deficient animals, TLR2/9−/− mice displayed markedly enhanced susceptibility to infection in association with combined defects in proinflammatory cytokine production in vitro, IFN-γ recall responses ex vivo, and altered pulmonary pathology. Cooperation between TLR9 and TLR2 was also evident at the level of the in vitro response to live M. tuberculosis, where dendritic cells and macrophages from TLR2/9−/− mice exhibited a greater defect in IL-12 response than the equivalent cell populations from single TLR9-deficient animals. These findings reveal a previously unappreciated role for TLR9 in the host response to M. tuberculosis and illustrate TLR collaboration in host resistance to a major human pathogen.

scholarly journals Characterization of Phosphopantetheinyl Hydrolase from Mycobacterium tuberculosis

2021 ◽  
Author(s):  
Shilpika Pandey ◽  
Amrita Singh ◽  
Guangli Yang ◽  
Felipe B. d’Andrea ◽  
Xiuju Jiang ◽  
...  
Keyword(s):  
Infectious Disease ◽  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Posttranslational Modification ◽  
Content Type ◽  
Protein Encoding ◽  
And Function ◽  
Encoding Genes

Tuberculosis (TB), caused by Mycobacterium tuberculosis , was the leading cause of death from an infectious disease before COVID, yet the in vivo essentiality and function of many of the protein-encoding genes expressed by M. tuberculosis are not known. We biochemically characterize M. tuberculosis ’s phosphopantetheinyl hydrolase, PptH, a protein unique to mycobacteria that removes an essential posttranslational modification on proteins involved in synthesis of lipids important for the bacterium’s cell wall and virulence.

scholarly journals Inhibition of Mycobacterium tuberculosis Glutamine Synthetase as a Novel Antibiotic Strategy against Tuberculosis: Demonstration of Efficacy In Vivo

2003 ◽  
Vol 71 (1) ◽  
pp. 456-464 ◽  
Author(s):  
Günter Harth ◽  
Marcus A. Horwitz
Keyword(s):  
Weight Loss ◽  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Glutamine Synthetase ◽  
Secretory Proteins ◽  
Cell Wall Biosynthesis ◽  
Conventional Antibiotics ◽  
Guinea Pig Model ◽  
Highly Virulent

ABSTRACT Tuberculosis remains one of humankind's greatest killers, and new therapeutic strategies are needed to combat the causative agent, Mycobacterium tuberculosis, which is rapidly developing resistance to conventional antibiotics. Using the highly demanding guinea pig model of pulmonary tuberculosis, we have investigated the feasibility of inhibiting M. tuberculosis glutamine synthetase (GS), an enzyme that plays a key role in both nitrogen metabolism and cell wall biosynthesis, as a novel antibiotic strategy. In guinea pigs challenged by aerosol with the highly virulent Erdman strain of M. tuberculosis, the GS inhibitor l-methionine-SR-sulfoximine (MSO) protected the animals against weight loss, a hallmark of tuberculosis, and against the growth of M. tuberculosis in the lungs and spleen; MSO reduced the CFU of M. tuberculosis at 10 weeks after challenge by ∼0.7 log unit compared with that in control animals. MSO acted synergistically with isoniazid in protecting animals against weight loss and bacterial growth, reducing the CFU in the lungs and spleen by ∼1.5 log units below the level seen with isoniazid alone. In the presence of ascorbate, which allows treatment with a higher dose, MSO was highly efficacious, reducing the CFU in the lungs and spleen by 2.5 log units compared with that in control animals. This study demonstrates that inhibition of M. tuberculosis GS is a feasible therapeutic strategy against this pathogen and supports the concept that M. tuberculosis enzymes involved in cell wall biosynthesis, including major secretory proteins, have potential as antibiotic targets.

scholarly journals De novo synthesized polyunsaturated fatty acids operate as both host immunomodulators and nutrients for Mycobacterium tuberculosis

2021 ◽  
Author(s):  
Thomas Laval ◽  
Laura Pedró-Cos ◽  
Wladimir Malaga ◽  
Laure Guenin-Macé ◽  
Alexandre Pawlik ◽  
...  
Keyword(s):  
Fatty Acids ◽  
Mycobacterium Tuberculosis ◽  
Immune Responses ◽  
Biosynthetic Pathway ◽  
De Novo ◽  
Axenic Culture ◽  
Pufa Biosynthesis ◽  
Successful Control

Successful control of Mycobacterium tuberculosis (Mtb) infection by macrophages relies on immunometabolic reprogramming, where the role of fatty acids (FAs) remains poorly understood. Recent studies unraveled Mtb's capacity to acquire saturated and monounsaturated FAs via the Mce1 importer. However, upon activation macrophages produce polyunsaturated FAs (PUFAs), mammal-specific FAs mediating the generation of key immunomodulatory eicosanoids. Here, we asked whether PUFA biosynthesis is modulated in Mtb-infected macrophages and benefits host or pathogen. Quantitative lipidomics revealed that Mtb infection activates the early PUFA biosynthetic pathway for production of eicosanoids. While PUFA synthesis blockade significantly impaired the inflammatory and antimicrobial responses of infected macrophages, it had no effect on Mtb growth in vivo. Using a click-chemistry approach, we found that Mtb efficiently imports PUFAs of the w6 subset via Mce1 in axenic culture, including the eicosanoid precursor arachidonic acid (AA). Notably, Mtb preferentially internalized AA over all other FAs in infected macrophages, but AA import by intracellular Mtb was largely independent from Mce1 and correlated with elevated AA levels within macrophages. Together, these findings reveal PUFAs as novel FA substrates for Mtb. They suggest that Mtb's import of infection-induced PUFAs may counteract their stimulatory effect on anti-mycobacterial immune responses.

scholarly journals Unique C-terminal extension and interactome of Mycobacterium tuberculosis GlmU impacts its in vivo function and the survival of the pathogen

2021 ◽  
Author(s):  
Meetu Kumar Agarwal ◽  
Vijay Kumar Soni ◽  
Suresh Kumar ◽  
Biplab Singha ◽  
Vinay Kumar Nandicoori
Keyword(s):  
Cell Wall ◽  
Mycobacterium Tuberculosis ◽  
Mycobacterium Smegmatis ◽  
Biological Function ◽  
Deletion Mutants ◽  
Bifunctional Enzyme ◽  
Uridine Diphosphate ◽  
Carboxy Terminal ◽  
Wall Components

N-acetyl glucosamine-1-phosphate uridyltransferase (GlmU) is a bifunctional enzyme involved in the biosynthesis of Uridine diphosphate N-acetylglucosamine (UDP-GlcNAc). UDP-GlcNAc is a critical precursor for the synthesis of peptidoglycan and other cell wall components. The absence of a homolog in eukaryotes makes GlmU an attractive target for therapeutic intervention. Mycobacterium tuberculosis GlmU (GlmUMt) has features, such as a C-terminal extension, that are not present in GlmU orthologs from other bacteria. Here, we set out to determine the uniqueness of GlmUMt by performing in vivo complementation experiments using RvDglmU mutant. We find that any deletion of the carboxy-terminal extension region of GlmUMt abolishes its ability to complement the function of GlmUMt.  Results show orthologs of GlmU, including its closest ortholog, from Mycobacterium smegmatis, cannot complement the function of GlmUMt. Furthermore, the co-expression of GlmUMt domain deletion mutants with either acetyl or uridyltransferase activities failed to rescue the function. However, co-expression of GlmUMt point mutants with either acetyl or uridyltransferase activities successfully restored the biological function of GlmUMt, likely due to the formation of heterotrimers. Based on the interactome experiments, we speculate that GlmUMt participates in unique interactions essential for its in vivo function.

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