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Allué-Guardia A, Garcia-Vilanova A, Schami AM, Olmo-Fontánez AM, Hicks A, Peters J, Maselli DJ, Wewers MD, Wang Y, Torrelles JB. Exposure of Mycobacterium tuberculosis to human alveolar lining fluid shows temporal and strain-specific adaptation to the lung environment. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.09.27.559381. [PMID: 37808780 PMCID: PMC10557635 DOI: 10.1101/2023.09.27.559381] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/10/2023]
Abstract
Upon infection, Mycobacterium tuberculosis ( M.tb ) reaches the alveolar space and comes in close contact with human alveolar lining fluid (ALF) for an uncertain period of time prior to its encounter with alveolar cells. We showed that homeostatic ALF hydrolytic enzymes modify the M.tb cell envelope, driving M.tb -host cell interactions. Still, the contribution of ALF during M.tb infection is poorly understood. Here, we exposed 4 M.tb strains with different levels of virulence, transmissibility, and drug resistance (DR) to physiological concentrations of human ALF for 15-min and 12-h, and performed RNA sequencing. Gene expression analysis showed a temporal and strain-specific adaptation to human ALF. Differential expression (DE) of ALF-exposed vs. unexposed M.tb revealed a total of 397 DE genes associated with lipid metabolism, cell envelope and processes, intermediary metabolism and respiration, and regulatory proteins, among others. Most DE genes were detected at 12-h post-ALF exposure, with DR- M.tb strain W-7642 having the highest number of DE genes. Interestingly, genes from the KstR2 regulon, which controls the degradation of cholesterol C and D rings, were significantly upregulated in all strains post-ALF exposure. These results indicate that M.tb -ALF contact drives initial metabolic and physiologic changes in M.tb , with potential implications in infection outcome. IMPORTANCE Tuberculosis, caused by airborne pathogen Mycobacterium tuberculosis ( M.tb ), is one of the leading causes of mortality worldwide. Upon infection, M.tb reaches the alveoli and gets in contact with human alveolar lining fluid (ALF), where ALF hydrolases modify the M.tb cell envelope driving subsequent M.tb -host cell interactions. Still, the contributions of ALF during infection are poorly understood. We exposed 4 M.tb strains to ALF for 15-min and 12-h and performed RNA sequencing, demonstrating a temporal and strain-specific adaptation of M.tb to ALF. Interestingly, genes associated with cholesterol degradation were highly upregulated in all strains. This study shows for the first time that ALF drives global metabolic changes in M.tb during the initial stages of the infection, with potential implications in disease outcome. Biologically relevant networks and common and strain-specific bacterial determinants derived from this study could be further investigated as potential therapeutic candidates.
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Badhwar P, Ahmad I, Sharma R, Taneja B. Structural investigation and gene deletion studies of mycobacterial oligoribonuclease reveal modulation of c-di-GMP-mediated phenotypes. Int J Biol Macromol 2022; 223:161-172. [PMID: 36356862 DOI: 10.1016/j.ijbiomac.2022.11.029] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2022] [Revised: 10/26/2022] [Accepted: 11/01/2022] [Indexed: 11/09/2022]
Abstract
Cyclic-di-GMP (c-di-GMP) is a ubiquitous bacterial second messenger required for normal physiology as well as survival under hypoxic and reductive stress conditions of mycobacterial cells. Complete degradation of c-di-GMP is necessary for signal termination and maintaining its homeostasis inside the cells. Homeostasis of c-di-GMP in mycobacteria is brought about by the bifunctional diguanylate cyclase (DGC) that synthesizes c-di-GMP from two molecules of GTP and also catalyses the asymmetric cleavage of c-di-GMP to linear pGpG through its phosphodiesterase activity. However, the mycobacterial enzyme for the last step of degradation from pGpG to GMP has not been characterized thus far. Here, we present the identification of oligoribonuclease (Orn) as the most likely phosphodiesterase to degrade pGpG to GMP through AlphaFold-empowered structural homology that exhibited in vitro phosphodiesterase activity on pGpG substrates. In order to understand the physiological role of Orn in mycobacteria, we created a deletion mutant of orn in M. smegmatis and analysed the phenotypes that are associated with c-di-GMP signaling. We find that orn plays important roles in vivo and is required not only for proper growth of M. smegmatis in normal and stress conditions but also for biofilm formation.
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Affiliation(s)
- Pooja Badhwar
- CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi 110025, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Iftekhar Ahmad
- CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi 110025, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Rakesh Sharma
- CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi 110025, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India
| | - Bhupesh Taneja
- CSIR-Institute of Genomics and Integrative Biology (CSIR-IGIB), New Delhi 110025, India; Academy of Scientific and Innovative Research (AcSIR), Ghaziabad 201002, India.
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Thomson M, Liu Y, Nunta K, Cheyne A, Fernandes N, Williams R, Garza-Garcia A, Larrouy-Maumus G. Expression of a novel mycobacterial phosphodiesterase successfully lowers cAMP levels resulting in reduced tolerance to cell wall-targeting antimicrobials. J Biol Chem 2022; 298:102151. [PMID: 35718063 PMCID: PMC9293780 DOI: 10.1016/j.jbc.2022.102151] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2022] [Revised: 06/09/2022] [Accepted: 06/10/2022] [Indexed: 02/09/2023] Open
Abstract
cAMP and antimicrobial susceptibility in mycobacteriaAntimicrobial tolerance, the ability to survive exposure to antimicrobials via transient nonspecific means, promotes the development of antimicrobial resistance (AMR). The study of the molecular mechanisms that result in antimicrobial tolerance is therefore essential for the understanding of AMR. In gram-negative bacteria, the second messenger molecule 3'',5''-cAMP has been previously shown to be involved in AMR. In mycobacteria, however, the role of cAMP in antimicrobial tolerance has been difficult to probe due to its particular complexity. In order to address this difficulty, here, through unbiased biochemical approaches consisting in the fractionation of clear protein lysate from a mycobacterial strain deleted for the known cAMP phosphodiesterase (Rv0805c) combined with mass spectrometry techniques, we identified a novel cyclic nucleotide-degrading phosphodiesterase enzyme (Rv1339) and developed a system to significantly decrease intracellular cAMP levels through plasmid expression of Rv1339 using the constitutive expression system, pVV16. In Mycobacterium smegmatis mc2155, we demonstrate that recombinant expression of Rv1339 reduced cAMP levels threefold and resulted in altered gene expression, impaired bioenergetics, and a disruption in peptidoglycan biosynthesis leading to decreased tolerance to antimicrobials that target cell wall synthesis such as ethambutol, D-cycloserine, and vancomycin. This work increases our understanding of the role of cAMP in mycobacterial antimicrobial tolerance, and our observations suggest that nucleotide signaling may represent a new target for the development of antimicrobial therapies.
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Affiliation(s)
- Michael Thomson
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, United Kingdom
| | - Yi Liu
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, United Kingdom
| | - Kanokkan Nunta
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, United Kingdom
| | - Ashleigh Cheyne
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, United Kingdom
| | - Nadia Fernandes
- Imperial BRC Genomics Facility, Imperial College London, London, United Kingdom
| | - Richard Williams
- Imperial BRC Genomics Facility, Imperial College London, London, United Kingdom
| | | | - Gerald Larrouy-Maumus
- MRC Centre for Molecular Bacteriology and Infection, Department of Life Sciences, Faculty of Natural Sciences, Imperial College London, London, United Kingdom,For correspondence: Gerald Larrouy-Maumus
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Ciechonska M, Sturrock M, Grob A, Larrouy-Maumus G, Shahrezaei V, Isalan M. Emergent expression of fitness-conferring genes by phenotypic selection. PNAS NEXUS 2022; 1:pgac069. [PMID: 36741458 PMCID: PMC9896880 DOI: 10.1093/pnasnexus/pgac069] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 10/20/2021] [Accepted: 05/23/2022] [Indexed: 02/07/2023]
Abstract
Genotypic and phenotypic adaptation is the consequence of ongoing natural selection in populations and is key to predicting and preventing drug resistance. Whereas classic antibiotic persistence is all-or-nothing, here we demonstrate that an antibiotic resistance gene displays linear dose-responsive selection for increased expression in proportion to rising antibiotic concentration in growing Escherichia coli populations. Furthermore, we report the potentially wide-spread nature of this form of emergent gene expression (EGE) by instantaneous phenotypic selection process under bactericidal and bacteriostatic antibiotic treatment, as well as an amino acid synthesis pathway enzyme under a range of auxotrophic conditions. We propose an analogy to Ohm's law in electricity (V = IR), where selection pressure acts similarly to voltage (V), gene expression to current (I), and resistance (R) to cellular machinery constraints and costs. Lastly, mathematical modeling using agent-based models of stochastic gene expression in growing populations and Bayesian model selection reveal that the EGE mechanism requires variability in gene expression within an isogenic population, and a cellular "memory" from positive feedbacks between growth and expression of any fitness-conferring gene. Finally, we discuss the connection of the observed phenomenon to a previously described general fluctuation-response relationship in biology.
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Affiliation(s)
| | | | - Alice Grob
- Department of Life Sciences, Imperial College London, London SW7 2AZ, UK
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Dawson CC, Cummings JE, Starkey JM, Slayden RA. Discovery of a novel type IIb RelBE toxin-antitoxin system in Mycobacterium tuberculosis defined by co-regulation with an antisense RNA. Mol Microbiol 2022; 117:1419-1433. [PMID: 35526138 PMCID: PMC9325379 DOI: 10.1111/mmi.14917] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/29/2020] [Revised: 04/30/2022] [Accepted: 05/05/2022] [Indexed: 11/29/2022]
Abstract
Toxin‐antitoxin loci regulate adaptive responses to stresses associated with the host environment and drug exposure. Phylogenomic studies have shown that Mycobacterium tuberculosis encodes a naturally expanded type II toxin‐antitoxin system, including ParDE/RelBE superfamily members. Type II toxins are presumably regulated exclusively through protein–protein interactions with type II antitoxins. However, experimental observations in M. tuberculosis indicated that additional control mechanisms regulate RelBE2 type II loci under host‐associated stress conditions. Herein, we describe for the first time a novel antisense RNA, termed asRelE2, that co‐regulates RelE2 production via targeted processing by the Mtb RNase III, Rnc. We find that convergent expression of this coding‐antisense hybrid TA locus, relBE2‐asrelE2, is controlled in a cAMP‐dependent manner by the essential cAMP receptor protein transcription factor, Crp, in response to the host‐associated stresses of low pH and nutrient limitation. Ex vivo survival studies with relE2 and asrelE2 knockout strains showed that RelE2 contributes to Mtb survival in activated macrophages and low pH to nutrient limitation. To our knowledge, this is the first report of a novel tripartite type IIb TA loci and antisense post‐transcriptional regulation of a type II TA loci.
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Affiliation(s)
- Clinton C Dawson
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins.,Endolytix Technology, Inc. Beverly, 01915
| | - Jason E Cummings
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins
| | - Julie M Starkey
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins
| | - Richard A Slayden
- Mycobacteria Research Laboratories, Department of Microbiology, Immunology, and Pathology, Colorado State University, Fort Collins
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Ante VM, Farris LC, Saputra EP, Hall AJ, O'Bier NS, Oliva Chávez AS, Marconi RT, Lybecker MC, Hyde JA. The Borrelia burgdorferi Adenylate Cyclase, CyaB, Is Important for Virulence Factor Production and Mammalian Infection. Front Microbiol 2021; 12:676192. [PMID: 34113333 PMCID: PMC8186283 DOI: 10.3389/fmicb.2021.676192] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/04/2021] [Accepted: 04/16/2021] [Indexed: 12/21/2022] Open
Abstract
Borrelia burgdorferi, the causative agent of Lyme disease, traverses through vastly distinct environments between the tick vector and the multiple phases of the mammalian infection that requires genetic adaptation for the progression of pathogenesis. Borrelial gene expression is highly responsive to changes in specific environmental signals that initiate the RpoS regulon for mammalian adaptation, but the mechanism(s) for direct detection of environmental cues has yet to be identified. Secondary messenger cyclic adenosine monophosphate (cAMP) produced by adenylate cyclase is responsive to environmental signals, such as carbon source and pH, in many bacterial pathogens to promote virulence by altering gene regulation. B. burgdorferi encodes a single non-toxin class IV adenylate cyclase (bb0723, cyaB). This study investigates cyaB expression along with its influence on borrelial virulence regulation and mammalian infectivity. Expression of cyaB was specifically induced with co-incubation of mammalian host cells that was not observed with cultivated tick cells suggesting that cyaB expression is influenced by cellular factor(s) unique to mammalian cell lines. The 3′ end of cyaB also encodes a small RNA, SR0623, in the same orientation that overlaps with bb0722. The differential processing of cyaB and SR0623 transcripts may alter the ability to influence function in the form of virulence determinant regulation and infectivity. Two independent cyaB deletion B31 strains were generated in 5A4-NP1 and ML23 backgrounds and complemented with the cyaB ORF alone that truncates SR0623, cyaB with intact SR0623, or cyaB with a mutagenized full-length SR0623 to evaluate the influence on transcriptional and posttranscriptional regulation of borrelial virulence factors and infectivity. In the absence of cyaB, the expression and production of ospC was significantly reduced, while the protein levels for BosR and DbpA were substantially lower than parental strains. Infectivity studies with both independent cyaB mutants demonstrated an attenuated phenotype with reduced colonization of tissues during early disseminated infection. This work suggests that B. burgdorferi utilizes cyaB and potentially cAMP as a regulatory pathway to modulate borrelial gene expression and protein production to promote borrelial virulence and dissemination in the mammalian host.
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Affiliation(s)
- Vanessa M Ante
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, Bryan, TX, United States
| | - Lauren C Farris
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, Bryan, TX, United States
| | - Elizabeth P Saputra
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, Bryan, TX, United States
| | - Allie J Hall
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, CO, United States
| | - Nathaniel S O'Bier
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA, United States
| | - Adela S Oliva Chávez
- Department of Entomology, Texas A&M University, College Station, TX, United States
| | - Richard T Marconi
- Department of Microbiology and Immunology, Virginia Commonwealth University Medical Center, Richmond, VA, United States
| | - Meghan C Lybecker
- Department of Biology, University of Colorado at Colorado Springs, Colorado Springs, CO, United States
| | - Jenny A Hyde
- Department of Microbial Pathogenesis and Immunology, Texas A&M University Health Science Center, Bryan, TX, United States
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