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Derunets AS, Selimzyanova AI, Rykov SV, Kuznetsov AE, Berezina OV. Strategies to enhance stress tolerance in lactic acid bacteria across diverse stress conditions. World J Microbiol Biotechnol 2024; 40:126. [PMID: 38446232 DOI: 10.1007/s11274-024-03905-3] [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: 12/01/2023] [Accepted: 01/21/2024] [Indexed: 03/07/2024]
Abstract
Lactic acid bacteria (LAB) hold significant importance in diverse fields, including food technology, industrial biotechnology, and medicine. As basic components of starter cultures, probiotics, immunomodulators, and live vaccines, LAB cells resist a variety of stressors, including temperature fluctuations, osmotic and pH shocks, exposure to oxidants and ultraviolet radiation, substrate deprivation, mechanical damage, and more. To stay alive in these adversities, LAB employ a wide range of stress response strategies supported by various mechanisms, for example rearrangement of metabolism, expression of specialized biomolecules (e.g., chaperones and antioxidants), exopolysaccharide synthesis, and complex repair and regulatory systems. LAB can coordinate responses to various stressors using global regulators. In this review, we summarize current knowledge about stress response strategies used by LAB and consider mechanisms of response to specific stressful factors, supported by illustrative examples. In addition, we discuss technical approaches to increase the stress resistance of LAB, including pre-adaptation, genetic modification of strains, and adjustment of cultivation conditions. A critical analysis of the recent findings in this field augments comprehension of stress tolerance mechanisms in LAB, paving the way for prospective research directions with implications in fundamental and practical areas.
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Affiliation(s)
- A S Derunets
- National Research Center Kurchatov Institute, Moscow, Russia.
| | | | - S V Rykov
- National Research Center Kurchatov Institute, Moscow, Russia
| | - A E Kuznetsov
- D. Mendeleev University of Chemical Technology of Russia, Moscow, Russia
| | - O V Berezina
- National Research Center Kurchatov Institute, Moscow, Russia
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2
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Graham CI, MacMartin TL, de Kievit TR, Brassinga AKC. Molecular regulation of virulence in Legionella pneumophila. Mol Microbiol 2024; 121:167-195. [PMID: 37908155 DOI: 10.1111/mmi.15172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Revised: 09/15/2023] [Accepted: 09/17/2023] [Indexed: 11/02/2023]
Abstract
Legionella pneumophila is a gram-negative bacteria found in natural and anthropogenic aquatic environments such as evaporative cooling towers, where it reproduces as an intracellular parasite of cohabiting protozoa. If L. pneumophila is aerosolized and inhaled by a susceptible person, bacteria may colonize their alveolar macrophages causing the opportunistic pneumonia Legionnaires' disease. L. pneumophila utilizes an elaborate regulatory network to control virulence processes such as the Dot/Icm Type IV secretion system and effector repertoire, responding to changing nutritional cues as their host becomes depleted. The bacteria subsequently differentiate to a transmissive state that can survive in the environment until a replacement host is encountered and colonized. In this review, we discuss the lifecycle of L. pneumophila and the molecular regulatory network that senses nutritional depletion via the stringent response, a link to stationary phase-like metabolic changes via alternative sigma factors, and two-component systems that are homologous to stress sensors in other pathogens, to regulate differentiation between the intracellular replicative phase and more transmissible states. Together, we highlight how this prototypic intracellular pathogen offers enormous potential in understanding how molecular mechanisms enable intracellular parasitism and pathogenicity.
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Affiliation(s)
- Christopher I Graham
- Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Teassa L MacMartin
- Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Teresa R de Kievit
- Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada
| | - Ann Karen C Brassinga
- Department of Microbiology, Faculty of Science, University of Manitoba, Winnipeg, Manitoba, Canada
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3
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Weaver JW, Proshkin S, Duan W, Epshtein V, Gowder M, Bharati BK, Afanaseva E, Mironov A, Serganov A, Nudler E. Control of transcription elongation and DNA repair by alarmone ppGpp. Nat Struct Mol Biol 2023; 30:600-607. [PMID: 36997761 PMCID: PMC10191844 DOI: 10.1038/s41594-023-00948-2] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2021] [Accepted: 02/27/2023] [Indexed: 04/01/2023]
Abstract
Second messenger (p)ppGpp (collectively guanosine tetraphosphate and guanosine pentaphosphate) mediates bacterial adaptation to nutritional stress by modulating transcription initiation. More recently, ppGpp has been implicated in coupling transcription and DNA repair; however, the mechanism of ppGpp engagement remained elusive. Here we present structural, biochemical and genetic evidence that ppGpp controls Escherichia coli RNA polymerase (RNAP) during elongation via a specific site that is nonfunctional during initiation. Structure-guided mutagenesis renders the elongation (but not initiation) complex unresponsive to ppGpp and increases bacterial sensitivity to genotoxic agents and ultraviolet radiation. Thus, ppGpp binds RNAP at sites with distinct functions in initiation and elongation, with the latter being important for promoting DNA repair. Our data provide insights on the molecular mechanism of ppGpp-mediated adaptation during stress, and further highlight the intricate relationships between genome stability, stress responses and transcription.
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Affiliation(s)
- Jacob W Weaver
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Sergey Proshkin
- Engelhardt Institute of Molecular Biology, Russian Academy of Science, Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Moscow, Russia
| | - Wenqian Duan
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Vitaly Epshtein
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
| | - Manjunath Gowder
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
- Howard Hughes Medical Institute, New York University School of Medicine, New York, NY, USA
| | - Binod K Bharati
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA
- Howard Hughes Medical Institute, New York University School of Medicine, New York, NY, USA
| | - Elena Afanaseva
- Engelhardt Institute of Molecular Biology, Russian Academy of Science, Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Moscow, Russia
| | - Alexander Mironov
- Engelhardt Institute of Molecular Biology, Russian Academy of Science, Center for Precision Genome Editing and Genetic Technologies for Biomedicine, Moscow, Russia
| | - Alexander Serganov
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA.
| | - Evgeny Nudler
- Department of Biochemistry and Molecular Pharmacology, New York University School of Medicine, New York, NY, USA.
- Howard Hughes Medical Institute, New York University School of Medicine, New York, NY, USA.
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4
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Protein-Ligand Interactions in Scarcity: The Stringent Response from Bacteria to Metazoa, and the Unanswered Questions. Int J Mol Sci 2023; 24:ijms24043999. [PMID: 36835415 PMCID: PMC9965611 DOI: 10.3390/ijms24043999] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2022] [Revised: 02/06/2023] [Accepted: 02/14/2023] [Indexed: 02/18/2023] Open
Abstract
The stringent response, originally identified in Escherichia coli as a signal that leads to reprogramming of gene expression under starvation or nutrient deprivation, is now recognized as ubiquitous in all bacteria, and also as part of a broader survival strategy in diverse, other stress conditions. Much of our insight into this phenomenon derives from the role of hyperphosphorylated guanosine derivatives (pppGpp, ppGpp, pGpp; guanosine penta-, tetra- and tri-phosphate, respectively) that are synthesized on starvation cues and act as messengers or alarmones. These molecules, collectively referred to here as (p)ppGpp, orchestrate a complex network of biochemical steps that eventually lead to the repression of stable RNA synthesis, growth, and cell division, while promoting amino acid biosynthesis, survival, persistence, and virulence. In this analytical review, we summarize the mechanism of the major signaling pathways in the stringent response, consisting of the synthesis of the (p)ppGpp, their interaction with RNA polymerase, and diverse factors of macromolecular biosynthesis, leading to differential inhibition and activation of specific promoters. We also briefly touch upon the recently reported stringent-like response in a few eukaryotes, which is a very disparate mechanism involving MESH1 (Metazoan SpoT Homolog 1), a cytosolic NADPH phosphatase. Lastly, using ppGpp as an example, we speculate on possible pathways of simultaneous evolution of alarmones and their multiple targets.
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Wang MF, Wang J, Wang XB, Zhu XC, Wang YP, Wang W. Effect of SPoT-mediated Stringent Response on Biofilm Formation, Stress Resistance and Quorum Sensing in Pseudomonas protegens SN15-2. APPL BIOCHEM MICRO+ 2022. [DOI: 10.1134/s0003683822040172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
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Bisiak F, Chrenková A, Zhang SD, Pedersen JN, Otzen DE, Zhang YE, Brodersen DE. Structural variations between small alarmone hydrolase dimers support different modes of regulation of the stringent response. J Biol Chem 2022; 298:102142. [PMID: 35714769 PMCID: PMC9293644 DOI: 10.1016/j.jbc.2022.102142] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2022] [Revised: 06/10/2022] [Accepted: 06/11/2022] [Indexed: 11/04/2022] Open
Abstract
The bacterial stringent response involves wide-ranging metabolic reprogramming aimed at increasing long-term survivability during stress conditions. One of the hallmarks of the stringent response is the production of a set of modified nucleotides, known as alarmones, which affect a multitude of cellular pathways in diverse ways. Production and degradation of these molecules depend on the activity of enzymes from the RelA/SpoT homologous family, which come in both bifunctional (containing domains to both synthesize and hydrolyze alarmones) and monofunctional (consisting of only synthetase or hydrolase domain) variants, of which the structure, activity, and regulation of the bifunctional RelA/SpoT homologs have been studied most intensely. Despite playing an important role in guanosine nucleotide homeostasis in particular, mechanisms of regulation of the small alarmone hydrolases (SAHs) are still rather unclear. Here, we present crystal structures of SAH enzymes from Corynebacterium glutamicum (RelHCg) and Leptospira levettii (RelHLl) and show that while being highly similar, structural differences in substrate access and dimer conformations might be important for regulating their activity. We propose that a varied dimer form is a general property of the SAH family, based on current structural information as well as prediction models for this class of enzymes. Finally, subtle structural variations between monofunctional and bifunctional enzymes point to how these different classes of enzymes are regulated.
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Affiliation(s)
- Francesco Bisiak
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Adriana Chrenková
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark
| | - Sheng-Da Zhang
- Department of Biotechnology and Biomedicine, Technical University of Denmark, Kgs. Lyngby, Denmark
| | - Jannik N Pedersen
- Interdisciplinary Nanoscience Centre (iNano), Aarhus University, Aarhus C, Denmark
| | - Daniel E Otzen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark; Interdisciplinary Nanoscience Centre (iNano), Aarhus University, Aarhus C, Denmark
| | - Yong E Zhang
- Department of Biology, University of Copenhagen, København N, Denmark
| | - Ditlev E Brodersen
- Department of Molecular Biology and Genetics, Aarhus University, Aarhus C, Denmark.
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Diez S, Hydorn M, Whalen A, Dworkin J. Crosstalk between guanosine nucleotides regulates cellular heterogeneity in protein synthesis during nutrient limitation. PLoS Genet 2022; 18:e1009957. [PMID: 35594298 PMCID: PMC9173625 DOI: 10.1371/journal.pgen.1009957] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/19/2021] [Revised: 06/07/2022] [Accepted: 04/24/2022] [Indexed: 11/26/2022] Open
Abstract
Phenotypic heterogeneity of microbial populations can facilitate survival in dynamic environments by generating sub-populations of cells that may have differential fitness in a future environment. Bacillus subtilis cultures experiencing nutrient limitation contain distinct sub-populations of cells exhibiting either comparatively high or low protein synthesis activity. This heterogeneity requires the production of phosphorylated guanosine nucleotides (pp)pGpp by three synthases: SasA, SasB, and RelA. Here we show that these enzymes differentially affect this bimodality: RelA and SasB are necessary to generate the sub-population of cells exhibiting low protein synthesis whereas SasA is necessary to generate cells exhibiting comparatively higher protein synthesis. Previously, it was reported that a RelA product allosterically activates SasB and we find that a SasA product competitively inhibits this activation. Finally, we provide in vivo evidence that this antagonistic interaction mediates the observed heterogeneity in protein synthesis. This work therefore identifies the mechanism underlying phenotypic heterogeneity in protein synthesis. Upon encountering conditions unfavorable to growth such as nutrient limitation, bacteria enter a quiescent phenotype that is mediated by group of guanosine nucleotides collectively known as (pp)pGpp. These nucleotides direct the down-regulation of energy intensive processes and are essential for a striking heterogeneity in protein synthesis observed during exit from rapid growth. Here, we show that a network of (pp)pGpp synthases is responsible for this heterogeneity and describe a mechanism that allows for the integration of multiple signals into the decision to down regulate the most energy intensive process in a cell.
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Affiliation(s)
- Simon Diez
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Molly Hydorn
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Abigail Whalen
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
| | - Jonathan Dworkin
- Department of Microbiology and Immunology, College of Physicians and Surgeons, Columbia University, New York, New York, United States of America
- * E-mail:
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8
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How to save a bacterial ribosome in times of stress. Semin Cell Dev Biol 2022; 136:3-12. [PMID: 35331628 DOI: 10.1016/j.semcdb.2022.03.015] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/26/2022] [Revised: 03/01/2022] [Accepted: 03/11/2022] [Indexed: 11/21/2022]
Abstract
Biogenesis of ribosomes is one of the most cost- and resource-intensive processes in all living cells. In bacteria, ribosome biogenesis is rate-limiting for growth and must be tightly coordinated to yield maximum fitness of the cells. Since bacteria are continuously facing environmental changes and stress conditions, they have developed sophisticated systems to sense and regulate their nutritional status. Amino acid starvation leads to the synthesis and accumulation of the nucleotide-based second messengers ppGpp and pppGpp [(p)ppGpp], which in turn function as central players of a pleiotropic metabolic adaptation mechanism named the stringent response. Here, we review our current knowledge on the multiple roles of (p)ppGpp in the stress-related modulation of the prokaryotic protein biosynthesis machinery with the ribosome as its core constituent. The alarmones ppGpp/pppGpp act as competitors of their GDP/GTP counterparts, to affect a multitude of ribosome-associated P-loop GTPases involved in the translation cycle, ribosome biogenesis and hibernation. A similar mode of inhibition has been found for the GTPases of the proteins involved in the SRP-dependent membrane-targeting machinery present in the periphery of the ribosome. In this sense, during stringent conditions, binding of (p)ppGpp restricts the membrane insertion and secretion of proteins. Altogether, we highlight the enormously resource-intensive stages of ribosome biogenesis as a critical regulatory hub of the stringent response that ultimately tunes the protein synthesis capacity and consequently the survival of the cell.
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9
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Kho ZY, Azad MAK, Han ML, Zhu Y, Huang C, Schittenhelm RB, Naderer T, Velkov T, Selkrig J, Zhou Q(T, Li J. Correlative proteomics identify the key roles of stress tolerance strategies in Acinetobacter baumannii in response to polymyxin and human macrophages. PLoS Pathog 2022; 18:e1010308. [PMID: 35231068 PMCID: PMC8887720 DOI: 10.1371/journal.ppat.1010308] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2021] [Accepted: 01/26/2022] [Indexed: 11/19/2022] Open
Abstract
The opportunistic pathogen Acinetobacter baumannii possesses stress tolerance strategies against host innate immunity and antibiotic killing. However, how the host-pathogen-antibiotic interaction affects the overall molecular regulation of bacterial pathogenesis and host response remains unexplored. Here, we simultaneously investigate proteomic changes in A. baumannii and macrophages following infection in the absence or presence of the polymyxins. We discover that macrophages and polymyxins exhibit complementary effects to disarm several stress tolerance and survival strategies in A. baumannii, including oxidative stress resistance, copper tolerance, bacterial iron acquisition and stringent response regulation systems. Using the spoT mutant strains, we demonstrate that bacterial cells with defects in stringent response exhibit enhanced susceptibility to polymyxin killing and reduced survival in infected mice, compared to the wild-type strain. Together, our findings highlight that better understanding of host-pathogen-antibiotic interplay is critical for optimization of antibiotic use in patients and the discovery of new antimicrobial strategy to tackle multidrug-resistant bacterial infections.
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Affiliation(s)
- Zhi Ying Kho
- Biomedicine Discovery Institute, Infection Program and Department of Microbiology, Monash University, Clayton, Victoria, Australia
| | - Mohammad A. K. Azad
- Biomedicine Discovery Institute, Infection Program and Department of Microbiology, Monash University, Clayton, Victoria, Australia
| | - Mei-Ling Han
- Biomedicine Discovery Institute, Infection Program and Department of Microbiology, Monash University, Clayton, Victoria, Australia
| | - Yan Zhu
- Biomedicine Discovery Institute, Infection Program and Department of Microbiology, Monash University, Clayton, Victoria, Australia
| | - Cheng Huang
- Monash Proteomics & Metabolomics Facility, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
| | - Ralf B. Schittenhelm
- Monash Proteomics & Metabolomics Facility, Monash Biomedicine Discovery Institute, Monash University, Clayton, Victoria, Australia
| | - Thomas Naderer
- Biomedicine Discovery Institute, Infection Program, Department of Biochemistry and Molecular Biology, Monash University, Clayton, Victoria, Australia
| | - Tony Velkov
- Department of Pharmacology and Therapeutics, School of Biomedical Sciences, Faculty of Medicine, Dentistry and Health Sciences, University of Melbourne, Parkville, Victoria, Australia
| | - Joel Selkrig
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Qi (Tony) Zhou
- Department of Industrial and Physical Pharmacy, Purdue University, West Lafayette, Indiana, United States of America
| | - Jian Li
- Biomedicine Discovery Institute, Infection Program and Department of Microbiology, Monash University, Clayton, Victoria, Australia
- * E-mail:
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10
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Syal K, Rs N, Reddy MVNJ. The extended (p)ppGpp family: New dimensions in Stress response. CURRENT RESEARCH IN MICROBIAL SCIENCES 2021; 2:100052. [PMID: 34841343 PMCID: PMC8610335 DOI: 10.1016/j.crmicr.2021.100052] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2021] [Revised: 07/21/2021] [Accepted: 07/25/2021] [Indexed: 11/30/2022] Open
Abstract
Second messenger (p)ppGpp mediated stress response plays a crucial role in bacterial persistence and multiple drug resistance. In E. coli, (p)ppGpp binds to RNA polymerase and upregulates the transcription of genes essential for stress response while concurrently downregulating the expression of genes critical for growth and metabolism. Recently, the family of alarmone molecules has expanded to pppGpp, ppGpp, pGpp & (pp)pApp as distinct members. These molecules may help in fine-tuning stress responses in different hostile conditions. Do all of these molecules bind to RNA polymerase? Do they compete with each other or complement each other's functions is still not clear. Earlier, others and we have synthesized artificial analogs of (p)ppGpp that inhibited (p)ppGpp synthesis and long-term survival in M. smegmatis and in B. subtilis suggesting that analogs could compete with each other. Understanding the interplay of these molecules will allow deciphering novel pathways that can be potentially subjected to the therapeutic intervention. In this article, we have reviewed newly characterized second messengers and discussed their mode of action. We have also documented the progress made to-date in understanding the molecular basis of regulation of transcription by second messenger ppGpp, pppGpp, and pGpp.
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Affiliation(s)
- Kirtimaan Syal
- Department of Biological Sciences, Birla Institute of Technology and Sciences-Pilani, Hyderabad campus, Hyderabad, Telangana, India
| | - Neethu Rs
- Department of Biological Sciences, Birla Institute of Technology and Sciences-Pilani, Hyderabad campus, Hyderabad, Telangana, India
| | - M V N Janardhan Reddy
- Department of Biological Sciences, Birla Institute of Technology and Sciences-Pilani, Hyderabad campus, Hyderabad, Telangana, India
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11
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Wan X, Brynildsen MP. Robustness of nitric oxide detoxification to nitrogen starvation in Escherichia coli requires RelA. Free Radic Biol Med 2021; 176:286-297. [PMID: 34624482 DOI: 10.1016/j.freeradbiomed.2021.10.005] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2021] [Accepted: 10/04/2021] [Indexed: 01/18/2023]
Abstract
Reactive nitrogen species and nutrient deprivation are two elements of the immune response used to eliminate pathogens within phagosomes. Concomitantly, pathogenic bacteria have evolved defense systems to cope with phagosomal stressors, which include enzymes that detoxify nitric oxide (•NO) and respond to nutrient scarcity. A deeper understanding of how those defense systems are deployed under adverse conditions that contain key elements of phagosomes will facilitate targeting of those systems for therapeutic purposes. Here we investigated how Escherichia coli detoxifies •NO in the absence of useable nitrogen, because nitrogen availability is limited in phagosomes due to the removal of nitrogenous compounds (e.g., amino acids). We hypothesized that nitrogen starvation would impair •NO detoxification by E. coli because it depresses translation rates and the main E. coli defense enzyme, Hmp, is synthesized in response to •NO. However, we found that E. coli detoxifies •NO at the same rate regardless of whether useable nitrogen was present. We confirmed that the nitrogen in •NO and its autoxidation products could not be used by E. coli under our experimental conditions, and discovered that •NO eliminated differences in carbon and oxygen consumption between nitrogen-replete and nitrogen-starved cultures. Interestingly, E. coli does not consume measurable extracellular nitrogen during •NO stress despite the need to translate defense enzymes. Further, we found that RelA, which responds to uncharged tRNA, was required to observe the robustness of •NO detoxification to nitrogen starvation. These data demonstrate that E. coli is well poised to detoxify •NO in the absence of useable nitrogen and suggest that the stringent response could be a useful target to potentiate the antibacterial activity of •NO.
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Affiliation(s)
- Xuanqing Wan
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, 08544, USA
| | - Mark P Brynildsen
- Department of Chemical and Biological Engineering, Princeton University, Princeton, NJ, 08544, USA.
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12
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Liu Z, Zhao Y, Huang C, Luo Y. Recent Advances in Silent Gene Cluster Activation in Streptomyces. Front Bioeng Biotechnol 2021; 9:632230. [PMID: 33681170 PMCID: PMC7930741 DOI: 10.3389/fbioe.2021.632230] [Citation(s) in RCA: 42] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2020] [Accepted: 01/25/2021] [Indexed: 11/13/2022] Open
Abstract
Natural products (NPs) are critical sources of drug molecules for decades. About two-thirds of natural antibiotics are produced by Streptomyces. Streptomyces have a large number of secondary metabolite biosynthetic gene clusters (SM-BGCs) that may encode NPs. However, most of these BGCs are silent under standard laboratory conditions. Hence, activation of these silent BGCs is essential to current natural products discovery research. In this review, we described the commonly used strategies for silent BGC activation in Streptomyces from two aspects. One focused on the strategies applied in heterologous host, including methods to clone and reconstruct BGCs along with advances in chassis engineering; the other focused on methods applied in native host which includes engineering of promoters, regulatory factors, and ribosomes. With the metabolic network being elucidated more comprehensively and methods optimized more high-thoroughly, the discovery of NPs will be greatly accelerated.
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Affiliation(s)
- Zhenyu Liu
- Key Laboratory of Systems Bioengineering (Ministry of Education), Frontier Science Center for Synthetic Biology, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Yatong Zhao
- Key Laboratory of Systems Bioengineering (Ministry of Education), Frontier Science Center for Synthetic Biology, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Chaoqun Huang
- Key Laboratory of Systems Bioengineering (Ministry of Education), Frontier Science Center for Synthetic Biology, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China
| | - Yunzi Luo
- Key Laboratory of Systems Bioengineering (Ministry of Education), Frontier Science Center for Synthetic Biology, School of Chemical Engineering and Technology, Tianjin University, Tianjin, China.,Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, China
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13
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relA and spoT Gene Expression is Modulated in Salmonella Grown Under Static Magnetic Field. Curr Microbiol 2021; 78:887-893. [PMID: 33515321 DOI: 10.1007/s00284-021-02346-7] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2020] [Accepted: 01/10/2021] [Indexed: 10/22/2022]
Abstract
Virtually all bacterial species synthesize high levels of (p)ppGpp (guanosine penta- or tetraphosphate), a pleiotropic regulator of the stringent response and other stresses in bacteria. relA and spoT genes are, respectively, involved in synthesis and synthesis/biodegradation of (p)ppGpp. We aimed in this work to evaluate the impact of static magnetic field (SMF) 200 mT exposure on the expression of relA and spoT genes in Salmonella enterica Hadar. Bacteria were exposed to a SMF during 9 h, and RNA extraction was followed by reverse transcriptase polymerase chain reaction (RT-PCR). The relative quantification of mRNA expression levels using the 16S rRNA reference gene did not change during the SMF exposure. However, results showed a significant increase in gene expression for relA after 3 h of exposure (P < 0.05) and after 6 h for spoT (P < 0.05). The differential gene expression of relA and spoT could be considered as a potential stress response to a SMF exposure in Salmonella related to the production/degradation of (p)ppGpp.
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14
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Parker H, Lorenc R, Ruelas Castillo J, Karakousis PC. Mechanisms of Antibiotic Tolerance in Mycobacterium avium Complex: Lessons From Related Mycobacteria. Front Microbiol 2020; 11:573983. [PMID: 33101247 PMCID: PMC7554310 DOI: 10.3389/fmicb.2020.573983] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2020] [Accepted: 09/01/2020] [Indexed: 11/13/2022] Open
Abstract
Mycobacterium avium complex (MAC) species are the most commonly isolated nontuberculous mycobacteria to cause pulmonary infections worldwide. The lengthy and complicated therapy required to cure lung disease due to MAC is at least in part due to the phenomenon of antibiotic tolerance. In this review, we will define antibiotic tolerance and contrast it with persistence and antibiotic resistance. We will discuss physiologically relevant stress conditions that induce altered metabolism and antibiotic tolerance in mycobacteria. Next, we will review general molecular mechanisms underlying bacterial antibiotic tolerance, particularly those described for MAC and related mycobacteria, including Mycobacterium tuberculosis, with a focus on genes containing significant sequence homology in MAC. An improved understanding of antibiotic tolerance mechanisms can lay the foundation for novel approaches to target antibiotic-tolerant mycobacteria, with the goal of shortening the duration of curative treatment and improving survival in patients with MAC.
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Affiliation(s)
- Harley Parker
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Rachel Lorenc
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Jennie Ruelas Castillo
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States
| | - Petros C Karakousis
- Department of Medicine, Johns Hopkins University School of Medicine, Baltimore, MD, United States.,Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD, United States
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15
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Vargas-Blanco DA, Shell SS. Regulation of mRNA Stability During Bacterial Stress Responses. Front Microbiol 2020; 11:2111. [PMID: 33013770 PMCID: PMC7509114 DOI: 10.3389/fmicb.2020.02111] [Citation(s) in RCA: 39] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/28/2020] [Accepted: 08/11/2020] [Indexed: 12/12/2022] Open
Abstract
Bacteria have a remarkable ability to sense environmental changes, swiftly regulating their transcriptional and posttranscriptional machinery as a response. Under conditions that cause growth to slow or stop, bacteria typically stabilize their transcriptomes in what has been shown to be a conserved stress response. In recent years, diverse studies have elucidated many of the mechanisms underlying mRNA degradation, yet an understanding of the regulation of mRNA degradation under stress conditions remains elusive. In this review we discuss the diverse mechanisms that have been shown to affect mRNA stability in bacteria. While many of these mechanisms are transcript-specific, they provide insight into possible mechanisms of global mRNA stabilization. To that end, we have compiled information on how mRNA fate is affected by RNA secondary structures; interaction with ribosomes, RNA binding proteins, and small RNAs; RNA base modifications; the chemical nature of 5' ends; activity and concentration of RNases and other degradation proteins; mRNA and RNase localization; and the stringent response. We also provide an analysis of reported relationships between mRNA abundance and mRNA stability, and discuss the importance of stress-associated mRNA stabilization as a potential target for therapeutic development.
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Affiliation(s)
- Diego A Vargas-Blanco
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, United States
| | - Scarlet S Shell
- Department of Biology and Biotechnology, Worcester Polytechnic Institute, Worcester, MA, United States.,Program in Bioinformatics and Computational Biology, Worcester Polytechnic Institute, Worcester, MA, United States
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16
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Balaure PC, Grumezescu AM. Recent Advances in Surface Nanoengineering for Biofilm Prevention and Control. Part I: Molecular Basis of Biofilm Recalcitrance. Passive Anti-Biofouling Nanocoatings. NANOMATERIALS (BASEL, SWITZERLAND) 2020; 10:E1230. [PMID: 32599948 PMCID: PMC7353097 DOI: 10.3390/nano10061230] [Citation(s) in RCA: 26] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/11/2020] [Revised: 06/19/2020] [Accepted: 06/20/2020] [Indexed: 12/17/2022]
Abstract
Medical device-associated infections are becoming a leading cause of morbidity and mortality worldwide, prompting researchers to find new, more effective ways to control the bacterial colonisation of surfaces and biofilm development. Bacteria in biofilms exhibit a set of "emergent properties", meaning those properties that are not predictable from the study of free-living bacterial cells. The social coordinated behaviour in the biofilm lifestyle involves intricate signaling pathways and molecular mechanisms underlying the gain in resistance and tolerance (recalcitrance) towards antimicrobial agents as compared to free-floating bacteria. Nanotechnology provides powerful tools to disrupt the processes responsible for recalcitrance development in all stages of the biofilm life cycle. The present paper is a state-of-the-art review of the surface nanoengineering strategies currently used to design antibiofilm coatings. The review is structurally organised in two parts according to the targeted biofilm life cycle stages and molecular mechanisms intervening in recalcitrance development. Therefore, in the present first part, we begin with a presentation of the current knowledge of the molecular mechanisms responsible for increased recalcitrance that have to be disrupted. Further, we deal with passive surface nanoengineering strategies that aim to prevent bacterial cells from settling onto a biotic or abiotic surface. Both "fouling-resistant" and "fouling release" strategies are addressed as well as their synergic combination in a single unique nanoplatform.
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Affiliation(s)
- Paul Cătălin Balaure
- “Costin Nenitzescu” Department of Organic Chemistry, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, G. Polizu Street 1-7, 011061 Bucharest, Romania
| | - Alexandru Mihai Grumezescu
- Department of Science and Engineering of Oxide Materials and Nanomaterials, Faculty of Applied Chemistry and Materials Science, University Politehnica of Bucharest, G. Polizu Street 1-7, 011061 Bucharest, Romania
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17
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The alarmones (p)ppGpp directly regulate translation initiation during entry into quiescence. Proc Natl Acad Sci U S A 2020; 117:15565-15572. [PMID: 32576694 DOI: 10.1073/pnas.1920013117] [Citation(s) in RCA: 53] [Impact Index Per Article: 13.3] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
Abstract
Many bacteria exist in a state of metabolic quiescence where energy consumption must be minimized so as to maximize available resources over a potentially extended period of time. As protein synthesis is the most energy intensive metabolic process in a bacterial cell, it would be an appropriate target for down-regulation during the transition from growth to quiescence. We observe that when Bacillus subtilis exits rapid growth, a subpopulation of cells emerges with very low protein synthetic activity. This phenotypic heterogeneity requires the production of the nucleotides (p)ppGpp, which we show are sufficient to inhibit protein synthesis in vivo. We then show that one of these molecules, ppGpp, inhibits protein synthesis by preventing the allosteric activation of the essential GTPase Initiation Factor 2 (IF2) during translation initiation. Finally, we demonstrate that the observed attenuation of protein synthesis during the entry into quiescence is a consequence of the direct interaction of (p)ppGpp and IF2.
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18
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Kumar J, Chauhan AS, Shah RL, Gupta JA, Rathore AS. Amino acid supplementation for enhancing recombinant protein production in
E. coli. Biotechnol Bioeng 2020; 117:2420-2433. [DOI: 10.1002/bit.27371] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2020] [Accepted: 05/03/2020] [Indexed: 12/19/2022]
Affiliation(s)
- Jashwant Kumar
- Department of Chemical EngineeringIndian Institute of TechnologyNew Delhi India
| | - Ashish S. Chauhan
- Department of Chemical EngineeringIndian Institute of TechnologyNew Delhi India
| | - Rohan L. Shah
- Department of Chemical EngineeringIndian Institute of TechnologyNew Delhi India
| | - Jaya A. Gupta
- Department of Chemical EngineeringIndian Institute of TechnologyNew Delhi India
| | - Anurag S. Rathore
- Department of Chemical EngineeringIndian Institute of TechnologyNew Delhi India
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19
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Gummesson B, Shah SA, Borum AS, Fessler M, Mitarai N, Sørensen MA, Svenningsen SL. Valine-Induced Isoleucine Starvation in Escherichia coli K-12 Studied by Spike-In Normalized RNA Sequencing. Front Genet 2020; 11:144. [PMID: 32211022 PMCID: PMC7066862 DOI: 10.3389/fgene.2020.00144] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2019] [Accepted: 02/07/2020] [Indexed: 12/19/2022] Open
Abstract
Escherichia coli cells respond to a period of famine by globally reorganizing their gene expression. The changes are known as the stringent response, which is orchestrated by the alarmone ppGpp that binds directly to RNA polymerase. The resulting changes in gene expression are particularly well studied in the case of amino acid starvation. We used deep RNA sequencing in combination with spike-in cells to measure global changes in the transcriptome after valine-induced isoleucine starvation of a standard E. coli K12 strain. Owing to the whole-cell spike-in method that eliminates variations in RNA extraction efficiency between samples, we show that ribosomal RNA levels are reduced during isoleucine starvation and we quantify how the change in cellular RNA content affects estimates of gene regulation. Specifically, we show that standard data normalization relying on sample sequencing depth underestimates the number of down-regulated genes in the stringent response and overestimates the number of up-regulated genes by approximately 40%. The whole-cell spike-in method also made it possible to quantify how rapidly the pool of total messenger RNA (mRNA) decreases upon amino acid starvation. A principal component analysis showed that the first two components together described 69% of the variability of the data, underlining that large and highly coordinated regulons are at play in the stringent response. The induction of starvation by sudden addition of high valine concentrations provoked prominent regulatory responses outside of the expected ppGpp, RpoS, and Lrp regulons. This underlines the notion that with the high resolution possible in deep RNA sequencing analysis, any different starvation method (e.g., nitrogen-deprivation, removal of an amino acid from an auxotroph strain, or valine addition to E. coli K12 strains) will produce measurable variations in the stress response produced by the cells to cope with the specific treatment.
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Affiliation(s)
- Bertil Gummesson
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Shiraz Ali Shah
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | | | - Mathias Fessler
- Department of Biology, University of Copenhagen, Copenhagen, Denmark
| | - Namiko Mitarai
- Niels Bohr Institute, University of Copenhagen, Copenhagen, Denmark
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20
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The Application of Ribosome Engineering to Natural Product Discovery and Yield Improvement in Streptomyces. Antibiotics (Basel) 2019; 8:antibiotics8030133. [PMID: 31480298 PMCID: PMC6784132 DOI: 10.3390/antibiotics8030133] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2019] [Revised: 08/10/2019] [Accepted: 08/27/2019] [Indexed: 12/23/2022] Open
Abstract
Microbial natural product drug discovery and development has entered a new era, driven by microbial genomics and synthetic biology. Genome sequencing has revealed the vast potential to produce valuable secondary metabolites in bacteria and fungi. However, many of the biosynthetic gene clusters are silent under standard fermentation conditions. By rational screening for mutations in bacterial ribosomal proteins or RNA polymerases, ribosome engineering is a versatile approach to obtain mutants with improved titers for microbial product formation or new natural products through activating silent biosynthetic gene clusters. In this review, we discuss the mechanism of ribosome engineering and its application to natural product discovery and yield improvement in Streptomyces. Our analysis suggests that ribosome engineering is a rapid and cost-effective approach and could be adapted to speed up the discovery and development of natural product drug leads in the post-genomic era.
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21
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Bervoets I, Charlier D. Diversity, versatility and complexity of bacterial gene regulation mechanisms: opportunities and drawbacks for applications in synthetic biology. FEMS Microbiol Rev 2019; 43:304-339. [PMID: 30721976 PMCID: PMC6524683 DOI: 10.1093/femsre/fuz001] [Citation(s) in RCA: 87] [Impact Index Per Article: 17.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/27/2018] [Accepted: 01/21/2019] [Indexed: 12/15/2022] Open
Abstract
Gene expression occurs in two essential steps: transcription and translation. In bacteria, the two processes are tightly coupled in time and space, and highly regulated. Tight regulation of gene expression is crucial. It limits wasteful consumption of resources and energy, prevents accumulation of potentially growth inhibiting reaction intermediates, and sustains the fitness and potential virulence of the organism in a fluctuating, competitive and frequently stressful environment. Since the onset of studies on regulation of enzyme synthesis, numerous distinct regulatory mechanisms modulating transcription and/or translation have been discovered. Mostly, various regulatory mechanisms operating at different levels in the flow of genetic information are used in combination to control and modulate the expression of a single gene or operon. Here, we provide an extensive overview of the very diverse and versatile bacterial gene regulatory mechanisms with major emphasis on their combined occurrence, intricate intertwinement and versatility. Furthermore, we discuss the potential of well-characterized basal expression and regulatory elements in synthetic biology applications, where they may ensure orthogonal, predictable and tunable expression of (heterologous) target genes and pathways, aiming at a minimal burden for the host.
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Affiliation(s)
- Indra Bervoets
- Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
| | - Daniel Charlier
- Research Group of Microbiology, Department of Bioengineering Sciences, Vrije Universiteit Brussel, Pleinlaan 2, B-1050 Brussels, Belgium
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22
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Abstract
The logistics of tuberculosis therapy are difficult, requiring multiple drugs for many months. Mycobacterium tuberculosis survives in part by entering nongrowing states in which it is metabolically less active and thus less susceptible to antibiotics. Basic knowledge on how M. tuberculosis survives during these low-metabolism states is incomplete, and we hypothesize that optimized energy resource management is important. Here, we report that slowed mRNA turnover is a common feature of mycobacteria under energy stress but is not dependent on the mechanisms that have generally been postulated in the literature. Finally, we found that mRNA stability and growth status can be decoupled by a drug that causes growth arrest but increases metabolic activity, indicating that mRNA stability responds to metabolic status rather than to growth rate per se. Our findings suggest a need to reorient studies of global mRNA stabilization to identify novel mechanisms that are presumably responsible. The success of Mycobacterium tuberculosis as a human pathogen is due in part to its ability to survive stress conditions, such as hypoxia or nutrient deprivation, by entering nongrowing states. In these low-metabolism states, M. tuberculosis can tolerate antibiotics and develop genetically encoded antibiotic resistance, making its metabolic adaptation to stress crucial for survival. Numerous bacteria, including M. tuberculosis, have been shown to reduce their rates of mRNA degradation under growth limitation and stress. While the existence of this response appears to be conserved across species, the underlying bacterial mRNA stabilization mechanisms remain unknown. To better understand the biology of nongrowing mycobacteria, we sought to identify the mechanistic basis of mRNA stabilization in the nonpathogenic model Mycobacterium smegmatis. We found that mRNA half-life was responsive to energy stress, with carbon starvation and hypoxia causing global mRNA stabilization. This global stabilization was rapidly reversed when hypoxia-adapted cultures were reexposed to oxygen, even in the absence of new transcription. The stringent response and RNase levels did not explain mRNA stabilization, nor did transcript abundance. This led us to hypothesize that metabolic changes during growth cessation impact the activities of degradation proteins, increasing mRNA stability. Indeed, bedaquiline and isoniazid, two drugs with opposing effects on cellular energy status, had opposite effects on mRNA half-lives in growth-arrested cells. Taken together, our results indicate that mRNA stability in mycobacteria is not directly regulated by growth status but rather is dependent on the status of energy metabolism.
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23
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Turtola M, Mäkinen JJ, Belogurov GA. Active site closure stabilizes the backtracked state of RNA polymerase. Nucleic Acids Res 2018; 46:10870-10887. [PMID: 30256972 PMCID: PMC6237748 DOI: 10.1093/nar/gky883] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/19/2018] [Revised: 08/30/2018] [Accepted: 09/19/2018] [Indexed: 01/02/2023] Open
Abstract
All cellular RNA polymerases (RNAP) occasionally backtrack along the template DNA as part of transcriptional proofreading and regulation. Here, we studied the mechanism of RNAP backtracking by one nucleotide using two complementary approaches that allowed us to precisely measure the occupancy and lifetime of the backtracked state. Our data show that the stability of the backtracked state is critically dependent on the closure of the RNAP active site by a mobile domain, the trigger loop (TL). The lifetime and occupancy of the backtracked state measurably decreased by substitutions of the TL residues that interact with the nucleoside triphosphate (NTP) substrate, whereas amino acid substitutions that stabilized the closed active site increased the lifetime and occupancy. These results suggest that the same conformer of the TL closes the active site during catalysis of nucleotide incorporation into the nascent RNA and backtracking by one nucleotide. In support of this hypothesis, we construct a model of the 1-nt backtracked complex with the closed active site and the backtracked nucleotide in the entry pore area known as the E-site. We further propose that 1-nt backtracking mimics the reversal of the NTP substrate loading into the RNAP active site during on-pathway elongation.
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Affiliation(s)
- Matti Turtola
- University of Turku, Department of Biochemistry, FIN-20014 Turku, Finland
| | - Janne J Mäkinen
- University of Turku, Department of Biochemistry, FIN-20014 Turku, Finland
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24
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Basu P, Bhadra RK. Post-transcriptional regulation of cholera toxin production in Vibrio cholerae by the stringent response regulator DksA. MICROBIOLOGY-SGM 2018; 165:102-112. [PMID: 30444469 DOI: 10.1099/mic.0.000743] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Expression of cholera toxin (CT), the principal virulence factor of the cholera pathogen Vibrio cholerae, is positively modulated by the RNA polymerase binding unusual transcription factor DksA (DksAVc) of the stringent response pathway. Here we report that even though CT (encoded by the genes ctxAB) production is downregulated in the V. cholerae ΔdksA (ΔdksAVc) mutant, the expression of the ctxA gene as well as the genes encoding different virulence regulators, namely, AphA, TcpP and ToxT, were also upregulated. Since DksAVc positively regulates HapR, a known negative regulator of CT production, the increased expression of different virulence genes in ΔdksAVc was due most probably to downregulation of HapR. There was no secretion/transport-related defect in ΔdksAVc cells because whole cell lysates of the mutant showed a negligible amount of CT accumulation similar to WT cells. To understand further, the hapR gene was deleted in ΔdksAVc background, however, the double mutant failed to rescue the CT production defect suggesting strongly towards post-transcriptional/translational regulation by DksAVc. This hypothesis was further confirmed when the site-directed mutagenesis of each or both of the conserved aspartic acid residues at positions 68 and 71 of DksAVc, which are essential for transcription initiation during the stringent response, had no effect in the regulation of CT expression. Interestingly, progressive deletion analysis indicated that the C4-type Zn finger motif present in the C-terminus of DksAVc is essential for optimal CT production. Since this motif plays important roles in DNA/RNA binding, the present study indicates a novel complex post-transcriptional regulation of CT expression by DksAVc.
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Affiliation(s)
- Pallabi Basu
- Infectious Diseases and Immunology Division, CSIR-Indian Institute of Chemical Biology, Kolkata-700 032, India
| | - Rupak K Bhadra
- Infectious Diseases and Immunology Division, CSIR-Indian Institute of Chemical Biology, Kolkata-700 032, India
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25
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Portelli S, Phelan JE, Ascher DB, Clark TG, Furnham N. Understanding molecular consequences of putative drug resistant mutations in Mycobacterium tuberculosis. Sci Rep 2018; 8:15356. [PMID: 30337649 PMCID: PMC6193939 DOI: 10.1038/s41598-018-33370-6] [Citation(s) in RCA: 52] [Impact Index Per Article: 8.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2018] [Accepted: 09/26/2018] [Indexed: 12/21/2022] Open
Abstract
Genomic studies of Mycobacterium tuberculosis bacteria have revealed loci associated with resistance to anti-tuberculosis drugs. However, the molecular consequences of polymorphism within these candidate loci remain poorly understood. To address this, we have used computational tools to quantify the effects of point mutations conferring resistance to three major anti-tuberculosis drugs, isoniazid (n = 189), rifampicin (n = 201) and D-cycloserine (n = 48), within their primary targets, katG, rpoB, and alr. Notably, mild biophysical effects brought about by high incidence mutations were considered more tolerable, while different structural effects brought about by haplotype combinations reflected differences in their functional importance. Additionally, highly destabilising mutations such as alr Y388, highlighted a functional importance of the wildtype residue. Our qualitative analysis enabled us to relate resistance mutations onto a theoretical landscape linking enthalpic changes with phenotype. Such insights will aid the development of new resistance-resistant drugs and, via an integration into predictive tools, in pathogen surveillance.
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Affiliation(s)
- Stephanie Portelli
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Victoria, 3051, Australia
| | - Jody E Phelan
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - David B Ascher
- Department of Biochemistry and Molecular Biology, Bio21 Institute, University of Melbourne, Victoria, 3051, Australia
| | - Taane G Clark
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
- Department of Infectious Disease Epidemiology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK
| | - Nicholas Furnham
- Department of Pathogen Molecular Biology, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, UK.
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26
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Choi E, Hwang J. The GTPase BipA expressed at low temperature in Escherichia coli assists ribosome assembly and has chaperone-like activity. J Biol Chem 2018; 293:18404-18419. [PMID: 30305394 DOI: 10.1074/jbc.ra118.002295] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/07/2018] [Revised: 09/27/2018] [Indexed: 12/29/2022] Open
Abstract
BPI-inducible protein A (BipA) is a conserved ribosome-associated GTPase in bacteria that is structurally similar to other GTPases associated with protein translation, including IF2, EF-Tu, and EF-G. Its binding site on the ribosome appears to overlap those of these translational GTPases. Mutations in the bipA gene cause a variety of phenotypes, including cold and antibiotics sensitivities and decreased pathogenicity, implying that BipA may participate in diverse cellular processes by regulating translation. According to recent studies, a bipA-deletion strain of Escherichia coli displays a ribosome assembly defect at low temperature, suggesting that BipA might be involved in ribosome assembly. To further investigate BipA's role in ribosome biogenesis, here, we compared and analyzed the ribosomal protein compositions of MG1655 WT and bipA-deletion strains at 20 °C. Aberrant 50S ribosomal subunits (i.e. 44S particles) accumulated in the bipA-deletion strain at 20 °C, and the ribosomal protein L6 was absent in these 44S particles. Furthermore, bipA expression was significantly stimulated at 20 °C, suggesting that it encodes a cold shock-inducible GTPase. Moreover, the transcriptional regulator cAMP receptor protein (CRP) positively promoted bipA expression only at 20 °C. Importantly, GFP and α-glucosidase refolding assays revealed that BipA has chaperone activity. Our findings indicate that BipA is a cold shock-inducible GTPase that participates in 50S ribosomal subunit assembly by incorporating the L6 ribosomal protein into the 44S particle during the assembly.
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Affiliation(s)
- Eunsil Choi
- From the Department of Microbiology, Pusan National University, Busan 46241, Korea
| | - Jihwan Hwang
- From the Department of Microbiology, Pusan National University, Busan 46241, Korea.
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27
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Gourse RL, Chen AY, Gopalkrishnan S, Sanchez-Vazquez P, Myers A, Ross W. Transcriptional Responses to ppGpp and DksA. Annu Rev Microbiol 2018; 72:163-184. [PMID: 30200857 PMCID: PMC6586590 DOI: 10.1146/annurev-micro-090817-062444] [Citation(s) in RCA: 142] [Impact Index Per Article: 23.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
The stringent response to nutrient deprivation is a stress response found throughout the bacterial domain of life. Although first described in proteobacteria for matching ribosome synthesis to the cell's translation status and for preventing formation of defective ribosomal particles, the response is actually much broader, regulating many hundreds of genes-some positively, some negatively. Utilization of the signaling molecules ppGpp and pppGpp for this purpose is ubiquitous in bacterial evolution, although the mechanisms employed vary. In proteobacteria, the signaling molecules typically bind to two sites on RNA polymerase, one at the interface of the β' and ω subunits and one at the interface of the β' secondary channel and the transcription factor DksA. The β' secondary channel is targeted by other transcription regulators as well. Although studies on the transcriptional outputs of the stringent response date back at least 50 years, the mechanisms responsible are only now coming into focus.
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Affiliation(s)
- Richard L Gourse
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA; , , , , ,
| | - Albert Y Chen
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA; , , , , ,
| | - Saumya Gopalkrishnan
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA; , , , , ,
| | - Patricia Sanchez-Vazquez
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA; , , , , ,
| | | | - Wilma Ross
- Department of Bacteriology, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA; , , , , ,
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28
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Baral B, Akhgari A, Metsä-Ketelä M. Activation of microbial secondary metabolic pathways: Avenues and challenges. Synth Syst Biotechnol 2018; 3:163-178. [PMID: 30345402 PMCID: PMC6190515 DOI: 10.1016/j.synbio.2018.09.001] [Citation(s) in RCA: 103] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 08/28/2018] [Accepted: 09/04/2018] [Indexed: 12/21/2022] Open
Abstract
Microbial natural products are a tremendous source of new bioactive chemical entities for drug discovery. Next generation sequencing has revealed an unprecedented genomic potential for production of secondary metabolites by diverse micro-organisms found in the environment and in the microbiota. Genome mining has further led to the discovery of numerous uncharacterized 'cryptic' metabolic pathways in the classical producers of natural products such as Actinobacteria and fungi. These biosynthetic gene clusters may code for improved biologically active metabolites, but harnessing the full genetic potential has been hindered by the observation that many of the pathways are 'silent' under laboratory conditions. Here we provide an overview of the various biotechnological methodologies, which can be divided to pleiotropic, biosynthetic gene cluster specific, and targeted genome-wide approaches that have been developed for the awakening of microbial secondary metabolic pathways.
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Affiliation(s)
| | | | - Mikko Metsä-Ketelä
- Department of Biochemistry, University of Turku, FIN-20014, Turku, Finland
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29
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Combined Drug Resistance Mutations Substantially Enhance Enzyme Production in Paenibacillus agaridevorans. J Bacteriol 2018; 200:JB.00188-18. [PMID: 29866810 DOI: 10.1128/jb.00188-18] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2018] [Accepted: 05/29/2018] [Indexed: 11/20/2022] Open
Abstract
This study shows that sequential introduction of drug resistance mutations substantially increased enzyme production in Paenibacillus agaridevorans The triple mutant YT478 (rsmG Gln225→stop codon, rpsL K56R, and rpoB R485H), generated by screening for resistance to streptomycin and rifampin, expressed a 1,100-fold-larger amount of the extracellular enzyme cycloisomaltooligosaccharide glucanotransferase (CITase) than the wild-type strain. These mutants were characterized by higher intracellular S-adenosylmethionine concentrations during exponential phase and enhanced protein synthesis activity during stationary phase. Surprisingly, the maximal expression of CITase mRNA was similar in the wild-type and triple mutant strains, but the mutant showed greater CITase mRNA expression throughout the growth curve, resulting in enzyme overproduction. A metabolome analysis showed that the triple mutant YT478 had higher levels of nucleic acids and glycolysis metabolites than the wild type, indicating that YT478 mutant cells were activated. The production of CITase by the triple mutant was further enhanced by introducing a mutation conferring resistance to the rare earth element, scandium. This combined drug resistance mutation method also effectively enhanced the production of amylases, proteases, and agarases by P. agaridevorans and Streptomyces coelicolor This method also activated the silent or weak expression of the P. agaridevorans CITase gene, as shown by comparisons of the CITase gene loci of P. agaridevorans T-3040 and another cycloisomaltooligosaccharide-producing bacterium, Paenibacillus sp. strain 598K. The simplicity and wide applicability of this method should facilitate not only industrial enzyme production but also the identification of dormant enzymes by activating the expression of silent or weakly expressed genes.IMPORTANCE Enzyme use has become more widespread in industry. This study evaluated the molecular basis and effectiveness of ribosome engineering in markedly enhancing enzyme production (>1,000-fold). This method, due to its simplicity, wide applicability, and scalability for large-scale production, should facilitate not only industrial enzyme production but also the identification of novel enzymes, because microorganisms contain many silent or weakly expressed genes which encode novel antibiotics or enzymes. Furthermore, this study provides a new mechanism for strain improvement, with a consistent rather than transient high expression of the key gene(s) involved in enzyme production.
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30
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Bruhn-Olszewska B, Molodtsov V, Sobala M, Dylewski M, Murakami KS, Cashel M, Potrykus K. Structure-function comparisons of (p)ppApp vs (p)ppGpp for Escherichia coli RNA polymerase binding sites and for rrnB P1 promoter regulatory responses in vitro. BIOCHIMICA ET BIOPHYSICA ACTA. GENE REGULATORY MECHANISMS 2018; 1861:731-742. [PMID: 30012465 PMCID: PMC6114088 DOI: 10.1016/j.bbagrm.2018.07.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/27/2018] [Revised: 07/03/2018] [Accepted: 07/11/2018] [Indexed: 12/27/2022]
Abstract
Precise regulation of gene expression is crucial for bacteria to respond to changing environmental conditions. In addition to protein factors affecting RNA polymerase (RNAP) activity, second messengers play an important role in transcription regulation, such as well-known effectors of the stringent response: guanosine 5'triphosphate-3'diphosphate and guanosine 3', 5'-bis(diphosphate) [(p)ppGpp]. Although much is known about importance of the 5' and 3' moieties of (p)ppGpp, the role of the guanine base remains somewhat cryptic. Here, we use (p)ppGpp's adenine analogs [(p)ppApp] to investigate how the nucleobase contributes to determine its binding site and transcriptional regulation. We determined X-ray crystal structure of Escherichia coli RNAP-(p)ppApp complex, which shows the analogs bind near the active site and switch regions of RNAP. We have also explored the regulatory effects of (p)ppApp on transcription initiating from the well-studied E. coli rrnB P1 promoter to assess and compare properties of (p)ppApp with (p)ppGpp. We demonstrate that contrary to (p)ppGpp, (p)ppApp activates transcription at this promoter and DksA hinders this effect. Moreover, pppApp exerts a stronger effect than ppApp. We also show that when ppGpp and pppApp are present together, the outcome depends on which one of them was pre-incubated with RNAP first. This behavior suggests a surprising Yin-Yang like reciprocal plasticity of RNAP responses at a single promoter, occasioned simply by pre-exposure to one or the other nucleotide. Our observations underscore the importance of the (p)ppNpp's purine nucleobase for interactions with RNAP, which may lead to a better fundamental understanding of (p)ppGpp regulation of RNAP activity.
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Affiliation(s)
- Bożena Bruhn-Olszewska
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland.
| | - Vadim Molodtsov
- Department of Biochemistry and Molecular Biology, Center of RNA Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA.
| | - Michał Sobala
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland.
| | - Maciej Dylewski
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland.
| | - Katsuhiko S Murakami
- Department of Biochemistry and Molecular Biology, Center of RNA Molecular Biology, Pennsylvania State University, University Park, PA 16802, USA.
| | - Michael Cashel
- Intramural Research Program, Eunice Kennedy Shriver NICHD, National Institutes of Health, Bethesda, MD 20892, USA.
| | - Katarzyna Potrykus
- Department of Bacterial Molecular Genetics, Faculty of Biology, University of Gdansk, Wita Stwosza 59, 80-308 Gdansk, Poland.
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Alkhateeb RS, Vorhölter FJ, Steffens T, Rückert C, Ortseifen V, Hublik G, Niehaus K, Pühler A. Comparative transcription profiling of two fermentation cultures of Xanthomonas campestris pv. campestris B100 sampled in the growth and in the stationary phase. Appl Microbiol Biotechnol 2018; 102:6613-6625. [DOI: 10.1007/s00253-018-9106-2] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/28/2018] [Revised: 05/07/2018] [Accepted: 05/08/2018] [Indexed: 10/14/2022]
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Ruwe M, Kalinowski J, Persicke M. Identification and Functional Characterization of Small Alarmone Synthetases in Corynebacterium glutamicum. Front Microbiol 2017; 8:1601. [PMID: 28871248 PMCID: PMC5566576 DOI: 10.3389/fmicb.2017.01601] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Accepted: 08/07/2017] [Indexed: 11/15/2022] Open
Abstract
The hyperphosphorylated guanosine derivatives ppGpp and pppGpp represent global regulators of the bacterial stress response, as they act as central elements of the stringent response system. Although it was assumed that both, (p)ppGpp synthesis and hydrolysis, are catalyzed by one bifunctional RSH-protein in the actinobacterial model organism Corynebacterium glutamicum ATCC 13032, two putative short alarmone synthetases (SASs) were identified by bioinformatic analyses. The predicted sequences of both enzymes, designated as RelP*Cg and RelSCg, exhibit high similarities to the conserved (p)ppGpp synthetase catalytic domain. In the context of sequence analysis, significant differences were found between the RelP variants of different C. glutamicum isolates. In contrast to the bifunctional RelA/SpoT homolog (RSH) protein RelCg, whose gene deletion results in a reduced growth rate, no change in growth characteristics were observed for deletion mutants of the putative SAS proteins under standard growth conditions. The growth deficit of the Δrel strain could be restored by the additional deletion of the gene encoding RelSCg, which clearly indicates a functional relationship between both enzymes. The predicted pyrophosphokinase activity of RelSCg was demonstrated by means of genetic complementation of an Escherichia coli ΔrelAΔspoT strain. For the expression of RelP*Cg, as well as the slightly differing variant RelPCg from C. glutamicum AS1.542, no complementation was observed, concluding that both RelP versions possess no significant pyrophosphokinase activity in vivo. The results were confirmed by in vitro characterization of the corresponding proteins. In the course of this investigation, the additional conversion of GMP to pGpp was determined for the enzyme RelSCg. Since the SAS species analyzed extend both the network of stringent response related enzymes and the number of substances involved, the study of this class of enzymes is an important component in understanding the bacterial stress response. In addition to the comprehension of important biological processes, such as growth rate regulation and the survival of pathogenic species in the host organism, SAS enzymes can be used to produce novel hyperphosphorylated nucleotide species, such as pGpp.
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Affiliation(s)
- Matthias Ruwe
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld UniversityBielefeld, Germany
| | - Jörn Kalinowski
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld UniversityBielefeld, Germany
| | - Marcus Persicke
- Microbial Genomics and Biotechnology, Center for Biotechnology, Bielefeld UniversityBielefeld, Germany
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33
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Tanaka Y, Kasahara K, Hirose Y, Morimoto Y, Izawa M, Ochi K. Enhancement of butanol production by sequential introduction of mutations conferring butanol tolerance and streptomycin resistance. J Biosci Bioeng 2017; 124:400-407. [PMID: 28566234 DOI: 10.1016/j.jbiosc.2017.05.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2017] [Revised: 05/01/2017] [Accepted: 05/06/2017] [Indexed: 12/19/2022]
Abstract
Ribosome engineering, originally applied to Streptomyces lividans, has been widely utilized for strain improvement, especially for the activation of bacterial secondary metabolism. This study assessed ribosome engineering technology to modulate primary metabolism, taking butanol production as a representative example. The introduction into Clostridium saccharoperbutylacetonicum of mutations conferring resistance to butanol (ButR) and of the str mutation (SmR; a mutation in the rpsL gene encoding ribosomal protein S12), conferring high-level resistance to streptomycin, increased butanol production 1.6-fold, to 16.5 g butanol/L. Real-time qPCR analysis demonstrated that the genes involved in butanol metabolism by C. saccharoperbutylacetonicum were activated at the transcriptional level in the drug-resistant mutants, providing a mechanism for the higher yields of butanol by the mutants. Moreover, the activity of enzymes butyraldehyde dehydrogenase (AdhE) and butanol dehydrogenases (BdhAB), the key enzymes involved in butanol synthesis, was both markedly increased in the ButR SmR mutant, reflecting the significant up-regulation of adhE and bdhA at transcriptional level in this mutant strain. These results demonstrate the efficacy of ribosome engineering for the production of not only secondary metabolites but of industrially important primary metabolites. The possible ways to overcome the reduced growth rate and/or fitness cost caused by the mutation were also discussed.
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Affiliation(s)
- Yukinori Tanaka
- Department of Life Sciences, Hiroshima Institute of Technology, Saeki-ku, Hiroshima 731-5193, Japan
| | - Ken Kasahara
- Chitose Laboratory Corp., Biotechnology Research Center, Nogawa, Miyamae-ku, Kawasaki 216-0001, Japan
| | - Yutaka Hirose
- Chitose Laboratory Corp., Biotechnology Research Center, Nogawa, Miyamae-ku, Kawasaki 216-0001, Japan
| | - Yu Morimoto
- Department of Life Sciences, Hiroshima Institute of Technology, Saeki-ku, Hiroshima 731-5193, Japan
| | - Masumi Izawa
- Department of Life Sciences, Hiroshima Institute of Technology, Saeki-ku, Hiroshima 731-5193, Japan
| | - Kozo Ochi
- Department of Life Sciences, Hiroshima Institute of Technology, Saeki-ku, Hiroshima 731-5193, Japan.
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In-silico prediction of dual function of DksA like hypothetical protein in V. cholerae O395 genome. Microbiol Res 2017; 195:60-70. [DOI: 10.1016/j.micres.2016.11.010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2016] [Revised: 11/04/2016] [Accepted: 11/05/2016] [Indexed: 11/20/2022]
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35
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Ramisetty BCM, Ghosh D, Roy Chowdhury M, Santhosh RS. What Is the Link between Stringent Response, Endoribonuclease Encoding Type II Toxin-Antitoxin Systems and Persistence? Front Microbiol 2016; 7:1882. [PMID: 27933045 PMCID: PMC5120126 DOI: 10.3389/fmicb.2016.01882] [Citation(s) in RCA: 49] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2016] [Accepted: 11/09/2016] [Indexed: 11/21/2022] Open
Abstract
Persistence is a transient and non-inheritable tolerance to antibiotics by a small fraction of a bacterial population. One of the proposed determinants of bacterial persistence is toxin–antitoxin systems (TASs) which are also implicated in a wide range of stress-related phenomena. Maisonneuve E, Castro-Camargo M, Gerdes K. 2013. Cell 154:1140–1150 reported an interesting link between ppGpp mediated stringent response, TAS, and persistence. It is proposed that accumulation of ppGpp enhances the accumulation of inorganic polyphosphate which modulates Lon protease to degrade antitoxins. The decrease in the concentration of antitoxins supposedly activated the toxin to increase in the number of persisters during antibiotic treatment. In this study, we show that inorganic polyphosphate is not required for transcriptional activation of yefM/yoeB TAS, which is an indirect indication of Lon-dependent degradation of YefM antitoxin. The Δ10 strain, an Escherichia coli MG1655 derivative in which the 10 TAS are deleted, is more sensitive to ciprofloxacin compared to wild type MG1655. Furthermore, we show that the Δ10 strain has relatively lower fitness compared to the wild type and hence, we argue that the persistence related implications based on Δ10 strain are void. We conclude that the transcriptional regulation and endoribonuclease activity of YefM/YoeB TAS is independent of ppGpp and inorganic polyphosphate. Therefore, we urge for thorough inspection and debate on the link between chromosomal endoribonuclease TAS and persistence.
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Affiliation(s)
- Bhaskar C M Ramisetty
- School of Chemical and Biotechnology, SASTRA UniversityThanjavur, India; Department of Biochemistry and Molecular Biology, University of Southern DenmarkOdense, Denmark
| | - Dimpy Ghosh
- School of Chemical and Biotechnology, SASTRA University Thanjavur, India
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36
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Hallez R. [Metabolism and cell cycle, two interconnected processes in bacteria]. Med Sci (Paris) 2016; 32:843-848. [PMID: 27758748 DOI: 10.1051/medsci/20163210017] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
To increase chances for a cell to survive in its natural environment, metabolism and cell cycle necessarily have to be interconnected. Indeed, cells need, on the one hand, to check their metabolic status before initiating a cell cycle step often energy-consuming, and, on the other hand, to complete some cell cycle steps before modifying their metabolism. Because bacteria do not differ from the rules, an increasing number of examples of connection between metabolism and cell cycle emerged these last years. Identifying metabolic enzymes as messengers coordinating metabolism and cell cycle allows the addition of another dimension to metabolic maps. Likewise, the very high conservation of these metabolic maps, from bacteria to human, allows inspiring research on tumor cells that are known to have an unrestrained cell cycle and a voracious appetite.
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Affiliation(s)
- Régis Hallez
- Bacterial Cell cycle and Development (BCcD), unité de recherche en biologie des micro-organismes (URBM), université de Namur (UNamur), 61 rue de Bruxelles, 5000 Namur, Belgique
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37
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Yang X, Ma C. In Vitro Transcription Assays and Their Application in Drug Discovery. J Vis Exp 2016. [PMID: 27684446 DOI: 10.3791/54256] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022] Open
Abstract
In vitro transcription assays have been developed and widely used for many years to study the molecular mechanisms involved in transcription. This process requires multi-subunit DNA-dependent RNA polymerase (RNAP) and a series of transcription factors that act to modulate the activity of RNAP during gene expression. Sequencing gel electrophoresis of radiolabeled transcripts is used to provide detailed mechanistic information on how transcription proceeds and what parameters can affect it. In this paper we describe the protocol to study how the essential elongation factor NusA regulates transcriptional pausing, as well as a method to identify an antibacterial agent targeting transcription initiation through inhibition of RNAP holoenzyme formation. These methods can be used a as platform for the development of additional approaches to explore the mechanism of action of the transcription factors which still remain unclear, as well as new antibacterial agents targeting transcription which is an underutilized drug target in antibiotic research and development.
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Affiliation(s)
- Xiao Yang
- School of Environmental and Life Sciences, University of Newcastle
| | - Cong Ma
- School of Environmental and Life Sciences, University of Newcastle; Department of Applied Biology and Chemical Technology, The State Key Laboratory of Chirosciences, The Hong Kong Polytechnic University;
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38
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Okada BK, Seyedsayamdost MR. Antibiotic dialogues: induction of silent biosynthetic gene clusters by exogenous small molecules. FEMS Microbiol Rev 2016; 41:19-33. [PMID: 27576366 DOI: 10.1093/femsre/fuw035] [Citation(s) in RCA: 137] [Impact Index Per Article: 17.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Revised: 06/03/2016] [Accepted: 07/29/2016] [Indexed: 12/21/2022] Open
Abstract
Natural products have traditionally served as a dominant source of therapeutic agents. They are produced by dedicated biosynthetic gene clusters that assemble complex, bioactive molecules from simple precursors. Recent genome sequencing efforts coupled with advances in bioinformatics indicate that the majority of biosynthetic gene clusters are not expressed under normal laboratory conditions. Termed 'silent' or 'cryptic', these gene clusters represent a treasure trove for discovery of novel small molecules, their regulatory circuits and their biosynthetic pathways. In this review, we assess the capacity of exogenous small molecules in activating silent secondary metabolite gene clusters. Several approaches that have been developed are presented, including coculture techniques, ribosome engineering, chromatin remodeling and high-throughput elicitor screens. The rationale, applications and mechanisms attendant to each are discussed. Some general conclusions can be drawn from our analysis: exogenous small molecules comprise a productive avenue for the discovery of cryptic metabolites. Specifically, growth-inhibitory molecules, in some cases clinically used antibiotics, serve as effective inducers of silent biosynthetic gene clusters, suggesting that old antibiotics may be used to find new ones. The involvement of natural antibiotics in modulating secondary metabolism at subinhibitory concentrations suggests that they represent part of the microbial vocabulary through which inter- and intraspecies interactions are mediated.
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Affiliation(s)
- Bethany K Okada
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA
| | - Mohammad R Seyedsayamdost
- Department of Chemistry, Princeton University, Princeton, NJ 08544, USA .,Department of Molecular Biology, Princeton University, Princeton, NJ 08544, USA
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39
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Sarkar S, Roberts LW, Phan MD, Tan L, Lo AW, Peters KM, Paterson DL, Upton M, Ulett GC, Beatson SA, Totsika M, Schembri MA. Comprehensive analysis of type 1 fimbriae regulation in fimB-null strains from the multidrug resistant Escherichia coli ST131 clone. Mol Microbiol 2016; 101:1069-87. [PMID: 27309594 DOI: 10.1111/mmi.13442] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/13/2016] [Indexed: 12/17/2022]
Abstract
Uropathogenic Escherichia coli (UPEC) of sequence type 131 (ST131) are a pandemic multidrug resistant clone associated with urinary tract and bloodstream infections. Type 1 fimbriae, a major UPEC virulence factor, are essential for ST131 bladder colonization. The globally dominant sub-lineage of ST131 strains, clade C/H30-R, possess an ISEc55 insertion in the fimB gene that controls phase-variable type 1 fimbriae expression via the invertible fimS promoter. We report that inactivation of fimB in these strains causes altered regulation of type 1 fimbriae expression. Using a novel read-mapping approach based on Illumina sequencing, we demonstrate that 'off' to 'on' fimS inversion is reduced in these strains and controlled by recombinases encoded by the fimE and fimX genes. Unlike typical UPEC strains, the nucleoid-associated H-NS protein does not strongly repress fimE transcription in clade C ST131 strains. Using a genetic screen to identify novel regulators of fimE and fimX in the clade C ST131 strain EC958, we defined a new role for the guaB gene in the regulation of type 1 fimbriae and in colonisation of the mouse bladder. Our results provide a comprehensive analysis of type 1 fimbriae regulation in ST131, and highlight important differences in its control compared to non-ST131 UPEC.
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Affiliation(s)
- Sohinee Sarkar
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, 4059, Australia
| | - Leah W Roberts
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Minh-Duy Phan
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Lendl Tan
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Alvin W Lo
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - Kate M Peters
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia
| | - David L Paterson
- Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.,Royal Brisbane and Women's Hospital, University of Queensland Centre for Clinical Research, Brisbane, Queensland, 4029, Australia
| | - Mathew Upton
- Plymouth University Peninsula Schools of Medicine and Dentistry, Plymouth, PL4 8AA, UK
| | - Glen C Ulett
- School of Medical Science, Menzies Health Institute Queensland, Griffith University, Gold Coast, Queensland, 4222, Australia
| | - Scott A Beatson
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.
| | - Makrina Totsika
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Institute of Health and Biomedical Innovation, School of Biomedical Sciences, Queensland University of Technology, Brisbane, Queensland, 4059, Australia.
| | - Mark A Schembri
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, Queensland, 4072, Australia. .,Australian Infectious Disease Research Centre, The University of Queensland, Brisbane, Queensland, 4072, Australia.
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40
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Insights into microbial cryptic gene activation and strain improvement: principle, application and technical aspects. J Antibiot (Tokyo) 2016; 70:25-40. [PMID: 27381522 DOI: 10.1038/ja.2016.82] [Citation(s) in RCA: 69] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2016] [Revised: 05/22/2016] [Accepted: 06/06/2016] [Indexed: 12/22/2022]
Abstract
As bacteria and fungi have been found to contain genes encoding enzymes that synthesize a plethora of potential secondary metabolites, interest has grown in the activation of these cryptic pathways. Homologous and heterologous expression of these cryptic secondary metabolite-biosynthetic genes, often silent under ordinary laboratory fermentation conditions, may lead to the discovery of novel secondary metabolites. This review addresses current progress in the activation of these pathways, describing methods for activating silent genes. It especially focuses on genetic manipulation of transcription and translation (ribosome engineering), the utilization of elicitors, metabolism remodeling and co-cultivation. In particular, the principles and technical points of ribosome engineering and the significance of S-adenosylmethionine in bacterial physiology, especially secondary metabolism, are described in detail.
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41
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Steinchen W, Bange G. The magic dance of the alarmones (p)ppGpp. Mol Microbiol 2016; 101:531-44. [PMID: 27149325 DOI: 10.1111/mmi.13412] [Citation(s) in RCA: 129] [Impact Index Per Article: 16.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/02/2016] [Indexed: 11/26/2022]
Abstract
The alarmones (p)ppGpp are important second messengers that orchestrate pleiotropic adaptations of bacteria and plant chloroplasts in response to starvation and stress. Here, we review our structural and mechanistic knowledge on (p)ppGpp metabolism including their synthesis, degradation and interconversion by a highly diverse set of enzymes. Increasing structural information shows how (p)ppGpp interacts with an incredibly diverse set of different targets that are essential for replication, transcription, translation, ribosome assembly and metabolism. This raises the question how the chemically rather simple (p)ppGpp is able to interact with these different targets? Structural analysis shows that the diversity of (p)ppGpp interaction with cellular targets critically relies on the conformational flexibility of the 3' and 5' phosphate moieties allowing alarmones to efficiently modulate the activity of target structures in a broad concentration range. Current approaches in the design of (p)ppGpp-analogs as future antibiotics might be aided by the comprehension of conformational flexibility exhibited by the magic dancers (p)ppGpp.
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Affiliation(s)
- Wieland Steinchen
- Department of Chemistry, LOEWE Center for Synthetic Microbiology (Synmikro), Philipps University Marburg, Hans-Meerwein-Strasse, Marburg, 35043, Germany
| | - Gert Bange
- Department of Chemistry, LOEWE Center for Synthetic Microbiology (Synmikro), Philipps University Marburg, Hans-Meerwein-Strasse, Marburg, 35043, Germany
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42
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Ross W, Sanchez-Vazquez P, Chen AY, Lee JH, Burgos HL, Gourse RL. ppGpp Binding to a Site at the RNAP-DksA Interface Accounts for Its Dramatic Effects on Transcription Initiation during the Stringent Response. Mol Cell 2016; 62:811-823. [PMID: 27237053 DOI: 10.1016/j.molcel.2016.04.029] [Citation(s) in RCA: 180] [Impact Index Per Article: 22.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/29/2016] [Revised: 04/06/2016] [Accepted: 04/22/2016] [Indexed: 11/30/2022]
Abstract
Throughout the bacterial domain, the alarmone ppGpp dramatically reprograms transcription following nutrient limitation. This "stringent response" is critical for survival and antibiotic tolerance and is a model for transcriptional regulation by small ligands. We report that ppGpp binds to two distinct sites 60 Å apart on E. coli RNA polymerase (RNAP), one characterized previously (site 1) and a second identified here at an interface of RNAP and the transcription factor DksA (site 2). The location and unusual tripartite nature of site 2 account for the DksA-ppGpp synergism and suggest mechanisms for ppGpp enhancement of DksA's effects on RNAP. Site 2 binding results in the majority of ppGpp's effects on transcription initiation in vitro and in vivo, and strains lacking site 2 are severely impaired for growth following nutritional shifts. Filling of the two sites at different ppGpp concentrations would expand the dynamic range of cellular responses to changes in ppGpp levels.
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Affiliation(s)
- Wilma Ross
- Department of Bacteriology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA
| | - Patricia Sanchez-Vazquez
- Department of Bacteriology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA
| | - Albert Y Chen
- Department of Bacteriology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA
| | - Jeong-Hyun Lee
- Department of Bacteriology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA
| | - Hector L Burgos
- Department of Bacteriology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA
| | - Richard L Gourse
- Department of Bacteriology, University of Wisconsin-Madison, 1550 Linden Drive, Madison, WI 53706, USA.
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Brandi A, Giangrossi M, Giuliodori AM, Falconi M. An Interplay among FIS, H-NS, and Guanosine Tetraphosphate Modulates Transcription of the Escherichia coli cspA Gene under Physiological Growth Conditions. Front Mol Biosci 2016; 3:19. [PMID: 27252944 PMCID: PMC4877382 DOI: 10.3389/fmolb.2016.00019] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2016] [Accepted: 05/01/2016] [Indexed: 11/13/2022] Open
Abstract
CspA, the most characterized member of the csp gene family of Escherichia coli, is highly expressed not only in response to cold stress, but also during the early phase of growth at 37°C. Here, we investigate at molecular level the antagonistic role played by the nucleoid proteins FIS and H-NS in the regulation of cspA expression under non-stress conditions. By means of both probing experiments and immunological detection, we demonstrate in vitro the existence of binding sites for these proteins on the cspA regulatory region, in which FIS and H-NS bind simultaneously to form composite DNA-protein complexes. While the in vitro promoter activity of cspA is stimulated by FIS and repressed by H-NS, a compensatory effect is observed when both proteins are added in the transcription assay. Consistently with these findings, inactivation of fis and hns genes reversely affect the in vivo amount of cspA mRNA. In addition, by means of strains expressing a high level of the alarmone guanosine tetraphosphate ((p)ppGpp) and in vitro transcription assays, we show that the cspA promoter is sensitive to (p)ppGpp inhibition. The (p)ppGpp-mediated expression of fis and hns genes is also analyzed, thus clarifying some aspects of the regulatory loop governing cspA transcription.
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Affiliation(s)
- Anna Brandi
- Laboratory of Genetics, School of Bioscience and Veterinary Medicine, University of Camerino Camerino, Italy
| | - Mara Giangrossi
- Laboratory of Genetics, School of Bioscience and Veterinary Medicine, University of Camerino Camerino, Italy
| | - Anna M Giuliodori
- Laboratory of Genetics, School of Bioscience and Veterinary Medicine, University of Camerino Camerino, Italy
| | - Maurizio Falconi
- Laboratory of Genetics, School of Bioscience and Veterinary Medicine, University of Camerino Camerino, Italy
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Fung AWS, Payoe R, Fahlman RP. Perspectives and Insights into the Competition for Aminoacyl-tRNAs between the Translational Machinery and for tRNA Dependent Non-Ribosomal Peptide Bond Formation. Life (Basel) 2015; 6:life6010002. [PMID: 26729173 PMCID: PMC4810233 DOI: 10.3390/life6010002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2015] [Revised: 12/23/2015] [Accepted: 12/25/2015] [Indexed: 12/19/2022] Open
Abstract
Aminoacyl-tRNA protein transferases catalyze the transfer of amino acids from aminoacyl-tRNAs to polypeptide substrates. Different forms of these enzymes are found in the different kingdoms of life and have been identified to be central to a wide variety of cellular processes. L/F-transferase is the sole member of this class of enzyme found in Escherichia coli and catalyzes the transfer of leucine to the N-termini of proteins which result in the targeted degradation of the modified protein. Recent investigations on the tRNA specificity of L/F-transferase have revealed the unique recognition nucleotides for a preferred Leu-tRNALeu isoacceptor substrate. In addition to discussing this tRNA selectivity by L/F-transferase, we present and discuss a hypothesis and its implications regarding the apparent competition for this aminoacyl-tRNA between L/F-transferase and the translational machinery. Our discussion reveals a hypothetical involvement of the bacterial stringent response that occurs upon amino acid limitation as a potential cellular event that may reduce this competition and provide the opportunity for L/F-transferase to readily increase its access to the pool of aminoacylated tRNA substrates.
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Affiliation(s)
- Angela W S Fung
- Department of Biochemistry, Faculty of Medicine & Dentistry, University of Alberta, 474-MSB Edmonton, AB T6G 2H7, Canada.
- Department of Laboratory Medicine and Pathobiology, Faculty of Medicine, University of Toronto, Toronto, ON M5S 1A1, Canada.
| | - Roshani Payoe
- Department of Biochemistry, Faculty of Medicine & Dentistry, University of Alberta, 474-MSB Edmonton, AB T6G 2H7, Canada.
- Institute of Technology, Faculty of Science and Technology, University of Tartu, Noorse St 1, Tartu 50411, Estonia.
| | - Richard P Fahlman
- Department of Biochemistry, Faculty of Medicine & Dentistry, University of Alberta, 474-MSB Edmonton, AB T6G 2H7, Canada.
- Department of Oncology, Faculty of Medicine & Dentistry, University of Alberta, Edmonton, AB T6G 2H7, Canada.
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Mechanism to control the cell lysis and the cell survival strategy in stationary phase under heat stress. SPRINGERPLUS 2015; 4:599. [PMID: 26543734 PMCID: PMC4627973 DOI: 10.1186/s40064-015-1415-7] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 03/15/2015] [Accepted: 10/07/2015] [Indexed: 11/10/2022]
Abstract
An array of stress signals triggering the bacterial cellular stress response is well known in Escherichia coli and other bacteria. Heat stress is usually sensed through the misfolded outer membrane porin (OMP) precursors in the periplasm, resulting in the activation of σ(E) (encoded by rpoE), which binds to RNA polymerase to start the transcription of genes required for responding against the heat stress signal. At the elevated temperatures, σ(E) also serves as the transcription factor for σ(H) (the main heat shock sigma factor, encoded by rpoH), which is involved in the expression of several genes whose products deal with the cytoplasmic unfolded proteins. Besides, oxidative stress in form of the reactive oxygen species (ROS) that accumulate due to heat stress, has been found to give rise to viable but non-culturable (VBNC) cells at the early stationary phase, which is in turn lysed by the σ(E)-dependent process. Such lysis of the defective cells may generate nutrients for the remaining population to survive with the capacity of formation of colony forming units (CFUs). σ(H) is also known to regulate the transcription of the major heat shock proteins (HSPs) required for heat shock response (HSR) resulting in cellular survival. Present review concentrated on the cellular survival against heat stress employing the harmonized impact of σ(E) and σ(H) regulons and the HSPs as well as their inter connectivity towards the maintenance of cellular survival.
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Syal K, Chatterji D. Differential binding of ppGpp and pppGpp to E. coli RNA polymerase: photo-labeling and mass spectral studies. Genes Cells 2015; 20:1006-16. [PMID: 26606426 DOI: 10.1111/gtc.12304] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/19/2015] [Accepted: 09/06/2015] [Indexed: 11/28/2022]
Abstract
(p)ppGpp, a secondary messenger, is induced under stress and shows pleiotropic response. It binds to RNA polymerase and regulates transcription in Escherichia coli. More than 25 years have passed since the first discovery was made on the direct interaction of ppGpp with E. coli RNA polymerase. Several lines of evidence suggest different modes of ppGpp binding to the enzyme. Earlier cross-linking experiments suggested that the β-subunit of RNA polymerase is the preferred site for ppGpp, whereas recent crystallographic studies pinpoint the interface of β'/ω-subunits as the site of action. With an aim to validate the binding domain and to follow whether tetra- and pentaphosphate guanosines have different location on RNA polymerase, this work was initiated. RNA polymerase was photo-labeled with 8-azido-ppGpp/8-azido-pppGpp, and the product was digested with trypsin and subjected to mass spectrometry analysis. We observed three new peptides in the trypsin digest of the RNA polymerase labeled with 8-azido-ppGpp, of which two peptides correspond to the same pocket on β'-subunit as predicted by X-ray structural analysis, whereas the third peptide was mapped on the β-subunit. In the case of 8-azido-pppGpp-labeled RNA polymerase, we have found only one cross-linked peptide from the β'-subunit. However, we were unable to identify any binding site of pppGpp on the β-subunit. Interestingly, we observed that pppGpp at high concentration competes out ppGpp bound to RNA polymerase more efficiently, whereas ppGpp cannot titrate out pppGpp. The competition between tetraphosphate guanosine and pentaphosphate guanosine for E. coli RNA polymerase was followed by gel-based assay as well as by a new method known as DRaCALA assay.
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Affiliation(s)
- Kirtimaan Syal
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India
| | - Dipankar Chatterji
- Molecular Biophysics Unit, Indian Institute of Science, Bangalore, 560012, India
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When Too Much ATP Is Bad for Protein Synthesis. J Mol Biol 2015; 427:2586-2594. [PMID: 26150063 DOI: 10.1016/j.jmb.2015.06.021] [Citation(s) in RCA: 73] [Impact Index Per Article: 8.1] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2015] [Revised: 06/30/2015] [Accepted: 06/30/2015] [Indexed: 01/17/2023]
Abstract
Adenosine triphosphate (ATP) is the energy currency of living cells. Even though ATP powers virtually all energy-dependent activities, most cellular ATP is utilized in protein synthesis via tRNA aminoacylation and guanosine triphosphate regeneration. Magnesium (Mg(2+)), the most common divalent cation in living cells, plays crucial roles in protein synthesis by maintaining the structure of ribosomes, participating in the biochemistry of translation initiation and functioning as a counterion for ATP. A non-physiological increase in ATP levels hinders growth in cells experiencing Mg(2+) limitation because ATP is the most abundant nucleotide triphosphate in the cell, and Mg(2+) is also required for the stabilization of the cytoplasmic membrane and as a cofactor for essential enzymes. We propose that organisms cope with Mg(2+) limitation by decreasing ATP levels and ribosome production, thereby reallocating Mg(2+) to indispensable cellular processes.
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Discovery of microbial natural products by activation of silent biosynthetic gene clusters. Nat Rev Microbiol 2015; 13:509-23. [PMID: 26119570 DOI: 10.1038/nrmicro3496] [Citation(s) in RCA: 615] [Impact Index Per Article: 68.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2023]
Abstract
Microorganisms produce a wealth of structurally diverse specialized metabolites with a remarkable range of biological activities and a wide variety of applications in medicine and agriculture, such as the treatment of infectious diseases and cancer, and the prevention of crop damage. Genomics has revealed that many microorganisms have far greater potential to produce specialized metabolites than was thought from classic bioactivity screens; however, realizing this potential has been hampered by the fact that many specialized metabolite biosynthetic gene clusters (BGCs) are not expressed in laboratory cultures. In this Review, we discuss the strategies that have been developed in bacteria and fungi to identify and induce the expression of such silent BGCs, and we briefly summarize methods for the isolation and structural characterization of their metabolic products.
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New Insights into the Functions of Transcription Factors that Bind the RNA Polymerase Secondary Channel. Biomolecules 2015; 5:1195-209. [PMID: 26120903 PMCID: PMC4598747 DOI: 10.3390/biom5031195] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2015] [Revised: 05/06/2015] [Accepted: 06/09/2015] [Indexed: 11/25/2022] Open
Abstract
Transcription elongation is regulated at several different levels, including control by various accessory transcription elongation factors. A distinct group of these factors interacts with the RNA polymerase secondary channel, an opening at the enzyme surface that leads to its active center. Despite investigation for several years, the activities and in vivo roles of some of these factors remain obscure. Here, we review the recent progress in understanding the functions of the secondary channel binding factors in bacteria. In particular, we highlight the surprising role of global regulator DksA in fidelity of RNA synthesis and the resolution of RNA polymerase traffic jams by the Gre factor. These findings indicate a potential link between transcription fidelity and collisions of the transcription and replication machineries.
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Structural biology of bacterial RNA polymerase. Biomolecules 2015; 5:848-64. [PMID: 25970587 PMCID: PMC4496699 DOI: 10.3390/biom5020848] [Citation(s) in RCA: 82] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Revised: 04/10/2015] [Accepted: 04/13/2015] [Indexed: 11/17/2022] Open
Abstract
Since its discovery and characterization in the early 1960s (Hurwitz, J. The discovery of RNA polymerase. J. Biol. Chem. 2005, 280, 42477-42485), an enormous amount of biochemical, biophysical and genetic data has been collected on bacterial RNA polymerase (RNAP). In the late 1990s, structural information pertaining to bacterial RNAP has emerged that provided unprecedented insights into the function and mechanism of RNA transcription. In this review, I list all structures related to bacterial RNAP (as determined by X-ray crystallography and NMR methods available from the Protein Data Bank), describe their contributions to bacterial transcription research and discuss the role that small molecules play in inhibiting bacterial RNA transcription.
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