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Zhang P, Zhang B, Ji Y, Jiao J, Zhang Z, Tian C. Cofitness network connectivity determines a fuzzy essential zone in open bacterial pangenome. MLIFE 2024; 3:277-290. [PMID: 38948139 PMCID: PMC11211677 DOI: 10.1002/mlf2.12132] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/07/2023] [Revised: 04/20/2024] [Accepted: 04/24/2024] [Indexed: 07/02/2024]
Abstract
Most in silico evolutionary studies commonly assumed that core genes are essential for cellular function, while accessory genes are dispensable, particularly in nutrient-rich environments. However, this assumption is seldom tested genetically within the pangenome context. In this study, we conducted a robust pangenomic Tn-seq analysis of fitness genes in a nutrient-rich medium for Sinorhizobium strains with a canonical open pangenome. To evaluate the robustness of fitness category assignment, Tn-seq data for three independent mutant libraries per strain were analyzed by three methods, which indicates that the Hidden Markov Model (HMM)-based method is most robust to variations between mutant libraries and not sensitive to data size, outperforming the Bayesian and Monte Carlo simulation-based methods. Consequently, the HMM method was used to classify the fitness category. Fitness genes, categorized as essential (ES), advantage (GA), and disadvantage (GD) genes for growth, are enriched in core genes, while nonessential genes (NE) are over-represented in accessory genes. Accessory ES/GA genes showed a lower fitness effect than core ES/GA genes. Connectivity degrees in the cofitness network decrease in the order of ES, GD, and GA/NE. In addition to accessory genes, 1599 out of 3284 core genes display differential essentiality across test strains. Within the pangenome core, both shared quasi-essential (ES and GA) and strain-dependent fitness genes are enriched in similar functional categories. Our analysis demonstrates a considerable fuzzy essential zone determined by cofitness connectivity degrees in Sinorhizobium pangenome and highlights the power of the cofitness network in understanding the genetic basis of ever-increasing prokaryotic pangenome data.
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Affiliation(s)
- Pan Zhang
- State Key Laboratory of Plant Environmental Resilience, and College of Biological SciencesChina Agricultural UniversityBeijingChina
- MOA Key Laboratory of Soil Microbiology, and Rhizobium Research CenterChina Agricultural UniversityBeijingChina
- Shenzhen Institute of Synthetic Biology, Shenzhen Institute of Advanced TechnologyChinese Academy of SciencesShenzhenChina
| | - Biliang Zhang
- MOA Key Laboratory of Soil Microbiology, and Rhizobium Research CenterChina Agricultural UniversityBeijingChina
- State Key Laboratory of Livestock and Poultry Biotechnology Breeding, and College of Biological SciencesChina Agricultural UniversityBeijingChina
| | - Yuan‐Yuan Ji
- State Key Laboratory of Plant Environmental Resilience, and College of Biological SciencesChina Agricultural UniversityBeijingChina
- MOA Key Laboratory of Soil Microbiology, and Rhizobium Research CenterChina Agricultural UniversityBeijingChina
| | - Jian Jiao
- State Key Laboratory of Plant Environmental Resilience, and College of Biological SciencesChina Agricultural UniversityBeijingChina
- MOA Key Laboratory of Soil Microbiology, and Rhizobium Research CenterChina Agricultural UniversityBeijingChina
| | - Ziding Zhang
- State Key Laboratory of Livestock and Poultry Biotechnology Breeding, and College of Biological SciencesChina Agricultural UniversityBeijingChina
| | - Chang‐Fu Tian
- State Key Laboratory of Plant Environmental Resilience, and College of Biological SciencesChina Agricultural UniversityBeijingChina
- MOA Key Laboratory of Soil Microbiology, and Rhizobium Research CenterChina Agricultural UniversityBeijingChina
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2
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Fiebig A, Schnizlein MK, Pena-Rivera S, Trigodet F, Dubey AA, Hennessy MK, Basu A, Pott S, Dalal S, Rubin D, Sogin ML, Eren AM, Chang EB, Crosson S. Bile acid fitness determinants of a Bacteroides fragilis isolate from a human pouchitis patient. mBio 2024; 15:e0283023. [PMID: 38063424 PMCID: PMC10790697 DOI: 10.1128/mbio.02830-23] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2023] [Accepted: 10/26/2023] [Indexed: 12/19/2023] Open
Abstract
IMPORTANCE The Gram-negative bacterium Bacteroides fragilis is a common member of the human gut microbiota that colonizes multiple host niches and can influence human physiology through a variety of mechanisms. Identification of genes that enable B. fragilis to grow across a range of host environments has been impeded in part by the relatively limited genetic tractability of this species. We have developed a high-throughput genetic resource for a B. fragilis strain isolated from a UC pouchitis patient. Bile acids limit microbial growth and are altered in abundance in UC pouches, where B. fragilis often blooms. Using this resource, we uncovered pathways and processes that impact B. fragilis fitness in bile and that may contribute to population expansions during bouts of gut inflammation.
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Affiliation(s)
- Aretha Fiebig
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Matthew K. Schnizlein
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Selymar Pena-Rivera
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Florian Trigodet
- Department of Medicine, University of Chicago, Chicago, Illinois, USA
- Helmholtz Institute for Functional Marine Biodiversity, University of Oldenburg, Oldenburg, Germany
| | - Abhishek Anil Dubey
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Miette K. Hennessy
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
| | - Anindita Basu
- Department of Medicine, University of Chicago, Chicago, Illinois, USA
| | - Sebastian Pott
- Department of Medicine, University of Chicago, Chicago, Illinois, USA
| | - Sushila Dalal
- Department of Medicine, University of Chicago, Chicago, Illinois, USA
| | - David Rubin
- Department of Medicine, University of Chicago, Chicago, Illinois, USA
| | | | - A. Murat Eren
- Department of Medicine, University of Chicago, Chicago, Illinois, USA
- Helmholtz Institute for Functional Marine Biodiversity, University of Oldenburg, Oldenburg, Germany
| | - Eugene B. Chang
- Department of Medicine, University of Chicago, Chicago, Illinois, USA
| | - Sean Crosson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, Michigan, USA
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3
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Hamami E, Huo W, Neal K, Neisewander I, Geisinger E, Isberg RR. Identification of essential genes that support fitness of Acinetobacter baumannii efflux pump overproducers in the presence of fluoroquinolone. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.01.04.574119. [PMID: 38260615 PMCID: PMC10802289 DOI: 10.1101/2024.01.04.574119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/24/2024]
Abstract
Acinetobacter baumannii is a nosocomial pathogen often associated with multidrug resistance (MDR) infections. Fluoroquinolone resistance (FQR) due to drug target site mutations and elevated expression of RND drug transporters is common among clinical isolates. We describe here a CRISPRi platform that identifies hypomorphic mutations that preferentially altered drug sensitivity in RND pump overproducers. An sgRNA library against essential genes of A. baumannii was constructed with single and double nucleotide mutations that produced titratable knockdown efficiencies and introduced into multiple strain backgrounds. Other than nusG depletions, there were few candidates in the absence of drug treatment that showed lowered fitness specifically in strains overexpressing clinically relevant RND efflux pumps AdeAB, AdeIJK, or AdeFGH. In the presence of ciprofloxacin, the hypomorphs causing hypersensitivity were predicted to result in outer membrane dysfunction, to which the AdeFGH overproducer appeared particularly sensitive. Depletions of either the outer membrane assembly BAM complex, LOS biogenesis proteins, or Lpt proteins involved in LOS transport to the outer membrane caused drug hypersensitivity in at least two of the three pump overproducers. On the other hand, depletions of translation-associated proteins, as well as components of the proton-pumping ATP synthase pump resulted in fitness benefits for at least two pump-overproducing strains in the presence of the drug. Therefore, pump overproduction exacerbated stress caused by defective outer membrane integrity, while the efficacy of drug resistance in efflux overproducers was enhanced by slowed translation or defects in ATP synthesis linked to the control of proton movement across the bacterial membrane.
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Affiliation(s)
- Efrat Hamami
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
| | - Wenwen Huo
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
| | - Katherine Neal
- Department of Biochemistry, Curry College, Milton, MA, USA
| | - Isabelle Neisewander
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
| | - Edward Geisinger
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
- Department of Biology, Northeastern University, Boston, MA, 02115, USA
| | - Ralph R Isberg
- Department of Molecular Biology and Microbiology, Tufts University School of Medicine, 150 Harrison Ave., Boston, MA 02111, USA
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4
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Nazli A, Qiu J, Tang Z, He Y. Recent Advances and Techniques for Identifying Novel Antibacterial Targets. Curr Med Chem 2024; 31:464-501. [PMID: 36734893 DOI: 10.2174/0929867330666230123143458] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2022] [Revised: 10/30/2022] [Accepted: 11/11/2022] [Indexed: 02/04/2023]
Abstract
BACKGROUND With the emergence of drug-resistant bacteria, the development of new antibiotics is urgently required. Target-based drug discovery is the most frequently employed approach for the drug development process. However, traditional drug target identification techniques are costly and time-consuming. As research continues, innovative approaches for antibacterial target identification have been developed which enabled us to discover drug targets more easily and quickly. METHODS In this review, methods for finding drug targets from omics databases have been discussed in detail including principles, procedures, advantages, and potential limitations. The role of phage-driven and bacterial cytological profiling approaches is also discussed. Moreover, current article demonstrates the advancements being made in the establishment of computational tools, machine learning algorithms, and databases for antibacterial target identification. RESULTS Bacterial drug targets successfully identified by employing these aforementioned techniques are described as well. CONCLUSION The goal of this review is to attract the interest of synthetic chemists, biologists, and computational researchers to discuss and improve these methods for easier and quicker development of new drugs.
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Affiliation(s)
- Adila Nazli
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing, 401331, P. R. China
| | - Jingyi Qiu
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, 266 Fangzheng Avenue, Chongqing, 400714, P. R. China
| | - Ziyi Tang
- Chongqing Institute of Green and Intelligent Technology, Chinese Academy of Sciences, 266 Fangzheng Avenue, Chongqing, 400714, P. R. China
| | - Yun He
- Chongqing Key Laboratory of Natural Product Synthesis and Drug Research, School of Pharmaceutical Sciences, Chongqing University, Chongqing, 401331, P. R. China
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5
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Sharma G, Zee PC, Zea L, Curtis PD. Whole genome-scale assessment of gene fitness of Novosphingobium aromaticavorans during spaceflight. BMC Genomics 2023; 24:782. [PMID: 38102595 PMCID: PMC10725011 DOI: 10.1186/s12864-023-09799-z] [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: 08/11/2023] [Accepted: 11/10/2023] [Indexed: 12/17/2023] Open
Abstract
In microgravity, bacteria undergo intriguing physiological adaptations. There have been few attempts to assess global bacterial physiological responses to microgravity, with most studies only focusing on a handful of individual systems. This study assessed the fitness of each gene in the genome of the aromatic compound-degrading Alphaproteobacterium Novosphingobium aromaticavorans during growth in spaceflight. This was accomplished using Comparative TnSeq, which involves culturing the same saturating transposon mutagenized library under two different conditions. To assess gene fitness, a novel comparative TnSeq analytical tool was developed, named TnDivA, that is particularly useful in leveraging biological replicates. In this approach, transposon diversity is represented numerically using a modified Shannon diversity index, which was then converted into effective transposon density. This transformation accounts for variability in read distribution between samples, such as cases where reads were dominated by only a few transposon inserts. Effective density values were analyzed using multiple statistical methods, including log2-fold change, least-squares regression analysis, and Welch's t-test. The results obtained across applied statistical methods show a difference in the number of significant genes identified. However, the functional categories of genes important to growth in microgravity showed similar patterns. Lipid metabolism and transport, energy production, transcription, translation, and secondary metabolite biosynthesis and transport were shown to have high fitness during spaceflight. This suggests that core metabolic processes, including lipid and secondary metabolism, play an important role adapting to stress and promoting growth in microgravity.
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Affiliation(s)
- Gayatri Sharma
- Department of Biology, University of Mississippi, 402 Shoemaker Hall, University, MS, 38677, USA
| | - Peter C Zee
- Department of Biology, University of Mississippi, 402 Shoemaker Hall, University, MS, 38677, USA
| | - Luis Zea
- Aerospace Engineering Sciences, University of Colorado Boulder, Boulder, CO, 80303, USA
| | - Patrick D Curtis
- Department of Biology, University of Mississippi, 402 Shoemaker Hall, University, MS, 38677, USA.
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Fiebig A, Schnizlein MK, Pena-Rivera S, Trigodet F, Dubey AA, Hennessy M, Basu A, Pott S, Dalal S, Rubin D, Sogin ML, Murat Eren A, Chang EB, Crosson S. Bile acid fitness determinants of a Bacteroides fragilis isolate from a human pouchitis patient. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.05.11.540287. [PMID: 37214927 PMCID: PMC10197588 DOI: 10.1101/2023.05.11.540287] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
Bacteroides fragilis comprises 1-5% of the gut microbiota in healthy humans but can expand to >50% of the population in ulcerative colitis (UC) patients experiencing inflammation. The mechanisms underlying such microbial blooms are poorly understood, but the gut of UC patients has physicochemical features that differ from healthy patients and likely impact microbial physiology. For example, levels of the secondary bile acid deoxycholate (DC) are highly reduced in the ileoanal J-pouch of UC colectomy patients. We isolated a B. fragilis strain from a UC patient with pouch inflammation (i.e. pouchitis) and developed it as a genetic model system to identify genes and pathways that are regulated by DC and that impact B. fragilis fitness in DC and crude bile. Treatment of B. fragilis with a physiologically relevant concentration of DC reduced cell growth and remodeled transcription of one-quarter of the genome. DC strongly induced expression of chaperones and select transcriptional regulators and efflux systems and downregulated protein synthesis genes. Using a barcoded collection of ≈50,000 unique insertional mutants, we further defined B. fragilis genes that contribute to fitness in media containing DC or crude bile. Genes impacting cell envelope functions including cardiolipin synthesis, cell surface glycosylation, and systems implicated in sodium-dependent bioenergetics were major bile acid fitness factors. As expected, there was limited overlap between transcriptionally regulated genes and genes that impacted fitness in bile when disrupted. Our study provides a genome-scale view of a B. fragilis bile response and genetic determinants of its fitness in DC and crude bile.
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Affiliation(s)
- Aretha Fiebig
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Matthew K. Schnizlein
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Selymar Pena-Rivera
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Florian Trigodet
- Department of Medicine, University of Chicago, Chicago, IL, USA
- Helmholtz Institute for Functional Marine Biodiversity, University of Oldenburg, Oldenburg, Germany
| | - Abhishek Anil Dubey
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Miette Hennessy
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
| | - Anindita Basu
- Department of Medicine, University of Chicago, Chicago, IL, USA
| | - Sebastian Pott
- Department of Medicine, University of Chicago, Chicago, IL, USA
| | - Sushila Dalal
- Department of Medicine, University of Chicago, Chicago, IL, USA
| | - David Rubin
- Department of Medicine, University of Chicago, Chicago, IL, USA
| | | | - A. Murat Eren
- Department of Medicine, University of Chicago, Chicago, IL, USA
- Helmholtz Institute for Functional Marine Biodiversity, University of Oldenburg, Oldenburg, Germany
| | - Eugene B. Chang
- Department of Medicine, University of Chicago, Chicago, IL, USA
| | - Sean Crosson
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI, USA
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7
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Matern WM, Harris HT, Danchik C, McDonald M, Patel G, Srivastava A, Ioerger TR, Bader JS, Karakousis PC. Functional Whole Genome Screen of Nutrient-Starved Mycobacterium tuberculosis Identifies Genes Involved in Rifampin Tolerance. Microorganisms 2023; 11:2269. [PMID: 37764112 PMCID: PMC10534295 DOI: 10.3390/microorganisms11092269] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2023] [Revised: 09/05/2023] [Accepted: 09/07/2023] [Indexed: 09/29/2023] Open
Abstract
Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), poses a global health challenge and is responsible for over a million deaths each year. Current treatment is lengthy and complex, and new, abbreviated regimens are urgently needed. Mtb adapts to nutrient starvation, a condition experienced during host infection, by shifting its metabolism and becoming tolerant to the killing activity of bactericidal antibiotics. An improved understanding of the mechanisms mediating antibiotic tolerance in Mtb can serve as the basis for developing more effective therapies. We performed a forward genetic screen to identify candidate Mtb genes involved in tolerance to the two key first-line antibiotics, rifampin and isoniazid, under nutrient-rich and nutrient-starved conditions. In nutrient-rich conditions, we found 220 mutants with differential antibiotic susceptibility (218 in the rifampin screen and 2 in the isoniazid screen). Following Mtb adaptation to nutrient starvation, 82 mutants showed differential antibiotic susceptibility (80 in the rifampin screen and 2 in the isoniazid screen). Using targeted mutagenesis, we validated the rifampin-hypersusceptible phenotype under nutrient starvation in Mtb mutants lacking the following genes: ercc3, moeA1, rv0049, and rv2179c. These findings shed light on potential therapeutic targets, which could help shorten the duration and complexity of antitubercular regimens.
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Affiliation(s)
- William M. Matern
- Department of Biomedical Engineering, Institute for Computational Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (W.M.M.)
- Center for Systems Approaches to Infectious Diseases (C-SAID), School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (H.T.H.)
- Tuberculosis Research Advancement Center, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Harley T. Harris
- Center for Systems Approaches to Infectious Diseases (C-SAID), School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (H.T.H.)
- Tuberculosis Research Advancement Center, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Carina Danchik
- Center for Systems Approaches to Infectious Diseases (C-SAID), School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (H.T.H.)
- Tuberculosis Research Advancement Center, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Marissa McDonald
- Center for Systems Approaches to Infectious Diseases (C-SAID), School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (H.T.H.)
- Tuberculosis Research Advancement Center, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Gopi Patel
- Center for Systems Approaches to Infectious Diseases (C-SAID), School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (H.T.H.)
- Tuberculosis Research Advancement Center, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
| | - Aashish Srivastava
- Department of Biochemistry and Biophysics, Texas A&M University, College Station, TX 77843, USA;
| | - Thomas R. Ioerger
- Department of Computer Science and Engineering, Texas A&M University, College Station, TX 77843, USA
| | - Joel S. Bader
- Department of Biomedical Engineering, Institute for Computational Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (W.M.M.)
- Center for Systems Approaches to Infectious Diseases (C-SAID), School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (H.T.H.)
| | - Petros C. Karakousis
- Center for Systems Approaches to Infectious Diseases (C-SAID), School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA; (H.T.H.)
- Tuberculosis Research Advancement Center, Department of Medicine, School of Medicine, Johns Hopkins University, Baltimore, MD 21205, USA
- Department of International Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
- Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Baltimore, MD 21205, USA
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8
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Matern WM, Harris HT, Danchik C, McDonald M, Patel G, Srivastava A, Ioerger TR, Bader JS, Karakousis PC. Functional whole genome screen of nutrient-starved Mycobacterium tuberculosis identifies genes involved in antibiotic tolerance. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2023:2023.04.12.536593. [PMID: 37090629 PMCID: PMC10120713 DOI: 10.1101/2023.04.12.536593] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 04/25/2023]
Abstract
Mycobacterium tuberculosis ( Mtb ), the causative agent of tuberculosis (TB), poses a global health challenge and is responsible for over a million deaths each year. Current treatment is lengthy and complex, and new, abbreviated regimens are urgently needed. Mtb adapts to nutrient starvation, a condition experienced during host infection, by shifting its metabolism and becoming tolerant to the killing activity of bactericidal antibiotics. An improved understanding of the mechanisms mediating antibiotic tolerance in Mtb can serve as the basis for developing more effective therapies. We performed a forward genetic screen to identify candidate Mtb genes involved in tolerance to the two key first-line antibiotics, rifampin and isoniazid, under nutrient-rich and nutrient-starved conditions. In nutrient-rich conditions, we found 220 mutants with differential antibiotic susceptibility (218 in the rifampin screen and 2 in the isoniazid screen). Following Mtb adaptation to nutrient starvation, 82 mutants showed differential antibiotic susceptibility (80 in the rifampin screen and 2 in the isoniazid screen). Using targeted mutagenesis, we validated the rifampin-hypersusceptible phenotype under nutrient starvation in Mtb mutants lacking the following genes: ercc3 , moeA1 , rv0049 , and rv2179c . These findings shed light on potential therapeutic targets, which could help shorten the duration and complexity of antitubercular regimens. Importance Treatment of Mtb infection requires a long course of combination antibiotics, likely due to subpopulations of tolerant bacteria exhibiting decreased susceptibility to antibiotics. Identifying and characterizing the genetic pathways involved in antibiotic tolerance is expected to yield therapeutic targets for the development of novel TB treatment-shortening regimens.
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9
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Harten T, Nimzyk R, Gawlick VEA, Reinhold-Hurek B. Elucidation of Essential Genes and Mutant Fitness during Adaptation toward Nitrogen Fixation Conditions in the Endophyte Azoarcus olearius BH72 Revealed by Tn-Seq. Microbiol Spectr 2022; 10:e0216222. [PMID: 36416558 PMCID: PMC9769520 DOI: 10.1128/spectrum.02162-22] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2022] [Accepted: 11/05/2022] [Indexed: 11/24/2022] Open
Abstract
Azoarcus olearius BH72 is a diazotrophic model endophyte that contributes fixed nitrogen to its host plant, Kallar grass, and expresses nitrogenase genes endophytically. Despite extensive studies on biological nitrogen fixation (BNF) of diazotrophic endophytes, little is known about global genetic players involved in survival under respective physiological conditions. Here, we report a global genomic screen for putatively essential genes of A. olearius employing Tn5 transposon mutagenesis with a modified transposon combined with high-throughput sequencing (Tn-Seq). A large Tn5 master library of ~6 × 105 insertion mutants of strain BH72 was obtained. Next-generation sequencing identified 183,437 unique insertion sites into the 4,376,040-bp genome, displaying one insertion every 24 bp on average. Applying stringent criteria, we describe 616 genes as putatively essential for growth on rich medium. COG (Clusters of Orthologous Groups) assignment of the 564 identified protein-coding genes revealed enrichment of genes related to core cellular functions and cell viability. To mimic gradual adaptations toward BNF conditions, the Tn5 mutant library was grown aerobically in synthetic medium or microaerobically on either combined or atmospheric nitrogen. Enrichment and depletion analysis of Tn5 mutants not only demonstrated the role of BNF- and metabolism-related proteins but also revealed that, strikingly, many genes relevant for plant-microbe interactions decrease bacterial competitiveness in pure culture, such type IV pilus- and bacterial envelope-associated genes. IMPORTANCE A constantly growing world population and the daunting challenge of climate change demand new strategies in agricultural crop production. Intensive usage of chemical fertilizers, overloading the world's fields with organic input, threaten terrestrial and marine ecosystems as well as human health. Long overlooked, the beneficial interaction of endophytic bacteria and grasses has attracted ever-growing interest in research in the last decade. Capable of biological nitrogen fixation, diazotrophic endophytes not only provide a valuable source of combined nitrogen but also are known for diverse plant growth-promoting effects, thereby contributing to plant productivity. Elucidation of an essential gene set for a prominent model endophyte such as A. olearius BH72 provides us with powerful insights into its basic lifestyle. Knowledge about genes detrimental or advantageous under defined physiological conditions may point out a way of manipulating key steps in the bacterium's lifestyle and plant interaction toward a more sustainable agriculture.
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Affiliation(s)
- Theresa Harten
- University of Bremen, Faculty of Biology and Chemistry, CBIB Center for Biomolecular Interactions, Department of Microbe-Plant Interactions, Bremen, Germany
| | - Rolf Nimzyk
- University of Bremen, Faculty of Biology and Chemistry, CBIB Center for Biomolecular Interactions, Department of Microbe-Plant Interactions, Bremen, Germany
- University of Bremen, Faculty of Biology and Chemistry, CBIB Center for Biomolecular Interactions, Nucleic Acid Analysis Facility (NAA), Bremen, Germany
| | - Vivian E. A. Gawlick
- University of Bremen, Faculty of Biology and Chemistry, CBIB Center for Biomolecular Interactions, Department of Microbe-Plant Interactions, Bremen, Germany
| | - Barbara Reinhold-Hurek
- University of Bremen, Faculty of Biology and Chemistry, CBIB Center for Biomolecular Interactions, Department of Microbe-Plant Interactions, Bremen, Germany
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10
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Bythrow GV, Farhat MF, Levendosky K, Mohandas P, Germain GA, Yoo B, Quadri LEN. Mycobacterium abscessus Mutants with a Compromised Functional Link between the Type VII ESX-3 System and an Iron Uptake Mechanism Reliant on an Unusual Mycobactin Siderophore. Pathogens 2022; 11:pathogens11090953. [PMID: 36145386 PMCID: PMC9505556 DOI: 10.3390/pathogens11090953] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 08/12/2022] [Accepted: 08/18/2022] [Indexed: 11/28/2022] Open
Abstract
The opportunistic pathogen Mycobacterium abscessus subsp. abscessus (Mab) has become an emerging public health threat due to the increasing number of Mab-associated chronic pulmonary disease cases. Treatment requires multiple drug courses and is often combined with surgical resection. Cure rates are only ~50% due to treatment failure and comorbidities. Deeper understanding of the biology of Mab is required to illuminate potential avenues for the development of better therapeutics against Mab infections. The ESX-3 type VII protein secretion system of Mab has an important role in host inflammatory and pathological responses during infection. In this work, we demonstrate a functional link between ESX-3 and an iron uptake system based on an unusual mycobactin-type siderophore (designated MBT Ab) and exploit this link to implement a large screen for transposon mutants with an impaired ESX-3. Most mutants we identified carry insertions in genes encoding predicted ESX-3 secretion machinery components or potential ESX-3 substrates. The mutants overproduce MBT Ab, a trait consistent with an iron uptake defect. Our characterization of MBT Ab revealed structural features reminiscent of nocardial mycobactin-like compounds with cytotoxicity. This finding raises the possibility that MBT Ab may play roles in pathogenesis unlinked to iron homeostasis. The mutants generated herein will facilitate research to better understand the role of ESX-3 and its interplay with the siderophore system.
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Affiliation(s)
- Glennon V. Bythrow
- Department of Biology, Brooklyn College, City University of New York, 2900 Bedford Avenue, Brooklyn, NY 11210, USA
- Biology Program, Graduate Center, City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
| | - Manal F. Farhat
- Department of Biology, Brooklyn College, City University of New York, 2900 Bedford Avenue, Brooklyn, NY 11210, USA
- Biology Program, Graduate Center, City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
| | - Keith Levendosky
- Department of Biology, Brooklyn College, City University of New York, 2900 Bedford Avenue, Brooklyn, NY 11210, USA
- Biology Program, Graduate Center, City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
| | - Poornima Mohandas
- Department of Biology, Brooklyn College, City University of New York, 2900 Bedford Avenue, Brooklyn, NY 11210, USA
- Biology Program, Graduate Center, City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
| | - Gabrielle A. Germain
- Department of Biology, Brooklyn College, City University of New York, 2900 Bedford Avenue, Brooklyn, NY 11210, USA
- Biology Program, Graduate Center, City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
| | - Barney Yoo
- Department of Chemistry, Hunter College, City University of New York, 695 Park Avenue, New York, NY 10065, USA
| | - Luis E. N. Quadri
- Department of Biology, Brooklyn College, City University of New York, 2900 Bedford Avenue, Brooklyn, NY 11210, USA
- Biology Program, Graduate Center, City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
- Biochemistry Program, Graduate Center, City University of New York, 365 Fifth Avenue, New York, NY 10016, USA
- Correspondence:
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11
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Sarsani V, Aldikacti B, He S, Zeinert R, Chien P, Flaherty P. Model-based identification of conditionally-essential genes from transposon-insertion sequencing data. PLoS Comput Biol 2022; 18:e1009273. [PMID: 35255084 PMCID: PMC8929702 DOI: 10.1371/journal.pcbi.1009273] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Revised: 03/17/2022] [Accepted: 02/09/2022] [Indexed: 12/13/2022] Open
Abstract
The understanding of bacterial gene function has been greatly enhanced by recent advancements in the deep sequencing of microbial genomes. Transposon insertion sequencing methods combines next-generation sequencing techniques with transposon mutagenesis for the exploration of the essentiality of genes under different environmental conditions. We propose a model-based method that uses regularized negative binomial regression to estimate the change in transposon insertions attributable to gene-environment changes in this genetic interaction study without transformations or uniform normalization. An empirical Bayes model for estimating the local false discovery rate combines unique and total count information to test for genes that show a statistically significant change in transposon counts. When applied to RB-TnSeq (randomized barcode transposon sequencing) and Tn-seq (transposon sequencing) libraries made in strains of Caulobacter crescentus using both total and unique count data the model was able to identify a set of conditionally beneficial or conditionally detrimental genes for each target condition that shed light on their functions and roles during various stress conditions.
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Affiliation(s)
- Vishal Sarsani
- Department of Mathematics and Statistics, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America
| | - Berent Aldikacti
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America
| | - Shai He
- Department of Mathematics and Statistics, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America
| | - Rilee Zeinert
- Division of Molecular and Cellular Biology, Eunice Kennedy Shriver National Institute of Child Health and Human Development, Bethesda, Maryland, United States of America
| | - Peter Chien
- Department of Biochemistry and Molecular Biology, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America
| | - Patrick Flaherty
- Department of Mathematics and Statistics, University of Massachusetts Amherst, Amherst, Massachusetts, United States of America
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12
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Rahman ASMZ, Timmerman L, Gallardo F, Cardona ST. Identification of putative essential protein domains from high-density transposon insertion sequencing. Sci Rep 2022; 12:962. [PMID: 35046497 PMCID: PMC8770471 DOI: 10.1038/s41598-022-05028-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2021] [Accepted: 12/29/2021] [Indexed: 12/24/2022] Open
Abstract
A first clue to gene function can be obtained by examining whether a gene is required for life in certain standard conditions, that is, whether a gene is essential. In bacteria, essential genes are usually identified by high-density transposon mutagenesis followed by sequencing of insertion sites (Tn-seq). These studies assign the term "essential" to whole genes rather than the protein domain sequences that encode the essential functions. However, genes can code for multiple protein domains that evolve their functions independently. Therefore, when essential genes code for more than one protein domain, only one of them could be essential. In this study, we defined this subset of genes as "essential domain-containing" (EDC) genes. Using a Tn-seq data set built-in Burkholderia cenocepacia K56-2, we developed an in silico pipeline to identify EDC genes and the essential protein domains they encode. We found forty candidate EDC genes and demonstrated growth defect phenotypes using CRISPR interference (CRISPRi). This analysis included two knockdowns of genes encoding the protein domains of unknown function DUF2213 and DUF4148. These putative essential domains are conserved in more than two hundred bacterial species, including human and plant pathogens. Together, our study suggests that essentiality should be assigned to individual protein domains rather than genes, contributing to a first functional characterization of protein domains of unknown function.
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Affiliation(s)
| | - Lukas Timmerman
- Department of Computer Science, University of Manitoba, Winnipeg, MB, Canada
| | - Flyn Gallardo
- Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada
| | - Silvia T Cardona
- Department of Microbiology, University of Manitoba, Winnipeg, MB, Canada.
- Department of Medical Microbiology and Infectious Diseases, University of Manitoba, Winnipeg, Canada.
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13
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Abstract
TnSeq, or sequencing of transposon insertion libraries, has proven to be a valuable method for probing the functions of genes in a wide range of bacteria. TnSeq has found many applications for studying genes involved in core functions (such as cell division or metabolism), stress response, virulence, etc., as well as to identify potential drug targets. Two of the most commonly used transposons in practice are Himar1, which inserts randomly at TA dinucleotides, and Tn5, which can insert more broadly throughout the genome. These insertions cause putative gene function disruption, and clones with insertions in genes that cannot tolerate disruption (in a given condition) are eliminated from the population. Deep sequencing can be used to efficiently profile the surviving members, with insertions in genes that can be inferred to be non-essential. Data from TnSeq experiments (i.e. transposon insertion counts at specific genomic locations) is inherently noisy, making rigorous statistical analysis (e.g. quantifying significance) challenging. In this chapter, we describe Transit, a Python-based software package for analyzing TnSeq data that combines a variety of data processing tools, quality assessment methods, and analytical algorithms for identifying essential (or conditionally essential) genes.
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Affiliation(s)
- Thomas R Ioerger
- Department of Computer Science, Texas A&M University, College Station, TX, USA.
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14
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Li Y, Jiang B, Dai W. A large-scale whole-genome sequencing analysis reveals false positives of bacterial essential genes. Appl Microbiol Biotechnol 2021; 106:341-347. [PMID: 34889987 DOI: 10.1007/s00253-021-11702-3] [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: 09/16/2021] [Revised: 11/05/2021] [Accepted: 11/15/2021] [Indexed: 11/26/2022]
Abstract
Essential genes are crucial for bacterial viability and represent attractive targets for novel anti-pathogen drug discovery. However, essential genes determined by the transposon insertion sequencing (Tn-seq) approach often contain many false positives. We hypothesized that some of those false positives are genes that are actually deleted from the genome, so they do not present any transposon insertion in the course of Tn-seq analysis. Based on this assumption, we performed a large-scale whole-genome sequencing analysis for the bacterium of interest. Our analysis revealed that some "essential genes" are indeed removed from the analyzed bacterial genomes. Since these genes were kicked out by bacteria, they should not be defined as essential. Our work showed that gene deletion is one of the false positive sources of essentiality determination, which is apparently underestimated in previous studies. We suggest subtracting the genome backgrounds before the evaluation of Tn-seq, and created a list of false positive gene essentiality as a reference for the downstream application. KEY POINTS: • Discovery of false positives of essential genes defined previously through the analyses of a large scale of whole-genome sequencing data • These false positives are the results of gene deletions in the studied genomes • Sequencing the target genome before Tn-seq analysis is of importance while some studies neglected it.
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Affiliation(s)
- Yuanhao Li
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510006, China
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Center, South China Agricultural University, Guangzhou, 510642, China
| | - Bo Jiang
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510006, China
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Center, South China Agricultural University, Guangzhou, 510642, China
| | - Weijun Dai
- Guangdong Laboratory for Lingnan Modern Agriculture, Guangzhou, 510006, China.
- Guangdong Province Key Laboratory of Microbial Signals and Disease Control, Integrative Microbiology Research Center, South China Agricultural University, Guangzhou, 510642, China.
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15
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Immanuel SRC, Arrieta-Ortiz ML, Ruiz RA, Pan M, Lopez Garcia de Lomana A, Peterson EJR, Baliga NS. Quantitative prediction of conditional vulnerabilities in regulatory and metabolic networks using PRIME. NPJ Syst Biol Appl 2021; 7:43. [PMID: 34873198 PMCID: PMC8648758 DOI: 10.1038/s41540-021-00205-6] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2021] [Accepted: 11/02/2021] [Indexed: 12/04/2022] Open
Abstract
The ability of Mycobacterium tuberculosis (Mtb) to adopt heterogeneous physiological states underlies its success in evading the immune system and tolerating antibiotic killing. Drug tolerant phenotypes are a major reason why the tuberculosis (TB) mortality rate is so high, with over 1.8 million deaths annually. To develop new TB therapeutics that better treat the infection (faster and more completely), a systems-level approach is needed to reveal the complexity of network-based adaptations of Mtb. Here, we report a new predictive model called PRIME (Phenotype of Regulatory influences Integrated with Metabolism and Environment) to uncover environment-specific vulnerabilities within the regulatory and metabolic networks of Mtb. Through extensive performance evaluations using genome-wide fitness screens, we demonstrate that PRIME makes mechanistically accurate predictions of context-specific vulnerabilities within the integrated regulatory and metabolic networks of Mtb, accurately rank-ordering targets for potentiating treatment with frontline drugs.
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Affiliation(s)
| | | | - Rene A Ruiz
- Institute for Systems Biology, Seattle, WA, USA
| | - Min Pan
- Institute for Systems Biology, Seattle, WA, USA
| | - Adrian Lopez Garcia de Lomana
- Institute for Systems Biology, Seattle, WA, USA
- Center for Systems Biology, University of Iceland, Reykjavik, Iceland
| | | | - Nitin S Baliga
- Institute for Systems Biology, Seattle, WA, USA.
- Departments of Biology and Microbiology, University of Washington, Seattle, WA, USA.
- Molecular and Cellular Biology Program, University of Washington, Seattle, WA, USA.
- Lawrence Berkeley National Lab, Berkeley, CA, USA.
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16
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Choudhery S, Brown AJ, Akusobi C, Rubin EJ, Sassetti CM, Ioerger TR. Modeling Site-Specific Nucleotide Biases Affecting Himar1 Transposon Insertion Frequencies in TnSeq Data Sets. mSystems 2021; 6:e0087621. [PMID: 34665010 PMCID: PMC8525568 DOI: 10.1128/msystems.00876-21] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2021] [Accepted: 09/27/2021] [Indexed: 11/20/2022] Open
Abstract
TnSeq is a widely used methodology for determining gene essentiality, conditional fitness, and genetic interactions in bacteria. The Himar1 transposon is restricted to insertions at TA dinucleotides, but otherwise, few site-specific biases have been identified. As a result, most analytical approaches assume that insertions are expected to be randomly distributed among TA sites in nonessential regions. However, through analysis of Himar1 transposon libraries in Mycobacterium tuberculosis, we demonstrate that there are site-specific biases that affect the frequency of insertion of the Himar1 transposon at different TA sites. We use machine learning and statistical models to characterize patterns in the nucleotides surrounding TA sites that correlate with high or low insertion counts. We then develop a quantitative model based on these patterns that can be used to predict the expected counts at each TA site based on nucleotide context, which can explain up to half of the variance in insertion counts. We show that these insertion preferences exist in Himar1 TnSeq data sets from other mycobacterial and nonmycobacterial species. We present an improved method for identification of essential genes, called TTN-Fitness, that can better distinguish true biological fitness effects by comparing observed counts to expected counts based on our site-specific model of insertion preferences. Compared to previous essentiality methods, TTN-Fitness can make finer distinctions among genes whose disruption causes a fitness defect (or advantage), separating them out from the large pool of nonessentials, and is able to classify many smaller genes (with few TA sites) that were previously characterized as uncertain. IMPORTANCE When using the Himar1 transposon to create transposon insertion mutant libraries, it is known that the transposon is restricted to insertions at TA dinucleotide sites throughout the genome, and the absence of insertions is used to infer which genes are essential (or conditionally essential) in a bacterial organism. It is widely assumed that insertions in nonessential regions are otherwise random, and this assumption is used as the basis of several methods for statistical analysis of TnSeq data. In this paper, we show that the nucleotide sequence surrounding TA sites influences the magnitude of insertions, and these Himar1 insertion preferences (sequence biases) can partially explain why some sites have higher counts than others. We use this predictive model to make improved estimates of the fitness effects of genes, which help make finer distinctions of the phenotype and biological consequences of disruption of nonessential genes.
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Affiliation(s)
- Sanjeevani Choudhery
- Department of Computer Science and Engineering, Texas A&M University, College Station, Texas, USA
| | - A. Jacob Brown
- Department of Computer Science and Engineering, Texas A&M University, College Station, Texas, USA
| | - Chidiebere Akusobi
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, USA
| | - Eric J. Rubin
- Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, Massachusetts, USA
| | - Christopher M. Sassetti
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts, USA
| | - Thomas R. Ioerger
- Department of Computer Science and Engineering, Texas A&M University, College Station, Texas, USA
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17
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3D architecture and structural flexibility revealed in the subfamily of large glutamate dehydrogenases by a mycobacterial enzyme. Commun Biol 2021; 4:684. [PMID: 34083757 PMCID: PMC8175468 DOI: 10.1038/s42003-021-02222-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Accepted: 05/14/2021] [Indexed: 11/16/2022] Open
Abstract
Glutamate dehydrogenases (GDHs) are widespread metabolic enzymes that play key roles in nitrogen homeostasis. Large glutamate dehydrogenases composed of 180 kDa subunits (L-GDHs180) contain long N- and C-terminal segments flanking the catalytic core. Despite the relevance of L-GDHs180 in bacterial physiology, the lack of structural data for these enzymes has limited the progress of functional studies. Here we show that the mycobacterial L-GDH180 (mL-GDH180) adopts a quaternary structure that is radically different from that of related low molecular weight enzymes. Intersubunit contacts in mL-GDH180 involve a C-terminal domain that we propose as a new fold and a flexible N-terminal segment comprising ACT-like and PAS-type domains that could act as metabolic sensors for allosteric regulation. These findings uncover unique aspects of the structure-function relationship in the subfamily of L-GDHs. Lázaro et. al. report the first 3D structure of a large glutamate dehydrogenase (L-GDH), the one corresponding to the Mycobacterium smegmatis enzyme composed of 180 kDa subunits (mL-GDH180), obtained by X-ray crystallography and cryo-electron microscopy. This structure reveals that mL-GDH180 assembles as tetramers with the N- and C-terminal domains being involved in inter-subunit contacts and unveils unique features of the subfamily of L-GDHs.
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18
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De novo histidine biosynthesis protects Mycobacterium tuberculosis from host IFN-γ mediated histidine starvation. Commun Biol 2021; 4:410. [PMID: 33767335 PMCID: PMC7994828 DOI: 10.1038/s42003-021-01926-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2020] [Accepted: 03/01/2021] [Indexed: 01/31/2023] Open
Abstract
Intracellular pathogens including Mycobacterium tuberculosis (Mtb) have evolved with strategies to uptake amino acids from host cells to fulfil their metabolic requirements. However, Mtb also possesses de novo biosynthesis pathways for all the amino acids. This raises a pertinent question- how does Mtb meet its histidine requirements within an in vivo infection setting? Here, we present a mechanism in which the host, by up-regulating its histidine catabolizing enzymes through interferon gamma (IFN-γ) mediated signalling, exerts an immune response directed at starving the bacillus of intracellular free histidine. However, the wild-type Mtb evades this host immune response by biosynthesizing histidine de novo, whereas a histidine auxotroph fails to multiply. Notably, in an IFN-γ-/- mouse model, the auxotroph exhibits a similar extent of virulence as that of the wild-type. The results augment the current understanding of host-Mtb interactions and highlight the essentiality of Mtb histidine biosynthesis for its pathogenesis.
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19
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Le Breton Y, Belew AT, McIver KS. Protocols for Tn-seq Analyses in the Group A Streptococcus. Methods Mol Biol 2021; 2136:33-57. [PMID: 32430812 DOI: 10.1007/978-1-0716-0467-0_4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Transposon-sequencing (Tn-seq) has revolutionized forward-genetic analyses to study genotype-phenotype associations and interrogate bacterial cell physiology. The Tn-seq approach allows the en masse monitoring of highly complex mutant libraries, leveraging massive parallel DNA sequencing as a means to characterize the composition of these mutant pools on a genome-scale with unprecedented nucleotide-level high resolution. In this chapter, we present step-by-step protocols for Tn-seq analyses in the human pathogen Streptococcus pyogenes (Group A Streptococcus or GAS) using the mariner-based Krmit transposon. We detail how to generate highly complex Krmit mutant libraries in GAS and the en masse production of Krmit insertion tags for Illumina sequencing of the transposon-genome junctions for Tn-seq analyses. Most of the protocols presented here were developed and implemented using the S. pyogenes M1T1 serotype clinical isolate 5448, but they have been successfully applied to multiple GAS serotypes as well as other pathogenic Streptococci.
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Affiliation(s)
- Yoann Le Breton
- Wound Infections Department, Bacterial Diseases Branch, Walter Reed Army Institute for Research, Silver Spring, MD, USA.
| | - Ashton T Belew
- Department of Cell Biology and Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, College Park, MD, USA.,Center for Bioinformatics and Computational Biology, University of Maryland, College Park, College Park, MD, USA
| | - Kevin S McIver
- Department of Cell Biology and Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, College Park, MD, USA
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20
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Dammann AN, Chamby AB, Catomeris AJ, Davidson KM, Tettelin H, van Pijkeren JP, Gopalakrishna KP, Keith MF, Elder JL, Ratner AJ, Hooven TA. Genome-Wide fitness analysis of group B Streptococcus in human amniotic fluid reveals a transcription factor that controls multiple virulence traits. PLoS Pathog 2021; 17:e1009116. [PMID: 33684178 PMCID: PMC7971860 DOI: 10.1371/journal.ppat.1009116] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2020] [Revised: 03/18/2021] [Accepted: 02/18/2021] [Indexed: 02/06/2023] Open
Abstract
Streptococcus agalactiae (group B Streptococcus; GBS) remains a dominant cause of serious neonatal infections. One aspect of GBS that renders it particularly virulent during the perinatal period is its ability to invade the chorioamniotic membranes and persist in amniotic fluid, which is nutritionally deplete and rich in fetal immunologic factors such as antimicrobial peptides. We used next-generation sequencing of transposon-genome junctions (Tn-seq) to identify five GBS genes that promote survival in the presence of human amniotic fluid. We confirmed our Tn-seq findings using a novel CRISPR inhibition (CRISPRi) gene expression knockdown system. This analysis showed that one gene, which encodes a GntR-class transcription factor that we named MrvR, conferred a significant fitness benefit to GBS in amniotic fluid. We generated an isogenic targeted deletion of the mrvR gene, which had a growth defect in amniotic fluid relative to the wild type parent strain. The mrvR deletion strain also showed a significant biofilm defect in vitro. Subsequent in vivo studies showed that while the mutant was able to cause persistent murine vaginal colonization, pregnant mice colonized with the mrvR deletion strain did not develop preterm labor despite consistent GBS invasion of the uterus and the fetoplacental units. In contrast, pregnant mice colonized with wild type GBS consistently deliver prematurely. In a sepsis model the mrvR deletion strain showed significantly decreased lethality. In order to better understand the mechanism by which this newly identified transcription factor controls GBS virulence, we performed RNA-seq on wild type and mrvR deletion GBS strains, which revealed that the transcription factor affects expression of a wide range of genes across the GBS chromosome. Nucleotide biosynthesis and salvage pathways were highly represented among the set of differentially expressed genes, suggesting that MrvR may be involved in regulating nucleotide availability. Group B Streptococcus (GBS) is a species of Gram-positive bacteria that often colonizes the healthy adult intestinal and reproductive tracts without causing serious symptoms. During pregnancy, however, GBS can invade the pregnant uterus, where it can cause infection of the placenta, fetal membranes, and fetus—a condition known as chorioamnionitis. Chorioamnionitis is associated with serious adverse pregnancy outcomes, including stillbirth, preterm labor, and severe infection of the newborn. GBS can survive in human amniotic fluid, which is low in bacterial nutrients and contains immune molecules that limit microbial persistence, and this ability likely contributes to GBS chorioamnionitis. This study is focused on a single GBS gene that encodes a genetic regulator we called MrvR, which we show is important for GBS resistance to human amniotic fluid. Using a series of genetic techniques combined with animal models of GBS colonization and infection, we show that MrvR also plays a key role in allowing GBS to invade the bloodstream and trigger the inflammatory responses that lead to preterm labor and stillbirth. The study concludes with a survey of other GBS genes whose activity is regulated by MrvR, which seems to be an important contributor to GBS virulence.
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Affiliation(s)
- Allison N. Dammann
- Department of Pediatrics, New York University School of Medicine, New York, New York, United States of America
| | - Anna B. Chamby
- University of Vermont Larner College of Medicine, Burlington, Vermont, United States of America
| | - Andrew J. Catomeris
- Georgetown University School of Medicine, Washington, District of Columbia, United States of America
| | - Kyle M. Davidson
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Hervé Tettelin
- Department of Microbiology and Immunology, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, Maryland, United States of America
| | - Jan-Peter van Pijkeren
- Department of Food Science, University of Wisconsin, Madison, Wisconsin, United States of America
| | - Kathyayini P. Gopalakrishna
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Mary F. Keith
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Jordan L. Elder
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
| | - Adam J. Ratner
- Department of Pediatrics, New York University School of Medicine, New York, New York, United States of America
- Department of Microbiology, New York University, New York, New York, United States of America
| | - Thomas A. Hooven
- Department of Pediatrics, University of Pittsburgh School of Medicine, Pittsburgh, Pennsylvania, United States of America
- Richard King Mellon Institute for Pediatric Research, UPMC Children’s Hospital of Pittsburgh, Pittsburgh, Pennsylvania, United States of America
- * E-mail:
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21
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Transposon Insertion Sequencing in a Clinical Isolate of Legionella pneumophila Identifies Essential Genes and Determinants of Natural Transformation. J Bacteriol 2021; 203:JB.00548-20. [PMID: 33168636 PMCID: PMC7811196 DOI: 10.1128/jb.00548-20] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/02/2020] [Accepted: 11/04/2020] [Indexed: 02/07/2023] Open
Abstract
Legionella pneumophila is the etiologic agent of a severe form of nosocomial and community-acquired pneumonia in humans. The environmental life traits of L. pneumophila are essential to its ability to accidentally infect humans. Legionella pneumophila is a Gram-negative bacterium ubiquitous in freshwater environments which, if inhaled, can cause a severe pneumonia in humans. The emergence of L. pneumophila is linked to several traits selected in the environment, the acquisition of some of which involved intra- and interkingdom horizontal gene transfer events. Transposon insertion sequencing (TIS) is a powerful method to identify the genetic basis of selectable traits as well as to identify fitness determinants and essential genes, which are possible antibiotic targets. TIS has not yet been used to its full power in L. pneumophila, possibly because of the difficulty of obtaining a high-saturation transposon insertion library. Indeed, we found that isolates of sequence type 1 (ST1), which includes the commonly used laboratory strains, are poorly permissive to saturating mutagenesis by conjugation-mediated transposon delivery. In contrast, we obtained high-saturation libraries in non-ST1 clinical isolates, offering the prospect of using TIS on unaltered L. pneumophila strains. Focusing on one of them, we then used TIS to identify essential genes in L. pneumophila. We also revealed that TIS could be used to identify genes controlling vertical transmission of mobile genetic elements. We then applied TIS to identify all the genes required for L. pneumophila to develop competence and undergo natural transformation, defining the set of major and minor type IV pilins that are engaged in DNA uptake. This work paves the way for the functional exploration of the L. pneumophila genome by TIS and the identification of the genetic basis of other life traits of this species. IMPORTANCELegionella pneumophila is the etiologic agent of a severe form of nosocomial and community-acquired pneumonia in humans. The environmental life traits of L. pneumophila are essential to its ability to accidentally infect humans. A comprehensive identification of their genetic basis could be obtained through the use of transposon insertion sequencing. However, this powerful approach had not been fully implemented in L. pneumophila. Here, we describe the successful implementation of the transposon-sequencing approach in a clinical isolate of L. pneumophila. We identify essential genes, potential drug targets, and genes required for horizontal gene transfer by natural transformation. This work represents an important step toward identifying the genetic basis of the many life traits of this environmental and pathogenic species.
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22
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Identification of Zinc-Dependent Mechanisms Used by Group B Streptococcus To Overcome Calprotectin-Mediated Stress. mBio 2020; 11:mBio.02302-20. [PMID: 33173000 PMCID: PMC7667036 DOI: 10.1128/mbio.02302-20] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023] Open
Abstract
Group B Streptococcus (GBS) asymptomatically colonizes the female reproductive tract but is a common causative agent of meningitis. GBS meningitis is characterized by extensive infiltration of neutrophils carrying high concentrations of calprotectin, a metal chelator. To persist within inflammatory sites and cause invasive disease, GBS must circumvent host starvation attempts. Here, we identified global requirements for GBS survival during calprotectin challenge, including known and putative systems involved in metal ion transport. We characterized the role of zinc import in tolerating calprotectin stress in vitro and in a mouse model of infection. We observed that a global zinc uptake mutant was less virulent than the parental GBS strain and found calprotectin knockout mice to be equally susceptible to infection by wild-type (WT) and mutant strains. These findings suggest that calprotectin production at the site of infection results in a zinc-limited environment and reveals the importance of GBS metal homeostasis to invasive disease. Nutritional immunity is an elegant host mechanism used to starve invading pathogens of necessary nutrient metals. Calprotectin, a metal-binding protein, is produced abundantly by neutrophils and is found in high concentrations within inflammatory sites during infection. Group B Streptococcus (GBS) colonizes the gastrointestinal and female reproductive tracts and is commonly associated with severe invasive infections in newborns such as pneumonia, sepsis, and meningitis. Although GBS infections induce robust neutrophil recruitment and inflammation, the dynamics of GBS and calprotectin interactions remain unknown. Here, we demonstrate that disease and colonizing isolate strains exhibit susceptibility to metal starvation by calprotectin. We constructed a mariner transposon (Krmit) mutant library in GBS and identified 258 genes that contribute to surviving calprotectin stress. Nearly 20% of all underrepresented mutants following treatment with calprotectin are predicted metal transporters, including known zinc systems. As calprotectin binds zinc with picomolar affinity, we investigated the contribution of GBS zinc uptake to overcoming calprotectin-imposed starvation. Quantitative reverse transcriptase PCR (qRT-PCR) revealed a significant upregulation of genes encoding zinc-binding proteins, adcA, adcAII, and lmb, following calprotectin exposure, while growth in calprotectin revealed a significant defect for a global zinc acquisition mutant (ΔadcAΔadcAIIΔlmb) compared to growth of the GBS wild-type (WT) strain. Furthermore, mice challenged with the ΔadcAΔadcAIIΔlmb mutant exhibited decreased mortality and significantly reduced bacterial burden in the brain compared to mice infected with WT GBS; this difference was abrogated in calprotectin knockout mice. Collectively, these data suggest that GBS zinc transport machinery is important for combatting zinc chelation by calprotectin and establishing invasive disease.
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Miravet-Verde S, Burgos R, Delgado J, Lluch-Senar M, Serrano L. FASTQINS and ANUBIS: two bioinformatic tools to explore facts and artifacts in transposon sequencing and essentiality studies. Nucleic Acids Res 2020; 48:e102. [PMID: 32813015 PMCID: PMC7515713 DOI: 10.1093/nar/gkaa679] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2020] [Revised: 07/28/2020] [Accepted: 08/10/2020] [Indexed: 12/15/2022] Open
Abstract
Transposon sequencing is commonly applied for identifying the minimal set of genes required for cellular life; a major challenge in fields such as evolutionary or synthetic biology. However, the scientific community has no standards at the level of processing, treatment, curation and analysis of this kind data. In addition, we lack knowledge about artifactual signals and the requirements a dataset has to satisfy to allow accurate prediction. Here, we have developed FASTQINS, a pipeline for the detection of transposon insertions, and ANUBIS, a library of functions to evaluate and correct deviating factors known and uncharacterized until now. ANUBIS implements previously defined essentiality estimate models in addition to new approaches with advantages like not requiring a training set of genes to predict general essentiality. To highlight the applicability of these tools, and provide a set of recommendations on how to analyze transposon sequencing data, we performed a comprehensive study on artifacts corrections and essentiality estimation at a 1.5-bp resolution, in the genome-reduced bacterium Mycoplasma pneumoniae. We envision FASTQINS and ANUBIS to aid in the analysis of Tn-seq procedures and lead to the development of accurate genome essentiality estimates to guide applications such as designing live vaccines or growth optimization.
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Affiliation(s)
- Samuel Miravet-Verde
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr Aiguader 88, 08003 Barcelona, Spain
| | - Raul Burgos
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr Aiguader 88, 08003 Barcelona, Spain
| | - Javier Delgado
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr Aiguader 88, 08003 Barcelona, Spain
| | - Maria Lluch-Senar
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr Aiguader 88, 08003 Barcelona, Spain.,Pulmobiotics, Dr Aiguader 88, 08003 Barcelona, Spain
| | - Luis Serrano
- Centre for Genomic Regulation (CRG), The Barcelona Institute of Science and Technology, Dr Aiguader 88, 08003 Barcelona, Spain.,Universitat Pompeu Fabra (UPF), Barcelona, Spain.,ICREA, Pg. Lluis Companys 23, 08010 Barcelona, Spain
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24
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López-Agudelo VA, Mendum TA, Laing E, Wu H, Baena A, Barrera LF, Beste DJV, Rios-Estepa R. A systematic evaluation of Mycobacterium tuberculosis Genome-Scale Metabolic Networks. PLoS Comput Biol 2020; 16:e1007533. [PMID: 32542021 PMCID: PMC7316355 DOI: 10.1371/journal.pcbi.1007533] [Citation(s) in RCA: 13] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2019] [Revised: 06/25/2020] [Accepted: 05/08/2020] [Indexed: 01/06/2023] Open
Abstract
Metabolism underpins the pathogenic strategy of the causative agent of TB, Mycobacterium tuberculosis (Mtb), and therefore metabolic pathways have recently re-emerged as attractive drug targets. A powerful approach to study Mtb metabolism as a whole, rather than just individual enzymatic components, is to use a systems biology framework, such as a Genome-Scale Metabolic Network (GSMN) that allows the dynamic interactions of all the components of metabolism to be interrogated together. Several GSMNs networks have been constructed for Mtb and used to study the complex relationship between the Mtb genotype and its phenotype. However, the utility of this approach is hampered by the existence of multiple models, each with varying properties and performances. Here we systematically evaluate eight recently published metabolic models of Mtb-H37Rv to facilitate model choice. The best performing models, sMtb2018 and iEK1011, were refined and improved for use in future studies by the TB research community.
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Affiliation(s)
- Víctor A. López-Agudelo
- Grupo de Bioprocesos, Departamento de Ingeniería Química, Universidad de Antioquia UdeA, Medellín, Colombia
- Grupo de Inmunología Celular e Inmunogenética (GICIG), Facultad de Medicina, Universidad de Antioquia UdeA, Medellín, Colombia
| | - Tom A. Mendum
- Department of Microbial Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Emma Laing
- Department of Microbial Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - HuiHai Wu
- Department of Microbial Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Andres Baena
- Grupo de Inmunología Celular e Inmunogenética (GICIG), Facultad de Medicina, Universidad de Antioquia UdeA, Medellín, Colombia
- Departamento de Microbiología y Parasitología, Facultad de Medicina, Universidad de Antioquia UdeA, Medellín, Colombia
| | - Luis F. Barrera
- Grupo de Inmunología Celular e Inmunogenética (GICIG), Facultad de Medicina, Universidad de Antioquia UdeA, Medellín, Colombia
- Instituto de Investigaciones Médicas, Facultad de Medicina, Universidad de Antioquia UdeA, Medellín, Colombia
| | - Dany J. V. Beste
- Department of Microbial Sciences, Faculty of Health and Medical Sciences, University of Surrey, Guildford, United Kingdom
| | - Rigoberto Rios-Estepa
- Grupo de Bioprocesos, Departamento de Ingeniería Química, Universidad de Antioquia UdeA, Medellín, Colombia
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25
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Selection or drift: The population biology underlying transposon insertion sequencing experiments. Comput Struct Biotechnol J 2020; 18:791-804. [PMID: 32280434 PMCID: PMC7138912 DOI: 10.1016/j.csbj.2020.03.021] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2019] [Revised: 03/06/2020] [Accepted: 03/22/2020] [Indexed: 01/23/2023] Open
Abstract
Transposon insertion sequencing methods such as Tn-seq revolutionized microbiology by allowing the identification of genomic loci that are critical for viability in a specific environment on a genome-wide scale. While powerful, transposon insertion sequencing suffers from limited reproducibility when different analysis methods are compared. From the perspective of population biology, this may be explained by changes in mutant frequency due to chance (drift) rather than differential fitness (selection). Here, we develop a mathematical model of the population biology of transposon insertion sequencing experiments, i.e. the changes in size and composition of the transposon-mutagenized population during the experiment. We use this model to investigate mutagenesis, the growth of the mutant library, and its passage through bottlenecks. Specifically, we study how these processes can lead to extinction of individual mutants depending on their fitness and the distribution of fitness effects (DFE) of the entire mutant population. We find that in typical in vitro experiments few mutants with high fitness go extinct. However, bottlenecks of a size that is common in animal infection models lead to so much random extinction that a large number of viable mutants would be misclassified. While mutants with low fitness are more likely to be lost during the experiment, mutants with intermediate fitness are expected to be much more abundant and can constitute a large proportion of detected hits, i.e. false positives. Thus, incorporating the DFEs of randomly generated mutations in the analysis may improve the reproducibility of transposon insertion experiments, especially when strong bottlenecks are encountered.
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26
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Budell WC, Germain GA, Janisch N, McKie-Krisberg Z, Jayaprakash AD, Resnick AE, Quadri LEN. Transposon mutagenesis in Mycobacterium kansasii links a small RNA gene to colony morphology and biofilm formation and identifies 9,885 intragenic insertions that do not compromise colony outgrowth. Microbiologyopen 2020; 9:e988. [PMID: 32083796 PMCID: PMC7142372 DOI: 10.1002/mbo3.988] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2019] [Revised: 12/09/2019] [Accepted: 12/10/2019] [Indexed: 01/05/2023] Open
Abstract
Mycobacterium kansasii (Mk) is a resilient opportunistic human pathogen that causes tuberculosis‐like chronic pulmonary disease and mortality stemming from comorbidities and treatment failure. The standard treatment of Mk infections requires costly, long‐term, multidrug courses with adverse side effects. The emergence of drug‐resistant isolates further complicates the already challenging drug therapy regimens and threatens to compromise the future control of Mk infections. Despite the increasingly recognized global burden of Mk infections, the biology of this opportunistic pathogen remains essentially unexplored. In particular, studies reporting gene function or generation of defined mutants are scarce. Moreover, no transposon (Tn) mutagenesis tool has been validated for use in Mk, a situation limiting the repertoire of genetic approaches available to accelerate the dissection of gene function and the generation of gene knockout mutants in this poorly characterized pathogen. In this study, we validated the functionality of a powerful Tn mutagenesis tool in Mk and used this tool in conjunction with a forward genetic screen to establish a previously unrecognized role of a conserved mycobacterial small RNA gene of unknown function in colony morphology features and biofilm formation. We also combined Tn mutagenesis with next‐generation sequencing to identify 12,071 Tn insertions that do not compromise viability in vitro. Finally, we demonstrated the susceptibility of the Galleria mellonella larva to Mk, setting the stage for further exploration of this simple and economical infection model system to the study of this pathogen.
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Affiliation(s)
- William C Budell
- Department of Biology, Brooklyn College, City University of New York, Brooklyn, NY, USA.,Biology Ph.D. Program, Graduate Center, City University of New York, New York, NY, USA
| | - Gabrielle A Germain
- Department of Biology, Brooklyn College, City University of New York, Brooklyn, NY, USA.,Biology Ph.D. Program, Graduate Center, City University of New York, New York, NY, USA
| | - Niklas Janisch
- Department of Biology, Brooklyn College, City University of New York, Brooklyn, NY, USA.,Biology Ph.D. Program, Graduate Center, City University of New York, New York, NY, USA
| | - Zaid McKie-Krisberg
- Department of Biology, Brooklyn College, City University of New York, Brooklyn, NY, USA
| | | | - Andrew E Resnick
- Department of Biology, Brooklyn College, City University of New York, Brooklyn, NY, USA
| | - Luis E N Quadri
- Department of Biology, Brooklyn College, City University of New York, Brooklyn, NY, USA.,Biology Ph.D. Program, Graduate Center, City University of New York, New York, NY, USA.,Biochemistry Ph.D. Program, Graduate Center, City University of New York, New York, NY, USA
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27
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Riggs-Shute SD, Falkinham JO, Yang Z. Construction and Use of Transposon MycoTetOP 2 for Isolation of Conditional Mycobacteria Mutants. Front Microbiol 2020; 10:3091. [PMID: 32038540 PMCID: PMC6985430 DOI: 10.3389/fmicb.2019.03091] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2019] [Accepted: 12/20/2019] [Indexed: 11/13/2022] Open
Abstract
Mycobacteria are unique in many aspects of their biology. The development of genetic tools to identify genes critical for their growth by forward genetic analysis holds great promises to advance our understanding of their cellular, physiological and biochemical processes. Here we report the development of a novel transposon, MycoTetOP 2, to aid the identification of such genes by direct transposon mutagenesis. This mariner-based transposon contains nested anhydrotetracycline (ATc)-inducible promoters to drive transcription outward from both of its ends. In addition, it includes the Escherichia coli R6Kγ origin to facilitate the identification of insertion sites. MycoTetOP 2 was placed in a shuttle plasmid with a temperature-sensitive DNA replication origin in mycobacteria. This allows propagation of mycobacteria harboring the plasmid at a permissive temperature. The resulting population of cells can then be subjected to a temperature shift to select for transposon mutants. This transposon and its delivery system, once constructed, were tested in the fast-growing model Mycobacterium smegmatis and 13 mutants with ATc-dependent growth were isolated. The identification of the insertion sites in these mutants led to nine unique genetic loci with genes critical for essential processes in both M. smegmatis and Mycobacterium tuberculosis. These results demonstrate that MycoTetOP 2 and its delivery vector provide valuable tools for the studies of mycobacteria by forward genetics.
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Affiliation(s)
- Sarah D. Riggs-Shute
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
- Department of Biology, Tidewater Community College, Portsmouth, VA, United States
| | - Joseph O. Falkinham
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
| | - Zhaomin Yang
- Department of Biological Sciences, Virginia Tech, Blacksburg, VA, United States
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28
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Statistical analysis of variability in TnSeq data across conditions using zero-inflated negative binomial regression. BMC Bioinformatics 2019; 20:603. [PMID: 31752678 PMCID: PMC6873424 DOI: 10.1186/s12859-019-3156-z] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/20/2019] [Accepted: 10/14/2019] [Indexed: 12/12/2022] Open
Abstract
Background Deep sequencing of transposon mutant libraries (or TnSeq) is a powerful method for probing essentiality of genomic loci under different environmental conditions. Various analytical methods have been described for identifying conditionally essential genes whose tolerance for insertions varies between two conditions. However, for large-scale experiments involving many conditions, a method is needed for identifying genes that exhibit significant variability in insertions across multiple conditions. Results In this paper, we introduce a novel statistical method for identifying genes with significant variability of insertion counts across multiple conditions based on Zero-Inflated Negative Binomial (ZINB) regression. Using likelihood ratio tests, we show that the ZINB distribution fits TnSeq data better than either ANOVA or a Negative Binomial (in a generalized linear model). We use ZINB regression to identify genes required for infection of M. tuberculosis H37Rv in C57BL/6 mice. We also use ZINB to perform a analysis of genes conditionally essential in H37Rv cultures exposed to multiple antibiotics. Conclusions Our results show that, not only does ZINB generally identify most of the genes found by pairwise resampling (and vastly out-performs ANOVA), but it also identifies additional genes where variability is detectable only when the magnitudes of insertion counts are treated separately from local differences in saturation, as in the ZINB model.
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29
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Lipowska J, Miks CD, Kwon K, Shuvalova L, Zheng H, Lewiński K, Cooper DR, Shabalin IG, Minor W. Pyrimidine biosynthesis in pathogens - Structures and analysis of dihydroorotases from Yersinia pestis and Vibrio cholerae. Int J Biol Macromol 2019; 136:1176-1187. [PMID: 31207330 PMCID: PMC6686667 DOI: 10.1016/j.ijbiomac.2019.05.149] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/02/2019] [Revised: 05/01/2019] [Accepted: 05/14/2019] [Indexed: 02/06/2023]
Abstract
The de novo pyrimidine biosynthesis pathway is essential for the proliferation of many pathogens. One of the pathway enzymes, dihydroorotase (DHO), catalyzes the reversible interconversion of N-carbamoyl-l-aspartate to 4,5-dihydroorotate. The substantial difference between bacterial and mammalian DHOs makes it a promising drug target for disrupting bacterial growth and thus an important candidate to evaluate as a response to antimicrobial resistance on a molecular level. Here, we present two novel three-dimensional structures of DHOs from Yersinia pestis (YpDHO), the plague-causing pathogen, and Vibrio cholerae (VcDHO), the causative agent of cholera. The evaluations of these two structures led to an analysis of all available DHO structures and their classification into known DHO types. Comparison of all the DHO active sites containing ligands that are listed in DrugBank was facilitated by a new interactive, structure-comparison and presentation platform. In addition, we examined the genetic context of characterized DHOs, which revealed characteristic patterns for different types of DHOs. We also generated a homology model for DHO from Plasmodium falciparum.
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Affiliation(s)
- Joanna Lipowska
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA; Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA 22908, USA; Faculty of Chemistry, Jagiellonian University, 30-387 Kraków, Poland
| | - Charles Dylan Miks
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA
| | - Keehwan Kwon
- Infectious Diseases Group, J. Craig Venter Institute, Rockville, MD 20850, USA
| | - Ludmilla Shuvalova
- Center for Structural Genomics of Infectious Diseases (CSGID), Chicago, IL 60611, USA
| | - Heping Zheng
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA; Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA 22908, USA
| | | | - David R Cooper
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA; Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA 22908, USA
| | - Ivan G Shabalin
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA; Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA 22908, USA.
| | - Wladek Minor
- Department of Molecular Physiology and Biological Physics, University of Virginia, Charlottesville, VA 22908, USA; Center for Structural Genomics of Infectious Diseases (CSGID), Charlottesville, VA 22908, USA.
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30
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Borgers K, Vandewalle K, Festjens N, Callewaert N. A guide to Mycobacterium mutagenesis. FEBS J 2019; 286:3757-3774. [PMID: 31419030 DOI: 10.1111/febs.15041] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2019] [Revised: 07/05/2019] [Accepted: 08/12/2019] [Indexed: 12/18/2022]
Abstract
The genus Mycobacterium includes several pathogens that cause severe disease in humans, like Mycobacterium tuberculosis (M. tb), the infectious agent causing tuberculosis. Genetic tools to engineer mycobacterial genomes, in a targeted or random fashion, have provided opportunities to investigate M. tb infection and pathogenesis. Furthermore, they have allowed the identification and validation of potential targets for the diagnosis, prevention, and treatment of tuberculosis. This review describes the various methods that are available for the generation of mutants in Mycobacterium species, focusing specifically on tools for altering slow-growing mycobacteria from the M. tb complex. Among others, it incorporates the recent new molecular biological technologies (e.g. ORBIT) to rapidly and/or genome-wide comprehensively obtain targeted mutants in mycobacteria. As such, this review can be used as a guide to select the appropriate genetic tools to generate mycobacterial mutants of interest, which can be used as tools to aid understanding of M. tb infection or to help developing TB intervention strategies.
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Affiliation(s)
- Katlyn Borgers
- VIB-UGhent Center for Medical Biotechnology, Belgium.,Department of Biochemistry and Microbiology, Ghent University, Belgium
| | - Kristof Vandewalle
- VIB-UGhent Center for Medical Biotechnology, Belgium.,Department of Biochemistry and Microbiology, Ghent University, Belgium
| | - Nele Festjens
- VIB-UGhent Center for Medical Biotechnology, Belgium.,Department of Biochemistry and Microbiology, Ghent University, Belgium
| | - Nico Callewaert
- VIB-UGhent Center for Medical Biotechnology, Belgium.,Department of Biochemistry and Microbiology, Ghent University, Belgium
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31
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Minato Y, Gohl DM, Thiede JM, Chacón JM, Harcombe WR, Maruyama F, Baughn AD. Genomewide Assessment of Mycobacterium tuberculosis Conditionally Essential Metabolic Pathways. mSystems 2019; 4:e00070-19. [PMID: 31239393 PMCID: PMC6593218 DOI: 10.1128/msystems.00070-19] [Citation(s) in RCA: 59] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2019] [Accepted: 06/07/2019] [Indexed: 11/30/2022] Open
Abstract
A better understanding of essential cellular functions in pathogenic bacteria is important for the development of more effective antimicrobial agents. We performed a comprehensive identification of essential genes in Mycobacterium tuberculosis, the major causative agent of tuberculosis, using a combination of transposon insertion sequencing (Tn-seq) and comparative genomic analysis. To identify conditionally essential genes by Tn-seq, we used media with different nutrient compositions. Although many conditional gene essentialities were affected by the presence of relevant nutrient sources, we also found that the essentiality of genes in a subset of metabolic pathways was unaffected by metabolite availability. Comparative genomic analysis revealed that not all essential genes identified by Tn-seq were fully conserved within the M. tuberculosis complex, including some existing antitubercular drug target genes. In addition, we utilized an available M. tuberculosis genome-scale metabolic model, iSM810, to predict M. tuberculosis gene essentiality in silico Comparing the sets of essential genes experimentally identified by Tn-seq to those predicted in silico reveals the capabilities and limitations of gene essentiality predictions, highlighting the complexity of M. tuberculosis essential metabolic functions. This study provides a promising platform to study essential cellular functions in M. tuberculosis IMPORTANCE Mycobacterium tuberculosis causes 10 million cases of tuberculosis (TB), resulting in over 1 million deaths each year. TB therapy is challenging because it requires a minimum of 6 months of treatment with multiple drugs. Protracted treatment times and the emergent spread of drug-resistant M. tuberculosis necessitate the identification of novel targets for drug discovery to curb this global health threat. Essential functions, defined as those indispensable for growth and/or survival, are potential targets for new antimicrobial drugs. In this study, we aimed to define gene essentialities of M. tuberculosis on a genomewide scale to comprehensively identify potential targets for drug discovery. We utilized a combination of experimental (functional genomics) and in silico approaches (comparative genomics and flux balance analysis). Our functional genomics approach identified sets of genes whose essentiality was affected by nutrient availability. Comparative genomics revealed that not all essential genes were fully conserved within the M. tuberculosis complex. Comparing sets of essential genes identified by functional genomics to those predicted by flux balance analysis highlighted gaps in current knowledge regarding M. tuberculosis metabolic capabilities. Thus, our study identifies numerous potential antitubercular drug targets and provides a comprehensive picture of the complexity of M. tuberculosis essential cellular functions.
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Affiliation(s)
- Yusuke Minato
- Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - Daryl M Gohl
- University of Minnesota Genomics Center, Minneapolis, Minnesota, USA
| | - Joshua M Thiede
- Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, Minnesota, USA
| | - Jeremy M Chacón
- Biotechnology Institute and Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota, USA
| | - William R Harcombe
- Biotechnology Institute and Department of Ecology, Evolution and Behavior, University of Minnesota, St. Paul, Minnesota, USA
| | - Fumito Maruyama
- Department of Microbiology, Graduate School of Medicine, Kyoto University, Kyoto, Japan
- The Japan Science and Technology Agency/Japan International Cooperation Agency, Science and Technology Research Partnership for Sustainable Development (JST/JICA, SATREPS), Tokyo, Japan
- Scientific and Technological Bioresource Nucleus, Universidad de La Frontera, Temuco, Chile
| | - Anthony D Baughn
- Department of Microbiology and Immunology, University of Minnesota Medical School, Minneapolis, Minnesota, USA
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32
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Cardenal-Muñoz E, Barisch C, Lefrançois LH, López-Jiménez AT, Soldati T. When Dicty Met Myco, a (Not So) Romantic Story about One Amoeba and Its Intracellular Pathogen. Front Cell Infect Microbiol 2018; 7:529. [PMID: 29376033 PMCID: PMC5767268 DOI: 10.3389/fcimb.2017.00529] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2017] [Accepted: 12/18/2017] [Indexed: 01/06/2023] Open
Abstract
In recent years, Dictyostelium discoideum has become an important model organism to study the cell biology of professional phagocytes. This amoeba not only shares many molecular features with mammalian macrophages, but most of its fundamental signal transduction pathways are conserved in humans. The broad range of existing genetic and biochemical tools, together with its suitability for cell culture and live microscopy, make D. discoideum an ideal and versatile laboratory organism. In this review, we focus on the use of D. discoideum as a phagocyte model for the study of mycobacterial infections, in particular Mycobacterium marinum. We look in detail at the intracellular cycle of M. marinum, from its uptake by D. discoideum to its active or passive egress into the extracellular medium. In addition, we describe the molecular mechanisms that both the mycobacterial invader and the amoeboid host have developed to fight against each other, and compare and contrast with those developed by mammalian phagocytes. Finally, we introduce the methods and specific tools that have been used so far to monitor the D. discoideum-M. marinum interaction.
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Affiliation(s)
- Elena Cardenal-Muñoz
- Department of Biochemistry, Sciences II, Faculty of Sciences, University of Geneva, Geneva, Switzerland
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33
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Peng C, Lin Y, Luo H, Gao F. A Comprehensive Overview of Online Resources to Identify and Predict Bacterial Essential Genes. Front Microbiol 2017; 8:2331. [PMID: 29230204 PMCID: PMC5711816 DOI: 10.3389/fmicb.2017.02331] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2017] [Accepted: 11/13/2017] [Indexed: 12/15/2022] Open
Abstract
Genes critical for the survival or reproduction of an organism in certain circumstances are classified as essential genes. Essential genes play a significant role in deciphering the survival mechanism of life. They may be greatly applied to pharmaceutics and synthetic biology. The continuous progress of experimental method for essential gene identification has accelerated the accumulation of gene essentiality data which facilitates the study of essential genes in silico. In this article, we present some available online resources related to gene essentiality, including bioinformatic software tools for transposon sequencing (Tn-seq) analysis, essential gene databases and online services to predict bacterial essential genes. We review several computational approaches that have been used to predict essential genes, and summarize the features used for gene essentiality prediction. In addition, we evaluate the available online bacterial essential gene prediction servers based on the experimentally validated essential gene sets of 30 bacteria from DEG. This article is intended to be a quick reference guide for the microbiologists interested in the essential genes.
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Affiliation(s)
- Chong Peng
- Department of Physics, School of Science, Tianjin University, Tianjin, China
| | - Yan Lin
- Department of Physics, School of Science, Tianjin University, Tianjin, China
| | - Hao Luo
- Department of Physics, School of Science, Tianjin University, Tianjin, China
| | - Feng Gao
- Department of Physics, School of Science, Tianjin University, Tianjin, China
- Key Laboratory of Systems Bioengineering (Ministry of Education), Tianjin University, Tianjin, China
- SynBio Research Platform, Collaborative Innovation Center of Chemical Science and Engineering (Tianjin), Tianjin University, Tianjin, China
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34
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Ruiz L, Bottacini F, Boinett CJ, Cain AK, O'Connell-Motherway M, Lawley TD, van Sinderen D. The essential genomic landscape of the commensal Bifidobacterium breve UCC2003. Sci Rep 2017; 7:5648. [PMID: 28717159 PMCID: PMC5514069 DOI: 10.1038/s41598-017-05795-y] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2017] [Accepted: 06/02/2017] [Indexed: 01/15/2023] Open
Abstract
Bifidobacteria are common gut commensals with purported health-promoting effects. This has encouraged scientific research into bifidobacteria, though recalcitrance to genetic manipulation and scarcity of molecular tools has hampered our knowledge on the precise molecular determinants of their health-promoting attributes and gut adaptation. To overcome this problem and facilitate functional genomic analyses in bifidobacteria, we created a large Tn5 transposon mutant library of the commensal Bifidobacterium breve UCC2003 that was further characterized by means of a Transposon Directed Insertion Sequencing (TraDIS) approach. Statistical analysis of transposon insertion distribution revealed a set of 453 genes that are essential for or markedly contribute to growth of this strain under laboratory conditions. These essential genes encode functions involved in the so-called bifid-shunt, most enzymes related to nucleotide biosynthesis and a range of housekeeping functions. Comparison to the Bifidobacterium and B. breve core genomes highlights a high degree of conservation of essential genes at the species and genus level, while comparison to essential gene datasets from other gut bacteria identified essential genes that appear specific to bifidobacteria. This work establishes a useful molecular tool for scientific discovery of bifidobacteria and identifies targets for further studies aimed at characterizing essential functions not previously examined in bifidobacteria.
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Affiliation(s)
- Lorena Ruiz
- School of Microbiology and APC Microbiome Institute, National University of Ireland, Cork, Western Road, Ireland.,Department of Nutrition, Bromatology and Food Technology, Complutense University, Avda Puerta de Hierro s/n, 28040, Madrid, Spain
| | - Francesca Bottacini
- School of Microbiology and APC Microbiome Institute, National University of Ireland, Cork, Western Road, Ireland
| | | | - Amy K Cain
- Wellcome Trust Sanger Institute, Hinxton, Cambridge, UK
| | - Mary O'Connell-Motherway
- School of Microbiology and APC Microbiome Institute, National University of Ireland, Cork, Western Road, Ireland
| | | | - Douwe van Sinderen
- School of Microbiology and APC Microbiome Institute, National University of Ireland, Cork, Western Road, Ireland.
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35
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Combining Genome-Scale Experimental and Computational Methods To Identify Essential Genes in Rhodobacter sphaeroides. mSystems 2017; 2:mSystems00015-17. [PMID: 28744485 PMCID: PMC5513736 DOI: 10.1128/msystems.00015-17] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/27/2017] [Accepted: 05/16/2017] [Indexed: 12/14/2022] Open
Abstract
Knowledge about the role of genes under a particular growth condition is required for a holistic understanding of a bacterial cell and has implications for health, agriculture, and biotechnology. We developed the Tn-seq analysis software (TSAS) package to provide a flexible and statistically rigorous workflow for the high-throughput analysis of insertion mutant libraries, advanced the knowledge of gene essentiality in R. sphaeroides, and illustrated how Tn-seq data can be used to more accurately identify genes that play important roles in metabolism and other processes that are essential for cellular survival. Rhodobacter sphaeroides is one of the best-studied alphaproteobacteria from biochemical, genetic, and genomic perspectives. To gain a better systems-level understanding of this organism, we generated a large transposon mutant library and used transposon sequencing (Tn-seq) to identify genes that are essential under several growth conditions. Using newly developed Tn-seq analysis software (TSAS), we identified 493 genes as essential for aerobic growth on a rich medium. We then used the mutant library to identify conditionally essential genes under two laboratory growth conditions, identifying 85 additional genes required for aerobic growth in a minimal medium and 31 additional genes required for photosynthetic growth. In all instances, our analyses confirmed essentiality for many known genes and identified genes not previously considered to be essential. We used the resulting Tn-seq data to refine and improve a genome-scale metabolic network model (GEM) for R. sphaeroides. Together, we demonstrate how genetic, genomic, and computational approaches can be combined to obtain a systems-level understanding of the genetic framework underlying metabolic diversity in bacterial species. IMPORTANCE Knowledge about the role of genes under a particular growth condition is required for a holistic understanding of a bacterial cell and has implications for health, agriculture, and biotechnology. We developed the Tn-seq analysis software (TSAS) package to provide a flexible and statistically rigorous workflow for the high-throughput analysis of insertion mutant libraries, advanced the knowledge of gene essentiality in R. sphaeroides, and illustrated how Tn-seq data can be used to more accurately identify genes that play important roles in metabolism and other processes that are essential for cellular survival. Author Video: An author video summary of this article is available.
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36
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Hudock TA, Foreman TW, Bandyopadhyay N, Gautam US, Veatch AV, LoBato DN, Gentry KM, Golden NA, Cavigli A, Mueller M, Hwang SA, Hunter RL, Alvarez X, Lackner AA, Bader JS, Mehra S, Kaushal D. Hypoxia Sensing and Persistence Genes Are Expressed during the Intragranulomatous Survival of Mycobacterium tuberculosis. Am J Respir Cell Mol Biol 2017; 56:637-647. [PMID: 28135421 PMCID: PMC5449490 DOI: 10.1165/rcmb.2016-0239oc] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2016] [Accepted: 12/13/2016] [Indexed: 12/22/2022] Open
Abstract
Although it is accepted that the environment within the granuloma profoundly affects Mycobacterium tuberculosis (Mtb) and infection outcome, our ability to understand Mtb gene expression in these niches has been limited. We determined intragranulomatous gene expression in human-like lung lesions derived from nonhuman primates with both active tuberculosis (ATB) and latent TB infection (LTBI). We employed a non-laser-based approach to microdissect individual lung lesions and interrogate the global transcriptome of Mtb within granulomas. Mtb genes expressed in classical granulomas with central, caseous necrosis, as well as within the caseum itself, were identified and compared with other Mtb lesions in animals with ATB (n = 7) or LTBI (n = 7). Results were validated using both an oligonucleotide approach and RT-PCR on macaque samples and by using human TB samples. We detected approximately 2,900 and 1,850 statistically significant genes in ATB and LTBI lesions, respectively (linear models for microarray analysis, Bonferroni corrected, P < 0.05). Of these genes, the expression of approximately 1,300 (ATB) and 900 (LTBI) was positively induced. We identified the induction of key regulons and compared our results to genes previously determined to be required for Mtb growth. Our results indicate pathways that Mtb uses to ensure its survival in a highly stressful environment in vivo. A large number of genes is commonly expressed in granulomas with ATB and LTBI. In addition, the enhanced expression of the dormancy survival regulon was a key feature of lesions in animals with LTBI, stressing its importance in the persistence of Mtb during the chronic phase of infection.
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Affiliation(s)
- Teresa A. Hudock
- Tulane National Primate Research Center, Covington, Louisiana
- Tulane University Health Sciences, New Orleans, Louisiana; and
| | - Taylor W. Foreman
- Tulane National Primate Research Center, Covington, Louisiana
- Tulane University Health Sciences, New Orleans, Louisiana; and
| | - Nirmalya Bandyopadhyay
- Whitaker Biomedical Engineering Institute, Whiting School of Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Uma S. Gautam
- Tulane National Primate Research Center, Covington, Louisiana
| | - Ashley V. Veatch
- Tulane National Primate Research Center, Covington, Louisiana
- Tulane University Health Sciences, New Orleans, Louisiana; and
| | - Denae N. LoBato
- Tulane National Primate Research Center, Covington, Louisiana
| | | | - Nadia A. Golden
- Tulane National Primate Research Center, Covington, Louisiana
| | - Amy Cavigli
- Tulane National Primate Research Center, Covington, Louisiana
| | | | - Shen-An Hwang
- Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, Houston, Texas
| | - Robert L. Hunter
- Department of Pathology and Laboratory Medicine, University of Texas Health Science Center, Houston, Texas
| | - Xavier Alvarez
- Tulane National Primate Research Center, Covington, Louisiana
| | - Andrew A. Lackner
- Tulane National Primate Research Center, Covington, Louisiana
- Tulane University Health Sciences, New Orleans, Louisiana; and
| | - Joel S. Bader
- Whitaker Biomedical Engineering Institute, Whiting School of Engineering, Johns Hopkins University, Baltimore, Maryland
| | - Smriti Mehra
- Department of Pathobiological Sciences, Louisiana State University School of Veterinary Medicine, Baton Rouge, Louisiana
| | - Deepak Kaushal
- Tulane National Primate Research Center, Covington, Louisiana
- Tulane University Health Sciences, New Orleans, Louisiana; and
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Majumdar G, Mbau R, Singh V, Warner DF, Dragset MS, Mukherjee R. Genome-Wide Transposon Mutagenesis in Mycobacterium tuberculosis and Mycobacterium smegmatis. Methods Mol Biol 2017; 1498:321-335. [PMID: 27709585 DOI: 10.1007/978-1-4939-6472-7_21] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/06/2023]
Abstract
TnSeq, or transposon (Tn) insertion sequencing, is a powerful method for identifying the essential-as well as conditionally essential-regions in a genome, both coding and noncoding. The advent of accessible massively parallel DNA sequencing technologies in particular has resulted in the increased use of TnSeq-based approaches to elucidate various aspects of bacterial physiology and metabolism. Moreover, the availability of detailed protocols has enabled even nonspecialist laboratories to adapt and develop TnSeq approaches to address specific research questions. In this chapter, we describe a recently modified experimental protocol used in our laboratory for TnSeq in the major human pathogen, Mycobacterium tuberculosis, as well as the related non-pathogenic mycobacterium, M. smegmatis. The method, which was developed in close consultation with pioneers in the field of mycobacterial genetics, includes the steps involved in preparing a phage stock, generating a mutant library, selection of the library under a specific experimental condition, isolation of genomic DNA from the pooled population of mutants, amplification of the sites of Tn insertion and, finally, determining the essential genomic regions by next-generation sequencing.
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Affiliation(s)
- Gaurav Majumdar
- MRC/NHLS/UCT Molecular Mycobacteriology Research Unit, DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Rendani Mbau
- MRC/NHLS/UCT Molecular Mycobacteriology Research Unit, DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Vinayak Singh
- MRC/NHLS/UCT Molecular Mycobacteriology Research Unit, DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa
| | - Digby F Warner
- MRC/NHLS/UCT Molecular Mycobacteriology Research Unit, DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
- Institute of Infectious Disease and Molecular Medicine, University of Cape Town, Cape Town, South Africa.
| | - Marte Singsås Dragset
- Centre of Molecular Inflammation Research, Department of Cancer Research and Molecular Medicine, Norwegian University of Science and Technology, Trondheim, Norway
| | - Raju Mukherjee
- MRC/NHLS/UCT Molecular Mycobacteriology Research Unit, DST/NRF Centre of Excellence for Biomedical TB Research, Department of Pathology, Faculty of Health Sciences, University of Cape Town, Cape Town, South Africa.
- Division of Biology, Indian Institute of Science Education and Research, Tirupati, India.
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38
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van Wyk N, Drancourt M, Henrissat B, Kremer L. Current perspectives on the families of glycoside hydrolases ofMycobacterium tuberculosis: their importance and prospects for assigning function to unknowns. Glycobiology 2016; 27:112-122. [DOI: 10.1093/glycob/cww099] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/25/2016] [Revised: 08/28/2016] [Accepted: 09/26/2016] [Indexed: 11/14/2022] Open
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39
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Hooven TA, Catomeris AJ, Akabas LH, Randis TM, Maskell DJ, Peters SE, Ott S, Santana-Cruz I, Tallon LJ, Tettelin H, Ratner AJ. The essential genome of Streptococcus agalactiae. BMC Genomics 2016; 17:406. [PMID: 27229469 PMCID: PMC4881062 DOI: 10.1186/s12864-016-2741-z] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2016] [Accepted: 05/14/2016] [Indexed: 12/22/2022] Open
Abstract
BACKGROUND Next-generation sequencing of transposon-genome junctions from a saturated bacterial mutant library (Tn-seq) is a powerful tool that permits genome-wide determination of the contribution of genes to fitness of the organism under a wide range of experimental conditions. We report development, testing, and results from a Tn-seq system for use in Streptococcus agalactiae (group B Streptococcus; GBS), an important cause of neonatal sepsis. METHODS Our method uses a Himar1 mini-transposon that inserts at genomic TA dinucleotide sites, delivered to GBS on a temperature-sensitive plasmid that is subsequently cured from the bacterial population. In order to establish the GBS essential genome, we performed Tn-seq on DNA collected from three independent mutant libraries-with at least 135,000 mutants per library-at serial 24 h time points after outgrowth in rich media. RESULTS After statistical analysis of transposon insertion density and distribution, we identified 13.5 % of genes as essential and 1.2 % as critical, with high levels of reproducibility. Essential and critical genes are enriched for fundamental cellular housekeeping functions, such as acyl-tRNA biosynthesis, nucleotide metabolism, and glycolysis. We further validated our system by comparing fitness assignments of homologous genes in GBS and a close bacterial relative, Streptococcus pyogenes, which demonstrated 93 % concordance. Finally, we used our fitness assignments to identify signal transduction pathway components predicted to be essential or critical in GBS. CONCLUSIONS We believe that our baseline fitness assignments will be a valuable tool for GBS researchers and that our system has the potential to reveal key pathogenesis gene networks and potential therapeutic/preventative targets.
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Affiliation(s)
- Thomas A Hooven
- Department of Pediatrics, Columbia University, New York, NY, USA
| | - Andrew J Catomeris
- Department of Pediatrics, Division of Pediatric Infectious Diseases, New York University School of Medicine, 550 First Avenue (MSB 223), New York, NY, 10016, USA
| | - Leor H Akabas
- Department of Pediatrics, Columbia University, New York, NY, USA
| | - Tara M Randis
- Department of Pediatrics, Division of Pediatric Infectious Diseases, New York University School of Medicine, 550 First Avenue (MSB 223), New York, NY, 10016, USA
| | - Duncan J Maskell
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - Sarah E Peters
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - Sandra Ott
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Ivette Santana-Cruz
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Luke J Tallon
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Hervé Tettelin
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD, USA
| | - Adam J Ratner
- Department of Pediatrics, Division of Pediatric Infectious Diseases, New York University School of Medicine, 550 First Avenue (MSB 223), New York, NY, 10016, USA. .,Department of Microbiology, New York University School of Medicine, New York, NY, USA.
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40
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Chao MC, Abel S, Davis BM, Waldor MK. The design and analysis of transposon insertion sequencing experiments. Nat Rev Microbiol 2016; 14:119-28. [PMID: 26775926 DOI: 10.1038/nrmicro.2015.7] [Citation(s) in RCA: 147] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Abstract
Transposon insertion sequencing (TIS) is a powerful approach that can be extensively applied to the genome-wide definition of loci that are required for bacterial growth under diverse conditions. However, experimental design choices and stochastic biological processes can heavily influence the results of TIS experiments and affect downstream statistical analysis. In this Opinion article, we discuss TIS experimental parameters and how these factors relate to the benefits and limitations of the various statistical frameworks that can be applied to the computational analysis of TIS data.
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Affiliation(s)
- Michael C Chao
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts 02115, USA; the Division of Infectious Disease, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA; and the Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA
| | - Sören Abel
- Department of Pharmacy, University of Tromsø, The Arctic University of Norway, 9019 Tromsø, Norway
| | - Brigid M Davis
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts 02115, USA; the Division of Infectious Disease, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA; and the Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA
| | - Matthew K Waldor
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, Massachusetts 02115, USA; the Division of Infectious Disease, Brigham and Women's Hospital, Boston, Massachusetts 02115, USA; and the Howard Hughes Medical Institute, Boston, Massachusetts 02115, USA
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41
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Wivagg CN, Wellington S, Gomez JE, Hung DT. Loss of a Class A Penicillin-Binding Protein Alters β-Lactam Susceptibilities in Mycobacterium tuberculosis. ACS Infect Dis 2016; 2:104-10. [PMID: 27624961 DOI: 10.1021/acsinfecdis.5b00119] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Recent studies have renewed interest in β-lactam antibiotics as a potential treatment for Mycobacterium tuberculosis infection. To explore the opportunities and limitations of this approach, we sought to better understand potential resistance mechanisms to β-lactam antibiotics in M. tuberculosis. We identified mutations in the penicillin-binding protein (PBP) ponA2 that were able to confer some degree of resistance to the cephalosporin subclass of β-lactams. Surprisingly, deletion of ponA2 also confers resistance, demonstrating that β-lactam resistance can spontaneously arise from PBP loss of function. We show that ponA2 mutants resistant to the cephalosporin subclass of β-lactams in fact show increased susceptibility to meropenem, a carbapenem that is known to target l,d-transpeptidases, thereby suggesting that in the absence of PonA2, an alternative mode of peptidoglycan synthesis likely becomes essential. Consistent with this hypothesis, a negative genetic selection identified the l,d-transpeptidase ldtMt2 as essential in the absence of ponA2. The mechanism of β-lactam resistance we outline is consistent with emerging models of β-lactam killing, while the investigation of ponA2 downstream and synthetic lethal genes sheds light on the mechanism of cell wall biosynthesis and the interaction between conventional PBPs and l,d-transpeptidases.
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Affiliation(s)
- Carl N. Wivagg
- Department
of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue
Louis Pasteur, Boston, Massachusetts 02115, United States
| | - Samantha Wellington
- Department
of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue
Louis Pasteur, Boston, Massachusetts 02115, United States
- Department of Molecular Biology and Center for Computational and
Integrative Biology, Massachusetts General Hospital, Richard B. Simches Research Center, 185 Cambridge Street, Seventh Floor, Boston, Massachusetts 02114, United States
| | - James E. Gomez
- Broad Institute, 415
Main Street, Cambridge, Massachusetts 02142, United States
| | - Deborah T. Hung
- Department
of Microbiology and Immunobiology, Harvard Medical School, 77 Avenue
Louis Pasteur, Boston, Massachusetts 02115, United States
- Broad Institute, 415
Main Street, Cambridge, Massachusetts 02142, United States
- Department of Molecular Biology and Center for Computational and
Integrative Biology, Massachusetts General Hospital, Richard B. Simches Research Center, 185 Cambridge Street, Seventh Floor, Boston, Massachusetts 02114, United States
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Glutamate Dehydrogenase Is Required by Mycobacterium bovis BCG for Resistance to Cellular Stress. PLoS One 2016; 11:e0147706. [PMID: 26824899 PMCID: PMC4732601 DOI: 10.1371/journal.pone.0147706] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Accepted: 01/07/2016] [Indexed: 11/19/2022] Open
Abstract
We recently reported on our success to generate deletion mutants of the genes encoding glutamate dehydrogenase (GDH) and glutamine oxoglutarate aminotransferase (GOGAT) in M. bovis BCG, despite their in vitro essentiality in M. tuberculosis. We could use these mutants to delineate the roles of GDH and GOGAT in mycobacterial nitrogen metabolism by using M. bovis BCG as a model for M. tuberculosis specifically. Here, we extended our investigation towards the involvement of GDH and GOGAT in other aspects of M. bovis BCG physiology, including the use of glutamate as a carbon source and resistance to known phagosomal stresses, as well as in survival inside macrophages. We find that gdh is indispensable for the utilization of glutamate as a major carbon source, in low pH environments and when challenged with nitric oxide. On the other hand, the gltBD mutant had increased viability under low pH conditions and was unaffected by a challenge with nitric oxide. Strikingly, GDH was required to sustain M. bovis BCG during infection of both murine RAW 264.7 and bone-marrow derived and macrophages, while GOGAT was not. We conclude that the catabolism of glutamate in slow growing mycobacteria may be a crucial function during infection of macrophage cells and demonstrate a novel requirement for M. bovis BCG GDH in the protection against acidic and nitrosative stress. These results provide strong clues on the role of GDH in intracellular survival of M. tuberculosis, in which the essentiality of the gdh gene complicates knock out studies making the study of the role of this enzyme in pathogenesis difficult.
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43
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DeJesus MA, Ioerger TR. Normalization of transposon-mutant library sequencing datasets to improve identification of conditionally essential genes. J Bioinform Comput Biol 2016; 14:1642004. [PMID: 26932272 DOI: 10.1142/s021972001642004x] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Sequencing of transposon-mutant libraries using next-generation sequencing (TnSeq) has become a popular method for determining which genes and non-coding regions are essential for growth under various conditions in bacteria. For methods that rely on quantitative comparison of counts of reads at transposon insertion sites, proper normalization of TnSeq datasets is vitally important. Real TnSeq datasets are often noisy and exhibit a significant skew that can be dominated by high counts at a small number of sites (often for non-biological reasons). If two datasets that are not appropriately normalized are compared, it might cause the artifactual appearance of Differentially Essential (DE) genes in a statistical test, constituting type I errors (false positives). In this paper, we propose a novel method for normalization of TnSeq datasets that corrects for the skew of read-count distributions by fitting them to a Beta-Geometric distribution. We show that this read-count correction procedure reduces the number of false positives when comparing replicate datasets grown under the same conditions (for which no genuine differences in essentiality are expected). We compare these results to results obtained with other normalization procedures, and show that it results in greater reduction in the number of false positives. In addition we investigate the effects of normalization on the detection of DE genes.
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Affiliation(s)
- Michael A DeJesus
- 1 Department of Computer Science, Texas A&M University, College Station, Texas 77843, USA
| | - Thomas R Ioerger
- 1 Department of Computer Science, Texas A&M University, College Station, Texas 77843, USA
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Lunardi J, Borges Martinelli LK, Raupp AS, Sacconi Nunes JE, Rostirolla DC, Saraiva Macedo Timmers LF, Villela AD, Pissinate K, Limberger J, Norberto de Souza O, Basso LA, Santos DS, Machado P. Mycobacterium tuberculosis histidinol dehydrogenase: biochemical characterization and inhibition studies. RSC Adv 2016. [DOI: 10.1039/c6ra03020c] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
We describe a series of biochemical studies on recombinantMycobacterium tuberculosisHisD (MtHisD) and the synthesis of a series of compounds which are, to the best of our knowledge, the first inhibitors ofMtHisD activity reported in the literature.
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DeJesus MA, Ambadipudi C, Baker R, Sassetti C, Ioerger TR. TRANSIT--A Software Tool for Himar1 TnSeq Analysis. PLoS Comput Biol 2015; 11:e1004401. [PMID: 26447887 PMCID: PMC4598096 DOI: 10.1371/journal.pcbi.1004401] [Citation(s) in RCA: 128] [Impact Index Per Article: 12.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2015] [Accepted: 06/10/2015] [Indexed: 02/07/2023] Open
Abstract
TnSeq has become a popular technique for determining the essentiality of genomic regions in bacterial organisms. Several methods have been developed to analyze the wealth of data that has been obtained through TnSeq experiments. We developed a tool for analyzing Himar1 TnSeq data called TRANSIT. TRANSIT provides a graphical interface to three different statistical methods for analyzing TnSeq data. These methods cover a variety of approaches capable of identifying essential genes in individual datasets as well as comparative analysis between conditions. We demonstrate the utility of this software by analyzing TnSeq datasets of M. tuberculosis grown on glycerol and cholesterol. We show that TRANSIT can be used to discover genes which have been previously implicated for growth on these carbon sources. TRANSIT is written in Python, and thus can be run on Windows, OSX and Linux platforms. The source code is distributed under the GNU GPL v3 license and can be obtained from the following GitHub repository: https://github.com/mad-lab/transit.
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Affiliation(s)
- Michael A. DeJesus
- Department of Computer Science, Texas A&M University, College Station, Texas, United States of America
- * E-mail:
| | - Chaitra Ambadipudi
- Department of Computer Science, Texas A&M University, College Station, Texas, United States of America
| | - Richard Baker
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Christopher Sassetti
- Department of Microbiology and Physiological Systems, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
| | - Thomas R. Ioerger
- Department of Computer Science, Texas A&M University, College Station, Texas, United States of America
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van der Beek SL, Le Breton Y, Ferenbach AT, Chapman RN, van Aalten DMF, Navratilova I, Boons GJ, McIver KS, van Sorge NM, Dorfmueller HC. GacA is essential for Group A Streptococcus and defines a new class of monomeric dTDP-4-dehydrorhamnose reductases (RmlD). Mol Microbiol 2015; 98:946-62. [PMID: 26278404 PMCID: PMC4832382 DOI: 10.1111/mmi.13169] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 08/13/2015] [Indexed: 12/29/2022]
Abstract
The sugar nucleotide dTDP‐L‐rhamnose is critical for the biosynthesis of the Group A Carbohydrate, the molecular signature and virulence determinant of the human pathogen Group A Streptococcus (GAS). The final step of the four‐step dTDP‐L‐rhamnose biosynthesis pathway is catalyzed by dTDP‐4‐dehydrorhamnose reductases (RmlD). RmlD from the Gram‐negative bacterium Salmonella is the only structurally characterized family member and requires metal‐dependent homo‐dimerization for enzymatic activity. Using a biochemical and structural biology approach, we demonstrate that the only RmlD homologue from GAS, previously renamed GacA, functions in a novel monomeric manner. Sequence analysis of 213 Gram‐negative and Gram‐positive RmlD homologues predicts that enzymes from all Gram‐positive species lack a dimerization motif and function as monomers. The enzymatic function of GacA was confirmed through heterologous expression of gacA in a S. mutans rmlD knockout, which restored attenuated growth and aberrant cell division. Finally, analysis of a saturated mutant GAS library using Tn‐sequencing and generation of a conditional‐expression mutant identified gacA as an essential gene for GAS. In conclusion, GacA is an essential monomeric enzyme in GAS and representative of monomeric RmlD enzymes in Gram‐positive bacteria and a subset of Gram‐negative bacteria. These results will help future screens for novel inhibitors of dTDP‐L‐rhamnose biosynthesis.
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Affiliation(s)
- Samantha L van der Beek
- University Medical Center Utrecht, Medical Microbiology, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands
| | - Yoann Le Breton
- Department of Cell Biology and Molecular Genetics, Maryland Pathogen Research Institute, University of Maryland, 3124 Biosciences Research Building, College Park, MD 20742, USA
| | - Andrew T Ferenbach
- Division of Molecular Microbiology, University of Dundee, School of Life Sciences, Dow Street, DD1 5EH, Dundee, UK
| | - Robert N Chapman
- Complex Carbohydrate Research Center, Department of Chemistry, The University of Georgia, 315 Riverbend Road, Athens, USA
| | - Daan M F van Aalten
- Division of Molecular Microbiology, University of Dundee, School of Life Sciences, Dow Street, DD1 5EH, Dundee, UK
| | - Iva Navratilova
- Division of Biological Chemistry and Drug Discovery, University of Dundee, School of Life Sciences, Dow Street, DD1 5EH, Dundee, UK
| | - Geert-Jan Boons
- Complex Carbohydrate Research Center, Department of Chemistry, The University of Georgia, 315 Riverbend Road, Athens, USA
| | - Kevin S McIver
- Department of Cell Biology and Molecular Genetics, Maryland Pathogen Research Institute, University of Maryland, 3124 Biosciences Research Building, College Park, MD 20742, USA
| | - Nina M van Sorge
- University Medical Center Utrecht, Medical Microbiology, Heidelberglaan 100, 3584 CX, Utrecht, The Netherlands
| | - Helge C Dorfmueller
- Division of Molecular Microbiology, University of Dundee, School of Life Sciences, Dow Street, DD1 5EH, Dundee, UK.,Rutherford Appleton Laboratory, Research Complex at Harwell, OX11 0FA, Didcot, UK
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Neglected Tropical Diseases in the Post-Genomic Era. Trends Genet 2015; 31:539-555. [DOI: 10.1016/j.tig.2015.06.002] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/09/2015] [Revised: 06/01/2015] [Accepted: 06/03/2015] [Indexed: 01/22/2023]
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Acetate Dissimilation and Assimilation in Mycobacterium tuberculosis Depend on Carbon Availability. J Bacteriol 2015. [PMID: 26216844 DOI: 10.1128/jb.00259-15] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
UNLABELLED Mycobacterium tuberculosis persists inside granulomas in the human lung. Analysis of the metabolic composition of granulomas from guinea pigs revealed that one of the organic acids accumulating in the course of infection is acetate (B. S. Somashekar, A. G. Amin, C. D. Rithner, J. Troudt, R. Basaraba, A. Izzo, D. C. Crick, and D. Chatterjee, J Proteome Res 10:4186-4195, 2011, doi:http://dx.doi.org/10.1021/pr2003352), which might result either from metabolism of the pathogen or might be provided by the host itself. Our studies characterize a metabolic pathway by which M. tuberculosis generates acetate in the cause of fatty acid catabolism. The acetate formation depends on the enzymatic activities of Pta and AckA. Using actyl coenzyme A (acetyl-CoA) as a substrate, acetyl-phosphate is generated and finally dephosphorylated to acetate, which is secreted into the medium. Knockout mutants lacking either the pta or ackA gene showed significantly reduced acetate production when grown on fatty acids. This effect is even more pronounced when the glyoxylate shunt is blocked, resulting in higher acetate levels released to the medium. The secretion of acetate was followed by an assimilation of the metabolite when other carbon substrates became limiting. Our data indicate that during acetate assimilation, the Pta-AckA pathway acts in concert with another enzymatic reaction, namely, the acetyl-CoA synthetase (Acs) reaction. Thus, acetate metabolism might possess a dual function, mediating an overflow reaction to release excess carbon units and resumption of acetate as a carbon substrate. IMPORTANCE During infection, host-derived lipid components present the major carbon source at the infection site. β-Oxidation of fatty acids results in the formation of acetyl-CoA. In this study, we demonstrate that consumption of fatty acids by Mycobacterium tuberculosis activates an overflow mechanism, causing the pathogen to release excess carbon intermediates as acetate. The Pta-AckA pathway mediating acetate formation proved to be reversible, enabling M. tuberculosis to reutilize the previously secreted acetate as a carbon substrate for metabolism.
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Le Breton Y, Belew AT, Valdes KM, Islam E, Curry P, Tettelin H, Shirtliff ME, El-Sayed NM, McIver KS. Essential Genes in the Core Genome of the Human Pathogen Streptococcus pyogenes. Sci Rep 2015; 5:9838. [PMID: 25996237 PMCID: PMC4440532 DOI: 10.1038/srep09838] [Citation(s) in RCA: 92] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2015] [Accepted: 03/23/2015] [Indexed: 02/01/2023] Open
Abstract
Streptococcus pyogenes (Group A Streptococcus, GAS) remains a major public health burden worldwide, infecting over 750 million people leading to over 500,000 deaths annually. GAS pathogenesis is complex, involving genetically distinct GAS strains and multiple infection sites. To overcome fastidious genetic manipulations and accelerate pathogenesis investigations in GAS, we developed a mariner-based system (Krmit) for en masse monitoring of complex mutant pools by transposon sequencing (Tn-seq). Highly saturated transposant libraries (Krmit insertions in ca. every 25 nucleotides) were generated in two distinct GAS clinical isolates, a serotype M1T1 invasive strain 5448 and a nephritogenic serotype M49 strain NZ131, and analyzed using a Bayesian statistical model to predict GAS essential genes, identifying sets of 227 and 241 of those genes in 5448 and NZ131, respectively. A large proportion of GAS essential genes corresponded to key cellular processes and metabolic pathways, and 177 were found conserved within the GAS core genome established from 20 available GAS genomes. Selected essential genes were validated using conditional-expression mutants. Finally, comparison to previous essentiality analyses in S. sanguinis and S. pneumoniae revealed significant overlaps, providing valuable insights for the development of new antimicrobials to treat infections by GAS and other pathogenic streptococci.
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Affiliation(s)
- Yoann Le Breton
- Department of Cell Biology & Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, MD USA
| | - Ashton T. Belew
- Department of Cell Biology & Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, MD USA
| | - Kayla M. Valdes
- Department of Cell Biology & Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, MD USA
| | - Emrul Islam
- Department of Cell Biology & Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, MD USA
| | - Patrick Curry
- Department of Cell Biology & Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, MD USA
| | - Hervé Tettelin
- Institute for Genome Sciences, University of Maryland School of Medicine, Baltimore, MD USA
- Department of Microbiology & Immunology, University of Maryland School of Medicine, Baltimore, MD USA
| | - Mark E. Shirtliff
- Department of Microbiology & Immunology, University of Maryland School of Medicine, Baltimore, MD USA
- Department of Microbial Pathogenesis, School of Dentistry, University of Maryland School of Medicine, Baltimore, MD USA
| | - Najib M. El-Sayed
- Department of Cell Biology & Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, MD USA
- Center for Bioinformatics and Computation Biology, University of Maryland, College Park, MD USA
| | - Kevin S. McIver
- Department of Cell Biology & Molecular Genetics and Maryland Pathogen Research Institute, University of Maryland, College Park, MD USA
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50
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Characterization of genome-wide ordered sequence-tagged Mycobacterium mutant libraries by Cartesian Pooling-Coordinate Sequencing. Nat Commun 2015; 6:7106. [PMID: 25960123 PMCID: PMC4432585 DOI: 10.1038/ncomms8106] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2014] [Accepted: 04/07/2015] [Indexed: 02/02/2023] Open
Abstract
Reverse genetics research approaches require the availability of methods to rapidly generate specific mutants. Alternatively, where these methods are lacking, the construction of pre-characterized libraries of mutants can be extremely valuable. However, this can be complex, expensive and time consuming. Here, we describe a robust, easy to implement parallel sequencing-based method (Cartesian Pooling-Coordinate Sequencing or CP-CSeq) that reports both on the identity as well as on the location of sequence-tagged biological entities in well-plate archived clone collections. We demonstrate this approach using a transposon insertion mutant library of the Mycobacterium bovis BCG vaccine strain, providing the largest resource of mutants in any strain of the M. tuberculosis complex. The method is applicable to any entity for which sequence-tagged identification is possible. The generation of characterized panels of specific mutants is an essential but time-consuming step of reverse genetic studies. Here Vandewalle et al. describe CP-CSeq, an easy to implement parallel sequencing method for rapid library construction.
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