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The Landscape of Phenotypic and Transcriptional Responses to Ciprofloxacin in Acinetobacter baumannii: Acquired Resistance Alleles Modulate Drug-Induced SOS Response and Prophage Replication. mBio 2019; 10:mBio.01127-19. [PMID: 31186328 PMCID: PMC6561030 DOI: 10.1128/mbio.01127-19] [Citation(s) in RCA: 21] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023] Open
Abstract
The emergence of fluoroquinolone resistance in nosocomial pathogens has restricted the clinical efficacy of this antibiotic class. In Acinetobacter baumannii, the majority of clinical isolates now show high-level resistance due to mutations in gyrA (DNA gyrase) and parC (topoisomerase IV [topo IV]). To investigate the molecular basis for fluoroquinolone resistance, an exhaustive mutation analysis was performed in both drug-sensitive and -resistant strains to identify loci that alter ciprofloxacin sensitivity. To this end, parallel fitness tests of over 60,000 unique insertion mutations were performed in strains with various alleles in genes encoding the drug targets. The spectra of mutations that altered drug sensitivity were found to be similar in the drug-sensitive and gyrA parC double-mutant backgrounds, having resistance alleles in both genes. In contrast, the introduction of a single gyrA resistance allele, resulting in preferential poisoning of topo IV by ciprofloxacin, led to extreme alterations in the insertion mutation fitness landscape. The distinguishing feature of preferential topo IV poisoning was enhanced induction of DNA synthesis in the region of two endogenous prophages, with DNA synthesis associated with excision and circularization of the phages. Induction of the selective DNA synthesis in the gyrA background was also linked to heightened prophage gene transcription and enhanced activation of the mutagenic SOS response relative to that observed in either the wild-type (WT) or gyrA parC double mutant. Therefore, the accumulation of mutations that result in the stepwise evolution of high ciprofloxacin resistance is tightly connected to modulation of the SOS response and endogenous prophage DNA synthesis.IMPORTANCE Fluoroquinolones have been extremely successful antibiotics due to their ability to target multiple bacterial enzymes critical to DNA replication, the topoisomerases DNA gyrase and topo IV. Unfortunately, mutations lowering drug affinity for both enzymes are now widespread, rendering these drugs ineffective for many pathogens. To undermine this form of resistance, we examined how bacteria with target alterations differentially cope with fluoroquinolone exposures. We studied this problem in the nosocomial pathogen A. baumannii, which causes drug-resistant life-threatening infections. Employing genome-wide approaches, we uncovered numerous pathways that could be exploited to raise fluoroquinolone sensitivity independently of target alteration. Remarkably, fluoroquinolone targeting of topo IV in specific mutants caused dramatic hyperinduction of prophage replication and enhanced the mutagenic DNA damage response, but these responses were muted in strains with DNA gyrase as the primary target. This work demonstrates that resistance evolution via target modification can profoundly modulate the antibiotic stress response, revealing potential resistance-associated liabilities.
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Gonyar LA, Gelbach PE, McDuffie DG, Koeppel AF, Chen Q, Lee G, Temple LM, Stibitz S, Hewlett EL, Papin JA, Damron FH, Eby JC. In Vivo Gene Essentiality and Metabolism in Bordetella pertussis. mSphere 2019; 4:e00694-18. [PMID: 31118307 PMCID: PMC6531889 DOI: 10.1128/msphere.00694-18] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Accepted: 05/10/2019] [Indexed: 12/30/2022] Open
Abstract
Bordetella pertussis is the causative agent of whooping cough, a serious respiratory illness affecting children and adults, associated with prolonged cough and potential mortality. Whooping cough has reemerged in recent years, emphasizing a need for increased knowledge of basic mechanisms of B. pertussis growth and pathogenicity. While previous studies have provided insight into in vitro gene essentiality of this organism, very little is known about in vivo gene essentiality, a critical gap in knowledge, since B. pertussis has no previously identified environmental reservoir and is isolated from human respiratory tract samples. We hypothesize that the metabolic capabilities of B. pertussis are especially tailored to the respiratory tract and that many of the genes involved in B. pertussis metabolism would be required to establish infection in vivo In this study, we generated a diverse library of transposon mutants and then used it to probe gene essentiality in vivo in a murine model of infection. Using the CON-ARTIST pipeline, 117 genes were identified as conditionally essential at 1 day postinfection, and 169 genes were identified as conditionally essential at 3 days postinfection. Most of the identified genes were associated with metabolism, and we utilized two existing genome-scale metabolic network reconstructions to probe the effects of individual essential genes on biomass synthesis. This analysis suggested a critical role for glucose metabolism and lipooligosaccharide biosynthesis in vivo This is the first genome-wide evaluation of in vivo gene essentiality in B. pertussis and provides tools for future exploration.IMPORTANCE Our study describes the first in vivo transposon sequencing (Tn-seq) analysis of B. pertussis and identifies genes predicted to be essential for in vivo growth in a murine model of intranasal infection, generating key resources for future investigations into B. pertussis pathogenesis and vaccine design.
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Affiliation(s)
- Laura A Gonyar
- Department of Pediatrics, University of Virginia, Charlottesville, Virginia, USA
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA
| | - Patrick E Gelbach
- Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA
| | - Dennis G McDuffie
- Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA
| | - Alexander F Koeppel
- Department of Medicine, University of Virginia, Charlottesville, Virginia, USA
| | - Qing Chen
- Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, USA
| | - Gloria Lee
- Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, USA
| | - Louise M Temple
- Department of Integrated Science and Technology, James Madison University, Harrisonburg, Virginia, USA
| | - Scott Stibitz
- Center for Biologics Evaluation and Research, Food and Drug Administration, Silver Spring, Maryland, USA
| | - Erik L Hewlett
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA
| | - Jason A Papin
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA
- Department of Biomedical Engineering, University of Virginia, Charlottesville, Virginia, USA
- Department of Biochemistry and Molecular Genetics, University of Virginia, Charlottesville, Virginia, USA
| | - F Heath Damron
- Department of Microbiology, Immunology and Cell Biology, West Virginia University, Morgantown, West Virginia, USA
- Vaccine Development Center, West Virginia University Health Sciences Center, Morgantown, West Virginia, USA
| | - Joshua C Eby
- Department of Medicine, Division of Infectious Diseases and International Health, University of Virginia, Charlottesville, Virginia, USA
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103
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Genome-Wide Identification of Fitness Factors in Seawater for Edwardsiella piscicida. Appl Environ Microbiol 2019; 85:AEM.00233-19. [PMID: 30877123 DOI: 10.1128/aem.00233-19] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2019] [Accepted: 03/12/2019] [Indexed: 12/29/2022] Open
Abstract
Marine pathogens are transmitted from one host to another through seawater. Therefore, it is important for marine pathogens to maintain survival or growth in seawater. However, little is known about how marine pathogens adapt to living in seawater environments. Here, transposon insertion sequencing was performed to explore the genetic determinants of Edwardsiella piscicida survival in seawater at 16 and 28°C. Seventy-one mutants with mutations mainly in metabolism-, transportation-, and type III secretion system (T3SS)-related genes showed significantly increased or impaired fitness in 16°C water. In 28°C seawater, 63 genes associated with transcription and translation, as well as energy production and conversion, were essential for optimal survival of the bacterium. In particular, 11 T3SS-linked mutants displayed enhanced fitness in 16°C seawater but not in 28°C seawater. In addition, 13 genes associated with oxidative phosphorylation and 4 genes related to ubiquinone synthesis were identified for survival in 28°C seawater but not in 16°C seawater, which suggests that electron transmission and energy-producing aerobic respiration chain factors are indispensable for E. piscicida to maintain survival in higher-temperature seawater. In conclusion, we defined genes and processes related to metabolism and virulence that operate in E. piscicida to facilitate survival in low- and high-temperature seawater, which may underlie the infection outbreak mechanisms of E. piscicida and facilitate the development of improved vaccines against marine pathogens.IMPORTANCE Edwardsiella piscicida is one of the most important marine pathogens and causes serious edwardsiellosis in farmed fish during the summer-autumn seasonal changes, resulting in enormous losses to aquaculture industries worldwide. Survival and transmission of the pathogen in seawater are critical steps that increase the risk of outbreaks. To investigate the mechanism of survival in seawater for this marine pathogen, we used transposon insertion sequencing analysis to explore the fitness determinants in summer and autumn seawater. Approximately 127 genes linked to metabolism and virulence, as well as other processes, were revealed in E. piscicida to contribute to better adaptations to the seasonal alternations of seawater environments; these genes provide important insights into the infection outbreak mechanisms of E. piscicida and potential improved treatments or vaccines against marine pathogens.
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Abstract
Genomics offered the promise of transforming antibiotic discovery by revealing many new essential genes as good targets, but the results fell short of the promise. While numerous factors contributed to the disappointing yield, one factor was that essential genes for a bacterial species were often defined based on a single or limited number of strains grown under a single or limited number of in vitro laboratory conditions. In fact, the essentiality of a gene can depend on both the genetic background and growth condition. We thus developed a strategy for more rigorously defining the core essential genome of a bacterial species by studying many pathogen strains and growth conditions. We assessed how many strains must be examined to converge on a set of core essential genes for a species. We used transposon insertion sequencing (Tn-Seq) to define essential genes in nine strains of Pseudomonas aeruginosa on five different media and developed a statistical model, FiTnEss, to classify genes as essential versus nonessential across all strain-medium combinations. We defined a set of 321 core essential genes, representing 6.6% of the genome. We determined that analysis of four strains was typically sufficient in P. aeruginosa to converge on a set of core essential genes likely to be essential across the species across a wide range of conditions relevant to in vivo infection, and thus to represent attractive targets for novel drug discovery.
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105
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Passaris I, Tadesse WM, Gayán E, Aertsen A. Construction and validation of the Tn5-P LtetO-1-msfGFP transposon as a tool to probe protein expression and localization. J Microbiol Methods 2019; 161:56-62. [PMID: 31004623 DOI: 10.1016/j.mimet.2019.04.012] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/23/2019] [Revised: 04/16/2019] [Accepted: 04/16/2019] [Indexed: 11/28/2022]
Abstract
In this study we report the design, construction and validation of a novel transposon aimed to systematically screen for protein localization and expression patterns in prokaryotes using fluorescence microscopy. Upon random insertion in an open reading frame in the proper frame and orientation, the transposon creates an N-terminal fluorescent protein fusion to the msfGFP reporter. Moreover, in order to examine the localization of fusion proteins whose native expression might be too low or absent, the transposon was fitted with a PLtetO-1 promoter that makes the expression of the generated fluorescent protein fusions controllable by anhydrotetracycline. Importantly, upon flipping out the PLtetO-1 promoter and neighboring antibiotic resistance marker, an in-frame "sandwich" msfGFP fusion is created in which the N- and C-terminal portions of the targeted protein are again controlled by its native promoter.
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Affiliation(s)
- Ioannis Passaris
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, KU Leuven. Faculty of Bioscience Engineering, Kasteelpark Arenberg 22, 3000 Leuven, Belgium
| | - Wubishet M Tadesse
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, KU Leuven. Faculty of Bioscience Engineering, Kasteelpark Arenberg 22, 3000 Leuven, Belgium
| | - Elisa Gayán
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, KU Leuven. Faculty of Bioscience Engineering, Kasteelpark Arenberg 22, 3000 Leuven, Belgium
| | - Abram Aertsen
- Laboratory of Food Microbiology, Department of Microbial and Molecular Systems, KU Leuven. Faculty of Bioscience Engineering, Kasteelpark Arenberg 22, 3000 Leuven, Belgium.
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106
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Blazier AS, Papin JA. Reconciling high-throughput gene essentiality data with metabolic network reconstructions. PLoS Comput Biol 2019; 15:e1006507. [PMID: 30973869 PMCID: PMC6478342 DOI: 10.1371/journal.pcbi.1006507] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/07/2018] [Revised: 04/23/2019] [Accepted: 03/06/2019] [Indexed: 11/30/2022] Open
Abstract
The identification of genes essential for bacterial growth and survival represents a promising strategy for the discovery of antimicrobial targets. Essential genes can be identified on a genome-scale using transposon mutagenesis approaches; however, variability between screens and challenges with interpretation of essentiality data hinder the identification of both condition-independent and condition-dependent essential genes. To illustrate the scope of these challenges, we perform a large-scale comparison of multiple published Pseudomonas aeruginosa gene essentiality datasets, revealing substantial differences between the screens. We then contextualize essentiality using genome-scale metabolic network reconstructions and demonstrate the utility of this approach in providing functional explanations for essentiality and reconciling differences between screens. Genome-scale metabolic network reconstructions also enable a high-throughput, quantitative analysis to assess the impact of media conditions on the identification of condition-independent essential genes. Our computational model-driven analysis provides mechanistic insight into essentiality and contributes novel insights for design of future gene essentiality screens and the identification of core metabolic processes. With the rise of antibiotic resistance, there is a growing need to discover new therapeutic targets to treat bacterial infections. One attractive strategy is to target genes that are essential for growth and survival. Essential genes can be identified with transposon mutagenesis approaches; however, variability between screens and challenges with interpretation of essentiality data hinder the identification and analysis of essential genes. We performed a large-scale comparison of multiple gene essentiality screens of the microbial pathogen Pseudomonas aeruginosa. We implemented a computational model-driven approach to provide functional explanations for essentiality and reconcile differences between screens. The integration of computational modeling with high-throughput experimental screens may enable the identification of drug targets with high-confidence and provide greater understanding for the development of novel therapeutic strategies.
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Affiliation(s)
- Anna S. Blazier
- Biomedical Engineering, University of Virginia, Charlottesville, Virginia, United States of America
| | - Jason A. Papin
- Biomedical Engineering, University of Virginia, Charlottesville, Virginia, United States of America
- Medicine, Infectious Diseases & International Health, University of Virginia, Charlottesville, Virginia, United States of America
- Biochemistry & Molecular Genetics, University of Virginia, Charlottesville, Virginia, United States of America
- * E-mail:
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107
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Transcriptional noise and exaptation as sources for bacterial sRNAs. Biochem Soc Trans 2019; 47:527-539. [PMID: 30837318 DOI: 10.1042/bst20180171] [Citation(s) in RCA: 23] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2018] [Revised: 02/01/2019] [Accepted: 02/01/2019] [Indexed: 11/17/2022]
Abstract
Understanding how new genes originate and integrate into cellular networks is key to understanding evolution. Bacteria present unique opportunities for both the natural history and experimental study of gene origins, due to their large effective population sizes, rapid generation times, and ease of genetic manipulation. Bacterial small non-coding RNAs (sRNAs), in particular, many of which operate through a simple antisense regulatory logic, may serve as tractable models for exploring processes of gene origin and adaptation. Understanding how and on what timescales these regulatory molecules arise has important implications for understanding the evolution of bacterial regulatory networks, in particular, for the design of comparative studies of sRNA function. Here, we introduce relevant concepts from evolutionary biology and review recent work that has begun to shed light on the timescales and processes through which non-functional transcriptional noise is co-opted to provide regulatory functions. We explore possible scenarios for sRNA origin, focusing on the co-option, or exaptation, of existing genomic structures which may provide protected spaces for sRNA evolution.
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108
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Shields RC, Jensen PA. The bare necessities: Uncovering essential and condition-critical genes with transposon sequencing. Mol Oral Microbiol 2019; 34:39-50. [PMID: 30739386 DOI: 10.1111/omi.12256] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2018] [Revised: 01/18/2019] [Accepted: 02/06/2019] [Indexed: 12/11/2022]
Abstract
Querying gene function in bacteria has been greatly accelerated by the advent of transposon sequencing (Tn-seq) technologies (related Tn-seq strategies are known as TraDIS, INSeq, RB-TnSeq, and HITS). Pooled populations of transposon mutants are cultured in an environment and next-generation sequencing tools are used to determine areas of the genome that are important for bacterial fitness. In this review we provide an overview of Tn-seq methodologies and discuss how Tn-seq has been applied, or could be applied, to the study of oral microbiology. These applications include studying the essential genome as a means to rationally design therapeutic agents. Tn-seq has also contributed to our understanding of well-studied biological processes in oral bacteria. Other important applications include in vivo pathogenesis studies and use of Tn-seq to probe the molecular basis of microbial interactions. We also highlight recent advancements in techniques that act in synergy with Tn-seq such as clustered regularly interspaced short palindromic repeats (CRISPR) interference and microfluidic chip platforms.
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Affiliation(s)
- Robert C Shields
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida
| | - Paul A Jensen
- Department of Bioengineering and Carl R. Woese Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois
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109
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Abstract
Transposon insertion sequencing (TIS) is a widely used technique for conducting genome-scale forward genetic screens in bacteria. However, few methods enable comparison of TIS data across multiple replicates of a screen or across independent screens, including screens performed in different organisms. Here, we introduce a post hoc analytic framework, comparative TIS (CompTIS), which utilizes unsupervised learning to enable meta-analysis of multiple TIS data sets. CompTIS first implements screen-level principal-component analysis (PCA) and clustering to identify variation between the TIS screens. This initial screen-level analysis facilitates the selection of related screens for additional analyses, reveals the relatedness of complex environments based on growth phenotypes measured by TIS, and provides a useful quality control step. Subsequently, PCA is performed on genes to identify loci whose corresponding mutants lead to concordant/discordant phenotypes across all or in a subset of screens. We used CompTIS to analyze published intestinal colonization TIS data sets from two vibrio species. Gene-level analyses identified both pan-vibrio genes required for intestinal colonization and conserved genes that displayed species-specific requirements. CompTIS is applicable to virtually any combination of TIS screens and can be implemented without regard to either the number of screens or the methods used for upstream data analysis.IMPORTANCE Forward genetic screens are powerful tools for functional genomics. The comparison of similar forward genetic screens performed in different organisms enables the identification of genes with similar or different phenotypes across organisms. Transposon insertion sequencing is a widely used method for conducting genome-scale forward genetic screens in bacteria, yet few bioinformatic approaches have been developed to compare the results of screen replicates and different screens conducted across species or strains. Here, we used principal-component analysis (PCA) and hierarchical clustering, two unsupervised learning approaches, to analyze the relatedness of multiple in vivo screens of pathogenic vibrios. This analytic framework reveals both shared pan-vibrio requirements for intestinal colonization and strain-specific dependencies. Our findings suggest that PCA-based analytics will be a straightforward widely applicable approach for comparing diverse transposon insertion sequencing screens.
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110
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Abstract
Bacterial regulatory RNAs are key players in adaptation to changing environmental conditions and response to diverse cellular stresses. However, while regulatory RNAs of bacterial pathogens have been intensely studied under defined conditions in vitro, characterization of their role during the infection of eukaryotic host organisms is lagging behind. This review summarizes our current understanding of the contribution of the different classes of regulatory RNAs and RNA-binding proteins to bacterial virulence and illustrates their role in infection by reviewing the mechanisms of some prominent representatives of each class. Emerging technologies are described that bear great potential for global, unbiased studies of virulence-related RNAs in bacterial model and nonmodel pathogens in the future. The review concludes by deducing common principles of RNA-mediated gene expression control of virulence programs in different pathogens, and by defining important open questions for upcoming research in the field.
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111
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diCenzo GC, Mengoni A, Fondi M. Tn-Core: A Toolbox for Integrating Tn-seq Gene Essentiality Data and Constraint-Based Metabolic Modeling. ACS Synth Biol 2019; 8:158-169. [PMID: 30525460 DOI: 10.1021/acssynbio.8b00432] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
The design of synthetic cells requires a detailed understanding of the relevance of genes and gene networks underlying complex cellular phenotypes. Transposon-sequencing (Tn-seq) and constraint-based metabolic modeling can be used to probe the core genetic and metabolic networks underlying a biological process. Integrating these highly complementary experimental and in silico approaches has the potential to yield a highly comprehensive understanding of the core networks of a cell. Specifically, it can facilitate the interpretation of Tn-seq data sets and identify gaps in the data that could hinder the engineering of the cellular system, while also providing refined models for the accurate predictions of cellular metabolism. Here, we present Tn-Core, the first easy-to-use computational pipeline specifically designed for integrating Tn-seq data with metabolic modeling, prepared for use by both experimental and computational biologists. Tn-Core is a MATLAB toolbox that contains several custom functions, and it is built upon existing functions within the COBRA Toolbox and the TIGER Toolbox. Tn-Core takes as input a genome-scale metabolic model, Tn-seq data, and optionally RNA-seq data, and returns: (i) a context-specific core metabolic model; (ii) an evaluation of redundancies within core metabolic pathways, and optionally (iii) a refined genome-scale metabolic model. A simple, user-friendly workflow, requiring limited knowledge of metabolic modeling, is provided that allows users to run the analyses and export the data as easy-to-explore files of value to both experimental and computational biologists. We demonstrate the utility of Tn-Core using Sinorhizobium meliloti, Pseudomonas aeruginosa, and Rhodobacter sphaeroides genome-scale metabolic reconstructions as case studies.
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Affiliation(s)
- George C. diCenzo
- Department of Biology, University of Florence, Sesto Fiorentino, Florence, 50019, Italy
| | - Alessio Mengoni
- Department of Biology, University of Florence, Sesto Fiorentino, Florence, 50019, Italy
| | - Marco Fondi
- Department of Biology, University of Florence, Sesto Fiorentino, Florence, 50019, Italy
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112
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Wei L, Qiao H, Liu B, Yin K, Liu Q, Zhang Y, Ma Y, Wang Q. MarTrack: A versatile toolbox of mariner transposon derivatives used for functional genetic analysis of bacterial genomes. Microbiol Res 2019; 219:84-93. [PMID: 30642470 DOI: 10.1016/j.micres.2018.11.008] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2018] [Revised: 11/22/2018] [Accepted: 11/23/2018] [Indexed: 11/28/2022]
Abstract
The mariner transposon family of Himar1 has been widely used for the random mutagenesis of bacteria to generate single insertions into the chromosome. Here, a versatile toolbox of mariner transposon derivatives was generated and applied to the functional genomics investigation of fish pathogen Edwardsiella piscicida. In this study, we combined the merits of the random mutagenesis of mariner transposon and common efficient reporter marker genes or regulatory elements, mcherry, gfp, luxAB, lacZ, sacBR, and PBAD and antibiotic resistance cassettes to construct a series of derivative transposon vectors, pMmch, pMKGR, pMCGR, pMXKGR, pMLKGR, pMSGR, and pMPR, based on the initial transposon pMar2xT7. The function and effectiveness of the modified transposons were verified by introducing them into E. piscicida EIB202. Based on the toolbox, a transposon insertion mutant library containing approximately 3.0 × 105 separated mutants was constructed to explore the upstream regulators of esrB, the master regulator of the type III and type VI secretion systems (T3/T6SS) in E. piscicida. Following analysis by Con-ARTIST, ETAE_2184 (renamed as EsrR) was screened out and identified as a novel regulator mediating T3SS expression. In addition, the esrR mutants displayed critical virulence attenuation. Due to the broad-range host compatibility of mariner transposons, the newly built transposon toolbox can be broadly applied for functional genomics studies in various bacteria.
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Affiliation(s)
- Lifan Wei
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, PR China
| | - Haoxian Qiao
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, PR China
| | - Bing Liu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, PR China
| | - Kaiyu Yin
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, PR China; Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai, PR China
| | - Qin Liu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, PR China; Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai, PR China
| | - Yuanxing Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, PR China; Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai, PR China
| | - Yue Ma
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, PR China; Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai, PR China.
| | - Qiyao Wang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, 130 Meilong Road, Shanghai, 200237, PR China; Shanghai Engineering Research Center of Maricultured Animal Vaccines, Shanghai, PR China.
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113
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diCenzo GC, Zamani M, Checcucci A, Fondi M, Griffitts JS, Finan TM, Mengoni A. Multidisciplinary approaches for studying rhizobium–legume symbioses. Can J Microbiol 2019; 65:1-33. [DOI: 10.1139/cjm-2018-0377] [Citation(s) in RCA: 49] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
The rhizobium–legume symbiosis is a major source of fixed nitrogen (ammonia) in the biosphere. The potential for this process to increase agricultural yield while reducing the reliance on nitrogen-based fertilizers has generated interest in understanding and manipulating this process. For decades, rhizobium research has benefited from the use of leading techniques from a very broad set of fields, including population genetics, molecular genetics, genomics, and systems biology. In this review, we summarize many of the research strategies that have been employed in the study of rhizobia and the unique knowledge gained from these diverse tools, with a focus on genome- and systems-level approaches. We then describe ongoing synthetic biology approaches aimed at improving existing symbioses or engineering completely new symbiotic interactions. The review concludes with our perspective of the future directions and challenges of the field, with an emphasis on how the application of a multidisciplinary approach and the development of new methods will be necessary to ensure successful biotechnological manipulation of the symbiosis.
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Affiliation(s)
- George C. diCenzo
- Department of Biology, University of Florence, Sesto Fiorentino, FI 50019, Italy
| | - Maryam Zamani
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Alice Checcucci
- Department of Biology, University of Florence, Sesto Fiorentino, FI 50019, Italy
| | - Marco Fondi
- Department of Biology, University of Florence, Sesto Fiorentino, FI 50019, Italy
| | - Joel S. Griffitts
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT 84602, USA
| | - Turlough M. Finan
- Department of Biology, McMaster University, Hamilton, ON L8S 4K1, Canada
| | - Alessio Mengoni
- Department of Biology, University of Florence, Sesto Fiorentino, FI 50019, Italy
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114
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Guanhua Y, Wang C, Wang X, Ma R, Zheng H, Liu Q, Zhang Y, Ma Y, Wang Q. Complete genome sequence of the marine fish pathogen Vibrio anguillarum and genome-wide transposon mutagenesis analysis of genes essential for in vivo infection. Microbiol Res 2018; 216:97-107. [DOI: 10.1016/j.micres.2018.08.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Revised: 08/21/2018] [Accepted: 08/23/2018] [Indexed: 12/14/2022]
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115
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Klobucar K, Brown ED. Use of genetic and chemical synthetic lethality as probes of complexity in bacterial cell systems. FEMS Microbiol Rev 2018; 42:4563584. [PMID: 29069427 DOI: 10.1093/femsre/fux054] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2017] [Accepted: 10/23/2017] [Indexed: 12/22/2022] Open
Abstract
Different conditions and genomic contexts are known to have an impact on gene essentiality and interactions. Synthetic lethal interactions occur when a combination of perturbations, either genetic or chemical, result in a more profound fitness defect than expected based on the effect of each perturbation alone. Synthetic lethality in bacterial systems has long been studied; however, during the past decade, the emerging fields of genomics and chemical genomics have led to an increase in the scale and throughput of these studies. Here, we review the concepts of genomics and chemical genomics in the context of synthetic lethality and their revolutionary roles in uncovering novel biology such as the characterization of genes of unknown function and in antibacterial drug discovery. We provide an overview of the methodologies, examples and challenges of both genetic and chemical synthetic lethal screening platforms. Finally, we discuss how to apply genetic and chemical synthetic lethal approaches to rationalize the synergies of drugs, screen for new and improved antibacterial therapies and predict drug mechanism of action.
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Affiliation(s)
- Kristina Klobucar
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, 1280 Main St West, Hamilton, ON L8N 3Z5, Canada
| | - Eric D Brown
- Department of Biochemistry and Biomedical Sciences, Michael G. DeGroote Institute for Infectious Disease Research, McMaster University, 1280 Main St West, Hamilton, ON L8N 3Z5, Canada
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116
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Carda-Diéguez M, Silva-Hernández FX, Hubbard TP, Chao MC, Waldor MK, Amaro C. Comprehensive identification of Vibrio vulnificus genes required for growth in human serum. Virulence 2018; 9:981-993. [PMID: 29697309 PMCID: PMC6037467 DOI: 10.1080/21505594.2018.1455464] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
Vibrio vulnificus can be a highly invasive pathogen capable of spreading from an infection site to the bloodstream, causing sepsis and death. To survive and proliferate in blood, the pathogen requires mechanisms to overcome the innate immune defenses and metabolic limitations of this host niche. We created a high-density transposon mutant library in YJ016, a strain representative of the most virulent V. vulnificus lineage (or phylogroup) and used transposon insertion sequencing (TIS) screens to identify loci that enable the pathogen to survive and proliferate in human serum. Initially, genes underrepresented for insertions were used to estimate the V. vulnificus essential gene set; comparisons of these genes with similar TIS-based classification of underrepresented genes in other vibrios enabled the compilation of a common Vibrio essential gene set. Analysis of the relative abundance of insertion mutants in the library after exposure to serum suggested that genes involved in capsule biogenesis are critical for YJ016 complement resistance. Notably, homologues of two genes required for YJ016 serum-resistance and capsule biogenesis were not previously linked to capsule biogenesis and are largely absent from other V. vulnificus strains. The relative abundance of mutants after exposure to heat inactivated serum was compared with the findings from the serum screen. These comparisons suggest that in both conditions the pathogen relies on its Na+ transporting NADH-ubiquinone reductase (NQR) complex and type II secretion system to survive/proliferate within the metabolic constraints of serum. Collectively, our findings reveal the potency of comparative TIS screens to provide knowledge of how a pathogen overcomes the diverse limitations to growth imposed by serum.
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Affiliation(s)
- M Carda-Diéguez
- a Department of Microbiology and Ecology , University of Valencia. Dr. Moliner 50 , Burjassot , Spain.,b ERI BIOTECMED , Universitat de València. Dr Moliner 50 , Burjassot , Spain
| | - F X Silva-Hernández
- a Department of Microbiology and Ecology , University of Valencia. Dr. Moliner 50 , Burjassot , Spain
| | - T P Hubbard
- c Division of Infectious Disease , Brigham and Women's Hospital , Boston , Massachusetts , United States of America.,e Department of Microbiology and Immunobiology , Harvard Medical School , Boston , Massachusetts , United States of America
| | - M C Chao
- c Division of Infectious Disease , Brigham and Women's Hospital , Boston , Massachusetts , United States of America.,d Howard Hughes Medical Institute , Boston , Massachusetts , United States of America.,e Department of Microbiology and Immunobiology , Harvard Medical School , Boston , Massachusetts , United States of America
| | - M K Waldor
- c Division of Infectious Disease , Brigham and Women's Hospital , Boston , Massachusetts , United States of America.,d Howard Hughes Medical Institute , Boston , Massachusetts , United States of America.,e Department of Microbiology and Immunobiology , Harvard Medical School , Boston , Massachusetts , United States of America
| | - C Amaro
- a Department of Microbiology and Ecology , University of Valencia. Dr. Moliner 50 , Burjassot , Spain.,b ERI BIOTECMED , Universitat de València. Dr Moliner 50 , Burjassot , Spain
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117
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Hentchel KL, Reyes Ruiz LM, Curtis PD, Fiebig A, Coleman ML, Crosson S. Genome-scale fitness profile of Caulobacter crescentus grown in natural freshwater. ISME JOURNAL 2018; 13:523-536. [PMID: 30297849 DOI: 10.1038/s41396-018-0295-6] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Revised: 09/18/2018] [Accepted: 09/21/2018] [Indexed: 12/29/2022]
Abstract
Bacterial genomes evolve in complex ecosystems and are best understood in this natural context, but replicating such conditions in the lab is challenging. We used transposon sequencing to define the fitness consequences of gene disruption in the bacterium Caulobacter crescentus grown in natural freshwater, compared with axenic growth in common laboratory media. Gene disruptions in amino-acid and nucleotide sugar biosynthesis pathways and in metabolic substrate transport machinery impaired fitness in both lake water and defined minimal medium relative to complex peptone broth. Fitness in lake water was enhanced by insertions in genes required for flagellum biosynthesis and reduced by insertions in genes involved in biosynthesis of the holdfast surface adhesin. We further uncovered numerous hypothetical and uncharacterized genes for which disruption impaired fitness in lake water, defined minimal medium, or both. At the genome scale, the fitness profile of mutants cultivated in lake water was more similar to that in complex peptone broth than in defined minimal medium. Microfiltration of lake water did not significantly affect the terminal cell density or the fitness profile of the transposon mutant pool, suggesting that Caulobacter does not strongly interact with other microbes in this ecosystem on the measured timescale. Fitness of select mutants with defects in cell surface biosynthesis and environmental sensing were significantly more variable across days in lake water than in defined medium, presumably owing to day-to-day heterogeneity in the lake environment. This study reveals genetic interactions between Caulobacter and a natural freshwater environment, and provides a new avenue to study gene function in complex ecosystems.
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Affiliation(s)
- Kristy L Hentchel
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
| | - Leila M Reyes Ruiz
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA
| | - Patrick D Curtis
- Department of Biology, University of Mississippi, University, MS, 38677, USA
| | - Aretha Fiebig
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA.
| | - Maureen L Coleman
- Department of the Geophysical Sciences, University of Chicago, Chicago, IL, 60637, USA.
| | - Sean Crosson
- Department of Biochemistry and Molecular Biology, University of Chicago, Chicago, IL, 60637, USA.
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118
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Genetic Determinants of Penicillin Tolerance in Vibrio cholerae. Antimicrob Agents Chemother 2018; 62:AAC.01326-18. [PMID: 30061291 DOI: 10.1128/aac.01326-18] [Citation(s) in RCA: 27] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2018] [Accepted: 07/26/2018] [Indexed: 12/25/2022] Open
Abstract
Many bacteria are resistant to killing (tolerant) by typically bactericidal antibiotics due to their ability to counteract drug-induced cell damage. Vibrio cholerae, the cholera agent, displays an unusually high tolerance to diverse inhibitors of cell wall synthesis. Exposure to these agents, which in other bacteria leads to lysis and death, results in a breakdown of the cell wall and subsequent sphere formation in V. cholerae Spheres readily recover to rod-shaped cells upon antibiotic removal, but the mechanisms mediating the recovery process are not well characterized. Here, we found that the mechanisms of recovery are dependent on environmental conditions. Interestingly, on agarose pads, spheres undergo characteristic stages during the restoration of rod shape. Drug inhibition and microscopy experiments suggest that class A penicillin binding proteins (aPBPs) play a more active role than the Rod system, especially early in sphere recovery. Transposon insertion sequencing (TnSeq) analyses revealed that lipopolysaccharide (LPS) and cell wall biogenesis genes, as well as the sigma E cell envelope stress response, were particularly critical for recovery. LPS core and O-antigen appear to be more critical for sphere formation/integrity and viability than lipid A modifications. Overall, our findings demonstrate that the outer membrane is a key contributor to beta lactam tolerance and suggest a role for aPBPs in cell wall biogenesis in the absence of rod-shape cues. Factors required for postantibiotic recovery could serve as targets for antibiotic adjuvants that enhance the efficacy of antibiotics that inhibit cell wall biogenesis.
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119
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Luthra S, Rominski A, Sander P. The Role of Antibiotic-Target-Modifying and Antibiotic-Modifying Enzymes in Mycobacterium abscessus Drug Resistance. Front Microbiol 2018; 9:2179. [PMID: 30258428 PMCID: PMC6143652 DOI: 10.3389/fmicb.2018.02179] [Citation(s) in RCA: 129] [Impact Index Per Article: 21.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/02/2018] [Accepted: 08/24/2018] [Indexed: 11/21/2022] Open
Abstract
The incidence and prevalence of non-tuberculous mycobacterial (NTM) infections have been increasing worldwide and lately led to an emerging public health problem. Among rapidly growing NTM, Mycobacterium abscessus is the most pathogenic and drug resistant opportunistic germ, responsible for disease manifestations ranging from “curable” skin infections to only “manageable” pulmonary disease. Challenges in M. abscessus treatment stem from the bacteria’s high-level innate resistance and comprise long, costly and non-standardized administration of antimicrobial agents, poor treatment outcomes often related to adverse effects and drug toxicities, and high relapse rates. Drug resistance in M. abscessus is conferred by an assortment of mechanisms. Clinically acquired drug resistance is normally conferred by mutations in the target genes. Intrinsic resistance is attributed to low permeability of M. abscessus cell envelope as well as to (multi)drug export systems. However, expression of numerous enzymes by M. abscessus, which can modify either the drug-target or the drug itself, is the key factor for the pathogen’s phenomenal resistance to most classes of antibiotics used for treatment of other moderate to severe infectious diseases, like macrolides, aminoglycosides, rifamycins, β-lactams and tetracyclines. In 2009, when M. abscessus genome sequence became available, several research groups worldwide started studying M. abscessus antibiotic resistance mechanisms. At first, lack of tools for M. abscessus genetic manipulation severely delayed research endeavors. Nevertheless, the last 5 years, significant progress has been made towards the development of conditional expression and homologous recombination systems for M. abscessus. As a result of recent research efforts, an erythromycin ribosome methyltransferase, two aminoglycoside acetyltransferases, an aminoglycoside phosphotransferase, a rifamycin ADP-ribosyltransferase, a β-lactamase and a monooxygenase were identified to frame the complex and multifaceted intrinsic resistome of M. abscessus, which clearly contributes to complications in treatment of this highly resistant pathogen. Better knowledge of the underlying mechanisms of drug resistance in M. abscessus could improve selection of more effective chemotherapeutic regimen and promote development of novel antimicrobials which can overwhelm the existing resistance mechanisms. This article reviews the currently elucidated molecular mechanisms of antibiotic resistance in M. abscessus, with a focus on its drug-target-modifying and drug-modifying enzymes.
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Affiliation(s)
- Sakshi Luthra
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Anna Rominski
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland
| | - Peter Sander
- Institute of Medical Microbiology, University of Zurich, Zurich, Switzerland.,National Center for Mycobacteria, Zurich, Switzerland
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120
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Comprehensive Functional Analysis of the Enterococcus faecalis Core Genome Using an Ordered, Sequence-Defined Collection of Insertional Mutations in Strain OG1RF. mSystems 2018; 3:mSystems00062-18. [PMID: 30225373 PMCID: PMC6134198 DOI: 10.1128/msystems.00062-18] [Citation(s) in RCA: 43] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2018] [Accepted: 08/03/2018] [Indexed: 12/14/2022] Open
Abstract
The robust ability of Enterococcus faecalis to survive outside the host and to spread via oral-fecal transmission and its high degree of intrinsic and acquired antimicrobial resistance all complicate the treatment of hospital-acquired enterococcal infections. The conserved E. faecalis core genome serves as an important genetic scaffold for evolution of this bacterium in the modern health care setting and also provides interesting vaccine and drug targets. We used an innovative pooling/sequencing strategy to map a large collection of arrayed transposon insertions in E. faecalis OG1RF and generated an arrayed library of defined mutants covering approximately 70% of the OG1RF genome. Then, we performed high-throughput transposon sequencing experiments using this library to determine core genomic determinants of bile resistance in OG1RF. This collection is a valuable resource for comprehensive, functional enterococcal genomics using both traditional and high-throughput approaches and enables immediate recovery of mutants of interest. Enterococcus faecalis is a common commensal bacterium in animal gastrointestinal (GI) tracts and a leading cause of opportunistic infections of humans in the modern health care setting. E. faecalis OG1RF is a plasmid-free strain that contains few mobile elements yet retains the robust survival characteristics, intrinsic antibiotic resistance, and virulence traits characteristic of most E. faecalis genotypes. To facilitate interrogation of the core enterococcal genetic determinants for competitive fitness in the GI tract, biofilm formation, intrinsic antimicrobial resistance, and survival in the environment, we generated an arrayed, sequence-defined set of chromosomal transposon insertions in OG1RF. We used an orthogonal pooling strategy in conjunction with Illumina sequencing to identify a set of mutants with unique, single Himar-based transposon insertions. The mutants contained insertions in 1,926 of 2,651 (72.6%) annotated open reading frames and in the majority of hypothetical protein-encoding genes and intergenic regions greater than 100 bp in length, which could encode small RNAs. As proof of principle of the usefulness of this arrayed transposon library, we created a minimal input pool containing 6,829 mutants chosen for maximal genomic coverage and used an approach that we term SMarT (sequence-defined marinertechnology) transposon sequencing (TnSeq) to identify numerous genetic determinants of bile resistance in E. faecalis OG1RF. These included several genes previously associated with bile acid resistance as well as new loci. Our arrayed library allows functional screening of a large percentage of the genome with a relatively small number of mutants, reducing potential effects of bottlenecking, and enables immediate recovery of mutants following competitions. IMPORTANCE The robust ability of Enterococcus faecalis to survive outside the host and to spread via oral-fecal transmission and its high degree of intrinsic and acquired antimicrobial resistance all complicate the treatment of hospital-acquired enterococcal infections. The conserved E. faecalis core genome serves as an important genetic scaffold for evolution of this bacterium in the modern health care setting and also provides interesting vaccine and drug targets. We used an innovative pooling/sequencing strategy to map a large collection of arrayed transposon insertions in E. faecalis OG1RF and generated an arrayed library of defined mutants covering approximately 70% of the OG1RF genome. Then, we performed high-throughput transposon sequencing experiments using this library to determine core genomic determinants of bile resistance in OG1RF. This collection is a valuable resource for comprehensive, functional enterococcal genomics using both traditional and high-throughput approaches and enables immediate recovery of mutants of interest.
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121
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Cowley LA, Low AS, Pickard D, Boinett CJ, Dallman TJ, Day M, Perry N, Gally DL, Parkhill J, Jenkins C, Cain AK. Transposon Insertion Sequencing Elucidates Novel Gene Involvement in Susceptibility and Resistance to Phages T4 and T7 in Escherichia coli O157. mBio 2018. [PMID: 30042196 DOI: 10.1128/mbio] [Citation(s) in RCA: 76] [Impact Index Per Article: 12.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/12/2023] Open
Abstract
Experiments using bacteriophage (phage) to infect bacterial strains have helped define some basic genetic concepts in microbiology, but our understanding of the complexity of bacterium-phage interactions is still limited. As the global threat of antibiotic resistance continues to increase, phage therapy has reemerged as an attractive alternative or supplement to treating antibiotic-resistant bacterial infections. Further, the long-used method of phage typing to classify bacterial strains is being replaced by molecular genetic techniques. Thus, there is a growing need for a complete understanding of the precise molecular mechanisms underpinning phage-bacterium interactions to optimize phage therapy for the clinic as well as for retrospectively interpreting phage typing data on the molecular level. In this study, a genomics-based fitness assay (TraDIS) was used to identify all host genes involved in phage susceptibility and resistance for a T4 phage infecting Shiga-toxigenic Escherichia coli O157. The TraDIS results identified both established and previously unidentified genes involved in phage infection, and a subset were confirmed by site-directed mutagenesis and phenotypic testing of 14 T4 and 2 T7 phages. For the first time, the entire sap operon was implicated in phage susceptibility and, conversely, the stringent starvation protein A gene (sspA) was shown to provide phage resistance. Identifying genes involved in phage infection and replication should facilitate the selection of bespoke phage combinations to target specific bacterial pathogens.IMPORTANCE Antibiotic resistance has diminished treatment options for many common bacterial infections. Phage therapy is an alternative option that was once popularly used across Europe to kill bacteria within humans. Phage therapy acts by using highly specific viruses (called phages) that infect and lyse certain bacterial species to treat the infection. Whole-genome sequencing has allowed modernization of the investigations into phage-bacterium interactions. Here, using E. coli O157 and T4 bacteriophage as a model, we have exploited a genome-wide fitness assay to investigate all genes involved in defining phage resistance or susceptibility. This knowledge of the genetic determinants of phage resistance and susceptibility can be used to design bespoke phage combinations targeted to specific bacterial infections for successful infection eradication.
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Affiliation(s)
- Lauren A Cowley
- Gastrointestinal Bacterial Reference Unit, Public Health England, London United Kingdom
- Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Alison S Low
- Division of Immunity and Infection, the Roslin Institute and Royal (Dick) School of Veterinary Studies, the University of Edinburgh, Midlothian, United Kingdom
| | - Derek Pickard
- Wellcome Trust Sanger Institute, Hinxton, Cambridge United Kingdom
| | - Christine J Boinett
- Wellcome Trust Sanger Institute, Hinxton, Cambridge United Kingdom
- The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
| | - Timothy J Dallman
- Gastrointestinal Bacterial Reference Unit, Public Health England, London United Kingdom
| | - Martin Day
- Gastrointestinal Bacterial Reference Unit, Public Health England, London United Kingdom
| | - Neil Perry
- Gastrointestinal Bacterial Reference Unit, Public Health England, London United Kingdom
| | - David L Gally
- Division of Immunity and Infection, the Roslin Institute and Royal (Dick) School of Veterinary Studies, the University of Edinburgh, Midlothian, United Kingdom
| | - Julian Parkhill
- Wellcome Trust Sanger Institute, Hinxton, Cambridge United Kingdom
| | - Claire Jenkins
- Gastrointestinal Bacterial Reference Unit, Public Health England, London United Kingdom
| | - Amy K Cain
- Wellcome Trust Sanger Institute, Hinxton, Cambridge United Kingdom
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW, Australia
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122
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Cowley LA, Low AS, Pickard D, Boinett CJ, Dallman TJ, Day M, Perry N, Gally DL, Parkhill J, Jenkins C, Cain AK. Transposon Insertion Sequencing Elucidates Novel Gene Involvement in Susceptibility and Resistance to Phages T4 and T7 in Escherichia coli O157. mBio 2018; 9:e00705-18. [PMID: 30042196 PMCID: PMC6058288 DOI: 10.1128/mbio.00705-18] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2018] [Accepted: 06/27/2018] [Indexed: 01/01/2023] Open
Abstract
Experiments using bacteriophage (phage) to infect bacterial strains have helped define some basic genetic concepts in microbiology, but our understanding of the complexity of bacterium-phage interactions is still limited. As the global threat of antibiotic resistance continues to increase, phage therapy has reemerged as an attractive alternative or supplement to treating antibiotic-resistant bacterial infections. Further, the long-used method of phage typing to classify bacterial strains is being replaced by molecular genetic techniques. Thus, there is a growing need for a complete understanding of the precise molecular mechanisms underpinning phage-bacterium interactions to optimize phage therapy for the clinic as well as for retrospectively interpreting phage typing data on the molecular level. In this study, a genomics-based fitness assay (TraDIS) was used to identify all host genes involved in phage susceptibility and resistance for a T4 phage infecting Shiga-toxigenic Escherichia coli O157. The TraDIS results identified both established and previously unidentified genes involved in phage infection, and a subset were confirmed by site-directed mutagenesis and phenotypic testing of 14 T4 and 2 T7 phages. For the first time, the entire sap operon was implicated in phage susceptibility and, conversely, the stringent starvation protein A gene (sspA) was shown to provide phage resistance. Identifying genes involved in phage infection and replication should facilitate the selection of bespoke phage combinations to target specific bacterial pathogens.IMPORTANCE Antibiotic resistance has diminished treatment options for many common bacterial infections. Phage therapy is an alternative option that was once popularly used across Europe to kill bacteria within humans. Phage therapy acts by using highly specific viruses (called phages) that infect and lyse certain bacterial species to treat the infection. Whole-genome sequencing has allowed modernization of the investigations into phage-bacterium interactions. Here, using E. coli O157 and T4 bacteriophage as a model, we have exploited a genome-wide fitness assay to investigate all genes involved in defining phage resistance or susceptibility. This knowledge of the genetic determinants of phage resistance and susceptibility can be used to design bespoke phage combinations targeted to specific bacterial infections for successful infection eradication.
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Affiliation(s)
- Lauren A Cowley
- Gastrointestinal Bacterial Reference Unit, Public Health England, London United Kingdom
- Center for Communicable Disease Dynamics, Harvard T.H. Chan School of Public Health, Boston, Massachusetts, USA
| | - Alison S Low
- Division of Immunity and Infection, the Roslin Institute and Royal (Dick) School of Veterinary Studies, the University of Edinburgh, Midlothian, United Kingdom
| | - Derek Pickard
- Wellcome Trust Sanger Institute, Hinxton, Cambridge United Kingdom
| | - Christine J Boinett
- Wellcome Trust Sanger Institute, Hinxton, Cambridge United Kingdom
- The Hospital for Tropical Diseases, Wellcome Trust Major Overseas Programme, Oxford University Clinical Research Unit, Ho Chi Minh City, Vietnam
| | - Timothy J Dallman
- Gastrointestinal Bacterial Reference Unit, Public Health England, London United Kingdom
| | - Martin Day
- Gastrointestinal Bacterial Reference Unit, Public Health England, London United Kingdom
| | - Neil Perry
- Gastrointestinal Bacterial Reference Unit, Public Health England, London United Kingdom
| | - David L Gally
- Division of Immunity and Infection, the Roslin Institute and Royal (Dick) School of Veterinary Studies, the University of Edinburgh, Midlothian, United Kingdom
| | - Julian Parkhill
- Wellcome Trust Sanger Institute, Hinxton, Cambridge United Kingdom
| | - Claire Jenkins
- Gastrointestinal Bacterial Reference Unit, Public Health England, London United Kingdom
| | - Amy K Cain
- Wellcome Trust Sanger Institute, Hinxton, Cambridge United Kingdom
- Department of Chemistry and Biomolecular Sciences, Macquarie University, Sydney, NSW, Australia
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Abstract
Vibrio is a genus of ubiquitous bacteria found in a wide variety of aquatic and marine habitats; of the >100 described Vibrio spp., ~12 cause infections in humans. Vibrio cholerae can cause cholera, a severe diarrhoeal disease that can be quickly fatal if untreated and is typically transmitted via contaminated water and person-to-person contact. Non-cholera Vibrio spp. (for example, Vibrio parahaemolyticus, Vibrio alginolyticus and Vibrio vulnificus) cause vibriosis - infections normally acquired through exposure to sea water or through consumption of raw or undercooked contaminated seafood. Non-cholera bacteria can lead to several clinical manifestations, most commonly mild, self-limiting gastroenteritis, with the exception of V. vulnificus, an opportunistic pathogen with a high mortality that causes wound infections that can rapidly lead to septicaemia. Treatment for Vibrio spp. infection largely depends on the causative pathogen: for example, rehydration therapy for V. cholerae infection and debridement of infected tissues for V. vulnificus-associated wound infections, with antibiotic therapy for severe cholera and systemic infections. Although cholera is preventable and effective oral cholera vaccines are available, outbreaks can be triggered by natural or man-made events that contaminate drinking water or compromise access to safe water and sanitation. The incidence of vibriosis is rising, perhaps owing in part to the spread of Vibrio spp. favoured by climate change and rising sea water temperature.
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124
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Zhu J, Gong R, Zhu Q, He Q, Xu N, Xu Y, Cai M, Zhou X, Zhang Y, Zhou M. Genome-Wide Determination of Gene Essentiality by Transposon Insertion Sequencing in Yeast Pichia pastoris. Sci Rep 2018; 8:10223. [PMID: 29976927 PMCID: PMC6033949 DOI: 10.1038/s41598-018-28217-z] [Citation(s) in RCA: 20] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2017] [Accepted: 06/19/2018] [Indexed: 12/22/2022] Open
Abstract
In many prokaryotes but limited eukaryotic species, the combination of transposon mutagenesis and high-throughput sequencing has greatly accelerated the identification of essential genes. Here we successfully applied this technique to the methylotrophic yeast Pichia pastoris and classified its conditionally essential/non-essential gene sets. Firstly, we showed that two DNA transposons, TcBuster and Sleeping beauty, had high transposition activities in P. pastoris. By merging their insertion libraries and performing Tn-seq, we identified a total of 202,858 unique insertions under glucose supported growth condition. We then developed a machine learning method to classify the 5,040 annotated genes into putatively essential, putatively non-essential, ambig1 and ambig2 groups, and validated the accuracy of this classification model. Besides, Tn-seq was also performed under methanol supported growth condition and methanol specific essential genes were identified. The comparison of conditionally essential genes between glucose and methanol supported growth conditions helped to reveal potential novel targets involved in methanol metabolism and signaling. Our findings suggest that transposon mutagenesis and Tn-seq could be applied in the methylotrophic yeast Pichia pastoris to classify conditionally essential/non-essential gene sets. Our work also shows that determining gene essentiality under different culture conditions could help to screen for novel functional components specifically involved in methanol metabolism.
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Affiliation(s)
- Jinxiang Zhu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Ruiqing Gong
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Qiaoyun Zhu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Qiulin He
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Ning Xu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Yichun Xu
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Menghao Cai
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Xiangshan Zhou
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
| | - Yuanxing Zhang
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China
- Shanghai Collaborative Innovation Center for Biomanufacturing (SCICB), Shanghai, 200237, China
| | - Mian Zhou
- State Key Laboratory of Bioreactor Engineering, East China University of Science and Technology, Shanghai, 200237, China.
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125
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Abstract
Transposon insertion site sequencing (TIS) permits genome-wide, quantitative fitness assessment of individual genomic loci. In addition to the identification of essential genes in given growth conditions, TIS enables the elucidation of genetic networks such as synthetic lethal or suppressor gene combinations. Therefore, TIS becomes an exceptionally powerful tool for the high-throughput determination of genotype-phenotype relationships in bacteria. Here, we describe a protocol for the generation of high-density transposon insertion libraries and subsequent preparation of DNA samples for Illumina sequencing using the Gram-negative bacterium Vibrio cholerae as an example.
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126
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diCenzo GC, Benedict AB, Fondi M, Walker GC, Finan TM, Mengoni A, Griffitts JS. Robustness encoded across essential and accessory replicons of the ecologically versatile bacterium Sinorhizobium meliloti. PLoS Genet 2018; 14:e1007357. [PMID: 29672509 PMCID: PMC5929573 DOI: 10.1371/journal.pgen.1007357] [Citation(s) in RCA: 38] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2018] [Revised: 05/01/2018] [Accepted: 04/10/2018] [Indexed: 11/19/2022] Open
Abstract
Bacterial genome evolution is characterized by gains, losses, and rearrangements of functional genetic segments. The extent to which large-scale genomic alterations influence genotype-phenotype relationships has not been investigated in a high-throughput manner. In the symbiotic soil bacterium Sinorhizobium meliloti, the genome is composed of a chromosome and two large extrachromosomal replicons (pSymA and pSymB, which together constitute 45% of the genome). Massively parallel transposon insertion sequencing (Tn-seq) was employed to evaluate the contributions of chromosomal genes to growth fitness in both the presence and absence of these extrachromosomal replicons. Ten percent of chromosomal genes from diverse functional categories are shown to genetically interact with pSymA and pSymB. These results demonstrate the pervasive robustness provided by the extrachromosomal replicons, which is further supported by constraint-based metabolic modeling. A comprehensive picture of core S. meliloti metabolism was generated through a Tn-seq-guided in silico metabolic network reconstruction, producing a core network encompassing 726 genes. This integrated approach facilitated functional assignments for previously uncharacterized genes, while also revealing that Tn-seq alone missed over a quarter of wild-type metabolism. This work highlights the many functional dependencies and epistatic relationships that may arise between bacterial replicons and across a genome, while also demonstrating how Tn-seq and metabolic modeling can be used together to yield insights not obtainable by either method alone. S. meliloti, which has traditionally facilitated ground-breaking insights into symbiotic communication, is also emerging as an excellent model for studying the evolution of functional relationships between bacterial chromosomes and anciently acquired accessory replicons. Multi-replicon genome architecture is present in ~ 10% of presently sequenced bacterial genomes. The S. meliloti genome is composed of three circular replicons, two of which are dispensable even though they encompass nearly half of the protein-coding genes in this organism. The construction of strains lacking these replicons has enabled a straightforward, genome-wide analysis of interactions between the chromosome and the non-essential replicons, revealing extensive functional cooperation between these genomic components. This analysis enabled a substantial refinement of a metabolic network model for S. meliloti. The integration of massively parallel genotype-phenotype screening with in silico metabolic reconstruction has enhanced our understanding of metabolic network structure as it relates to genome evolution in S. meliloti, and exemplifies an approach that may be productively applied to other taxa. The combined experimental and computational approach employed here further provides unique insights into the pervasive genetic interactions that may exist within large bacterial genomes.
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Affiliation(s)
- George C. diCenzo
- Department of Biology, University of Florence, Sesto Fiorentino, FI, Italy
- * E-mail:
| | - Alex B. Benedict
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, United States of America
| | - Marco Fondi
- Department of Biology, University of Florence, Sesto Fiorentino, FI, Italy
| | - Graham C. Walker
- Department of Biology, Massachusetts Institute of Technology, Cambridge, MA, United States of America
| | | | - Alessio Mengoni
- Department of Biology, University of Florence, Sesto Fiorentino, FI, Italy
| | - Joel S. Griffitts
- Department of Microbiology and Molecular Biology, Brigham Young University, Provo, UT, United States of America
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127
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Purification of Intracellular Bacterial Communities during Experimental Urinary Tract Infection Reveals an Abundant and Viable Bacterial Reservoir. Infect Immun 2018; 86:IAI.00740-17. [PMID: 29378794 DOI: 10.1128/iai.00740-17] [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: 10/13/2017] [Accepted: 01/22/2018] [Indexed: 12/17/2022] Open
Abstract
Urinary tract infections (UTIs) are a major infection of humans, particularly affecting women. Recurrent UTIs can cause significant discomfort and expose patients to high levels of antibiotic use, which in turn contributes to the development of higher antibiotic resistance rates. Most UTIs are caused by uropathogenic Escherichia coli, which is able to form intracellular collections (termed intracellular bacterial communities [IBCs]) within the epithelial cells lining the bladder lumen. IBCs are seen in both infected mice and humans and are a potential cause of recurrent UTI. Genetic and molecular studies of IBCs have been hampered both by the low number of bacteria in IBCs relative to the number extracellular bacteria and by population bottlenecks that occur during IBC formation. We now report the development of a simple and rapid technique for isolating pure IBCs from experimentally infected mice. We verified the specificity and purity of the isolated IBCs via microscopy, gene expression, and culture-based methods. Our results further demonstrated that our isolation technique practically enables specific molecular studies of IBCs. In the first such direct measurement, we determined that a single epithelial cell containing an early IBC typically contains 103 viable bacteria. Our isolation technique complements recent progress in low-input, single-cell genomics to enable future genomic studies of the formation of IBCs and their activation pathways during recurrent UTI, which may lead to novel strategies to eliminate them from the bladder.
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128
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Genome-Wide Identification by Transposon Insertion Sequencing of Escherichia coli K1 Genes Essential for In Vitro Growth, Gastrointestinal Colonizing Capacity, and Survival in Serum. J Bacteriol 2018; 200:JB.00698-17. [PMID: 29339415 PMCID: PMC5847654 DOI: 10.1128/jb.00698-17] [Citation(s) in RCA: 22] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2017] [Accepted: 01/09/2018] [Indexed: 12/18/2022] Open
Abstract
Escherichia coli K1 strains are major causative agents of invasive disease of newborn infants. The age dependency of infection can be reproduced in neonatal rats. Colonization of the small intestine following oral administration of K1 bacteria leads rapidly to invasion of the blood circulation; bacteria that avoid capture by the mesenteric lymphatic system and evade antibacterial mechanisms in the blood may disseminate to cause organ-specific infections such as meningitis. Some E. coli K1 surface constituents, in particular the polysialic acid capsule, are known to contribute to invasive potential, but a comprehensive picture of the factors that determine the fully virulent phenotype has not emerged so far. We constructed a library and constituent sublibraries of ∼775,000 Tn5 transposon mutants of E. coli K1 strain A192PP and employed transposon-directed insertion site sequencing (TraDIS) to identify genes required for fitness for infection of 2-day-old rats. Transposon insertions were lacking in 357 genes following recovery on selective agar; these genes were considered essential for growth in nutrient-replete medium. Colonization of the midsection of the small intestine was facilitated by 167 E. coli K1 gene products. Restricted bacterial translocation across epithelial barriers precluded TraDIS analysis of gut-to-blood and blood-to-brain transits; 97 genes were required for survival in human serum. This study revealed that a large number of bacterial genes, many of which were not previously associated with systemic E. coli K1 infection, are required to realize full invasive potential. IMPORTANCEEscherichia coli K1 strains cause life-threatening infections in newborn infants. They are acquired from the mother at birth and colonize the small intestine, from where they invade the blood and central nervous system. It is difficult to obtain information from acutely ill patients that sheds light on physiological and bacterial factors determining invasive disease. Key aspects of naturally occurring age-dependent human infection can be reproduced in neonatal rats. Here, we employ transposon-directed insertion site sequencing to identify genes essential for the in vitro growth of E. coli K1 and genes that contribute to the colonization of susceptible rats. The presence of bottlenecks to invasion of the blood and cerebrospinal compartments precluded insertion site sequencing analysis, but we identified genes for survival in serum.
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129
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Duong DA, Jensen RV, Stevens AM. Discovery of Pantoea stewartii ssp. stewartii genes important for survival in corn xylem through a Tn-Seq analysis. MOLECULAR PLANT PATHOLOGY 2018; 19:1929-1941. [PMID: 29480976 PMCID: PMC6638119 DOI: 10.1111/mpp.12669] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/22/2017] [Revised: 02/21/2018] [Accepted: 02/22/2018] [Indexed: 05/29/2023]
Abstract
The bacterium Pantoea stewartii ssp. stewartii causes Stewart's wilt disease in corn. Pantoea stewartii is transmitted to plants via corn flea beetles, where it first colonizes the apoplast causing water-soaked lesions, and then migrates to the xylem and forms a biofilm that blocks water transport. Bacterial quorum sensing ensures that the exopolysaccharide production necessary for biofilm formation occurs only at high cell density. A genomic-level transposon sequencing (Tn-Seq) analysis was performed to identify additional bacterial genes essential for survival in planta and to provide insights into the plant-microbe interactions occurring during wilt disease. A mariner transposon library of approximately 40 000 mutants was constructed and used to inoculate corn seedlings through a xylem infection model. Cultures of the library grown in Luria-Bertani (LB) broth served as the in vitro pre-inoculation control. Tn-Seq analysis showed that the number of transposon mutations was reduced by more than 10-fold for 486 genes in planta compared with the library that grew in LB, suggesting that they are important for xylem survival. Interestingly, a small set of genes had a higher abundance of mutants in planta versus in vitro conditions, indicating enhanced strain fitness with loss of these genes inside the host. In planta competition assays retested the trends of the Tn-Seq data for several genes, including two outer membrane proteins, Lon protease and two quorum sensing-associated transcription factors, RcsA and LrhA. Virulence assays were performed to check for correlation between growth/colonization and pathogenicity. This study demonstrates the capacity of a Tn-Seq approach to advance our understanding of P. stewartii-corn interactions.
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Affiliation(s)
- Duy An Duong
- Department of Biological SciencesVirginia TechBlacksburgVA 24061USA
| | | | - Ann M. Stevens
- Department of Biological SciencesVirginia TechBlacksburgVA 24061USA
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130
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Di Minin G, Postlmayr A, Wutz A. HaSAPPy: A tool for candidate identification in pooled forward genetic screens of haploid mammalian cells. PLoS Comput Biol 2018; 14:e1005950. [PMID: 29337991 PMCID: PMC5798846 DOI: 10.1371/journal.pcbi.1005950] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2017] [Revised: 02/05/2018] [Accepted: 01/03/2018] [Indexed: 12/28/2022] Open
Abstract
Haploid cells are increasingly used for screening of complex pathways in animal genomes. Hemizygous mutations introduced through viral insertional mutagenesis can be directly selected for phenotypic changes. Here we present HaSAPPy a tool for analysing sequencing datasets of screens using insertional mutations in large pools of haploid cells. Candidate gene prediction is implemented through identification of enrichment of insertional mutations after selection by simultaneously evaluating several parameters. We have developed HaSAPPy for analysis of genetic screens for silencing factors of X chromosome inactivation in haploid mouse embryonic stem cells. To benchmark the performance, we further analyse several datasets of genetic screens in human haploid cells for which candidates have been validated. Our results support the effective candidate prediction strategy of HaSAPPy. HaSAPPy is implemented in Python, licensed under the MIT license, and is available from https://github.com/gdiminin/HaSAPPy.
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Affiliation(s)
- Giulio Di Minin
- Institute of Molecular Health Sciences, Department of Biology, Swiss Federal Institute of Technology ETH Hönggerberg, Zurich, Switzerland
- * E-mail: (AW); (GDM)
| | - Andreas Postlmayr
- Institute of Molecular Health Sciences, Department of Biology, Swiss Federal Institute of Technology ETH Hönggerberg, Zurich, Switzerland
| | - Anton Wutz
- Institute of Molecular Health Sciences, Department of Biology, Swiss Federal Institute of Technology ETH Hönggerberg, Zurich, Switzerland
- * E-mail: (AW); (GDM)
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131
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Shields RC, Zeng L, Culp DJ, Burne RA. Genomewide Identification of Essential Genes and Fitness Determinants of Streptococcus mutans UA159. mSphere 2018; 3:e00031-18. [PMID: 29435491 PMCID: PMC5806208 DOI: 10.1128/msphere.00031-18] [Citation(s) in RCA: 36] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2018] [Accepted: 01/19/2018] [Indexed: 11/20/2022] Open
Abstract
Transposon mutagenesis coupled with next-generation DNA sequencing (Tn-seq) is a powerful tool for discovering regions of the genome that are required for the survival of bacteria in different environments. We adapted this technique to the dental caries pathogen Streptococcus mutans UA159 and identified 11% of the genome as essential, with many genes encoding products required for replication, translation, lipid metabolism, and cell wall biogenesis. Comparison of the essential genome of S. mutans UA159 with those of selected other streptococci for which such information is available revealed several metabolic pathways and genes that are required in S. mutans, but not in some Streptococcus spp. We further identified genes that are essential for sustained growth in rich or defined medium, as well as for persistence in vivo in a rodent model of oral infection. Collectively, our results provide a novel and comprehensive view of the genes required for essential processes of S. mutans, many of which could represent potential targets for therapeutics. IMPORTANCE Tooth decay (dental caries) is a common cause of pain, impaired quality of life, and tooth loss in children and adults. It begins because of a compositional change in the microorganisms that colonize the tooth surface driven by repeated and sustained carbohydrate intake. Although several bacterial species are associated with tooth decay, Streptococcus mutans is the most common cause. Therefore, it is important to identify biological processes that contribute to the survival of S. mutans in the human mouth, with the aim of disrupting the processes with antimicrobial agents. We successfully applied Tn-seq to S. mutans, discovering genes that are required for survival, growth, and persistence, both in laboratory environments and in a mouse model of tooth decay. This work highlights new avenues for the control of an important human pathogen.
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Affiliation(s)
- Robert C. Shields
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida, USA
| | - Lin Zeng
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida, USA
| | - David J. Culp
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida, USA
| | - Robert A. Burne
- Department of Oral Biology, College of Dentistry, University of Florida, Gainesville, Florida, USA
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132
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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: 4.6] [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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133
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Abstract
Transposon insertion sequencing (TIS) is a powerful high-throughput genetic technique that is transforming functional genomics in prokaryotes, because it enables genome-wide mapping of the determinants of fitness. However, current approaches for analyzing TIS data assume that selective pressures are constant over time and thus do not yield information regarding changes in the genetic requirements for growth in dynamic environments (e.g., during infection). Here, we describe structured analysis of TIS data collected as a time series, termed pattern analysis of conditional essentiality (PACE). From a temporal series of TIS data, PACE derives a quantitative assessment of each mutant’s fitness over the course of an experiment and identifies mutants with related fitness profiles. In so doing, PACE circumvents major limitations of existing methodologies, specifically the need for artificial effect size thresholds and enumeration of bacterial population expansion. We used PACE to analyze TIS samples of Edwardsiella piscicida (a fish pathogen) collected over a 2-week infection period from a natural host (the flatfish turbot). PACE uncovered more genes that affect E. piscicida’s fitness in vivo than were detected using a cutoff at a terminal sampling point, and it identified subpopulations of mutants with distinct fitness profiles, one of which informed the design of new live vaccine candidates. Overall, PACE enables efficient mining of time series TIS data and enhances the power and sensitivity of TIS-based analyses. Transposon insertion sequencing (TIS) enables genome-wide mapping of the genetic determinants of fitness, typically based on observations at a single sampling point. Here, we move beyond analysis of endpoint TIS data to create a framework for analysis of time series TIS data, termed pattern analysis of conditional essentiality (PACE). We applied PACE to identify genes that contribute to colonization of a natural host by the fish pathogen Edwardsiella piscicida. PACE uncovered more genes that affect E. piscicida’s fitness in vivo than were detected using a terminal sampling point, and its clustering of mutants with related fitness profiles informed design of new live vaccine candidates. PACE yields insights into patterns of fitness dynamics and circumvents major limitations of existing methodologies. Finally, the PACE method should be applicable to additional “omic” time series data, including screens based on clustered regularly interspaced short palindromic repeats with Cas9 (CRISPR/Cas9).
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134
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Mandal RK, Kwon YM. Global Screening of Salmonella enterica Serovar Typhimurium Genes for Desiccation Survival. Front Microbiol 2017; 8:1723. [PMID: 28943871 PMCID: PMC5596212 DOI: 10.3389/fmicb.2017.01723] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2017] [Accepted: 08/24/2017] [Indexed: 01/13/2023] Open
Abstract
Salmonella spp., one of the most common foodborne bacterial pathogens, has the ability to survive under desiccation conditions in foods and food processing facilities for years. This raises the concerns of Salmonella infection in humans associated with low water activity foods. Salmonella responds to desiccation stress via complex pathways involving immediate physiological actions as well as coordinated genetic responses. However, the exact mechanisms of Salmonella to resist desiccation stress remain to be fully elucidated. In this study, we screened a genome-saturating transposon (Tn5) library of Salmonella Typhimurium (S. Typhimurium) 14028s under the in vitro desiccation stress using transposon sequencing (Tn-seq). We identified 61 genes and 6 intergenic regions required to overcome desiccation stress. Salmonella desiccation resistance genes were mostly related to energy production and conversion; cell wall/membrane/envelope biogenesis; inorganic ion transport and metabolism; regulation of biological process; DNA metabolic process; ABC transporters; and two component system. More than 20% of the Salmonella desiccation resistance genes encode either putative or hypothetical proteins. Phenotypic evaluation of 12 single gene knockout mutants showed 3 mutants (atpH, atpG, and corA) had significantly (p < 0.02) reduced survival as compared to the wild type during desiccation survival. Thus, our study provided new insights into the molecular mechanisms utilized by Salmonella for survival against desiccation stress. The findings might be further exploited to develop effective control strategies against Salmonella contamination in low water activity foods and food processing facilities.
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Affiliation(s)
- Rabindra K Mandal
- Department of Poultry Science, University of ArkansasFayetteville, AR, United States
| | - Young M Kwon
- Department of Poultry Science, University of ArkansasFayetteville, AR, United States.,Cell and Molecular Biology Program, University of ArkansasFayetteville, AR, United States
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135
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Sanchez-Larrayoz AF, Elhosseiny NM, Chevrette MG, Fu Y, Giunta P, Spallanzani RG, Ravi K, Pier GB, Lory S, Maira-Litrán T. Complexity of Complement Resistance Factors Expressed by Acinetobacter baumannii Needed for Survival in Human Serum. THE JOURNAL OF IMMUNOLOGY 2017; 199:2803-2814. [PMID: 28855313 DOI: 10.4049/jimmunol.1700877] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/16/2017] [Accepted: 08/07/2017] [Indexed: 11/19/2022]
Abstract
Acinetobacter baumannii is a bacterial pathogen with increasing impact in healthcare settings, due in part to this organism's resistance to many antimicrobial agents, with pneumonia and bacteremia as the most common manifestations of disease. A significant proportion of clinically relevant A. baumannii strains are resistant to killing by normal human serum (NHS), an observation supported in this study by showing that 12 out of 15 genetically diverse strains of A. baumannii are resistant to NHS killing. To expand our understanding of the genetic basis of A. baumannii serum resistance, a transposon (Tn) sequencing (Tn-seq) approach was used to identify genes contributing to this trait. An ordered Tn library in strain AB5075 with insertions in every nonessential gene was subjected to selection in NHS. We identified 50 genes essential for the survival of A. baumannii in NHS, including already known serum resistance factors, and many novel genes not previously associated with serum resistance. This latter group included the maintenance of lipid asymmetry genetic pathway as a key determinant in protecting A. baumannii from the bactericidal activity of NHS via the alternative complement pathway. Follow-up studies validated the role of eight additional genes identified by Tn-seq in A. baumannii resistance to killing by NHS but not by normal mouse serum, highlighting the human species specificity of A. baumannii serum resistance. The identification of a large number of genes essential for serum resistance in A. baumannii indicates the degree of complexity needed for this phenotype, which might reflect a general pattern that pathogens rely on to cause serious infections.
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Affiliation(s)
- Amaro F Sanchez-Larrayoz
- Division of Infectious Diseases, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115; and
| | - Noha M Elhosseiny
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115
| | - Marc G Chevrette
- Division of Infectious Diseases, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115; and
| | - Yang Fu
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115
| | - Peter Giunta
- Division of Infectious Diseases, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115; and
| | - Raúl G Spallanzani
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115
| | - Keerthikka Ravi
- Division of Infectious Diseases, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115; and
| | - Gerald B Pier
- Division of Infectious Diseases, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115; and
| | - Stephen Lory
- Department of Microbiology and Immunobiology, Harvard Medical School, Boston, MA 02115
| | - Tomás Maira-Litrán
- Division of Infectious Diseases, Department of Medicine, Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115; and
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136
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Abstract
Chemical-genetic approaches are based on measuring the cellular outcome of combining genetic and chemical perturbations in large-numbers in tandem. In these approaches the contribution of every gene to the fitness of an organism is measured upon exposure to different chemicals. Current technological advances enable the application of chemical genetics to almost any organism and at an unprecedented throughput. Here we review the underlying concepts behind chemical genetics, present its different vignettes and illustrate how such approaches can propel drug discovery.
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Affiliation(s)
- Elisabetta Cacace
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - George Kritikos
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
| | - Athanasios Typas
- European Molecular Biology Laboratory, Genome Biology Unit, Heidelberg, Germany
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137
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Senior NJ, Sasidharan K, Saint RJ, Scott AE, Sarkar-Tyson M, Ireland PM, Bullifent HL, Rong Yang Z, Moore K, Oyston PCF, Atkins TP, Atkins HS, Soyer OS, Titball RW. An integrated computational-experimental approach reveals Yersinia pestis genes essential across a narrow or a broad range of environmental conditions. BMC Microbiol 2017; 17:163. [PMID: 28732479 PMCID: PMC5521123 DOI: 10.1186/s12866-017-1073-8] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2017] [Accepted: 07/17/2017] [Indexed: 01/07/2023] Open
Abstract
Background The World Health Organization has categorized plague as a re-emerging disease and the potential for Yersinia pestis to also be used as a bioweapon makes the identification of new drug targets against this pathogen a priority. Environmental temperature is a key signal which regulates virulence of the bacterium. The bacterium normally grows outside the human host at 28 °C. Therefore, understanding the mechanisms that the bacterium used to adapt to a mammalian host at 37 °C is central to the development of vaccines or drugs for the prevention or treatment of human disease. Results Using a library of over 1 million Y. pestis CO92 random mutants and transposon-directed insertion site sequencing, we identified 530 essential genes when the bacteria were cultured at 28 °C. When the library of mutants was subsequently cultured at 37 °C we identified 19 genes that were essential at 37 °C but not at 28 °C, including genes which encode proteins that play a role in enabling functioning of the type III secretion and in DNA replication and maintenance. Using genome-scale metabolic network reconstruction we showed that growth conditions profoundly influence the physiology of the bacterium, and by combining computational and experimental approaches we were able to identify 54 genes that are essential under a broad range of conditions. Conclusions Using an integrated computational-experimental approach we identify genes which are required for growth at 37 °C and under a broad range of environments may be the best targets for the development of new interventions to prevent or treat plague in humans. Electronic supplementary material The online version of this article (doi:10.1186/s12866-017-1073-8) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Nicola J Senior
- College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4SB, UK
| | - Kalesh Sasidharan
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Richard J Saint
- Defence Science Technology Laboratory, Porton Down, Salisbury, SP4 OJQ, UK
| | - Andrew E Scott
- Defence Science Technology Laboratory, Porton Down, Salisbury, SP4 OJQ, UK
| | - Mitali Sarkar-Tyson
- Defence Science Technology Laboratory, Porton Down, Salisbury, SP4 OJQ, UK.,Marshall Centre for Infectious Disease Research and Training, School of Pathology and Laboratory Medicine, University of Western Australia, Perth, WA, 6009, Australia
| | - Philip M Ireland
- Defence Science Technology Laboratory, Porton Down, Salisbury, SP4 OJQ, UK
| | - Helen L Bullifent
- Defence Science Technology Laboratory, Porton Down, Salisbury, SP4 OJQ, UK
| | - Z Rong Yang
- College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4SB, UK
| | - Karen Moore
- College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4SB, UK
| | - Petra C F Oyston
- Defence Science Technology Laboratory, Porton Down, Salisbury, SP4 OJQ, UK
| | - Timothy P Atkins
- College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4SB, UK.,Defence Science Technology Laboratory, Porton Down, Salisbury, SP4 OJQ, UK
| | - Helen S Atkins
- College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4SB, UK.,Defence Science Technology Laboratory, Porton Down, Salisbury, SP4 OJQ, UK
| | - Orkun S Soyer
- School of Life Sciences, University of Warwick, Coventry, CV4 7AL, UK
| | - Richard W Titball
- College of Life and Environmental Sciences, University of Exeter, Exeter, EX4 4SB, UK.
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138
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Defining Genetic Fitness Determinants and Creating Genomic Resources for an Oral Pathogen. Appl Environ Microbiol 2017; 83:AEM.00797-17. [PMID: 28476775 DOI: 10.1128/aem.00797-17] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Accepted: 05/02/2017] [Indexed: 11/20/2022] Open
Abstract
Periodontitis is a microbial infection that destroys the structures that support the teeth. Although it is typically a chronic condition, rapidly progressing, aggressive forms are associated with the oral pathogen Aggregatibacter actinomycetemcomitans One of this bacterium's key virulence traits is its ability to attach to surfaces and form robust biofilms that resist killing by the host and antibiotics. Though much has been learned about A. actinomycetemcomitans since its initial discovery, we lack insight into a fundamental aspect of its basic biology, as we do not know the full set of genes that it requires for viability (the essential genome). Furthermore, research on A. actinomycetemcomitans is hampered by the field's lack of a mutant collection. To address these gaps, we used rapid transposon mutant sequencing (Tn-seq) to define the essential genomes of two strains of A. actinomycetemcomitans, revealing a core set of 319 genes. We then generated an arrayed mutant library comprising >1,500 unique insertions and used a sequencing-based approach to define each mutant's position (well and plate) in the library. To demonstrate its utility, we screened the library for mutants with weakened resistance to subinhibitory erythromycin, revealing the multidrug efflux pump AcrAB as a critical resistance factor. During the screen, we discovered that erythromycin induces A. actinomycetemcomitans to form biofilms. We therefore devised a novel Tn-seq-based screen to identify specific factors that mediate this phenotype and in follow-up experiments confirmed 4 mutants. Together, these studies present new insights and resources for investigating the basic biology and disease mechanisms of a human pathogen.IMPORTANCE Millions suffer from gum disease, which often is caused by Aggregatibacter actinomycetemcomitans, a bacterium that forms antibiotic-resistant biofilms. To fully understand any organism, we should be able to answer: what genes does it require for life? Here, we address this question for A. actinomycetemcomitans by determining the genes in its genome that cannot be mutated. As for the genes that can be mutated, we archived these mutants into a library, which we used to find genes that contribute to antibiotic resistance, leading us to discover that antibiotics cause A. actinomycetemcomitans to form biofilms. We then devised an approach to find genes that mediate this process and confirmed 4 genes. These results illuminate new fundamental traits of a human pathogen.
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Kazmierczak T, Nagymihály M, Lamouche F, Barrière Q, Guefrachi I, Alunni B, Ouadghiri M, Ibijbijen J, Kondorosi É, Mergaert P, Gruber V. Specific Host-Responsive Associations Between Medicago truncatula Accessions and Sinorhizobium Strains. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2017; 30:399-409. [PMID: 28437159 DOI: 10.1094/mpmi-01-17-0009-r] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
Legume plants interact with rhizobia to form nitrogen-fixing root nodules. Legume-rhizobium interactions are specific and only compatible rhizobia and plant species will lead to nodule formation. Even within compatible interactions, the genotype of both the plant and the bacterial symbiont will impact on the efficiency of nodule functioning and nitrogen-fixation activity. The model legume Medicago truncatula forms nodules with several species of the Sinorhizobium genus. However, the efficiency of these bacterial strains is highly variable. In this study, we compared the symbiotic efficiency of Sinorhizobium meliloti strains Sm1021, 102F34, and FSM-MA, and Sinorhizobium medicae strain WSM419 on the two widely used M. truncatula accessions A17 and R108. The efficiency of the interactions was determined by multiple parameters. We found a high effectiveness of the FSM-MA strain with both M. truncatula accessions. In contrast, specific highly efficient interactions were obtained for the A17-WSM419 and R108-102F34 combinations. Remarkably, the widely used Sm1021 strain performed weakly on both hosts. We showed that Sm1021 efficiently induced nodule organogenesis but cannot fully activate the differentiation of the symbiotic nodule cells, explaining its weaker performance. These results will be informative for the selection of appropriate rhizobium strains in functional studies on symbiosis using these M. truncatula accessions, particularly for research focusing on late stages of the nodulation process.
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Affiliation(s)
- Théophile Kazmierczak
- 1 Institute of Plant Sciences Paris Saclay IPS2, CNRS, INRA, Université Paris-Sud, Université Evry, Université Paris-Saclay, Bâtiment 630, 91405 Orsay, France. Institute of Plant Sciences Paris-Saclay IPS2, Université Paris Diderot, Sorbonne Paris-Cité, Bâtiment 630, 91405, Orsay, France
| | - Marianna Nagymihály
- 2 Institute for Integrative Biology of the Cell, UMR 9198, CNRS/Université Paris-Sud/CEA, 91198, Gif-sur-Yvette, France
- 3 Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, 6726 Szeged, Hungary
| | - Florian Lamouche
- 2 Institute for Integrative Biology of the Cell, UMR 9198, CNRS/Université Paris-Sud/CEA, 91198, Gif-sur-Yvette, France
| | - Quentin Barrière
- 2 Institute for Integrative Biology of the Cell, UMR 9198, CNRS/Université Paris-Sud/CEA, 91198, Gif-sur-Yvette, France
| | - Ibtissem Guefrachi
- 2 Institute for Integrative Biology of the Cell, UMR 9198, CNRS/Université Paris-Sud/CEA, 91198, Gif-sur-Yvette, France
| | - Benoit Alunni
- 2 Institute for Integrative Biology of the Cell, UMR 9198, CNRS/Université Paris-Sud/CEA, 91198, Gif-sur-Yvette, France
| | - Mouna Ouadghiri
- 4 Collections Coordonnées Marocaines de Microorganismes et Laboratoire de Microbiologie et Biologie Moléculaire, Centre National pour la Recherche Scientifique et Technique, Rabat, Maroc; and
| | - Jamal Ibijbijen
- 5 Faculté des Sciences, Université Moulay Ismail, Meknès, Maroc, Faculté des Sciences, Université Moulay Ismail, BP 11201 Zitoune, Meknès, Maroc
| | - Éva Kondorosi
- 2 Institute for Integrative Biology of the Cell, UMR 9198, CNRS/Université Paris-Sud/CEA, 91198, Gif-sur-Yvette, France
- 3 Institute of Biochemistry, Biological Research Centre, Hungarian Academy of Sciences, 6726 Szeged, Hungary
| | - Peter Mergaert
- 2 Institute for Integrative Biology of the Cell, UMR 9198, CNRS/Université Paris-Sud/CEA, 91198, Gif-sur-Yvette, France
| | - Véronique Gruber
- 1 Institute of Plant Sciences Paris Saclay IPS2, CNRS, INRA, Université Paris-Sud, Université Evry, Université Paris-Saclay, Bâtiment 630, 91405 Orsay, France. Institute of Plant Sciences Paris-Saclay IPS2, Université Paris Diderot, Sorbonne Paris-Cité, Bâtiment 630, 91405, Orsay, France
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140
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de Vries SP, Gupta S, Baig A, Wright E, Wedley A, Jensen AN, Lora LL, Humphrey S, Skovgård H, Macleod K, Pont E, Wolanska DP, L'Heureux J, Mobegi FM, Smith DGE, Everest P, Zomer A, Williams N, Wigley P, Humphrey T, Maskell DJ, Grant AJ. Genome-wide fitness analyses of the foodborne pathogen Campylobacter jejuni in in vitro and in vivo models. Sci Rep 2017; 7:1251. [PMID: 28455506 PMCID: PMC5430854 DOI: 10.1038/s41598-017-01133-4] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/16/2016] [Accepted: 03/27/2017] [Indexed: 01/22/2023] Open
Abstract
Campylobacter is the most common cause of foodborne bacterial illness worldwide. Faecal contamination of meat, especially chicken, during processing represents a key route of transmission to humans. There is a lack of insight into the mechanisms driving C. jejuni growth and survival within hosts and the environment. Here, we report a detailed analysis of C. jejuni fitness across models reflecting stages in its life cycle. Transposon (Tn) gene-inactivation libraries were generated in three C. jejuni strains and the impact on fitness during chicken colonisation, survival in houseflies and under nutrient-rich and -poor conditions at 4 °C and infection of human gut epithelial cells was assessed by Tn-insertion site sequencing (Tn-seq). A total of 331 homologous gene clusters were essential for fitness during in vitro growth in three C. jejuni strains, revealing that a large part of its genome is dedicated to growth. We report novel C. jejuni factors essential throughout its life cycle. Importantly, we identified genes that fulfil important roles across multiple conditions. Our comprehensive screens showed which flagella elements are essential for growth and which are vital to the interaction with host organisms. Future efforts should focus on how to exploit this knowledge to effectively control infections caused by C. jejuni.
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Affiliation(s)
- Stefan P de Vries
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Srishti Gupta
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Abiyad Baig
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
- School of Veterinary Medicine and Science, University of Nottingham, Sutton Bonnington, Leicestershire, United Kingdom
| | - Elli Wright
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Leahurst Campus, Neston, United Kingdom
| | - Amy Wedley
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Leahurst Campus, Neston, United Kingdom
| | | | - Lizeth LaCharme Lora
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Leahurst Campus, Neston, United Kingdom
| | - Suzanne Humphrey
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Leahurst Campus, Neston, United Kingdom
- Institute of Infection, Immunity and Inflammation, University of Glasgow, Glasgow, United Kingdom
| | - Henrik Skovgård
- Department of Agroecology, University of Aarhus, Slagelse, Denmark
| | - Kareen Macleod
- University of Glasgow, Veterinary School, Glasgow, United Kingdom
| | - Elsa Pont
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Dominika P Wolanska
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Joanna L'Heureux
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Fredrick M Mobegi
- Department of Paediatric Infectious Diseases, Radboud Institute for Molecular Life Sciences, Radboud University Medical Centre, Nijmegen, The Netherlands
- Division of Molecular Carcinogenesis, The Netherlands Cancer Institute, Amsterdam, The Netherlands
| | - David G E Smith
- Heriot-Watt University, School of Life Sciences, Edinburgh, Scotland, United Kingdom
| | - Paul Everest
- University of Glasgow, Veterinary School, Glasgow, United Kingdom
| | - Aldert Zomer
- Department of Infectious Diseases and Immunology, Faculty of Veterinary Medicine, Utrecht University, Utrecht, The Netherlands
| | - Nicola Williams
- Department of Epidemiology and Population Health, Institute of Infection and Global Health, University of Liverpool, Leahurst Campus, Neston, United Kingdom
| | - Paul Wigley
- Department of Infection Biology, Institute of Infection and Global Health, University of Liverpool, Leahurst Campus, Neston, United Kingdom
| | - Thomas Humphrey
- School of Medicine, Institute of Life Sciences, Swansea University, Swansea, United Kingdom
| | - Duncan J Maskell
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom
| | - Andrew J Grant
- Department of Veterinary Medicine, University of Cambridge, Cambridge, United Kingdom.
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141
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Suzuki S, Kaidow A, Meya T, Masuya A, Shiina T. Phenotypic difference between Δ(srl-recA)306 and ΔrecA::Km elucidated by next-generation sequencing combined with a long-PCR system. J GEN APPL MICROBIOL 2017; 63:22-27. [PMID: 27990000 DOI: 10.2323/jgam.2016.07.002] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
Many significant gene mutations in E. coli have contributed to the development of genetics. Among these, a commonly used recA mutation, Δ(srl-recA)306 has been sequenced by a next-generation sequencer combined with a long PCR. An original report described that Δ(srl-recA)306 cells were deleted from srlR to recA genes in their genome. The next-generation sequencer enables more accurate details to be determined. We ask whether both surrounding genes from hypF to norV for srlR and alaS for recA is there first. The long PCR was carried out with primers, norR and alaS, and amplified DNA fragments differed in length from wild to Δ(srl-recA)306 cells, suggesting that an entire Δ(srl-recA)306 mutation was included. Sequences of those DNA fragments indicated that 9147 bp, from srlR to recA including 10 genes, were replaced by a Tn10 DNA sequence. Junction points at both srlR-Tn10 and Tn10-recA were determined precisely. The results indicate that the first 97% of recA gene sequences were lost with a downstream recX gene remaining intact. The phenotypic difference between Δ(srl-recA)306 and ΔrecA::Km is discussed.
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Affiliation(s)
- Shingo Suzuki
- Department of Molecular Life Science, Division of Basic Medical Science and Molecular Medicine, Tokai University School of Medicine
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142
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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: 1.1] [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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143
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Bii VM, Trobridge GD. Identifying Cancer Driver Genes Using Replication-Incompetent Retroviral Vectors. Cancers (Basel) 2016; 8:cancers8110099. [PMID: 27792127 PMCID: PMC5126759 DOI: 10.3390/cancers8110099] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/20/2016] [Revised: 10/12/2016] [Accepted: 10/17/2016] [Indexed: 12/16/2022] Open
Abstract
Identifying novel genes that drive tumor metastasis and drug resistance has significant potential to improve patient outcomes. High-throughput sequencing approaches have identified cancer genes, but distinguishing driver genes from passengers remains challenging. Insertional mutagenesis screens using replication-incompetent retroviral vectors have emerged as a powerful tool to identify cancer genes. Unlike replicating retroviruses and transposons, replication-incompetent retroviral vectors lack additional mutagenesis events that can complicate the identification of driver mutations from passenger mutations. They can also be used for almost any human cancer due to the broad tropism of the vectors. Replication-incompetent retroviral vectors have the ability to dysregulate nearby cancer genes via several mechanisms including enhancer-mediated activation of gene promoters. The integrated provirus acts as a unique molecular tag for nearby candidate driver genes which can be rapidly identified using well established methods that utilize next generation sequencing and bioinformatics programs. Recently, retroviral vector screens have been used to efficiently identify candidate driver genes in prostate, breast, liver and pancreatic cancers. Validated driver genes can be potential therapeutic targets and biomarkers. In this review, we describe the emergence of retroviral insertional mutagenesis screens using replication-incompetent retroviral vectors as a novel tool to identify cancer driver genes in different cancer types.
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Affiliation(s)
- Victor M Bii
- College of Pharmacy, Washington State University, WSU Spokane PBS 323, P.O. Box 1495, Spokane, WA 99210, USA.
| | - Grant D Trobridge
- College of Pharmacy, Washington State University, WSU Spokane PBS 323, P.O. Box 1495, Spokane, WA 99210, USA.
- School of Molecular Biosciences, Washington State University, Pullman, WA 99164, USA.
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144
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Blanchard AM, Egan SA, Emes RD, Warry A, Leigh JA. PIMMS (Pragmatic Insertional Mutation Mapping System) Laboratory Methodology a Readily Accessible Tool for Identification of Essential Genes in Streptococcus. Front Microbiol 2016; 7:1645. [PMID: 27826289 PMCID: PMC5078762 DOI: 10.3389/fmicb.2016.01645] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2016] [Accepted: 10/03/2016] [Indexed: 12/27/2022] Open
Abstract
The Pragmatic Insertional Mutation Mapping (PIMMS) laboratory protocol was developed alongside various bioinformatics packages (Blanchard et al., 2015) to enable detection of essential and conditionally essential genes in Streptococcus and related bacteria. This extended the methodology commonly used to locate insertional mutations in individual mutants to the analysis of mutations in populations of bacteria. In Streptococcus uberis, a pyogenic Streptococcus associated with intramammary infection and mastitis in ruminants, the mutagen pGhost9:ISS1 was shown to integrate across the entire genome. Analysis of >80,000 mutations revealed 196 coding sequences, which were not be mutated and a further 67 where mutation only occurred beyond the 90th percentile of the coding sequence. These sequences showed good concordance with sequences within the database of essential genes and typically matched sequences known to be associated with basic cellular functions. Due to the broad utility of this mutagen and the simplicity of the methodology it is anticipated that PIMMS will be of value to a wide range of laboratories in functional genomic analysis of a wide range of Gram positive bacteria (Streptococcus, Enterococcus, and Lactococcus) of medical, veterinary, and industrial significance.
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Affiliation(s)
- Adam M Blanchard
- School of Veterinary Medicine and Science, University of Nottingham Sutton Bonington, UK
| | - Sharon A Egan
- School of Veterinary Medicine and Science, University of Nottingham Sutton Bonington, UK
| | - Richard D Emes
- School of Veterinary Medicine and Science, University of NottinghamSutton Bonington, UK; Advanced Data Analysis Centre, University of NottinghamSutton Bonington, UK
| | - Andrew Warry
- Advanced Data Analysis Centre, University of Nottingham Sutton Bonington, UK
| | - James A Leigh
- School of Veterinary Medicine and Science, University of Nottingham Sutton Bonington, UK
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145
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Freed NE, Bumann D, Silander OK. Combining Shigella Tn-seq data with gold-standard E. coli gene deletion data suggests rare transitions between essential and non-essential gene functionality. BMC Microbiol 2016; 16:203. [PMID: 27599549 PMCID: PMC5011829 DOI: 10.1186/s12866-016-0818-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2016] [Accepted: 08/19/2016] [Indexed: 01/02/2023] Open
Abstract
BACKGROUND Gene essentiality - whether or not a gene is necessary for cell growth - is a fundamental component of gene function. It is not well established how quickly gene essentiality can change, as few studies have compared empirical measures of essentiality between closely related organisms. RESULTS Here we present the results of a Tn-seq experiment designed to detect essential protein coding genes in the bacterial pathogen Shigella flexneri 2a 2457T on a genome-wide scale. Superficial analysis of this data suggested that 481 protein-coding genes in this Shigella strain are critical for robust cellular growth on rich media. Comparison of this set of genes with a gold-standard data set of essential genes in the closely related Escherichia coli K12 BW25113 revealed that an excessive number of genes appeared essential in Shigella but non-essential in E. coli. Importantly, and in converse to this comparison, we found no genes that were essential in E. coli and non-essential in Shigella, implying that many genes were artefactually inferred as essential in Shigella. Controlling for such artefacts resulted in a much smaller set of discrepant genes. Among these, we identified three sets of functionally related genes, two of which have previously been implicated as critical for Shigella growth, but which are dispensable for E. coli growth. CONCLUSIONS The data presented here highlight the small number of protein coding genes for which we have strong evidence that their essentiality status differs between the closely related bacterial taxa E. coli and Shigella. A set of genes involved in acetate utilization provides a canonical example. These results leave open the possibility of developing strain-specific antibiotic treatments targeting such differentially essential genes, but suggest that such opportunities may be rare in closely related bacteria.
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Affiliation(s)
- Nikki E Freed
- Institute of Natural and Mathematical Sciences, Massey University, Auckland, New Zealand.,Infection Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Dirk Bumann
- Infection Biology, Biozentrum, University of Basel, Basel, Switzerland
| | - Olin K Silander
- Institute of Natural and Mathematical Sciences, Massey University, Auckland, New Zealand. .,Computational and Systems Biology, Biozentrum, University of Basel, Basel, Switzerland.
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146
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Abstract
UNLABELLED Transposon insertion sequencing (TIS; also known as TnSeq) is a potent approach commonly used to comprehensively define the genetic loci that contribute to bacterial fitness in diverse environments. A key presumption underlying analyses of TIS datasets is that loci with a low frequency of transposon insertions contribute to fitness. However, it is not known whether factors such as nucleoid binding proteins can alter the frequency of transposon insertion and thus whether TIS output may systematically reflect factors that are independent of the role of the loci in fitness. Here, we investigated whether the histone-like nucleoid structuring (H-NS) protein, which preferentially associates with AT-rich sequences, modulates the frequency of Mariner transposon insertion in the Vibrio cholerae genome, using comparative analysis of TIS results from wild-type (wt) and Δhns V. cholerae strains. These analyses were overlaid on gene classification based on GC content as well as on extant genome-wide identification of H-NS binding loci. Our analyses revealed a significant dearth of insertions within AT-rich loci in wt V. cholerae that was not apparent in the Δhns insertion library. Additionally, we observed a striking correlation between genetic loci that are overrepresented in the Δhns insertion library relative to their insertion frequency in wt V. cholerae and loci previously found to physically interact with H-NS. Collectively, our findings reveal that factors other than genetic fitness can systematically modulate the frequency of transposon insertions in TIS studies and add a cautionary note to interpretation of TIS data, particularly for AT-rich sequences. IMPORTANCE Transposon insertion sequencing (TIS) is often used to assess the relative frequency with which genetic loci can be disrupted, which is taken as an indicator of their importance for bacterial fitness. Here, we report that biological factors other than the relative levels of fitness of insertion mutants can influence TIS output. We found that the presence of the DNA binding protein H-NS, which preferentially recognizes AT-rich sequences, is linked to significant underrepresentation of mutations within AT-rich loci in transposon insertion libraries. Furthermore, there is a marked correspondence between loci bound by H-NS and loci with an increased frequency of disruption in a Δhns insertion library relative to a wt library. Our data suggest that factors other than genetic fitness (e.g., DNA binding proteins such as H-NS) can systematically modulate the frequency of transposon insertions in TIS studies and add a note of caution for interpretation of TIS data.
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