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Pigula M, Lai YC, Koh M, Diercks CS, Rogers TF, Dik DA, Schultz PG. An unnatural amino acid dependent, conditional Pseudomonas vaccine prevents bacterial infection. Nat Commun 2024; 15:6766. [PMID: 39117651 PMCID: PMC11310302 DOI: 10.1038/s41467-024-50843-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2024] [Accepted: 07/22/2024] [Indexed: 08/10/2024] Open
Abstract
Live vaccines are ideal for inducing immunity but suffer from the need to attenuate their pathogenicity or replication to preclude the possibility of escape. Unnatural amino acids (UAAs) provide a strategy to engineer stringent auxotrophies, yielding conditionally replication incompetent live bacteria with excellent safety profiles. Here, we engineer Pseudomonas aeruginosa to maintain auxotrophy for the UAA p-benzoyl-L-phenylalanine (BzF) through its incorporation into the essential protein DnaN. In vivo evolution using an Escherichia coli-based two-hybrid selection system enabled engineering of a mutant DnaN homodimeric interface completely dependent on a BzF-specific interaction. This engineered strain, Pa Vaccine, exhibits undetectable escape frequency (<10-11) and shows excellent safety in naïve mice. Animals vaccinated via intranasal or intraperitoneal routes are protected from lethal challenge with pathogenic P. aeruginosa PA14. These results establish UAA-auxotrophic bacteria as promising candidates for bacterial vaccine therapy and outline a platform for expanding this technology to diverse bacterial pathogens.
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Affiliation(s)
- Michael Pigula
- Department of Chemistry, Scripps Research, La Jolla, CA, USA
| | - Yen-Chung Lai
- Department of Immunology and Microbiology, Scripps Research, La Jolla, CA, USA
- Division of Infectious Diseases, Department of Medicine, University of California, San Diego, La Jolla, CA, USA
| | - Minseob Koh
- Department of Chemistry, Pusan National University, Busan, Korea
| | | | - Thomas F Rogers
- Department of Immunology and Microbiology, Scripps Research, La Jolla, CA, USA
- Division of Infectious Diseases, Department of Medicine, University of California, San Diego, La Jolla, CA, USA
| | - David A Dik
- Department of Biology, Calibr-Skaggs Institute for Innovative Medicines, Scripps Research, La Jolla, CA, USA.
| | - Peter G Schultz
- Department of Chemistry, Scripps Research, La Jolla, CA, USA.
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2
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Robertson SN, Romero M, Fenn S, Kohler Riedi PL, Cámara M. Development, characterization, and evaluation of a simple polymicrobial colony biofilm model for testing of antimicrobial wound dressings. J Appl Microbiol 2024; 135:lxae042. [PMID: 38366933 DOI: 10.1093/jambio/lxae042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Revised: 01/12/2024] [Accepted: 02/15/2024] [Indexed: 02/19/2024]
Abstract
Chronic wound infections are generally of polymicrobial nature with aerobic and anaerobic bacteria, as well as fungi frequently observed in them. Wound treatment involves a series of steps, including debridement of the wound, flushing, and often the use of multiple wound dressings many of which are antimicrobial. Yet, many wound dressings are tested versus single species of planktonic microbes, which fails to mirror the real-life presence of biofilms. AIMS Simple biofilm models are the first step to testing of any antimicrobial and wound dressing; therefore, the aim of this study was to develop and validate a simple polymicrobial colony biofilm wound model comprised of Pseudomonas aeruginosa, Staphylococcus aureus, and Candida albicans on RPMI-1640 agar. The model was then used to evaluate the topical disinfectant chlorohexidine and four commercially available wound dressings using the polymicrobial model. The model used was as a starting point to mimic debridement in clinical care of wounds and the effectiveness of wound dressings evaluated afterwards. METHODS AND RESULTS Planktonic assessment using AATCC100-2004 demonstrated that all antimicrobial wound dressings reduced the planktonic microbial burden below the limit of detection; however, when challenged with polymicrobial colony biofilms, silver wound dressings showed limited effectiveness (1-2 log CFU reductions). In contrast, a single iodine releasing wound dressing showed potent antibiofilm activity reducing all species CFUs below the limit of detection (>6-10 log) depending on the species. A disrupted biofilm model challenge was performed to represent the debridement of a wound and wound silver-based wound dressings were found to be marginally more effective than in whole colony biofilm challenges while the iodine containing wound dressing reduced microbial recovery below the limit of detection. CONCLUSIONS In this model, silver dressings were ineffective versus the whole colony biofilms but showed some recovery of activity versus the disrupted colony biofilm. The iodine wound dressing reduced the viability of all species below the level of detection. This suggests that mode of action of wound dressing should be considered for the type of biofilm challenge as should the clinical use, e.g. debridement.
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Affiliation(s)
- Shaun N Robertson
- National Biofilms Innovation Centre, School of Life Sciences, Biodiscovery Institute, University of Nottingham, NG7 2RD Nottingham, United Kingdom
| | - Manuel Romero
- National Biofilms Innovation Centre, School of Life Sciences, Biodiscovery Institute, University of Nottingham, NG7 2RD Nottingham, United Kingdom
- Department of Microbiology and Parasitology, Faculty of Biology-CIBUS, Universidade de Santiago de Compostela, Santiago de Compostela 15782, Spain
- Aquatic One Health Research Center (ARCUS), Universidade de Santiago de Compostela, Santiago de Compostela 15782, Spain
| | - Samuel Fenn
- National Biofilms Innovation Centre, School of Life Sciences, Biodiscovery Institute, University of Nottingham, NG7 2RD Nottingham, United Kingdom
- Schools of Microbiology and Medicine, University College Cork, and APC Microbiome Ireland, Cork T12 TP07, Ireland
| | | | - Miguel Cámara
- National Biofilms Innovation Centre, School of Life Sciences, Biodiscovery Institute, University of Nottingham, NG7 2RD Nottingham, United Kingdom
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3
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Shrestha A, Limay-Rios V, Brettingham DJL, Raizada MN. Maize pollen carry bacteria that suppress a fungal pathogen that enters through the male gamete fertilization route. FRONTIERS IN PLANT SCIENCE 2024; 14:1286199. [PMID: 38269134 PMCID: PMC10806238 DOI: 10.3389/fpls.2023.1286199] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 08/31/2023] [Accepted: 12/20/2023] [Indexed: 01/26/2024]
Abstract
In flowering plants, after being released from pollen grains, the male gametes use the style channel to migrate towards the ovary where they fertilize awaiting eggs. Environmental pathogens exploit the style passage, resulting in diseased progeny seed. The belief is that pollen also transmits pathogens into the style. By contrast, we hypothesized that pollen carries beneficial microbes that suppress environmental pathogens on the style passage. No prior studies have reported pollen-associated bacterial functions in any plant species. Here, bacteria were cultured from maize (corn) pollen encompassing wild ancestors and farmer-selected landraces from across the Americas, grown in a common field in Canada for one season. In total, 298 bacterial isolates were cultured, spanning 45 genera, 103 species, and 88 OTUs, dominated by Pantoea, Bacillus, Pseudomonas, Erwinia, and Microbacterium. Full-length 16S DNA-based taxonomic profiling showed that 78% of bacterial taxa from the major wild ancestor of maize (Parviglumis teosinte) were present in at least one cultivated landrace. The species names of the bacterial isolates were used to search the pathogen literature systematically; this preliminary evidence predicted that the vast majority of the pollen-associated bacteria analyzed are not maize pathogens. The pollen-associated bacteria were tested in vitro against a style-invading Fusarium pathogen shown to cause Gibberella ear rot (GER): 14 isolates inhibited this pathogen. Genome mining showed that all the anti-Fusarium bacterial species encode phzF, associated with biosynthesis of the natural fungicide, phenazine. To mimic the male gamete migration route, three pollen-associated bacterial strains were sprayed onto styles (silks), followed by Fusarium inoculation; these bacteria reduced GER symptoms and mycotoxin accumulation in progeny seed. Confocal microscopy was used to search for direct evidence that pollen-associated bacteria can defend living silks against Fusarium graminearum (Fg); bacterial strain AS541 (Kluyvera intermedia), isolated from pollen of ancestral Parviglumis, was observed to colonize the susceptible style/silk entry points of Fg (silk epidermis, trichomes, wounds). Furthermore, on style/silk tissue, AS541 colonized/aggregated on Fg hyphae, and was associated with Fg hyphal breaks. These results suggest that pollen has the potential to carry bacteria that can defend the style/silk passage against an environmental pathogen - a novel observation.
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Affiliation(s)
- Anuja Shrestha
- Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada
| | - Victor Limay-Rios
- Department of Plant Agriculture, University of Guelph, Ridgetown, ON, Canada
| | | | - Manish N. Raizada
- Department of Plant Agriculture, University of Guelph, Guelph, ON, Canada
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4
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Smith P, Schuster M. The fitness benefit of pyoverdine cross-feeding by Pseudomonas protegens Pf-5. Environ Microbiol 2024; 26:e16554. [PMID: 38097191 DOI: 10.1111/1462-2920.16554] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2023] [Accepted: 11/24/2023] [Indexed: 12/20/2023]
Abstract
Under iron-limiting conditions, fluorescent pseudomonads acquire iron from the environment by secreting strain-specific, iron-chelating siderophores termed pyoverdines (PVD). The rhizosphere bacterium Pseudomonas protegens Pf-5 produces its own PVD but also can cross-feed on PVDs produced by other species. Previous work has found that Pf-5 continues to produce its own PVD when allowed to cross-feed, raising questions about the benefit of heterologous PVD utilisation. Here, we investigate this question using a defined, unidirectional P. protegens Pf-5/Pseudomonas aeruginosa PAO1 cross-feeding model. Quantifying the production of PVD in the presence of heterologous PVD produced by PAO1, we show that cross-feeding Pf-5 strains reduce the production of their own PVD, while non-cross-feeding Pf-5 strains increase the production of PVD. Measuring the fitness of cross-feeding and non-cross-feeding Pf-5 strains in triple coculture with PAO1, we find that cross-feeding provides a fitness benefit to Pf-5 when the availability of heterologous PVD is high. We conclude that cross-feeding can reduce the costs of self-PVD production and may thus aid in the colonisation of iron-limited environments that contain compatible siderophores produced by other resident microbes. Taken together, these results expand our understanding of the mechanisms of interspecific competition for iron in microbial communities.
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Affiliation(s)
- Parker Smith
- Department of Microbiology, Oregon State University, Corvallis, Oregon, USA
| | - Martin Schuster
- Department of Microbiology, Oregon State University, Corvallis, Oregon, USA
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5
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Sanow S, Kuang W, Schaaf G, Huesgen P, Schurr U, Roessner U, Watt M, Arsova B. Molecular Mechanisms of Pseudomonas-Assisted Plant Nitrogen Uptake: Opportunities for Modern Agriculture. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2023; 36:536-548. [PMID: 36989040 DOI: 10.1094/mpmi-10-22-0223-cr] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/19/2023]
Abstract
Pseudomonas spp. make up 1.6% of the bacteria in the soil and are found throughout the world. More than 140 species of this genus have been identified, some beneficial to the plant. Several species in the family Pseudomonadaceae, including Azotobacter vinelandii AvOP, Pseudomonas stutzeri A1501, Pseudomonas stutzeri DSM4166, Pseudomonas szotifigens 6HT33bT, and Pseudomonas sp. strain K1 can fix nitrogen from the air. The genes required for these reactions are organized in a nitrogen fixation island, obtained via horizontal gene transfer from Klebsiella pneumoniae, Pseudomonas stutzeri, and Azotobacter vinelandii. Today, this island is conserved in Pseudomonas spp. from different geographical locations, which, in turn, have evolved to deal with different geo-climatic conditions. Here, we summarize the molecular mechanisms behind Pseudomonas-driven plant growth promotion, with particular focus on improving plant performance at limiting nitrogen (N) and improving plant N content. We describe Pseudomonas-plant interaction strategies in the soil, noting that the mechanisms of denitrification, ammonification, and secondary metabolite signaling are only marginally explored. Plant growth promotion is dependent on the abiotic conditions and differs at sufficient and deficient N. The molecular controls behind different plant responses are not fully elucidated. We suggest that superposition of transcriptome, proteome, and metabolome data and their integration with plant phenotype development through time will help fill these gaps. The aim of this review is to summarize the knowledge behind Pseudomonas-driven nitrogen fixation and to point to possible agricultural solutions. [Formula: see text] Copyright © 2023 The Author(s). This is an open access article distributed under the CC BY 4.0 International license.
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Affiliation(s)
- Stefan Sanow
- Institute for Bio- and Geosciences, Plant Sciences (IBG-2), Forschungszentrum Juelich GmbH, Germany
- School of BioSciences, Faculty of Science, The University of Melbourne, Parkville, 3010 Victoria, Australia
| | - Weiqi Kuang
- College of life and Environmental Sciences, Hunan University of Arts and Science, China
| | - Gabriel Schaaf
- Institute of Crop Science and Resource Conservation, University of Bonn, 53115 Bonn, Germany
| | - Pitter Huesgen
- Central institute for Engineering, Electronics and Analytics (ZEA-3), Forschungszentrum Juelich GmbH, Germany
| | - Ulrich Schurr
- Institute for Bio- and Geosciences, Plant Sciences (IBG-2), Forschungszentrum Juelich GmbH, Germany
| | - Ute Roessner
- Research School of Biology, The Australian National University, Acton, 2601 Australian Capital Territory, Australia
| | - Michelle Watt
- School of BioSciences, Faculty of Science, The University of Melbourne, Parkville, 3010 Victoria, Australia
| | - Borjana Arsova
- Institute for Bio- and Geosciences, Plant Sciences (IBG-2), Forschungszentrum Juelich GmbH, Germany
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Bhattacharyya A, Mavrodi O, Bhowmik N, Weller D, Thomashow L, Mavrodi D. Bacterial biofilms as an essential component of rhizosphere plant-microbe interactions. METHODS IN MICROBIOLOGY 2023; 53:3-48. [PMID: 38415193 PMCID: PMC10898258 DOI: 10.1016/bs.mim.2023.05.006] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/29/2024]
Affiliation(s)
- Ankita Bhattacharyya
- School of Biological, Environmental and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
| | - Olga Mavrodi
- School of Biological, Environmental and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
| | - Niladri Bhowmik
- School of Biological, Environmental and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
| | - David Weller
- USDA-ARS Wheat Health, Genetics and Quality Research Unit, Pullman, WA, United States
| | - Linda Thomashow
- USDA-ARS Wheat Health, Genetics and Quality Research Unit, Pullman, WA, United States
| | - Dmitri Mavrodi
- School of Biological, Environmental and Earth Sciences, The University of Southern Mississippi, Hattiesburg, MS, United States
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Abstract
Quorum sensing is described as a widespread cell density-dependent signaling mechanism in bacteria. Groups of cells coordinate gene expression by secreting and responding to diffusible signal molecules. Theory, however, predicts that individual cells may short-circuit this mechanism by directly responding to the signals they produce irrespective of cell density. In this study, we characterize this self-sensing effect in the acyl-homoserine lactone quorum sensing system of Pseudomonas aeruginosa. We show that antiactivators, a set of proteins known to affect signal sensitivity, function to prevent self-sensing. Measuring quorum-sensing gene expression in individual cells at very low densities, we find that successive deletion of antiactivator genes qteE and qslA produces a bimodal response pattern, in which increasing proportions of constitutively induced cells coexist with uninduced cells. Comparing responses of signal-proficient and -deficient cells in cocultures, we find that signal-proficient cells show a much higher response in the antiactivator mutant background but not in the wild-type background. Our results experimentally demonstrate the antiactivator-dependent transition from group- to self-sensing in the quorum-sensing circuitry of P. aeruginosa. Taken together, these findings extend our understanding of the functional capacity of quorum sensing. They highlight the functional significance of antiactivators in the maintenance of group-level signaling and experimentally prove long-standing theoretical predictions.
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8
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The Wsp system of Pseudomonas aeruginosa links surface sensing and cell envelope stress. Proc Natl Acad Sci U S A 2022; 119:e2117633119. [PMID: 35476526 PMCID: PMC9170161 DOI: 10.1073/pnas.2117633119] [Citation(s) in RCA: 29] [Impact Index Per Article: 14.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023] Open
Abstract
SignificanceBacteria must respond quickly to environmental changes to survive. One way bacteria can respond to environmental stress is by undergoing a lifestyle transition from individual, free-swimming cells to a surface-associated community called a biofilm characterized by aggregative growth. The opportunistic pathogen Pseudomonas aeruginosa uses the Wsp chemosensory system to sense an unknown surface-associated cue. Here we show that the Wsp system senses cell envelope stress, specifically conditions that promote unfolded or misregulated periplasmic and inner membrane proteins. This work provides direct evidence that cell envelope stress is an important feature of surface sensing in P. aeruginosa.
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9
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Smith P, Schuster M. Inexpensive Apparatus for High-Quality Imaging of Microbial Growth on Agar Plates. Front Microbiol 2021; 12:689476. [PMID: 34276620 PMCID: PMC8278329 DOI: 10.3389/fmicb.2021.689476] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Accepted: 06/07/2021] [Indexed: 11/15/2022] Open
Abstract
The ability to capture images of results or processes is an important tool in the biologist’s tool kit. In microbiology, capturing high-quality images of microbial growth on agar plates is difficult due to the reflective surface of the plates and limitations in common photography techniques. Equipment is available to overcome these challenges, but acquisition costs are high. We have developed and tested an inexpensive and efficient apparatus for high-quality imaging of microbial colonies. The imaging box, as we have named the apparatus, is designed to eliminate glare and reduce reflections on the surface of the plate while providing uniform, diffuse light from all sides. The imaging box was used to capture hundreds of images in research and teaching lab settings.
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Affiliation(s)
- Parker Smith
- Department of Microbiology, Oregon State University, Corvallis, OR, United States
| | - Martin Schuster
- Department of Microbiology, Oregon State University, Corvallis, OR, United States
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10
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Petch JE, Gurnani P, Yilmaz G, Mastrotto F, Alexander C, Heeb S, Cámara M, Mantovani G. Combining Inducible Lectin Expression and Magnetic Glyconanoparticles for the Selective Isolation of Bacteria from Mixed Populations. ACS APPLIED MATERIALS & INTERFACES 2021; 13:19230-19243. [PMID: 33852268 DOI: 10.1021/acsami.1c00907] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/12/2023]
Abstract
The selective isolation of bacteria from mixed populations has been investigated in varied applications ranging from differential pathogen identification in medical diagnostics and food safety to the monitoring of microbial stress dynamics in industrial bioreactors. Selective isolation techniques are generally limited to the confinement of small populations in defined locations, may be unable to target specific bacteria, or rely on immunomagnetic separation, which is not universally applicable. In this proof-of-concept work, we describe a novel strategy combining inducible bacterial lectin expression with magnetic glyconanoparticles (MGNPs) as a platform technology to enable selective bacterial isolation from cocultures. An inducible mutant of the type 1 fimbriae, displaying the mannose-specific lectin FimH, was constructed in Escherichia coli allowing for "on-demand" glycan-binding protein presentation following external chemical stimulation. Binding to glycopolymers was only observed upon fimbrial induction and was specific for mannosylated materials. A library of MGNPs was produced via the grafting of well-defined catechol-terminal glycopolymers prepared by reversible addition-fragmentation chain transfer (RAFT) polymerization to magnetic nanoparticles. Thermal analysis revealed high functionalization (≥85% polymer by weight). Delivery of MGNPs to cocultures of fluorescently labeled bacteria followed by magnetic extraction resulted in efficient depletion of type 1 fimbriated target cells from wild-type or afimbriate E. coli. Extraction efficiency was found to be dependent on the molecular weight of the glycopolymers utilized to engineer the nanoparticles, with MGNPs decorated with shorter Dopa-(ManAA)50 mannosylated glycopolymers found to perform better than those assembled from a longer Dopa-(ManAA)200 analogue. The extraction efficiency of fimbriated E. coli was also improved when the counterpart strain did not harbor the genetic apparatus for the expression of the type 1 fimbriae. Overall, this work suggests that the modulation of the genetic apparatus encoding bacterial surface-associated lectins coupled with capture through MGNPs could be a versatile tool for the extraction of bacteria from mixed populations.
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Affiliation(s)
- Joshua E Petch
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, U.K
- Nottingham University Biodiscovery Institute, National Biofilms Innovation Centre, School of Life Sciences, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Pratik Gurnani
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Gokhan Yilmaz
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Francesca Mastrotto
- Department of Pharmaceutical and Pharmacological Sciences, University of Padova, Via F. Marzolo 5, 35131 Padova, Italy
| | - Cameron Alexander
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Stephan Heeb
- Nottingham University Biodiscovery Institute, National Biofilms Innovation Centre, School of Life Sciences, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Miguel Cámara
- Nottingham University Biodiscovery Institute, National Biofilms Innovation Centre, School of Life Sciences, University of Nottingham, Nottingham NG7 2RD, U.K
| | - Giuseppe Mantovani
- Division of Molecular Therapeutics and Formulation, School of Pharmacy, University of Nottingham, Nottingham NG7 2RD, U.K
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Generation of Genetic Tools for Gauging Multiple-Gene Expression at the Single-Cell Level. Appl Environ Microbiol 2021; 87:AEM.02956-20. [PMID: 33608300 DOI: 10.1128/aem.02956-20] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2020] [Accepted: 02/11/2021] [Indexed: 11/20/2022] Open
Abstract
Key microbial processes in many bacterial species are heterogeneously expressed in single cells of bacterial populations. However, the paucity of adequate molecular tools for live, real-time monitoring of multiple-gene expression at the single-cell level has limited the understanding of phenotypic heterogeneity. To investigate phenotypic heterogeneity in the ubiquitous opportunistic pathogen Pseudomonas aeruginosa, a genetic tool that allows gauging multiple-gene expression at the single-cell level has been generated. This tool, named pRGC, consists of a promoter-probe vector for transcriptional fusions that carries three reporter genes coding for the fluorescent proteins mCherry, green fluorescent protein (GFP), and cyan fluorescent protein (CFP). The pRGC vector has been characterized and validated via single-cell gene expression analysis of both constitutive and iron-regulated promoters, showing clear discrimination of the three fluorescence signals in single cells of a P. aeruginosa population without the need for image processing for spectral cross talk correction. In addition, two pRGC variants have been generated for either (i) integration of the reporter gene cassette into a single neutral site of P. aeruginosa chromosome that is suitable for long-term experiments in the absence of antibiotic selection or (ii) replication in bacterial genera other than Pseudomonas The easy-to-use genetic tools generated in this study will allow rapid and cost-effective investigation of multiple-gene expression in populations of environmental and pathogenic bacteria, hopefully advancing the understanding of microbial phenotypic heterogeneity.IMPORTANCE Within a bacterial population, single cells can differently express some genes, even though they are genetically identical and experience the same chemical and physical stimuli. This phenomenon, known as phenotypic heterogeneity, is mainly driven by gene expression noise and results in the emergence of bacterial subpopulations with distinct phenotypes. The analysis of gene expression at the single-cell level has shown that phenotypic heterogeneity is associated with key bacterial processes, including competence, sporulation, and persistence. In this study, new genetic tools have been generated that allow easy cloning of up to three promoters upstream of distinct fluorescent genes, making it possible to gauge multiple-gene expression at the single-cell level by fluorescence microscopy without the need for advanced image-processing procedures. A proof of concept has been provided by investigating iron uptake and iron storage gene expression in response to iron availability in P. aeruginosa.
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12
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Werner A, Otte KL, Stahlhut G, Pöggeler S. Establishment of the monomeric yellow-green fluorescent protein mNeonGreen for life cell imaging in mycelial fungi. AMB Express 2020; 10:222. [PMID: 33349910 PMCID: PMC7752937 DOI: 10.1186/s13568-020-01160-x] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/22/2020] [Accepted: 12/07/2020] [Indexed: 12/28/2022] Open
Abstract
The engineered monomeric version of the lancelet Branchiostoma lanceolatum fluorescent protein, mNeonGreen (mNG), has several positive characteristics, such as a very bright fluorescence, high photostability and fast maturation. These features make it a good candidate for the utilization as fluorescent tool for cell biology and biochemical applications in filamentous fungi. We report the generation of plasmids for the expression of the heterologous mNG gene under the control of an inducible and a constitutive promoter in the filamentous ascomycete Sordaria macrospora and display a stable expression of mNG in the cytoplasm. To demonstrate its usefulness for labeling of organelles, the peroxisomal targeting sequence serine-lysine-leucine (SKL) was fused to mNG. Expression of this tagged version led to protein import of mNG into peroxisomes and their bright fluorescence in life cell imaging.
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Affiliation(s)
- Antonia Werner
- Department of Genetics of Eukaryotic Microorganisms, Institute of Microbiology and Genetics, Georg-August-University of Göttingen, Grisebachstr. 8, 37077 Göttingen, Germany
| | - Kolja L. Otte
- Department of Genetics of Eukaryotic Microorganisms, Institute of Microbiology and Genetics, Georg-August-University of Göttingen, Grisebachstr. 8, 37077 Göttingen, Germany
| | - Gertrud Stahlhut
- Department of Genetics of Eukaryotic Microorganisms, Institute of Microbiology and Genetics, Georg-August-University of Göttingen, Grisebachstr. 8, 37077 Göttingen, Germany
| | - Stefanie Pöggeler
- Department of Genetics of Eukaryotic Microorganisms, Institute of Microbiology and Genetics, Georg-August-University of Göttingen, Grisebachstr. 8, 37077 Göttingen, Germany
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13
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Evaluation of chromosomal insertion loci in the Pseudomonas putida KT2440 genome for predictable biosystems design. Metab Eng Commun 2020; 11:e00139. [PMID: 32775199 PMCID: PMC7398981 DOI: 10.1016/j.mec.2020.e00139] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 07/02/2020] [Accepted: 07/15/2020] [Indexed: 01/27/2023] Open
Abstract
The development of Pseudomonas strains for industrial production of fuels and chemicals will require the integration of heterologous genes and pathways into the chromosome. Finding the most appropriate integration site to maximize strain performance is an essential part of the strain design process. We characterized seven chromosomal loci in Pseudomonas putida KT2440 for integration of a fluorescent protein expression construct. Insertion in five of the loci did not affect growth rate, but fluorescence varied by up to 27-fold. Three sites displaying a diversity of phenotypes with the fluorescent reporter were also chosen for the integration of a gene encoding a muconate importer. Depending on the integration locus, expression of the importer varied by approximately 3-fold and produced significant phenotypic differences. This work demonstrates the impact of the integration location on host viability, gene expression, and overall strain performance. Pseudomonas putida KT2440 chromosomal loci were characterized as potential insertion targets for heterologous genes. Integration location had a significant effect on heterologous protein expression and host phenotype. The identification of an appropriate chromosomal insertion location is essential to optimize genetic engineering design.
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14
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Noirot-Gros MF, Shinde SV, Akins C, Johnson JL, Zerbs S, Wilton R, Kemner KM, Noirot P, Babnigg G. Functional Imaging of Microbial Interactions With Tree Roots Using a Microfluidics Setup. FRONTIERS IN PLANT SCIENCE 2020; 11:408. [PMID: 32351525 PMCID: PMC7174594 DOI: 10.3389/fpls.2020.00408] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/17/2019] [Accepted: 03/20/2020] [Indexed: 05/20/2023]
Abstract
Coupling microfluidics with microscopy has emerged as a powerful approach to study at cellular resolution the dynamics in plant physiology and root-microbe interactions (RMIs). Most devices have been designed to study the model plant Arabidopsis thaliana at higher throughput than conventional methods. However, there is a need for microfluidic devices which enable in vivo studies of root development and RMIs in woody plants. Here, we developed the RMI-chip, a simple microfluidic setup in which Populus tremuloides (aspen tree) seedlings can grow for over a month, allowing continuous microscopic observation of interactions between live roots and rhizobacteria. We find that the colonization of growing aspen roots by Pseudomonas fluorescens in the RMI-chip involves dynamic biofilm formation and dispersal, in keeping with previous observations in a different experimental set-up. Also, we find that whole-cell biosensors based on the rhizobacterium Bacillus subtilis can be used to monitor compositional changes in the rhizosphere but that the application of these biosensors is limited by their efficiency at colonizing aspen roots and persisting. These results indicate that functional imaging of dynamic root-bacteria interactions in the RMI-chip requires careful matching between the host plant and the bacterial root colonizer.
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Affiliation(s)
| | | | | | | | | | | | | | | | - Gyorgy Babnigg
- Biosciences Division, Argonne National Laboratory, Lemont, IL, United States
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15
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Polarly Localized EccE 1 Is Required for ESX-1 Function and Stabilization of ESX-1 Membrane Proteins in Mycobacterium tuberculosis. J Bacteriol 2020; 202:JB.00662-19. [PMID: 31843799 DOI: 10.1128/jb.00662-19] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2019] [Accepted: 12/11/2019] [Indexed: 12/15/2022] Open
Abstract
Mycobacterium tuberculosis is a slow-growing intracellular bacterium with the ability to induce host cell death and persist indefinitely in the human body. This pathogen uses the specialized ESX-1 secretion system to secrete virulence factors and potent immunogenic effectors required for disease progression. ESX-1 is a multisubunit apparatus with a membrane complex that is predicted to form a channel in the cytoplasmic membrane. In M. tuberculosis this complex is composed of five membrane proteins: EccB1, EccCa1, EccCb1, EccD1, and EccE1 In this study, we have characterized the membrane component EccE1 and found that deletion of eccE 1 lowers the levels of EccB1, EccCa1, and EccD1, thereby abolishing ESX-1 secretion and attenuating M. tuberculosis ex vivo Surprisingly, secretion of EspB was not affected by loss of EccE1 Furthermore, EccE1 was found to be a membrane- and cell wall-associated protein that needs the presence of other ESX-1 components to assemble into a stable complex at the poles of M. tuberculosis Overall, this investigation provides new insights into the role of EccE1 and its localization in M. tuberculosis IMPORTANCE Tuberculosis (TB), the world's leading cause of death of humans from an infectious disease, is caused by the intracellular bacterium Mycobacterium tuberculosis The development of successful strategies to control TB requires better understanding of the complex interactions between the pathogen and the human host. We investigated the contribution of EccE1, a membrane protein, to the function of the ESX-1 secretion system, the major virulence determinant of M. tuberculosis By combining genetic analysis of selected mutants with eukaryotic cell biology and proteomics, we demonstrate that EccE1 is critical for ESX-1 function, secretion of effector proteins, and pathogenesis. Our research improves knowledge of the molecular basis of M. tuberculosis virulence and enhances our understanding of pathogenesis.
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16
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Noirot-Gros MF, Shinde S, Larsen PE, Zerbs S, Korajczyk PJ, Kemner KM, Noirot PH. Dynamics of Aspen Roots Colonization by Pseudomonads Reveals Strain-Specific and Mycorrhizal-Specific Patterns of Biofilm Formation. Front Microbiol 2018; 9:853. [PMID: 29774013 PMCID: PMC5943511 DOI: 10.3389/fmicb.2018.00853] [Citation(s) in RCA: 34] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2017] [Accepted: 04/13/2018] [Indexed: 12/20/2022] Open
Abstract
Rhizosphere-associated Pseudomonas fluorescens are known plant growth promoting (PGP) and mycorrhizal helper bacteria (MHB) of many plants and ectomycorrhizal fungi. We investigated the spatial and temporal dynamics of colonization of mycorrhizal and non-mycorrhizal Aspen seedlings roots by the P. fluorescens strains SBW25, WH6, Pf0-1, and the P. protegens strain Pf-5. Seedlings were grown in laboratory vertical plates systems, inoculated with a fluorescently labeled Pseudomonas strain, and root colonization was monitored over a period of 5 weeks. We observed unexpected diversity of bacterial assemblies on seedling roots that changed over time and were strongly affected by root mycorrhization. P. fluorescens SBW25 and WH6 stains developed highly structured biofilms with internal void spaces forming channels. On mycorrhizal roots bacteria appeared encased in a mucilaginous substance in which they aligned side by side in parallel arrangements. The different phenotypic classes of bacterial assemblies observed for the four Pseudomonas strains were summarized in a single model describing transitions between phenotypic classes. Our findings also reveal that bacterial assembly phenotypes are driven by interactions with mucilaginous materials present at roots.
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Affiliation(s)
| | - Shalaka Shinde
- Biosciences Division, Argonne National Laboratory, Lemont, IL, United States
| | - Peter E Larsen
- Biosciences Division, Argonne National Laboratory, Lemont, IL, United States
| | - Sarah Zerbs
- Biosciences Division, Argonne National Laboratory, Lemont, IL, United States
| | - Peter J Korajczyk
- Biosciences Division, Argonne National Laboratory, Lemont, IL, United States
| | - Kenneth M Kemner
- Biosciences Division, Argonne National Laboratory, Lemont, IL, United States
| | - Philippe H Noirot
- Biosciences Division, Argonne National Laboratory, Lemont, IL, United States
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