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Mannaa M, Lee D, Lee HH, Han G, Kang M, Kim TJ, Park J, Seo YS. Exploring the comparative genome of rice pathogen Burkholderia plantarii: unveiling virulence, fitness traits, and a potential type III secretion system effector. FRONTIERS IN PLANT SCIENCE 2024; 15:1416253. [PMID: 38845849 PMCID: PMC11153758 DOI: 10.3389/fpls.2024.1416253] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 04/12/2024] [Accepted: 05/10/2024] [Indexed: 06/09/2024]
Abstract
This study presents a comprehensive genomic analysis of Burkholderia plantarii, a rice pathogen that causes blight and grain rot in seedlings. The entire genome of B. plantarii KACC 18964 was sequenced, followed by a comparative genomic analysis with other available genomes to gain insights into its virulence, fitness, and interactions with rice. Multiple secondary metabolite gene clusters were identified. Among these, 12 demonstrated varying similarity levels to known clusters linked to bioactive compounds, whereas eight exhibited no similarity, indicating B. plantarii as a source of potentially novel secondary metabolites. Notably, the genes responsible for tropolone and quorum sensing were conserved across the examined genomes. Additionally, B. plantarii was observed to possess three complete CRISPR systems and a range of secretion systems, exhibiting minor variations among the analyzed genomes. Genomic islands were analyzed across the four genomes, and a detailed study of the B. plantarii KACC 18964 genome revealed 59 unique islands. These islands were thoroughly investigated for their gene contents and potential roles in virulence. Particular attention has been devoted to the Type III secretion system (T3SS), a crucial virulence factor. An in silico analysis of potential T3SS effectors identified a conserved gene, aroA. Further mutational studies, in planta and in vitro analyses validated the association between aroA and virulence in rice. Overall, this study enriches our understanding of the genomic basis of B. plantarii pathogenicity and emphasizes the potential role of aroA in virulence. This understanding may guide the development of effective disease management strategies.
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Affiliation(s)
- Mohamed Mannaa
- Department of Integrated Biological Science, Pusan National University, Busan, Republic of Korea
- Institute of System Biology, Pusan National University, Busan, Republic of Korea
- Department of Plant Pathology, Faculty of Agriculture, Cairo University, Giza, Egypt
| | - Duyoung Lee
- Department of Integrated Biological Science, Pusan National University, Busan, Republic of Korea
- Institute of System Biology, Pusan National University, Busan, Republic of Korea
| | - Hyun-Hee Lee
- Department of Integrated Biological Science, Pusan National University, Busan, Republic of Korea
| | - Gil Han
- Department of Integrated Biological Science, Pusan National University, Busan, Republic of Korea
| | - Minhee Kang
- Department of Integrated Biological Science, Pusan National University, Busan, Republic of Korea
- Institute of System Biology, Pusan National University, Busan, Republic of Korea
| | - Tae-Jin Kim
- Department of Integrated Biological Science, Pusan National University, Busan, Republic of Korea
- Institute of System Biology, Pusan National University, Busan, Republic of Korea
| | - Jungwook Park
- Biotechnology Research Division, National Institute of Fisheries Science, Busan, Republic of Korea
| | - Young-Su Seo
- Department of Integrated Biological Science, Pusan National University, Busan, Republic of Korea
- Institute of System Biology, Pusan National University, Busan, Republic of Korea
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Jia J, Lu SE. Comparative Genome Analyses Provide Insight into the Antimicrobial Activity of Endophytic Burkholderia. Microorganisms 2024; 12:100. [PMID: 38257926 PMCID: PMC10821513 DOI: 10.3390/microorganisms12010100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2023] [Revised: 01/02/2024] [Accepted: 01/03/2024] [Indexed: 01/24/2024] Open
Abstract
Endophytic bacteria are endosymbionts that colonize a portion of plants without harming the plant for at least a part of its life cycle. Bacterial endophytes play an essential role in promoting plant growth using multiple mechanisms. The genus Burkholderia is an important member among endophytes and encompasses bacterial species with high genetic versatility and adaptability. In this study, the endophytic characteristics of Burkholderia species are investigated via comparative genomic analyses of several endophytic Burkholderia strains with pathogenic Burkholderia strains. A group of bacterial genes was identified and predicted as the putative endophytic behavior genes of Burkholderia. Multiple antimicrobial biosynthesis genes were observed in these endophytic bacteria; however, certain important pathogenic and virulence genes were absent. The majority of resistome genes were distributed relatively evenly among the endophytic and pathogenic bacteria. All known types of secretion systems were found in the studied bacteria. This includes T3SS and T4SS, which were previously thought to be disproportionately represented in endophytes. Additionally, questionable CRISPR-Cas systems with an orphan CRISPR array were prevalent, suggesting that intact CRISPR-Cas systems may not exist in symbiotes of Burkholderia. This research not only sheds light on the antimicrobial activities that contribute to biocontrol but also expands our understanding of genomic variations in Burkholderia's endophytic and pathogenic bacteria.
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Affiliation(s)
| | - Shi-En Lu
- Department of Biochemistry, Molecular Biology, Entomology and Plant Pathology, Mississippi State University, Mississippi State, MS 39762, USA;
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3
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Gonzales M, Plener L, Armengaud J, Armstrong N, Chabrière É, Daudé D. Lactonase-mediated inhibition of quorum sensing largely alters phenotypes, proteome, and antimicrobial activities in Burkholderia thailandensis E264. Front Cell Infect Microbiol 2023; 13:1190859. [PMID: 37333853 PMCID: PMC10272358 DOI: 10.3389/fcimb.2023.1190859] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2023] [Accepted: 05/15/2023] [Indexed: 06/20/2023] Open
Abstract
Introduction Burkholderia thailandensis is a study model for Burkholderia pseudomallei, a highly virulent pathogen, known to be the causative agent of melioidosis and a potential bioterrorism agent. These two bacteria use an (acyl-homoserine lactone) AHL-mediated quorum sensing (QS) system to regulate different behaviors including biofilm formation, secondary metabolite productions, and motility. Methods Using an enzyme-based quorum quenching (QQ) strategy, with the lactonase SsoPox having the best activity on B. thailandensis AHLs, we evaluated the importance of QS in B. thailandensis by combining proteomic and phenotypic analyses. Results We demonstrated that QS disruption largely affects overall bacterial behavior including motility, proteolytic activity, and antimicrobial molecule production. We further showed that QQ treatment drastically decreases B. thailandensis bactericidal activity against two bacteria (Chromobacterium violaceum and Staphylococcus aureus), while a spectacular increase in antifungal activity was observed against fungi and yeast (Aspergillus niger, Fusarium graminearum and Saccharomyces cerevisiae). Discussion This study provides evidence that QS is of prime interest when it comes to understanding the virulence of Burkholderia species and developing alternative treatments.
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Affiliation(s)
- Mélanie Gonzales
- Aix Marseille Université, IRD, APHM, MEPHI, IHU-Méditerranée Infection, Marseille, France
- Gene&GreenTK, Marseille, France
| | | | - Jean Armengaud
- Université Paris-Saclay, CEA, INRAE, Département Médicaments et Technologies pour la Santé (DMTS), SPI, Bagnols-sur-Cèze, France
| | | | - Éric Chabrière
- Aix Marseille Université, IRD, APHM, MEPHI, IHU-Méditerranée Infection, Marseille, France
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Chodkowski JL, Shade A. A coevolution experiment between Flavobacterium johnsoniae and Burkholderia thailandensis reveals parallel mutations that reduce antibiotic susceptibility. MICROBIOLOGY (READING, ENGLAND) 2023; 169. [PMID: 36724091 DOI: 10.1099/mic.0.001267] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
One interference mechanism of bacterial competition is the production of antibiotics. Bacteria exposed to antibiotics can resist antibiotic inhibition through intrinsic or acquired mechanisms. Here, we performed a coevolution experiment to understand the long-term consequences of antibiotic production and antibiotic susceptibility for two environmental bacterial strains. We grew five independent lines of the antibiotic-producing environmental strain, Burkholderia thailandensis E264, and the antibiotic-inhibited environmental strain, Flavobacterium johnsoniae UW101, together and separately on agar plates for 7.5 months (1.5 month incubations), transferring each line five times to new agar plates. We observed that the F. johnsoniae ancestor could tolerate the B. thailandensis-produced antibiotic through efflux mechanisms, but that the coevolved lines had reduced susceptibility. We then sequenced genomes from the coevolved and monoculture F. johnsoniae lines, and uncovered mutational ramifications for the long-term antibiotic exposure. The coevolved genomes from F. johnsoniae revealed four potential mutational signatures of reduced antibiotic susceptibility that were not observed in the evolved monoculture lines. Two mutations were found in tolC: one corresponding to a 33 bp deletion and the other corresponding to a nonsynonymous mutation. A third mutation was observed as a 1 bp insertion coding for a RagB/SusD nutrient uptake protein. The last mutation was a G83R nonsynonymous mutation in acetyl-coA carboxylayse carboxyltransferase subunit alpha (AccA). Deleting the 33 bp from tolC in the F. johnsoniae ancestor reduced antibiotic susceptibility, but not to the degree observed in coevolved lines. Furthermore, the accA mutation matched a previously described mutation conferring resistance to B. thailandensis-produced thailandamide. Analysis of B. thailandensis transposon mutants for thailandamide production revealed that thailandamide was bioactive against F. johnsoniae, but also suggested that additional B. thailandensis-produced antibiotics were involved in the inhibition of F. johnsoniae. This study reveals how multi-generational interspecies interactions, mediated through chemical exchange, can result in novel interaction-specific mutations, some of which may contribute to reductions in antibiotic susceptibility.
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Affiliation(s)
- John L Chodkowski
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA
| | - Ashley Shade
- Department of Microbiology and Molecular Genetics, Michigan State University, East Lansing, MI 48824, USA.,Department of Plant, Soil and Microbial Sciences, Michigan State University, East Lansing, MI 48824, USA.,Program in Ecology, Evolution and Behavior, Michigan State University, East Lansing, MI 48824, USA.,Univ Lyon, CNRS, INSA Lyon, Université Claude Bernard Lyon 1, Ecole Centrale de Lyon, Ampère, UMR5005, 69134, Ecully cedex, France
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5
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Engdahl CS, Tikhe CV, Dimopoulos G. Discovery of novel natural products for mosquito control. Parasit Vectors 2022; 15:481. [PMID: 36539851 PMCID: PMC9768913 DOI: 10.1186/s13071-022-05594-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/18/2022] [Accepted: 11/17/2022] [Indexed: 12/24/2022] Open
Abstract
Vector control plays a key role in reducing the public health burden of mosquito-borne diseases. Today's vector control strategies largely rely on synthetic insecticides that can have a negative environmental impact when applied outdoors and often become inefficient because of the mosquitoes' ability to develop resistance. An alternative and promising approach to circumvent these challenges involves the implementation of insecticides derived from nature (biopesticides) for vector control. Biopesticides can constitute naturally occurring organisms or substances derived from them that have lifespan-shortening effects on disease vectors such as mosquitoes. Here we present the discovery and evaluation of natural product-based biological control agents that can potentially be developed into biopesticides for mosquito control. We screened a natural product collection comprising 390 compounds and initially identified 26 molecules with potential ability to kill the larval stages of the yellow fever mosquito Aedes aegypti, which is responsible for transmitting viruses such as dengue, Zika, chikungunya and yellow fever. Natural products identified as hits in the screen were further evaluated for their suitability for biopesticide development. We show that a selection of the natural product top hits, bactobolin, maytansine and ossamycin, also killed the larval stages of the malaria-transmitting mosquito Anopheles gambiae as well as the adult form of both species. We have further explored the usefulness of crude extracts and preparations from two of the best candidates' sources (organisms of origin) for mosquitocidal activity, that is extracts from the two bacteria Burkholderia thailandensis and Streptomyces hygroscopicus var. ossamyceticus.
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Affiliation(s)
- Cecilia S. Engdahl
- grid.21107.350000 0001 2171 9311W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD USA ,grid.12650.300000 0001 1034 3451Present Address: Department of Clinical Microbiology, Virology, Umeå University, 90185 Umeå, Sweden
| | - Chinmay V. Tikhe
- grid.21107.350000 0001 2171 9311W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD USA
| | - George Dimopoulos
- grid.21107.350000 0001 2171 9311W. Harry Feinstone Department of Molecular Microbiology and Immunology, Bloomberg School of Public Health, Johns Hopkins University, Baltimore, MD USA
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Aiosa N, Sinha A, Jaiyesimi OA, da Silva RR, Branda SS, Garg N. Metabolomics Analysis of Bacterial Pathogen Burkholderia thailandensis and Mammalian Host Cells in Co-culture. ACS Infect Dis 2022; 8:1646-1662. [PMID: 35767828 DOI: 10.1021/acsinfecdis.2c00233] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The Tier 1 HHS/USDA Select Agent Burkholderia pseudomallei is a bacterial pathogen that is highly virulent when introduced into the respiratory tract and intrinsically resistant to many antibiotics. Transcriptomic- and proteomic-based methodologies have been used to investigate mechanisms of virulence employed by B. pseudomallei and Burkholderia thailandensis, a convenient surrogate; however, analysis of the pathogen and host metabolomes during infection is lacking. Changes in the metabolites produced can be a result of altered gene expression and/or post-transcriptional processes. Thus, metabolomics complements transcriptomics and proteomics by providing a chemical readout of a biological phenotype, which serves as a snapshot of an organism's physiological state. However, the poor signal from bacterial metabolites in the context of infection poses a challenge in their detection and robust annotation. In this study, we coupled mammalian cell culture-based metabolomics with feature-based molecular networking of mono- and co-cultures to annotate the pathogen's secondary metabolome during infection of mammalian cells. These methods enabled us to identify several key secondary metabolites produced by B. thailandensis during infection of airway epithelial and macrophage cell lines. Additionally, the use of in silico approaches provided insights into shifts in host biochemical pathways relevant to defense against infection. Using chemical class enrichment analysis, for example, we identified changes in a number of host-derived compounds including immune lipids such as prostaglandins, which were detected exclusively upon pathogen challenge. Taken together, our findings indicate that co-culture of B. thailandensis with mammalian cells alters the metabolome of both pathogen and host and provides a new dimension of information for in-depth analysis of the host-pathogen interactions underlying Burkholderia infection.
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Affiliation(s)
- Nicole Aiosa
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 950 Atlantic Drive, Atlanta, Georgia 30332-2000, United States
| | - Anupama Sinha
- Biotechnology & Bioengineering, Sandia National Laboratories, 7011 East Avenue, Livermore, California 94550, United States
| | - Olakunle A Jaiyesimi
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 950 Atlantic Drive, Atlanta, Georgia 30332-2000, United States
| | - Ricardo R da Silva
- School of Pharmaceutical Sciences of Ribeirão Preto, University of São Paulo, Ribeirão Preto, Av. do Café─Vila Monte Alegre, 14040-903 Ribeirão Preto-SP, Brazil
| | - Steven S Branda
- Systems Biology, Sandia National Laboratories, 7011 East Avenue, Livermore, California 94550, United States
| | - Neha Garg
- School of Chemistry and Biochemistry, Georgia Institute of Technology, 950 Atlantic Drive, Atlanta, Georgia 30332-2000, United States.,Center for Microbial Dynamics and Infection, Georgia Institute of Technology, 311 Ferst Drive, ES&T, Atlanta, Georgia 30332, United States
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7
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Nelli MR, Heitmeier KN, Looper RE. Dissecting the Nucleoside Antibiotics as Universal Translation Inhibitors. Acc Chem Res 2021; 54:2798-2811. [PMID: 34152729 DOI: 10.1021/acs.accounts.1c00221] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
Without question, natural products have provided the lion share of leads, if not drugs themselves, for the treatment of bacterial infections. The bacterial arms race, fueled by selection and survival pressures has delivered a natural arsenal of small molecules targeting the most essential of life processes. Antibiotics that target these critical intracellular processes face the formidable defense of both penetrating a bacterial cell membrane and avoiding efflux to exert their effect. These challenges are especially effective in Gram-negative (Gram-(-)) bacteria, which have a double membrane structure and efficient efflux systems from the combination of outer-membrane porins and inner membrane proton pumps. In this landscape of offense and defense, our clinically used antibiotics have only successfully targeted three intracellular processes for therapeutic intervention in Gram-(-) bacteria: dihydrofolate biosynthesis, transcription, and translation. Not surprisingly, such critical survival machinery is a popular target for bacterial warfare, and eight of our 14 classes of commonly used antibiotics target translation with the bacterial ribosome remaining one the most vetted targets for antimicrobial therapy. On the plus side, its anionic character attracts cationic inhibitors, which are generally more capable of penetrating the bacterial cell wall, and clinical resistance rates are usually manageable as mutation of such a highly evolved machine is difficult. On the down side, this highly evolved machine renders it difficult to inhibit selectively, and the inhibition of prokaryotic translation versus both eukaryotic cellular and mitochondrial translation is critical for clinical development and minimization of undesired toxicities.A class of natural products known as the "nucleoside antibiotics" have historically been recognized as universal inhibitors of the ribosome and can inhibit translation in prokaryotes, eukaryotes, and archaea. While they have served an essential role in dissecting the biochemical underpinnings of the enzymatic functions of the ribosome, they have not proven therapeutically useful as they target the highly conserved rRNA in the P-site and are toxic to mammalian cells. In this Account, we describe our studies on the natural product amicetin, a nucleoside antibiotic that we have demonstrated to break the rule of being a universal translation inhibitor. While the cytosine of amicetin mimics C75 of the 3'-CCA tail of the P-site tRNA akin to other nucleoside antibiotics, we advance a hypothesis that amicetin's unique interaction with the ribosomal protein uL16 exploits an untapped mechanism for selectively targeting the bacterial ribosome. A complex molecule comprised of a nucleoside, carbohydrates and amino acids, amicetin is also chemically unstable. Our initial attempts to stabilize and simplify this scaffold are presented with the ultimate goal of rebuilding the compound with improved penetrance to bacterial cells. If successful, this scaffold would demonstrate a path forward for a new class of antibiotics capable of selectively targeting the ribosomal P-site.
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Affiliation(s)
- Matthew R. Nelli
- Department of Chemistry, University of Utah, Salt Lake City Utah 84103, United States
| | - Kendall N. Heitmeier
- Department of Chemistry, University of Utah, Salt Lake City Utah 84103, United States
| | - Ryan E. Looper
- Department of Chemistry, University of Utah, Salt Lake City Utah 84103, United States
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8
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Foxfire A, Buhrow AR, Orugunty RS, Smith L. Drug discovery through the isolation of natural products from Burkholderia. Expert Opin Drug Discov 2021; 16:807-822. [PMID: 33467922 PMCID: PMC9844120 DOI: 10.1080/17460441.2021.1877655] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Introduction: The increasing threat of antibiotic-resistant pathogens makes it imperative that new antibiotics to combat them are discovered. Burkholderia is a genus of Gram-negative, non-sporulating bacteria. While ubiquitous and capable of growing within plants and groundwater, they are primarily soil-dwelling organisms. These include the more virulent forms of Burkholderia such as Burkholderia mallei, Burkholderia pseudomallei, and the Burkholderia cepacia complex (Bcc).Areas covered: This review provides a synopsis of current research on the natural products isolated from the genus Burkholderia. The authors also cover the research on the drug discovery efforts that have been performed on the natural products derived from Burkholderia.Expert opinion: Though Burkholderia has a small number of pathogenic species, the majority of the genus is avirulent and almost all members of the genus are capable of producing useful antimicrobial products that could potentially lead to the development of novel therapeutics against infectious diseases. The need for discovery of new antibiotics is urgent due to the ever-increasing prevalence of antibiotic-resistant pathogens, coupled with the decline in the discovery of new antibiotics.
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Affiliation(s)
- Adam Foxfire
- Department of Biology, Texas A&M University, College Station, TX 77843
| | - Andrew Riley Buhrow
- Department of Biology, Texas A&M University, College Station, TX 77843,Antimicrobial Division, Sano Chemicals Inc., Bryan, TX 77803
| | | | - Leif Smith
- Department of Biology, Texas A&M University, College Station, TX 77843,Antimicrobial Division, Sano Chemicals Inc., Bryan, TX 77803,Address correspondence to Leif Smith,
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Li A, Okada BK, Rosen PC, Seyedsayamdost MR. Piperacillin triggers virulence factor biosynthesis via the oxidative stress response in Burkholderia thailandensis. Proc Natl Acad Sci U S A 2021; 118:e2021483118. [PMID: 34172579 PMCID: PMC8256049 DOI: 10.1073/pnas.2021483118] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
Natural products have been an important source of therapeutic agents and chemical tools. The recent realization that many natural product biosynthetic genes are silent or sparingly expressed during standard laboratory growth has prompted efforts to investigate their regulation and develop methods to induce their expression. Because it is difficult to intuit signals that induce a given biosynthetic locus, we recently implemented a forward chemical-genetic approach to identify such inducers. In the current work, we applied this approach to nine silent biosynthetic loci in the model bacterium Burkholderia thailandensis to systematically screen for elicitors from a library of Food and Drug Administration-approved drugs. We find that β-lactams, fluoroquinolones, antifungals, and, surprisingly, calcimimetics, phenothiazine antipsychotics, and polyaromatic antidepressants are the most effective global inducers of biosynthetic genes. Investigations into the mechanism of stimulation of the silent virulence factor malleicyprol by the β-lactam piperacillin allowed us to elucidate the underlying regulatory circuits. Low-dose piperacillin causes oxidative stress, thereby inducing redox-sensing transcriptional regulators, which activate malR, a pathway-specific positive regulator of the malleicyprol gene cluster. Malleicyprol is thus part of the OxyR and SoxR regulons in B. thailandensis, allowing the bacterium to initiate virulence in response to oxidative stress. Our work catalogs a diverse array of elicitors and a previously unknown regulatory input for secondary metabolism in B. thailandensis.
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Affiliation(s)
- Anran Li
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544
| | - Bethany K Okada
- Department of Chemistry, Princeton University, Princeton, NJ 08544
| | - Paul C Rosen
- Department of Chemistry, Princeton University, Princeton, NJ 08544
| | - Mohammad R Seyedsayamdost
- Department of Molecular Biology, Princeton University, Princeton, NJ 08544;
- Department of Chemistry, Princeton University, Princeton, NJ 08544
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10
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Lee HH, Park J, Jung H, Seo YS. Pan-Genome Analysis Reveals Host-Specific Functional Divergences in Burkholderia gladioli. Microorganisms 2021; 9:1123. [PMID: 34067383 PMCID: PMC8224644 DOI: 10.3390/microorganisms9061123] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Revised: 05/17/2021] [Accepted: 05/20/2021] [Indexed: 11/16/2022] Open
Abstract
Burkholderia gladioli has high versatility and adaptability to various ecological niches. Here, we constructed a pan-genome using 14 genome sequences of B. gladioli, which originate from different niches, including gladiolus, rice, humans, and nature. Functional roles of core and niche-associated genomes were investigated by pathway enrichment analyses. Consequently, we inferred the uniquely important role of niche-associated genomes in (1) selenium availability during competition with gladiolus host; (2) aromatic compound degradation in seed-borne and crude oil-accumulated environments, and (3) stress-induced DNA repair system/recombination in the cystic fibrosis-niche. We also identified the conservation of the rhizomide biosynthetic gene cluster in all the B. gladioli strains and the concentrated distribution of this cluster in human isolates. It was confirmed the absence of complete CRISPR/Cas system in both plant and human pathogenic B. gladioli and the presence of the system in B. gladioli living in nature, possibly reflecting the inverse relationship between CRISPR/Cas system and virulence.
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Affiliation(s)
- Hyun-Hee Lee
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea; (H.-H.L.); (J.P.); (H.J.)
| | - Jungwook Park
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea; (H.-H.L.); (J.P.); (H.J.)
- Environmental Microbiology Research Team, Nakdonggang National Institute of Biological Resources (NNIBR), Sangju 37242, Korea
| | - Hyejung Jung
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea; (H.-H.L.); (J.P.); (H.J.)
| | - Young-Su Seo
- Department of Integrated Biological Science, Pusan National University, Busan 46241, Korea; (H.-H.L.); (J.P.); (H.J.)
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11
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Secondary metabolites from the Burkholderia pseudomallei complex: structure, ecology, and evolution. J Ind Microbiol Biotechnol 2020; 47:877-887. [PMID: 33052546 DOI: 10.1007/s10295-020-02317-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2020] [Accepted: 09/22/2020] [Indexed: 12/15/2022]
Abstract
Bacterial secondary metabolites play important roles in promoting survival, though few have been carefully studied in their natural context. Numerous gene clusters code for secondary metabolites in the genomes of members of the Bptm group, made up of three closely related species with distinctly different lifestyles: the opportunistic pathogen Burkholderia pseudomallei, the non-pathogenic saprophyte Burkholderia thailandensis, and the host-adapted pathogen Burkholderia mallei. Several biosynthetic gene clusters are conserved across two or all three species, and this provides an opportunity to understand how the corresponding secondary metabolites contribute to survival in different contexts in nature. In this review, we discuss three secondary metabolites from the Bptm group: bactobolin, malleilactone (and malleicyprol), and the 4-hydroxy-3-methyl-2-alkylquinolines, providing an overview of each of their biosynthetic pathways and insight into their potential ecological roles. Results of studies on these secondary metabolites provide a window into how secondary metabolites contribute to bacterial survival in different environments, from host infections to polymicrobial soil communities.
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12
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Mao D, Yoshimura A, Wang R, Seyedsayamdost MR. Reporter-Guided Transposon Mutant Selection for Activation of Silent Gene Clusters in Burkholderia thailandensis. Chembiochem 2020; 21:1826-1831. [PMID: 31984619 DOI: 10.1002/cbic.201900748] [Citation(s) in RCA: 9] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2019] [Indexed: 01/01/2023]
Abstract
Most natural product biosynthetic gene clusters that can be observed bioinformatically are silent. This insight has prompted the development of several methodologies for inducing their expression. One of the more recent methods, termed reporter-guided mutant selection (RGMS), entails creation of a library of mutants that is then screened for the desired phenotype via reporter gene expression. Herein, we apply a similar approach to Burkholderia thailandensis and, using transposon mutagenesis, mutagenize three strains, each carrying a fluorescent reporter in the malleilactone (mal), capistruin (cap), or an unidentified ribosomal peptide (tomm) gene cluster. We show that even a small library of <500 mutants can be used to induce expression of each cluster. We also explore the mechanism of activation and find that inhibition of pyrimidine biosynthesis is linked to the induction of the mal cluster. Both a transposon insertion into pyrF as well as small-molecule-mediated inhibition of PyrF trigger malleilactone biosynthesis. Our results pave the way toward the broad application of RGMS and related approaches to Burkholderia spp.
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Affiliation(s)
- Dainan Mao
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Aya Yoshimura
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Rurun Wang
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA
| | - Mohammad R Seyedsayamdost
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA.,Department of Molecular Biology, Princeton University, Princeton, NJ, 08544, USA
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13
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Park JD, Moon K, Miller C, Rose J, Xu F, Ebmeier CC, Jacobsen JR, Mao D, Old WM, DeShazer D, Seyedsayamdost MR. Thailandenes, Cryptic Polyene Natural Products Isolated from Burkholderia thailandensis Using Phenotype-Guided Transposon Mutagenesis. ACS Chem Biol 2020; 15:1195-1203. [PMID: 31816232 DOI: 10.1021/acschembio.9b00883] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023]
Abstract
Burkholderia thailandensis has emerged as a model organism for investigating the production and regulation of diverse secondary metabolites. Most of the biosynthetic gene clusters encoded in B. thailandensis are silent, motivating the development of new methods for accessing their products. In the current work, we add to the canon of available approaches using phenotype-guided transposon mutagenesis to characterize a silent biosynthetic gene cluster. Because secondary metabolite biosynthesis is often associated with phenotypic changes, we carried out random transposon mutagenesis followed by phenotypic inspection of the resulting colonies. Several mutants exhibited intense pigmentation and enhanced expression of an iterative type I polyketide synthase cluster that we term org. Disruptions of orgA, orgB, and orgC abolished the biosynthesis of the diffusible pigment, thus linking it to the org operon. Isolation and structural elucidation by HR-MS and 1D/2D NMR spectroscopy revealed three novel, cryptic metabolites, thailandene A-C. Thailandenes are linear formylated or acidic polyenes containing a combination of cis and trans double bonds. Variants A and B exhibited potent antibiotic activity against Staphylococcus aureus and Saccharomyces cerevisiae but not against Escherichia coli. One of the transposon mutants that exhibited an enhanced expression of org contained an insertion upstream of a σ54-dependent transcription factor. Closer inspection of the org operon uncovered a σ54 promoter consensus sequence upstream of orgA, providing clues regarding its regulation. Our results showcase the utility of phenotype-guided transposon mutagenesis in uncovering cryptic metabolites encoded in bacterial genomes.
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Affiliation(s)
- Jong-Duk Park
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Kyuho Moon
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Cheryl Miller
- Molecular and Translational Science Division, U.S. Army Medical Research Institute of Infectious Diseases, Frederick, Maryland 21702, United States
| | - Jessica Rose
- Biotechnology Program, Hagerstown Community College, Hagerstown, Maryland 21742, United States
| | - Fei Xu
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Christopher C. Ebmeier
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309, United States
| | - Jeremy R. Jacobsen
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309, United States
| | - Dainan Mao
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - William M. Old
- Department of Molecular, Cellular, and Developmental Biology, University of Colorado, Boulder, Colorado 80309, United States
| | - David DeShazer
- Bacteriology Division, U.S. Army Medical Research Institute of Infectious Diseases, Frederick, Maryland 21702, United States
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14
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Vojáčková P, Michalska L, Nečas M, Shcherbakov D, Böttger EC, Šponer J, Šponer JE, Švenda J. Stereocontrolled Synthesis of (−)-Bactobolin A. J Am Chem Soc 2020; 142:7306-7311. [DOI: 10.1021/jacs.0c01554] [Citation(s) in RCA: 12] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Affiliation(s)
- Petra Vojáčková
- Department of Chemistry, Masaryk University, Brno 625 00, Czech Republic
- International Clinical Research Center, St. Anne’s University Hospital, Brno 656 91, Czech Republic
| | - Lucyna Michalska
- Department of Chemistry, Masaryk University, Brno 625 00, Czech Republic
- International Clinical Research Center, St. Anne’s University Hospital, Brno 656 91, Czech Republic
| | - Marek Nečas
- Department of Chemistry, Masaryk University, Brno 625 00, Czech Republic
| | - Dimitri Shcherbakov
- Institute of Medical Microbiology, University of Zürich, Zürich 8006, Switzerland
| | - Erik C. Böttger
- Institute of Medical Microbiology, University of Zürich, Zürich 8006, Switzerland
| | - Jiří Šponer
- Institute of Biophysics, Czech Academy of Sciences, Brno 612 65, Czech Republic
| | - Judit E. Šponer
- Institute of Biophysics, Czech Academy of Sciences, Brno 612 65, Czech Republic
| | - Jakub Švenda
- Department of Chemistry, Masaryk University, Brno 625 00, Czech Republic
- International Clinical Research Center, St. Anne’s University Hospital, Brno 656 91, Czech Republic
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15
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Greenberg EP, Chandler JR, Seyedsayamdost MR. The Chemistry and Biology of Bactobolin: A 10-Year Collaboration with Natural Product Chemist Extraordinaire Jon Clardy. JOURNAL OF NATURAL PRODUCTS 2020; 83:738-743. [PMID: 32105069 PMCID: PMC8118907 DOI: 10.1021/acs.jnatprod.9b01237] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/10/2023]
Abstract
Bactobolin is a hybrid natural product with potent cytotoxic activity. Its production from Burkholderia thailandensis was reported as part of a collaboration between the Greenberg and Clardy laboratories in 2010. The collaboration sparked a series of studies leading to the discovery of new analogues and associated structure-activity relationships, the identification of the bactobolin biosynthetic gene cluster and assembly of its unusual amino acid building block, the molecular target of and resistance to the antibiotic, and finally an X-ray crystal structure of the ribosome-bactobolin complex. Herein, we review the collaborations that led to our current understanding of the chemistry and biology of bactobolin.
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Affiliation(s)
- E Peter Greenberg
- Department of Microbiology, School of Medicine, University of Washington, Seattle, Washington 98195, United States
| | - Josephine R Chandler
- Department of Molecular Biosciences, University of Kansas, Lawrence, Kansas 66045, United States
| | - Mohammad R Seyedsayamdost
- Departments of Chemistry and Molecular Biology, Princeton University, Princeton, New Jersey 08544, United States
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16
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Multi-Omic Analyses Provide Links between Low-Dose Antibiotic Treatment and Induction of Secondary Metabolism in Burkholderia thailandensis. mBio 2020; 11:mBio.03210-19. [PMID: 32098820 PMCID: PMC7042699 DOI: 10.1128/mbio.03210-19] [Citation(s) in RCA: 19] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Low doses of antibiotics can trigger secondary metabolite biosynthesis in bacteria, but the underlying mechanisms are generally unknown. We sought to better understand this phenomenon by studying how the antibiotic trimethoprim activates the synthesis of the virulence factor malleilactone in Burkholderia thailandensis Using transcriptomics, quantitative multiplexed proteomics, and primary metabolomics, we systematically mapped the changes induced by trimethoprim. Surprisingly, even subinhibitory doses of the antibiotic resulted in broad transcriptional and translational alterations, with ∼8.5% of the transcriptome and ∼5% of the proteome up- or downregulated >4-fold. Follow-up studies with genetic-biochemical experiments showed that the induction of malleilactone synthesis can be sufficiently explained by the accumulation of methionine biosynthetic precursors, notably homoserine, as a result of inhibition of the folate pathway. Homoserine activated the malleilactone gene cluster via the transcriptional regulator MalR and gave rise to a secondary metabolome which was very similar to that generated by trimethoprim. Our work highlights the expansive changes that low-dose trimethoprim induces on bacterial physiology and provides insights into its stimulatory effect on secondary metabolism.IMPORTANCE The discovery of antibiotics ranks among the most significant accomplishments of the last century. Although the targets of nearly all clinical antibiotics are known, our understanding regarding their natural functions and the effects of subinhibitory concentrations is in its infancy. Stimulatory rather than inhibitory functions have been attributed to low-dose antibiotics. Among these, we previously found that antibiotics activate silent biosynthetic genes and thereby enhance the metabolic output of bacteria. The regulatory circuits underlying this phenomenon are unknown. We take a first step toward elucidating these circuits and show that low doses of trimethoprim (Tmp) have cell-wide effects on the saprophyte Burkholderia thailandensis Most importantly, inhibition of one-carbon metabolic processes by Tmp leads to an accumulation of homoserine, which induces the production of an otherwise silent cytotoxin via a LuxR-type transcriptional regulator. These results provide a starting point for uncovering the molecular basis of the hormetic effects of antibiotics.
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17
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Thapa SS, Grove A. Do Global Regulators Hold the Key to Production of Bacterial Secondary Metabolites? Antibiotics (Basel) 2019; 8:antibiotics8040160. [PMID: 31547528 PMCID: PMC6963729 DOI: 10.3390/antibiotics8040160] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2019] [Revised: 09/18/2019] [Accepted: 09/19/2019] [Indexed: 12/18/2022] Open
Abstract
The emergence of multiple antibiotic resistant bacteria has pushed the available pool of antibiotics to the brink. Bacterial secondary metabolites have long been a valuable resource in the development of antibiotics, and the genus Burkholderia has recently emerged as a source of novel compounds with antibacterial, antifungal, and anti-cancer activities. Genome mining has contributed to the identification of biosynthetic gene clusters, which encode enzymes that are responsible for synthesis of such secondary metabolites. Unfortunately, these large gene clusters generally remain silent or cryptic under normal laboratory settings, which creates a hurdle in identification and isolation of these compounds. Various strategies, such as changes in growth conditions and antibiotic stress, have been applied to elicit the expression of these cryptic gene clusters. Although a number of compounds have been isolated from different Burkholderia species, the mechanisms by which the corresponding gene clusters are regulated remain poorly understood. This review summarizes the activity of well characterized secondary metabolites from Burkholderia species and the role of local regulators in their synthesis, and it highlights recent evidence for the role of global regulators in controlling production of secondary metabolites. We suggest that targeting global regulators holds great promise for the awakening of cryptic gene clusters and for developing better strategies for discovery of novel antibiotics.
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Affiliation(s)
- Sudarshan Singh Thapa
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
| | - Anne Grove
- Department of Biological Sciences, Louisiana State University, Baton Rouge, LA 70803, USA.
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18
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Seyedsayamdost MR. Toward a global picture of bacterial secondary metabolism. J Ind Microbiol Biotechnol 2019; 46:301-311. [PMID: 30684124 DOI: 10.1007/s10295-019-02136-y] [Citation(s) in RCA: 35] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2018] [Accepted: 01/02/2019] [Indexed: 12/20/2022]
Abstract
Bacterial metabolism is comprised of primary metabolites, the intracellular molecules of life that enable growth and proliferation, and secondary metabolites, predominantly extracellular molecules that facilitate a microbe's interaction with its environment. While our knowledge of primary metabolism and its web of interconnected intermediates is quantitative and holistic, significant knowledge gaps remain in our understanding of the secondary metabolomes of bacteria. In this Perspective, I discuss the main challenges involved in obtaining a global, comprehensive picture of bacterial secondary metabolomes, specifically in biosynthetically "gifted" microbes. Recent methodological advances that can meet these challenges will be reviewed. Applications of these methods combined with ongoing innovations will enable a detailed picture of global secondary metabolomes, which will in turn shed light onto the biology, chemistry, and enzymology underlying natural products and simultaneously aid drug discovery.
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Affiliation(s)
- Mohammad R Seyedsayamdost
- Department of Chemistry, Princeton University, Princeton, NJ, 08544, USA.
- Department of Molecular Biology, Princeton University, Princeton, NJ, USA.
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19
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Esmaeel Q, Pupin M, Jacques P, Leclère V. Nonribosomal peptides and polyketides of Burkholderia: new compounds potentially implicated in biocontrol and pharmaceuticals. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2018; 25:29794-29807. [PMID: 28547376 DOI: 10.1007/s11356-017-9166-3] [Citation(s) in RCA: 41] [Impact Index Per Article: 6.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/07/2017] [Accepted: 05/01/2017] [Indexed: 06/07/2023]
Abstract
Bacteria belonging to the genus Burkholderia live in various ecological niches and present a significant role in the environments through the excretion of a wide variety of secondary metabolites including modular nonribosomal peptides (NRPs) and polyketides (PKs). These metabolites represent a widely distributed biomedically and biocontrol important class of natural products including antibiotics, siderophores, and anticancers as well as biopesticides that are considered as a novel source that can be used to defend ecological niche from competitors and to promote plant growth. The aim of this review is to present all NRPs produced or potentially produced by strains of Burkholderia, as NRPs represent a major source of active compounds implicated in biocontrol. The review is a compilation of results from a large screening we have performed on 48 complete sequenced genomes available in NCBI to identify NRPS gene clusters, and data found in the literature mainly because some interesting compounds are produced by strains not yet sequenced. In addition to NRPs, hybrids NRPs/PKs are also included. Specific features about biosynthetic gene clusters and structures of the modular enzymes responsible for the synthesis, the biological activities, and the potential uses in agriculture and pharmaceutical of NRPs and hybrids NRPs/PKs will also be discussed.
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Affiliation(s)
- Qassim Esmaeel
- University Lille, INRA, ISA, University Artois, University Littoral Côte d'Opale, EA 7394-ICV- Institut Charles Viollette, F-59000, Lille, France
- Laboratoire de Stress, Défenses et Reproduction des Plantes URVVC-EA 4707, UFR Sciences Exactes et Naturelles, University of Reims-Champagne-Ardenne, Reims, France
| | - Maude Pupin
- University Lille, CNRS, Centrale Lille, UMR 9189- CRIStAL- Centre de Recherche en Informatique Signal et Automatique de Lille, F-59000, Lille, France
- Inria-Lille Nord Europe, Bonsai team, F-59655, Villeneuve d'Ascq Cedex, France
| | - Philippe Jacques
- University Lille, INRA, ISA, University Artois, University Littoral Côte d'Opale, EA 7394-ICV- Institut Charles Viollette, F-59000, Lille, France
- TERRA Research Centre, Microbial Processes and Interactions (MiPI), Gembloux Agro-Bio Tech University of Liege, B-5030, Gembloux, Belgium
| | - Valérie Leclère
- University Lille, INRA, ISA, University Artois, University Littoral Côte d'Opale, EA 7394-ICV- Institut Charles Viollette, F-59000, Lille, France.
- University Lille, CNRS, Centrale Lille, UMR 9189- CRIStAL- Centre de Recherche en Informatique Signal et Automatique de Lille, F-59000, Lille, France.
- Inria-Lille Nord Europe, Bonsai team, F-59655, Villeneuve d'Ascq Cedex, France.
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20
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Wu Y, Seyedsayamdost MR. The Polyene Natural Product Thailandamide A Inhibits Fatty Acid Biosynthesis in Gram-Positive and Gram-Negative Bacteria. Biochemistry 2018; 57:4247-4251. [DOI: 10.1021/acs.biochem.8b00678] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Yihan Wu
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
| | - Mohammad R. Seyedsayamdost
- Department of Chemistry, Princeton University, Princeton, New Jersey 08544, United States
- Department of Molecular Biology, Princeton University, Princeton, New Jersey 08544, United States
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21
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Two rsaM Homologues Encode Central Regulatory Elements Modulating Quorum Sensing in Burkholderia thailandensis. J Bacteriol 2018; 200:JB.00727-17. [PMID: 29507087 DOI: 10.1128/jb.00727-17] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/04/2017] [Accepted: 02/20/2018] [Indexed: 01/05/2023] Open
Abstract
The bacterium Burkholderia thailandensis possesses three N-acyl-l-homoserine lactone (AHL) quorum sensing (QS) systems designated BtaI1/BtaR1 (QS-1), BtaI2/BtaR2 (QS-2), and BtaI3/BtaR3 (QS-3). These QS systems are associated with the biosynthesis of N-octanoyl-homoserine lactone (C8-HSL), N-3-hydroxy-decanoyl-homoserine lactone (3OHC10-HSL), and N-3-hydroxy-octanoyl-homoserine lactone (3OHC8-HSL), which are produced by the LuxI-type synthases BtaI1, BtaI2, and BtaI3 and modulated by the LuxR-type transcriptional regulators BtaR1, BtaR2, and BtaR3. The btaR1-btaI1 and btaR2-btaI2 gene clusters each carry an additional gene encoding a homologue of the QS repressor RsaM originally identified in the phytopathogen Pseudomonas fuscovaginae and thus here named rsaM1 and rsaM2, respectively. We have characterized the functions of these two conserved rsaM homologues and demonstrated their involvement in the regulation of AHL biosynthesis in B. thailandensis strain E264. We quantified the production of C8-HSL, 3OHC10-HSL, and 3OHC8-HSL by liquid chromatography coupled to tandem mass spectrometry (LC-MS/MS) in the wild-type strain and in the rsaM1 and rsaM2 mutants, and we monitored btaI1, btaI2, and btaI3 expression using chromosomal mini-CTX-lux transcriptional reporters. The transcription of btaR1, btaR2, and btaR3 was also measured by quantitative reverse transcription-PCR (qRT-PCR). We observed that RsaM1 mainly represses the QS-1 system, whereas RsaM2 principally represses the QS-2 system. We also found that both rsaM1 and rsaM2 are QS controlled and negatively autoregulated. We conclude that RsaM1 and RsaM2 are an integral part of the QS circuitry of B. thailandensis and play a major role in the hierarchical and homeostatic organization of the QS-1, QS-2, and QS-3 systems.IMPORTANCE Quorum sensing (QS) is commonly involved in the coordination of gene transcription associated with the establishment of host-pathogen interactions and acclimatization to the environment. We present the functional characterization of two rsaM homologues in the regulation of the multiple QS systems coexisting in the nonpathogenic bacterium Burkholderia thailandensis, which is widely used as a model system for the study of the human pathogen Burkholderia pseudomallei We found that inactivation of these rsaM homologues, which are clustered with the other QS genes, profoundly affects the QS circuitry of B. thailandensis We conclude that they constitute essential regulatory components of the QS modulatory network and provide additional layers of regulation to modulate the transcription of QS-controlled genes, particularly those linked to environmental adaptation.
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22
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Duong LT, Schwarz S, Gross H, Breitbach K, Hochgräfe F, Mostertz J, Eske-Pogodda K, Wagner GE, Steinmetz I, Kohler C. GvmR - A Novel LysR-Type Transcriptional Regulator Involved in Virulence and Primary and Secondary Metabolism of Burkholderia pseudomallei. Front Microbiol 2018; 9:935. [PMID: 29867844 PMCID: PMC5964159 DOI: 10.3389/fmicb.2018.00935] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/05/2018] [Accepted: 04/23/2018] [Indexed: 01/22/2023] Open
Abstract
Burkholderia pseudomallei is a soil-dwelling bacterium able to survive not only under adverse environmental conditions, but also within various hosts which can lead to the disease melioidosis. The capability of B. pseudomallei to adapt to environmental changes is facilitated by the large number of regulatory proteins encoded by its genome. Among them are more than 60 uncharacterized LysR-type transcriptional regulators (LTTRs). Here we analyzed a B. pseudomallei mutant harboring a transposon in the gene BPSL0117 annotated as a LTTR, which we named gvmR (globally acting virulence and metabolism regulator). The gvmR mutant displayed a growth defect in minimal medium and macrophages in comparison with the wild type. Moreover, disruption of gvmR rendered B. pseudomallei avirulent in mice indicating a critical role of GvmR in infection. These defects of the mutant were rescued by ectopic expression of gvmR. To identify genes whose expression is modulated by GvmR, global transcriptome analysis of the B. pseudomallei wild type and gvmR mutant was performed using whole genome tiling microarrays. Transcript levels of 190 genes were upregulated and 141 genes were downregulated in the gvmR mutant relative to the wild type. Among the most downregulated genes in the gvmR mutant were important virulence factor genes (T3SS3, T6SS1, and T6SS2), which could explain the virulence defect of the gvmR mutant. In addition, expression of genes related to amino acid synthesis, glyoxylate shunt, iron-sulfur cluster assembly, and syrbactin metabolism (secondary metabolite) was decreased in the mutant. On the other hand, inactivation of GvmR increased expression of genes involved in pyruvate metabolism, ATP synthesis, malleobactin, and porin genes. Quantitative real-time PCR verified the differential expression of 27 selected genes. In summary, our data show that GvmR acts as an activating and repressing global regulator that is required to coordinate expression of a diverse set of metabolic and virulence genes essential for the survival in the animal host and under nutrient limitation.
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Affiliation(s)
- Linh Tuan Duong
- Friedrich Loeffler Institute of Medical Microbiology, University Medicine Greifswald, Greifswald, Germany
| | - Sandra Schwarz
- Interfaculty Institute of Microbiology and Infection Medicine Tübingen, University of Tübingen, Tübingen, Germany
| | - Harald Gross
- Department of Pharmaceutical Biology, Pharmaceutical Institute, Eberhard Karls University of Tübingen, Tübingen, Germany.,German Centre for Infection Research, Partner Site Tübingen, Tübingen, Germany
| | - Katrin Breitbach
- Friedrich Loeffler Institute of Medical Microbiology, University Medicine Greifswald, Greifswald, Germany
| | - Falko Hochgräfe
- Competence Center Functional Genomics, Junior Research Group Pathoproteomics, University of Greifswald, Greifswald, Germany
| | - Jörg Mostertz
- Competence Center Functional Genomics, Junior Research Group Pathoproteomics, University of Greifswald, Greifswald, Germany
| | - Kristin Eske-Pogodda
- Friedrich Loeffler Institute of Medical Microbiology, University Medicine Greifswald, Greifswald, Germany
| | - Gabriel E Wagner
- Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Graz, Austria
| | - Ivo Steinmetz
- Friedrich Loeffler Institute of Medical Microbiology, University Medicine Greifswald, Greifswald, Germany.,Institute of Hygiene, Microbiology and Environmental Medicine, Medical University of Graz, Graz, Austria
| | - Christian Kohler
- Friedrich Loeffler Institute of Medical Microbiology, University Medicine Greifswald, Greifswald, Germany
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23
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Lin J, Zhou D, Steitz TA, Polikanov YS, Gagnon MG. Ribosome-Targeting Antibiotics: Modes of Action, Mechanisms of Resistance, and Implications for Drug Design. Annu Rev Biochem 2018; 87:451-478. [PMID: 29570352 DOI: 10.1146/annurev-biochem-062917-011942] [Citation(s) in RCA: 161] [Impact Index Per Article: 26.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Genetic information is translated into proteins by the ribosome. Structural studies of the ribosome and of its complexes with factors and inhibitors have provided invaluable information on the mechanism of protein synthesis. Ribosome inhibitors are among the most successful antimicrobial drugs and constitute more than half of all medicines used to treat infections. However, bacterial infections are becoming increasingly difficult to treat because the microbes have developed resistance to the most effective antibiotics, creating a major public health care threat. This has spurred a renewed interest in structure-function studies of protein synthesis inhibitors, and in few cases, compounds have been developed into potent therapeutic agents against drug-resistant pathogens. In this review, we describe the modes of action of many ribosome-targeting antibiotics, highlight the major resistance mechanisms developed by pathogenic bacteria, and discuss recent advances in structure-assisted design of new molecules.
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Affiliation(s)
- Jinzhong Lin
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai 200438, China;
| | - Dejian Zhou
- State Key Laboratory of Genetic Engineering, School of Life Sciences, Zhongshan Hospital, Fudan University, Shanghai 200438, China;
| | - Thomas A Steitz
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, USA; .,Department of Chemistry, Yale University, New Haven, Connecticut 06520, USA.,Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06520, USA
| | - Yury S Polikanov
- Department of Biological Sciences, and Department of Medicinal Chemistry and Pharmacognosy, University of Illinois at Chicago, Chicago, Illinois 60607, USA;
| | - Matthieu G Gagnon
- Department of Molecular Biophysics and Biochemistry, Yale University, New Haven, Connecticut 06520, USA; .,Howard Hughes Medical Institute, Yale University, New Haven, Connecticut 06520, USA.,Current affiliation: Department of Microbiology and Immunology, and Sealy Center for Structural Biology and Molecular Biophysics, University of Texas Medical Branch, Galveston, Texas 77555, USA;
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24
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Gupta A, Bedre R, Thapa SS, Sabrin A, Wang G, Dassanayake M, Grove A. Global Awakening of Cryptic Biosynthetic Gene Clusters in Burkholderia thailandensis. ACS Chem Biol 2017; 12:3012-3021. [PMID: 29087175 DOI: 10.1021/acschembio.7b00681] [Citation(s) in RCA: 26] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Many bacteria encode biosynthetic proteins that produce a vast array of natural products. These compounds are often synthesized during host invasion as they function as virulence factors. In addition, such secondary metabolites have yielded numerous molecular scaffolds with pharmaceutical and clinical importance. The gene clusters that encode proteins responsible for synthesis of these compounds are typically silenced or "cryptic" under laboratory growth conditions, hampering discovery of novel lead compounds. We report here that MftR is a global repressor of secondary metabolite synthesis in Burkholderia thailandensis and that urate functions as a physiologically relevant inducer of gene expression. Biosynthetic gene clusters under MftR control include those associated with production of the antimicrobial bactobolins, the iron siderophore malleobactin, and the virulence factor malleilactone. MftR also controls additional genes associated with survival in a host environment, such as genes encoding components of the type III secretion system (T3SS) and proteins linked to anaerobic respiration. This observation not only has implications for understanding activation of gene regulatory networks during host invasion, but it also paves the way for isolation of novel therapeutic leads.
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Affiliation(s)
- Ashish Gupta
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Renesh Bedre
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Sudarshan Singh Thapa
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Afsana Sabrin
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Guannan Wang
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Maheshi Dassanayake
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
| | - Anne Grove
- Department
of Biological Sciences, ‡School of Plant, Environmental and Soil Sciences, Louisiana State University, Baton Rouge, Louisiana 70803, United States
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25
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Quorum Sensing in Burkholderia pseudomallei and Other Burkholderia species. CURRENT TROPICAL MEDICINE REPORTS 2017. [DOI: 10.1007/s40475-017-0127-1] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
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26
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Masschelein J, Jenner M, Challis GL. Antibiotics from Gram-negative bacteria: a comprehensive overview and selected biosynthetic highlights. Nat Prod Rep 2017. [PMID: 28650032 DOI: 10.1039/c7np00010c] [Citation(s) in RCA: 63] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022]
Abstract
Covering: up to 2017The overwhelming majority of antibiotics in clinical use originate from Gram-positive Actinobacteria. In recent years, however, Gram-negative bacteria have become increasingly recognised as a rich yet underexplored source of novel antimicrobials, with the potential to combat the looming health threat posed by antibiotic resistance. In this article, we have compiled a comprehensive list of natural products with antimicrobial activity from Gram-negative bacteria, including information on their biosynthetic origin(s) and molecular target(s), where known. We also provide a detailed discussion of several unusual pathways for antibiotic biosynthesis in Gram-negative bacteria, serving to highlight the exceptional biocatalytic repertoire of this group of microorganisms.
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Affiliation(s)
- J Masschelein
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, UK.
| | - M Jenner
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, UK.
| | - G L Challis
- Department of Chemistry, University of Warwick, Gibbet Hill Road, Coventry, UK.
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Detection of Burkholderia pseudomallei toxin-mediated inhibition of protein synthesis using a Caenorhabditis elegans ugt-29 biosensor. Sci Rep 2016; 6:27475. [PMID: 27273550 PMCID: PMC4895344 DOI: 10.1038/srep27475] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2016] [Accepted: 05/19/2016] [Indexed: 01/07/2023] Open
Abstract
Toxins are believed to play a crucial role in Burkholderia pseudomallei pathogenicity, however to date, only a few have been identified. The discovery of additional toxic molecules is limited by the lack of a sensitive indicator of B. pseudomallei toxicity. Previously, from a whole genome transcriptome analysis of B. pseudomallei-infected Caenorhabditis elegans, we noted significant overexpression of a number of worm genes encoding detoxification enzymes, indicating the host's attempt to clear bacterial toxic molecules. One of these genes, ugt-29, a family member of UDP-glucuronosyltransferases, was the most robustly induced phase II detoxification gene. In this study, we show that strong induction of ugt-29 is restricted to infections by the most virulent species among the pathogens tested. We also noted that ugt-29 is activated upon disruption of host protein synthesis. Hence, we propose that UGT-29 could be a promising biosensor to detect B. pseudomallei toxins that compromise host protein synthesis. The identification of bactobolin, a polyketide-peptide hybrid molecule, as a toxic molecule of B. pseudomallei further verifies the utilization of this surveillance system to search for bacterial toxins. Hence, a ugt-29 based reporter should be useful in screening for other molecules that inhibit host protein synthesis.
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Arenz S, Wilson DN. Blast from the Past: Reassessing Forgotten Translation Inhibitors, Antibiotic Selectivity, and Resistance Mechanisms to Aid Drug Development. Mol Cell 2015; 61:3-14. [PMID: 26585390 DOI: 10.1016/j.molcel.2015.10.019] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/21/2023]
Abstract
Protein synthesis is a major target within the bacterial cell for antibiotics. Investigations into ribosome-targeting antibiotics have provided much needed functional and structural insight into their mechanism of action. However, the increasing prevalence of multi-drug-resistant bacteria has limited the utility of our current arsenal of clinically relevant antibiotics, highlighting the need for the development of new classes. Recent structural studies have characterized a number of antibiotics discovered decades ago that have unique chemical scaffolds and/or utilize novel modes of action to interact with the ribosome and inhibit translation. Additionally, structures of eukaryotic cytoplasmic and mitochondrial ribosomes have provided further structural insight into the basis for specificity and toxicity of antibiotics. Together with our increased understanding of bacterial resistance mechanisms, revisiting our treasure trove of "forgotten" antibiotics could pave the way for the next generation of antimicrobial agents.
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Affiliation(s)
- Stefan Arenz
- Gene Center and Department of Biochemistry, Feodor-Lynenstr. 25, University of Munich, 81377 Munich, Germany
| | - Daniel N Wilson
- Gene Center and Department of Biochemistry, Feodor-Lynenstr. 25, University of Munich, 81377 Munich, Germany; Center for integrated Protein Science Munich, Feodor-Lynenstr. 25, University of Munich, 81377 Munich, Germany.
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29
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Amunts A, Fiedorczuk K, Truong TT, Chandler J, Greenberg EP, Ramakrishnan V. Bactobolin A binds to a site on the 70S ribosome distinct from previously seen antibiotics. J Mol Biol 2015; 427:753-755. [PMID: 25562208 PMCID: PMC4332689 DOI: 10.1016/j.jmb.2014.12.018] [Citation(s) in RCA: 29] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Revised: 12/12/2014] [Accepted: 12/23/2014] [Indexed: 11/02/2022]
Abstract
The ribosome is the target of a large number of antibiotics. Here, we report a 3.4-Å-resolution crystal structure of bactobolin A bound to 70S ribosome-tRNA complex. The antibiotic binds at a previously unseen site in the 50S subunit and displaces tRNA bound at the P-site. It thus likely has a similar mechanism of action as blasticidin S despite binding to a different site. The structure also rationalizes previously identified resistance mutations.
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Affiliation(s)
- Alexey Amunts
- MRC Laboratory of Molecular Biology, Cambridge CB20QH, UK
| | | | - Thao T Truong
- Department of Microbiology, School of Medicine, University of Washington, Seattle, WA 98195, USA
| | - Josephine Chandler
- Department of Microbiology, School of Medicine, University of Washington, Seattle, WA 98195, USA
| | - E Peter Greenberg
- Department of Microbiology, School of Medicine, University of Washington, Seattle, WA 98195, USA
| | - V Ramakrishnan
- MRC Laboratory of Molecular Biology, Cambridge CB20QH, UK.
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Biot FV, Lopez MM, Poyot T, Neulat-Ripoll F, Lignon S, Caclard A, Thibault FM, Peinnequin A, Pagès JM, Valade E. Interplay between three RND efflux pumps in doxycycline-selected strains of Burkholderia thailandensis. PLoS One 2013; 8:e84068. [PMID: 24386333 PMCID: PMC3873969 DOI: 10.1371/journal.pone.0084068] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2013] [Accepted: 11/11/2013] [Indexed: 11/18/2022] Open
Abstract
Background Efflux systems are involved in multidrug resistance in most Gram-negative non-fermentative bacteria. We have chosen Burkholderia thailandensis to dissect the development of multidrug resistance phenotypes under antibiotic pressure. Methodology/Principal Findings We used doxycycline selection to obtain several resistant B. thailandensis variants. The minimal inhibitory concentrations of a large panel of structurally unrelated antibiotics were determined ± the efflux pump inhibitor phenylalanine-arginine ß-naphthylamide (PAßN). Membrane proteins were identified by proteomic method and the expressions of major efflux pumps in the doxycycline selected variants were compared to those of the parental strains by a quantitative RT-PCR analysis. Doxycycline selected variants showed a multidrug resistance in two major levels corresponding to the overproduction of two efflux pumps depending on its concentration: AmrAB-OprA and BpeEF-OprC. The study of two mutants, each lacking one of these pumps, indicated that a third pump, BpeAB-OprB, could substitute for the defective pump. Surprisingly, we observed antagonistic effects between PAßN and aminoglycosides or some ß-lactams. PAßN induced the overexpression of AmrAB-OprA and BpeAB-OprB pump genes, generating this unexpected effect. Conclusions/Significance These results may account for the weak activity of PAßN in some Gram-negative species. We clearly demonstrated two antagonistic effects of this molecule on bacterial cells: the blocking of antibiotic efflux and an increase in efflux pump gene expression. Thus, doxycycline is a very efficient RND efflux pump inducer and PAßN may promote the production of some efflux pumps. These results should be taken into account when considering antibiotic treatments and in future studies on efflux pump inhibitors.
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Affiliation(s)
- Fabrice Vincent Biot
- Unité de Bactériologie/UMR_MD 1, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France ; UMR_MD 1, Aix Marseille Université, IRBA, Facultés de Médecine et de Pharmacie, Marseille, France
| | - Mélanie Monique Lopez
- Unité de Bactériologie/UMR_MD 1, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France
| | - Thomas Poyot
- Pôle de génomique, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France
| | - Fabienne Neulat-Ripoll
- Unité de Bactériologie/UMR_MD 1, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France ; UMR_MD 1, Aix Marseille Université, IRBA, Facultés de Médecine et de Pharmacie, Marseille, France
| | - Sabrina Lignon
- FR 3479 Plate-forme de Protéomique, CNRS, Aix-Marseille Université, Marseille, France
| | - Arnaud Caclard
- Unité de Bactériologie/UMR_MD 1, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France ; UMR_MD 1, Aix Marseille Université, IRBA, Facultés de Médecine et de Pharmacie, Marseille, France
| | - François Michel Thibault
- Unité de Bactériologie/UMR_MD 1, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France ; UMR_MD 1, Aix Marseille Université, IRBA, Facultés de Médecine et de Pharmacie, Marseille, France
| | - Andre Peinnequin
- Pôle de génomique, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France
| | - Jean-Marie Pagès
- UMR_MD 1, Aix Marseille Université, IRBA, Facultés de Médecine et de Pharmacie, Marseille, France
| | - Eric Valade
- Unité de Bactériologie/UMR_MD 1, Institut de Recherche Biomédicale des Armées, Brétigny-sur-Orge, France ; UMR_MD 1, Aix Marseille Université, IRBA, Facultés de Médecine et de Pharmacie, Marseille, France ; Ecole du Val-de-Grâce, Paris, France
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Liu X, Cheng YQ. Genome-guided discovery of diverse natural products from Burkholderia sp. J Ind Microbiol Biotechnol 2013; 41:275-84. [PMID: 24212473 DOI: 10.1007/s10295-013-1376-1] [Citation(s) in RCA: 54] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/17/2013] [Accepted: 10/24/2013] [Indexed: 01/09/2023]
Abstract
Burkholderia species have emerged as a new source of diverse natural products. This mini-review covers all of the natural products discovered in recent years from Burkholderia sp. by genome-guided approaches--these refer to the use of bacterial genome sequence as an entry point for in silico structural prediction, wet lab experimental design, and execution. While reliable structural prediction based on cryptic biosynthetic gene cluster sequence was not always possible due to noncanonical domains and/or module organization of a deduced biosynthetic pathway, a molecular genetic method was often employed to detect or alter the expression level of the gene cluster to achieve an observable phenotype, which facilitated downstream natural product purification and identification. Those examples of natural product discovery from Burkholderia sp. provide practical guidance for future exploration of Gram-negative bacteria as a new source of natural products.
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Affiliation(s)
- Xiangyang Liu
- UNT System College of Pharmacy, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX, 76107, USA
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Abstract
We constructed a near-saturation transposon mutant library for Burkholderia thailandensis, a low-virulence surrogate for the causative agent of melioidosis (Burkholderia pseudomallei). A primary set of nearly 42,000 unique mutants (~7.5 mutants/gene) was generated using transposon Tn5 derivatives. The strains carry insertions in 87% of the predicted protein-coding genes of the organism, corresponding to nearly all of those nonessential for growth on nutrient agar. To achieve high genome coverage, we developed procedures for efficient sequence identification of insertions in extremely GC-rich regions of DNA. To facilitate strain distribution, we created a secondary library with two mutants per gene for which most transposon locations had been confirmed by resequencing. A map of mutations in the two-allele library and procedures for obtaining strains can be found at http://tools.nwrce.org/tn_mutants/ and http://www.gs.washington.edu/labs/manoil/. The library should facilitate comprehensive mutant screens and serve as a source of strains to test predicted genotype-phenotype associations. The Gram-negative bacterium Burkholderia pseudomallei is a biothreat agent due to its potential for aerosol delivery and intrinsic antibiotic resistance and because exposure produces pernicious infections. Large-scale studies of B. pseudomallei are limited by the fact that the organism must be manipulated under biological safety level 3 conditions. A close relative of B. pseudomallei called Burkholderia thailandensis, which can be studied under less restrictive conditions, has been validated as a low-virulence surrogate in studies of virulence, antibiotic resistance and other traits. To facilitate large-scale studies of B. thailandensis, we created a near-saturation, sequence-defined transposon mutant library of the organism. The library facilitates genetic studies that identify genotype-phenotype associations conserved in B. pseudomallei.
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Abstract
Burkholderia thailandensis produces a family of polyketide-peptide molecules called bactobolins, some of which are potent antibiotics. We found that growth of B. thailandensis at 30°C versus that at 37°C resulted in increased production of bactobolins. We purified the three most abundant bactobolins and determined their activities against a battery of bacteria and mouse fibroblasts. Two of the three compounds showed strong activities against both bacteria and fibroblasts. The third analog was much less potent in both assays. These results suggested that the target of bactobolins might be conserved across bacteria and mammalian cells. To learn about the mechanism of bactobolin activity, we isolated four spontaneous bactobolin-resistant Bacillus subtilis mutants. We used genomic sequencing technology to show that each of the four resistant variants had mutations in rplB, which codes for the 50S ribosome-associated L2 protein. Ectopic expression of a mutant rplB gene in wild-type B. subtilis conferred bactobolin resistance. Finally, the L2 mutations did not confer resistance to other antibiotics known to interfere with ribosome function. Our data indicate that bactobolins target the L2 protein or a nearby site and that this is not the target of other antibiotics. We presume that the mammalian target of bactobolins involves the eukaryotic homolog of L2 (L8e). Currently available antibiotics target surprisingly few cellular functions, and there is a need to identify novel antibiotic targets. We have been interested in the Burkholderia thailandensis bactobolins, and we sought to learn about the target of bactobolin activity by mapping spontaneous resistance mutations in the bactobolin-sensitive Bacillus subtilis. Our results indicate that the bactobolin target is the 50S ribosome-associated L2 protein or a region of the ribosome affected by L2. Bactobolin-resistant mutants are not resistant to other known ribosome inhibitors. Our evidence indicates that bactobolins interact with a novel antibiotic target.
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Revised genome sequence of Burkholderia thailandensis MSMB43 with improved annotation. J Bacteriol 2012; 194:4749-50. [PMID: 22887659 DOI: 10.1128/jb.00931-12] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
There is growing interest in discovery of novel bioactive natural products from Burkholderia thailandensis. Here we report a significantly improved genome sequence and reannotation of Burkholderia thailandensis MSMB43, which will facilitate the discovery of new natural products through genome mining and studies of the metabolic versatility of this bacterium.
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Chandler JR, Heilmann S, Mittler JE, Greenberg EP. Acyl-homoserine lactone-dependent eavesdropping promotes competition in a laboratory co-culture model. ISME JOURNAL 2012; 6:2219-28. [PMID: 22763647 DOI: 10.1038/ismej.2012.69] [Citation(s) in RCA: 63] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Many Proteobacteria use acyl-homoserine lactone (AHL)-mediated quorum sensing to activate the production of antibiotics at high cell density. Extracellular factors like antibiotics can be considered public goods shared by individuals within a group. Quorum-sensing control of antibiotic production may be important for protecting a niche or competing for limited resources in mixed bacterial communities. To begin to investigate the role of quorum sensing in interspecies competition, we developed a dual-species co-culture model using the soil saprophytes Burkholderia thailandensis (Bt) and Chromobacterium violaceum (Cv). These bacteria require quorum sensing to activate the production of antimicrobial factors that inhibit growth of the other species. We demonstrate that quorum-sensing-dependent antimicrobials can provide a competitive advantage to either Bt or Cv by inhibiting growth of the other species in co-culture. Although the quorum-sensing signals differ for each species, we show that the promiscuous signal receptor encoded by Cv can sense signals produced by Bt, and that this ability to eavesdrop on Bt can provide Cv an advantage in certain situations. We use an in silico approach to investigate the effect of eavesdropping in competition, and show conditions where early activation of antibiotic production resulting from eavesdropping can promote competitiveness. Our work supports the idea that quorum sensing is important for interspecies competition and that promiscuous signal receptors allow eavesdropping on competitors in mixed microbial habitats.
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Affiliation(s)
- Josephine R Chandler
- Department of Microbiology, University of Washington School of Medicine, Seattle, WA, USA
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