1
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Azarnoosh R, Yarahmadi F, Keshavarz-Tohid V, Rajabpour A. Isolation and identification of rhizospheric pseudomonads with insecticidal effects from various crops in Khuzestan Province, Iran. J Invertebr Pathol 2024; 204:108099. [PMID: 38556196 DOI: 10.1016/j.jip.2024.108099] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2024] [Revised: 03/22/2024] [Accepted: 03/28/2024] [Indexed: 04/02/2024]
Abstract
Pseudomonas bacteria include a variety of species with distinct characteristics. Some species within this genus are known for their ability to stimulate plant growth. Recently, the potential of these bacteria in controlling insect pests has been documented. In this study, 58 bacterial isolates were purified from rhizospheres of wheat, broad bean and canola that were collected from different fields of Khuzestan province in south-west of Iran. With biochemical tests 19 non plant pathogenic pseudomonads strains were detected and their lethal effects on the eggs and larvae of Ephestia keuhniella as an important pest that infests stored products, were evaluated under laboratory conditions. For the bioassays, two concentrations of each strain were administered, and the 5th instar larvae and eggs of the pest were subjected to treatment. Mortality rates were recorded after 24 h. The results showed that all isolated Pseudomonad strains of this study had insecticidal effects against eggs and larvae of E. keuhniella. The strains AWI1, AWI2, AWI7, ABI12, ABI15 and ABI16 displayed the highest mortality rate (91.1 %, 86.2 %, 82.3 %, 84.2, 90.5 % and 90.5 %, respectively). Molecular identification and phylogeny tree according to 16 s rRNA sequencing clarified that AWI1, AWI2 belong to P. plecoglossicida, AWI5 belongs to P. lini, ABI12, ABI15 and ABI16 belong to P. taiwanensis. Moreover, the bacterial efficacy at a suspension concentration of 0.5 OD (80 %) was significantly greater than that at a concentration of 0.2 OD (63.33 %). No significant difference was detected in the response of the pest larvae or eggs to the different strains. Furthermore, olfactory trials revealed that the female parasitoid wasp Habrabracon hebetor actively avoided the infection of the treated larvae by the strains. These findings have practical implications for the development of microbiological pest control strategies.
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Affiliation(s)
- Roghayeh Azarnoosh
- Department of Plant Protection, Faculty of Agriculture, Agricultural Sciences and Natural Resources University of Khuzestan, Bavi, Khuzestan Province, Iran
| | - Fatemeh Yarahmadi
- Department of Plant Protection, Faculty of Agriculture, Agricultural Sciences and Natural Resources University of Khuzestan, Bavi, Khuzestan Province, Iran.
| | - Vahid Keshavarz-Tohid
- Department of Plant Protection, Faculty of Agriculture, Agricultural Sciences and Natural Resources University of Khuzestan, Bavi, Khuzestan Province, Iran.
| | - Ali Rajabpour
- Department of Plant Protection, Faculty of Agriculture, Agricultural Sciences and Natural Resources University of Khuzestan, Bavi, Khuzestan Province, Iran
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2
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Fabian B, Foster C, Asher A, Hassan K, Paulsen I, Tetu S. Identifying the suite of genes central to swimming in the biocontrol bacterium Pseudomonas protegens Pf-5. Microb Genom 2024; 10:001212. [PMID: 38546328 PMCID: PMC11004494 DOI: 10.1099/mgen.0.001212] [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: 01/01/2024] [Accepted: 02/20/2024] [Indexed: 04/12/2024] Open
Abstract
Swimming motility is a key bacterial trait, important to success in many niches. Biocontrol bacteria, such as Pseudomonas protegens Pf-5, are increasingly used in agriculture to control crop diseases, where motility is important for colonization of the plant rhizosphere. Swimming motility typically involves a suite of flagella and chemotaxis genes, but the specific gene set employed for both regulation and biogenesis can differ substantially between organisms. Here we used transposon-directed insertion site sequencing (TraDIS), a genome-wide approach, to identify 249 genes involved in P. protegens Pf-5 swimming motility. In addition to the expected flagella and chemotaxis, we also identified a suite of additional genes important for swimming, including genes related to peptidoglycan turnover, O-antigen biosynthesis, cell division, signal transduction, c-di-GMP turnover and phosphate transport, and 27 conserved hypothetical proteins. Gene knockout mutants and TraDIS data suggest that defects in the Pst phosphate transport system lead to enhanced swimming motility. Overall, this study expands our knowledge of pseudomonad motility and highlights the utility of a TraDIS-based approach for analysing the functions of thousands of genes. This work sets a foundation for understanding how swimming motility may be related to the inconsistency in biocontrol bacteria performance in the field.
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Affiliation(s)
- B.K. Fabian
- School of Natural Sciences, Macquarie University, Sydney, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, Australia
| | - C. Foster
- School of Natural Sciences, Macquarie University, Sydney, Australia
| | - A. Asher
- School of Natural Sciences, Macquarie University, Sydney, Australia
| | - K.A. Hassan
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, Australia
- School of Environmental and Life Sciences, University of Newcastle, Newcastle, Australia
| | - I.T. Paulsen
- School of Natural Sciences, Macquarie University, Sydney, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, Australia
| | - S.G. Tetu
- School of Natural Sciences, Macquarie University, Sydney, Australia
- ARC Centre of Excellence in Synthetic Biology, Macquarie University, Sydney, Australia
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3
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Wang B, Xu F, Zhang Z, Shen D, Wang L, Wu H, Yan Q, Cui C, Wang P, Wei Q, Shao X, Wang M, Qian G. Type IV secretion system effector sabotages multiple defense systems in a competing bacterium. THE ISME JOURNAL 2024; 18:wrae121. [PMID: 38959853 PMCID: PMC11253431 DOI: 10.1093/ismejo/wrae121] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/25/2024] [Revised: 06/22/2024] [Accepted: 07/02/2024] [Indexed: 07/05/2024]
Abstract
Effector proteins secreted by bacteria that infect mammalian and plant cells often subdue eukaryotic host cell defenses by simultaneously affecting multiple targets. However, instances when a bacterial effector injected in the competing bacteria sabotage more than a single target have not been reported. Here, we demonstrate that the effector protein, LtaE, translocated by the type IV secretion system from the soil bacterium Lysobacter enzymogenes into the competing bacterium, Pseudomonas protegens, affects several targets, thus disabling the antibacterial defenses of the competitor. One LtaE target is the transcription factor, LuxR1, that regulates biosynthesis of the antimicrobial compound, orfamide A. Another target is the sigma factor, PvdS, required for biosynthesis of another antimicrobial compound, pyoverdine. Deletion of the genes involved in orfamide A and pyoverdine biosynthesis disabled the antibacterial activity of P. protegens, whereas expression of LtaE in P. protegens resulted in the near-complete loss of the antibacterial activity against L. enzymogenes. Mechanistically, LtaE inhibits the assembly of the RNA polymerase complexes with each of these proteins. The ability of LtaE to bind to LuxR1 and PvdS homologs from several Pseudomonas species suggests that it can sabotage defenses of various competitors present in the soil or on plant matter. Our study thus reveals that the multi-target effectors have evolved to subdue cell defenses not only in eukaryotic hosts but also in bacterial competitors.
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Affiliation(s)
- Bingxin Wang
- College of Plant Protection (Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing 210095, P.R. China
| | - Fugui Xu
- College of Plant Protection (Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing 210095, P.R. China
| | - Zeyu Zhang
- College of Plant Protection (Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing 210095, P.R. China
| | - Danyu Shen
- College of Plant Protection (Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing 210095, P.R. China
| | - Limin Wang
- College of Plant Protection (Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing 210095, P.R. China
| | - Huijun Wu
- College of Plant Protection (Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing 210095, P.R. China
| | - Qing Yan
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717, United States
| | - Chuanbin Cui
- Department of Plant Pathology, Shaanxi Provincial Tobacco Corporation of CNTC, Xi'an 710061, China
| | - Pingping Wang
- Department of Plant Pathology, Shaanxi Provincial Tobacco Corporation of CNTC, Xi'an 710061, China
| | - Qi Wei
- Industrial Crops Institute, Heilongjiang Academy of Agricultural Sciences, Harbin 150086, China
| | - Xiaolong Shao
- College of Plant Protection (Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing 210095, P.R. China
| | - Mengcen Wang
- State Key Laboratory of Rice Biology and Breeding, Zhejiang University, Hangzhou 310058, China
- Ministry of Agricultural and Rural Affairs Laboratory of Molecular Biology of Crop Pathogens and Insects, Institute of Pesticide and Environmental Toxicology, College of Agriculture and Biotechnology, Zhejiang University, Hangzhou 310058, China
| | - Guoliang Qian
- College of Plant Protection (Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing 210095, P.R. China
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4
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Wang B, Zhang Z, Xu F, Yang Z, Li Z, Shen D, Wang L, Wu H, Li T, Yan Q, Wei Q, Shao X, Qian G. Soil bacterium manipulates antifungal weapons by sensing intracellular type IVA secretion system effectors of a competitor. THE ISME JOURNAL 2023; 17:2232-2246. [PMID: 37838821 PMCID: PMC10689834 DOI: 10.1038/s41396-023-01533-7] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2023] [Revised: 09/22/2023] [Accepted: 10/05/2023] [Indexed: 10/16/2023]
Abstract
Soil beneficial bacteria can effectively inhibit bacterial pathogens by assembling contact-dependent killing weapons, such as the type IVA secretion system (T4ASS). It's not clear whether these antibacterial weapons are involved in biotrophic microbial interactions in soil. Here we showed that an antifungal antibiotic 2,4-DAPG production of the soil bacterium, Pseudomonas protegens can be triggered by another soil bacterium, Lysobacter enzymogenes, via T4ASS by co-culturing on agar plates to mimic cell-to-cell contact. We demonstrated that the induced 2,4-DAPG production of P. protegens is achieved by intracellular detection of the T4ASS effector protein Le1519 translocated from L. enzymogenes. We defined Le1519 as LtaE (Lysobacter T4E triggering antifungal effects), which specifically stimulates the expression of 2,4-DAPG biosynthesis genes in P. protegens, thereby protecting soybean seedlings from infection by the fungus Rhizoctonia solani. We further found that LtaE directly bound to PhlF, a pathway-specific transcriptional repressor of the 2,4-DAPG biosynthesis, then activated the 2,4-DAPG production. Our results highlight a novel pattern of microbial interspecies and interkingdom interactions, providing a unique case for expanding the diversity of soil microbial interactions.
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Affiliation(s)
- Bingxin Wang
- College of Plant Protection (State Key Laboratory of Biological interactions and Crop Health; Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing, 210095, P.R. China
| | - Zeyu Zhang
- College of Plant Protection (State Key Laboratory of Biological interactions and Crop Health; Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing, 210095, P.R. China
| | - Fugui Xu
- College of Plant Protection (State Key Laboratory of Biological interactions and Crop Health; Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing, 210095, P.R. China
| | - Zixiang Yang
- College of Plant Protection (State Key Laboratory of Biological interactions and Crop Health; Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing, 210095, P.R. China
| | - Zihan Li
- College of Plant Protection (State Key Laboratory of Biological interactions and Crop Health; Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing, 210095, P.R. China
| | - Danyu Shen
- College of Plant Protection (State Key Laboratory of Biological interactions and Crop Health; Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing, 210095, P.R. China
| | - Limin Wang
- College of Plant Protection (State Key Laboratory of Biological interactions and Crop Health; Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing, 210095, P.R. China
| | - Huijun Wu
- College of Plant Protection (State Key Laboratory of Biological interactions and Crop Health; Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing, 210095, P.R. China
| | - Tao Li
- Shanghai Veterinary Research Institute, Chinese Academy of Agricultural Sciences, Shanghai, 200241, PR China
| | - Qing Yan
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT, 59717, USA
| | - Qi Wei
- Industrial Crops Institute, Heilongjiang Academy of Agricultural Sciences, Harbin, 150086, China
| | - Xiaolong Shao
- College of Plant Protection (State Key Laboratory of Biological interactions and Crop Health; Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing, 210095, P.R. China
| | - Guoliang Qian
- College of Plant Protection (State Key Laboratory of Biological interactions and Crop Health; Key Laboratory of Integrated Management of Crop Diseases and Pests), Nanjing Agricultural University, Nanjing, 210095, P.R. China.
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5
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Zhang QX, Xiong ZW, Li SY, Yin Y, Xing CL, Wen DY, Xu J, Liu Q. Regulatory roles of RpoS in the biosynthesis of antibiotics 2,4-diacetyphloroglucinol and pyoluteorin of Pseudomonas protegens FD6. Front Microbiol 2022; 13:993732. [PMID: 36583049 PMCID: PMC9793710 DOI: 10.3389/fmicb.2022.993732] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Accepted: 11/21/2022] [Indexed: 12/14/2022] Open
Abstract
The rhizosphere microbe Pseudomonas protegens FD6 possesses beneficial traits such as the production of antibiotics like pyoluteorin (Plt) and 2,4-diacetylphloroglucinol (2,4-DAPG). The alternative RpoS (σ38 factor), as a master regulator, activates or inhibits the transcription of stationary phase genes in several biocontrol organisms. Here, we investigated the complicated function and regulatory mechanism of RpoS in the biosynthesis of 2,4-DAPG and Plt in strain FD6. Phenotypic assays suggested that ΔrpoS was impaired in biofilm formation, swimming motility, swarming motility, and resistance to stress, such as heat, H2O2 and 12% ethanol. The RpoS mutation significantly increased both 2,4-DAPG and Plt production and altered the transcription and translation of the biosynthetic genes phlA and pltL, indicating that RpoS inhibited antibiotic production by FD6 at both the transcriptional and translational levels. RpoS negatively controlled 2,4-DAPG biosynthesis and transcription of the 2,4-DAPG operon phlACBD by directly interacting with the promoter sequences of phlG and phlA. In addition, RpoS significantly inhibited Plt production and the expression of its operon pltLABCDEFG by directly binding to the promoter regions of pltR, pltL and pltF. Further analyzes demonstrated that a putative R147 mutation in the RpoS binding domain abolished its inhibitory activity on the expression of pltL and phlA. Overall, our results reveal the pleiotropic regulatory function of RpoS in P. protegens FD6 and provide the basis for improving antibiotic biosynthesis by genetic engineering in biocontrol organisms.
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Affiliation(s)
- Qing Xia Zhang
- College of Plant Protection, Yangzhou University, Yangzhou, China,*Correspondence: Qing Xia Zhang,
| | - Zheng Wen Xiong
- College of Plant Protection, Yangzhou University, Yangzhou, China
| | - Shen Yu Li
- College of Plant Protection, Yangzhou University, Yangzhou, China
| | - Yue Yin
- College of Resources and Environmental Sciences, Nanjing Agricultural University, Nanjing, China
| | - Cheng Lin Xing
- College of Plant Protection, Yangzhou University, Yangzhou, China
| | - De Yu Wen
- College of Plant Protection, Yangzhou University, Yangzhou, China
| | - Jian Xu
- Jiangsu Lixiahe District Institute of Agricultural Sciences, Yangzhou, China
| | - Qin Liu
- Jiangsu Lixiahe District Institute of Agricultural Sciences, Yangzhou, China,Qin Liu,
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6
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Lai X, Niroula D, Burrows M, Wu X, Yan Q. Identification and Characterization of Bacteria-Derived Antibiotics for the Biological Control of Pea Aphanomyces Root Rot. Microorganisms 2022; 10:microorganisms10081596. [PMID: 36014014 PMCID: PMC9416638 DOI: 10.3390/microorganisms10081596] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2022] [Revised: 07/30/2022] [Accepted: 08/04/2022] [Indexed: 11/24/2022] Open
Abstract
Antibiosis has been proposed to contribute to the beneficial bacteria-mediated biocontrol against pea Aphanomyces root rot caused by the oomycete pathogen Aphanomyces euteiches. However, the antibiotics required for disease suppression remain unknown. In this study, we found that the wild type strains of Pseudomonas protegens Pf-5 and Pseudomonas fluorescens 2P24, but not their mutants that lack 2,4-diacetylphloroglucinol, strongly inhibited A. euteiches on culture plates. Purified 2,4-diacetylphloroglucinol compound caused extensive hyphal branching and stunted hyphal growth of A. euteiches. Using a GFP-based transcriptional reporter assay, we found that expression of the 2,4-diacetylphloroglucinol biosynthesis gene phlAPf-5 is activated by germinating pea seeds. The 2,4-diacetylphloroglucinol producing Pf-5 derivative, but not its 2,4-diacetylphloroglucinol non-producing mutant, reduced disease severity caused by A. euteiches on pea plants in greenhouse conditions. This is the first report that 2,4-diacetylphloroglucinol produced by strains of Pseudomonas species plays an important role in the biocontrol of pea Aphanomyces root rot.
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Affiliation(s)
- Xiao Lai
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717, USA
| | - Dhirendra Niroula
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717, USA
| | - Mary Burrows
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717, USA
| | - Xiaogang Wu
- College of Agriculture, Guangxi University, Nanning 530004, China
- Correspondence: (X.W.); (Q.Y.)
| | - Qing Yan
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, MT 59717, USA
- Correspondence: (X.W.); (Q.Y.)
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7
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López-Pliego L, Lara-Flores N, Molina-Romero D, May-Compañ G, Carreño-López R, Núñez CE, Castañeda M. The GacS/A-Rsm Pathway Positively Regulates Motility and Flagella Synthesis in Azotobacter vinelandii. Curr Microbiol 2021; 79:17. [PMID: 34905080 DOI: 10.1007/s00284-021-02695-3] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2021] [Accepted: 10/21/2021] [Indexed: 10/19/2022]
Abstract
Azotobacter vinelandii is a motile bacterium that possesses an unusual pattern of peritrichous flagellation for members of the Pseudomonadaceae family. Unlike what has been reported for Pseudomonas spp. FleQ is not the master regulator of motility in A. vinelandii, this role is performed by FlhDC. Other factors involved in the regulation of motility are AlgU (σE) and CydR which act as negative regulators. In some members of the Enterobacteriaceae and Pseudomonadaceae families, the GacS/A-Rsm pathway is another important factor regulating motility. In the present study, the involvement of the GacS/A-Rsm pathway in regulating the motility of A. vinelandii was explored; we found that contrary to what has been reported for most of the strains studied of Pseudomonas species, GacS/A, through the Rsm system, positively controlled swimming motility. We show that the target of this regulation is the synthesis of flagella, which most likely occurs in an FlhDC-independent manner.
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Affiliation(s)
- Liliana López-Pliego
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, IC-11 Ciudad Universitaria, Apdo, Postal 1622, C. P. 72000, Puebla, Pue, México
| | - Norarizbeth Lara-Flores
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, IC-11 Ciudad Universitaria, Apdo, Postal 1622, C. P. 72000, Puebla, Pue, México.,Facultad de Medicina, Benemérita Universidad Autónoma de Puebla, 13 Sur 2702, C. P. 72410, Puebla, Pue, México
| | - Dalia Molina-Romero
- Facultad de Ciencias Biológicas, BIO-1 Ciudad Universitaria, C. P. 72000, Puebla, Pue, México
| | - Gabriela May-Compañ
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, IC-11 Ciudad Universitaria, Apdo, Postal 1622, C. P. 72000, Puebla, Pue, México.,Facultad de Medicina, Benemérita Universidad Autónoma de Puebla, 13 Sur 2702, C. P. 72410, Puebla, Pue, México
| | - Ricardo Carreño-López
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, IC-11 Ciudad Universitaria, Apdo, Postal 1622, C. P. 72000, Puebla, Pue, México
| | - Cinthia E Núñez
- Departamento de Microbiología Molecular, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Apdo, Postal 510-3, C. P. 62250, Cuernavaca, Mor, México
| | - Miguel Castañeda
- Centro de Investigaciones en Ciencias Microbiológicas, Instituto de Ciencias, Benemérita Universidad Autónoma de Puebla, IC-11 Ciudad Universitaria, Apdo, Postal 1622, C. P. 72000, Puebla, Pue, México.
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8
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Rose MM, Scheer D, Hou Y, Hotter VS, Komor AJ, Aiyar P, Scherlach K, Vergara F, Yan Q, Loper JE, Jakob T, van Dam NM, Hertweck C, Mittag M, Sasso S. The bacterium Pseudomonas protegens antagonizes the microalga Chlamydomonas reinhardtii using a blend of toxins. Environ Microbiol 2021; 23:5525-5540. [PMID: 34347373 DOI: 10.1111/1462-2920.15700] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2021] [Revised: 06/24/2021] [Accepted: 07/31/2021] [Indexed: 11/27/2022]
Abstract
The unicellular alga Chlamydomonas reinhardtii and the bacterium Pseudomonas protegens serve as a model to study the interactions between photosynthetic and heterotrophic microorganisms. P. protegens secretes the cyclic lipopeptide orfamide A that interferes with cytosolic Ca2+ homeostasis in C. reinhardtii resulting in deflagellation of the algal cells. Here, we studied the roles of additional secondary metabolites secreted by P. protegens using individual compounds and co-cultivation of algae with bacterial mutants. Rhizoxin S2, pyrrolnitrin, pyoluteorin, 2,4-diacetylphloroglucinol (DAPG) and orfamide A all induce changes in cell morphology and inhibit the growth of C. reinhardtii. Rhizoxin S2 exerts the strongest growth inhibition, and its action depends on the spatial structure of the environment (agar versus liquid culture). Algal motility is unaffected by rhizoxin S2 and is most potently inhibited by orfamide A (IC50 = 4.1 μM). Pyrrolnitrin and pyoluteorin both interfere with algal cytosolic Ca2+ homeostasis and motility whereas high concentrations of DAPG immobilize C. reinhardtii without deflagellation or disturbance of Ca2+ homeostasis. Co-cultivation with a regulatory mutant of bacterial secondary metabolism (ΔgacA) promotes algal growth under spatially structured conditions. Our results reveal how a single soil bacterium uses an arsenal of secreted antialgal compounds with complementary and partially overlapping activities.
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Affiliation(s)
- Magdalena M Rose
- Institute of Biology, Leipzig University, Leipzig, Germany.,Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University Jena, Jena, Germany
| | - Daniel Scheer
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University Jena, Jena, Germany
| | - Yu Hou
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University Jena, Jena, Germany
| | - Vivien S Hotter
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University Jena, Jena, Germany
| | - Anna J Komor
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany
| | - Prasad Aiyar
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University Jena, Jena, Germany
| | - Kirstin Scherlach
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany
| | - Fredd Vergara
- German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany.,Institute of Biodiversity, Friedrich Schiller University Jena, Jena, Germany
| | - Qing Yan
- Department of Plant Sciences and Plant Pathology, Montana State University, Bozeman, Montana, USA
| | - Joyce E Loper
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA
| | - Torsten Jakob
- Institute of Biology, Leipzig University, Leipzig, Germany
| | - Nicole M van Dam
- German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany.,Institute of Biodiversity, Friedrich Schiller University Jena, Jena, Germany
| | - Christian Hertweck
- Department of Biomolecular Chemistry, Leibniz Institute for Natural Product Research and Infection Biology (HKI), Jena, Germany.,Faculty of Biological Sciences, Friedrich Schiller University Jena, Jena, Germany
| | - Maria Mittag
- Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University Jena, Jena, Germany
| | - Severin Sasso
- Institute of Biology, Leipzig University, Leipzig, Germany.,Matthias Schleiden Institute of Genetics, Bioinformatics and Molecular Botany, Friedrich Schiller University Jena, Jena, Germany.,German Centre for Integrative Biodiversity Research (iDiv) Halle-Jena-Leipzig, Leipzig, Germany
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9
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Takeuchi K, Tsuchiya W, Fujimoto Z, Yamada K, Someya N, Yamazaki T. Discovery of an Antibiotic-Related Small Protein of Biocontrol Strain Pseudomonas sp. Os17 by a Genome-Mining Strategy. Front Microbiol 2020; 11:605705. [PMID: 33324389 PMCID: PMC7726476 DOI: 10.3389/fmicb.2020.605705] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2020] [Accepted: 10/26/2020] [Indexed: 11/13/2022] Open
Abstract
Many root-colonizing Pseudomonas spp. exhibiting biocontrol activities produce a wide range of secondary metabolites that exert antibiotic effects against other microbes, nematodes, and insects in the rhizosphere. The expression of these secondary metabolites depends on the Gac/Rsm signal transduction pathway. Based on the findings of a previous genomic study on newly isolated biocontrol pseudomonad strains, we herein investigated the novel gene cluster OS3, which consists of four genes (Os1348–Os1351) that are located upstream of putative efflux transporter genes (Os1352–Os1355). Os1348 was predicted to encode an 85-aa small precursor protein, the expression of which was under the control of GacA, and an X-ray structural analysis suggested that the Os1348 protein formed a dimer. The mutational loss of the Os1348 gene decreased the antibiotic activity of Pseudomonas sp. Os17 without changing its growth rate. The Os1349–1351 genes were predicted to be involved in post-translational modifications. Intracellular levels of the Os1348 protein in the deficient mutant of each gene differed from that in wild-type cells. These results suggest that Os1348 is involved in antibiotic activity and that the structure or expression of this protein is under the control of downstream gene products.
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Affiliation(s)
- Kasumi Takeuchi
- Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Wataru Tsuchiya
- Structural Biology Team, Advanced Analysis Center, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Zui Fujimoto
- Structural Biology Team, Advanced Analysis Center, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Kosumi Yamada
- Graduate School of Life and Environmental Sciences, University of Tsukuba, Tsukuba, Japan
| | - Nobutaka Someya
- Division of Vegetable Production System, Institute of Vegetable and Floriculture Science, National Agriculture and Food Research Organization, Tsukuba, Japan
| | - Toshimasa Yamazaki
- Structural Biology Team, Advanced Analysis Center, National Agriculture and Food Research Organization, Tsukuba, Japan
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10
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Latour X. The Evanescent GacS Signal. Microorganisms 2020; 8:microorganisms8111746. [PMID: 33172195 PMCID: PMC7695008 DOI: 10.3390/microorganisms8111746] [Citation(s) in RCA: 17] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/06/2020] [Revised: 11/02/2020] [Accepted: 11/04/2020] [Indexed: 12/18/2022] Open
Abstract
The GacS histidine kinase is the membrane sensor of the major upstream two-component system of the regulatory Gac/Rsm signal transduction pathway. This pathway governs the expression of a wide range of genes in pseudomonads and controls bacterial fitness and motility, tolerance to stress, biofilm formation, and virulence or plant protection. Despite the importance of these roles, the ligands binding to the sensor domain of GacS remain unknown, and their identification is an exciting challenge in this domain. At high population densities, the GacS signal triggers a switch from primary to secondary metabolism and a change in bacterial lifestyle. It has been suggested, based on these observations, that the GacS signal is a marker of the emergence of nutritional stress and competition. Biochemical investigations have yet to characterize the GacS signal fully. However, they portray this cue as a low-molecular weight, relatively simple and moderately apolar metabolite possibly resembling, but nevertheless different, from the aliphatic organic acids acting as quorum-sensing signaling molecules in other Proteobacteria. Significant progress in the development of metabolomic tools and new databases dedicated to Pseudomonas metabolism should help to unlock some of the last remaining secrets of GacS induction, making it possible to control the Gac/Rsm pathway.
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Affiliation(s)
- Xavier Latour
- Laboratory of Microbiology Signals and Microenvironment (LMSM EA 4312), Normandy University (University of Rouen Normandy), 55 rue Saint-Germain, 27000 Evreux, France;
- Research Federation NORVEGE Fed4277, Normandy University, F-76821 Mont-Saint-Aignan, France
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11
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Ueda A, Ogasawara S, Horiuchi K. Identification of the genes controlling biofilm formation in the plant commensal Pseudomonas protegens Pf-5. Arch Microbiol 2020; 202:2453-2459. [PMID: 32607723 DOI: 10.1007/s00203-020-01966-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2020] [Revised: 06/20/2020] [Accepted: 06/24/2020] [Indexed: 12/20/2022]
Abstract
Determinant genes controlling biofilm formation in a plant commensal bacterium, Pseudomonas protegens Pf-5, were identified by transposon mutagenesis. Comprehensive screening of 7500 transposon-inserted mutants led to the isolation of four mutants exhibiting decreased and five mutants exhibiting increased biofilm formation. Mutations in the genes encoding MFS drug resistance transporter, LapA adhesive protein, RetS sensor histidine kinase/response regulator, and HecA adhesin/hemagglutinin led to decreased biofilm formation, indicating that these genes are necessary for biofilm formation in Pf-5. The mutants exhibiting increased biofilm formation had transposon insertions in the genes coding for an outer membrane protein, a GGDEF domain-containing protein, AraC transcriptional regulator, non-ribosomal peptide synthetase OfaB, and the intergenic region of a DNA-binding protein and the Aer aerotaxis receptor, suggesting that these genes are negative regulators of biofilm formation. Some of these mutants also showed altered swimming and swarming motilities, and a negative correlation between biofilm formation and swarming motility was observed. Thus, sessile-motile lifestyle is regulated by divergent regulatory genes in Pf-5.
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Affiliation(s)
- Akihiro Ueda
- Graduate School of Integrated Sciences for Life, Hiroshima University, Higashi-Hiroshima, 739-8528, Japan.
- Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, 739-8528, Japan.
| | - Shinta Ogasawara
- Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, 739-8528, Japan
| | - Keishi Horiuchi
- School of Applied Biological Science, Hiroshima University, Higashi-Hiroshima, 739-8528, Japan
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12
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Marmont LS, Whitfield GB, Pfoh R, Williams RJ, Randall TE, Ostaszewski A, Razvi E, Groves RA, Robinson H, Nitz M, Parsek MR, Lewis IA, Whitney JC, Harrison JJ, Howell PL. PelX is a UDP- N-acetylglucosamine C4-epimerase involved in Pel polysaccharide-dependent biofilm formation. J Biol Chem 2020; 295:11949-11962. [PMID: 32601062 PMCID: PMC7443510 DOI: 10.1074/jbc.ra120.014555] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2020] [Revised: 06/24/2020] [Indexed: 12/15/2022] Open
Abstract
Pel is a GalNAc-rich bacterial polysaccharide that contributes to the structure and function of Pseudomonas aeruginosa biofilms. The pelABCDEFG operon is highly conserved among diverse bacterial species, and Pel may therefore be a widespread biofilm determinant. Previous annotation of pel gene clusters has helped us identify an additional gene, pelX, that is present adjacent to pelABCDEFG in >100 different bacterial species. The pelX gene is predicted to encode a member of the short-chain dehydrogenase/reductase (SDR) superfamily, but its potential role in Pel-dependent biofilm formation is unknown. Herein, we have used Pseudomonas protegens Pf-5 as a model to elucidate PelX function as Pseudomonas aeruginosa lacks a pelX homologue in its pel gene cluster. We found that P. protegens forms Pel-dependent biofilms; however, despite expression of pelX under these conditions, biofilm formation was unaffected in a ΔpelX strain. This observation led us to identify a pelX paralogue, PFL_5533, which we designate here PgnE, that appears to be functionally redundant to pelX In line with this, a ΔpelX ΔpgnE double mutant was substantially impaired in its ability to form Pel-dependent biofilms. To understand the molecular basis for this observation, we determined the structure of PelX to 2.1 Å resolution. The structure revealed that PelX resembles UDP-GlcNAc C4-epimerases. Using 1H NMR analysis, we show that PelX catalyzes the epimerization between UDP-GlcNAc and UDP-GalNAc. Our results indicate that Pel-dependent biofilm formation requires a UDP-GlcNAc C4-epimerase that generates the UDP-GalNAc precursors required by the Pel synthase machinery for polymer production.
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Affiliation(s)
- Lindsey S Marmont
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Gregory B Whitfield
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Roland Pfoh
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada
| | - Rohan J Williams
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Trevor E Randall
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | | | - Erum Razvi
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Ryan A Groves
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - Howard Robinson
- Photon Science Division, Brookhaven National Laboratory, Upton, New York, USA
| | - Mark Nitz
- Department of Chemistry, University of Toronto, Toronto, Ontario, Canada
| | - Matthew R Parsek
- Department of Microbiology, University of Washington, Seattle, Washington, USA
| | - Ian A Lewis
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - John C Whitney
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada
| | - Joe J Harrison
- Department of Biological Sciences, University of Calgary, Calgary, Alberta, Canada
| | - P Lynne Howell
- Program in Molecular Medicine, The Hospital for Sick Children, Toronto, Ontario, Canada; Department of Biochemistry, University of Toronto, Toronto, Ontario, Canada.
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13
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Jahanshah G, Yan Q, Gerhardt H, Pataj Z, Lämmerhofer M, Pianet I, Josten M, Sahl HG, Silby MW, Loper JE, Gross H. Discovery of the Cyclic Lipopeptide Gacamide A by Genome Mining and Repair of the Defective GacA Regulator in Pseudomonas fluorescens Pf0-1. JOURNAL OF NATURAL PRODUCTS 2019; 82:301-308. [PMID: 30666877 DOI: 10.1021/acs.jnatprod.8b00747] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Genome mining of the Gram-negative bacterium Pseudomonas fluorescens Pf0-1 showed that the strain possesses a silent NRPS-based biosynthetic gene cluster encoding a new lipopeptide; its activation required the repair of the global regulator system. In this paper, we describe the genomics-driven discovery and characterization of the associated secondary metabolite gacamide A, a lipodepsipeptide that forms a new family of Pseudomonas lipopeptides. The compound has a moderate, narrow-spectrum antibiotic activity and facilitates bacterial surface motility.
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Affiliation(s)
- Gahzaleh Jahanshah
- Pharmaceutical Institute, Department of Pharmaceutical Biology , University of Tübingen , 72076 Tübingen , Germany
- German Centre for Infection Research (DZIF) , partner site Tübingen , 72076 Tübingen , Germany
| | - Qing Yan
- Department of Botany and Plant Pathology , Oregon State University , Corvallis , Oregon 97331 , United States
| | - Heike Gerhardt
- Pharmaceutical Institute, Department of Pharmaceutical Analysis and Bioanalysis , University of Tübingen , 72076 Tübingen , Germany
- UMR 5060, IRAMAT-CRP2A, Esplanade des Antilles , F-33600 Pessac , France
| | - Zoltán Pataj
- Pharmaceutical Institute, Department of Pharmaceutical Analysis and Bioanalysis , University of Tübingen , 72076 Tübingen , Germany
- UMR 5060, IRAMAT-CRP2A, Esplanade des Antilles , F-33600 Pessac , France
| | - Michael Lämmerhofer
- Pharmaceutical Institute, Department of Pharmaceutical Analysis and Bioanalysis , University of Tübingen , 72076 Tübingen , Germany
- UMR 5060, IRAMAT-CRP2A, Esplanade des Antilles , F-33600 Pessac , France
| | - Isabelle Pianet
- CESAMO-ISM, UMR 5255, CNRS , Université Bordeaux I , 351 Cours de la Libération , F-33405 Talence , France
| | - Michaele Josten
- Institute for Medical Microbiology, Immunology and Parasitology (IMMIP), Pharmaceutical Microbiology Unit , University of Bonn , 53115 Bonn , Germany
- German Centre for Infection Research (DZIF) , partner site Bonn-Cologne , 53115 Bonn , Germany
| | - Hans-Georg Sahl
- Institute for Medical Microbiology, Immunology and Parasitology (IMMIP), Pharmaceutical Microbiology Unit , University of Bonn , 53115 Bonn , Germany
- German Centre for Infection Research (DZIF) , partner site Bonn-Cologne , 53115 Bonn , Germany
| | - Mark W Silby
- Department of Biology , University of Massachusetts Dartmouth , North Dartmouth , Massachusetts 02747 , United States
| | - Joyce E Loper
- Department of Botany and Plant Pathology , Oregon State University , Corvallis , Oregon 97331 , United States
- Agricultural Research Service , U.S. Department of Agriculture , Corvallis , Oregon 97331 , United States
| | - Harald Gross
- Pharmaceutical Institute, Department of Pharmaceutical Biology , University of Tübingen , 72076 Tübingen , Germany
- German Centre for Infection Research (DZIF) , partner site Tübingen , 72076 Tübingen , Germany
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14
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Yu F, Jing X, Li X, Wang H, Chen H, Zhong L, Yin J, Pan D, Yin Y, Fu J, Xia L, Bian X, Tu Q, Zhang Y. Recombineering Pseudomonas protegens CHA0: An innovative approach that improves nitrogen fixation with impressive bactericidal potency. Microbiol Res 2019; 218:58-65. [DOI: 10.1016/j.micres.2018.09.009] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Revised: 08/06/2018] [Accepted: 09/28/2018] [Indexed: 10/28/2022]
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15
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Yang Y, Li Y, Gao T, Zhang Y, Wang Q. C-di-GMP turnover influences motility and biofilm formation in Bacillus amyloliquefaciens PG12. Res Microbiol 2018; 169:205-213. [PMID: 29859892 DOI: 10.1016/j.resmic.2018.04.009] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/10/2017] [Revised: 03/22/2018] [Accepted: 04/05/2018] [Indexed: 12/11/2022]
Abstract
Bis-(3'→5') cyclic dimeric guanosine monophosphate (c-di-GMP) is defined as a highly versatile secondary messenger in bacteria, coordinating diverse aspects of bacterial growth and behavior, including motility and biofilm formation. Bacillus amyloliquefaciens PG12 is an effective biocontrol agent against apple ring rot caused by Botryosphaeria dothidea. In this study, we characterized the core regulators of c-di-GMP turnover in B. amyloliquefaciens PG12. Using bioinformatic analysis, heterologous expression and biochemical characterization of knockout and overexpression derivatives, we identified and characterized two active diguanylate cyclases (which catalyze c-di-GMP biosynthesis), YhcK and YtrP and one active c-di-GMP phosphodiesterase (which degrades c-di-GMP), YuxH. Furthermore, we showed that elevating c-di-GMP levels up to a certain threshold inhibited the swimming motility of B. amyloliquefaciens PG12. Although yhcK, ytrP and yuxH knockout mutants did not display defects in biofilm formation, significant increases in c-di-GMP levels induced by YtrP or YuxH overexpression stimulated biofilm formation in B. amyloliquefaciens PG12. Our results indicate that B. amyloliquefaciens possesses a functional c-di-GMP signaling system that influences the bacterium's motility and ability to form biofilms. Since motility and biofilm formation influence the efficacy of biological control agent, our work provides a basis for engineering a more effective strain of B. amyloliquefaciens PG12.
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Affiliation(s)
- Yang Yang
- Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China.
| | - Yan Li
- Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China.
| | - Tantan Gao
- Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China.
| | - Yue Zhang
- Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China.
| | - Qi Wang
- Department of Plant Pathology, College of Plant Protection, China Agricultural University, Beijing 100193, China.
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16
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Park JY, Kang BR, Ryu C, Anderson AJ, Kim YC. Polyamine is a critical determinant of Pseudomonas chlororaphis O6 for GacS-dependent bacterial cell growth and biocontrol capacity. MOLECULAR PLANT PATHOLOGY 2018; 19:1257-1266. [PMID: 28862813 PMCID: PMC6638107 DOI: 10.1111/mpp.12610] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
The Gac/Rsm network regulates, at the transcriptional level, many beneficial traits in biocontrol-active pseudomonads. In this study, we used Phenotype MicroArrays, followed by specific growth studies and mutational analysis, to understand how catabolism is regulated by this sensor kinase system in the biocontrol isolate Pseudomonas chlororaphis O6. The growth of a gacS mutant was decreased significantly relative to that of the wild-type on ornithine and arginine, and on the precursor of these amino acids, N-acetyl-l-glutamic acid. The gacS mutant also showed reduced production of polyamines. Expression of the genes encoding arginine decarboxylase (speA) and ornithine decarboxylases (speC) was controlled at the transcriptional level by the GacS sensor of P. chlororaphis O6. Polyamine production was reduced in the speC mutant, and was eliminated in the speAspeC mutant. The addition of exogenous polyamines to the speAspeC mutant restored the in vitro growth inhibition of two fungal pathogens, as well as the secretion of three biological control-related factors: pyrrolnitrin, protease and siderophore. These results extend our knowledge of the regulation by the Gac/Rsm network in a biocontrol pseudomonad to include polyamine synthesis. Collectively, our studies demonstrate that bacterial polyamines act as important regulators of bacterial cell growth and biocontrol potential.
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Affiliation(s)
- Ju Yeon Park
- Department of Applied BiologyCollege of Agriculture and Life Sciences, Chonnam National UniversityGwangju 61186South Korea
| | - Beom Ryong Kang
- Department of Applied BiologyCollege of Agriculture and Life Sciences, Chonnam National UniversityGwangju 61186South Korea
| | - Choong‐Min Ryu
- Molecular Phytobacteriology LaboratoryInfectious Disease Research Center, KRIBBDaejeon 34141South Korea
| | - Anne J. Anderson
- Department of BioengineeringUtah State UniversityLoganUT 84322‐5305USA
| | - Young Cheol Kim
- Department of Applied BiologyCollege of Agriculture and Life Sciences, Chonnam National UniversityGwangju 61186South Korea
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17
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Takeuchi K. GABA, A Primary Metabolite Controlled by the Gac/Rsm Regulatory Pathway, Favors a Planktonic Over a Biofilm Lifestyle in Pseudomonas protegens CHA0. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2018; 31:274-282. [PMID: 28990487 DOI: 10.1094/mpmi-05-17-0120-r] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/07/2023]
Abstract
In Pseudomonas protegens CHA0 and other fluorescent pseudomonads, the Gac/Rsm signal transduction pathway is crucial for the expression of secondary metabolism and the biological control of fungi, nematodes, and insects. Based on the findings of a previous metabolomic study, the role of intracellular γ-aminobutyrate (GABA) as a potential signal in the Gac/Rsm pathway was investigated herein. The function and regulation of a gabDT (c01870-c01880) gene cluster in strain CHA0 were described. The gabT gene encoded GABA transaminase (GABAT) and enabled the growth of the bacterium on GABA, whereas the upstream gabD gene (annotated as a gene encoding succinic semialdehyde dehydrogenase) had an unknown function. A gacA mutant exhibited low GABAT activity, leading to the markedly greater intracellular accumulation of GABA than in the wild type. In the gacA mutant, the RsmA and RsmE proteins caused translational gabD repression, with concomitant gabT repression. Due to very low GABAT activity, the gabT mutant accumulated GABA to high levels. This trait promoted a planktonic lifestyle, reduced biofilm formation, and favored root colonization without exhibiting the highly pleiotropic gacA phenotypes. These results suggest an important role of GABA in the Gac/Rsm-regulated niche adaptation of strain CHA0 to plant roots.
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Affiliation(s)
- Kasumi Takeuchi
- Division of Plant and Microbial Sciences, Institute of Agrobiological Sciences, National Agriculture and Food Research Organization, 2-1-2 Kannondai, Tsukuba, Ibaraki 305-8602, Japan
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18
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Secondary Metabolism and Interspecific Competition Affect Accumulation of Spontaneous Mutants in the GacS-GacA Regulatory System in Pseudomonas protegens. mBio 2018; 9:mBio.01845-17. [PMID: 29339425 PMCID: PMC5770548 DOI: 10.1128/mbio.01845-17] [Citation(s) in RCA: 24] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Secondary metabolites are synthesized by many microorganisms and provide a fitness benefit in the presence of competitors and predators. Secondary metabolism also can be costly, as it shunts energy and intermediates from primary metabolism. In Pseudomonas spp., secondary metabolism is controlled by the GacS-GacA global regulatory system. Intriguingly, spontaneous mutations in gacS or gacA (Gac− mutants) are commonly observed in laboratory cultures. Here we investigated the role of secondary metabolism in the accumulation of Gac− mutants in Pseudomonas protegens strain Pf-5. Our results showed that secondary metabolism, specifically biosynthesis of the antimicrobial compound pyoluteorin, contributes significantly to the accumulation of Gac− mutants. Pyoluteorin biosynthesis, which poses a metabolic burden on the producer cells, but not pyoluteorin itself, leads to the accumulation of the spontaneous mutants. Interspecific competition also influenced the accumulation of the Gac− mutants: a reduced proportion of Gac− mutants accumulated when P. protegens Pf-5 was cocultured with Bacillus subtilis than in pure cultures of strain Pf-5. Overall, our study associated a fitness trade-off with secondary metabolism, with metabolic costs versus competitive benefits of production influencing the evolution of P. protegens, assessed by the accumulation of Gac− mutants. Many microorganisms produce antibiotics, which contribute to ecologic fitness in natural environments where microbes constantly compete for resources with other organisms. However, biosynthesis of antibiotics is costly due to the metabolic burdens of the antibiotic-producing microorganism. Our results provide an example of the fitness trade-off associated with antibiotic production. Under noncompetitive conditions, antibiotic biosynthesis led to accumulation of spontaneous mutants lacking a master regulator of antibiotic production. However, relatively few of these spontaneous mutants accumulated when a competitor was present. Results from this work provide information on the evolution of antibiotic biosynthesis and provide a framework for their discovery and regulation.
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19
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Lopes LD, Davis EW, Pereira E Silva MDC, Weisberg AJ, Bresciani L, Chang JH, Loper JE, Andreote FD. Tropical soils are a reservoir for fluorescent Pseudomonas spp. biodiversity. Environ Microbiol 2017; 20:62-74. [PMID: 29027341 DOI: 10.1111/1462-2920.13957] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2017] [Revised: 10/07/2017] [Accepted: 10/08/2017] [Indexed: 11/30/2022]
Abstract
Fluorescent Pseudomonas spp. are widely studied for their beneficial activities to plants. To explore the genetic diversity of Pseudomonas spp. in tropical regions, we collected 76 isolates from a Brazilian soil. Genomes were sequenced and compared to known strains, mostly collected from temperate regions. Phylogenetic analyses classified the isolates in the P. fluorescens (57) and P. putida (19) groups. Among the isolates in the P. fluorescens group, most (37) were classified in the P. koreensis subgroup and two in the P. jessenii subgroup. The remaining 18 isolates fell into two phylogenetic subclades distinct from currently recognized P. fluorescens subgroups, and probably represent new subgroups. Consistent with their phylogenetic distance from described subgroups, the genome sequences of strains in these subclades are asyntenous to the genome sequences of members of their neighbour subgroups. The tropical isolates have several functional genes also present in known fluorescent Pseudomonas spp. strains. However, members of the new subclades share exclusive genes not detected in other subgroups, pointing to the potential for novel functions. Additionally, we identified 12 potential new species among the 76 isolates from the tropical soil. The unexplored diversity found in the tropical soil is possibly related to biogeographical patterns.
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Affiliation(s)
- Lucas Dantas Lopes
- Department of Soil Science, "Luiz de Queiroz" College of Agriculture, University of São Paulo, Piracicaba, SP, Brazil.,Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA
| | - Edward W Davis
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA.,Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR 97331, USA
| | - Michele de C Pereira E Silva
- Department of Soil Science, "Luiz de Queiroz" College of Agriculture, University of São Paulo, Piracicaba, SP, Brazil
| | - Alexandra J Weisberg
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA
| | - Luana Bresciani
- Department of Soil Science, "Luiz de Queiroz" College of Agriculture, University of São Paulo, Piracicaba, SP, Brazil
| | - Jeff H Chang
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA.,Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR 97331, USA
| | - Joyce E Loper
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR 97331, USA.,Molecular and Cellular Biology Program, Oregon State University, Corvallis, OR 97331, USA
| | - Fernando D Andreote
- Department of Soil Science, "Luiz de Queiroz" College of Agriculture, University of São Paulo, Piracicaba, SP, Brazil
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20
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Lv Y, Niu Z, Chen Y, Hu Y. Bacterial effects and interfacial inactivation mechanism of nZVI/Pd on Pseudomonas putida strain. WATER RESEARCH 2017; 115:297-308. [PMID: 28285239 DOI: 10.1016/j.watres.2017.03.012] [Citation(s) in RCA: 51] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/19/2016] [Revised: 02/14/2017] [Accepted: 03/05/2017] [Indexed: 06/06/2023]
Abstract
With the introduction of nano zero valent iron (nZVI) technology into our environment, its potential environmental risk to environmental microorganisms has attracted considerable attention. In this study, Pseudomonas putida was chosen as a typical strain to study the bacterial toxicity of nZVI/Pd. The CFU assay results indicated that nZVI/Pd was toxic to P. putida cells but the toxicity decreased with an increase in DO. The experiments isolated by dialysis bag and flow cytometry analysis suggested that both membrane disruption caused by direct contact and oxidative stress were the main bactericidal mechanisms under the aerobic condition, while membrane disruption resulting from direct contact was the primary bactericidal mechanism in the anaerobic system. Furthermore, according to TEM, SEM, EDS, XRD, FTIR and XPS, it was indicated that in the aerobic system, the reactive oxygen species (ROS) generated by nZVI/Pd could oxidize the amide and hydroxyl groups into carboxyl groups, resulting in a decline in peptides and increase in polysaccharides. In addition, the ROS also accumulated inside the cell and caused cell inactivation via oxidative stress. In the anaerobic system, the adhered nZVI/Pd particles would attack the functional groups such as carboxyl, ester and amide, leading to the decline in proteins and polysaccharides and subsequent damage of the membrane. The findings provide a significant guide for the application of nano-bio combined technology.
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Affiliation(s)
- Yuancai Lv
- State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Science, South China University of Technology, Guangzhou, 510640, China; College of Environment & Resources, Fuzhou University, Fuzhou, 350116, China.
| | - Zhuyu Niu
- Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, College of Environment and Energy, South China University of Technology, Guangzhou, 510006, China
| | - Yuancai Chen
- State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Science, South China University of Technology, Guangzhou, 510640, China; Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, College of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.
| | - Yongyou Hu
- State Key Laboratory of Pulp and Paper Engineering, College of Light Industry and Food Science, South China University of Technology, Guangzhou, 510640, China; Ministry of Education Key Laboratory of Pollution Control and Ecological Remediation for Industrial Agglomeration Area, College of Environment and Energy, South China University of Technology, Guangzhou, 510006, China.
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21
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Yan Q, Philmus B, Chang JH, Loper JE. Novel mechanism of metabolic co-regulation coordinates the biosynthesis of secondary metabolites in Pseudomonas protegens. eLife 2017; 6. [PMID: 28262092 PMCID: PMC5395296 DOI: 10.7554/elife.22835] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2016] [Accepted: 02/16/2017] [Indexed: 12/02/2022] Open
Abstract
Metabolic co-regulation between biosynthetic pathways for secondary metabolites is common in microbes and can play an important role in microbial interactions. Here, we describe a novel mechanism of metabolic co-regulation in which an intermediate in one pathway is converted into signals that activate a second pathway. Our study focused on the co-regulation of 2,4-diacetylphloroglucinol (DAPG) and pyoluteorin, two antimicrobial metabolites produced by the soil bacterium Pseudomonas protegens. We show that an intermediate in DAPG biosynthesis, phloroglucinol, is transformed by a halogenase encoded in the pyoluteorin gene cluster into mono- and di-chlorinated phloroglucinols. The chlorinated phloroglucinols function as intra- and inter-cellular signals that induce the expression of pyoluteorin biosynthetic genes, pyoluteorin production, and pyoluteorin-mediated inhibition of the plant-pathogenic bacterium Erwinia amylovora. This metabolic co-regulation provides a strategy for P. protegens to optimize the deployment of secondary metabolites with distinct roles in cooperative and competitive microbial interactions. DOI:http://dx.doi.org/10.7554/eLife.22835.001 Bacteria live almost everywhere on Earth and often compete with one another for limited resources, like space or nutrients. Certain bacteria produce molecules that are toxic to other microorganisms to give themselves a competitive advantage. These toxic molecules are more commonly referred as antibiotics, and are perhaps best known for their importance in medicine. Yet, antibiotics benefit the bacteria that produce them in other ways too. Some bacteria, for example, use antibiotics as chemical signals to communicate with one another and coordinate their activities. Some bacteria produce many antibiotics with different toxic and signaling activities. These bacteria often coordinate the production of different antibiotics such that the production of one antibiotic shuts down the production of another. This kind of coordination would allow the bacterium to focus its energy on producing only the antibiotic that gives it a competitive advantage at that time. Yet, in most cases, it was not known how the bacterial cell coordinates the production of two different antibiotics. Pseudomonas protegens is a species of bacteria that lives in soil, and produces many antibiotics that are toxic to other bacteria or fungi. The antibiotics are made via distinct pathways of chemical reactions that are catalyzed by different enzymes. However, the production of two antibiotics, called 2,4-diacetylphloroglucinol and pyoluteorin, is tightly coordinated in some strains of P. protegens. Now, Yan et al. have discovered how P. protegens coordinates the production of these two antibiotics. It turns out that the bacterium produces an enzyme that adds chlorine atoms onto one of the intermediate building blocks used to make 2,4-diacetylphloroglucinol. These “chlorinated derivatives” then activate the genes required to make the second antibiotic, pyoluteorin. The derivatives also signal to other P. protegens cells and trigger them to produce pyoluteorin too. Lastly, Yan et al. confirmed that pyoluteorin could inhibit the growth of another species of bacteria called Erwinia amylovora. These new findings highlight an important role played by chemicals that might have previously been considered as merely stepping stones in other biochemical reactions. An important challenge for the future will be to evaluate if other microbes use chemical intermediates in similar ways. Understanding the natural role of more antibiotics and their intermediates should help us to more wisely use existing antibiotics, and might eventually lead to new treatments for infections in humans and other animals. DOI:http://dx.doi.org/10.7554/eLife.22835.002
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Affiliation(s)
- Qing Yan
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, United States
| | - Benjamin Philmus
- Department of Pharmaceutical Sciences, Oregon State University, Corvallis, United States
| | - Jeff H Chang
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, United States
| | - Joyce E Loper
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, United States.,US Department of Agriculture, Agricultural Research Service, Horticultural Crops Research Laboratory, Corvallis, United States
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22
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Flury P, Vesga P, Péchy-Tarr M, Aellen N, Dennert F, Hofer N, Kupferschmied KP, Kupferschmied P, Metla Z, Ma Z, Siegfried S, de Weert S, Bloemberg G, Höfte M, Keel CJ, Maurhofer M. Antimicrobial and Insecticidal: Cyclic Lipopeptides and Hydrogen Cyanide Produced by Plant-Beneficial Pseudomonas Strains CHA0, CMR12a, and PCL1391 Contribute to Insect Killing. Front Microbiol 2017; 8:100. [PMID: 28217113 PMCID: PMC5289993 DOI: 10.3389/fmicb.2017.00100] [Citation(s) in RCA: 59] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/25/2016] [Accepted: 01/13/2017] [Indexed: 01/30/2023] Open
Abstract
Particular groups of plant-beneficial fluorescent pseudomonads are not only root colonizers that provide plant disease suppression, but in addition are able to infect and kill insect larvae. The mechanisms by which the bacteria manage to infest this alternative host, to overcome its immune system, and to ultimately kill the insect are still largely unknown. However, the investigation of the few virulence factors discovered so far, points to a highly multifactorial nature of insecticidal activity. Antimicrobial compounds produced by fluorescent pseudomonads are effective weapons against a vast diversity of organisms such as fungi, oomycetes, nematodes, and protozoa. Here, we investigated whether these compounds also contribute to insecticidal activity. We tested mutants of the highly insecticidal strains Pseudomonas protegens CHA0, Pseudomonas chlororaphis PCL1391, and Pseudomonas sp. CMR12a, defective for individual or multiple antimicrobial compounds, for injectable and oral activity against lepidopteran insect larvae. Moreover, we studied expression of biosynthesis genes for these antimicrobial compounds for the first time in insects. Our survey revealed that hydrogen cyanide and different types of cyclic lipopeptides contribute to insecticidal activity. Hydrogen cyanide was essential to full virulence of CHA0 and PCL1391 directly injected into the hemolymph. The cyclic lipopeptide orfamide produced by CHA0 and CMR12a was mainly important in oral infections. Mutants of CMR12a and PCL1391 impaired in the production of the cyclic lipopeptides sessilin and clp1391, respectively, showed reduced virulence in injection and feeding experiments. Although virulence of mutants lacking one or several of the other antimicrobial compounds, i.e., 2,4-diacetylphloroglucinol, phenazines, pyrrolnitrin, or pyoluteorin, was not reduced, these metabolites might still play a role in an insect background since all investigated biosynthetic genes for antimicrobial compounds of strain CHA0 were expressed at some point during insect infection. In summary, our study identified new factors contributing to insecticidal activity and extends the diverse functions of antimicrobial compounds produced by fluorescent pseudomonads from the plant environment to the insect host.
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Affiliation(s)
- Pascale Flury
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürich, Switzerland
| | - Pilar Vesga
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürich, Switzerland
| | - Maria Péchy-Tarr
- Department of Fundamental Microbiology, University of LausanneLausanne, Switzerland
| | - Nora Aellen
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürich, Switzerland
| | - Francesca Dennert
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürich, Switzerland
| | - Nicolas Hofer
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürich, Switzerland
| | | | - Peter Kupferschmied
- Department of Fundamental Microbiology, University of LausanneLausanne, Switzerland
| | - Zane Metla
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürich, Switzerland
- Laboratory of Experimental Entomology, Institute of Biology, University of LatviaRiga, Latvia
| | - Zongwang Ma
- Laboratory of Phytopathology, Faculty of Bioscience Engineering, Ghent UniversityGhent, Belgium
| | - Sandra Siegfried
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürich, Switzerland
| | - Sandra de Weert
- Microbial Biotechnology and Health, Institute of Biology Leiden, Leiden UniversityLeiden, Netherlands
| | - Guido Bloemberg
- Microbial Biotechnology and Health, Institute of Biology Leiden, Leiden UniversityLeiden, Netherlands
| | - Monica Höfte
- Laboratory of Phytopathology, Faculty of Bioscience Engineering, Ghent UniversityGhent, Belgium
| | - Christoph J. Keel
- Department of Fundamental Microbiology, University of LausanneLausanne, Switzerland
| | - Monika Maurhofer
- Plant Pathology, Institute of Integrative Biology, ETH ZürichZürich, Switzerland
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23
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Lefevre E, Bossa N, Wiesner MR, Gunsch CK. A review of the environmental implications of in situ remediation by nanoscale zero valent iron (nZVI): Behavior, transport and impacts on microbial communities. THE SCIENCE OF THE TOTAL ENVIRONMENT 2016; 565:889-901. [PMID: 26897610 PMCID: PMC5217753 DOI: 10.1016/j.scitotenv.2016.02.003] [Citation(s) in RCA: 173] [Impact Index Per Article: 21.6] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/19/2015] [Revised: 01/20/2016] [Accepted: 02/01/2016] [Indexed: 05/04/2023]
Abstract
The increasing use of strategies incorporating nanoscale zero valent iron (nZVI) for soil and groundwater in situ remediation is raising some concerns regarding the potential adverse effects nZVI could have on indigenous microbial communities and ecosystem functioning. This review provides an overview of the current literature pertaining to the impacts of nZVI applications on microbial communities. Toxicity studies suggest that cell membrane disruption and oxidative stress through the generation of Fe(2+) and reactive oxygen species by nZVI are the main mechanisms contributing to nZVI cytotoxicity. In addition, nZVI has been shown to substantially alter the taxonomic and functional composition of indigenous microbial communities. However, because the physico-chemical conditions encountered in situ highly modulate nZVI toxicity, a better understanding of the environmental factors affecting nZVI toxicity and transport in the environment is of primary importance in evaluating the ecological consequences that could result from a more extensive use of nZVI.
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Affiliation(s)
- Emilie Lefevre
- Department of Civil and Environmental Engineering, Duke University, Durham, NC, USA
| | - Nathan Bossa
- Department of Civil and Environmental Engineering, Duke University, Durham, NC, USA
| | - Mark R Wiesner
- Department of Civil and Environmental Engineering, Duke University, Durham, NC, USA
| | - Claudia K Gunsch
- Department of Civil and Environmental Engineering, Duke University, Durham, NC, USA.
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24
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Loper JE, Henkels MD, Rangel LI, Olcott MH, Walker FL, Bond KL, Kidarsa TA, Hesse CN, Sneh B, Stockwell VO, Taylor BJ. Rhizoxin analogs, orfamide A and chitinase production contribute to the toxicity of Pseudomonas protegens strain Pf-5 to Drosophila melanogaster. Environ Microbiol 2016; 18:3509-3521. [PMID: 27130686 DOI: 10.1111/1462-2920.13369] [Citation(s) in RCA: 43] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/23/2016] [Accepted: 04/13/2016] [Indexed: 11/28/2022]
Abstract
Pseudomonas protegens strain Pf-5 is a soil bacterium that was first described for its capacity to suppress plant diseases and has since been shown to be lethal to certain insects. Among these is the common fruit fly Drosophila melanogaster, a well-established model organism for studies evaluating the molecular and cellular basis of the immune response to bacterial challenge. Pf-5 produces the insect toxin FitD, but a ΔfitD mutant of Pf-5 retained full toxicity against D. melanogaster in a noninvasive feeding assay, indicating that FitD is not a major determinant of Pf-5's oral toxicity against this insect. Pf-5 also produces a broad spectrum of exoenzymes and natural products with antibiotic activity, whereas a mutant with a deletion in the global regulatory gene gacA produces none of these exoproducts and also lacks toxicity to D. melanogaster. In this study, we made use of a panel of Pf-5 mutants having single or multiple mutations in the biosynthetic gene clusters for seven natural products and two exoenzymes that are produced by the bacterium under the control of gacA. Our results demonstrate that the production of rhizoxin analogs, orfamide A, and chitinase are required for full oral toxicity of Pf-5 against D. melanogaster, with rhizoxins being the primary determinant.
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Affiliation(s)
- Joyce E Loper
- Agricultural Research Service, US Department of Agriculture, 3420 N.W. Orchard Ave., Corvallis, OR, 97330, USA. .,Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, 97331, USA.
| | - Marcella D Henkels
- Agricultural Research Service, US Department of Agriculture, 3420 N.W. Orchard Ave., Corvallis, OR, 97330, USA.,Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, 97331, USA
| | - Lorena I Rangel
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, 97331, USA
| | - Marika H Olcott
- Department of Integrative Biology, Oregon State University, Corvallis, OR, 97331, USA
| | - Francesca L Walker
- Department of Integrative Biology, Oregon State University, Corvallis, OR, 97331, USA
| | - Kise L Bond
- Department of Integrative Biology, Oregon State University, Corvallis, OR, 97331, USA
| | - Teresa A Kidarsa
- Agricultural Research Service, US Department of Agriculture, 3420 N.W. Orchard Ave., Corvallis, OR, 97330, USA.,Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, 97331, USA
| | - Cedar N Hesse
- Agricultural Research Service, US Department of Agriculture, 3420 N.W. Orchard Ave., Corvallis, OR, 97330, USA
| | - Baruch Sneh
- Department of Molecular Biology and Ecology of Plants, The George S. Wise Faculty of Life Sciences, Tel Aviv University, Tel Aviv, Israel
| | - Virginia O Stockwell
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, OR, 97331, USA
| | - Barbara J Taylor
- Department of Integrative Biology, Oregon State University, Corvallis, OR, 97331, USA
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25
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Song C, Kidarsa TA, van de Mortel JE, Loper JE, Raaijmakers JM. Living on the edge: emergence of spontaneous gac mutations in Pseudomonas protegens during swarming motility. Environ Microbiol 2016; 18:3453-3465. [PMID: 26945503 DOI: 10.1111/1462-2920.13288] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2015] [Accepted: 03/02/2016] [Indexed: 11/28/2022]
Abstract
Swarming motility is a flagella-driven multicellular behaviour that allows bacteria to colonize new niches and escape competition. Here, we investigated the evolution of specific mutations in the GacS/GacA two-component regulatory system in swarming colonies of Pseudomonas protegens Pf-5. Experimental evolution assays showed that repeated rounds of swarming by wildtype Pf-5 drives the accumulation of gacS/gacA spontaneous mutants on the swarming edge. These mutants cannot swarm on their own because they lack production of the biosurfactant orfamide A, but they do co-swarm with orfamide-producing wildtype Pf-5. These co-swarming assays further demonstrated that ΔgacA mutant cells indeed predominate on the edge and that initial ΔgacA:wildtype Pf-5 ratios of at least 2:1 lead to a collapse of the swarming colony. Subsequent whole-genome transcriptome analyses revealed that genes associated with motility, resource acquisition, chemotaxis and efflux were significantly upregulated in ΔgacA mutant on swarming medium. Moreover, transmission electron microscopy showed that ΔgacA mutant cells were longer and more flagellated than wildtype cells, which may explain their predominance on the swarming edge. We postulate that adaptive evolution through point mutations is a common feature of range-expanding microbial populations and that the putative fitness benefits of these mutations during dispersal of bacteria into new territories are frequency-dependent.
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Affiliation(s)
- Chunxu Song
- Department of Microbial Ecology, Netherlands Institute of Ecology, Droevendaalsesteeg 10, 6708, PB, Wageningen, The Netherlands.,Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708, PB, Wageningen, The Netherlands
| | - Teresa A Kidarsa
- Agricultural Research Service, US Department of Agriculture, Corvallis, OR, 97330, USA
| | - Judith E van de Mortel
- Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708, PB, Wageningen, The Netherlands
| | - Joyce E Loper
- Agricultural Research Service, US Department of Agriculture, Corvallis, OR, 97330, USA
| | - Jos M Raaijmakers
- Department of Microbial Ecology, Netherlands Institute of Ecology, Droevendaalsesteeg 10, 6708, PB, Wageningen, The Netherlands. .,Microbial Biotechnology Department, Institute of Biology (IBL), Leiden University, Leiden, The Netherlands.
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26
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Quecine MC, Kidarsa TA, Goebel NC, Shaffer BT, Henkels MD, Zabriskie TM, Loper JE. An Interspecies Signaling System Mediated by Fusaric Acid Has Parallel Effects on Antifungal Metabolite Production by Pseudomonas protegens Strain Pf-5 and Antibiosis of Fusarium spp. Appl Environ Microbiol 2015; 82:1372-1382. [PMID: 26655755 PMCID: PMC4771327 DOI: 10.1128/aem.02574-15] [Citation(s) in RCA: 27] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/07/2015] [Accepted: 12/03/2015] [Indexed: 01/27/2023] Open
Abstract
Pseudomonas protegens strain Pf-5 is a rhizosphere bacterium that suppresses soilborne plant diseases and produces at least seven different secondary metabolites with antifungal properties. We derived mutants of Pf-5 with single and multiple mutations in biosynthesis genes for seven antifungal metabolites: 2,4-diacetylphoroglucinol (DAPG), pyrrolnitrin, pyoluteorin, hydrogen cyanide, rhizoxin, orfamide A, and toxoflavin. These mutants were tested for inhibition of the pathogens Fusarium verticillioides and Fusarium oxysporum f. sp. pisi. Rhizoxin, pyrrolnitrin, and DAPG were found to be primarily responsible for fungal antagonism by Pf-5. Previously, other workers showed that the mycotoxin fusaric acid, which is produced by many Fusarium species, including F. verticillioides, inhibited the production of DAPG by Pseudomonas spp. In this study, amendment of culture media with fusaric acid decreased DAPG production, increased pyoluteorin production, and had no consistent influence on pyrrolnitrin or orfamide A production by Pf-5. Fusaric acid also altered the transcription of biosynthetic genes, indicating that the mycotoxin influenced antibiotic production by Pf-5 at the transcriptional level. Addition of fusaric acid to the culture medium reduced antibiosis of F. verticillioides by Pf-5 and derivative strains that produce DAPG but had no effect on antibiosis by Pf-5 derivatives that suppressed F. verticillioides due to pyrrolnitrin or rhizoxin production. Our results demonstrated the importance of three compounds, rhizoxin, pyrrolnitrin, and DAPG, in suppression of Fusarium spp. by Pf-5 and confirmed that an interspecies signaling system mediated by fusaric acid had parallel effects on antifungal metabolite production and antibiosis by the bacterial biological control organism.
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Affiliation(s)
- Maria Carolina Quecine
- Department of Genetics, College of Agriculture Luiz de Queiroz, ESALQ, University of São Paulo, Piracicaba, São Paulo, Brazil
| | - Teresa A Kidarsa
- Agricultural Research Service, U.S. Department of Agriculture, Corvallis, Oregon, USA
| | - Neal C Goebel
- Department of Pharmaceutical Sciences, Oregon State University, Corvallis, Oregon, USA
| | - Brenda T Shaffer
- Agricultural Research Service, U.S. Department of Agriculture, Corvallis, Oregon, USA
| | - Marcella D Henkels
- Agricultural Research Service, U.S. Department of Agriculture, Corvallis, Oregon, USA
| | - T Mark Zabriskie
- Department of Pharmaceutical Sciences, Oregon State University, Corvallis, Oregon, USA
| | - Joyce E Loper
- Agricultural Research Service, U.S. Department of Agriculture, Corvallis, Oregon, USA
- Department of Botany and Plant Pathology, Oregon State University, Corvallis, Oregon, USA
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27
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Clifford JC, Buchanan A, Vining O, Kidarsa TA, Chang JH, McPhail KL, Loper JE. Phloroglucinol functions as an intracellular and intercellular chemical messenger influencing gene expression in Pseudomonas protegens. Environ Microbiol 2015; 18:3296-3308. [PMID: 26337778 DOI: 10.1111/1462-2920.13043] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Revised: 07/24/2015] [Accepted: 08/22/2015] [Indexed: 12/13/2022]
Abstract
Bacteria can be both highly communicative and highly competitive in natural habitats and antibiotics are thought to play a role in both of these processes. The soil bacterium Pseudomonas protegens Pf-5 produces a spectrum of antibiotics, two of which, pyoluteorin and 2,4-diacetylphloroglucinol (DAPG), function in intracellular and intercellular communication, both as autoinducers of their own production. Here, we demonstrate that phloroglucinol, an intermediate in DAPG biosynthesis, can serve as an intercellular signal influencing the expression of pyoluteorin biosynthesis genes, the production of pyoluteorin, and inhibition of Pythium ultimum, a phytopathogenic oomycete sensitive to pyoluteorin. Through analysis of RNAseq data sets, we show that phloroglucinol had broad effects on the transcriptome of Pf-5, significantly altering the transcription of more than two hundred genes. The effects of nanomolar versus micromolar concentrations of phloroglucinol differed both quantitatively and qualitatively, influencing the expression of distinct sets of genes or having opposite effects on transcript abundance of certain genes. Therefore, our results support the concept of hormesis, a phenomenon associated with signalling molecules that elicit distinct responses at different concentrations. Phloroglucinol is the first example of an intermediate of antibiotic biosynthesis that functions as a chemical messenger influencing gene expression in P. protegens.
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Affiliation(s)
- Jennifer C Clifford
- US Department of Agriculture, Agricultural Research Service, Horticultural Crops Research Laboratory, Corvallis, OR, USA
| | - Alex Buchanan
- Department of Botany and Plant Pathology and Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR, USA
| | - Oliver Vining
- College of Pharmacy, Oregon State University, Corvallis, OR, USA
| | - Teresa A Kidarsa
- US Department of Agriculture, Agricultural Research Service, Horticultural Crops Research Laboratory, Corvallis, OR, USA
| | - Jeff H Chang
- Department of Botany and Plant Pathology and Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR, USA
| | - Kerry L McPhail
- College of Pharmacy, Oregon State University, Corvallis, OR, USA
| | - Joyce E Loper
- US Department of Agriculture, Agricultural Research Service, Horticultural Crops Research Laboratory, Corvallis, OR, USA. .,Department of Botany and Plant Pathology and Center for Genome Research and Biocomputing, Oregon State University, Corvallis, OR, USA.
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28
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Herbst FA, Danielsen HN, Wimmer R, Nielsen PH, Dueholm MS. Label-free quantification reveals major proteomic changes in Pseudomonas putida F1 during the exponential growth phase. Proteomics 2015; 15:3244-52. [PMID: 26122999 DOI: 10.1002/pmic.201400482] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/16/2014] [Revised: 04/30/2015] [Accepted: 06/26/2015] [Indexed: 01/12/2023]
Abstract
The physiological adaptation to stationary growth by Pseudomonas putida F1, a model organism for the degradation of aromatic compounds, was investigated by proteome-wide label-free quantification.The data unveiled that entrance to the stationary phase did not involve an abrupt switch within the P. putida F1 proteome, but rather an ongoing adaptation that started already during the mid-exponential growth phase. The proteomic adaptations involved a clear increase in amino acid degradation capabilities and a loss of transcriptional as well as translational capacity. The final entrance to the stationary phase was accompanied by increased oxidative stress protection, although the stress and stationary sigma factor RpoS increased in abundance already during mid-exponential growth. The results show that it is important to consider significant sample variations when exponentially growing cultures are studied alone or compared across proteomic or transcriptomic literature. All MS data have been deposited in the ProteomeXchange with identifier PXD001219 (http://proteomecentral.proteomexchange.org/dataset/PXD001219).
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Affiliation(s)
- Florian-Alexander Herbst
- Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Heidi Nolsøe Danielsen
- Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Reinhard Wimmer
- Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Per Halkjaer Nielsen
- Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
| | - Morten Simonsen Dueholm
- Center for Microbial Communities, Department of Chemistry and Bioscience, Aalborg University, Aalborg, Denmark
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29
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Philmus B, Shaffer BT, Kidarsa TA, Yan Q, Raaijmakers JM, Begley TP, Loper JE. Investigations into the Biosynthesis, Regulation, and Self-Resistance of Toxoflavin in Pseudomonas protegens Pf-5. Chembiochem 2015; 16:1782-90. [PMID: 26077901 DOI: 10.1002/cbic.201500247] [Citation(s) in RCA: 38] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2015] [Indexed: 11/10/2022]
Abstract
Pseudomonas spp. are prolific producers of natural products from many structural classes. Here we show that the soil bacterium Pseudomonas protegens Pf-5 is capable of producing trace levels of the triazine natural product toxoflavin (1) under microaerobic conditions. We evaluated toxoflavin production by derivatives of Pf-5 with deletions in specific biosynthesis genes, which led us to propose a revised biosynthetic pathway for toxoflavin that shares the first two steps with riboflavin biosynthesis. We also report that toxM, which is not present in the well-characterized cluster of Burkholderia glumae, encodes a monooxygenase that degrades toxoflavin. The toxoflavin degradation product of ToxM is identical to that of TflA, the toxoflavin lyase from Paenibacillus polymyxa. Toxoflavin production by P. protegens causes inhibition of several plant-pathogenic bacteria, and introduction of toxM into the toxoflavin-sensitive strain Pseudomonas syringae DC3000 results in resistance to toxoflavin.
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Affiliation(s)
- Benjamin Philmus
- College of Pharmacy, Oregon State University, 203 Pharmacy Building, Corvallis, OR 97331 (USA).
| | - Brenda T Shaffer
- Agricultural Research Service, US Department of Agriculture, 3420 N.W. Orchard Avenue, Corvallis, OR 97330 (USA)
| | - Teresa A Kidarsa
- Agricultural Research Service, US Department of Agriculture, 3420 N.W. Orchard Avenue, Corvallis, OR 97330 (USA)
| | - Qing Yan
- Department of Botany and Plant Pathology, Oregon State University, 2082 Cordley Hall, Corvallis, OR 97331 (USA)
| | - Jos M Raaijmakers
- Department of Microbial Ecology, Netherlands Institute of Ecology, Droevendaalsesteeg 10, 6708 PB Wageningen (The Netherlands).,Institute of Biology, Leiden University, Sylviusweg 72, 2333 BE Leiden (The Netherlands)
| | - Tadhg P Begley
- Department of Chemistry, Texas A&M University, College Station, TX 77843 (USA)
| | - Joyce E Loper
- Agricultural Research Service, US Department of Agriculture, 3420 N.W. Orchard Avenue, Corvallis, OR 97330 (USA). .,Department of Botany and Plant Pathology, Oregon State University, 2082 Cordley Hall, Corvallis, OR 97331 (USA).
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30
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Transcriptional analysis of the global regulatory networks active in Pseudomonas syringae during leaf colonization. mBio 2014; 5:e01683-14. [PMID: 25182327 PMCID: PMC4173789 DOI: 10.1128/mbio.01683-14] [Citation(s) in RCA: 47] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
The plant pathogen Pseudomonas syringae pv. syringae B728a grows and survives on leaf surfaces and in the leaf apoplast of its host, bean (Phaseolus vulgaris). To understand the contribution of distinct regulators to B728a fitness and pathogenicity, we performed a transcriptome analysis of strain B728a and nine regulatory mutants recovered from the surfaces and interior of leaves and exposed to environmental stresses in culture. The quorum-sensing regulators AhlR and AefR influenced few genes in planta or in vitro. In contrast, GacS and a downstream regulator, SalA, formed a large regulatory network that included a branch that regulated diverse traits and was independent of plant-specific environmental signals and a plant signal-dependent branch that positively regulated secondary metabolite genes and negatively regulated the type III secretion system. SalA functioned as a central regulator of iron status based on its reciprocal regulation of pyoverdine and achromobactin genes and also sulfur uptake, suggesting a role in the iron-sulfur balance. RetS functioned almost exclusively to repress secondary metabolite genes when the cells were not on leaves. Among the sigma factors examined, AlgU influenced many more genes than RpoS, and most AlgU-regulated genes depended on RpoN. RpoN differentially impacted many AlgU- and GacS-activated genes in cells recovered from apoplastic versus epiphytic sites, suggesting differences in environmental signals or bacterial stress status in these two habitats. Collectively, our findings illustrate a central role for GacS, SalA, RpoN, and AlgU in global regulation in B728a in planta and a high level of plasticity in these regulators’ responses to distinct environmental signals. Leaves harbor abundant microorganisms, all of which must withstand challenges such as active plant defenses and a highly dynamic environment. Some of these microbes can influence plant health. Despite knowledge of individual regulators that affect the fitness or pathogenicity of foliar pathogens, our understanding of the relative importance of various global regulators to leaf colonization is limited. Pseudomonas syringae strain B728a is a plant pathogen and a good colonist of both the surfaces and interior of leaves. This study used global transcript profiles of strain B728a to investigate the complex regulatory network of putative quorum-sensing regulators, two-component regulators, and sigma factors in cells colonizing the leaf surface and leaf interior under stressful in vitro conditions. The results highlighted the value of evaluating these networks in planta due to the impact of leaf-specific environmental signals and suggested signal differences that may enable cells to differentiate surface versus interior leaf habitats.
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Henkels MD, Kidarsa TA, Shaffer BT, Goebel NC, Burlinson P, Mavrodi DV, Bentley MA, Rangel LI, Davis EW, Thomashow LS, Zabriskie TM, Preston GM, Loper JE. Pseudomonas protegens Pf-5 causes discoloration and pitting of mushroom caps due to the production of antifungal metabolites. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2014; 27:733-746. [PMID: 24742073 DOI: 10.1094/mpmi-10-13-0311-r] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/03/2023]
Abstract
Bacteria in the diverse Pseudomonas fluorescens group include rhizosphere inhabitants known for their antifungal metabolite production and biological control of plant disease, such as Pseudomonas protegens Pf-5, and mushroom pathogens, such as Pseudomonas tolaasii. Here, we report that strain Pf-5 causes brown, sunken lesions on peeled caps of the button mushroom (Agaricus bisporus) that resemble brown blotch symptoms caused by P. tolaasii. Strain Pf-5 produces six known antifungal metabolites under the control of the GacS/GacA signal transduction system. A gacA mutant produces none of these metabolites and did not cause lesions on mushroom caps. Mutants deficient in the biosynthesis of the antifungal metabolites 2,4-diacetylphloroglucinol and pyoluteorin caused less-severe symptoms than wild-type Pf-5 on peeled mushroom caps, whereas mutants deficient in the production of lipopeptide orfamide A caused similar symptoms to wild-type Pf-5. Purified pyoluteorin and 2,4-diacetylphloroglucinol mimicked the symptoms caused by Pf-5. Both compounds were isolated from mushroom tissue inoculated with Pf-5, providing direct evidence for their in situ production by the bacterium. Although the lipopeptide tolaasin is responsible for brown blotch of mushroom caused by P. tolaasii, P. protegens Pf-5 caused brown blotch-like symptoms on peeled mushroom caps through a lipopeptide-independent mechanism involving the production of 2,4-diacetylphloroglucinol and pyoluteorin.
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Roles of cyclic Di-GMP and the Gac system in transcriptional control of the genes coding for the Pseudomonas putida adhesins LapA and LapF. J Bacteriol 2014; 196:1484-95. [PMID: 24488315 DOI: 10.1128/jb.01287-13] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
LapA and LapF are large extracellular proteins that play a relevant role in biofilm formation by Pseudomonas putida. Current evidence favors a sequential model in which LapA is first required for the initial adhesion of individual bacteria to a surface, while LapF participates in later stages of biofilm development. In agreement with this model, lapF transcription was previously shown to take place at late times of growth and to respond to the stationary-phase sigma factor RpoS. We have now analyzed the transcription pattern of lapA and other regulatory elements that influence expression of both genes. The lapA promoter shows a transient peak of activation early during growth, with a second increase in stationary phase that is independent of RpoS. The same pattern is observed in biofilms although expression is not uniform in the population. Both lapA and lapF are under the control of the two-component regulatory system GacS/GacA, and their transcription also responds to the intracellular levels of the second messenger cyclic diguanylate (c-di-GMP), although in surprisingly reverse ways. Whereas expression from the lapA promoter increases with high levels of c-di-GMP, the opposite is true for lapF. The transcriptional regulator FleQ is required for the modulation of lapA expression by c-di-GMP but has a minor influence on lapF. This work represents a further step in our understanding of the regulatory interactions controlling biofilm formation in P. putida.
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The global response regulator ExpA controls virulence gene expression through RsmA-mediated and RsmA-independent pathways in Pectobacterium wasabiae SCC3193. Appl Environ Microbiol 2014; 80:1972-84. [PMID: 24441162 DOI: 10.1128/aem.03829-13] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
ExpA (GacA) is a global response regulator that controls the expression of major virulence genes, such as those encoding plant cell wall-degrading enzymes (PCWDEs) in the model soft rot phytopathogen Pectobacterium wasabiae SCC3193. Several studies with pectobacteria as well as related phytopathogenic gammaproteobacteria, such as Dickeya and Pseudomonas, suggest that the control of virulence by ExpA and its homologues is executed partly by modulating the activity of RsmA, an RNA-binding posttranscriptional regulator. To elucidate the extent of the overlap between the ExpA and RsmA regulons in P. wasabiae, we characterized both regulons by microarray analysis. To do this, we compared the transcriptomes of the wild-type strain, an expA mutant, an rsmA mutant, and an expA rsmA double mutant. The microarray data for selected virulence-related genes were confirmed through quantitative reverse transcription (qRT-PCR). Subsequently, assays were performed to link the observed transcriptome differences to changes in bacterial phenotypes such as growth, motility, PCWDE production, and virulence in planta. An extensive overlap between the ExpA and RsmA regulons was observed, suggesting that a substantial portion of ExpA regulation appears to be mediated through RsmA. However, a number of genes involved in the electron transport chain and oligogalacturonide metabolism, among other processes, were identified as being regulated by ExpA independently of RsmA. These results suggest that ExpA may only partially impact fitness and virulence via RsmA.
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Cheng X, de Bruijn I, van der Voort M, Loper JE, Raaijmakers JM. The Gac regulon of Pseudomonas fluorescens SBW25. ENVIRONMENTAL MICROBIOLOGY REPORTS 2013; 5:608-19. [PMID: 23864577 DOI: 10.1111/1758-2229.12061] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/05/2012] [Accepted: 04/01/2013] [Indexed: 05/10/2023]
Abstract
Transcriptome analysis of Pseudomonas fluorescens SBW25 showed that 702 genes were differentially regulated in a gacS::Tn5 mutant, with 300 and 402 genes up- and downregulated respectively. Similar to the Gac regulon of other Pseudomonas species, genes involved in motility, biofilm formation, siderophore biosynthesis and oxidative stress were differentially regulated in the gacS mutant of SBW25. Our analysis also revealed, for the first time, that transcription of 19 rhizosphere-induced genes and of genes involved in type II secretion, (exo)polysaccharide and pectate lyase biosynthesis, twitching motility and an orphan non-ribosomal peptide synthetase (NRPS) were significantly affected in the gacS mutant. Furthermore, the gacS mutant inhibited growth of oomycete, fungal and bacterial pathogens significantly more than wild type SBW25. Since RP-HPLC analysis did not reveal any potential candidate metabolites, we focused on the Gac-regulated orphan NRPS gene cluster that was predicted to encode an eight-amino-acid ornicorrugatin-like peptide. Site-directed mutagenesis indicated that the encoded peptide is not involved in the enhanced antimicrobial activity of the gacS mutant but may function as a siderophore. Collectively, this genome-wide analysis revealed that a mutation in the GacS/A two-component regulatory system causes major transcriptional changes in SBW25 and significantly enhances its antimicrobial activities by yet unknown mechanisms.
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Affiliation(s)
- Xu Cheng
- Laboratory of Phytopathology, Wageningen University, Droevendaalsesteeg 1, 6708 PB, Wageningen, the Netherlands
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