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Santander RD, Monte-Serrano M, Rodríguez-Herva JJ, López-Solanilla E, Rodríguez-Palenzuela P, Biosca EG. Exploring new roles for the rpoS gene in the survival and virulence of the fire blight pathogen Erwinia amylovora. FEMS Microbiol Ecol 2014; 90:895-907. [PMID: 25331301 DOI: 10.1111/1574-6941.12444] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2014] [Revised: 10/13/2014] [Accepted: 10/18/2014] [Indexed: 01/19/2023] Open
Abstract
Erwinia amylovora causes fire blight in economically important plants of the family Rosaceae. This bacterial pathogen spends part of its life cycle coping with starvation and other fluctuating environmental conditions. In many Gram-negative bacteria, starvation and other stress responses are regulated by the sigma factor RpoS. We obtained an E. amylovora rpoS mutant to explore the role of this gene in starvation responses and its potential implication in other processes not yet studied in this pathogen. Results showed that E. amylovora needs rpoS to develop normal starvation survival and viable but nonculturable (VBNC) responses. Furthermore, this gene contributed to stationary phase cross-protection against oxidative, osmotic, and acid stresses and was essential for cross-protection against heat shock, but nonessential against acid shock. RpoS also mediated regulation of motility, exopolysaccharide synthesis, and virulence in immature loquats, but not in pear plantlets, and contributed to E. amylovora survival in nonhost tissues during incompatible interactions. Our results reveal some unique roles for the rpoS gene in E. amylovora and provide new knowledge on the regulation of different processes related to its ecology, including survival in different environments and virulence in immature fruits.
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Affiliation(s)
- Ricardo D Santander
- Departmento de Microbiología y Ecología, Universitat de València, Burjassot, Valencia, Spain; Centro de Biotecnología y Genómica de Plantas (CBGP), Universidad Politécnica de Madrid-Instituto Nacional de Investigación y Tecnología Agraria y Alimentaria, Parque Científico y Tecnológico de la UPM, Madrid, Spain
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Santander RD, Oliver JD, Biosca EG. Cellular, physiological, and molecular adaptive responses of Erwinia amylovora to starvation. FEMS Microbiol Ecol 2014; 88:258-71. [PMID: 24476337 DOI: 10.1111/1574-6941.12290] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 01/02/2014] [Accepted: 01/19/2014] [Indexed: 11/29/2022] Open
Abstract
Erwinia amylovora causes fire blight, a destructive disease of rosaceous plants distributed worldwide. This bacterium is a nonobligate pathogen able to survive outside the host under starvation conditions, allowing its spread by various means such as rainwater. We studied E. amylovora responses to starvation using water microcosms to mimic natural oligotrophy. Initially, survivability under optimal (28 °C) and suboptimal (20 °C) growth temperatures was compared. Starvation induced a loss of culturability much more pronounced at 28 °C than at 20 °C. Natural water microcosms at 20 °C were then used to characterize cellular, physiological, and molecular starvation responses of E. amylovora. Challenged cells developed starvation-survival and viable but nonculturable responses, reduced their size, acquired rounded shapes and developed surface vesicles. Starved cells lost motility in a few days, but a fraction retained flagella. The expression of genes related to starvation, oxidative stress, motility, pathogenicity, and virulence was detected during the entire experimental period with different regulation patterns observed during the first 24 h. Further, starved cells remained as virulent as nonstressed cells. Overall, these results provide new knowledge on the biology of E. amylovora under conditions prevailing in nature, which could contribute to a better understanding of the life cycle of this pathogen.
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Affiliation(s)
- Ricardo D Santander
- Department of Microbiology and Ecology, University of Valencia, Burjassot, Valencia, Spain
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Ramos LS, Lehman BL, Sinn JP, Pfeufer EE, Halbrendt NO, McNellis TW. The fire blight pathogen Erwinia amylovora requires the rpoN gene for pathogenicity in apple. MOLECULAR PLANT PATHOLOGY 2013; 14:838-43. [PMID: 23721085 PMCID: PMC6638816 DOI: 10.1111/mpp.12045] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/24/2023]
Abstract
RpoN is a σ(54) factor regulating essential virulence gene expression in several plant pathogenic bacteria, including Pseudomonas syringae and Pectobacterium carotovorum. In this study, we found that mutation of rpoN in the fire blight pathogen Erwinia amylovora caused a nonpathogenic phenotype. The E. amylovora rpoN Tn5 transposon mutant rpoN1250::Tn5 did not cause fire blight disease symptoms on shoots of mature apple trees. In detached immature apple fruits, the rpoN1250::Tn5 mutant failed to cause fire blight disease symptoms and grew to population levels 12 orders of magnitude lower than the wild-type. In addition, the rpoN1250::Tn5 mutant failed to elicit a hypersensitive response when infiltrated into nonhost tobacco plant leaves, and rpoN1250::Tn5 cells failed to express HrpN protein when grown in hrp (hypersensitive response and pathogenicity)-inducing liquid medium. A plasmid-borne copy of the wild-type rpoN gene complemented all the rpoN1250::Tn5 mutant phenotypes tested. The rpoN1250::Tn5 mutant was prototrophic on minimal solid and liquid media, indicating that the rpoN1250::Tn5 nonpathogenic phenotype was not caused by a defect in basic metabolism or growth. This study provides clear genetic evidence that rpoN is an essential virulence gene of E. amylovora, suggesting that rpoN has the same function in E. amylovora as in P. syringae and Pe. carotovorum.
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Affiliation(s)
- Laura S Ramos
- Department of Plant Pathology & Environmental Microbiology, The Pennsylvania State University, University Park, PA 16802, USA
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Global small RNA chaperone Hfq and regulatory small RNAs are important virulence regulators in Erwinia amylovora. J Bacteriol 2013; 195:1706-17. [PMID: 23378513 DOI: 10.1128/jb.02056-12] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Hfq is a global small RNA (sRNA) chaperone that interacts with Hfq-regulated sRNAs and functions in the posttranscriptional regulation of gene expression. In this work, we identified Hfq to be a virulence regulator in the Gram-negative fire blight pathogen Erwinia amylovora. Deletion of hfq in E. amylovora Ea1189 significantly reduced bacterial virulence in both immature pear fruits and apple shoots. Analysis of virulence determinants in strain Ea1189Δhfq showed that Hfq exerts pleiotropic regulation of amylovoran exopolysaccharide production, biofilm formation, motility, and the type III secretion system (T3SS). Further characterization of biofilm regulation by Hfq demonstrated that Hfq limits bacterial attachment to solid surfaces while promoting biofilm maturation. Characterization of T3SS regulation by Hfq revealed that Hfq positively regulates the translocation and secretion of the major type III effector DspE and negatively controls the secretion of the putative translocator HrpK and the type III effector Eop1. Lastly, 10 Hfq-regulated sRNAs were identified using a computational method, and two of these sRNAs, RprA and RyhA, were found to be required for the full virulence of E. amylovora.
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Smits THM, Jaenicke S, Rezzonico F, Kamber T, Goesmann A, Frey JE, Duffy B. Complete genome sequence of the fire blight pathogen Erwinia pyrifoliae DSM 12163T and comparative genomic insights into plant pathogenicity. BMC Genomics 2010; 11:2. [PMID: 20047678 PMCID: PMC2827408 DOI: 10.1186/1471-2164-11-2] [Citation(s) in RCA: 41] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2009] [Accepted: 01/04/2010] [Indexed: 11/10/2022] Open
Abstract
Background Erwinia pyrifoliae is a newly described necrotrophic pathogen, which causes fire blight on Asian (Nashi) pear and is geographically restricted to Eastern Asia. Relatively little is known about its genetics compared to the closely related main fire blight pathogen E. amylovora. Results The genome of the type strain of E. pyrifoliae strain DSM 12163T, was sequenced using both 454 and Solexa pyrosequencing and annotated. The genome contains a circular chromosome of 4.026 Mb and four small plasmids. Based on their respective role in virulence in E. amylovora or related organisms, we identified several putative virulence factors, including type III and type VI secretion systems and their effectors, flagellar genes, sorbitol metabolism, iron uptake determinants, and quorum-sensing components. A deletion in the rpoS gene covering the most conserved region of the protein was identified which may contribute to the difference in virulence/host-range compared to E. amylovora. Comparative genomics with the pome fruit epiphyte Erwinia tasmaniensis Et1/99 showed that both species are overall highly similar, although specific differences were identified, for example the presence of some phage gene-containing regions and a high number of putative genomic islands containing transposases in the E. pyrifoliae DSM 12163T genome. Conclusions The E. pyrifoliae genome is an important addition to the published genome of E. tasmaniensis and the unfinished genome of E. amylovora providing a foundation for re-sequencing additional strains that may shed light on the evolution of the host-range and virulence/pathogenicity of this important group of plant-associated bacteria.
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Affiliation(s)
- Theo H M Smits
- Swiss National Competence Center for Fire Blight, Division of Plant Protection, Agroscope Changins-Wädenswil ACW, Wädenswil, Switzerland
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Cloning, identification, and characterization of the rpoS-like sigma factor rpoX from Vibrio alginolyticus. J Biomed Biotechnol 2009; 2009:126986. [PMID: 20069110 PMCID: PMC2804039 DOI: 10.1155/2009/126986] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2009] [Revised: 08/05/2009] [Accepted: 09/28/2009] [Indexed: 11/18/2022] Open
Abstract
Vibrio alginolyticus ZJ-51 displays phase variation between opaque/rugose colonies (Op) and translucent/smooth colonies (Tr). These colony variants show great differences in biofilm formation and motility. In this study, a gene encoding for an rpoS-like sigma factor, rpoX, has been cloned and characterized. The absence of rpoX did not affect colony switching rate but did decrease biofilm formation in both the Op and the Tr variants. When challenged with hydrogen peroxide, the DeltarpoX in the Op background showed a slightly higher survival rate compared with the wild type, whereas survival was decreased in the Tr background. Deletion of rpoX in the Tr background resulted in a higher ability to resist ethanol challenges and to survive hyperosmolarity challenges, and in the Op background the opposite phenotype was observed. This indicates that the rpoX gene is involved in biofilm formation and stress response but the effects are controlled by colony phase variation in V. alginolyticus.
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Devescovi G, Bigirimana J, Degrassi G, Cabrio L, LiPuma JJ, Kim J, Hwang I, Venturi V. Involvement of a quorum-sensing-regulated lipase secreted by a clinical isolate of Burkholderia glumae in severe disease symptoms in rice. Appl Environ Microbiol 2007; 73:4950-8. [PMID: 17557855 PMCID: PMC1951028 DOI: 10.1128/aem.00105-07] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2007] [Accepted: 05/30/2007] [Indexed: 11/20/2022] Open
Abstract
Burkholderia glumae is an emerging rice pathogen in several areas around the world. Closely related Burkholderia species are important opportunistic human pathogens for specific groups of patients, such as patients with cystic fibrosis and patients with chronic granulomatous disease. Here we report that the first clinical isolate of B. glumae, strain AU6208, has retained its capability to be very pathogenic to rice. As previously reported for rice isolate B. glumae BGR1 (and also for the clinical isolate AU6208), TofI or TofR acyl homoserine lactone (AHL) quorum sensing played a pivotal role in rice virulence. We report that AHL quorum sensing in B. glumae AU6208 regulates secreted LipA lipase and toxoflavin, the phytotoxin produced by B. glumae. B. glumae AU6208 lipA mutants were no longer pathogenic to rice, indicating that the lipase is an important virulence factor. It was also established that type strain B. glumae ATCC 33617 did not produce toxoflavin and lipase and was nonpathogenic to rice. It was determined that in strain ATCC 33617 the LuxR family quorum-sensing sensor/regulator TofR was inactive. Introducing the tofR gene of B. glumae AU6208 in strain ATCC 33617 restored its ability to produce toxoflavin and the LipA lipase. This study extends the role of AHL quorum sensing in rice pathogenicity through the regulation of a lipase which was demonstrated to be a virulence factor. It is the first report of a clinical B. glumae isolate retaining strong rice pathogenicity and finally determined that B. glumae can undergo phenotypic conversion through a spontaneous mutation in the tofR regulator.
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Affiliation(s)
- Giulia Devescovi
- Bacteriology Group, International Centre for Genetic Engineering and Biotechnology, Padriciano 99, Trieste, Italy
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Miller CD, Kim YC, Anderson AJ. Competitiveness in root colonization by Pseudomonas putida requires the rpoS gene. Can J Microbiol 2004; 47:41-8. [PMID: 15049448 DOI: 10.1139/w00-123] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
The rpoS gene in Pseudomonas putida was essential for plant root colonization under competitive conditions from other microbes. The RpoS- mutant survived less well than the wild-type strain in culture medium, and unlike the wild-type, failed to colonize the roots in a peat matrix containing an established diverse microflora. The RpoS-deficient P. putida isolate was generated by insertion of a glucuronidase-npt cassette into the rpoS gene. The RpoS mutant had dose-dependent increased sensitivity to oxidative stress and produced Mn-superoxide dismutase activity earlier than the parent. While extracts from wild-type P. putida stationary-phase cells contained three isozymes of catalase (CatA, CatB, and CatC), the sigma38-deficient P. putida lacked CatB. These results are consistent with previous findings that CatB is induced in stationary-phase.
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Affiliation(s)
- C D Miller
- Department of Biology, Utah State University, Logan, UT 84522-5305, USA
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Navarro-Lloréns JM, Martínez-García E, Tormo A. Enterobacter cloacae rpoS promoter and gene organization. Arch Microbiol 2002; 179:33-41. [PMID: 12471502 DOI: 10.1007/s00203-002-0493-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2002] [Revised: 09/20/2002] [Accepted: 09/24/2002] [Indexed: 12/01/2022]
Abstract
The upstream region of the Enterobacter cloacae strain CECT960 rpoS gene was sequenced. An IS 10R element was found within the nlpD gene, between rpoSp and rpoS. The rpoS promoter, although functional, did not drive transcription of the gene in this strain. However, rpoS transcription depended on this promoter in strains that lacked the insertion sequence in nlpD. rpoSp showed growth-phase-dependent, sigma(S)-independent regulation. Transcription from rpoSp was strongly inhibited by glucose even though it was cAMP-receptor-protein (CRP)-independent. Its functionality was also independent of both integration host factor (IHF) and the alarmone ppGpp. RpoS-dependent resistance to some environmental stresses showed a quantitative response to RpoS levels under some conditions (alkaline pH and high osmolarity) but not others (acidic pH, high temperature, and UV irradiation).
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Affiliation(s)
- Juana María Navarro-Lloréns
- Departamento de Bioquímica y Biología Molecular I, Facultad de Ciencias Biológicas, Universidad Complutense de Madrid, 28040 Madrid, Spain
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Lin YH, Miyamoto C, Meighen EA. Cloning, sequencing, and functional studies of the rpoS gene from Vibrio harveyi. Biochem Biophys Res Commun 2002; 293:456-62. [PMID: 12054623 DOI: 10.1016/s0006-291x(02)00245-0] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
Abstract
The Vibrio harveyi rpoS gene which encodes an alternative sigma factor (sigma(s) or sigma(38)), has been cloned and characterized. The predicted protein sequence is closely related to RpoS proteins in other bacteria with up to 86% sequence identity. A rpoS null mutant of V. harveyi was constructed and the phenotype studied. Comparison of the properties of the V. harveyi wild type and rpoS deletion mutant showed that rpoS affected the ability of the cells to survive only under specific types of environmental stresses. The rpoS null mutant had a lower survival rate compared to the wild type parental strain at high concentrations of ethanol and in the stationary phase. In contrast to other bacteria, deletion of rpoS in V. harveyi did not affect the resistance of the cells to high osmolarity or hydrogen peroxide, suggesting the existence of alternative systems in V. harveyi responsible for resistance to these stresses. RpoS appears not to be involved in the control of luminescence in V. harveyi even though it is implicated in regulation of other acyl-homoserine dependent quorum sensing systems.
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Affiliation(s)
- Yi Hsing Lin
- Department of Biochemistry, McGill University, Montreal, Que., Canada H3G 1Y6
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Eastgate JA. Erwinia amylovora: the molecular basis of fireblight disease. MOLECULAR PLANT PATHOLOGY 2000; 1:325-329. [PMID: 20572979 DOI: 10.1046/j.1364-3703.2000.00044.x] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
UNLABELLED Summary Taxonomy: Bacteria; Proteobacteria; gamma subdivision; order Enterobacteriales; family Enterobacteriaceae; genus Erwinia. Microbiological properties: Gram-negative, motile rods. Related species:E. carotovora (soft-rot diseases), E. chrysanthemi (soft-rot diseases), E. (Pantoea) stewartii (Stewart's wilt of corn), E. (Pantoea) herbicola (epiphyte). HOST RANGE Affects rosaceous plants, primarily members of the Pomoideae. Economically important hosts are apple and pear. The commercial implications of fireblight outbreaks are aggravated by the limited effectiveness of current control measures. Disease symptoms:E. amylovora infection is characterized by water soaking of infected tissue, followed by wilting and tissue necrosis. Necrosis gives tissue a scorched, blackened appearance, giving rise to the name fireblight. Symptoms are often localized to blossom bracts or young shoots but, in highly susceptible hosts, can spread systemically resulting in death of the entire tree. Infections can vary in severity depending on climatic conditions and host susceptibility. Useful web site:http://www.agric.gov.ab.ca.
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Affiliation(s)
- J A Eastgate
- Biological Sciences, School of Engineering and Science, University of Paisley, Paisley, Scotland, PA1 2EB, UK
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Andersson RA, Kõiv V, Norman-Setterblad C, Pirhonen M. Role of RpoS in virulence and stress tolerance of the plant pathogen Erwinia carotovora subsp. carotovora. MICROBIOLOGY (READING, ENGLAND) 1999; 145 ( Pt 12):3547-3556. [PMID: 10627052 DOI: 10.1099/00221287-145-12-3547] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
The plant-pathogenic bacterium Erwinia carotovora subsp. carotovora causes plant disease mainly through a number of extracellular plant-cell-wall-degrading enzymes. In this study, the ability of an rpoS mutant of the Er. carotovora subsp. carotovora strain SCC3193 to infect plants and withstand environmental stress was characterized. This mutant was found to be sensitive to osmotic and oxidative stresses in vitro and to be deficient in glycogen accumulation. The production of extracellular enzymes in vitro was similar in the mutant and in the wild-type strains. However, the rpoS mutant caused more severe symptoms than the wild-type strain on tobacco plants and also produced more extracellular enzymes in planta, but did not grow to higher cell density in planta compared to the wild-type strain. When tested on plants with reduced catalase activities, which show higher levels of reactive oxygen species, the rpoS mutant was found to cause lower symptom levels and to have impaired growth. In addition, the mutant was unable to compete with the wild-type strain in planta and in vitro. These results suggest that a functional rpoS gene is needed mainly for survival in a competitive environment and during stress conditions, and not for effective infection of plants.
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Affiliation(s)
- Robert A Andersson
- Department of Plant Biology, Swedish University of Agricultural Sciences (SLU), PO Box 7080,SE-75007 Uppsala, Sweden 1
| | - Viia Kõiv
- Institute of Molecular and Cell Biology, University of Tartu, 23 Riia Street, EE 2400 Tartu, Republic of Estonia2
| | - Cecilia Norman-Setterblad
- Department of Plant Biology, Swedish University of Agricultural Sciences (SLU), PO Box 7080,SE-75007 Uppsala, Sweden 1
| | - Minna Pirhonen
- Department of Plant Biology, Swedish University of Agricultural Sciences (SLU), PO Box 7080,SE-75007 Uppsala, Sweden 1
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