151
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Holden N, Pritchard L, Toth I. Colonization outwith the colon: plants as an alternative environmental reservoir for human pathogenic enterobacteria. FEMS Microbiol Rev 2009; 33:689-703. [PMID: 19076238 DOI: 10.1111/j.1574-6976.2008.00153.x] [Citation(s) in RCA: 127] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/20/2023] Open
Abstract
Members of the Enterobacteriaceae have the capacity to adapt to a wide variety of environments and can be isolated from a range of host species across biological kingdoms. Bacteria that are pathogenic to animals, in particular humans, are increasingly found to be transmitted through the food chain by fruits and vegetables. Rather than simply contaminating plant surfaces, there is a growing body of evidence to show that these bacteria actively interact with plants and can colonize them as alternative hosts. This review draws together evidence from studies that investigate proven and potential mechanisms involved in colonization of plants by human pathogenic enterobacteria.
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Affiliation(s)
- Nicola Holden
- Department of Plant Pathology, Scottish Crop Research Institute, Invergowrie, Dundee, UK.
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152
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Figueiredo JEF, Gomes EA, Guimarães CT, de Paula Lana UG, Teixeira MA, Lima GVC, Bressan W. Molecular analysis of endophytic bacteria from the genus Bacillus isolated from tropical maize (Zea mays L.). Braz J Microbiol 2009; 40:522-34. [PMID: 24031395 PMCID: PMC3768548 DOI: 10.1590/s1517-838220090003000014] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2008] [Revised: 10/20/2008] [Accepted: 05/03/2009] [Indexed: 11/21/2022] Open
Abstract
Endophytic bacteria play an important role in agriculture by improving plant performance and adaptation against biotic and abiotic stresses. In the present study molecular methods were used for identifying Bacillus endophytic bacteria isolated from Brazilian sweet corn. SDS-PAGE of whole-cell protein extract of forty-two isolates revealed a high number of scrutinable bands. Twenty-four isolates were identified in nine different groups of duplicated bacteria and eighteen were identified as unique. Some high-accumulated polipeptides with variable length were observed in almost isolates. Partial sequencing of 16S ribosomal gene revealed that all isolates are Bacillus sp. and among thirteen isolates with similar protein profiles, two were different strains. Among the forty-two isolates identified by rDNA sequencing, Bacillus subitilis and B. pumilus were the most frequenty species (15 and 12 isolates, respectively) followed by B. licheniformes (7 isolates), B. cereus (5 isolates) and B. amiloliquefascens (3 isolates). According to present results, SDS-PAGE technique could be used as a fast and cheap first tool for identifying inter-specific variation in maize endophytic bacterial collections while rDNA sequencing could be applied for analyzing intra-specific variation among isolates with similar protein profile as well as for taxonomic studies.
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Affiliation(s)
| | | | | | | | | | | | - Wellington Bressan
- Laboratório de Microbiologia e Controle Biológico, Embrapa Milho e Sorgo, Sete Lagoas, MG, Brasil
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153
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Human enteric pathogens in produce: un-answered ecological questions with direct implications for food safety. Curr Opin Biotechnol 2009; 20:166-71. [DOI: 10.1016/j.copbio.2009.03.002] [Citation(s) in RCA: 89] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/25/2008] [Revised: 02/19/2009] [Accepted: 03/09/2009] [Indexed: 11/18/2022]
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154
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Recent advances in the microbial safety of fresh fruits and vegetables. ADVANCES IN FOOD AND NUTRITION RESEARCH 2009; 57:155-208. [PMID: 19595387 DOI: 10.1016/s1043-4526(09)57004-0] [Citation(s) in RCA: 136] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
Foodborne illness outbreaks linked to fresh produce are becoming more frequent and widespread. High impact outbreaks, such as that associated with spinach contaminated with Escherichia coli O157:H7, resulted in almost 200 cases of foodborne illness across North America and >$300 m market losses. Over the last decade there has been intensive research into gaining an understanding on the interactions of human pathogens with plants and how microbiological safety of fresh produce can be improved. The following review will provide an update on the food safety issues linked to fresh produce. An overview of recent foodborne illness outbreaks linked to fresh produce. The types of human pathogens encountered will be described and how they can be transferred from their normal animal or human host to fresh produce. The interaction of human pathogens with growing plants will be discussed, in addition to novel intervention methods to enhance the microbiological safety of fresh produce.
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155
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Hardoim PR, van Overbeek LS, Elsas JDV. Properties of bacterial endophytes and their proposed role in plant growth. Trends Microbiol 2008; 16:463-71. [PMID: 18789693 DOI: 10.1016/j.tim.2008.07.008] [Citation(s) in RCA: 674] [Impact Index Per Article: 42.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2007] [Revised: 06/26/2008] [Accepted: 07/14/2008] [Indexed: 01/25/2023]
Abstract
Bacterial endophytes live inside plants for at least part of their life cycle. Studies of the interaction of endophytes with their host plants and their function within their hosts are important to address the ecological relevance of endophytes. The modulation of ethylene levels in plants by bacterially produced 1-aminocyclopropane-1-carboxylate deaminase is a key trait that enables interference with the physiology of the host plant. Endophytes with this capacity might profit from association with the plant, because colonization is enhanced. In turn, host plants benefit by stress reduction and increased root growth. This mechanism leads to the concept of 'competent' endophytes, defined as endophytes that are equipped with genes important for maintenance of plant-endophyte associations. The ecological role of these endophytes and their relevance for plant growth are discussed here.
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Affiliation(s)
- Pablo R Hardoim
- Department of Microbial Ecology, Centre for Ecological and Evolutionary Studies, University of Groningen, Kerklaan 30, 9751 NN, Haren, The Netherlands
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156
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Affiliation(s)
- M P Doyle
- Centre for Food Safety, University of Georgia, Griffin, GA, USA.
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157
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Fouts DE, Tyler HL, DeBoy RT, Daugherty S, Ren Q, Badger JH, Durkin AS, Huot H, Shrivastava S, Kothari S, Dodson RJ, Mohamoud Y, Khouri H, Roesch LFW, Krogfelt KA, Struve C, Triplett EW, Methé BA. Complete genome sequence of the N2-fixing broad host range endophyte Klebsiella pneumoniae 342 and virulence predictions verified in mice. PLoS Genet 2008; 4:e1000141. [PMID: 18654632 PMCID: PMC2453333 DOI: 10.1371/journal.pgen.1000141] [Citation(s) in RCA: 180] [Impact Index Per Article: 11.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2008] [Accepted: 06/24/2008] [Indexed: 12/25/2022] Open
Abstract
We report here the sequencing and analysis of the genome of the nitrogen-fixing endophyte, Klebsiella pneumoniae 342. Although K. pneumoniae 342 is a member of the enteric bacteria, it serves as a model for studies of endophytic, plant-bacterial associations due to its efficient colonization of plant tissues (including maize and wheat, two of the most important crops in the world), while maintaining a mutualistic relationship that encompasses supplying organic nitrogen to the host plant. Genomic analysis examined K. pneumoniae 342 for the presence of previously identified genes from other bacteria involved in colonization of, or growth in, plants. From this set, approximately one-third were identified in K. pneumoniae 342, suggesting additional factors most likely contribute to its endophytic lifestyle. Comparative genome analyses were used to provide new insights into this question. Results included the identification of metabolic pathways and other features devoted to processing plant-derived cellulosic and aromatic compounds, and a robust complement of transport genes (15.4%), one of the highest percentages in bacterial genomes sequenced. Although virulence and antibiotic resistance genes were predicted, experiments conducted using mouse models showed pathogenicity to be attenuated in this strain. Comparative genomic analyses with the presumed human pathogen K. pneumoniae MGH78578 revealed that MGH78578 apparently cannot fix nitrogen, and the distribution of genes essential to surface attachment, secretion, transport, and regulation and signaling varied between each genome, which may indicate critical divergences between the strains that influence their preferred host ranges and lifestyles (endophytic plant associations for K. pneumoniae 342 and presumably human pathogenesis for MGH78578). Little genome information is available concerning endophytic bacteria. The K. pneumoniae 342 genome will drive new research into this less-understood, but important category of bacterial-plant host relationships, which could ultimately enhance growth and nutrition of important agricultural crops and development of plant-derived products and biofuels.
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158
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Schikora A, Carreri A, Charpentier E, Hirt H. The dark side of the salad: Salmonella typhimurium overcomes the innate immune response of Arabidopsis thaliana and shows an endopathogenic lifestyle. PLoS One 2008; 3:e2279. [PMID: 18509467 PMCID: PMC2386236 DOI: 10.1371/journal.pone.0002279] [Citation(s) in RCA: 107] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/26/2008] [Accepted: 03/23/2008] [Indexed: 11/22/2022] Open
Abstract
Salmonella enterica serovar typhimurium contaminated vegetables and fruits are considerable sources of human infections. Bacteria present in raw plant-derived nutrients cause salmonellosis, the world wide most spread food poisoning. This facultative endopathogen enters and replicates in host cells and actively suppresses host immune responses. Although Salmonella survives on plants, the underlying bacterial infection mechanisms are only poorly understood. In this report we investigated the possibility to use Arabidopsis thaliana as a genetically tractable host system to study Salmonella-plant interactions. Using green fluorescent protein (GFP) marked bacteria, we show here that Salmonella can infect various Arabidopsis tissues and proliferate in intracelullar cellular compartments. Salmonella infection of Arabidopsis cells can occur via intact shoot or root tissues resulting in wilting, chlorosis and eventually death of the infected organs. Arabidopsis reacts to Salmonella by inducing the activation of mitogen-activated protein kinase (MAPK) cascades and enhanced expression of pathogenesis related (PR) genes. The induction of defense responses fails in plants that are compromised in ethylene or jasmonic acid signaling or in the MKK3-MPK6 MAPK pathway. These findings demonstrate that Arabidopsis represents a true host system for Salmonella, offering unique possibilities to study the interaction of this human pathogen with plants at the molecular level for developing novel drug targets and addressing current safety issues in human nutrition.
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Affiliation(s)
- Adam Schikora
- Unité de Recherche en Génomique Végétale, Institut National de la Recherche Agronomique/Centre National de la Recherche Scientifique/University of Evry Val d'Essonne, Evry, France
| | - Alessandro Carreri
- Department of Plant Molecular Biology, Max F. Perutz Laboratories, Vienna, Austria
| | - Emmanuelle Charpentier
- Department of Microbiology and Immunobiology, Max F. Perutz Laboratories, Vienna, Austria
| | - Heribert Hirt
- Unité de Recherche en Génomique Végétale, Institut National de la Recherche Agronomique/Centre National de la Recherche Scientifique/University of Evry Val d'Essonne, Evry, France
- Department of Plant Molecular Biology, Max F. Perutz Laboratories, Vienna, Austria
- * E-mail:
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159
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Pugh ND, Tamta H, Balachandran P, Wu X, Howell J, Dayan FE, Pasco DS. The majority of in vitro macrophage activation exhibited by extracts of some immune enhancing botanicals is due to bacterial lipoproteins and lipopolysaccharides. Int Immunopharmacol 2008; 8:1023-32. [PMID: 18486914 DOI: 10.1016/j.intimp.2008.03.007] [Citation(s) in RCA: 46] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2008] [Revised: 02/22/2008] [Accepted: 03/06/2008] [Indexed: 12/31/2022]
Abstract
We have identified potent monocyte/macrophage activating bacterial lipoproteins within commonly used immune enhancing botanicals such as Echinacea, American ginseng and alfalfa sprouts. These bacterial lipoproteins, along with lipopolysaccharides, were substantially more potent than other bacterially derived components when tested in in vitro monocyte/macrophage activation systems. In experiments using RAW 264.7 and mouse peritoneal macrophages the majority (85-98%) of the activity within extracts from eight immune enhancing botanicals was eradicated by treatment with agents (lipoprotein lipase and polymyxin B) known to target these two bacterial components. Alfalfa sprouts exhibited the highest activity of those botanicals tested but the appearance of this activity during the germination of surface sterilized seeds was abolished by the presence of antibiotics. These studies indicate that the majority of the in vitro macrophage activating properties in extracts from these botanicals can be attributed to the presence of lipoproteins and lipopolysaccharides derived from bacteria and that bacterial endophytes may be a significant source of these components.
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Affiliation(s)
- Nirmal D Pugh
- National Center for Natural Products Research, Research Institute of Pharmaceutical Sciences, School of Pharmacy, University of Mississippi, University, MS 38677, USA
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160
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Compant S, Kaplan H, Sessitsch A, Nowak J, Ait Barka E, Clément C. Endophytic colonization of Vitis vinifera L. by Burkholderia phytofirmans strain PsJN: from the rhizosphere to inflorescence tissues. FEMS Microbiol Ecol 2008; 63:84-93. [PMID: 18081592 DOI: 10.1111/j.1574-6941.2007.00410.x] [Citation(s) in RCA: 126] [Impact Index Per Article: 7.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
The colonization pattern of Vitis vinifera L. by Burkholderia phytofirmans strain PsJN was determined using grapevine fruiting cuttings with emphasis on putative inflorescence colonization under nonsterile conditions. Two-week-old rooted plants harbouring flower bud initials, grown in nonsterile soil, were inoculated with PsJN:gfp2x. Plant colonization was subsequently monitored at various times after inoculation with plate counts and epifluorescence and/or confocal microscopy. Strain PsJN was chronologically detected on the root surfaces, in the endorhiza, inside grape inflorescence stalks, not inside preflower buds and flowers but rather as an endophyte inside young berries. Data demonstrated low endophytic populations of strain PsJN in inflorescence organs, i.e. grape stalks and immature berries with inconsistency among plants for bacterial colonization of inflorescences. Nevertheless, endophytic colonization of inflorescences by strain PsJN was substantial for some plants. Microscopic analysis revealed PsJN as a thriving endophyte in inflorescence organs after the colonization process. Strain PsJN was visualized colonizing the root surface, entering the endorhiza and spreading to grape inflorescence stalks, pedicels and then to immature berries through xylem vessels. In parallel to these observations, a natural microbial communities was also detected on and inside plants, demonstrating the colonization of grapevine by strain PsJN in the presence of other microorganisms.
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Affiliation(s)
- Stéphane Compant
- Laboratoire de Stress, Défenses et Reproduction des Plantes, Unité de Recherche Vignes et Vins de Champagne, UFR Sciences, Université de Reims Champagne-Ardenne, Reims Cédex 2, France
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161
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Heaton J, Jones K. Microbial contamination of fruit and vegetables and the behaviour of enteropathogens in the phyllosphere: a review. J Appl Microbiol 2008; 104:613-26. [DOI: 10.1111/j.1365-2672.2007.03587.x] [Citation(s) in RCA: 369] [Impact Index Per Article: 23.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
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162
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Ormeño-Orrillo E, Rosenblueth M, Luyten E, Vanderleyden J, Martínez-Romero E. Mutations in lipopolysaccharide biosynthetic genes impair maize rhizosphere and root colonization of Rhizobium tropici CIAT899. Environ Microbiol 2008; 10:1271-84. [PMID: 18312393 DOI: 10.1111/j.1462-2920.2007.01541.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Three transposon mutants of Rhizobium tropici CIAT899 affected in lipopolysaccharide (LPS) biosynthesis were characterized and their maize rhizosphere and endophytic root colonization abilities were evaluated. The disrupted genes coded for the following putative products: the ATPase component of an O antigen ABC-2 type transporter (wzt), a nucleotide-sugar dehydratase (lpsbeta2) and a bifunctional enzyme producing GDP-mannose (noeJ). Electrophoretic analysis of affinity purified LPS showed that all mutants lacked the smooth LPS bands indicating an O antigen minus phenotype. In the noeJ mutant, the rough LPS band migrated faster than the parental band, suggesting a truncated LPS core. When inoculated individually, the wzt and noeJ mutants colonize the rhizosphere and root to a lower extent than the parental strain while no differences were observed between the lpsbeta2 mutant and the parental strain. All mutants were impaired in competitive rhizosphere and root colonization. Pleiotropic effects of the mutations on known colonization traits such as motility and growth rate were observed, but they were not sufficient to explain the colonization behaviours. It was found that the LPS mutants were sensitive to the maize antimicrobial 6-methoxy-2-benzoxazolinone (MBOA). Only the combined effects of altered growth rate and susceptibility to maize antimicrobials could account for all the observed colonization phenotypes. The results suggest an involvement of the LPS in protecting R. tropici against maize defence response during rhizosphere and root colonization.
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Affiliation(s)
- Ernesto Ormeño-Orrillo
- Centro de Ciencias Genómicas, Universidad Nacional Autónoma de México, Apdo. Postal 565-A, Cuernavaca, Morelos, Mexico
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163
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Tyler HL, Triplett EW. Plants as a habitat for beneficial and/or human pathogenic bacteria. ANNUAL REVIEW OF PHYTOPATHOLOGY 2008; 46:53-73. [PMID: 18680423 DOI: 10.1146/annurev.phyto.011708.103102] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Non-plant pathogenic endophytic bacteria can promote plant growth, improve nitrogen nutrition, and, in some cases, are human pathogens. Recent work in several laboratories has shown that enteric bacteria are common inhabitants of the interior of plants. These observations led to the experiments that showed the entry into plants of enteric human pathogens such as Salmonella and E. coli O157:H7. The extent of endophytic colonization by strains is regulated by plant defenses and several genetic determinants necessary for this interior colonization in endophytic bacteria have been identified. The genomes of four endophytic bacteria now available should promote discovery of other genes that contribute to this phenotype. Common virulence factors in plant and animal pathogens have also been described in bacteria that can infect both plant and animal models. Future directions in all of these areas are proposed.
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Affiliation(s)
- Heather L Tyler
- Department of Microbiology and Cell Science, University of Florida, Gainesville, Florida 32611-0700, USA.
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164
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Affiliation(s)
- Gail M Preston
- Department of Plant Sciences, University of Oxford, South Parks Road, Oxford OX1 3RB, UK.
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165
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Klerks MM, Franz E, van Gent-Pelzer M, Zijlstra C, van Bruggen AHC. Differential interaction of Salmonella enterica serovars with lettuce cultivars and plant-microbe factors influencing the colonization efficiency. THE ISME JOURNAL 2007; 1:620-31. [PMID: 18043669 DOI: 10.1038/ismej.2007.82] [Citation(s) in RCA: 170] [Impact Index Per Article: 10.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
The availability of knowledge of the route of infection and critical plant and microbe factors influencing the colonization efficiency of plants by human pathogenic bacteria is essential for the design of preventive strategies to maintain safe food. This research describes the differential interaction of human pathogenic Salmonella enterica with commercially available lettuce cultivars. The prevalence and degree of endophytic colonization of axenically grown lettuce by the S. enterica serovars revealed a significant serovar-cultivar interaction for the degree of colonization (S. enterica CFUs per g leaf), but not for the prevalence. The evaluated S. enterica serovars were each able to colonize soil-grown lettuce epiphytically, but only S. enterica serovar Dublin was able to colonize the plants also endophytically. The number of S. enterica CFU per g of lettuce was negatively correlated to the species richness of the surface sterilized lettuce cultivars. A negative trend was observed for cultivars Cancan and Nelly, but not for cultivar Tamburo. Chemotaxis experiments revealed that S. enterica serovars actively move toward root exudates of lettuce cultivar Tamburo. Subsequent micro-array analysis identified genes of S. enterica serovar Typhimurium that were activated by the root exudates of cultivar Tamburo. A sugar-like carbon source was correlated with chemotaxis, while also pathogenicity-related genes were induced in presence of the root exudates. The latter revealed that S. enterica is conditioned for host cell attachment during chemotaxis by these root exudates. Finally, a tentative route of infection is described that includes plant-microbe factors, herewith enabling further design of preventive strategies.
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Affiliation(s)
- Michel M Klerks
- Wageningen University and Research Centre, Plant Research International BV, Wageningen, The Netherlands.
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166
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Klerks MM, van Gent-Pelzer M, Franz E, Zijlstra C, van Bruggen AHC. Physiological and molecular responses of Lactuca sativa to colonization by Salmonella enterica serovar Dublin. Appl Environ Microbiol 2007; 73:4905-14. [PMID: 17513585 PMCID: PMC1951040 DOI: 10.1128/aem.02522-06] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2006] [Accepted: 05/12/2007] [Indexed: 11/20/2022] Open
Abstract
This paper describes the physiological and molecular interactions between the human-pathogenic organism Salmonella enterica serovar Dublin and the commercially available mini Roman lettuce cv. Tamburo. The association of S. enterica serovar Dublin with lettuce plants was first determined, which indicated the presence of significant populations outside and inside the plants. The latter was evidenced from significant residual concentrations after highly efficient surface disinfection (99.81%) and fluorescence microscopy of S. enterica serovar Dublin in cross sections of lettuce at the root-shoot transition region. The plant biomass was reduced significantly compared to that of noncolonized plants upon colonization with S. enterica serovar Dublin. In addition to the physiological response, transcriptome analysis by cDNA amplified fragment length polymorphism analysis also provided clear differential gene expression profiles between noncolonized and colonized lettuce plants. From these, generally and differentially expressed genes were selected and identified by sequence analysis, followed by reverse transcription-PCR displaying the specific gene expression profiles in time. Functional grouping of the expressed genes indicated a correlation between colonization of the plants and an increase in expressed pathogenicity-related genes. This study indicates that lettuce plants respond to the presence of S. enterica serovar Dublin at physiological and molecular levels, as shown by the reduction in growth and the concurrent expression of pathogenicity-related genes. In addition, it was confirmed that Salmonella spp. can colonize the interior of lettuce plants, thus potentially imposing a human health risk when processed and consumed.
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Affiliation(s)
- M M Klerks
- Wageningen University and Research Centre, Plant Research International BV, Droevendaalsesteeg 1, 6709 PB Wageningen, The Netherlands.
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167
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Barazani O, von Dahl CC, Baldwin IT. Sebacina vermifera promotes the growth and fitness of Nicotiana attenuata by inhibiting ethylene signaling. PLANT PHYSIOLOGY 2007; 144:1223-32. [PMID: 17416638 PMCID: PMC1914189 DOI: 10.1104/pp.107.097543] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/05/2007] [Accepted: 03/27/2007] [Indexed: 05/14/2023]
Abstract
Sebacina vermifera, a growth-promoting endophytic fungus, significantly increases Nicotiana attenuata's growth but impairs both its herbivore resistance and its accumulation of the costly, jasmonic acid (JA)-regulated defense protein, trypsin proteinase inhibitor (TPI). To determine if the fungi's growth-promoting effects can be attributed to lower TPI-related defense costs, we inoculated transformed N. attenuata plants silenced in their ability to synthesize JA, JA-isoleucine, and TPI by antisense (lipoxygenase 3 [as-lox3] and Thr deaminase [as-td]) and inverted repeat (ir-tpi) expression, and found that inoculation promoted plant growth as in untransformed wild-type plants. Moreover, herbivore-elicited increases in JA and JA-isoleucine concentrations did not differ between inoculated and uninoculated wild-type plants. However, inoculation significantly reduced the morphological effect of 1-aminocyclopropane-1-carboxylic acid on wild-type seedlings in a triple response assay, suggesting that ethylene signaling was impaired. Furthermore, S. vermifera failed to promote the growth of N. attenuata plants transformed to silence ethylene production (1-aminocyclopropane-1-carboxylic acid oxidase [ir-aco]). Inoculating wild-type plants with S. vermifera decreased the ethylene burst elicited by applying Manduca sexta oral secretions to mechanical wounds. Accordingly, oral secretion-elicited transcript levels of the ethylene synthesis genes NaACS3, NaACO1, and NaACO3 in inoculated plants were significantly lower compared to these levels in uninoculated wild-type plants. Inoculation accelerated germination in wild-type seeds; however, uninoculated wild-type seeds germinated as rapidly as inoculated seeds in the presence of the ethylene scrubber KMnO(4). In contrast, neither inoculation nor KMnO(4) exposure influenced the germination of ir-aco seeds. We conclude that S. vermifera increases plant growth by impairing ethylene production independently of JA signaling and TPI production.
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Affiliation(s)
- Oz Barazani
- Department of Molecular Ecology, Max Planck Institute for Chemical Ecology, Beutenberg Campus, 07745 Jena, Germany
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168
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Picard C, Bosco M. Heterozygosis drives maize hybrids to select elite 2,4-diacethylphloroglucinol-producing Pseudomonas strains among resident soil populations. FEMS Microbiol Ecol 2007; 58:193-204. [PMID: 17064261 DOI: 10.1111/j.1574-6941.2006.00151.x] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022] Open
Abstract
By comparing the distribution of two genomic markers among Pseudomonas strains recovered from the rhizosphere of two maize hybrids with those of strains recovered from the rhizosphere of their four respective parental lines, we showed that both hybrids supported more elite probiotic strains than the parents. Elite Pseudomonas strains showed genomic potential for both an appropriate in vitro 2,4-diacetylphloroglucinol (DAPG) productivity, and a superior root-colonization ability. The actual biocontrol and root-colonization abilities of these strains were confirmed by bioassays on five fungal strains and on axenic maize plants. Furthermore, results on the abundance and genetic diversity of resident DAPG+ Pseudomonas strains indicated that each hybrid was able to select its own specific DAPG+ population, whereas the four parental lines were not. The evidence that heterozygosis can drive maize plants to select elite probiotic rhizospheric DAPG+ Pseudomonas strains opens the way to a new strategy in the set up of plant breeding for low-input and organic agriculture.
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Affiliation(s)
- Christine Picard
- Dipartimento di Scienze e Tecnologie Agroambientali, Area di Microbiologia, Alma Mater Studiorum- Università di Bologna, Bologna, Italy.
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169
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Teplitski M, Al-Agely A, Ahmer BMM. Contribution of the SirA regulon to biofilm formation in Salmonella enterica serovar Typhimurium. MICROBIOLOGY-SGM 2007; 152:3411-3424. [PMID: 17074910 DOI: 10.1099/mic.0.29118-0] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Orthologues of the Salmonella enterica serovar Typhimurium (S. typhimurium) BarA/SirA two-component system are important for biofilm formation and virulence in many gamma-Proteobacteria. In S. typhimurium, SirA activates the csrB and csrC carbon storage regulatory RNAs and the virulence gene regulators hilA and hilC. The regulatory RNAs antagonize the activity of the CsrA protein, allowing translation of those same virulence genes, and inhibiting the translation of flagellar genes. In this report, it was determined that SirA and the Csr system also control the fim operon that encodes type 1 fimbriae. sirA orthologues in other bacterial species, and the fim operon of S. typhimurium, are known to play a role in biofilm formation; therefore, all members of the S. typhimurium sirA regulon were tested for in vitro biofilm production. A sirA mutant, a csrB csrC double mutant, and a fimI mutant, were all defective in biofilm formation. Conversely, inactivation of flhDC increased biofilm formation. Therefore, SirA activates csrB, csrC and the fim operon to promote biofilm formation. In turn, csrB and csrC promote the translation of the fim operon, while at the same time inhibiting the translation of flagella, which are inhibitory to biofilm formation.
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Affiliation(s)
- Max Teplitski
- Soil and Water Science Department, IFAS, University of Florida, Gainesville, FL 32611-0290, USA
| | - Ali Al-Agely
- Soil and Water Science Department, IFAS, University of Florida, Gainesville, FL 32611-0290, USA
| | - Brian M M Ahmer
- Department of Microbiology, Ohio State University, 484 West 12th Avenue, Columbus, OH 43210-1292, USA
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170
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Aruscavage D, Lee K, Miller S, LeJeune J. Interactions Affecting the Proliferation and Control of Human Pathogens on Edible Plants. J Food Sci 2006. [DOI: 10.1111/j.1750-3841.2006.00157.x] [Citation(s) in RCA: 101] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
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171
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Rosenblueth M, Martínez-Romero E. Bacterial endophytes and their interactions with hosts. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:827-37. [PMID: 16903349 DOI: 10.1094/mpmi-19-0827] [Citation(s) in RCA: 569] [Impact Index Per Article: 31.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Recent molecular studies on endophytic bacterial diversity have revealed a large richness of species. Endophytes promote plant growth and yield, suppress pathogens, may help to remove contaminants, solubilize phosphate, or contribute assimilable nitrogen to plants. Some endophytes are seedborne, but others have mechanisms to colonize the plants that are being studied. Bacterial mutants unable to produce secreted proteins are impaired in the colonization process. Plant genes expressed in the presence of endophytes provide clues as to the effects of endophytes in plants. Molecular analysis showed that plant defense responses limit bacterial populations inside plants. Some human pathogens, such as Salmonella spp., have been found as endophytes, and these bacteria are not removed by disinfection procedures that eliminate superficially occurring bacteria. Delivery of endophytes to the environment or agricultural fields should be carefully evaluated to avoid introducing pathogens.
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Affiliation(s)
- Mónica Rosenblueth
- Centro de Ciencias Genómicas, Universidad Nacional Autóma de México, Apdo. Postal 565-A, Cuernavaca, México
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172
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Wang ET, Tan ZY, Guo XW, Rodríguez-Duran R, Boll G, Martínez-Romero E. Diverse endophytic bacteria isolated from a leguminous tree Conzattia multiflora grown in Mexico. Arch Microbiol 2006; 186:251-9. [PMID: 16862424 DOI: 10.1007/s00203-006-0141-5] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2006] [Revised: 05/18/2006] [Accepted: 05/24/2006] [Indexed: 11/24/2022]
Abstract
Conzattia multiflora is a leguminous tree present only in Mexico and Guatemala. There is no record about its symbiotic or pathogenic microbes. In this study, we found that numerous bacteria with 10(4)-10(6) individuals per gram of fresh epidermis were distributed in the tissue of this plant. All the bacteria isolated from the Conzattia epidermis were Gram-negative, facultative anaerobic rods and formed yellow or colorless colonies. They were identified as endophytes by inoculation tests. Some of the bacteria could significantly promote the growth of Conzattia seedlings. Nine different groups were defined by PCR-based RFLP, which were classified as Pantoea, Erwinia, Salmonella, Enterobacter, Citrobacter and Klebsiella by the phylogenetic analysis of 16S rRNA genes. The existence of plant-borne lineages of Salmonella indicates that the unexplored plants may harbor some unknown microbes.
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Affiliation(s)
- En Tao Wang
- Departamento de Microbiología, Escuela Nacional de Ciencias Biológicas, Instituto Politécnico Nacional, México DF, México.
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173
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Miché L, Battistoni F, Gemmer S, Belghazi M, Reinhold-Hurek B. Upregulation of jasmonate-inducible defense proteins and differential colonization of roots of Oryza sativa cultivars with the endophyte Azoarcus sp. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:502-11. [PMID: 16673937 DOI: 10.1094/mpmi-19-0502] [Citation(s) in RCA: 51] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/03/2023]
Abstract
The endophyte Azoarcus sp. strain BH72 expresses nitrogenase (nif) genes inside rice roots. We applied a proteomic approach to dissect responses of rice roots toward bacterial colonization and jasmonic acid (JA) treatment. Two sister lineages of Oryza sativa were analyzed with cv. IR42 showing a less compatible interaction with the Azoarcus sp. resulting in slight root browning whereas cv. IR36 was successfully colonized as determined by nifHi::gusA activity. External addition of JA inhibited colonization of roots and caused browning in contrast to the addition of ethylene, applied as ethephon (up to 5 mM). Only two of the proteins induced in cv. IR36 by JA were also induced by the endophyte (SalT, two isoforms). In contrast, seven JA-induced proteins were also induced by bacteria in cv. IR42, indicating that IR42 showed a stronger defense response. Mass spectrometry analysis identified these proteins as pathogenesis-related (PR) proteins (Prb1, RSOsPR10) or proteins sharing domains with receptorlike kinases induced by pathogens. Proteins strongly induced in roots in both varieties by JA were identified as Bowman-Birk trypsin inhibittors, germinlike protein, putative endo-1,3-beta-D-glucosidase, glutathion-S-transferase, and 1-propane-1-carboxylate oxidase synthase, peroxidase precursor, PR10-a, and a RAN protein previously not found to be JA-induced. Data suggest that plant defense responses involving JA may contribute to restricting endophytic colonization in grasses. Remarkably, in a compatible interaction with endophytes, JA-inducible stress or defense responses are apparently not important.
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Affiliation(s)
- Lucie Miché
- Laboratory of General Microbiology, Faculty of Biology and Chemistry, University of Bremen, PO. Box 33 40 40, D-28334 Bremen, Germany
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174
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Reinhold-Hurek B, Maes T, Gemmer S, Van Montagu M, Hurek T. An endoglucanase is involved in infection of rice roots by the not-cellulose-metabolizing endophyte Azoarcus sp. strain BH72. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2006; 19:181-8. [PMID: 16529380 DOI: 10.1094/mpmi-19-0181] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/06/2023]
Abstract
The nitrogen-fixing endophyte Azoarcus sp. strain BH72 infects roots of Kallar grass and rice inter- and intra-cellularly and can spread systemically into shoots without causing symptoms of plant disease. Although cellulose or its breakdown products do not support growth, this strain expresses an endoglucanase, which might be involved in infection. Sequence analysis of eglA places the secreted 34-kDa protein into the glycosyl hydrolases family 5, with highest relatedness (40% identity) to endoglucanases of the phytopathogenic bacteria Xanthomonas campestris and Ralstonia solanacearum. Transcriptional regulation studied by eglA:: gusA fusion was not significantly affected by cellulose or its breakdown products or by microaerobiosis. Strongest induction (threefold) was obtained in bacteria grown in close vicinity to rice roots. Visible sites of expression were the emergence points of lateral roots and root tips, which are the primary regions of ingress into the root. To study the role in endophytic colonization, eglA was inactivated by transposon mutagenesis. Systemic spreading of the eglA mutant and of a pilAB mutant into the rice shoot could no longer be detected by polymerase chain reaction. Microscopic inspection of infection revealed that the intracellular colonization of root epidermis cells was significantly reduced in the eglA- mutant BHE6 compared with the wild type and partially restored in the complementation mutant BHRE2 expressing eglA. This provides evidence that Azoarcus sp. endoglucanase is an important determinant for successful endophytic colonization of rice roots, suggesting an active bacterial colonization process.
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Affiliation(s)
- Barbara Reinhold-Hurek
- Laboratory of General Microbiology, University Bremen, P.O. Box 33 04 40, D-28334 Bremen, Germany.
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175
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Brandl MT. Fitness of human enteric pathogens on plants and implications for food safety. ANNUAL REVIEW OF PHYTOPATHOLOGY 2006; 44:367-92. [PMID: 16704355 DOI: 10.1146/annurev.phyto.44.070505.143359] [Citation(s) in RCA: 342] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/09/2023]
Abstract
The continuous rise in the number of outbreaks of foodborne illness linked to fresh fruit and vegetables challenges the notion that enteric pathogens are defined mostly by their ability to colonize the intestinal habitat. This review describes the epidemiology of produce-associated outbreaks of foodborne disease and presents recently acquired knowledge about the behavior of enteric pathogens on plants, with an emphasis on Salmonella enterica, Escherichia coli O157:H7, and Listeria monocytogenes. The growth and survival of enteric pathogens on plants are discussed in the light of knowledge and concepts in plant microbial ecology, including epiphytic fitness, the physicochemical nature of plant surfaces, biofilm formation, and microbe-microbe and plant-microbe interactions. Information regarding the various stresses that affect the survival of enteric pathogens and the molecular events that underlie their interactions in the plant environment provides a good foundation for assessing their role in the infectious dose of the pathogens when contaminated fresh produce is the vehicle of illness.
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Affiliation(s)
- Maria T Brandl
- Produce Safety and Microbiology Research Unit, Agricultural Research Services, U.S. Department of Agriculture, Albany, California 94710, USA.
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176
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Chi F, Shen SH, Cheng HP, Jing YX, Yanni YG, Dazzo FB. Ascending migration of endophytic rhizobia, from roots to leaves, inside rice plants and assessment of benefits to rice growth physiology. Appl Environ Microbiol 2005; 71:7271-8. [PMID: 16269768 PMCID: PMC1287620 DOI: 10.1128/aem.71.11.7271-7278.2005] [Citation(s) in RCA: 222] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Rhizobia, the root-nodule endosymbionts of leguminous plants, also form natural endophytic associations with roots of important cereal plants. Despite its widespread occurrence, much remains unknown about colonization of cereals by rhizobia. We examined the infection, dissemination, and colonization of healthy rice plant tissues by four species of gfp-tagged rhizobia and their influence on the growth physiology of rice. The results indicated a dynamic infection process beginning with surface colonization of the rhizoplane (especially at lateral root emergence), followed by endophytic colonization within roots, and then ascending endophytic migration into the stem base, leaf sheath, and leaves where they developed high populations. In situ CMEIAS image analysis indicated local endophytic population densities reaching as high as 9 x 10(10) rhizobia per cm3 of infected host tissues, whereas plating experiments indicated rapid, transient or persistent growth depending on the rhizobial strain and rice tissue examined. Rice plants inoculated with certain test strains of gfp-tagged rhizobia produced significantly higher root and shoot biomass; increased their photosynthetic rate, stomatal conductance, transpiration velocity, water utilization efficiency, and flag leaf area (considered to possess the highest photosynthetic activity); and accumulated higher levels of indoleacetic acid and gibberellin growth-regulating phytohormones. Considered collectively, the results indicate that this endophytic plant-bacterium association is far more inclusive, invasive, and dynamic than previously thought, including dissemination in both below-ground and above-ground tissues and enhancement of growth physiology by several rhizobial species, therefore heightening its interest and potential value as a biofertilizer strategy for sustainable agriculture to produce the world's most important cereal crops.
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Affiliation(s)
- Feng Chi
- Key Laboratory of Photosynthesis and Environmental Molecular Physiology, Institute of Botany, Chinese Academy of Sciences, Beijing 10093, People's Republic of China
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177
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Toth IK, Birch PRJ. Rotting softly and stealthily. CURRENT OPINION IN PLANT BIOLOGY 2005; 8:424-9. [PMID: 15970273 DOI: 10.1016/j.pbi.2005.04.001] [Citation(s) in RCA: 86] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/17/2005] [Accepted: 04/29/2005] [Indexed: 05/03/2023]
Abstract
The soft rot erwiniae, which are plant pathogens on potato and other crops world-wide, synthesize and secrete large quantities of plant cell wall degrading enzymes that are responsible for the soft rot phenotype, earning them the epithet 'brute force' pathogens. They have been distinguished from classic 'stealth' pathogens, such as Pseudomonas syringae, which possesses an extensive battery of Type III secreted effector proteins and phytotoxins to manipulate and suppress host defences. However, recent studies, including whole-genome sequencing, are revealing many components of stealth pathogenesis within the soft rot erwiniae (SRE), suggesting that 'stealth' and 'brute force' should not be regarded as mutually exclusive modes of pathogenesis.
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Affiliation(s)
- Ian K Toth
- Scottish Crop Research Institute (SCRI), Invergowrie, Dundee DD2 5DA, UK.
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