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Barak JD, Schroeder BK. Interrelationships of food safety and plant pathology: the life cycle of human pathogens on plants. ANNUAL REVIEW OF PHYTOPATHOLOGY 2012; 50:241-66. [PMID: 22656644 DOI: 10.1146/annurev-phyto-081211-172936] [Citation(s) in RCA: 69] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/26/2023]
Abstract
Bacterial food-borne pathogens use plants as vectors between animal hosts, all the while following the life cycle script of plant-associated bacteria. Similar to phytobacteria, Salmonella, pathogenic Escherichia coli, and cross-domain pathogens have a foothold in agricultural production areas. The commonality of environmental contamination translates to contact with plants. Because of the chronic absence of kill steps against human pathogens for fresh produce, arrival on plants leads to persistence and the risk of human illness. Significant research progress is revealing mechanisms used by human pathogens to colonize plants and important biological interactions between and among bacteria in planta. These findings articulate the difficulty of eliminating or reducing the pathogen from plants. The plant itself may be an untapped key to clean produce. This review highlights the life of human pathogens outside an animal host, focusing on the role of plants, and illustrates areas that are ripe for future investigation.
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Affiliation(s)
- Jeri D Barak
- Department of Plant Pathology, University of Wisconsin, Madison, Wisconsin 53706, USA.
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52
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Functional genomics studies shed light on the nutrition and gene expression of non-typhoidal Salmonella and enterovirulent E. coli in produce. Food Res Int 2012. [DOI: 10.1016/j.foodres.2011.06.020] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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53
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Kroupitski Y, Pinto R, Belausov E, Sela S. Distribution of Salmonella typhimurium in romaine lettuce leaves. Food Microbiol 2011; 28:990-7. [PMID: 21569943 DOI: 10.1016/j.fm.2011.01.007] [Citation(s) in RCA: 59] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2010] [Revised: 01/16/2011] [Accepted: 01/25/2011] [Indexed: 11/29/2022]
Abstract
Leafy greens are occasionally involved in outbreaks of enteric pathogens. In order to control the plant contamination it is necessary to understand the factors that influence enteric pathogen-plant interactions. Attachment of Salmonella enterica serovar typhimurium to lettuce leaves has been demonstrated before; however, only limited information is available regarding the localization and distribution of immigrant Salmonella on the leaf surface. To extend our knowledge regarding initial pathogen-leaf interactions, the distribution of green-fluorescent protein-labeled Salmonella typhimurium on artificially contaminated romaine lettuce leaves was analyzed. We demonstrate that attachment of Salmonella to different leaf regions is highly variable; yet a higher attachment level was observed on leaf regions localized close to the petiole (7.7 log CFU g(-1)) compared to surfaces at the far-end region of the leaf blade (6.2 log CFU g(-1)). Attachment to surfaces located at a central leaf region demonstrated intermediate attachment level (7.0 log CFU g(-1)). Salmonella displayed higher affinity toward the abaxial side compared to the adaxial side of the same leaf region. Rarely, Salmonella cells were also visualized underneath stomata within the parenchymal tissue, supporting the notion that this pathogen can also internalize romaine lettuce leaves. Comparison of attachment to leaves of different ages showed that Salmonella displayed higher affinity to older compared to younger leaves (1.5 log). Scanning electron microscopy revealed a more complex topography on the surface of older leaves, as well as on the abaxial side of the examined leaf tissue supporting the notion that a higher attachment level might be correlated with a more composite leaf landscape. Our findings indicate that initial attachment of Salmonella to romaine lettuce leaf depends on multiple plant factors pertaining to the specific localization on the leaf tissue and to the developmental stage of the leaf.
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Affiliation(s)
- Yulia Kroupitski
- Microbial Food-Safety Research Unit, Department of Food Quality and Safety, Institute for Postharvest Technology and Food Sciences, Agricultural Research Organization, The Volcani Center, POB 6, Beth-Dagan 50250, Israel
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54
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Boyer RR, Sumner SS, Williams RC, Kniel KE, McKinney JM. Role of O-antigen on the Escherichia coli O157:H7 cells hydrophobicity, charge and ability to attach to lettuce. Int J Food Microbiol 2011; 147:228-32. [PMID: 21550681 DOI: 10.1016/j.ijfoodmicro.2011.04.016] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2010] [Revised: 03/31/2011] [Accepted: 04/12/2011] [Indexed: 11/17/2022]
Abstract
Environmental factors encountered during growing and harvesting may contribute to Escherichia coli O157:H7 contamination of lettuce. Limited nutrients and extended exposure to water may cause E. coli O157:H7 to shed its O antigen. Absence of the O157-polysaccharide antigen could affect the cell's physicochemical properties (hydrophobicity and cell charge) and ultimately influence its attachment to surfaces. The objectives of this study were to evaluate the effect of the E. coli O157:H7 O-antigen on the cell's overall hydrophobicity, charge and ability to attach to cut edge and whole leaf iceberg lettuce surfaces. Three strains of E. coli O157:H7 (86-24 wild type; F-12, mutant lacking the O-antigen and pRFBE, plasmid for O157 gene reintroduced) were examined for their hydrophobicity, overall charge and ability to attach to lettuce. Overall, E. coli O157:H7 attached at higher levels to cut surfaces over whole leaf surfaces (P=0.008) for all strains and treatments. Additionally, the strain lacking the O-antigen (F12)-attached significantly less to lettuce (P=0.015) than the strains expressing the antigen (WT and pRFBE). Cells lacking the O antigen (strain F-12) were also significantly more hydrophobic than strains 86-24 or pRFBE (P≤0.05). Surface charge differed among the strains tested (P≤0.05); however, it did not appear to influence bacterial attachment to lettuce surfaces. The charge was not fully restored in the pRFBE strain (expression of O-antigen reintroduced), therefore, no conclusions can be made pertaining to the effect of charge on attachment in this study. Results indicate that E. coli O157:H7 cells which lack the O-antigen have greater hydrophobicity and attach at lower concentrations than cells expressing the O-antigen, to iceberg lettuce surfaces.
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Affiliation(s)
- Renee R Boyer
- Department of Food Science and Technology, Virginia Tech, Blacksburg, VA 24061, USA.
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55
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Urgent advice on the public health risk of Shiga-toxin producingEscherichia coliin fresh vegetables. EFSA J 2011. [DOI: 10.2903/j.efsa.2011.2274] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022] Open
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56
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Noel JT, Arrach N, Alagely A, McClelland M, Teplitski M. Specific responses of Salmonella enterica to tomato varieties and fruit ripeness identified by in vivo expression technology. PLoS One 2010; 5:e12406. [PMID: 20824208 PMCID: PMC2930847 DOI: 10.1371/journal.pone.0012406] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2010] [Accepted: 07/26/2010] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Recent outbreaks of vegetable-associated gastroenteritis suggest that enteric pathogens colonize, multiply and persist in plants for extended periods of time, eventually infecting people. Genetic and physiological pathways, by which enterics colonize plants, are still poorly understood. METHODOLOGY/PRINCIPAL FINDINGS To better understand interactions between Salmonella enterica sv. Typhimurium and tomatoes, a gfp-tagged Salmonella promoter library was screened inside red ripe fruits. Fifty-one unique constructs that were potentially differentially regulated in tomato relative to in vitro growth were identified. The expression of a subset of these promoters was tested in planta using recombinase-based in vivo expression technology (RIVET) and fitness of the corresponding mutants was tested. Gene expression in Salmonella was affected by fruit maturity and tomato cultivar. A putative fadH promoter was upregulated most strongly in immature tomatoes. Expression of the fadH construct depended on the presence of linoleic acid, which is consistent with the reduced accumulation of this compound in mature tomato fruits. The cysB construct was activated in the fruit of cv. Hawaii 7997 (resistant to a race of Ralstonia solanacearum) more strongly than in the universally susceptible tomato cv. Bonny Best. Known Salmonella motility and animal virulence genes (hilA, flhDC, fliF and those encoded on the pSLT virulence plasmid) did not contribute significantly to fitness of the bacteria inside tomatoes, even though deletions of sirA and motA modestly increased fitness of Salmonella inside tomatoes. CONCLUSIONS/SIGNIFICANCE This study reveals the genetic basis of the interactions of Salmonella with plant hosts. Salmonella relies on a distinct set of metabolic and regulatory genes, which are differentially regulated in planta in response to host genotype and fruit maturity. This enteric pathogen colonizes tissues of tomatoes differently than plant pathogens, and relies little on its animal virulence genes for persistence within the fruit.
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Affiliation(s)
- Jason T. Noel
- Soil and Water Science Department, Genetics Institute, University of Florida, Gainesville, Florida, United States of America
| | - Nabil Arrach
- Vaccine Research Institute of San Diego, La Jolla, California, United States of America
- Sanford-Burnham Medical Research Institute, La Jolla, California, United States of America
| | - Ali Alagely
- Soil and Water Science Department, Genetics Institute, University of Florida, Gainesville, Florida, United States of America
| | - Michael McClelland
- Vaccine Research Institute of San Diego, La Jolla, California, United States of America
- Department of Pathology and Laboratory Medicine, University of California Irvine, Irvine, California, United States of America
| | - Max Teplitski
- Soil and Water Science Department, Genetics Institute, University of Florida, Gainesville, Florida, United States of America
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57
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Berger CN, Sodha SV, Shaw RK, Griffin PM, Pink D, Hand P, Frankel G. Fresh fruit and vegetables as vehicles for the transmission of human pathogens. Environ Microbiol 2010; 12:2385-97. [DOI: 10.1111/j.1462-2920.2010.02297.x] [Citation(s) in RCA: 581] [Impact Index Per Article: 41.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
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58
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Collignon S, Korsten L. Attachment and colonization by Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica subsp. enterica serovar Typhimurium, and Staphylococcus aureus on stone fruit surfaces and Survival through a simulated commercial export chain. J Food Prot 2010; 73:1247-56. [PMID: 20615337 DOI: 10.4315/0362-028x-73.7.1247] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The ability of the foodborne pathogens Escherichia coli O157:H7, Listeria monocytogenes, Salmonella enterica subsp. enterica serovar Typhimurium, and Staphylococcus aureus to attach, colonize, and survive on stone fruit surfaces was investigated. Fifty microliters of bacterial suspension was spot inoculated onto the sterile intact fructoplane of whole peaches and plums. Minimum time required for initial adhesion and attachment was recorded for different surface contact times. Surface colonization patterns of the four pathogens and survival under simulated commercial export conditions also were evaluated. L. monocytogenes and Salmonella Typhimurium attached immediately to stone fruit surfaces. E. coli O157:H7 and S. aureus were visibly attached after 30 s and 1 h, respectively, of direct exposure. Holding freshly harvested stone fruit at 0.5 degrees C to simulate cold storage conditions significantly lowered the titer of E. coli O157:H7 on plums and the titers of L. monocytogenes and Salmonella Typhimurium on stone fruit. E. coli O157:H7 and L. monocytogenes at a low inoculum level and S. aureus and Salmonella Typhimurium at high and low levels did not survive the simulated export chain conditions at titers that exceeded the minimum infectious dose. However, E. coli O157:H7 and L. monocytogenes were able to survive on stone fruit surfaces when inoculated at an artificially high level. In this case, the final titer at the end of the supply chain was higher than the infectious dose. In this laboratory experiment, E. coli O157:H7, L. monocytogenes, Salmonella Typhimurium, and S. aureus at potential natural contamination levels were unable to survive simulated export conditions.
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Affiliation(s)
- Stacey Collignon
- Department of Microbiology and Plant Pathology, University of Pretoria, Pretoria, South Africa
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59
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Microbial ecology of foodborne pathogens associated with produce. Curr Opin Biotechnol 2010; 21:125-30. [DOI: 10.1016/j.copbio.2010.01.006] [Citation(s) in RCA: 92] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2009] [Revised: 01/02/2010] [Accepted: 01/16/2010] [Indexed: 11/22/2022]
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60
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Biofilm formation by and multicellular behavior of Escherichia coli O55:H7, an atypical enteropathogenic strain. Appl Environ Microbiol 2010; 76:1545-54. [PMID: 20080991 DOI: 10.1128/aem.01395-09] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Enteropathogenic Escherichia coli (EPEC) is an important causal agent of diarrheal illness throughout the world. Nevertheless, researchers have only recently begun to explore its capacity to form biofilms. Strain O55:H7 (DMS9) is a clinical isolate belonging to the atypical EPEC (aEPEC) group, which displays a high degree of genetic relatedness to enterohemorrhagic E. coli. Strain DMS9 formed a robust biofilm on an abiotic surface at 26 degrees C, but not at 37 degrees C. It also formed a dense pellicle at the air-liquid interface and developed a red, rough, and dry (RDAR) morphotype on Congo red agar. Unlike a previously described E. coli O157:H7 strain, the aEPEC strain seems to express cellulose. Transposon mutagenesis was used to identify biofilm-deficient mutants. One of the mutants was inactivated in the csgFG genes, required for assembly and secretion of curli fimbriae, while a second mutant had a mutation in crl, a thermosensitive global regulator that modulates sigma(S) activity and downstream expression of curli and cellulose. The two mutants were deficient in their biofilm formation capabilities and did not form a pellicle at the air-liquid interface. Unlike in Salmonella, the csgFG mutant in aEPEC completely lost the RDAR phenotype, while the crl mutant displayed a unique RDAR "pizza"-like morphotype. Genetic complementation of the two mutants resulted in restoration of the wild-type phenotype. This report is the first to describe and analyze a multicellular behavior in aEPEC and support a major role for curli and the crl regulator in biofilm development at low temperatures corresponding to the nonmammalian host environment.
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61
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Barak JD, Gorski L, Liang AS, Narm KE. Previously uncharacterized Salmonella enterica genes required for swarming play a role in seedling colonization. MICROBIOLOGY-SGM 2009; 155:3701-3709. [PMID: 19713240 DOI: 10.1099/mic.0.032029-0] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Incidences of bacterial foodborne illness caused by ingestion of fresh produce are rising. Instead of this being due to incidental contamination, the animal pathogen Salmonella enterica utilizes specific molecular mechanisms to attach to and colonize plants. This work characterizes two S. enterica genes of unknown function: a putative periplasmic protein, STM0278, and a putative protein with a hydrolase in the C-terminus, STM0650. STM0278 and STM0650 are important for seedling colonization but appear to have different roles during the process of colonization. Mutants of either STM0278 or STM0650 showed reduced colonization of alfalfa seedlings at 24 h, and the STM0278 mutant also showed reduced colonization at 48 h. Both genes were expressed in planta at 4 h following inoculation of 3-day-old seedlings and at 72 h after seed inoculation. This suggests that the role of STM0650 in seedling colonization is less important later in the process or is duplicated by other mechanisms. Mutants of STM0278 and STM0650 were defective in swarming. The STM0278 mutant failed to swarm in 24 h, while swarming of the STM0650 mutant was delayed. Addition of surfactant restored swarming of the STM0278 mutant, suggesting that STM0278 is involved in surfactant or osmotic agent production or deployment. Alfalfa seed exudates as the sole nutrient source were capable of perpetuating S. enterica swarming. Sequence analysis revealed sequences homologous to STM0278 and STM0650 in plant-associated bacteria, but none in Escherichia coli. Phylogenetic analysis of STM0650 showed similar sequences from diverse classes of plant-associated bacteria. Bacteria that preferentially colonize roots, including S. enterica, may use a similar hydrolase for swarming or biofilm production on plants. Multicellular behaviours by S. enterica appear central to plant colonization. S. enterica genes involved in plant colonization and survival outside of a host are most likely among the 'function unknown' genes of this bacterium.
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Affiliation(s)
- Jeri D Barak
- Department of Plant Pathology, Rm 790 Russell Laboratories, 1630 Linden Drive, University of Wisconsin-Madison, Madison, WI 53706, USA
| | - Lisa Gorski
- Produce Safety and Microbiology Research Unit, USDA Agricultural Research Service, Albany, CA 94710, USA
| | - Anita S Liang
- Produce Safety and Microbiology Research Unit, USDA Agricultural Research Service, Albany, CA 94710, USA
| | - Koh-Eun Narm
- Produce Safety and Microbiology Research Unit, USDA Agricultural Research Service, Albany, CA 94710, USA
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62
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Abu-Ali GS, Lacher DW, Wick LM, Qi W, Whittam TS. Genomic diversity of pathogenic Escherichia coli of the EHEC 2 clonal complex. BMC Genomics 2009; 10:296. [PMID: 19575794 PMCID: PMC2713265 DOI: 10.1186/1471-2164-10-296] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2008] [Accepted: 07/03/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Evolutionary analyses of enterohemorrhagic Escherichia coli (EHEC) have identified two distantly related clonal groups: EHEC 1, including serotype O157:H7 and its inferred ancestor O55:H7; and EHEC 2, comprised of several serogroups (O26, O111, O118, etc.). These two clonal groups differ in their virulence and global distribution. Although several fully annotated genomic sequences exist for strains of serotype O157:H7, much less is known about the genomic composition of EHEC 2. In this study, we analyzed a set of 24 clinical EHEC 2 strains representing serotypes O26:H11, O111:H8/H11, O118:H16, O153:H11 and O15:H11 from humans and animals by comparative genomic hybridization (CGH) on an oligoarray based on the O157:H7 Sakai genome. RESULTS Backbone genes, defined as genes shared by Sakai and K-12, were highly conserved in EHEC 2. The proportion of Sakai phage genes in EHEC 2 was substantially greater than that of Sakai-specific bacterial (non-phage) genes. This proportion was inverted in O55:H7, reiterating that a subset of Sakai bacterial genes is specific to EHEC 1. Split decomposition analysis of gene content revealed that O111:H8 was more genetically uniform and distinct from other EHEC 2 strains, with respect to the Sakai O157:H7 gene distribution. Serotype O26:H11 was the most heterogeneous EHEC 2 subpopulation, comprised of strains with the highest as well as the lowest levels of Sakai gene content conservation. Of the 979 parsimoniously informative genes, 15% were found to be compatible and their distribution in EHEC 2 clustered O111:H8 and O118:H16 strains by serotype. CGH data suggested divergence of the LEE island from the LEE1 to the LEE4 operon, and also between animal and human isolates irrespective of serotype. No correlation was found between gene contents and geographic locations of EHEC 2 strains. CONCLUSION The gene content variation of phage-related genes in EHEC 2 strains supports the hypothesis that extensive modular shuffling of mobile DNA elements has occurred among EHEC strains. These results suggest that EHEC 2 is a multiform pathogenic clonal complex, characterized by substantial intra-serotype genetic variation. The heterogeneous distribution of mobile elements has impacted the diversification of O26:H11 more than other EHEC 2 serotypes.
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Affiliation(s)
- Galeb S Abu-Ali
- Microbial Evolution Laboratory, National Food Safety & Toxicology Center, 165 Food Safety & Toxicology Building, Michigan State University, East Lansing, Michigan 48824, USA
| | - David W Lacher
- Division of Molecular Biology, Center for Food Safety and Applied Nutrition, U.S. Food and Drug Administration, Laurel, Maryland 20708, USA
| | - Lukas M Wick
- Biosynth AG, Rietlistrasse 4, 9422 Staad, Switzerland
| | - Weihong Qi
- Functional Genomics Center Zurich, University of Zurich and Swiss Federal Institute of Technology Zurich, Winterthurerstrasse 190, 8057 Zurich, Switzerland
| | - Thomas S Whittam
- Microbial Evolution Laboratory, National Food Safety & Toxicology Center, 165 Food Safety & Toxicology Building, Michigan State University, East Lansing, Michigan 48824, USA
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63
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Kroupitski Y, Pinto R, Brandl MT, Belausov E, Sela S. Interactions of Salmonella enterica with lettuce leaves. J Appl Microbiol 2009; 106:1876-85. [PMID: 19239550 DOI: 10.1111/j.1365-2672.2009.04152.x] [Citation(s) in RCA: 93] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/16/2023]
Abstract
AIMS To investigate the interactions of Salmonella enterica with abiotic and plant surfaces and their effect on the tolerance of the pathogen to various stressors. METHODS AND RESULTS Salmonella strains were tested for their ability to form biofilm in various growth media using a polystyrene plate model. Strong biofilm producers were found to attach better to intact Romaine lettuce leaf tissue compared to weak producers. Confocal microscopy and viable count studies revealed preferential attachment of Salmonella to cut-regions of the leaf after 2 h at 25 degrees C, but not for 18 h at 4 degrees C. Storage of intact lettuce pieces contaminated with Salmonella for 9 days at 4 degrees C resulted only in small changes in population size. Exposure of lettuce-associated Salmonella cells to acidic conditions (pH 3.0) revealed increased tolerance of the attached vs planktonic bacteria. CONCLUSIONS Biofilm formation on polystyrene may provide a suitable model to predict the initial interaction of Salmonella with cut Romaine lettuce leaves. Association of the pathogen with lettuce leaves facilitates its persistence during storage and enhances its acid tolerance. SIGNIFICANCE AND IMPACT OF THE STUDY Understanding the interactions between foodborne pathogens and lettuce might be useful in developing new approaches to prevent fresh produce-associated outbreaks.
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Affiliation(s)
- Y Kroupitski
- Microbial Food-Safety Research Unit, Department of Food Science, Institute for Technology and Storage of Fresh Produce, Agricultural Research Organization, The Volcani Center, Beth-Dagan, Israel
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64
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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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65
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Couthouis J, Rébora K, Immel F, Berthelot K, Castroviejo M, Cullin C. Screening for toxic amyloid in yeast exemplifies the role of alternative pathway responsible for cytotoxicity. PLoS One 2009; 4:e4539. [PMID: 19262694 PMCID: PMC2650408 DOI: 10.1371/journal.pone.0004539] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2008] [Accepted: 02/02/2009] [Indexed: 11/24/2022] Open
Abstract
The relationship between amyloid and toxic species is a central problem since the discovery of amyloid structures in different diseases. Despite intensive efforts in the field, the deleterious species remains unknown at the molecular level. This may reflect the lack of any structure-toxicity study based on a genetic approach. Here we show that a structure-toxicity study without any biochemical prerequisite can be successfully achieved in yeast. A PCR mutagenesis of the amyloid domain of HET-s leads to the identification of a mutant that might impair cellular viability. Cellular and biochemical analyses demonstrate that this toxic mutant forms GFP-amyloid aggregates that differ from the wild-type aggregates in their shape, size and molecular organization. The chaperone Hsp104 that helps to disassemble protein aggregates is strictly required for the cellular toxicity. Our structure-toxicity study suggests that the smallest aggregates are the most toxic, and opens a new way to analyze the relationship between structure and toxicity of amyloid species.
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Affiliation(s)
- Julien Couthouis
- IBGC, UMR 5095, CNRS Université Bordeaux 2 “Victor Segalen”, Bordeaux, France
| | - Karine Rébora
- IBGC, UMR 5095, CNRS Université Bordeaux 2 “Victor Segalen”, Bordeaux, France
| | - Françoise Immel
- IBGC, UMR 5095, CNRS Université Bordeaux 2 “Victor Segalen”, Bordeaux, France
| | - Karine Berthelot
- IBGC, UMR 5095, CNRS Université Bordeaux 2 “Victor Segalen”, Bordeaux, France
| | - Michel Castroviejo
- REGER, UMR 5097 CNRS Université Bordeaux 2 “Victor Segalen”, Bordeaux, France
| | - Christophe Cullin
- IBGC, UMR 5095, CNRS Université Bordeaux 2 “Victor Segalen”, Bordeaux, France
- * E-mail:
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66
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Berthelot K, Immel F, Géan J, Lecomte S, Oda R, Kauffmann B, Cullin C. Driving amyloid toxicity in a yeast model by structural changes: a molecular approach. FASEB J 2009; 23:2254-63. [DOI: 10.1096/fj.08-125724] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Affiliation(s)
- Karine Berthelot
- Institut de Biochimie et Génétique CellulairesUniversité Bordeaux 2 “Victor Segalen”BordeauxFrance
| | - Franşoise Immel
- Institut de Biochimie et Génétique CellulairesUniversité Bordeaux 2 “Victor Segalen”BordeauxFrance
| | - Julie Géan
- Chimie et Biochimie des Membranes et Nano‐objetsUniversité Bordeaux 1PessacFrance
| | - Sophie Lecomte
- Chimie et Biochimie des Membranes et Nano‐objetsUniversité Bordeaux 1PessacFrance
| | - Reiko Oda
- Chimie et Biochimie des Membranes et Nano‐objetsUniversité Bordeaux 1PessacFrance
| | - Brice Kauffmann
- Chimie et Biochimie des Membranes et Nano‐objetsUniversité Bordeaux 1PessacFrance
| | - Christophe Cullin
- Institut de Biochimie et Génétique CellulairesUniversité Bordeaux 2 “Victor Segalen”BordeauxFrance
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67
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Fremaux B, Prigent-Combaret C, Vernozy-Rozand C. Long-term survival of Shiga toxin-producing Escherichia coli in cattle effluents and environment: An updated review. Vet Microbiol 2008; 132:1-18. [DOI: 10.1016/j.vetmic.2008.05.015] [Citation(s) in RCA: 100] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2007] [Revised: 05/14/2008] [Accepted: 05/20/2008] [Indexed: 01/01/2023]
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68
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Thomas T, Evans FF, Schleheck D, Mai-Prochnow A, Burke C, Penesyan A, Dalisay DS, Stelzer-Braid S, Saunders N, Johnson J, Ferriera S, Kjelleberg S, Egan S. Analysis of the Pseudoalteromonas tunicata genome reveals properties of a surface-associated life style in the marine environment. PLoS One 2008; 3:e3252. [PMID: 18813346 PMCID: PMC2536512 DOI: 10.1371/journal.pone.0003252] [Citation(s) in RCA: 90] [Impact Index Per Article: 5.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2008] [Accepted: 08/21/2008] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Colonisation of sessile eukaryotic host surfaces (e.g. invertebrates and seaweeds) by bacteria is common in the marine environment and is expected to create significant inter-species competition and other interactions. The bacterium Pseudoalteromonas tunicata is a successful competitor on marine surfaces owing primarily to its ability to produce a number of inhibitory molecules. As such P. tunicata has become a model organism for the studies into processes of surface colonisation and eukaryotic host-bacteria interactions. METHODOLOGY/PRINCIPAL FINDINGS To gain a broader understanding into the adaptation to a surface-associated life-style, we have sequenced and analysed the genome of P. tunicata and compared it to the genomes of closely related strains. We found that the P. tunicata genome contains several genes and gene clusters that are involved in the production of inhibitory compounds against surface competitors and secondary colonisers. Features of P. tunicata's oxidative stress response, iron scavenging and nutrient acquisition show that the organism is well adapted to high-density communities on surfaces. Variation of the P. tunicata genome is suggested by several landmarks of genetic rearrangements and mobile genetic elements (e.g. transposons, CRISPRs, phage). Surface attachment is likely to be mediated by curli, novel pili, a number of extracellular polymers and potentially other unexpected cell surface proteins. The P. tunicata genome also shows a utilisation pattern of extracellular polymers that would avoid a degradation of its recognised hosts, while potentially causing detrimental effects on other host types. In addition, the prevalence of recognised virulence genes suggests that P. tunicata has the potential for pathogenic interactions. CONCLUSIONS/SIGNIFICANCE The genome analysis has revealed several physiological features that would provide P. tunciata with competitive advantage against other members of the surface-associated community. We have also identified properties that could mediate interactions with surfaces other than its currently recognised hosts. This together with the detection of known virulence genes leads to the hypothesis that P. tunicata maintains a carefully regulated balance between beneficial and detrimental interactions with a range of host surfaces.
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Affiliation(s)
- Torsten Thomas
- Centre of Marine Bio-Innovation and School of Biotechnology and Biomolecular Sciences, The University of New South Wales, Sydney, New South Wales, Australia.
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69
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Matthysse AG, Deora R, Mishra M, Torres AG. Polysaccharides cellulose, poly-beta-1,6-n-acetyl-D-glucosamine, and colanic acid are required for optimal binding of Escherichia coli O157:H7 strains to alfalfa sprouts and K-12 strains to plastic but not for binding to epithelial cells. Appl Environ Microbiol 2008; 74:2384-90. [PMID: 18310435 PMCID: PMC2293172 DOI: 10.1128/aem.01854-07] [Citation(s) in RCA: 73] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2007] [Accepted: 02/14/2008] [Indexed: 11/20/2022] Open
Abstract
When Escherichia coli O157:H7 bacteria are added to alfalfa sprouts growing in water, the bacteria bind tightly to the sprouts. In contrast, laboratory K-12 strains of E. coli do not bind to sprouts under similar conditions. The roles of E. coli O157:H7 lipopolysaccharide (LPS), capsular polysaccharide, and exopolysaccharides in binding to sprouts were examined. An LPS mutant had no effect on the binding of the pathogenic strain. Cellulose synthase mutants showed a significant reduction in binding; colanic acid mutants were more severely reduced, and binding by poly-beta-1,6-N-acetylglucosamine (PGA) mutants was barely detectable. The addition of a plasmid carrying a cellulose synthase gene to K-12 strains allowed them to bind to sprouts. A plasmid carrying the Bps biosynthesis genes had only a marginal effect on the binding of K-12 bacteria. However, the introduction of the same plasmid allowed Sinorhizobium meliloti and a nonbinding mutant of Agrobacterium tumefaciens to bind to tomato root segments. These results suggest that although multiple redundant protein adhesins are involved in the binding of E. coli O157:H7 to sprouts, the polysaccharides required for binding are not redundant and each polysaccharide may play a distinct role. PGA, colanic acid, and cellulose were also required for biofilm formation by a K-12 strain on plastic, but not for the binding of E. coli O157:H7 to mammalian cells.
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Affiliation(s)
- Ann G Matthysse
- Department of Biology, Coker Hall, University of North Carolina, Chapel Hill, NC 27599-3280, USA.
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70
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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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71
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Barak JD, Jahn CE, Gibson DL, Charkowski AO. The role of cellulose and O-antigen capsule in the colonization of plants by Salmonella enterica. MOLECULAR PLANT-MICROBE INTERACTIONS : MPMI 2007; 20:1083-91. [PMID: 17849711 DOI: 10.1094/mpmi-20-9-1083] [Citation(s) in RCA: 123] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/17/2023]
Abstract
Numerous salmonellosis outbreaks have been associated with vegetables, in particular sprouted seed. Thin aggregative fimbriae (Tafi), a component of the extracellular matrix responsible for multicellular behavior, are important for Salmonella enterica attachment and colonization of plants. Here, we demonstrate that the other surface polymers composing the extracellular matrix, cellulose, and O-antigen capsule also play a role in colonization of plants. Mutations in bacterial cellulose synthesis (bcsA) and O-antigen capsule assembly and translocation (yihO) reduced the ability to attach to and colonize alfalfa sprouts. A colanic acid mutant was unaffected in plant attachment or colonization. Tafi, cellulose synthesis, and O-antigen capsule, all of which contribute to attachment and colonization of plants, are regulated by AgfD, suggesting that AgfD is a key regulator for survival outside of hosts of Salmonella spp. The cellulose biosynthesis regulator adrA mutant was not affected in the ability to attach to or colonize plants; however, promoter probe assays revealed expression by cells attached to alfalfa sprouts. Furthermore, quantitative reverse-transcriptase polymerase chain reaction revealed differential expression of agfD and adrA between planktonic and plant-attached cells. In addition, there was no correlation among mutants between biofilm formation in culture and attachment to plants. Outside of animal hosts, S. enterica appears to rely on an arsenal of adhesins to persist on plants, which can act as vectors and perpetuate public health concerns.
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Affiliation(s)
- Jeri D Barak
- Produce Safety and Microbiology Research Unit, United States Department of Agriculture-Agricultural Research Service, Albany, CA 94710, USA.
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72
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Hammer ND, Schmidt JC, Chapman MR. The curli nucleator protein, CsgB, contains an amyloidogenic domain that directs CsgA polymerization. Proc Natl Acad Sci U S A 2007; 104:12494-9. [PMID: 17636121 PMCID: PMC1941497 DOI: 10.1073/pnas.0703310104] [Citation(s) in RCA: 201] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Curli are functional amyloid fibers assembled by enteric bacteria such as Escherichia coli and Salmonella spp. In E. coli, the polymerization of the major curli fiber subunit protein CsgA into an amyloid fiber depends on the minor curli subunit protein, CsgB. The outer membrane-localized CsgB protein shares approximately 30% sequence identity with the amyloid-forming protein CsgA, suggesting that CsgB might also have amyloidogenic properties. Here, we characterized the biochemical properties of CsgB and the molecular basis for CsgB-mediated nucleation of CsgA. Deletion analysis revealed that a CsgB molecule missing 19 amino acids from its C terminus (CsgB(trunc)) was not outer membrane-associated, but secreted away from the cell. CsgB(trunc) was overexpressed and purified from the extracellular milieu of cells as an SDS-soluble, nonaggregated protein. Soluble CsgB(trunc) assembled into fibers that bound to the amyloid-specific dyes Congo red and thioflavin-T. CsgB(trunc) fibers were able to seed soluble CsgA polymerization in vitro. CsgB(trunc) displayed modest nucleator activity in vivo, as demonstrated by its ability to convert extracellular CsgA into an amyloid fiber. Unlike WT CsgB, CsgB(trunc) was only able to act as a nucleator when cells were genetically manipulated to secrete higher concentrations of CsgA. This work represents a unique demonstration of functional amyloid nucleation and it suggests an elegant model for how E. coli guides efficient amyloid fiber formation on the cell surface.
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Affiliation(s)
- Neal D. Hammer
- *Department of Microbiology and Immunology, University of Michigan Medical School, Ann Arbor, MI 48109-0620
| | - Jens C. Schmidt
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan College of Literature, Science, and the Arts, 830 North University, Ann Arbor, MI 48109-0620; and
| | - Matthew R. Chapman
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan College of Literature, Science, and the Arts, 830 North University, Ann Arbor, MI 48109-0620; and
- To whom correspondence should be addressed. E-mail:
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73
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Boyer RR, Sumner SS, Williams RC, Pierson MD, Popham DL, Kniel KE. Influence of curli expression by Escherichia coli 0157:H7 on the cell's overall hydrophobicity, charge, and ability to attach to lettuce. J Food Prot 2007; 70:1339-45. [PMID: 17612061 DOI: 10.4315/0362-028x-70.6.1339] [Citation(s) in RCA: 74] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
Curli fibers are produced by some Escherichia coli cells in response to environmental stimuli. These extracellular proteins enhance the cell's ability to form biofilms on various abiotic surfaces. E. coli 0157:H7 cells readily attach to a variety of fruit and vegetable surfaces. It is not known whether the expression of curli influences the cell's ability to attach to produce surfaces. In this study, the effect of curli expression on the cell's overall hydrophobicity, charge, and ability to attach to cut and whole iceberg lettuce surfaces was examined. All strains, regardless of curli expression, attached preferentially to the cut edges of lettuce (P < 0.05). The curli-producing cells of E. coli 0157:H7 strain E0018 attached in significantly greater numbers to both cut and whole lettuce pieces than did the non-curli-producing E0018 cells (P < 0.05); however, no significant attachment differences were observed between the curli-producing and non-curli-producing cells of E. coli 0157:H7 strains 43894 and 43895. All curli-producing E. coli 0157:H7 strains were significantly more hydrophobic (P < 0.01); however, no association between the cells' hydrophobic characteristics and lettuce attachment was observed. Overall surface charge of the cells did not differ among strains or curli phenotypes. Results indicate that overall hydrophobicity and cell charge in E. coli 0157:H7 strains do not influence attachment to iceberg lettuce surfaces. The presence of curli may not have any influence on attachment of E. coli 0157:H7 cells to produce items. Additional factorsmay influence the attachment of E. coli 0157:H7 to plant surfaces and should be further examined.
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Affiliation(s)
- Renee R Boyer
- Department of Food Science and Technology, , Virginia Polytechnic Institute and State University, Blacksburg, Virginia 24061, USA.
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74
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Abstract
Curli are the major proteinaceous component of a complex extracellular matrix produced by many Enterobacteriaceae. Curli were first discovered in the late 1980s on Escherichia coli strains that caused bovine mastitis, and have since been implicated in many physiological and pathogenic processes of E. coli and Salmonella spp. Curli fibers are involved in adhesion to surfaces, cell aggregation, and biofilm formation. Curli also mediate host cell adhesion and invasion, and they are potent inducers of the host inflammatory response. The structure and biogenesis of curli are unique among bacterial fibers that have been described to date. Structurally and biochemically, curli belong to a growing class of fibers known as amyloids. Amyloid fiber formation is responsible for several human diseases including Alzheimer's, Huntington's, and prion diseases, although the process of in vivo amyloid formation is not well understood. Curli provide a unique system to study macromolecular assembly in bacteria and in vivo amyloid fiber formation. Here, we review curli biogenesis, regulation, role in biofilm formation, and role in pathogenesis.
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Affiliation(s)
- Michelle M Barnhart
- Department of Molecular, Cellular, and Developmental Biology, University of Michigan, Ann Arbor, Michigan 48109, USA
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75
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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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Torres AG, Jeter C, Langley W, Matthysse AG. Differential binding of Escherichia coli O157:H7 to alfalfa, human epithelial cells, and plastic is mediated by a variety of surface structures. Appl Environ Microbiol 2005; 71:8008-15. [PMID: 16332780 PMCID: PMC1317338 DOI: 10.1128/aem.71.12.8008-8015.2005] [Citation(s) in RCA: 91] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2005] [Accepted: 08/15/2005] [Indexed: 11/20/2022] Open
Abstract
Escherichia coli O157:H7 carried on plant surfaces, including alfalfa sprouts, has been implicated in food poisoning and outbreaks of disease in the United States. Adhesion to cell surfaces is a key component for bacterial establishment and colonization on many types of surfaces. Several E. coli O157:H7 surface proteins are thought to be important for adhesion and/or biofilm formation. Therefore, we examined whether mutations in several genes encoding potential adhesins and regulators of adherence have an effect on bacterial binding to plants and also examined the role of these genes during adhesion to Caco-2 cells and during biofilm formation on plastic in vitro. The genes tested included those encoding adhesins (cah, aidA1, and ompA) and mediators of hyperadherence (tdcA, yidE, waaI, and cadA) and those associated with fimbria formation (csgA, csgD, and lpfD2). The introduction of some of these genes (cah, aidA1, and csg loci) into an E. coli K-12 strain markedly increased its ability to bind to alfalfa sprouts and seed coats. The addition of more than one of these genes did not show an additive effect. In contrast, deletion of one or more of these genes in a strain of E. coli O157:H7 did not affect its ability to bind to alfalfa. Only the absence of the ompA gene had a significant effect on binding, and the plant-bacterium interaction was markedly reduced in a tdcA ompA double mutant. In contrast, the E. coli O157:H7 ompA and tdcA ompA mutant strains were only slightly affected in adhesion to Caco-2 cells and during biofilm formation. These findings suggest that some adhesins alone are sufficient to promote binding to alfalfa and that they may exist in E. coli O157:H7 as redundant systems, allowing it to compensate for the loss of one or more of these systems. Binding to the three types of surfaces appeared to be mediated by overlapping but distinct sets of genes. The only gene which appeared to be irreplaceable for binding to plant surfaces was ompA.
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Affiliation(s)
- Alfredo G Torres
- Department of Microbiology and Immunology, Department of Pathology, and Sealy Center for Vaccine Development, University of Texas Medical Branch, Galveston, TX 77555-1070, USA.
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