Postharvest Handling Conditions Affect Internalization of Salmonella in Baby Spinach during Washing

2013 ◽  
Vol 76 (7) ◽  
pp. 1145-1151 ◽  
Author(s):  
VICENTE M. GÓMEZ-LÓPEZ ◽  
ALICIA MARÍN ◽  
ANA ALLENDE ◽  
LARRY R. BEUCHAT ◽  
MARÍA I. GIL
Keyword(s):  
Green Fluorescent Protein ◽  
Laser Scanning ◽  
Fluorescent Protein ◽  
Negative Temperature ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Temperature Differential ◽  
Postharvest Handling ◽  
Green Fluorescent ◽  
Spinach Leaves

Internalization of foodborne pathogens in fruits and vegetables is an increasing safety concern. The aim of this research was to assess the potential for internalization of an enteric pathogen (Salmonella enterica serotype Typhimurium) in a leafy vegetable (baby spinach) during washing as influenced by three postharvest handling conditions: (i) illumination, (ii) negative temperature differential, and (iii) relative humidity (RH). To compare these potential postharvest handling conditions, leaves were exposed to different levels of illumination (0, 1,000, and 2,000 lx), temperature differential (5, 11, 14, 20, and 26uC), and RH (99, 85, and 74%) for a short time before or during washing. Washing of baby spinach was carried out in water containing green fluorescent protein–tagged Salmonella Typhimurium (6.5 log CFU/ml) at 5uC for 2 min, followed by surface disinfection with chlorine (10,000 μg/ml) for 1 min, two rinses in water for 10 s, and spin drying for 15 s. Internalization was assessed by enumerating the pathogen on Salmonella-Shigella agar and by confocal laser scanning microscopy. Illumination of spinach leaves before and during washing and a negative temperature differential during washing did not significantly (P > 0.05) increase the number of internalized bacteria. However, exposure of leaves to low-RH conditions before washing, which reduced the tissue water content, decreased internalization of Salmonella compared with internalization in baby spinach exposed to high RH (P ≤ 0.05). Green fluorescent protein–tagged Salmonella Typhimurium was visualized by confocal laser scanning microscopy at a depth of up to 30 μm beneath the surface of spinach leaves after exposure to a high inoculum level (8 log CFU/ml) for an extended time (2 h). Results show that internalization of Salmonella into baby spinach leaves can occur but can be minimized under specific postharvest handling conditions such as low RH.

Migration of Salmonella Enteritidis Phage Type 30 through Almond Hulls and Shells

2008 ◽  
Vol 71 (2) ◽  
pp. 397-401 ◽  
Author(s):  
MICHELLE D. DANYLUK ◽  
MARIA T. BRANDL ◽  
LINDA J. HARRIS
Keyword(s):  
Green Fluorescent Protein ◽  
Laser Scanning ◽  
Salmonella Enteritidis ◽  
Fluorescent Protein ◽  
Phage Type ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Aqueous Environment ◽  
Serovar Typhimurium ◽  
Green Fluorescent

The ability of Salmonella to migrate from an external aqueous environment through the almond hull and shell, and to colonize the kernel, was evaluated in two ways. First, the outer surface of shell halves from five varieties of almonds that differed in shell hardness were placed in contact with a suspension of Salmonella enterica serovar Enteritidis phage type 30 for 24hat24°C. Salmonella Enteritidis was isolated from the inside of these almond shells in 46 and 100% of the samples, by direct swabbing of the inner surface of the shell and by enrichment from the swab, respectively. These findings suggested that hardness of the shell is not a significant factor in the migration of the pathogen through that tissue. In addition, both motile and nonmotile strains of S. enterica serovar Typhimurium migrated through the almond shells to the same extent under the conditions of this assay, indicating that bacterial migration through the wet shell may be a passive process. Second, whole almonds (intact hull, shell, and kernel) were soaked for 24 to 72 h at 24°C in a suspension of Salmonella Enteritidis phage type 30 labeled with the green fluorescent protein. Green fluorescent protein–labeled Salmonella cells were observed on the outer and inner surfaces of both the almond hull and shell, and on the kernel, by confocal laser scanning microscopy. Our data provide direct evidence that wet conditions allow for Salmonella migration through the hull and shell and onto the almond kernel, thus providing a means by which almond kernels may become contaminated in the field.

scholarly journals Systemic Colonization of Potato Plants by a Soilborne, Green Fluorescent Protein-Tagged Strain of Dickeya sp. Biovar 3

2010 ◽  
Vol 100 (2) ◽  
pp. 134-142 ◽  
Author(s):  
Robert Czajkowski ◽  
Waldo J. de Boer ◽  
Henk Velvis ◽  
Jan M. van der Wolf
Keyword(s):  
Green Fluorescent Protein ◽  
Laser Scanning ◽  
Fluorescent Protein ◽  
Agar Medium ◽  
Lateral Roots ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Potato Plants ◽  
Soil Inoculation ◽  
Green Fluorescent

Colonization of potato plants by soilborne, green fluorescent protein (GFP)-tagged Dickeya sp. IPO2254 was investigated by selective plating, epifluorescence stereo microscopy (ESM), and confocal laser scanning microscopy (CLSM). Replicated experiments were carried out in a greenhouse using plants with an intact root system and plants from which ca. 30% of the lateral roots was removed. One day after soil inoculation, adherence of the pathogen on the roots and the internal colonization of the plants were detected using ESM and CLSM of plant parts embedded in an agar medium. Fifteen days post-soil inoculation, Dickeya sp. was found on average inside 42% of the roots, 13% of the stems, and 13% of the stolons in plants with undamaged roots. At the same time-point, in plants with damaged roots, Dickeya sp. was found inside 50% of the roots, 25% of the stems, and 25% of the stolons. Thirty days postinoculation, some plants showed true blackleg symptoms. In roots, Dickeya sp. was detected in parenchyma cells of the cortex, both inter- and intracellularly. In stems, bacteria were found in xylem vessels and in protoxylem cells. Microscopical observations were confirmed by dilution spread-plating the plant extracts onto agar medium directly after harvest. The implications of infection from soilborne inoculum are discussed.

scholarly journals Green Fluorescent Protein-Marked Pseudomonas fluorescens: Localization, Viability, and Activity in the Natural Barley Rhizosphere

1999 ◽  
Vol 65 (10) ◽  
pp. 4646-4651 ◽  
Author(s):  
Bo Normander ◽  
Niels B. Hendriksen ◽  
Ole Nybroe
Keyword(s):  
Green Fluorescent Protein ◽  
Pseudomonas Fluorescens ◽  
Laser Scanning ◽  
Fluorescent Protein ◽  
Green Fluorescent Protein Fluorescence ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Protein Fluorescence ◽  
Dividing Cells ◽  
Green Fluorescent

ABSTRACT The gfp-tagged Pseudomonas fluorescensbiocontrol strain DR54-BN14 was introduced into the barley rhizosphere. Confocal laser scanning microscopy revealed that the rhizoplane populations of DR54-BN14 on 3- to 14-day-old roots were able to form microcolonies closely associated with the indigenous bacteria and that a majority of DR54-BN14 cells appeared small and almost coccoid. Information on the viability of the inoculant was provided by a microcolony assay, while measurements of cell volume, the intensity of green fluorescent protein fluorescence, and the ratio of dividing cells to total cells were used as indicators of cellular activity. At a soil moisture close to the water-holding capacity of the soil, the activity parameters suggested that the majority of DR54-BN14 cells were starving in the rhizosphere. Nevertheless, approximately 80% of the population was either culturable or viable but nonculturable during the 3-week incubation period. No impact of root decay on viability was observed, and differences in viability or activity among DR54-BN14 cells located in different regions of the root were not apparent. In dry soil, however, the nonviable state of DR54-BN14 was predominant, suggesting that desiccation is an important abiotic regulator of cell viability.

scholarly journals Spitzenkörper Localization and Intracellular Traffic of Green Fluorescent Protein-Labeled CHS-3 and CHS-6 Chitin Synthases in Living Hyphae of Neurospora crassa

2007 ◽  
Vol 6 (10) ◽  
pp. 1853-1864 ◽  
Author(s):  
Meritxell Riquelme ◽  
Salomon Bartnicki-García ◽  
Juan Manuel González-Prieto ◽  
Eddy Sánchez-León ◽  
Jorge A. Verdín-Ramos ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Neurospora Crassa ◽  
Laser Scanning ◽  
Fluorescent Dyes ◽  
Fluorescent Protein ◽  
Golgi Body ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Chitin Synthases ◽  
Green Fluorescent

ABSTRACT The subcellular location and traffic of two selected chitin synthases (CHS) from Neurospora crassa, CHS-3 and CHS-6, labeled with green fluorescent protein (GFP), were studied by high-resolution confocal laser scanning microscopy. While we found some differences in the overall distribution patterns and appearances of CHS-3-GFP and CHS-6-GFP, most features were similar and were observed consistently. At the hyphal apex, fluorescence congregated into a conspicuous single body corresponding to the location of the Spitzenkörper (Spk). In distal regions (beyond 40 μm from the apex), CHS-GFP revealed a network of large endomembranous compartments that was predominantly comprised of irregular tubular shapes, while some compartments were distinctly spherical. In the distal subapex (20 to 40 μm from the apex), fluorescence was observed in globular bodies that appeared to disintegrate into vesicles as they advanced forward until reaching the proximal subapex (5 to 20 μm from the apex). CHS-GFP was also conspicuously found delineating developing septa. Analysis of fluorescence recovery after photobleaching suggested that the fluorescence of the Spk originated from the advancing population of microvesicles (chitosomes) in the subapex. The inability of brefeldin A to interfere with the traffic of CHS-containing microvesicles and the lack of colocalization of CHS-GFP with the endoplasmic reticulum (ER)-Golgi body fluorescent dyes lend support to the idea that CHS proteins are delivered to the cell surface via an alternative route distinct from the classical ER-Golgi body secretory pathway.

Green fluorescent protein: Use of GFP-chimeras in the analysis of microtubule-associated protein 4 domains and microtubule dynamics

1996 ◽  
Vol 54 ◽  
pp. 888-889
Author(s):  
J.B. Olmsted ◽  
K.R. Olson ◽  
M.L. Gonzalez-Garay ◽  
F. Cabral
Keyword(s):  
Green Fluorescent Protein ◽  
Laser Scanning ◽  
Fluorescent Protein ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Gfp Reporter ◽  
Associated Proteins ◽  
Potential Applications ◽  
Exogenous Expression ◽  
Green Fluorescent

Green Fluorescent Protein (GFP) is an endogenous 27 kDa fluorophore of the jellyfish, Aequorea victoria. Chalfie et al., first described the exogenous expression of this molecule in bacteria, and its utility as a reporter in higher eukaryotes. Potential applications of GFP have been expanded through the construction of variants with enhanced brightness and/or different spectral properties.We have explored using GFP for the analysis of the real-time behaviors of microtubules and their associated proteins. Constructs of microtubule-associated protein 4 (MAP 4) or β-tubulin were generated in pRC/CMV vectors and used in either transient or stable transfection assays in a variety of cultured cell lines (3T3, PtKl, BHK, CHO, Cos). The GFP-chimeras were visualized using conventional fluorescence microscopy and confocal laser scanning microscopy. Unusual features of the GFP reporter are that fluorescence intensity increased 2-10 fold upon illumination, and that phototoxicity was low.

scholarly journals Novel Aspects of Tomato Root Colonization and Infection by Fusarium oxysporum f. sp. radicis-lycopersici Revealed by Confocal Laser Scanning Microscopic Analysis Using the Green Fluorescent Protein as a Marker

2002 ◽  
Vol 15 (2) ◽  
pp. 172-179 ◽  
Author(s):  
Anastasia L. Lagopodi ◽  
Arthur F. J. Ram ◽  
Gerda E. M. Lamers ◽  
Peter J. Punt ◽  
Cees A. M. J. J. Van den Hondel ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Fusarium Oxysporum ◽  
Laser Scanning ◽  
Fluorescent Protein ◽  
Microscopic Analysis ◽  
Laser Scanning Microscopy ◽  
Confocal Laser Scanning ◽  
Confocal Laser ◽  
Tomato Root ◽  
Green Fluorescent

The fungus Fusarium oxysporum f. sp. radicis-lycopersici is the causal agent of tomato foot and root rot disease. The green fluorescent protein (GFP) was used to mark this fungus in order to visualize and analyze the colonization and infection processes in vivo. Transformation of F. oxysporum f. sp. radicis-lycopersici was very efficient and gfp expression was stable for at least nine subcultures. Microscopic analysis of the transformants revealed homogeneity of the fluorescent signal, which was clearly visible in the hyphae as well as in the chlamydospores and conidia. To our knowledge, this is the first report in which this is shown. The transformation did not affect the pathogenicity. Using confocal laser scanning microscopy, colonization, infection, and disease development on tomato roots were visualized in detail and several new aspects of these processes were observed, such as (i) the complete colonization pattern of the tomato root system; (ii) the very first steps of contact between the fungus and the host, which takes place at the root hair zone by mingling and by the attachment of hyphae to the root hairs; (iii) the preferential colonization sites on the root surface, which are the grooves along the junctions of the epidermal cells; and (iv) the absence of specific infection sites, such as sites of emergence of secondary roots, root tips, or wounded tissue, and the absence of specific infection structures, such as appressoria. The results of this work prove that the use of GFP as a marker for F. oxysporum f. sp. radicis-lycopersici is a convenient, fast, and effective approach for studying plant-fungus interactions.

Monitoring of exocytosis and endocytosis of insulin secretory granules in the pancreatic β-cell line MIN6 using pH-sensitive green fluorescent protein (pHluorin) and confocal laser microscopy

2002 ◽  
Vol 363 (1) ◽  
pp. 73-80 ◽  
Author(s):  
Mica OHARA-IMAIZUMI ◽  
Yoko NAKAMICHI ◽  
Toshiaki TANAKA ◽  
Hidenori KATSUTA ◽  
Hitoshi ISHIDA ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Laser Scanning ◽  
Time Course ◽  
Fluorescent Protein ◽  
Secretory Granules ◽  
Ph Sensitive ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Min6 Cells ◽  
Green Fluorescent

The dynamics of exocytosis/endocytosis of insulin secretory granules in pancreatic β-cells remains to be clarified. In the present study, we visualized and analysed the motion of insulin secretory granules in MIN6 cells using pH-sensitive green fluorescent protein (pHluorin) fused to either insulin or the vesicle membrane protein, phogrin. In order to monitor insulin exocytosis, pHluorin, which is brightly fluorescent at approximately pH7.4, but not at approximately pH5.0, was attached to the C-terminus of insulin. To monitor the motion of insulin secretory granules throughout exocytosis/endocytosis, pHluorin was inserted between the third and fourth amino acids after the identified signal-peptide cleavage site of rat phogrin cDNA. Using this method of cDNA construction, pHluorin was located in the vesicle lumen, which may enable discrimination of the unfused acidic secretory granules from the fused neutralized ones. In MIN6 cells expressing insulin—pHluorin, time-lapse confocal laser scanning microscopy (5 or 10s intervals) revealed the appearance of fluorescent spots by depolarization after stimulation with 50mM KCl and 22mM glucose. The number of these spots in the image at the indicated times was counted and found to be consistent with the results of insulin release measured by RIA during the time course. In MIN6 cells expressing phogrin—pHluorin, data showed that fluorescent spots appeared following high KCl stimulation and remained stationary for a while, moved on the plasma membrane and then disappeared. Thus we demonstrate the visualized motion of insulin granule exocytosis/endocytosis using the pH-sensitive marker, pHluorin.

Intracellular Traffic of Glucocorticoid Receptors: Studies With Green Fluorescent Protein Chimeras in Living Cells

1997 ◽  
Vol 3 (S2) ◽  
pp. 131-132
Author(s):  
J. Barsony ◽  
J. Carroll ◽  
W. McKoy ◽  
I. Renyi ◽  
D.L. Gould ◽  
...  
Keyword(s):  
Green Fluorescent Protein ◽  
Laser Scanning ◽  
Glucocorticoid Receptors ◽  
Target Genes ◽  
Fluorescent Protein ◽  
Living Cells ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Intracellular Traffic ◽  
Green Fluorescent

As ligand-regulated transcription factors, glucocorticoid receptors (GR) must traffic through the cytoplasm, traverse the nuclear pores, and subsequently traffic within the the nucleus to reach their target genes. Due to technical difficulties with immunocytology, little is known about the translocation process or the intranuclear localization. The recent characterization of a chromophore, green fluorescent protein (GFP), provided a general tool to fluorescently label proteins in living cells. With the development of a transcriptionally active GFP-GR chimera, it became possible to visualize GR translocation and intranuclear distribution in living cells.This chimeric receptor was transiently transfected into mouse adenocarcinoma cells, allowing the direct visualization of GR using real-time video and confocal laser scanning microscopy. Mobility of GFP-GR was analyzed with fluorescent recovery after photobleaching (FRAP).The hormone-free GFP-GR was localized in the cytoplasm figure 1). Dexamethasone (lOnM) initiated GFP-GR translocation into the nucleus (Figure 2 and 3). The translocation rate was dose- and temperature-dependent, and occurred in a pulsatile manner along cytoplasmic fibrillar structures (Figure 2). FRAP experiments showed that GFP-GR remained in motion within the nucleus after translocation.

scholarly journals Functional Expression and Subcellular Localization of the Aflatoxin Pathway Enzyme Ver-1 Fused to Enhanced Green Fluorescent Protein

2008 ◽  
Vol 74 (20) ◽  
pp. 6385-6396 ◽  
Author(s):  
Sung-Yong Hong ◽  
John E. Linz
Keyword(s):  
Green Fluorescent Protein ◽  
Subcellular Localization ◽  
Fusion Proteins ◽  
Laser Scanning ◽  
Enhanced Green Fluorescent Protein ◽  
Fluorescent Protein ◽  
Substrate Surface ◽  
Laser Scanning Microscopy ◽  
Confocal Laser ◽  
Green Fluorescent

ABSTRACT Aflatoxin, a mycotoxin synthesized by Aspergillus spp., is among the most potent naturally occurring carcinogens known. Little is known about the subcellular organization of aflatoxin synthesis. Previously, we used transmission electron microscopy and immunogold labeling to demonstrate that the late aflatoxin enzyme OmtA localizes primarily to vacuoles in fungal cells on the substrate surface of colonies. In the present work, we monitored subcellular localization of Ver-1 in real time in living cells. Aspergillus parasiticus strain CS10-N2 was transformed with plasmid constructs that express enhanced green fluorescent protein (EGFP) fused to Ver-1. Analysis of transformants demonstrated that EGFP fused to Ver-1 at either the N or C terminus functionally complemented nonfunctional Ver-1 in recipient cells. Western blot analysis detected predominantly full-length Ver-1 fusion proteins in transformants. Confocal laser scanning microscopy demonstrated that Ver-1 fusion proteins localized in the cytoplasm and in the lumen of up to 80% of the vacuoles in hyphae grown for 48 h on solid media. Control EGFP (no Ver-1) expressed in transformants was observed in only 13% of the vacuoles at this time. These data support a model in which middle and late aflatoxin enzymes are synthesized in the cytoplasm and transported to vacuoles, where they participate in aflatoxin synthesis.

Sign in / Sign up

Export Citation Format

Share Document