scholarly journals Adjacent terrestrial landscapes impact the biogeographical pattern of soil Escherichia coli in produce fields by modifying the importance of environmental selection and dispersal

2020 ◽  
Author(s):  
Jingqiu Liao ◽  
Peter Bergholz ◽  
Martin Wiedmann
Keyword(s):  
Escherichia Coli ◽  
Land Use ◽  
New York State ◽  
Enteric Bacteria ◽  
Landscape Patterns ◽  
E Coli ◽  
Biogeographic Pattern ◽  
Environmental Selection ◽  
Forest Sites ◽  
Land Use Types

ABSTRACTHigh-quality habitats for wildlife (e.g., forest) provide essential ecosystem services while increasing species diversity and habitat connectivity. Unfortunately, presence of such habitats adjacent to produce fields may increase risk for contamination of fruits and vegetables by enteric bacteria, including Escherichia coli. E. coli survives in extra-host environments (e.g., soil) and could disperse across landscapes by wildlife. Understanding how terrestrial landscapes impact the distribution of soil E. coli is of importance in assessing the contamination risk of agricultural products. Here, using multi-locus sequence typing, we characterized 938 E. coli soil isolates collected from two watersheds with different landscape patterns in New York state, USA, and compared the distribution of E. coli and the influence of two ecological forces (environmental selection and dispersal) on the distribution between these two watersheds. Results showed that for the watershed with widespread produce fields, sparse forests, and limited interaction between the two land-use types, E. coli composition was significantly different between produce field sites and forest sites; this distribution was shaped by relatively strong environmental selection likely from soil phosphorus and slight dispersal limitation. For the watershed with more forested areas and stronger interaction between produce field sites and forest sites, E. coli composition between these two land-use types was relatively homogeneous; this distribution appeared to a consequence of wildlife-driven dispersal, inferred by competing models. Collectively, our results suggest that terrestrial landscape attributes could impact the biogeographic pattern of enteric bacteria by adjusting the importance of environmental selection and dispersal.IMPORTANCEUnderstanding the ecology of enteric bacteria in extra-host environments is important to allow for development and implementation of strategies to minimize pre-harvest contamination of produce with enteric pathogens. Our findings suggest that watershed landscape is an important factor influencing the importance of ecological drivers and dispersal patterns of E. coli. For watersheds with widespread produce fields, E. coli appears to experience local adaptation, possibly due to exposure to environmental stresses associated with agricultural activities. In contrast, for watersheds with high forest coverage we found evidence for wildlife-driven dispersal of E. coli, which might facilitate more frequent genetic exchange in this environment. Agricultural areas in such watersheds may have a higher risk of produce contamination due to less environmental constraints and higher potential of dispersal of enteric bacteria between locations. The significance of our research lies in exploring ecological principles underlying the biogeographic pattern of enteric bacteria at the regional level, which can inform agricultural, environmental and public health scientists that aim to reduce the risk of food contamination by enteric bacteria.

scholarly journals Adjacent Terrestrial Landscapes Impact the Biogeographical Pattern of Soil Escherichia coli Strains in Produce Fields by Modifying the Importance of Environmental Selection and Dispersal

2021 ◽  
Vol 87 (6) ◽  
Author(s):  
Jingqiu Liao ◽  
Peter Bergholz ◽  
Martin Wiedmann
Keyword(s):  
Public Health ◽  
Escherichia Coli ◽  
Land Use ◽  
Enteric Bacteria ◽  
Content Type ◽  
E Coli ◽  
Biogeographic Pattern ◽  
Environmental Selection ◽  
Forest Sites ◽  
Land Use Types

ABSTRACT High-quality habitats for wildlife (e.g., forest) provide essential ecosystem services while increasing species diversity and habitat connectivity. Unfortunately, the presence of such habitats adjacent to produce fields may increase risk for contamination of fruits and vegetables by enteric bacteria, including Escherichia coli. E. coli survives in extrahost environments (e.g., soil) and could be dispersed across landscapes by wildlife. Understanding how terrestrial landscapes impact the distribution of soil E. coli strains is of importance in assessing the contamination risk of agricultural products. Here, using multilocus sequence typing, we characterized 938 E. coli soil isolates collected from two watersheds with different landscape patterns in New York State, USA, and compared the distribution of E. coli and the influence that environmental selection and dispersal have on the distribution between these two watersheds. Results showed that for the watershed with widespread produce fields, sparse forests, and limited interaction between the two land use types, E. coli composition was significantly different between produce field sites and forest sites; this distribution appears to be shaped by relatively strong environmental selection, likely from soil phosphorus, and slight dispersal limitation. For the watershed with more forested areas and stronger interaction between produce field sites and forest sites, E. coli composition between these two land use types was relatively homogeneous; this distribution appeared to be a consequence of wildlife-driven dispersal, inferred by competing models. Collectively, our results suggest that terrestrial landscape attributes could impact the biogeographic pattern of enteric bacteria by adjusting the importance of environmental selection and dispersal. IMPORTANCE Understanding the ecology of enteric bacteria in extrahost environments is important for the development and implementation of strategies to minimize preharvest contamination of produce with enteric pathogens. Our findings suggest that watershed landscape is an important factor influencing the importance of ecological drivers and dispersal patterns of E. coli. Agricultural areas in such watersheds may have a higher risk of produce contamination due to fewer environmental constraints and higher potential of dispersal of enteric bacteria between locations. Thus, there is a perceived trade-off between priorities of environmental conservation and public health in on-farm food safety, with limited ecological data supporting or refuting the role of wildlife in dispersing pathogens under normal operating conditions. By combining field sampling and spatial modeling, we explored ecological principles underlying the biogeographic pattern of enteric bacteria at the regional level, which can benefit agricultural, environmental, and public health scientists who aim to reduce the risk of food contamination by enteric bacteria while minimizing negative impacts on wildlife habitats.

scholarly journals Functional Analysis of Genes Comprising the Locus of Heat Resistance in Escherichia coli

2017 ◽  
Vol 83 (20) ◽  
Author(s):  
Ryan Mercer ◽  
Oanh Nguyen ◽  
Qixing Ou ◽  
Lynn McMullen ◽  
Michael G. Gänzle
Keyword(s):  
Escherichia Coli ◽  
Heat Shock ◽  
Heat Shock Proteins ◽  
Heat Resistance ◽  
Growth Phase ◽  
Genomic Island ◽  
Enteric Bacteria ◽  
Content Type ◽  
E Coli ◽  
Shock Proteins

ABSTRACT The locus of heat resistance (LHR) is a 15- to 19-kb genomic island conferring exceptional heat resistance to organisms in the family Enterobacteriaceae, including pathogenic strains of Salmonella enterica and Escherichia coli. The complement of LHR-comprising genes that is necessary for heat resistance and the stress-induced or growth-phase-induced expression of LHR-comprising genes are unknown. This study determined the contribution of the seven LHR-comprising genes yfdX1 GI, yfdX2, hdeD GI, orf11, trx GI, kefB, and psiE GI by comparing the heat resistances of E. coli strains harboring plasmid-encoded derivatives of the different LHRs in these genes. (Genes carry a subscript “GI” [genomic island] if an ortholog of the same gene is present in genomes of E. coli.) LHR-encoded heat shock proteins sHSP20, ClpKGI, and sHSPGI are not sufficient for the heat resistance phenotype; YfdX1, YfdX2, and HdeD are necessary to complement the LHR heat shock proteins and to impart a high level of resistance. Deletion of trx GI, kefB, and psiE GI from plasmid-encoded copies of the LHR did not significantly affect heat resistance. The effect of the growth phase and the NaCl concentration on expression from the putative LHR promoter p2 was determined by quantitative reverse transcription-PCR and by a plasmid-encoded p2:GFP promoter fusion. The expression levels of exponential- and stationary-phase E. coli cells were not significantly different, but the addition of 1% NaCl significantly increased LHR expression. Remarkably, LHR expression in E. coli was dependent on a chromosomal copy of evgA. In conclusion, this study improved our understanding of the genes required for exceptional heat resistance in E. coli and factors that increase their expression in food. IMPORTANCE The locus of heat resistance (LHR) is a genomic island conferring exceptional heat resistance to several foodborne pathogens. The exceptional level of heat resistance provided by the LHR questions the control of pathogens by current food processing and preparation techniques. The function of LHR-comprising genes and their regulation, however, remain largely unknown. This study defines a core complement of LHR-encoded proteins that are necessary for heat resistance and demonstrates that regulation of the LHR in E. coli requires a chromosomal copy of the gene encoding EvgA. This study provides insight into the function of a transmissible genomic island that allows otherwise heat-sensitive enteric bacteria, including pathogens, to lead a thermoduric lifestyle and thus contributes to the detection and control of heat-resistant enteric bacteria in food.

scholarly journals Multiplex Polymerase Chain Reaction Assay for Identification of Enterotoxigenic Escherichia Coli Strains

2001 ◽  
Vol 13 (4) ◽  
pp. 308-311 ◽  
Author(s):  
Jacek Osek
Keyword(s):  
Escherichia Coli ◽  
Polymerase Chain Reaction ◽  
Multiplex Polymerase Chain Reaction ◽  
Direct Determination ◽  
Enteric Bacteria ◽  
Enterotoxigenic Escherichia Coli ◽  
Chain Reaction ◽  
Gram Negative ◽  
E Coli ◽  
Polymerase Chain

A multiplex polymerase chain reaction (PCR) system was developed for identification of enterotoxigenic Escherichia coli (ETEC) strains and to differentiate them from other gram negative enteric bacteria. This test simultaneously amplifies heat-labile (LTI) and heat-stable (STI and STII) toxin sequences and the E. coli-specific universal stress protein ( uspA). The specificity of the method was validated by single PCR tests performed with the reference E. coli and non- E. coli strains and with bacteria isolated from pig feces. The multiplex PCR allowed the rapid and specific identification of enterotoxin-positive E. coli and may be used as a method for direct determination of ETEC and to differentiate them from other E. coli and gram-negative enteric isolates.

scholarly journals The Escherichia coli K-12 NarL and NarP Proteins Insulate the nrf Promoter from the Effects of Integration Host Factor

2006 ◽  
Vol 188 (21) ◽  
pp. 7449-7456 ◽  
Author(s):  
Douglas F. Browning ◽  
David J. Lee ◽  
Alan J. Wolfe ◽  
Jeffrey A. Cole ◽  
Stephen J. W. Busby
Keyword(s):  
Escherichia Coli ◽  
Response Regulator ◽  
Regulatory Region ◽  
Enteric Bacteria ◽  
Integration Host Factor ◽  
Host Factor ◽  
Receptor Protein ◽  
E Coli ◽  
Serovar Typhimurium ◽  
K 12

ABSTRACT The Escherichia coli K-12 nrf operon promoter can be activated fully by the FNR protein (regulator of fumarate and nitrate reduction) binding to a site centered at position −41.5. FNR-dependent transcription is suppressed by integration host factor (IHF) binding at position −54, and this suppression is counteracted by binding of the NarL or NarP response regulator at position −74.5. The E. coli acs gene is transcribed from a divergent promoter upstream from the nrf operon promoter. Transcription from the major acsP2 promoter is dependent on the cyclic AMP receptor protein and is modulated by IHF and Fis binding at multiple sites. We show that IHF binding to one of these sites, located at position −127 with respect to the nrf promoter, has a positive effect on nrf promoter activity. This activation is dependent on the face of the DNA helix, independent of IHF binding at other locations, and found only when NarL/NarP are not bound at position −74.5. Binding of NarL/NarP appears to insulate the nrf promoter from the effects of IHF. The acs-nrf regulatory region is conserved in other pathogenic E. coli strains and related enteric bacteria but differs in Salmonella enterica serovar Typhimurium.

Attachment Strength to Pork Skin and Resistance to Quaternary Ammonium Salt and Heat of Escherichia coli Isolates Recovered from a Pork Slaughter Line

2005 ◽  
Vol 68 (11) ◽  
pp. 2447-2450 ◽  
Author(s):  
AZADEH NAMVAR ◽  
KEITH WARRINER
Keyword(s):  
Escherichia Coli ◽  
Ammonium Salt ◽  
Quaternary Ammonium ◽  
Quaternary Ammonium Salt ◽  
Enteric Bacteria ◽  
Salt Resistance ◽  
Inactivation Kinetics ◽  
Genetic Lineage ◽  
E Coli ◽  
Attachment Strength

The aim of this study was to determine whether the attachment strength to pork skin, quaternary ammonium salt resistance, and thermal inactivation kinetics (at 65°C) of a range of Escherichia coli isolates could be correlated with their temporal stability (persistence) within a pork slaughter line. The genetic lineage of the E. coli isolates was determined using entero-bacterial repetitive intergenic consensus–PCR. The genotypes were divided into transient and endemic populations based on the number of times they were recovered within and across sampling visits made to a pork slaughterhouse. No significant variation in the D-value at 65°C (0.27 to 0.51 min) was observed among the genotypes tested. However, differences in D-values were found for 100 ppm quaternary ammonium salt (3.0 to 6.0 min). All of the E. coli genotypes attached strongly to pork skin, and a high proportion of cells were irreversibly bound (39 to 42% of the initial inoculum). However, variation among genotypes was found with respect to loose attachment (21 to 33% of inoculated cells). No correlation between persistence of E. coli genotypes within the slaughter line and attachment strength or quaternary ammonium salt resistance was found. Variation in either physiological attribute could not be predicted based on genetic lineage. Additional or alternative factors may contribute to the ability of E. coli populations to become endemic within pork processing facilities. More studies should be conducted to elucidate the underlying factors that promote the formation of endemic populations of E. coli and other enteric bacteria (e.g., Salmonella) within slaughter lines.

scholarly journals Stationary-Phase Regulation of RpoS Translation in Escherichia coli

2005 ◽  
Vol 187 (21) ◽  
pp. 7204-7213 ◽  
Author(s):  
Matthew Hirsch ◽  
Thomas Elliott
Keyword(s):  
Escherichia Coli ◽  
Stationary Phase ◽  
Osmotic Shock ◽  
Transcriptional Response ◽  
Enteric Bacteria ◽  
Protein Activity ◽  
E Coli ◽  
Phase Regulation ◽  
Shine Dalgarno Sequence ◽  
Necessary And Sufficient

ABSTRACT In enteric bacteria, adaptation to a number of different stresses is mediated by the RpoS protein, one of several sigma factors that collectively allow a tailored transcriptional response to environmental cues. Stress stimuli including low temperature, osmotic shock, nutrient limitation, and growth to stationary phase (SP) all result in a substantial increase in RpoS abundance and activity. The mechanism of regulation depends on the specific signal but may occur at the level of transcription, translation, protein activity, or targeted proteolysis. In both Escherichia coli and Salmonella enterica, SP induction of RpoS in rich medium is >30 fold and includes effects on both transcription and translation. Recently, we found that SP control of rpoS transcription in S. enterica involves repression of the major rpoS promoter during exponential phase by the global transcription factor Fis. Working primarily with E. coli, we now show that 24 nucleotides of the rpoS ribosome-binding site (RBS) are necessary and sufficient for a large part of the increase in rpoS translation as cells grow to SP. Genetic evidence points to an essential role for the leader nucleotides just upstream of the Shine-Dalgarno sequence but is conflicted on the question of whether sequence or structure is important. SP regulation of rpoS is conserved between E. coli and S. enterica. When combined with an fis mutation to block transcriptional effects, replacement of the rpoS RBS sequence by the lacZ RBS eliminates nearly all SP induction of RpoS.

scholarly journals Induction of Cytolytic Anti-Gal Antibodies in α-1,3-Galactosyltransferase Gene Knockout Mice by Oral Inoculation with Escherichia coli O86:B7 Bacteria

2002 ◽  
Vol 70 (11) ◽  
pp. 6215-6222 ◽  
Author(s):  
Karla J. Posekany ◽  
H. Keith Pittman ◽  
John F. Bradfield ◽  
Carl E. Haisch ◽  
Kathryn M. Verbanac
Keyword(s):  
Escherichia Coli ◽  
Gene Knockout ◽  
Small Animal ◽  
Enteric Bacteria ◽  
Cytolytic Activity ◽  
Target Cells ◽  
E Coli ◽  
Oral Inoculation ◽  
Galt Gene ◽  
Gene Knockout Mice

ABSTRACT Naturally occurring antibodies against [Gal α-1,3-Gal] structures (anti-Gal antibodies) are the primary effectors of human hyperacute rejection (HAR) of nonhuman tissue. Unlike most mammals, humans lack a functional α-1,3-galactosyltransferase (GalT) gene and produce abundant anti-Gal antibodies, putatively in response to GalT+ enteric bacteria. GalT knockout (KO) mice have been generated as a small animal model of HAR but inconsistently express anti-Gal antibodies. We hypothesized that enteric exposure of GalT KO mice to live GalT+ bacteria would produce cytolytic anti-Gal antibodies. Naive mice lacking anti-Gal antibodies were orally immunized with 1010 live GalT+ Escherichia coli O86:B7 bacteria and assayed for anti-Gal antibody titer, isotype, and cytolytic activity. Fecal samples were tested for E. coli O86:B7 prior to and after inoculation. In two separate experiments, 77 to 100% (n = 31) of mice developed serum anti-Gal immunoglobulin G (IgG; titer, 1:5 to 1:80) and/or anti-Gal IgM antibodies (titer, 1:5 to 1:1,280) 14 days postinoculation. Induced anti-Gal antibodies caused complement-mediated cytolysis of GalT+ target cells, with extensive cytolysis observed consistently at serum IgM titers of ≥1:320. Absorption with synthetic [Gal α-1,3-Gal] inhibited both antibody binding and cytolysis. E. coli O86:B7 was recovered from stool samples from 83 to 94% of inoculated mice but not from naive mice, thus confirming enteric exposure. These findings demonstrate that oral inoculation with E. coli O86:B7 is a novel and effective method to induce cytolytic anti-Gal antibodies in GalT KO mice and support the premise that enteric exposure to GalT+ bacteria induces anti-Gal antibodies in humans. These studies also suggest a role for GalT KO mice in elucidating anti-Gal responses in microbial immunity.

Survival of Escherichia coli O157:H7 in soils under different land use types

2013 ◽  
Vol 21 (1) ◽  
pp. 518-524 ◽  
Author(s):  
Haizhen Wang ◽  
Taoxiang Zhang ◽  
Gang Wei ◽  
Laosheng Wu ◽  
Jianjun Wu ◽  
...  
Keyword(s):  
Escherichia Coli ◽  
Land Use ◽  
Escherichia Coli O157 ◽  
Land Use Types

scholarly journals Plant-Pathogenic Oomycetes, Escherichia coli Strains, and Salmonella spp. Frequently Found in Surface Water Used for Irrigation of Fruit and Vegetable Crops in New York State

2014 ◽  
Vol 80 (16) ◽  
pp. 4814-4820 ◽  
Author(s):  
Lisa A. Jones ◽  
Randy W. Worobo ◽  
Christine D. Smart
Keyword(s):  
Escherichia Coli ◽  
Water Quality ◽  
New York ◽  
Food Safety ◽  
Surface Water ◽  
New York State ◽  
Quality Parameters ◽  
Content Type ◽  
York State ◽  
E Coli

ABSTRACTIn the United States, surface water is commonly used to irrigate a variety of produce crops and can harbor pathogens responsible for food-borne illnesses and plant diseases. Understanding when pathogens infest water sources is valuable information for produce growers to improve the food safety and production of these crops. In this study, prevalence data along with regression tree analyses were used to correlate water quality parameters (pH, temperature, turbidity), irrigation site properties (source, the presence of livestock or fowl nearby), and precipitation data to the presence and concentrations ofEscherichia coli,Salmonellaspp., and hymexazol-insensitive (HIS) oomycetes (PhytophthoraandPythiumspp.) in New York State surface waters. A total of 123 samples from 18 sites across New York State were tested forE. coliandSalmonellaspp., of which 33% and 43% were positive, respectively. Additionally, 210 samples from 38 sites were tested for HIS oomycetes, and 88% were found to be positive, with 10 species ofPhytophthoraand 11 species ofPythiumbeing identified from the samples. Regression analysis found no strong correlations between water quality parameters, site factors, or precipitation to the presence or concentration ofE. coliin irrigation sources. ForSalmonella, precipitation (≤0.64 cm) 3 days before sampling was correlated to both presence and the highest counts. Analyses for oomycetes found creeks to have higher average counts than ponds, and higher turbidity levels were associated with higher oomycete counts. Overall, information gathered from this study can be used to better understand the food safety and plant pathogen risks of using surface water for irrigation.

scholarly journals Inactivation of Escherichia coli by Polychromatic Simulated Sunlight: Evidence for and Implications of a Fenton Mechanism Involving Iron, Hydrogen Peroxide, and Superoxide

2013 ◽  
Vol 80 (3) ◽  
pp. 935-942 ◽  
Author(s):  
Michael B. Fisher ◽  
Kara L. Nelson
Keyword(s):  
Escherichia Coli ◽  
Hydrogen Peroxide ◽  
Enteric Bacteria ◽  
Growth Conditions ◽  
Simulated Sunlight ◽  
Wild Type ◽  
Intracellular Iron ◽  
Content Type ◽  
E Coli ◽  
Degree Of Sensitization

ABSTRACTSunlight inactivation ofEscherichia colihas previously been shown to accelerate in the presence of oxygen, exogenously added hydrogen peroxide, and bioavailable forms of exogenously added iron. In this study, mutants unable to effectively scavenge hydrogen peroxide or superoxide were found to be more sensitive to polychromatic simulated sunlight (without UVB wavelengths) than wild-type cells, while wild-type cells grown under low-iron conditions were less sensitive than cells grown in the presence of abundant iron. Furthermore, prior exposure to simulated sunlight was found to sensitize cells to subsequent hydrogen peroxide exposure in the dark, but this effect was attenuated for cells grown with low iron. Mutants deficient in recombination DNA repair were sensitized to simulated sunlight (without UVB wavelengths), but growth in the presence of iron chelators reduced the degree of sensitization conferred by this mutation. These findings support the hypothesis that hydrogen peroxide, superoxide, and intracellular iron all participate in the photoinactivation ofE. coliand further suggest that the inactivation rate of enteric bacteria in the environment may be strongly dependent on iron availability and growth conditions.

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