Prevalence of Escherichia coli associated with a cabbage crop inadvertently irrigated with partially treated sewage wastewater

Preharvest contamination of field crops may have many sources, including feces, soil, and irrigation water. In March 2000, a sewage spill released unchlorinated tertiary-treated effluent into a creek used to irrigate commercial produce. A field of young cabbage transplants was irrigated with creek water as the contaminated water flowed past this land. Cabbage samples were taken from plots within this field, and Escherichia coli was isolated from the roots of these plants but not from the edible portion of the cabbage. No E. coli was isolated from water samples or from control samples taken from a nearby cabbage field watered with chlorinated municipal water. The cabbage field under study had not been fertilized with manure for at least 2 years prior to the contamination incident. Six different E. coli serotypes were identified, although none of them proved to be pathogenic. These serotypes were separated into five groups by a RiboPrinter; the resulting groups correlated well with the serotypes and the locations in the field from which these strains were isolated. We previously found that certain nonpathogenic E. coli strains displayed lower levels of adherence to lettuce seedling roots in a hydroponic adherence assay. The E. coli field strains displayed variable patterns of adherence to lettuce seedlings: strain MW421 showed significantly lower root and shoot adherence levels than did the other field strains, while strains MW423 and MW425 showed significantly higher root and shoot adherence levels. These data suggest that water quality is of paramount importance for the food safety of growing crops.     

Docking onto chromatin via the Saccharomyces cerevisiae Rad9 Tudor domain

An integrated cellular response to DNA damage is essential for the maintenance of genome integrity. Recently, post-translational modifications to histone proteins have been implicated in DNA damage responses involving the Rad9 family of checkpoint proteins. In budding yeast, methylation of histone H3 on lysine 79 (H3-K79me) has been shown to be required for efficient checkpoint signalling and Rad9 localization on chromatin. Here, we have used a rad9 Tudor mutant allele and cells mutated for Dot1, the H3-K79 methylase, to analyse the epistatic relationship between RAD9 and DOT1 genes regarding the DNA damage resistance and checkpoint activation pathways. Our results show that RAD9 is epistatic to DOT1 and suggest that it acts downstream of the Dot1 methylase in the damage resistance and checkpoint response. We have also found that the Tudor domain of Rad9 is necessary for in vitro binding to H3-K79me as well as Rad9 focal accumulation in response to DNA damage in vivo. In summary, our study demonstrates that the interaction between Rad9, via its Tudor domain, and methylated H3-K79 is required at two different steps of the DNA damage response, an early step corresponding to checkpoint activation, and a late step corresponding to DNA repair. The study further shows that the function of this interaction is cell cycle-regulated; the role in checkpoint activation is restricted to the G(1) phase and its role in DNA repair is restricted to G(2).     

Low‐field NMR: A tool for studying protein aggregation

Low‐field nuclear magnetic resonance (NMR) spin–spin relaxation (T₂) measurements were used to study the denaturation and aggregation of β‐lactoglobulin (β‐LG) solutions of varying concentrations (1–80 g L^?1) as they were heated at temperatures ranging from ambient up to 90 °C. For concentrations of 1–10 g L^?1, the T₂ of β‐LG solutions did not change, even after heating to 90 °C. A decrease in T₂ was only observed when solutions having higher concentrations (20–80 g L^?1) were heated. Circular dichroism (CD) spectroscopy and fluorescence tests using the dye 1‐anilino‐8‐naphthalene sulfonate (ANS) on 0.2 and 1 g L^?1 solutions, respectively, indicated there were changes in the protein's secondary and tertiary conformations when the β‐LG solutions reached 70 °C and above. In addition, dynamic light scattering (DLS) showed that protein aggregation occurred only at concentrations above 10 g L^?1 and for heating at 70 °C and above. The hydrodynamic radius increased as T₂ decreased. When excess 2‐mercaptoethanol was added, the changes in both T₂ and the hydrodynamic radius followed the same trend for all β‐LG protein concentrations between 1 and 40 g L^?1. These observations led to the conclusion that the changes in T₂ were due to protein aggregation, not protein unfolding. Copyright © 2007 Society of Chemical Industry     

Arsenic removal with iron(II) and iron(III) in waters with high silicate and phosphate concentrations

Arsenic removal by passive treatment, in which naturally present Fe(II) is oxidized by aeration and the forming iron(III) (hydr)oxides precipitate with adsorbed arsenic, is the simplest conceivable water treatment option. However, competing anions and low iron concentrations often require additional iron. Application of Fe(II) instead of the usually applied Fe(III) is shown to be advantageous, as oxidation of Fe(II) by dissolved oxygen causes partial oxidation of As(III) and iron(III) (hydr)oxides formed from Fe(II) have higher sorption capacities. In simulated groundwater (8.2 mM HCO3(-), 2.5 mM Ca2+, 1.6 mM Mg2+, 30 mg/L Si, 3 mg/L P, 500 ppb As(III), or As(V), pH 7.0 +/- 0.1), addition of Fe(II) clearly leads to better As removal than Fe(III). Multiple additions of Fe(II) further improved the removal of As(II). A competitive coprecipitation model that considers As(III) oxidation explains the observed results and allows the estimation of arsenic removal under different conditions. Lowering 500 microg/L As(III) to below 50 microg/L As(tot) in filtered water required > 80 mg/L Fe(III), 50-55 mg/L Fe(II) in one single addition, and 20-25 mg/L in multiple additions. With As(V), 10-12 mg/L Fe(II) and 15-18 mg/L Fe(III) was required. In the absence of Si and P, removal efficiencies for Fe(II) and Fe(III) were similar: 30-40 mg/L was required for As(II), and 2.0-2.5 mg/L was required for As(V). In a field study with 22 tubewells in Bangladesh, passive treatment efficiently removed phosphate, but iron contents were generally too low for efficient arsenic removal.     

Determination of ergosterol in paddy rice using solid phase extraction

Ergosterol, the predominant sterol found in most fungi, is considered as an indicator of fungal invasion in grain. An extraction method based on solid phase extraction (SPE) has been developed for determination of ergosterol in unmilled rice, generally called paddy. The samples obtained by extraction through SPE have been analysed by HPLC. The method has been validated in experiments with paddy subjected to different drying treatments and recoveries above 85% have been obtained. SPE appeared to be simple, quick, reliable and consistent for ergosterol analysis. The ergosterol levels obtained in the paddy samples were found to be within the expected range and were comparable with those found using conventional methods. Copyright © 2004 Society of Chemical Industry     

Species identification by genotyping and determination of antibiotic resistance in Campylobacter jejuni and Campylobacter coli from humans and chickens in Sweden

Campylobacter is today the most common cause of human bacterial enteritis in Sweden, as well as in most other industrialized countries. Common sources of infection are undercooked chicken meat, unpasteurized milk and contaminated drinking water. One aim with our present study was to identify the species Campylobacter jejuni and Campylobacter coli strains from humans and chickens using a polymerase chain reaction/restriction enzyme analysis (PCR/REA) method, as well as traditional hippurate hydrolysis test. Another aim was to investigate the antibiotic resistance pattern of the human domestic C. jejuni/C. coli isolates from infected patients and isolates from healthy Swedish chicken, as well as isolates from humans infected abroad. If discrimination between C. jejuni and C. coli was based on testing for hippurate hydrolysis, 95% of the human domestic strains and 88% of the chicken strains were identified as C. jejuni. Based on genotyping by PCR/REA, 100% of the human domestic strains and 98% of the chicken strains were attributed to C. jejuni. The E-test and disc diffusion methods were used for phenotypic antibiotic resistance studies. The two methods gave similar results. Most Swedish C. jejuni/C. coli isolates both from humans and chickens were sensitive to doxycycline and erythromycin, which are antibiotics used to treat human infection. Only 7% of the human domestic strains and 2% of the chicken strains were resistant to the quinolones tested. As a comparison, more than 94% of strains isolated from travelers to Asia and southern Europe showed antibiotic resistance to one or more drugs.     

Use of survival analysis and Classification and Regression Trees to model the growth/no growth boundary of spoilage yeasts as affected by alcohol, pH, sucrose, sorbate and temperature

This paper describes the application of a survival analysis model and a Classification and Regression Trees (CART) model to a data set comprising times to growth of a yeast cocktail inoculated into media simulating a fruit-based or alcoholic food or drink, and covering over 900 combinations of five environmental factors (alcohol, pH, sucrose, sorbate and temperature). Growth was determined as either the time to growth within a 150-day time period or as no-growth after 150 days. Models were developed which could either predict the likelihood of growth occurring within the 150 day period, or the time to grow, either in days or in one of three categories chosen to represent a rapid (1-14 days), medium (15-30 days) or slow (31-150 days) growth response. Growth was observed in 29% of the experimental conditions and demonstrated that the yeasts used were able to grow under extreme environmental conditions, for example at a pH value of 2.1, a temperature of 2 degrees C, a sucrose concentration of 55% (w/w) or an alcohol concentration of 12% (w/v). Generally, both models provided a reasonable fit to the data, and successfully predicted the growth class in 84% of cases. Direct comparisons of the models were made to determine the more suitable for predicting the growth of yeasts in food systems. The survival analysis model was preferred for this data set because it was more fail-safe than the CART model. In food validation studies, the survival model generally gave reliable predictions of time to growth in a range of 23 different food and drink products and is considered to be a reliable model to predict the likelihood and speed of yeast spoilage for a range of fruit-based or alcoholic food or drinks.     

Kinetics and mechanism of photoactivated periodate reaction with 4-chlorophenol in acidic solution

The application of photoactivated periodate (UV/IO4-) to the degradation of 4-chlorophenol (4-CP) was explored in this study. Under low irradiation intensities (23 microW/cm2), wavelength of 266 nm, and pH 3, 4-CP was observed to degrade by pseudo-first-order reaction kinetics. The small reduction in 4-CP degradation in the presence of tert-butyl alcohol (t-BuOH) suggests that degradation of 4-CP by UV/IO4- was not dominated by an OH* pathway. O3 production was suppressed in the presence of t-BuOH under O2-limited environments and in the presence of 4-CP. Faster degradation of 4-CP in the presence of an OH* scavenger under nitrogen purging as compared to air-saturated conditions indicates that O(3P) is an important reactive species with 4-CP in this system. When 4-CP is added to the system, IO3- production is enhanced. On the basis of the elimination of potential reaction pathways, O(3P) and IO3* are suspected reactive species with 4-CP in this system.     

The oxidative stability of omega-3 oil-in-water nanoemulsion systems suitable for functional food enrichment: A systematic review of the literature

There is growing demand for functional food products enriched with long chain omega-3 polyunsaturated fatty acids (LCω3PUFA). Nanoemulsions, systems with extremely small droplet sizes have been shown to increase LCω3PUFA bioavailability. However, nanoemulsion creation and processing methods may impact on the oxidative stability of these systems. The present systematic review collates information from studies that evaluated the oxidative stability of LCω3PUFA nanoemulsions suitable for use in functional foods. The systematic search identified seventeen articles published during the last 10 years. Researchers used a range of surfactants and antioxidants to create systems which were evaluated from 7 to 100 days of storage.

Nanoemulsions were created using synthetic and natural emulsifiers, with natural sources offering equivalent or increased oxidative stability compared to synthetic sources, which is useful as consumers are demanding natural, cleaner label food products. Equivalent vegetarian sources of LCω3PUFA found in fish oils such as algal oils are promising as they provide direct sources without the need for conversion in the human metabolic pathway. Quillaja saponin is a promising natural emulsifier that can produce nanoemulsion systems with equivalent/increased oxidative stability in comparison to other emulsifiers. Further studies to evaluate the oxidative stability of quillaja saponin nanoemulsions combined with algal sources of LCω3PUFA are warranted.     

Anti-listerial activity of a polymeric film coated with hybrid coatings doped with Enterocin 416K1 for use as bioactive food packaging

In this study, Enterocin 416K1, a bacteriocin produced by Enterococcus casseliflavus IM 416K1, was entrapped in an organic-inorganic hybrid coating applied to a LDPE (low-density polyethylene) film for its potential use in the active food packaging field. The antibacterial activity of the coated film was evaluated against Listeria monocytogenes NCTC 10888 by qualitative modified agar diffusion assay, quantitative determination in listeria saline solution suspension and direct contact with artificially contaminated food samples (frankfurters and fresh cheeses) stored at room and refrigeration temperatures. All investigations demonstrated that enterocin-activated coatings have a good anti-listeria activity. Qualitative tests showed a clear zone of inhibition in the indicator lawn in contact with and around the coated film. During the quantitative antibacterial evaluation the L. monocytogenes viable counts decreased to 1.5 log units compared to the control. The inhibitory capability was confirmed also in food-contact assays. In all food samples packed with coated films we observed a significant decrease in L. monocytogenes viable counts in the first 24 h compared to the control. This difference was generally maintained up to the seventh day and then decreased, with the exception of the cheese samples stored at refrigeration temperature.