ABSTRACIThe amount of indole-3-acetic acid (IAA) was measured in peach fruits by gas chromatography-mass spectrometry-selective ion monitoring using an isotope dilution assay with I"CC6IIAA as an internal standard throughout the growing season. Ethylene evolution of the fruit was also measured. IAA levels were 25 nanograms per gram fresh weight, 18 enous IAA concentration and observed ethylene evolution were correlated, given that auxin can promote ethylene evolution (14). MATERIALS AND METHODSPlant Material. Developing fruits of Prunus persica cv Redhaven were obtained from the University of Maryland Research Farm, Silver Spring, MD. Beginning from 18 to 88 d after anthesis fruits were harvested from around the entire periphery of the tree once or twice a week for IAA and ethylene, respectively. The abscission of unpollinated flowers was completed by d 18. At 88 d after anthesis, fruits were mature, firm-ripe, and capable of softening to full-ripe within 72 h of harvest. Uniform, upright fruiting shoots of about 60 cm length at 1.8 m height were harvested at 8:00 AM and their cut bases were immediately placed in water. One shoot was cut from each of 60 trees on each sampling date. Thirty min were needed to harvest and transport the fruit to the laboratory. The fruits were removed from their shoots immediately after transport and extraction begun.To minimize fruit-to-fruit variability only basal fruits were used for analyses. Fruits displaying visible signs of senescence, disease, or insect damage were not used. On each sampling date a minimum of 10 individual peach fruits were taken for ethylene determinations. An additional 2 replicates of a minimum of 10 pooled fruits were simultaneously extracted and assayed for endogenous levels of free IAA. In addition to the above, 8 to 10 peach ovules were excised from fruits on 60, 67, 81, and 88 d postanthesis. A single replicate of pooled ovules was extracted and endogenous free IAA levels determined on each date. This sampling protocol was used to avoid potential artifacts of frozen material and allow maximum frequency of sampling time. This latter aspect was important because our primary interest was in examining trends during development.Extraction and Measurement of Free IAA. A minimum of 10 whole fruits were added to cold (-20'C) acetone; tissue:acetone ratio 3:7 (w:v). To this mixture was added 50 to 100,000 dpm of '4C-(methylene)-IAA (59 or 51.6 mCi/mmol, Amersham containing 1.2 to 23.1 ng 12C-IAA per extract) and an estimated a 10-fold greater amount of '3C6-(benzene ring)-IAA (5.05-101 sg per extract) than the amount of free IAA in the fruit (4). Thus, the '3C6-IAA served as both an internal standard and as a carrier in order to increase sample recovery. The tissues were homogenized for 2 min and allowed to equilibrate overnight at 4°C. The crude extract was filtered, and the residue washed with 70% acetone. Acetone extracts were combined and concentrated to the aqueous phase in vacuo at 45°C. The aqueous phase was chilled to 4°C, adjusted to pH 7.0, and pa...

BackgroundTomato (Solanum lycopersicum) consumption has been one of the most common causes of produce-associated salmonellosis in the United States. Contamination may originate from animal waste, insects, soil or water. Current guidelines for fresh tomato production recommend the use of potable water for applications coming in direct contact with the fruit, but due to high demand, water from other sources is frequently used. We sought to describe the overall bacterial diversity on the surface of tomato fruit and the effect of two different water sources (ground and surface water) when used for direct crop applications by generating a 454-pyrosequencing 16S rRNA dataset of these different environments. This study represents the first in depth characterization of bacterial communities in the tomato fruit surface and the water sources commonly used in commercial vegetable production.ResultsThe two water sources tested had a significantly different bacterial composition. Proteobacteria was predominant in groundwater samples, whereas in the significantly more diverse surface water, abundant phyla also included Firmicutes, Actinobacteria and Verrucomicrobia. The fruit surface bacterial communities on tomatoes sprayed with both water sources could not be differentiated using various statistical methods. Both fruit surface environments had a high representation of Gammaproteobacteria, and within this class the genera Pantoea and Enterobacter were the most abundant.ConclusionsDespite the major differences observed in the bacterial composition of ground and surface water, the season long use of these very different water sources did not have a significant impact on the bacterial composition of the tomato fruit surface. This study has provided the first next-generation sequencing database describing the bacterial communities living in the fruit surface of a tomato crop under two different spray water regimes, and therefore represents an important step forward towards the development of science-based metrics for Good Agricultural Practices.

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Health professionals involved in endoscopy, intubation, bronchoscopy, or similar invasive procedures using benzocaine-containing sprays should know that (1) administration may cause MHb with potentially serious consequences, (2) identifying the reaction to benzocaine usually requires cooximetry (although it can be implied by symptoms), and (3) treatment involves immediate intravenous administration of 1 to 2 mg/kg of methylene blue.

Bacterial communities associated with the phyllosphere of apple trees (Malus domestica cv. Enterprise) grown under organic and conventional management were assessed to determine if increased biological food safety risks might be linked with the bacterial communities associated with either treatment. Libraries of 16S rRNA genes were generated from phyllosphere DNA extracted from a wash made from the surfaces of leaves and apples from replicated organic and conventional treatments. 16S rRNA gene libraries were analyzed with software designed to identify statistically significant differences between bacterial communities as well as shared and unique phylotypes. The identified diversity spanned eight bacterial phyla and 14 classes in the pooled organic and conventional libraries. Significant differences between organic and conventional communities were observed at four of six time points (P < 0.05). Despite the identification of significantly diverse microfloras associated with organic and conventional treatments, no detectable differences in the presence of potential enteric pathogens could be associated with either organic or conventional management. Neither of the bacterial genera most commonly associated with produce-related illness outbreaks (Salmonella and Escherichia) was observed in any of the libraries. The impressive bacterial diversity that was documented in this study provides a valuable contribution to our developing understanding of the total microbial ecology associated with the preharvest phyllospheres of food crops. The fact that organic and conventional phyllosphere bacterial communities were significantly different at numerous time points suggests that crop management methods may influence the bacterial consortia associated with the surfaces of fruits and vegetables.

Due to the intimate association between plants and their microbial symbionts, an examination of the influence of agricultural practices on phytobiome structure and diversity could foster a more comprehensive understanding of plant health and produce safety. Indeed, the impact of upstream crop producti006Fn practices cannot be overstated in their role in assuring an abundant and safe food supply. To assess whether fertilizer type impacted rhizosphere and phyllosphere bacterial communities associating with tomato plants, the bacterial microbiome of tomato cv. 'BHN602' grown in soils amended with fresh poultry litter, commercially available sterilized poultry litter pellets, vermicompost or synthetic fertilizer was described. Culture independent DNA was extracted from bulk and rhizosphere soils, and washes of tomato blossoms and ripe fruit. PCR amplicons of hypervariable regions of the 16S rRNA gene were sequenced and profiled using the QIIME pipeline. Bulk and rhizosphere soil, and blossom and fruit surfaces all supported distinct bacterial communities according to principal coordinate analysis and ANOSIM (R=0.87, p=0.001 in year 1; R=0.93, p=0.001 in year 2). Use of microbiologically diverse organic fertilizers generally did not influence bacterial diversity, community structure or relative abundance of specific taxa on any plant organ surface. However, statistically significant differences in sand and silt contents of soil (p<0.05) across the field and corresponding shifts in water activity were positively (R=0.52, p=0.005) and negatively (R=0.48, p=0.009) correlated with changes in bacterial community structure in the rhizosphere, respectively. Over two harvest seasons, this study demonstrated that the application of raw poultry manure, poultry litter pellets and vermicompost had little effect on the tomato microbiome in the rhizosphere and phyllosphere, when compared to synthetically fertilized plants. Plant anatomy, and other factors related to field location, possibly associated with edaphic and air characteristics, were more influential drivers of different tomato organ microbiomes than were diverse soil amendment applications.

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Small-and medium-size farms in the mid-Atlantic region of the United States use varied agricultural practices to produce leafy greens during spring and fall, but the impact of preharvest practices on food safety risk remains unclear. To assess farm-level risk factors, bacterial indicators, Salmonella enterica, and Shiga toxin-producing Escherichia coli (STEC) from 32 organic and conventional farms were analyzed. A total of 577 leafy greens, irrigation water, compost, field soil, and pond sediment samples were collected. Salmonella was recovered from 2.2% of leafy greens (n ‫؍‬ 369) and 7.7% of sediment (n ‫؍‬ 13) samples. There was an association between Salmonella recovery and growing season (fall versus spring) (P ‫؍‬ 0.006) but not farming system (organic or conventional) (P ‫؍‬ 0.920) or region (P ‫؍‬ 0.991). No STEC was isolated. In all, 10% of samples were positive for E. coli: 6% of leafy greens, 18% of irrigation water, 10% of soil, 38% of sediment, and 27% of compost samples. Farming system was not a significant factor for levels of E. coli or aerobic mesophiles on leafy greens but was a significant factor for total coliforms (TC) (P < 0.001), with higher counts from organic farm samples. Growing season was a factor for aerobic mesophiles on leafy greens (P ‫؍‬ 0.004), with higher levels in fall than in spring. Water source was a factor for all indicator bacteria (P < 0.001), and end-of-line groundwater had marginally higher TC counts than source samples (P ‫؍‬ 0.059). Overall, the data suggest that seasonal events, weather conditions, and proximity of compost piles might be important factors contributing to microbial contamination on farms growing leafy greens. Increased awareness of the nutritional and economic benefits of eating fresh produce has caused global consumption to increase 4.5% from 1990 to 2004 (1), but field-grown foods such as vegetables and leafy greens (including lettuce, spinach, spring mix, and kale) can also serve as reservoirs of microorganisms, including bacteria, molds, and yeasts. Most of these microorganisms are not harmful and are part of the background microflora of the plant. However, human-pathogenic bacteria such as Salmonella, Listeria monocytogenes, Shigella spp., and Escherichia coli O157:H7 have been associated with foodborne outbreaks involving fresh produce (2). The ability of foodborne pathogens to colonize and persist as part of the plant microbiome as endophytes or epiphytes (reviewed in reference 3) represents a significant food safety risk, as fresh produce is often consumed raw without any processing "kill step."In the United States, estimates calculate approximately 4.9 million yearly incidents of food-related illnesses attributed to plant commodities, with leafy vegetables comprising 22.3% of these (4). Following the E. coli O157:H7 multistate outbreak in fall 2006, which was attributed to spinach (5), leafy greens have received significant attention from government, industry, and academic researchers. Other incidents have implicated leafy greens as a vehicl...