Vitamin D mushrooms: comparison of the composition of button mushrooms (Agaricus bisporus) treated postharvest with UVB light or sunlight

This study compared the compositional changes in mushrooms exposed to sunlight with those occurring after commercial ultraviolet (UV) light processing. Button mushrooms (75 kg) were processed in the presence or absence of UVB light; a third group was exposed to direct sunlight. Mushroom composition was evaluated using chemical analyses. Vitamin D concentrations were 5, 410, and 374 μg/100 g (dw) in control, UVB, and sunlight groups, respectively. On a dry weight basis, no significant changes in vitamin C, folate, vitamins B(6), vitamin B(5), riboflavin, niacin, amino acids, fatty acids, ergosterol, or agaritine were observed following UVB processing. Sunlight exposure resulted in a 26% loss of riboflavin, evidence of folate oxidation, and unexplained increases in ergosterol (9.5%). It was concluded that compositional effects of UVB light are limited to changes in vitamin D and show no detrimental changes relative to natural sunlight exposure and, therefore, provide important information relevant to the suitability and safety of UVB light technology for vitamin D enhanced mushrooms.     

Determination and isolation of a thioesterase from passion fruit (Passiflora edulis Sims) that hydrolyzes volatile thioesters

Volatile organosulfur compounds (VOSCs) are high impact aroma chemicals characteristic of tropical fruits which are active as both free thiols and the respective thioesters. Using a simple and sensitive colorimetric enzyme assay, a thioesterase activity toward VOSCs has been identified in ripening purple passion fruit ( Passiflora edulis Sims). The assay was based on determining the release of free thiols from 2-methyl-3-furanthiol acetate using Ellman's reagent. The major thioesterase in the fruit was found to be a wall-bound protein in the mesocarp. The extracted enzyme activity was purified 150-fold and shown to be associated with a 43 kDa monomeric serine hydrolase which was selectively labeled with a fluorophosphonate suicide probe. MS-MS sequencing identified the thioesterase as a class 13 glycoside hydrolase, most similar to pectin acetylesterase, an enzyme involved in cell wall modifications in the peel of a number of fruit. Our results suggest that cell wall hydrolases in tropical fruit may have additional useful roles in biotransforming VOSCs.     

Starving the soil of plant inputs for 50 years reduces abundance but not diversity of soil bacterial communities

If soil communities rely on plant-derived carbon, is biodiversity lost when this primary source is removed? Soil microbial and mesofaunal communities at the Rothamsted Highfield site were compared under a mixed grass sward, arable rotation and a section maintained as a bare-fallow for the past 50 years by regular tillage. Organic matter reserves have been degraded and microbial and mesofaunal numbers and mite diversity have declined in this unique bare-fallow site, where fresh carbon inputs have been drastically reduced. However, it supports a species-rich metabolically active bacterial community of similar diversity to that in soil maintained as grass sward. Thus in contrast to soil mesofauna, bacterial diversity (but not abundance) is apparently independent of plant inputs.     

Distributions of soil phosphorus in China’s densely populated village landscapes

Purpose  

Village landscapes, which integrate small-scale agriculture with housing, forestry and a host of other land use practices, cover more than 2 × 10⁶ km² across China. Village lands tend to be managed at very fine spatial scales (≤30 m), with managers altering soil fertility and even terrain by terracing, irrigation, fertilizing, and other land use practices. Under these conditions, accumulation of excess phosphorous in soils has become important contributor to eutrophication of surface waters across China’s densely populated village landscapes. The aim of this study was to investigate relationships between fine-scale patterns of agricultural management and soil total phosphorus (STP) within China’s village landscapes.     

Norsesquiterpene glycosides in bracken ferns (Pteridium esculentum and Pteridium aquilinum subsp. wightianum) from Eastern Australia: reassessed poisoning risk to animals

Austral bracken Pteridium esculentum contains three unstable norsesquiterpene glycosides: ptaquiloside, ptesculentoside, and caudatoside, in variable proportions. The concentration of each of the glycosides was determined in this study as their respective degradation products, pterosin B, pterosin G and pterosin A, by HPLC-UV analysis. Samples of P. esculentum collected from six sites in eastern Australia contained up to 17 mg of total glycoside/g DW, with both ptaquiloside and ptesculentoside present as major components accompanied by smaller amounts of caudatoside. Ratios of ptaquiloside to ptesculentoside varied from 1:3 to 4:3, but in all Australian samples ptesculentoside was a significant component. This profile differed substantially from that of P. esculentum from New Zealand, which contained only small amounts of both ptesculentoside and caudatoside, with ptaquiloside as the dominant component. A similar profile with ptaquiloside as the dominant glycoside was obtained for Pteridium aquilinum subsp. wightianum (previously P. revolutum ) from northern Queensland and also P. aquilinum from European sources. Ptesculentoside has chemical reactivity similar to that of ptaquiloside and presumably biological activity similar to that of this potent carcinogen. The presence of this additional reactive glycoside in Australian P. esculentum implies greater toxicity for consuming animals than previously estimated from ptaquiloside content alone.     

Evaluation of spectrophotometric and HPLC methods for shikimic acid determination in plants: models in glyphosate-resistant and -susceptible crops

Endogenous shikimic acid determinations are routinely used to assess the efficacy of glyphosate in plants. Numerous analytical methods exist in the public domain for the detection of shikimic acid, yet the most commonly cited comprise spectrophotometric and high-pressure liquid chromatography (HPLC) methods. This paper compares an HPLC and two spectrophotometric methods (Spec 1 and Spec 2) and assesses the effectiveness in the detection of shikimic acid in the tissues of glyphosate-treated plants. Furthermore, the study evaluates the versatility of two acid-based shikimic acid extraction methods and assesses the longevity of plant extract samples under different storage conditions. Finally, Spec 1 and Spec 2 are further characterized with respect to (1) the capacity to discern between shikimic acid and chemically related alicyclic hydroxy acids, (2) the stability of the chromophore (t1/2), (3) the detection limits, and (4) the cost and simplicity of undertaking the analytical procedure. Overall, spectrophotometric methods were more cost-effective and simpler to execute yet provided a narrower detection limit compared to HPLC. All three methods were specific to shikimic acid and detected the compound in the tissues of glyphosate-susceptible crops, increasing exponentially in concentration within 24 h of glyphosate application and plateauing at approximately 72 h. Spec 1 estimated more shikimic acid in identical plant extract samples compared to Spec 2 and, likewise, HPLC detection was more effective than spectrophotometric determinations. Given the unprecedented global adoption of glyphosate-resistant crops and concomitant use of glyphosate, an effective and accurate assessment of glyphosate efficacy is important. Endogenous shikimic acid determinations are instrumental in corroborating the efficacy of glyphosate and therefore have numerous applications in herbicide research and related areas of science as well as resolving many commercial issues as a consequence of glyphosate utilization.     

Changes in soil chemistry associated with the establishment of forest gardens on eroded,acidified grassland soils in Sri Lanka

Topsoil properties were determined in forest gardens established about 20 years ago on eroded grassland soils (abandoned tea lands) in the wet zone of the Sri Lankan highlands. They were compared with adjacent, eroded grasslands (abandoned tea lands) on strongly weathered soils vs soils at earlier stages of pedogenic development in a two-way analysis of variance. Soil pH in forest gardens was, on average, 6.1, nearly one unit higher than in the adjacent grasslands. In the garden soils, the cation exchange capacity (CEC measured at pH 4.8) was nearly double, exchangeable calcium concentrations five times and exchangeable magnesium three times as high as in the grasslands soils. Total soil N content was found to be nearly 40% higher in the gardens. Topsoil gravel contents in the gardens were less than half as high as in the grasslands. The increases in exchangeable bases and N in gardens, relative to grasslands, were attributed to increased nutrient retention and acquisition. Higher retention was partly due to the higher CEC_pH4.8, and probably to reduced erosion and increased, continuous fine root density in the garden topsoils. Higher field CEC in gardens was likely to result from generally higher C contents and from the reversal of acidification, presumably caused by base accumulation and decomposition processes. Our results suggest that forest garden establishment on degraded grasslands can lead to accumulation of mobile nutrients in the topsoil, probably due to increased nutrient retention, subsoil uptake and litter input exceeding nutrient uptake by the standing biomass.     

Improved isolation procedure for azaspiracids from shellfish, structural elucidation of azaspiracid-6, and stability studies

Azaspiracids are a group of lipophilic polyether toxins produced by the small dinoflagellate Azadinium spinosum. They may accumulate in shellfish and can result in illnesses when consumed by humans. Research into analytical methods, chemistry, metabolism, and toxicology of azaspiracids has been severely constrained by the scarcity of high-purity azaspiracids. Consequently, since their discovery in 1995, considerable efforts have been made to develop methods for the isolation of azaspiracids in sufficient amounts and purities for toxicological studies, in addition to the preparation of standard reference materials. A seven-step procedure was improved for the isolation of azaspiracids-1-3 (1, 2, and 3) increasing recoveries 2-fold as compared to previous methods and leading to isolation of sufficiently purified azaspiracid-6 (6) for structural determination by NMR spectroscopy. The procedure, which involved a series of partitioning and column chromatography steps, was performed on 500 g of Mytilus edulis hepatopancreas tissue containing ~14 mg of 1. Overall yields of 1 (52%), 2 (43%), 3 (43%), and 6 (38%) were good, and purities were confirmed by NMR spectroscopy. The structure of 6 was determined by one- and two-dimensional NMR spectroscopy and mass spectrometry. The stability of 6 relative to 1 was also assessed in three solvents in a short-term study that demonstrated the greatest stability in aqueous acetonitrile.     

Survival of bacterial DNA and culturable bacteria in archived soils from the Rothamsted Broadbalk experiment

Dried soil samples from many sources have been stored in archives world-wide over the years, but there has been little research on their value for studying microbial populations. Samples collected since 1843 from the Broadbalk field experiment on crop nutrition at Rothamsted have been used to document changes in the structure and composition of soils as agricultural practices evolve, also offering an invaluable record of environmental changes from the pre- to post-industrial era in the UK. To date, the microbial communities of these soils have not been studied, in part due to the well-documented drop in bacterial culturability in dried soils. However, modern molecular methods based on PCR amplification of DNA extracted directly from soil do not require bacterial cells to be viable or intact and may allow investigations into the legacy of bacteria that were present at the time of sample collection.

In a preliminary study, to establish if dried soils can provide a historical record of bacterial communities, samples from the Broadbalk soil archive dating back to 1868 were investigated and plots treated with either farmyard manure (FYM) or inorganic fertilizer (NPK) were compared. As anticipated, the processes of air-drying and milling greatly reduced bacterial viability whilst DNA yields declined less and may be preserved by desiccation. A higher proportion of culturable bacteria survived the archiving process in the FYM soil, possibly protected by the increased soil organic matter. The majority of surviving bacteria were firmicutes, whether collected in 2003 or in 1914, but a wide range of genera was detected in DNA extracted from the samples using PCR and DGGE of 16S rRNA genes. Analysis of DGGE band profiles indicated that the two plots maintained divergent populations. Sequence analysis of bands excised from DGGE gels, from a sample collected in 1914, revealed DNA from - and β-proteobacteria as well as firmicutes. PCR using primers specific for ammonia oxidizing bacteria showed similar band profiles across the two treatments in recently collected samples, however older samples from the NPK plot showed greater divergence. Primers specific for the genus Pseudomonas were designed and used in real-time quantitative PCR to indicate that archived soil collected in 1868 contained 10-fold less pseudomonad DNA than fresh soil, representing around 10⁵ genomes g⁻¹ soil. Prior to milling, dramatically less pseudomonad DNA was extracted from recently collected air-dried soil from the NPK compared to the FYM plot; otherwise, the two plots followed similar trends. Overall bacterial abundance, diversity and survival during the archiving process differed in the two soils, possibly due to differences in clay and soil organic matter content. Nevertheless, the results demonstrate that air-dried soils can protect microbial DNA for more than 150 years and offer an invaluable resource for future research.     

Correlated responses to neonicotinoid insecticides in clones of the peach-potato aphid, Myzus persicae (Hemiptera: Aphididae)

BACKGROUND: Although there are still no confirmed reports of strong resistance to neonicotinoid insecticides in aphids, the peach-potato aphid (Myzus persicae Sulzer) shows variation in response, with some clones exhibiting up to tenfold resistance to imidacloprid. Five clones varying in response to imidacloprid were tested with four other neonicotinoid molecules to investigate the extent of cross-resistance.RESULTS: All four compounds-thiamethoxam, thiacloprid, clothianidin and dinotefuran-were cross-resisted, with ED(50) values ranked in the same order as for imidacloprid. Resistance factors ranged up to 11 for imidacloprid, 18 for thiamethoxam, 13 for thiacloprid, 100 for clothianidin and 6 for dinotefuran.CONCLUSION: This variation in response does not appear to be sufficient to compromise the field performance of neonicotinoids aimed at controlling aphids. However, it highlights the need for careful vigilance and stewardship in all M. persicae populations, and a need to consider neonicotinoids as a single cross-resisted group for management purposes.