Recovery of soil microbial community structure after fire in a sagebrush‐grassland ecosystem

Recovery of the soil microbial community after fire in a sagebrush‐grassland ecosystem was examined using a chronosequence of four sites ranging in time since fire from 3–39 years. The successional stage communities examined included Recent Burn (3 years since fire, ysf), Establishment (7 ysf), Expansion (21 ysf), and Mature (39 ysf). Aboveground standing plant biomass increased with time since disturbance to the Mature stage where sagebrush became dominant over herbaceous species. Phospholipid fatty acid (PLFA) analysis was used to characterize the microbial community structure. Soil microbial community productivity generally appeared to be similar to the Mature site soil (39 ysf) within 7 years of fire. Diversity of PLFAs detected in soils, at both depths, increased from a low value of 29 at the Recent site to a high of 37 at the Establishment site and then decreased again to 31 at the Mature stage site. Canonical variates analysis indicated important disparities in microbial community structure at the four sites. Greatest disparities were observed in microbial community structure between the Recent and Establishment stages but greater similarity between the Recent stage and the sagebrush dominated Mature stage. This study emphasizes both short‐term and long‐term changes in the belowground community and suggests that soil microbial communities are highly resilient to disturbances after prescribed fire. Copyright © 2010 John Wiley & Sons, Ltd.     

Incorporation of metal bioavailability into regulatory frameworks—metal exposure in water and sediment

Background, aim, and scope  

The cause for this position paper is the impression that risk assessors consider primarily the concentration of free metal ions dissolved in solution controlling metal bioavailability in aquatic systems. Aiming at a more realistic risk assessment of metals, bioavailability has to be discussed under the scope of main uptake routes of metals to organisms.     

A Modeling Approach to Water Quality Management of an Agriculturally Dominated Watershed, Kansas, USA

Impairment of water quality is a major concern for streams and rivers in the central USA. Total maximum daily loads (TMDLs) establish a watershed framework and set management targets to alleviate pollution from both point and nonpoint sources. For this study, we have used a hydrologic modeling approach to holistically examine the effect of land use management, urban development, and agricultural practices on sediment and nutrient loadings in an agricultural watershed. Annualized Agricultural Nonpoint Source (AnnAGNPS) simulation indicates that while point source dischargers contribute 8% of total nitrogen (TN) and 24% of total phosphorus (TP) loadings to the Marmaton River, agricultural nonpoint sources are the leading pollution source contributing 55% of TN and 49% of TP loading. Based on TMDL analysis and model simulation, 3% of the watershed area (3,244 ha) needs to be targeted to control TN loading whereas 1% of the total area (1,319 ha) is required for TP reduction management. Managing the TN areas alone can achieve a 57% reduction in the TP load required for the TMDL, whereas managing the targeted TP areas can only provide 30% of the required TN reduction. Areas required both TN and TP management comprise 469 ha. Targeting these areas can achieve approximately 22% of the required TN reduction and 29% of the required TP reduction. Overall, 4,094 ha will require management to achieve water quality goals. This study demonstrates that a modeling approach is needed to effectively address TMDL issues and help identify targeted areas for management.     

Synthesis of methylphosphonic acid by marine microbes: a source for methane in the aerobic ocean

Relative to the atmosphere, much of the aerobic ocean is supersaturated with methane; however, the source of this important greenhouse gas remains enigmatic. Catabolism of methylphosphonic acid by phosphorus-starved marine microbes, with concomitant release of methane, has been suggested to explain this phenomenon, yet methylphosphonate is not a known natural product, nor has it been detected in natural systems. Further, its synthesis from known natural products would require unknown biochemistry. Here we show that the marine archaeon Nitrosopumilus maritimus encodes a pathway for methylphosphonate biosynthesis and that it produces cell-associated methylphosphonate esters. The abundance of a key gene in this pathway in metagenomic data sets suggests that methylphosphonate biosynthesis is relatively common in marine microbes, providing a plausible explanation for the methane paradox.     

Dermatophagoides farinae house dust mite allergen challenges reduce stratum corneum ceramides in an experimental dog model of acute atopic dermatitis

Background – Ceramides are essential stratum corneum (SC) lipids and they play a pivotal role in maintaining effective cutaneous barrier function. Objectives – The present study aimed at determining the effect of a Dermatophagoides farinae house dust mite (Df‐HDM) allergen challenge on SC ceramides of atopic dogs experimentally sensitized to these allergens. Animals – Six Df‐HDM‐sensitized atopic Maltese–beagle dogs were used. Methods – Prechallenge SC was obtained by cyanoacrylate stripping. One week later, the dogs were challenged topically with Df‐HDM allergens, which resulted in mild to moderate inflammation 24 h later. Two weeks after challenge, SC of lesional and nonlesional skin was obtained. Finally, SC was collected from challenge sites 2 months after lesion resolution. The different SC lipids were quantified blindly by thin‐layer chromatography. Results – Significantly lower amounts of ceramides [AH], [AP], [AS], [NP], [EOP], [NS] and [EOS] were observed in lesional SC compared with prechallenge samples, while no significant effect was found on the amount of other lipids, including cholesterol and free fatty acids. The ceramide profile of nonlesional skin generally showed the same postchallenge reduction pattern. Ceramide amounts returned to normal within 2 months after lesion remission. Conclusion and clinical importance – These findings suggest that the allergic reactions caused by Df‐HDM allergens lead to a selective reduction of SC ceramides, not only at sites of inflammation but also at sites away from those of allergen application. There is normalization of ceramide amounts after inflammation subsides. These observations suggest that the deficiency of ceramides observed in canine atopic skin occurs, at least in part, secondary to inflammation.     

Effect of diet on the deposition of n-3 fatty acids, conjugated linoleic and C18:1trans fatty acid isomers in muscle lipids of German Holstein bulls

This study examined the effects of feeding diets rich in either n-3 or n-6 polyunsaturated fatty acids (PUFA) on the fatty acid composition of longissimus muscle in beef bulls. Thirty-three German Holstein bulls were randomly allocated to either an indoor concentrate system or periods of pasture feeding (160 days) followed by a finishing period on a concentrate containing linseed to enhance the contents of n-3 PUFA and conjugated linoleic acids (CLA) in beef muscle. The relative proportion and concentration (mg/100 g fresh muscle) of n-3 fatty acids in the phospholipid and triglyceride fractions were significantly increased (p < or = 0.05) in muscle lipids of pasture-fed bulls. The pasture feeding affected the distribution of individual CLA isomers in the muscle lipids. The proportion of the most prominent isomer, CLA cis-9,trans-11, was decreased from 73.5 to 65.0% of total CLA in bulls fed on concentrate as compared to pasture. The second most abundant CLA isomers were CLA trans-7,cis-9 and CLA trans-11,cis-13 in bulls fed on concentrate and pasture, respectively. Diet had no effect on the concentration of C18:1 trans-11. In contrast, the concentration of the C18:1 trans-13/14, trans-15, and trans-16 isomers in the muscle lipids was up to two times higher in pasture-fed as compared to concentrate-fed bulls. Pasture feeding enhanced the concentration of n-3 fatty acids, but the diet had no effect on the concentration of CLA cis-9,trans-11.     

Ein neues Thermo-Mikro-Verfahren zur Schnellabtrennung Flüchtiger Stoffe aus Drogen und Nahrungsmitteln (TAS-Verfahren)

Zusammenfassung Es werden ein neues, zeitsparendes Thermomikro-, Abtrenn- und Auftrageverfahren (TAS-Verfahren) sowie die Apparatur und ihre Handhabung beschrieben. In 1/2 bis 2 Minuten kann man hiermit aus 5–50 mg Proben die flüchtigen Stoffe bei 200–250° direkt auf eine DC-Platte transferieren. Zusammenfassend wird dann über die bisherigen Anwendungsmöglichkeiten berichtet. Neben den Drogen mit ätherischen Ölen sind Cumarine, Xanthinderivate, manche Alkaloide und Säuren, Scharfstoffe wie z.B. Capsaicin, Piperin u.a. aber auch Diphenyl-Derivate, PHB-Ester, Pestizide und viele andere Verbindungen auf diesem Wege einfach und schnell abtrennbar.

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A new time-saving thermomicro separation and application technique (TAS procedure) has been described, together with the apparatus and its use. With this technique it is possible to transfer, at 50–350°, volatilizable materials from 5–50 mg samples directly onto a thin-layer chromatographic plate. A survey of applications of the technique is also given. The technique offers a simple and rapid means for the separation of drugs containing essential oils, of coumarins, xanthine derivatives, some alkaloids and acids, spices such as capsaicin and piperin, and also of diphenylderivatives, 4-Hydroxybenzoate-esters, pesticides and many other compounds.

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Résumé On propose une méthode nouvelle et rapide pour extraction, transfer et dépôt à l'aide d'un microfour TAS. Ce four permet de traiter des échantillons de 5–50 mg entre 50 et 350°; les substances volatilisables peuvent ainsi être déposées sur une plaque chromatographique en moins d'une à deux minutes.Il est donné ensuite un aperçu sur les principales applications faites jusqu'ici. Bénéficient de la méthode: les huiles essentielles, les coumarines et dérivés xanthiques, certains alcaloïdes et acides, certains topiques tels que capsicine, pipérine, etc; il en est de même pour les dérivés diphénylés, les esteres de l'acide 4-hydroxy-benzoique, les pesticides et de nombreux autres composés qui peuvent par cette voie être séparés de façon simple et rapide.

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Vortrag gehalten auf der gemeinsamen Tagung der Internationalen Vereinigung zur Erforschung der Qualität von Nahrungspflanzen (CIQ) und der Deutschen Gesellschaft für Qualitätsforschung (Pflanzliche Nahrungsmittel) (DGQ) in Mainz (25.–27. März 1969) am 25.3.1969.