Analysis of gene cassettes of streptomycin-spectinomycin resistance of Hungarian Salmonella enterica serotype Typhimurium strains

By PCR using the ant(3")-Ia primer pair the aadA gene was detected in 34 streptomycin- and spectinomycin-resistant Salmonella enterica serotype Typhimurium strains. Out of them 12 belonged to DT104 and 22 to non-DT104 phage type. Using different primer combinations it was demonstrated that this gene was integron-associated in all cases: in the DT104 strains it was generally contained by a 1 kb integron while in the majority of the non-DT104 strains by a 2.05 kb (less often by a 1.9 or 1 kb) integron. In the case of integrons carrying multiple cassettes the cassette containing the aadA gene was located closer to the 3' end of the integron. The aadA genes of DT104 and non-DT104 strains were different: in the former group the aadA2 gene, while in the latter group (constituted by strains of five different phages types as well as unclassifiable and untypable strains) the aadA1 gene could be identified. The RH50/RH51 primer pair described by Collis and Hall (1992) proved to be suitable for rapid discrimination between the aadA1 and aadA2 genes on the basis that the RH51 primer bound exclusively to the aadA2 gene.     

Predicting moisture content and density distribution of Scots pine by microwave scanning of sawn timber

This study was carried out to investigate the possibility of calibrating a prediction model for the moisture content and density distribution of Scots pine (Pinus sylvestris) using microwave sensors. The material was initially of green moisture content and was thereafter dried in several steps to zero moisture content. At each step, all the pieces were weighed, scanned with a microwave sensor (Satimo 9,4GHz), and computed tomography (CT)-scanned with a medical CT scanner (Siemens Somatom AR.T.). The output variables from the microwave sensor were used as predictors, and CT images that correlated with known moisture content were used as response variables. Multivariate models to predict average moisture content and density were calibrated using the partial least squares (PLS) regression. The models for average moisture content and density were applied at the pixel level, and the distribution was visualized. The results show that it is possible to predict both moisture content distribution and density distribution with high accuracy using microwave sensors.     

Predicting moisture content and density distribution of Scots pine by microwave scanning of sawn timber II: evaluation of models generated on a pixel level

The purpose of this study was to use images from a microwave sensor on a pixel level for simultaneous prediction of moisture content and density of wood. The microwave sensor functions as a line-scan camera with a pixel size of 8mm. Boards of Scots pine (Pinus sylvestris), 25 and 50mm thick, were scanned at three different moisture contents. Dry density and moisture content for each pixel were calculated from measurements with a computed tomography scanner. It was possible to create models for prediction of density on a pixel level. Models for prediction of moisture content had to be based on average values over homogeneous regions. Accuracy will be improved if it is possible to make a classification of knots, heartwood, sapwood, etc., and calibrate different models for different types of wood. The limitations of the sensor used are high noise in amplitude measurements and the restriction to one period for phase measurements.     

Fire-derived charcoal causes loss of forest humus

Fire is a global driver of carbon storage and converts a substantial proportion of plant biomass to black carbon (for example, charcoal), which remains in the soil for thousands of years. Black carbon is therefore often proposed as an important long-term sink of soil carbon. We ran a 10-year experiment in each of three boreal forest stands to show that fire-derived charcoal promotes loss of forest humus and that this is associated with enhancement of microbial activity by charcoal. This result shows that charcoal-induced losses of belowground carbon in forests can partially offset the benefits of charcoal as a long-term carbon sink.     

SOM fractionation methods: Relevance to functional pools and to stabilization mechanisms

Soil organic matter (SOM) consists of various functional pools that are stabilized by specific mechanisms and have certain turnover rates. For the development of mechanistic models that predict changes in SOM storage, these pools have to be quantified and characterized. In the past, numerous fractionation schemes have been developed to separate and analyse such SOM fractions. In this review, the SOM fractions obtained with such operational fractionation procedures are described in terms of their pool sizes, chemical properties, and turnover rates. The main objective of this review is to evaluate these operationally defined fractions with respect to their suitability to describe functional SOM pools that could be used to parameterize SOM turnover models. Fractionation procedures include (1) physical separation of SOM into aggregate, particle size, and density fractions and fractions according to their magnetic susceptibility, and (2) various wet chemical procedures that fractionate SOM according to solubility, hydrolysability, and resistance to oxidation or by destruction of the mineral phase. Furthermore, combinations of fractionation methods are evaluated.The active SOM pool with turnover rates <10 years may best be represented by the soil microbial biomass and the light fraction (<1.6-2 g cm⁻³) obtained by density fractionation (if black carbon contents are considered). Most chemical and physical fractionations as well as combinations of methods yield SOM fractions that are not homogeneous in terms of turnover rates. It has proven to be particularly difficult to isolate functional fractions that represent the passive model pools in which the majority of soil SOM is stabilized. The available fractionation methods do not correspond to specific stabilization mechanisms and hence do not describe functional SOM pools. Another problem is that comprehensive data for turnover rates and data for whole soil profiles are only now becoming available, especially for new fractionation methods. Such information as well as the use of specific markers and compound-specific isotope analysis may be important for future differentiation and evaluation of functional SOM fractions.     

The relationship between local extinctions of grassland butterflies and increased soil nitrogen levels

In contrast to many other western European countries, the knowledge about trends in the Swedish butterfly fauna is poor. We studied the effects of habitat and species characteristics on species turnover in 13 grassland sites in southern Sweden by comparing species richness and compositions at two separate occasions with an interval of 21 years. The mean number of species per site decreased from 30 to 24, with a large variation between sites. The number of extinctions was highest in sites where the proportion of trees and shrubs had increased most, but there was no detectable effect of area or of the composition of landscapes surrounding the sites. Areas protected as nature reserves had lost as many species as unprotected areas had, indicating both the importance of proper management of nature reserves and that nature reserves alone may not be enough to inhibit regional extinction of butterfly species. Species dependent on nutrient-poor conditions tended to decrease while species dependent on nutrient-rich conditions tended to increase, indicating a negative effect of increased soil nitrogen levels resulting from active fertilizing of pastures and/or atmospheric nitrogen deposition. A regular monitoring program could show whether our results are representative for Sweden or Northern Europe.     

Einfluss von konventioneller und biologisch-dynamischer Bewirtschaftungsweise auf die mikrobielle Biomasse und deren Stickstoff-Dynamik in Parabraunerden der Friedberger Wetterau

Effect of conventional and biological farming on microbial biomass and its nitrogen turnover in agriculturally used luvisols of the Friedberg plains The influence of conventional and biological farming on microbial biomass-carbon (Bio-C) and nitrogen (Bio-N) of agriculturally used fields was compared. The fields were located on luvisols of the Friedberg plains and tilled according to each system for many years. Bio-C and Bio-N were measured using the chloroform-fumigation-extraction technique. During early spring and autumn (1990) [Bio-CI% C_org] and Bio-N [%N₁] were slightly lower in sites of conventional farming than on fields tilled by biological farming. During the vegetation period Bio-C and Bio-N increased continuously in both systems. This increase, however was higher on conventional than on biological fields and may be ascribed to a higher C-input (rhizodeposition) and availability of mineral nutrients. In the soils of the biological farming system N-deficiency apparently decreased Bio-N (but not Bio-C) in spring time. Consequently the Bio-C/N-ratio increased. It seems as if plant growth affects the quality of microbes (Bio-C/N). The average turnover-time of Bio-N was about 1 year in all soils. However, the average turnover-time of Bio-C was 1.6 years, being 2 times faster in the conventional than in the biological farming system. It seems as if long-term management practices may affect the amount of labile organic matter by changing the biomass pool and its turnover rate.     

Original study of the biochemical and oil composition of the Cambodia nut Irvingia malayana

Analysis of the biochemical composition of Irvingia malayana was carried out. This Cambodian nut contains 7.5% water and 70% oil. Most of the fatty acids are saturated and include 42% C12:0 and 41.8% C14:0; the sterol composition is similar to that of other vegetable oils. This oil is less rich in alpha-tocopherol than in gamma-tocopherol. Analysis of the solid content of the oil with respect to the temperature by NMR shows a fast fall of solid content around its fusion range at 38-39 degrees C. The main differences in the properties of the indigenous Cambodia nut from other known oleaginous seeds are in its selenium content, fatty acid composition, fusion temperature profile, and content of antioxidants. These important characteristics can soon make possible its application in pharmacology, cosmetics, the margarine industry, etc.     

Virulence, cytotoxic and inflammatory activities of Vibrio anguillarum and Aeromonas salmonicida isolated from cultivated salmonid fish in Sweden

Extracellular products in culture filtrates of Aeromonas salmonicida subsp. achromogenes and Vibrio anguillarum isolated from infected fish have been shown to possess skin inflammatory factor. The extracellular products from Vibrio anguillarum were cytotoxic in HeLa and CHO cells. In addition to the skin lesions, the culture filtrates of V. anguillarum caused necrotic reaction on the rabbit skin. Five of 6 strains of V. anguillarum were lethal to mice after intraperitoneal administration of 3×10⁷ CFU. Only 1 strain of 5 A. salmonicida subsp. achromogenes produced extracellular products which elicited cytotoxic effects in the CHO cells. None of the A. salmonicida subsp. achromogenes strains were lethal to mice. The cytotoxins were inactivated when heated at 65°C for 30 min. The results indicate that the thermolabile exotoxins are non-enterotoxic since they failed to stimulate fluid accumulation in the rabbit ileal loop and did not cause elongation of the CHO cells. The rounding off of CHO cells, as well as of HeLa cells indicate that the exotoxins may play an important role in fish diseases.     

Effects of pressurization on structure, water distribution, and sensory attributes of cured ham: can pressurization reduce the crucial sodium content?

This study investigated the replacement of tumbling (intermittent vacuum tumbling for 6 h) with pressure treatment (7 MPa for 4 s) in the production of a cured ham product with the aim of elucidating if the pressure treatment could reduce the amount of salt added to obtain a satisfactory product. Confocal laser scanning microscopy (CLSM) revealed a pressure-induced loosening of the meat structure, and proton nuclear magnetic resonance (NMR) relaxometry revealed that this structural modification of the meat had an impact on water properties and water distribution in both cooked and cooked/fried products. Three salt levels (0.6, 1.1, and 1.7% w/w) were investigated, and sensory profiling revealed that the pressured-cooked meat obtained a significantly higher juiciness score at low and medium salt levels. In addition, sensory profiling assessments revealed that at the lowest salt concentration the pressured product was perceived to be saltier compared with the tumbled product; however, the difference was not significant and was absent upon frying. In contrast, in sensory time intensity analysis the maximum intensity and the total salt taste were significantly higher in the pressured samples at the low and medium salt levels in the cooked samples. In conclusion, the present study showed strong evidence that the structure and biophysical characteristics of cured ham is altered by pressurization and suggested that pressurization may reduce the critical amount of salt required in a ham product.