Determination of free amino compounds in betalainic fruits and vegetables by gas chromatography with flame ionization and mass spectrometric detection

Amino acids and amines are the precursors of betalains. Therefore, the profiles of free amino compounds in juices obtained from cactus pears [Opuntia ficus-indica (L.) Mill. cv. Bianca, cv. Gialla, and cv. Rossa], pitaya fruits [Selenicereus megalanthus (K. Schumann ex Vaupel) Moran, Hylocereus polyrhizus (Weber) Britton & Rose, and Hylocereus undatus (Haworth) Britton & Rose], and in extracts from differently colored Swiss chard [Beta vulgaris L. ssp. cicla (L.) Alef. cv. Bright Lights] petioles and red and yellow beets (B. vulgaris L. ssp. vulgaris var. conditiva Alef. cv. Burpee's Golden) were investigated for the first time. Amino compounds were derivatized with propyl chloroformate. While gas chromatography (GC) with mass spectrometry was used for peak assignment, GC flame ionization detection was applied for quantification of individual compounds. Whereas proline was the major free amino compound of cactus pear and pitaya fruit juices, glutamine dominated in Swiss chard stems and beets, respectively. Interestingly, extremely high concentrations of dopamine were detected in Swiss chard stems and beets. Furthermore, the cleavage of betaxanthins caused by derivatization in alkaline reaction solutions is demonstrated for the first time. Amino acids and amines thus released might increase the actual free amino compound contents of the respective sample. To evaluate the contribution of betaxanthin cleavage to total amino acid and amine concentration, isolated betaxanthins were derivatized according to the "EZ:faast" method prior to quantification of the respective amino compounds released. On a molar basis, betaxanthin contribution to overall amino compound contents was always below 6.4%.     

Evaluating multifunctionality and adaptive capacity of mountain forest management alternatives under climate change in the Eastern Alps

European Journal of Forest Research - Future provisioning of ecosystem services (ES) from mountain forests is uncertain due to potential impacts of climate change. For a case study catchment in the...     

Mycorrhizal fungi mitigate nitrogen losses of an experimental grassland by facilitating plant uptake and soil microbial immobilization

Nitrogen (N) is one of the most limited nutrients of terrestrial ecosystems, whose losses are prevented in tightly coupled cycles in finely tuned systems. Global change-induced N enrichment through atmospheric deposition and application of vast amounts of fertilizer are now challenging the terrestrial N cycle. Arbuscular mycorrhizal fungi (AMF) are known drivers of plant-soil nutrient fluxes, but a comprehensive assessment of AMF involvement in N cycling under global change is still lacking. Here, we simulated N enrichment by fertilization (low/high) in experimental grassland microcosms under greenhouse conditions in the presence or absence of AMF and continuously monitored different N pathways over nine months. We found that high N enrichment by fertilization decreased the relative abundance of legumes and the plant species dominating the plant community changed from grasses to forbs in the presence of AMF, based on aboveground biomass. The presence of AMF always maintained plant N:phosphorus (P) ratios between 14 and 16, no matter how the soil N availability changed. Shifts in plant N:P ratios due to the increased plant N and P uptake might thus be a primary pathway of AMF altering plant community composition. Furthermore, we constructed a comprehensive picture of AMF’s role in N cycling, highlighting that AMF reduced N losses primarily by mitigating N leaching, while N₂O emissions played a marginal role. Arbuscular mycorrhizal fungi reduced N₂O emissions directly through the promotion of N₂O-consuming denitrifiers. The underlying mechanism for reducing N leaching is mainly the AMF-mediated improved nutrient uptake and AMF-associated microbial immobilization. Our results indicate that synergies between AMF and other soil microorganisms cannot be ignored in N cycling and that the integral role of AMF in N cycling terrestrial ecosystems can buffer the upcoming global changes.     

Bovine herpesvirus 5 BICP0 complements the bovine herpesvirus 1 homolog

Bovine herpesvirus 1 (BoHV-1) and BoHV-5 are closely related (82% amino acid identity) but differ strongly in neuropathogenesis. The immediate-early gene for BICP0 is less conserved (70% amino acid identity) and may contribute to a dissimilar phenotype. A peculiar difference is a guanosine hexamer in the BICP0-1 gene which aligns with only five guanosines in the BICP0-5 gene and therefore results in a frameshift in the latter open reading frame. Thus, the C-terminal amino acid sequence (residues 643–676 of BICP0-1 vs. 655–720 of BICP0-5) is completely different. We introduced the BICP0-5 frameshift into the BoHV-1 genome cloned as a bacterial artificial chromosome (BoHV-1 BAC) using the Red recombination system with galK selection and counterselection. Transfection of MDBK cells with the resulting BAC produced recombinant virus that replicated like wild type BoHV-1 in vitro. Attempts to exchange the entire BICP0-1 gene by the BoHV-5 homolog using the same approach failed repeatedly. Therefore, we cotransfected purified BICP0⁻/galK⁺-BoHV-1 BAC DNA with a recombination plasmid coding for BICP0-5 with or without a HA tag into MDBK cells. BoHV-1 recombinants expressing the respective proteins were characterized. In vitro, all recombinants grew to similar titers as the parental viruses, which demonstrates that BICP0-5 compensates for the growth defect of BICP0⁻/galK⁺-BoHV-1 and functionally complements BICP0-1 of BoHV-1. We conclude that BICP0 may be suitable to positively select BoHV-1 recombinants with deletions or insertions of additional genes of interest.     

Quantitative assessment of the fungal contribution to microbial tissue in soil

The fungi-to-bacteria ratio in soil ecological concepts and its application to explain the effects of land use changes have gained increasing attention over the past decade. Four different main approaches for quantifying the fungal and bacterial contribution to microbial tissue can be distinguished: (1) microscopic methods, (2) selective inhibition, (3) specific cell membrane components and (4) specific cell wall components. In this review, the different methods were compared and we hypothesized that all these approaches result in similar values for the fungal and bacterial contribution to total microbial biomass, activity, and residues (dead microbial tissue) if these methods are evenly reliable for the estimation of fungal biomass. The fungal contribution to the microbial biomass or respiration varied widely between 2 and 95% in different data sets published over the past three decades. However, the majority of the literature data indicated that fungi dominated microbial biomass, respiration or non-biomass microbial residues, with mean percentages obtained by the different methodological approaches varying between 35 and 76% in different soil groups, i.e. arable, grassland, and forest soils and litter layers. Microscopic methods generally gave the lowest average values, especially in arable and grasslands soils. Very low ratios in fungal biomass C-to-ergosterol obtained by microscopic methods suggest a severe underestimation of fungal biomass by certain stains. Relatively consistent ratios of ergosterol to linoleic acid (18:2ω6,9) indicate that both cell membrane components are useful indicators for saprotrophic and ectomycorrhizal fungi. More quantitative information on the PLFA content of soil bacteria and the 16:1ω5 content of arbuscular mycorrhizal fungi is urgently required to fully exploit the great potential of PLFA measurements. The most consistent results have been obtained from the analysis of fungal glucosamine and bacterial muramic acid in microbial residues. Component-specific δ¹³C analyses of PLFA and amino sugars are a promising prospect for the near future.     

Studies on the aroma of five fresh tomato cultivars and the precursors of cis- and trans-4,5-epoxy-(E)-2-decenals and methional

Three tasty (BR-139, FA-624, and FA-612) and two less tasty (R-144 and R-175) fresh greenhouse tomato cultivars, which significantly differ in their flavor profiles, were screened for potent odorants using aroma extract dilution analysis (AEDA). On the basis of AEDA results, 19 volatiles were selected for quantification in those 5 cultivars using gas chromatography-mass spectrometry (GC-MS). Compounds such as 1-penten-3-one, ( E, E)- and ( E, Z)-2,4-decadienal, and 4-hydroxy-2,5-dimethyl-3(2 H)-furanone (Furaneol) had higher odor units in the more preferred cultivars, whereas methional, phenylacetaldehyde, 2-phenylethanol, or 2-isobutylthiazole had higher odor units in the less preferred cultivars. Simulation of the odor of the selected tomato cultivars by preparation of aroma models and comparison with the corresponding real samples confirmed that all important fresh tomato odorants were identified, that their concentrations were determined correctly in all five cultivars, and that differences in concentration, especially of the compounds mentioned above, make it possible to distinguish between them and are responsible for the differential preference. To help elucidate formation pathways of key odorants, labeled precursors were added to tomatoes. Biogenesis of cis- and trans-4,5-epoxy-( E)-2-decenals from linoleic acid and methional from methionine was confirmed.     

Highly characteristic and individual specific telomere length patterns in cattle

A combined primed in situ labelling (PRINS)/4',6-diamino-2-phenylindole (DAPI)/propidium iodide (PI)-fluorescence-banding method was used to characterise telomeres, identify their specific chromosomes and visualise neighbouring heterochromatin in 25 artificial insemination (AI) bulls. A highly heterogeneous telomere length pattern was found in cattle. Each bull possessed his own characteristic, specific telomere length pattern.     

Remaining questions in the case for balanced harvesting

Balanced harvesting – harvesting all species and sizes in an ecosystem in proportion to their productivity – is a fisheries management strategy that has been suggested recently to increase yields, while reducing overall ecosystem impact. However, some aspects of balanced harvesting are controversial, including its call for extensive harvesting of juveniles and forage fish. Balanced harvesting also calls for targeting species and size‐classes that are not currently marketable, possibly at a significant economic cost. Some have argued that this cost is outweighed by the ecological benefits of maintaining the ecosystem size and trophic structures and by the benefits of extra yield for food security. There is broad consensus that balanced harvesting would require major changes to fishery management institutions and consumer behaviour, and it is unclear to what extent it is physically possible with current technologies. For this reason, we argue that steps to implement balanced harvesting are difficult to justify until the case for it is more clearly resolved. We outline some of the pivotal questions that must be answered to make a convincing case for or against balanced harvesting, many of which can be answered empirically. In identifying these questions, we hope to offer a constructive path forward in resolving some of the key issues in the balanced harvesting debate.     

Plant availability of magnesium and phosphorus from struvite with concurrent nitrification inhibitor application

Struvite (MgNH₄PO₄.6H₂O) and nitrification inhibitors are applied to soils to, respectively, provide nutrients and reduce nitrogen (N) loss. Given its low N composition (5.7%) relative to that of phosphorus (P, 12.6%) and magnesium (Mg, 9.9%), struvite could be added to soil concurrently with N fertilizers as a source of P and Mg. Nutrient release from struvite could be impacted if nitrification of its ammonium component is reduced by a nitrification inhibitor. Accordingly, a pot trial gauged whether struvite‐fertilized ryegrass had comparable Mg or P uptake and shoot yields with treatments receiving conventional Mg and P fertilizers. Struvite precipitated from milk industry wastewater, or conventional fertilizers, were added to a soil–sand mixture of low fertility. The inhibitor dicyandiamide (DCD) was added to assess its effect on P uptake by ryegrass. Relative to Epsom salt, struvite led to increased Mg uptake without significantly affecting shoot biomass, indicating luxury consumption. Regarding shoot yield and P uptake, struvite was as effective as triple super phosphate. DCD significantly reduced P uptake in the first harvest; the inhibited nitrification of the ammonium is surmised to have diminished struvite dissolution. In later harvests, DCD led to a trend (albeit not statistically significant) of increased biomass; this N‐rich (66% N) compound was probably biodegraded and utilized as an N source. The impact of DCD on P uptake in this experiment was short‐lived. Nevertheless, DCD degradation occurs less rapidly in field conditions, potentially affecting early P supply which is vital for optimum yield.     

Distribution and genetic characterization of porcine Campylobacter coli isolates

The aim of this study was to evaluate the impact of the slaughter process on the Campylobacter (C.) coli prevalence on pig carcasses and finally pork. To detect C. spp., faecal samples, organ samples and surfaces of slaughter pigs were sampled. Additionally, various abattoir surfaces (n=208) and 227 pork and minced meat samples were included in our study.Whereas a high C. spp. prevalence (64.0%) was detectable in the faeces of slaughter pigs (all isolates were identified as C. coli), low detection rates were observed on pig carcasses after the slaughter process before the chilling period (21.1%).The impact of chilling reduced the detection rate of C spp. on pig carcasses even further to 0.8%. Only C. jejuni strains were isolated after the chilling process. Chilling and the associated drying of the skin are responsible for that massive reduction of C. spp prevalence. Significantly more C. spp. were isolated from livers compared to the corresponding carcasses. Only 5 out of 208 swab samples from different surfaces of the abattoir were C. coli positive. Bacteriological investigation could not detect any C. spp. strains from pork and minced pork meat.The low detection rates at the end of the slaughter and processing line indicate that pork may only play a minor role in the transmission of C. coli infections to humans. By genotyping C. coli-isolates from selected animals we were able to demonstrate three possible ways of contamination of the slaughter carcass surface. Genetically highly related strains were detectable on carcass surfaces of consecutively slaughtered animals. Faecal isolates and isolates from the carcass surface showed occasional high similarities. C. coli-genotypes from tonsils and genotypes from the corresponding slaughter carcasses formed a close cluster.