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.     

Current models broadly neglect specific needs of biodiversity conservation in protected areas under climate change

Background  

Protected areas are the most common and important instrument for the conservation of biological diversity and are called for under the United Nations' Convention on Biological Diversity. Growing human population densities, intensified land-use, invasive species and increasing habitat fragmentation threaten ecosystems worldwide and protected areas are often the only refuge for endangered species. Climate change is posing an additional threat that may also impact ecosystems currently under protection. Therefore, it is of crucial importance to include the potential impact of climate change when designing future nature conservation strategies and implementing protected area management. This approach would go beyond reactive crisis management and, by necessity, would include anticipatory risk assessments. One avenue for doing so is being provided by simulation models that take advantage of the increase in computing capacity and performance that has occurred over the last two decades.     

Response of vascular epiphyte diversity to different land-use intensities in a neotropical montane wet forest

Although vascular epiphytes contribute substantially to the biodiversity of tropical montane forests, it is unclear how their diversity and community composition is affected by forest alteration. We studied the response of vascular epiphyte assemblages to different intensities of land-use in a montane wet forest of northeastern Ecuador: (1) unmanaged mature forest; (2) mature forest with mid- and understorey opened for cattle grazing; and (3) isolated remnant trees in cattle pastures. The numbers of individuals and species of epiphytes per host tree did not differ significantly between land-use types, neither did total epiphyte species richness (n = 30 trees). However, total species richness of pteridophytes was significantly lower on isolated remnant trees compared to unmanaged forest, whereas several taxa rich in xerotolerant species (Bromeliaceae, Orchidaceae, Piperaceae) exhibited the opposite trend. An analysis of floristic composition using ordination (NMS) and randomisation techniques (MRPP) showed that epiphyte assemblages on isolated remnant trees were significantly distinct from unmanaged forest while managed forest was intermediate between those two vegetation types. Ordination analysis further indicated reduced floristic heterogeneity in disturbed habitats. These results suggest considerable, rapid species turnover since land-use change 6 years prior to study, with pteridophytes being replaced by more xerotolerant taxa. We attribute this floristic turnover primarily to changes in microclimate towards higher levels of light and desiccation stress associated with forest disturbance. Our results support the notion that community composition offers a more sensitive indicator of human disturbance than species richness.     

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.     

Spatio-temporal dynamics of bacterial communities associated with two plant species differing in organic acid secretion: A one-year microcosm study on lupin and wheat

Plants are generally assumed to influence the surrounding soil microflora through rhizodeposition. However, the role of rhizodeposits, and especially organic acids, in structuring the bacterial communities is still poorly understood. In this study, we asked the question whether plants differing in organic acid secretion have a different impact on the soil bacterial communities, and if this is the case, to which extent this impact is due to different organic acid concentrations in the rhizosphere. To investigate this question, we compared white lupin and wheat. The former is a high organic acid-secreting species, while the latter secretes only low amounts of carboxylates. We grew the plants in large microcosms including root-free control compartments for one year (replanted every second month) and analyzed the spatio-temporal changes in soil ATP concentrations, as well as in diversity and structure of bacterial communities (using DNA- and RNA-based DGGE) along a root-soil gradient after two, six and twelve month's cultivation. Our results showed: i) that white lupin and wheat differed in their impact on soil ATP concentrations and on the structure of root bacterial communities; ii) that cultivation time was a key factor in explaining the observed differences in all the parameters studied; and iii) that the amounts of organic acids accounted for a significant proportion (15%) of the variability within root active communities. These results indicate that plants influence their associated bacterial communities in a species-specific way and that for communities living in the direct vicinity of roots (rhizoplane-endorhizosphere), a significant part of this influence can be attributed to root-secreted organic acids.     

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.