The effectiveness of flower strips and hedgerows on pest control,pollination services and crop yield: a quantitative synthesis

Floral plantings are promoted to foster ecological intensification of agriculture through provisioning of ecosystem services. However, a comprehensive assessment of the effectiveness of different floral plantings, their characteristics and consequences for crop yield is lacking. Here we quantified the impacts of flower strips and hedgerows on pest control (18 studies) and pollination services (17 studies) in adjacent crops in North America, Europe and New Zealand. Flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average. However, effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively. These findings provide promising pathways to optimise floral plantings to more effectively contribute to ecosystem service delivery and ecological intensification of agriculture in the future.     

Breeding density and population of little auks (Alle alle) in a Northwest Greenland colony

The little auk population of the Thule district in Greenland is generally believed to be the largest anywhere and to comprise more than half of the world population, although published numbers have largely been conjectural. In 1996/1997 we estimated breeding density of little auks at Hakluyt Island in this district by colour-marking a number of birds in three study plots and subsequently counting marked and unmarked birds present in the plots. The density estimate considered most representative of the colony was 1.8 birds/m² or 0.73 pairs/m² (±7%). From surveys of the inhabitated area of the scree slopes, this density implies a total little auk population for the island of 130,000 pairs. An extrapolation to the entire Thule district suggests a population in the area of at least 15 million pairs, which is in general agreement with previously published assumptions. Accepted: 3 January 2000     

Risk of inter-river transmission of Gyrodactylus salaris by migrating Atlantic salmon smolts, estimated by Monte Carlo simulation

The possibility of Gyrodactylus salaris infection of wild North Atlantic salmon Salmo salar spreading to new rivers poses a major threat in Norway. This freshwater parasite can survive for some time in brackish water, and it has been suggested that smolts leaving infected rivers could transport vital parasites to new rivers. A Monte Carlo simulation model was used to estimate the risk that infected smolts would ascend a new river. Data from an infected watercourse in Norway, where the salmon population is maintained constant by cultivation, were used. The model included information on prevalence of infection, hydrographical conditions, survival of G. salaris in brackish water, fish population characteristics, and smolt behaviour during seaward migration. The annual risk was estimated for 3 neighbouring rivers situated at different distances from the index river. For the nearest river, which shares the same brackish water zone with the index river, the model estimated an annual risk of 31% that at least 1 infected smolt would ascend this river. The results of the simulation were highly sensitive to the water salinity along the migration route. For the other rivers, the annual risk was lower than 0.5%. Risk was positively correlated with the number of fish leaving the index river, indicating control of this number as a possible tool in risk management.     

Synthesis of 4'-O-acetyl-maltose and alpha-D-galactopyranosyl-(1-->4)-D-glucopyranose for biochemical studies of amylose biosynthesis

The chemical synthesis of the title compounds as maltose analogs, in which the non-reducing end is modified by acetylation of the 4'-OH group or by reversing its configuration, is reported. For synthesis of the 4'-O-acetylated analog, beta-maltose was converted into its per-O-benzylated-4',6'-O-benzylidene derivative followed by removal of the benzylidene acetal function and selective silylation at C-6'. Acetylation at C-4' of the obtained silylated compound followed by removal of the benzyl ether protecting groups and subsequent desilylation afforded the desired analog. The other maltose analog was synthesized via the glycosidation reaction between the glycosyl donor, O-(2,3,4,6-tetra-O-benzyl-alpha/beta-D-galactopyranosyl)trichloroacetimidate and the glycosyl acceptor, phenyl 2,3,6-tri-O-benzyl-1-thio-beta-D-glucopyranoside followed by removal of the phenylthio group and debenzylation to provide the desired analog.     

The RihA, RihB, and RihC ribonucleoside hydrolases of Escherichia coli. Substrate specificity, gene expression, and regulation

Pyrimidine-requiring cdd mutants of Escherichia coli deficient in cytidine deaminase utilize cytidine as a pyrimidine source by an alternative pathway. This has been presumed to involve phosphorylation of cytidine to CMP by cytidine/uridine kinase and subsequent hydrolysis of CMP to cytosine and ribose 5-phosphate by a putative CMP hydrolase. Here we show that cytidine, in cdd strains, is converted directly to cytosine and ribose by a ribonucleoside hydrolase encoded by the previously uncharacterized gene ybeK, which we have renamed rihA. The RihA enzyme is homologous to the products of two unlinked genes, yeiK and yaaF, which have been renamed rihB and rihC, respectively. The RihB enzyme was shown to be a pyrimidine-specific ribonucleoside hydrolase like RihA, whereas RihC hydrolyzed both pyrimidine and purine ribonucleosides. The physiological function of the ribonucleoside hydrolases in wild-type E. coli strains is enigmatic, as their activities are paralleled by the phosphorolytic activities of the nucleoside phosphorylases, and a triple mutant lacking all three hydrolytic activities grew normally. Furthermore, enzyme assays and lacZ gene fusion analysis indicated that rihB was essentially silent unless activated by mutation, whereas rihA and rihC were poorly expressed in glucose medium due to catabolite repression.     

Physiological and haematological consequences of a novel parasite on the red-rumped swallow Hirundo daurica

Parasite virulence has been hypothesised to increase with the degree of host sociality because highly social hosts have a greater probability of encountering horizontal transmission of parasites and experiencing infections with multiple strains of the same parasites than do solitary hosts. As compared with the defences of closely related social host species, we predicted that solitary hosts should have relatively weak defences against parasites, thus being relatively more affected when parasitised by a novel parasite. We tested this prediction by either experimentally infesting 12 nests of the solitarily nesting red-rumped swallow Hirundo daurica with 50 individuals of the generalist martin bug Oeciacus hirundinis or by fumigation of nine nests. Nestlings 13 days old from the parasite addition group experienced increased mortality, attained lower body mass and tended to have shorter tarsi compared to nestlings from fumigated nests. Surprisingly, nestlings from the parasite addition group had higher packed cell volume (cellular fraction of blood) and lower levels of heat shock proteins (HSP60) than nestlings from the fumigation group. A measure of immunocompetence was not significantly affected by treatment, but its magnitude was positively related to packed cell volume and negatively related to level of HSP60. Solitary hosts like the red-rumped swallow have weak immune responses and low levels of heat shock proteins when infested with ectoparasites while highly social hosts have strong immune responses and high levels of heat shock proteins when infested. These findings partially support the hypothesis that potential host species with weak defences are more susceptible to infection and the deleterious effects of evolving parasites than potential hosts with strong defences.     

Analysis of the PilQ secretin from Neisseria meningitidis by transmission electron microscopy reveals a dodecameric quaternary structure

PilQ is a member of the secretin family of outer membrane proteins and is specifically involved in secretion of type IV pili in Neisseria meningitidis, Neisseria gonorrhoeae, and Pseudomonas aeruginosa. The quaternary structure of PilQ from N. meningitidis was analyzed by transmission electron microscopy by using a negative stain. Single particle averaging was carried out with a total data set of 650 individual particles, which produced a projection map generated from 296 particles at an estimated resolution of 2.6 nm. Oligomeric PilQ adopts a donut-like structure with an external ring that is 16.5 nm in diameter surrounding a central cavity that is 6.5 nm in diameter. Self-rotation and power spectrum analysis demonstrated the presence of 12-fold rotational symmetry, showing that PilQ is organized as a ring of 12 identical subunits. A model of the type IV meningococcal pilus fiber, based on the X-ray crystal structure of the N. gonorrhoeae pilin subunit, fitted neatly into the cavity, demonstrating how PilQ could serve as a channel for the growing pilus fiber.     

GSA11 encodes a unique 208-kDa protein required for pexophagy and autophagy in Pichia pastoris

Cells are capable of adapting to changes in their environment by synthesizing needed proteins and degrading superfluous ones. Pichia pastoris synthesizes peroxisomal enzymes to grow in methanol medium. Upon adapting from methanol medium to one containing glucose, this yeast rapidly and selectively degrades peroxisomes by an autophagic process referred to as pexophagy. In this study, we have utilized a novel approach to identify genes required for this degradative pathway. Our approach involves the random integration of a vector containing the Zeocin resistance gene into the yeast genome by restriction enzyme-mediated integration. Cells unable to degrade peroxisomes during glucose adaptation were isolated, and the genes that were disrupted by the insertion of the vector were determined by sequencing. By using this approach, we have identified a number of genes required for glucose-induced selective autophagy of peroxisomes (GSA genes). We report here the characterization of Gsa11, a unique 208-kDa protein. We found that this protein is required for glucose-induced pexophagy and starvation-induced autophagy. Gsa11 is a cytosolic protein that becomes associated with one or more structures situated near the vacuole during glucose adaptation. The punctate localization of Gsa11 was not observed in gsa10, gsa12, gsa14, and gsa19 mutants. We have previously shown that Gsa9 appears to relocate from a compartment at the vacuole surface to regions between the vacuole and the peroxisomes being sequestered. In the gsa11 mutants, the vacuole only partially surrounded the peroxisomes, but Gsa9 was still distributed around the peroxisome cluster. This suggests that Gsa9 binds to the peroxisomes independent of the vacuole. The data also indicate that Gsa11 is not necessary for Gsa9 to interact with peroxisomes but acts at an intermediate event required for the vacuole to engulf the peroxisomes.     

Continuous recording of long-chain acyl-coenzyme a synthetase activity using fluorescently labeled bovine serum albumin

The fluorescence-based long-chain fatty acid probe BSA-HCA (bovine serum albumin labeled with 7-hydroxycoumarin-4-acetic acid) is shown to respond to binding of long-chain acyl-CoA thioesters by quenching of the 450 nm fluorescence emission. As determined by spectrofluorometric titration, binding affinities for palmitoyl-, stearoyl-, and oleoyl-CoA (Kd = 0.2-0.4 microM) are 5-10 times lower than those for the corresponding nonesterified fatty acids. In the presence of detergent (Chaps, Triton X-100, n-octylglucoside) above the critical micelle concentration, acyl-CoA partitions from BSA-HCA and into the detergent micelles. This allows BSA-HCA to be used as a fluorescent probe for continuous recording of fatty acid concentrations in detergent solution with little interference from acyl-CoA. Using a calibration of the fluorescence signal with fatty acids in the C14 to C20 chain-length range, fatty acid consumption by Pseudomonas fragi and rat liver microsomal acyl-CoA synthetase activities are measured down to 0.05 microM/min with a data sampling rate of 10 points per second. This new method provides a very promising spectrofluorometric approach to the study of acyl-CoA synthetase reaction kinetics at physiologically relevant (nM) aqueous phase concentrations of fatty acid substrates and at a time resolution that cannot be obtained in isotopic sampling or enzyme-coupled assays.     

Liposomes as sustained release system for human interferon-gamma: biopharmaceutical aspects

Interferon-gamma (IFNgamma) has proven to be a promising adjuvant in vaccines against cancer and infectious diseases. However, due to its rapid biodegradation and clearance, its efficacy is severely reduced. Liposomal association might prolong the residence time of IFNgamma, but no efforts have been made to optimize the biopharmaceutical characteristics of liposomal IFNgamma for its application in therapy or as vaccine immunoadjuvant. In the present study, various liposomal formulations of recombinant human IFNgamma (hIFNgamma), differing in lipid composition, were prepared via the film hydration method and characterized in vitro regarding association efficiency and bioactivity, and in vivo regarding cytokine release kinetics after subcutaneous (s.c.) administration into mice. Human IFNgamma can be formulated in large, multilamellar liposomes with high association efficiency (>80%) and preservation of bioactivity. A critical parameter is the inclusion of negatively charged phospholipids to obtain a high liposome association efficiency, which is dominated by electrostatic interactions. The fraction of externally adsorbed protein compared to the total associated protein can be minimized from 74+/-9% to 8+/-3% by increasing the ionic strength of the dispersion medium. After injection of free (125)I-hIFNgamma, the radiolabel was detectable up to 48 h at the injection site. Liposomal encapsulation of (125)I-hIFNgamma increased the local area under the curve 4-fold, and the presence of the radiolabeled hIFNgamma at the injection site was prolonged to 7 days. The release kinetics and overall residence time of the cytokine at the s.c. administration site was influenced by depletion of the externally adsorbed IFNgamma, reducing the initial burst release. Increasing the rigidity of the liposome bilayer also resulted in a more pronounced reduction of the burst release and a 19-fold increase in the residence time of the protein at the s.c. administration site, compared to the free cytokine. As adjuvanticity of liposomal IFNgamma may strongly depend on the release kinetics of cytokines in vivo, the findings in this paper may contribute to a rational design of liposomal-cytokine adjuvants in vaccines against cancer and infectious diseases.