Indirect effect of salmon carcasses on growth of a freshwater amphipod, <Emphasis Type="Italic">Jesogammarus jesoensis</Emphasis> (Gammaridea): An experimental study

The effect of salmon carcasses on the growth of a freshwater amphipod, Jesogammarus jesoensis (Schellenberg) (Gammaridea, Anisogammaridae), was examined experimentally. Growth rate was determined by rearing juvenile amphipods in four food treatments (leaves, salmon, leaves and salmon and leaves with salmon leachate) for 20days. Mass loss and oxygen consumption of the leaves were also measured in the three treatments with leaves. The oxygen consumption rate of leaves was lower in the leaves treatment than in either the leaves and salmon or leaves with salmon leachate treatments, indicating that microbial activity on leaves was enhanced by the presence of salmon carcasses. Mass loss of leaves did not differ between the three treatments with leaves. The growth rate of the amphipods did not differ between the leaves and salmon treatments, or between the leaves and salmon and leaves with salmon leachate treatments. Growth rates in the two latter treatments were higher than rates in the leaves treatment, but not higher than the rates in the salmon treatment. Therefore, it appears likely that consuming leaves fertilized with nutrients from salmon carcasses facilitates growth in this amphipod.     

Structural diversity of O-polysaccharides and serological classification of <Emphasis Type="Italic">Pseudomonas syringae</Emphasis> pv. <Emphasis Type="Italic">garcae</Emphasis> and other strains of genomospecies 4

Novel O-serotypes were revealed among Pseudomonas syringae pv. garcae strains by using a set of mouse monoclonal antibodies specific to the lipopolysaccharide O-polysaccharide. Structural studies showed that the O-polysaccharide of P. syringae pv. garcae NCPPB 2708 is a hitherto unknown linear L-rhamnan lacking strict regularity and having two oligosaccharide repeating units I and II, which differ in the position of substitution in one of the rhamnose residues and have the following structures: I:3)--L Rha (12)-- L Rha (12)--L-Rha-(13)--L Rha (1;II: 2)--L-Rha-(13) -L-Rha-(12)--L-Rha-(13)--L Rha (1.The branched O-polysaccharides of P. syringae pv. garcae ICMP 8047 and NCPPB 588^T have the same L-rhamnan backbone with repeating units I and II and a lateral chain of 14)- or 13)-linked residues of 3-acetamido-3,6-dideoxy-D-galactose (D-Fuc3NAc). Several monoclonal antibody epitopes associated with the L-rhamnan backbone or the lateral -D-Fuc3NAc residues were characterized.Translated from Mikrobiologiya, Vol. 73, No. 6, 2004, pp. 777–789.Original Russian Text Copyright © 2004 by Ovod, Zdorovenko, Shashkov, Kocharova, Knirel.     

Sublittoral macrozoobenthic assemblages in the enclosed sediment-polluted Rhine-Meuse Delta; their relationship to environmental conditions

Composition, densities and biomass of sublittoral macrozoobenthos were investigated at 14 sites in the enclosed Rhine-Meuse Delta. The aim was to identify the main macrozoobenthic assemblages and to establish their relationship with environmental conditions, including sediment pollution. Most sites were dominated by the tubificidsLimnodrilus hoffmeisteri andL. claparedeanus. Four zoobenthic assemblages could be identified. They are related to different geomorphological phases of a basin filling up with fluvial sediment causing a longitudinal sediment gradient. The Rhine river assemblage was found in the Nieuwe Merwede, filled up in the 1970's, the soft mud assemblage in the Hollands Diep at sites with high sedimentation rates; the basin silt assemblage in the Amer, Hollands Diep and Haringvliet, at sites with lower sedimentation rates, and the basin shoal assemblage at former flats with low sedimentation rates. CANOCO was used to relate the TWINSPAN indicator species to a selection of environmental parameters. Sediment pH, water content, sand fraction, total polycyclic aromatic hydrocarbons (PAH) and current velocity explained 44% of the variance of the average abundance of the indicator taxa per site. Sediment firmness, indicated by sediment water content, and high ammonium concentrations probably were together responsible for the very low densities in the soft mud assemblage. Densities and biomasses in the other assemblages were low as well, except for theDreissena polymorpha habitat, where very high total zoobenthic biomass values (max. 55.8 g m^–2) were observed. It is argued that sediment contamination has a considerable impact on macrozoobenthic densities and species composition in all assemblages, the basin shoal assemblage excepted.     

Monitoring the mitochondrial transmembrane potential with the JC-1 fluorochrome in programmed cell death during mesophyll leaf senescence

Summary. Analysis of the mitochondrial transmembrane potential (_m) with the help of the JC-1 fluorochrome (5,5,6,6-tetrachloro-1,1,3,3-tetraethylbenzimidazolcarbocyanine iodide) during mesophyll leaf senescence was performed in order to determine whether a reduction of _m takes place during mesophyll senescence and whether plant mitochondria, like mammalian ones, might be involved in the induction of programmed cell death. Fluorescence analysis of mesophyll protoplasts of Pisum sativum in a confocal microscope, fluorescent spectra analysis and time dependence of fluorescence intensity of monomers and of J-aggregates revealed that JC-1 is incorporated and accumulated specifically in plant mitochondria. Analysis of _m during mesophyll protoplast senescence revealed that two subpopulations of mitochondria which differ in _m exist in all analyzed stages of leaf senescence. The first subpopulation contains mitochondria with red fluorescence of J-aggregates due to an unperturbed high _m. The second subpopulation comprises mitochondria with green fluorescence of monomers due to a low _m, proving total depolarization of mitochondrial membranes. Fluorescence analysis demonstrated that even in the latest analyzed stages of leaf senescence, mitochondria with a high _m still exist. Fluorometric measurements revealed that the fluorescence intensity of J-aggregates decreases with the age of plants, which indicates that a reduction of _m during the mesophyll senescence process takes place; however, it does not take place within the whole population of mitochondria of the same protoplast. The reason of this can be due to a dramatic reorganization of mitochondria in mesophyll cells and the appearance of large mitochondria with local heterogeneity of _m in the oldest analyzed stages. All mitochondria in every stage of senescence maintained their membrane organization even when their size, distribution, and spatial organization in protoplasts changed dramatically. We stated that the reduction of _m does not directly induce programmed cell death in mesophyll cells, as opposed to animal apoptosis.Correspondence and reprints: Department of Plant Anatomy and Cytology, Institute of Experimental Biology of Plants, Warsaw University, Miecznikowa 1, 02-096 Warszawa, Poland.     

Adoptions expérimentales de larves entre des fourmis de genres différents:Leptothorax nylanderi Förster etSolenopsis fugax Latreille

Résumé En l'absence de son propre couvain,Solenopsis fugax a élevé des larves deLeptothorax nylanderi, à la température de 22°C. Les ouvrières deSolenopsis détruisirent une partie de ces larves mais nourrirent celles qu'elles épargnèrent; ces dernières grossirent lentement pendant cinq à six mois, sans atteindre le stade prénymphe. Lorsque les ouvrières deS. fugax et les larves deL. nylanderi furent soumises ensemble à un hivernage préalable, elles donnèrent les mêmes résultats que sans hivernage. La présence d'une jeune reine deSolenopsis fut défavorable aux larves deLeptothorax.Inversement,L. nylanderi fut capable d'élever, à la température de 22°C, des larves deS. fugax et de les amener jusqu'au stade adulte. En présence de leurs propres larves, les ouvrières deL. nylanderi détruisirent tapidement toutes les larves deS. fugax introduites dans leur nid. D'autre part, un jeune couvain deLeptothorax remplaçait plus ou moins rapidement les larves deLeptothorax enlevées au préalable; sa présence était alors défavorable au développement des larves deSolenopsis. Un hivernage en début d'expérience fut plutôt favorable auxS. fugax, de même que la présence d'une reine féconde deLeptothorax. LesSolenopsis ainsi obtenus n'ont pas vécu plus de sept semaines. Ils étaient tous de caste ouvrière et de taille très petite.

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Summary When its own eggs and larvae missed,Solenopsis fugax bred larvae ofLeptothorax nylanderi, at a temperature of 22°C. TheSolenopsis workers killed some of this larvae and fed the others; these slowly grew bigger during five or six months but never reached the pre-pupa stage. The result was the same if the workers ofS. fugax and the larvae ofL. nylanderi overwintered together or not at all. A youngSolenopsis queen being there was noxious to the larvae ofLeptothorax.On the contrary,L. nylanderi has been able to breed larvae ofS. fugax up to the imago stage, at a temperature of 22°C. When its own larvae were in the nest, together with larvae ofS. fugax, the workers ofL. nylanderi killed the larvae ofS. fugax. On the other hand, new eggs and young larvae ofLeptothorax had to replace, more or less quickly, the larvae which had been taken away, and that was noxious to the growth ofSolenopsis larvae. An overwintering at the beginning of the experiment was rather favourable toS. fugax as was the presence of a fecundLeptothorax queen. TheSolenopsis thus obtained lived no longer than seven weeks. They all were workers and very small.

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S. Fugax L. Nylanderi 22° . Leptothorax , , , , . . S. Fugax Leptothorax.,L. Nylanderi 22° S. Fugax . L. Nylanderi ( )Leptothorax ; S. Fugax Solenopsis, Leptothorax. S. Fugax . .

     

Adoptions expérimentales de larves entre des fourmis de genres différents (II):Myrmica laevinodis Nylander etAnergates atratulus Schenck

Résumé Nous avons fait élever des larves d'Anergates atratulus par des ouvrières deMyrmica laevinodis à 22°C. Pour y parvenir, il n'est pas utile de faire hivernerensemble les larves d'Anergates et les ouvrières deMyrmica. La présence de larves autochtones n'empêche pas lesMyrmica d'élever des larves d'Anergates. Dans toutes les expériences lesMyrmica ont été soumises au fridavant de recevoir des larves d'Anergates. Aucune reine deMyrmica n'a été utilisée dans ces expériences.Sur les 64 larves d'Anergates que nous avons utilisées, 38 se sont transformées en imagos. C'est au début de l'adoption et au moment des métamorphoses que périrent la plupart des 26Anergates perdus. Les femelles vécurent en général 2 ou 3 jours et cherchèrent très tôt à quitter le nid natal. Les mâles vécurent 2 à 3 semaines.

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Summary Larvae ofAnergates atratulus were experimentally reared by workers ofMyrmica laevinodis, at 22°C. An overwintering of both larvae ofAnergates and workers ofMyrmica is not necessary for the success of that experiment. The presence of larvae ofMyrmica does not keep theMyrmica from rearing larvae ofAnergates. The workers ofMyrmica have been cooled, in all the experiments, before receiving larvae ofAnergates. No queen ofMyrmica have been used in that experiments.38 of the 64 larvae ofAnergates used became imagos. Most of the 26 lostAnergates died at the beginning of the adoption and during the metamorphosis. The females lived generally 2 or 3 days and tried, very early, to leave their native nest. The males lived 2 or 3 weeks.

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Anergates atratulus Myrmica laevinodis, 22 . bmecme Anergates Myrmica. Myrmica Anergates. Myrmica Anergates. Myrmica . 64 Anergates , 38 . 26 Anergates 2 3 . 2 3 .

     

Further studies on cell adhesion based on Lex-Lex interaction,with new approaches: embryoglycan aggregation of F9 teratocarcinoma cells,and adhesion of various tumour cells based on Lex expression

We previously proposed specific interaction of Le^x (Gal1 4[Fuc1 3]-GlcNAc1 3Gal) with Le^x as a basis of cell adhesion in pre-implantation embryos and in aggregation of F9 teratocarcinoma cells, based on several lines of evidence (Eggenset al., J Biol Chem (1989)264:9476–9484). We now present additional evidence for this concept, based on autoaggregation studies of plastic beads coated with glycosphingolipids (GSLs) bearing Le^x or other epitopes, and affinity chromatography on Le^x-columns of multivalent lactofucopentaose III (Le^x oligosaccharide) conjugated with lysyllysine. Comparative adhesion studies of Le^x-expressing tumour cellsvs their Le^x-non-expressing variants showed that only Le^x-expressing cells adhere to Le^x-coated plates and are involved in tumour cell aggregation, in analogy to F9 cell aggregation. The major carrier of Le^x determinant in F9 cells is not GSL but rather polylactosaminoglycan (embryoglycan), and we demonstrated autoaggregation of purified embryoglycan in the presence of Ca²⁺, and reversible dissociation in the absence of Ca²⁺ (addition of EDTA). Defucosylated embryoglycan did not show autoaggregation under the same conditions. Thus, Le^x-Le^x interaction has been demonstrated on a lactosaminoglycan basis as well as a GSL basis. A molecular model of Le^x-Le^x interaction based on minimum energy conformation with involvement of Ca²⁺ is presented.Abbreviations BSA bovine serum albumin - CHO carbohydrate - DMEM Dulbecco's modified Eagle's medium - EDTA ethylenediaminetetraacetic acid - GP glycopeptide - GSL glycosphingolipid - LAG lactosaminoglycan - Le^x Gal1 4[Fuc-1 3]GlcNAc1 R - LFP lacto-N-fucopentaose - LysLys-OH lysyllysinol - Mr relative molecular weight - PBS phosphate-buffered saline - PG paragloboside (Gal1 4GlcNAc1 3Gal1 4Glc1 1Cer) - TBS Tris-buffered saline (10mM Tris-HCl, pH 7.4, containing 0.15M NaCl) - TC tumour cell     

Antimutagenic Role of Autonomous 3′ → 5′-Exonucleases

Original and published data on the antimutagenic role of autonomous 3 5-exonucleases (AE) are analyzed. AE are not bound covalently to DNA polymerases but are often involved in replicative complexes. AE overproduction in bacterial cells is accompanied by a sharp suppression of mutagenesis, whereas AE inactivation in bacteria and higher fungi results in the increase in mutation rates by two to three orders of magnitude. The combined action of AE and DNA polymerases substantially improves the fidelity of their functioning in vitro. The fidelity of nuclease-free DNA polymerases and increases by two to three orders of magnitude in the presence of AE. The fidelity of moderately processive DNA polymerase I increases by two orders of magnitude, and that of highly processive DNA polymerase increases by a factor of 5–10, although both these polymerases possess their own 3 5-exonucleolytic activity. In biochemical experiments, AE was shown to participate directly in the correction of errors made by DNA polymerase I. The presence of AE in multienzyme DNA polymerase complexes increases their fidelity by a factor of 5–10. A model of extrinsic proofreading by AE in DNA biosynthesis is proposed. An investigation of thirty objects from all three kingdoms of life (from archaea and bacteria to mammals, including humans) has shown that AE account for 30–90% of the total cellular 3 5-exonucleolytic activity. Therefore, AE increase significantly the intracellular ratio of 3 5-exonuclease to DNA polymerase activities in a wide phylogenetic variety of species, which always leads to the increasing fidelity of DNA biosynthesis.     

Distribution and composition of particulate organic matter in the Ross Sea (Antarctica)

The biochemical composition and spatial distribution of particulate organic matter (POM) were studied in the Ross Sea (Antarctica) in summer 1989 to assess the quantitative role of organic carbon fractions in the cycling of organic matter in the water column. Large differences in chemical composition were observed between surface and deep layers. The results indicated that, despite large geographical differences, POM was quite homogeneous, of phytoplankton origin and mostly detrital. Different ratios were used to investigate the changes in biochemical composition of particulate organic matter in relation to the ice-melting: CN (organic carbonorganic nitrogen ratio) and C-POMPOC (sum of carbohydrate, protein and lipid carbontotal organic carbon ratio) were used to analyse the percentage of refractory organic material. PPRTPCHO (proteincarbohydrate ratio) were used to establish POM age and RNADNA ratios as a relative measure of particulate activity; POCChl a and N-PPRTChl a ratios were used to estimate the autotrophic contribution to the suspended particulate organic matter. Despite its low caloric value (5.3 Kcal g POM^–1), an high caloric content in the photic layer (1.6 Kcal m^–3 of POM and 2.5 Kcal m^–3 of POC) was found thus indicating that a large amount of food was available to higher trophic levels.     

The ability of acidic pH,growth inhibitors,and glucose to increase the proton motive force and energy spilling of amino acid-fermenting <Emphasis Type="Italic">Clostridium sporogenes</Emphasis> MD1 cultures

Clostridium sporogenes MD1 grew rapidly with peptides and amino acids as an energy source at pH 6.7. However, the proton motive force (p) was only –25 mV, and protonophores did not inhibit growth. When extracellular pH was decreased with HCl, the chemical gradient of protons (ZpH) and the electrical membrane potential () increased. The p was –125 mV at pH 4.7, even though growth was not observed. At pH 6.7, glucose addition did not cause an increase in growth rate, but increased to –70 mV. Protein synthesis inhibitors also significantly increased . Non-growing, arginine-energized cells had a of –80 mV at pH 6.7 or pH 4.7, but was not detected if the F₁F₀ ATPase was inhibited. Arginine-energized cells initiated growth if other amino acids were added at pH 6.7, and and ATP declined. At pH 4.7, ATP production remained high. However, growth could not be initiated, and neither nor the intracellular ATP concentration declined. Based on these results, it appears that C. sporogenes MD1 does not need a large p to grow, and p appears to serve as a mechanism of ATP dissipation or energy spilling.Mandatory disclaimer: Proprietary or brand names are necessary to report factually on available data; however, the USDA neither guarantees nor warrants the standard of the product, and the use of the name by the USDA implies no approval of the product, and exclusion of others that may be suitable.     

Carbon isotope composition in relation to leaf gas exchange and environmental conditions in Hawaiian Metrosideros polymorpha populations

Summary Carbon isotope composition, photosynthetic gas exchange, and nitrogen content were measured in leaves of three varieties of Metrosideros polymorpha growing in sites presenting a variety of precipitation, temperature and edaphic regimes. The eight populations studied could be divided into two groups on the basis of their mean foliar ¹³C values, one group consisting of three populations with mean ¹³C values ca.-26 and another group with ¹³C values ca.-28. Less negative ¹³C values appeared to be associated with reduced physiological availability of soil moisture resulting from hypoxic conditions at a poorly drained high elevation bog site and from low precipitation at a welldrained, low elevation leeward site. Gas exchange measurements indicated that foliar ¹³C and intrinsic wateruse efficiency were positively correlated. Maximum photosynthetic rates were nearly constant while maximum stomatal conductance varied substantially in individuals with foliar ¹³C ranging from-29 to-24. In contrast with the patterns of ¹³C observed, leaf nitrogen content appeared to be genetically determined and independent of site characteristics. Photosynthetic nitrogenuse efficiency was nearly constant over the range of ¹³C observed, suggesting that a compromise between intrinsic water- and N-use efficiency did not occur. In one population variations in foliar ¹³C and gas exchange with leaf cohort age, caused the ratio of intercellular to atmospheric partial pressure of CO₂ predicted from gas exchange and that calculated from ¹³C to be in close agreement only in the two youngest cohorts of fully expanded leaves. The results indicated that with suitable precautions concerning measurement protocol, foliar ¹³C and gas exchange measurements were reliable indicators of potential resource use efficiency by M. polymorpha along environmental gradients.     

Analysis of transgene integration sites in transgenic pigs by fluorescence in situ hybridization

The production of pigs transgenic for human decay accelerating factor (hDAF) as potential donors for clinical organ xenotransplantation was reported several years ago. For this purpose it is required that high levels of hDAF are expressed at relevant sites in transplantable organs. Currently, homozygous lines have been produced as well as lines from crosses between heterozygous animals from different founder lines, termed jigsaw pigs. The purpose of the jigsaw crosses is to combine the desirable hDAF protein expression patterns found in different founder lines. Initial selection of the jigsaw pigs is based on the inheritance of the hDAF integration sites from both lines. Litters with potential homozygous transgenics and jigsaw transgenics were analysed by fluorescence in situ hybridization (FISH) and slot blot analysis. Results show that both slot blot analysis and FISH are suitable to distinguish between pigs that are heterozygous and homozygous for hDAF. However, FISH has the advantage of producing results more rapidly. For the identification of jigsaw pigs FISH analysis was required since slot blot analysis lacked the required accuracy. On basis of these results, FISH analysis was made part of the routine screening programme for hDAF transgenic pigs     

Genetic diversity in relation to heterosis and combining ability in spring wheat

Summary Genetic diversity among ten varieties of spring wheat used as parents in a diallel cross was assessed through multivariate analysis (D²-statistics) and then related to heterosis and SCA effects of their hybrids. The parents fell into three groups. Group I contained the varieties, Nobre, Girua and Carazinho; group II contained Sonalika, Lyallpur and Pitic 62 and group III contained Indus 66, Balaka, Sonora 64rs and MSl. The varieties of group I were good general combiners, while the varieties of group III were poor combiners. Significant heterotic and SCA effects for yield and yield components were observed in the hybrids of the parents belonging to different groups but not in the same group. Genetic divergence between the parents had a positive relationship with heterosis and SCA effects of the hybrids.     

An elongated segment of DNA observed between two human α globin genes

Summary Detailed restriction enzyme analysis of the DNA from a Chinese female showed that one of her chromosomes had a >17.5 kb deletion of DNA, including the , 2, and 1 globin genes, which is present in many Southeast Asians with an -thalassemia-1 chromosome. Her normal chromosome had the expected cluster of -like globin genes (5----2-1-3), but the segment of DNA between the two globin genes was elongated by some 0.5–0.7 kb. Analyses of various restriction sites suggested that this normal variant of the human globin gene complex is due to a crossover between a normal chromosome with () and a chromosome with an -thalassemia-2 (–^3.7) and an -21-hybrid gene.     

Mutation of a conserved CDK site converts a metazoan Elongation Factor 1Bbeta subunit into a replacement for yeast eEF1Balpha

Elongation factor subunit eEF1B (formerly EF-1 in plants and EF-1 in animals) was identified and cloned in a screen for proteins from pea that interact with a cyclin-dependent kinase (CDK). CDKs are enzymes that regulate progression through meiotic and mitotic cell cycles in eukaryotes. eEF1B and the related protein eEF1B (formerly EF-1' in plants and EF-1 in animals and fungi) can catalyze GTP/GDP exchange on the G-protein eEF1A (formerly EF-1 in plants, animals and fungi) during the elongation phase of protein synthesis in eukaryotes. Recombinant Cdc2 and its native homologues from pea extracts associated both in vitro and in vivo with eEF1B. A Cdc2-cyclin B complex phosphorylated recombinant plant eEF1Bs, but not eEF1B. These interactions between CDK and eEF1B prompted investigations into the in vivo consequences of this relationship. Expression of cDNAs encoding rice or pea eEF1B subunits failed to complement a Saccharomyces cerevisiae mutant deleted for the eEF1B gene, as was previously observed for the human eEF1B. However, replacement of Thr91, the sole consensus CDK phosphorylation site in pea eEF1B, with alanine allowed the pea protein to substitute for eEF1B function in vivo. In addition, this rescued strain was severely cold sensitive, and more sensitive to translational inhibitors than wild-type yeast. Taken together, these results suggest a physiological connection between the cyclin-dependent class of kinases and a translational elongation factor in mitotic cells, and provide the first in vivo evidence that an altered form of eEF1B can serve as the guanine nucleotide exchange factor for eEF1A.Communicated by C. P. Hollenberg     

Ganglioside-cholera toxin interactions: a binding and lipid monolayer study

Summary On t.l.c. plates ¹²⁵I-cholera toxin binds to a disialoganglioside tentatively identified as GD_lb with about 10 times less capacity than to ganglioside GM₁. Binding of labeled toxin to both gangliosides was abolished in presence of excess amounts of unlabeled B subunit. Ganglioside extracts from human or pig intestinal mucosa showed toxin binding to gangliosides GM₁ and GD_1b. In ganglioside-containing lipid monolayers the penetration of the toxin was independent of the ganglioside binding capacity.Abbreviations GM₂ Gal-NAc14Gal(3-2NeuAc)14G1c1Cer - GM₁ Gal3Ga1-NAc14Gal(32NeuAc)14G1c11Cer - GD_1a NeuAc23Ga113Gal-NAc14Gal(32NeuAc)14G1c11Cer - GD1b Gall3Gal-NAcl4Gal(32NeuAc82NeuAc)14Glc11Cer - GT_1b NeuAc23Ga113Ga1-NAcal4Gal(3-2NeuAc82NeuAc)14G1c11Cer - dpPC 1,2-hexadecanoyl-sn-glycero-3-phosphocholine - dpPE 1,2-hexadecanoyl-sn-glycero-3-phosphoethanolamine     

Bacterial regeneration of ammonium and phosphate as affected by the carbon:nitrogen:phosphorus ratio of organic substrates

The effect of carbonnitrogenphosphorus (CNP) ratio of organic substrates on the regeneration of ammonium and phosphate was investigated by growing natural assemblages of freshwater bacteria in mineral media supplemented with the simple organic C, N, and P sources (glucose, asparagine, and sodium glycerophosphate, respectively) to give 25 different substrate CNP ratios. Both ammonium and phosphate were regenerated when CN and NP atomic ratios of organic substrates were 101 and 161, respectively. Only ammonium was regenerated when CN and NP ratios were 101 and 10–201, respectively. On the other hand, neither ammonium nor phosphate was regenerated when CN and NP ratios were 151 and 51, respectively. In no case was phosphate alone regenerated. As bacteria were able to alter widely the CNP ratio of their biomass, the growth yield of bacteria appeared primarily dependent on the substrate carbon concentration, irrespective of a wide variation in the substrate CNP ratio.     

‘Fine’ and ‘coarse’ mycorrhizal fungi on red clover plants in acid soils: Root colonization and plant responses

Three sterilized acid soils were inoculated with inocula of vesicular-arbuscular mycorrhizal fungi. Soils were limed and/or P fertilized to produce different fertility levels. Most inocula consisted of mixtures of fine + coarse type endophytes. Red clover (Trifolium pratense L.) was seeded in pots and grown in a glasshouse for 4 months. Root colonization by VAM fungi, the relative infection byGlomus tenue compared to that by coarse VAM fungi and the effect of inoculation on red clover growth and mineral nutrition (P, K, Ca and Mg) were studied. Spores were also checked and tentatively identified.Results showed that root colonization by VAM fungi was higher than 50% in most cases, the lower values being found in the soil with the highest P content. Inocula containingG. mosseae + G. tenue infected plant roots only in limed (pH>5.7) soils. A study of the relative colonization by fine and coarse endophytes showed that the competitive ability againstG. tenue followed the orderG. fasiculatum > G. mosseae > G. epigaeum > G. macrocarpum, although soil properties and fertility were crucial factors.Glomus lacteum was tentatively identified in two of the three experimental soils. The inoculum in whichGlommus tenue was most infective was also the most efficient in improving plant growth and nutrient uptake. The effect of inoculation on P and Mg uptake followed a similar pattern.     

Using stable isotopes to investigate migratory connectivity of the globally threatened aquatic warbler Acrocephalus paludicola

Understanding the links between breeding and wintering areas of migratory species has important ecological and conservation implications. Recently, stable isotope technology has been used to further our understanding. Stable isotope ratios vary geographically with a range of biogeochemical factors and isotope profiles in organisms reflect those in their food and environment. For inert tissues like feathers, isotope profiles reflect the environment in which they were formed. Following large-scale habitat destruction, the globally threatened aquatic warbler Acrocephalus paludicola has a fragmented breeding population across central Europe, largely in Belarus, Poland and Ukraine. The species sub-Saharan African wintering grounds have not yet been discovered, and this significantly hampers conservation efforts. Aquatic warblers grow their flight feathers on their wintering grounds, and we analysed stable isotope ratios (¹⁵N, ¹³C, D) in rectrices of adults from six main breeding sites (subpopulations) across Europe to determine whether different breeding subpopulations formed a single mixed population on the wintering grounds. ¹⁵N varies considerably with dietary trophic level and environmental factors, and D with the D in rainfall; neither varied between aquatic warbler subpopulations. Uniform feather ¹⁵N signatures suggest no major variation in dietary trophic level during feather formation. High variance and inter-annual differences in mean D values hinder interpretation of these data. Significant differences in mean ¹³C ratios existed between subpopulations. We discuss possible interpretations of this result, and consider differences in moulting latitude of different subpopulations to be the most parsimonious. ¹³C in plants and animals decreases with latitude, along a steep gradient in sub-Saharan Africa. Birds from the most north-westerly breeding subpopulation (Karsibor, Poland) had significantly lower variance in ¹³C and ¹⁵N than birds from all other sites, suggesting either that birds from Karsibor are less geographically dispersed during moult, or moult in an area with less isotopic heterogeneity. Mean ¹³C signatures from winter-grown feathers of different subpopulations were positively correlated with the latitude and longitude of breeding sites, suggesting a strong relationship between European breeding and African winter moulting latitudes. The use of stable isotopes provides novel insights into migratory connectivity and migration patterns in this little-known threatened species.