Extracellular dissolved organic carbon released from phytoplankton as a source of carbon for heterotrophic bacteria in lakes of different humic content

The quantitative importance of photosynthetically produced dissolved organic carbon (PDOC) released from phytoplankton as a source of carbon for pelagic, heterotrophic bacteria was investigated in four temperate Swedish lakes, of which two had low (≈20 mg Pt 1⁻¹), and two moderately high (60–80 mg Pt 1⁻¹) humic content. The bacterial assimilation of PDOC was estimated with the ¹⁴C method, and the total production of the heterotrophic bacteria was estimated with the [3H]thymidine incorporation method. The release of PDOC from natural communities of phytoplankton was not restricted to periods of photosynthesis, but often continued during periods of darkness. Heterotrophic bacteria often assimilated the labile components of the PDOC at high rates (up to 73% of the released PDOC was assimilated during the incubation in our experiments). The contribution of PDOC to bacterial production exhibited large within-lake seasonal variations, but PDOC was at certain times, both in humic and non-humic lakes, a quantitatively very important carbon source for the heterotrophic bacteria. Under periods of comparatively low primary production, heterotrophic bacteria in humic lakes appear to utilize allochthonous, humic substances as a substrate.     

Changes in the land mollusc fauna and soil chemistry in an inland district in southern Sweden

The land mollusc fauna and some abiotic soil variables were investigated at 20 forest sites SW of Vaxjo, southern Sweden, in 1964-66 and again in 1987-88 to evaluate possible effects of soil acidification, base cation leaching and nitrogen deposition The number of snail individuals decreased on average by 60% in herb-rich deciduous forests and by 80% in spruce and herb-poor oak forests Nesovitrea petronella, N hammonis, Euconulus fulvus, Vertigo substriata, Cochlicopa lubrica and Clausilia bidentata were most affected The calcium content in litter and surface layer of soil had decreased on average by 31%
The snail number decrease is negatively correlated to base saturation In the lower range of calcium content the change is in good accordance with a significant regression line of abundance on calcium from 1964–66
The snail abundance is positively correlated to base saturation, to soil moisture and probably also to nitrogen content
The soil chemistry and the snail fauna of the coniferous forest sites are so severely affected that a continued acidification and base cation leaching might lead to extinction of the snail fauna in this kind of forest Problems, possibilities and use of results from retrospective studies on the soil fauna are discussed     

Habitat use and resource overlap by breeding Golden Plovers and Dotterels (Pluvialis apricaria, Charadrius morinellus)

Summary Golden Plovers and Dotterels breeding in sympatry fed and nested onCladonia heath, especially in the early part of the season. An increasing number of habitats were used as they became available, andSalix herbacea beds were used disproportionately frequently by post-breeding flocks of both species and off-duty (incubating) Golden Plover females, apparently due to good insect and arachnid availability late in the season. The species overlapped considerably in resource use and showed no signs of resource partitioning under circumstances where it could be expected from the competitive exclusion principle. Aggression from Golden Plovers towards Dotterels indicated some competitive interaction early in the season, when snow cover reduced the feeding grounds to 5–25 %. There was, however, no evidence for interspecific effects on breeding densities. It is concluded that competition between the two species is of little importance; their spacing patterns are probably usually governed by other factors than food.

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Zusammenfassung Gold- und Mornellregenpfeifer benutzten bei sympatrischen Vorkommen in S-Norwegen in hohem Maß flache Hügelketten mitCladonia sowohl als Nesthabitat als auch zur Nahrungs-suche, besonders zu Beginn der Brutsaison. Diese flachen Hügelketten waren arm an Invertebraten, doch reich anEmpetrum-Beeren, und bildeten fast das einzige zugängliche Habitat vor dem vollen Eintritt der Schneeschmelze. Später wurden mehrere Habitate besetzt. Flächen mitSalix herbacea wurden sowohl von Vögeln, die das Brutgeschäft beendet hatten (Trupps beider Arten), als auch von Weibchen des Goldregenpfeifers in der Brutzeit vorzugsweise aufgesucht. Wahrscheinlich hing dies mit dem Angebot an Insekten und Spinnen in der zweiten Hälfte der Brutzeit zusammen. Die Ressourcennutzung beider Arten war sehr ähnlich; Anzeichen für Ressourcenaufteilung gemäß dem Konkurrenz-Ausschlußprinzip wurden nicht gefunden. Aggression von Goldregenpfeifern gegen Mornellregenpfeifer am Anfang der Saison deutet auf Konkurrenz zu dieser Zeit hin, als nur 5–25 % der Fläche vom Schnee frei waren. Eine Auswirkung auf die Siedlungsdichte ließ sich nicht erkennen. Konkurrenz zwischen beiden Arten dürfte also nur einen geringen Einfluß auf die Dispersionsmuster haben, das wahrscheinlich von anderen Faktoren als der Nahrung bestimmt wird.

     

Estimating the distribution of the G(2) phase duration from flow cytometric histograms

A mathematical model, based on branching processes, is proposed to interpret BrdUrd DNA FCM-derived data. Our main interest is in determining the distribution of the G(2) phase duration. Two different model classes involving different assumptions on the distribution of the G(2) phase duration are considered. Different assumptions of the G(2) phase duration result in very similar distributions of the S phase duration and the estimated means and standard deviations of the G(2) phase duration are all in the same range.     

Use of a novel nonantibiotic triple marker gene cassette to monitor high survival of Pseudomonas fluorescens SBW25 on winter wheat in the field

Pseudomonas fluorescens SBW25 was tagged with a triple marker gene cassette containing gfp, encoding green fluorescent protein; luxAB, encoding luciferase; and telABkilA, encoding tellurite resistance, and the tagged strain was monitored in the first Swedish field release of a genetically modified microorganism (GMM). The cells were inoculated onto winter wheat seeds and the GMM cells (SBW25:tgl) were monitored in the field from September 2005 to May 2006 using plating, luminometry and microscopic analyses. Cell numbers were high on all sampling occasions and metabolically active cells were detected on all plant parts. Field results were similar to those obtained in a parallel phytotron study, although the amount of SBW25:tgl detected on shoots was significantly higher in the phytotron than in the field. After winter, cell counts were 100-fold higher on the roots and root-associated soil compared with prewinter measurements, although the cells had a lower relative metabolic activity. The wheat seeds were naturally infested with Microdochium nivale, but no treatment resulted in reduction of disease symptoms. No SWB25:tgl cells were ever found in bulk soil or uninoculated plants. The Swedish field trial results complement and contrast with prior field studies performed with the same parent organism in the United Kingdom under different soil, plant and climatic conditions.     

Monitoring growth of the methanogenic archaea Methanobacterium formicicum using an electronic nose

Growth of the methanogenic archaea, Methanobacterium formicicum, in pure culture was monitored by analysing samples from the gas phase with an array of chemical gas sensors (an `electronic nose'). Analyses of the methane and protein formation rates were used as independent parameters of growth, and the data obtained from the electronic nose were evaluated using principal component analysis (PCA). We found that different growth phases can be distinguished with the electronic nose followed by PCA evaluation. The fast response of the sensors in combination with the high correlations with other parameters measuring growth show that the electronic nose can be a useful tool to rapidly determine methanogenic growth.     

Phylogenetic reconstruction of ancestral character states for gene expression and mRNA splicing data

Background  

As genomes evolve after speciation, gene content, coding sequence, gene expression, and splicing all diverge with time from ancestors with close relatives. A minimum evolution general method for continuous character analysis in a phylogenetic perspective is presented that allows for reconstruction of ancestral character states and for measuring along branch evolution.     

Placebo in emotional processing--induced expectations of anxiety relief activate a generalized modulatory network

Placebo analgesia and reward processing share several features. For instance, expectations have a strong influence on the subsequent emotional experience of both. Recent imaging data indicate similarities in the underlying neuronal network. We hypothesized that placebo analgesia is a special case of reward processing and that placebo treatment could modulate emotional perception in the same way as does pain perception. The behavioral part of this study indicates that placebo treatment has an effect on how subjects perceive unpleasant pictures. Furthermore, event-related fMRI demonstrated that the same modulatory network, including the rostral anterior cingulate cortex and the lateral orbitofrontal cortex, is involved in both emotional placebo and placebo analgesia. These effects were correlated with the reported placebo effect and were predicted by the amount of treatment expectation induced on a previous day. Thus, the placebo effect may be considered to be a general process of modulation induced by the subjects' expectations.     

Phylogeny of cetrarioid lichens (Parmeliaceae) inferred from ITS and b-tubulin sequences,morphology, anatomy and secondary chemistry

Phylogenetic relationships within the family Parmeliaceae (lichenized ascomycetes) with emphasis on the heterogeneous group of cetrarioid lichens are reconstructed. The results are based on cladistic analyses of DNA-sequences, morphological and chemical data. Almost all currently recognized cetrarioid genera were included in the analyses together with parmelioid and alectorioid members of the presumably monophyletic family Parmeliaceae. We tried to sample taxonomic diversity of the family as widely as possible. The ITS1-5.8S-ITS2 region of the rDNA and a partial β-tubulin gene from 126 samples representing 82 species were analysed. Cetrarioid lichens were identified as a monophyletic group, supported by both ITS and β-tubulin characters. This group was reanalysed using 47 morphological, anatomical and secondary chemistry characters combined with the DNA data matrix. ITS and β-tubulin sequences provide congruent information, and a clear correlation between DNA-data and conidial shape is observed. The current taxonomy of the cetrarioid lichens is discussed and compared with the phylogenetic trees obtained here. A comprehensive study of the phylogeography of some bipolar or subcosmopolitic species with representatives from both hemispheres was performed. Cetraria aculeata is the only taxon where correlation between DNA-data and geographic origin is observed.