Is coproporphyrin III a copper-acquisition compound in Paracoccus denitrificans?

Paracoccus denitrificans is a soil bacterium which can respire aerobically and also denitrify if oxygen is absent. Both processes are highly dependent on copper enzymes and copper is therefore likely to be an essential trace element for the bacterium. If copper is not easily available, a copper-acquisition mechanism would be highly beneficial. In this paper, we have addressed the question of whether Paracoccus secretes a copper-acquisition compound functionally analogous to that found in some methanotrophs. Bacteria were grown both in copper-containing and copper-deficient denitrification media, cells were removed by centrifugation and the supernatant was analysed using chromatography and spectroscopy. Bacterial growth yield in the absence of copper was 70-80% of that in the copper-containing medium. A notable difference between the two culture conditions was that spent copper-deficient medium was pigmented, whereas the copper-containing medium was not. Spectrophotometry indicated that a red compound with an absorption maximum at 405 nm was produced under copper-limited conditions. In addition to the strong 405 nm maximum, the visible spectrum of the purified red molecule had weaker maxima at 535 nm and 570 nm, features typical of metallated tetrapyrroles. Mass spectrometry showed that the purified pigment had a molecular mass of 716.18. Moreover, the fine structure of the mass spectrum suggested the presence of zinc and was consistent with the chemical formula of C(36)H(36)N(4)O(8)Zn. The presence of zinc was also demonstrated using inductively coupled plasma atomic emission spectroscopy. Fragmentation analysis with mass spectrometry showed the release of consecutive 59 Da fragments, assignable to four -CH(2)-COOH moieties. Thin layer chromatography as well as NMR analysis of the C-13/N-15 labelled red pigment suggested that it is predominantly zinc coproporphyrin III with a minor fraction of metal-free coproporphyrin III. We propose that in a copper-poor environment P. denitrificans secretes coproporphyrin III for copper chelation and subsequent uptake of the bound copper into the cell. Consistent with this idea, cell yields of copper-deficient cultures grown in the presence of 1 microM copper-coproporphyrin III were 90-95% of the yields of cultures grown in the normal copper-containing media. Coproporphyrin III may work as a copper-acquisition compound in P. denitrificans.     

Geographical trends in the yolk carotenoid composition of the pied flycatcher (Ficedula hypoleuca)

Carotenoids in the egg yolks of birds are considered to be important antioxidants and immune stimulants during the rapid growth of embryos. Yolk carotenoid composition is strongly affected by the carotenoid composition of the female??s diet at the time of egg formation. Spatial and temporal differences in carotenoid availability may thus be reflected in yolk concentrations. To assess whether yolk carotenoid concentrations or carotenoid profiles show any large-scale geographical trends or differences among habitats, we collected yolk samples from 16 European populations of the pied flycatcher, Ficedula hypoleuca. We found that the concentrations and proportions of lutein and some other xanthophylls in the egg yolks decreased from Central Europe northwards. The most southern population (which is also the one found at the highest altitude) also showed relatively low carotenoid levels. Concentrations of ??-carotene and zeaxanthin did not show any obvious geographical gradients. Egg yolks also contained proportionally more lutein and other xanthophylls in deciduous than in mixed or coniferous habitats. We suggest that latitudinal gradients in lutein and xanthophylls reflect the lower availability of lutein-rich food items in the northern F. hypoleuca populations and in montane southern populations, which start egg-laying earlier relative to tree phenology than the Central European populations. Similarly, among-habitat variation is likely to reflect the better availability of lutein-rich food in deciduous forests. Our study is the first to indicate that the concentration and profile of yolk carotenoids may show large-scale spatial variation among populations in different parts of the species?? geographical range. Further studies are needed to test the fitness effects of this geographical variation.     

A synthesis of methane emissions from 71 northern,temperate, and subtropical wetlands

Wetlands are the largest natural source of atmospheric methane. Here, we assess controls on methane flux using a database of approximately 19 000 instantaneous measurements from 71 wetland sites located across subtropical, temperate, and northern high latitude regions. Our analyses confirm general controls on wetland methane emissions from soil temperature, water table, and vegetation, but also show that these relationships are modified depending on wetland type (bog, fen, or swamp), region (subarctic to temperate), and disturbance. Fen methane flux was more sensitive to vegetation and less sensitive to temperature than bog or swamp fluxes. The optimal water table for methane flux was consistently below the peat surface in bogs, close to the peat surface in poor fens, and above the peat surface in rich fens. However, the largest flux in bogs occurred when dry 30‐day averaged antecedent conditions were followed by wet conditions, while in fens and swamps, the largest flux occurred when both 30‐day averaged antecedent and current conditions were wet. Drained wetlands exhibited distinct characteristics, e.g. the absence of large flux following wet and warm conditions, suggesting that the same functional relationships between methane flux and environmental conditions cannot be used across pristine and disturbed wetlands. Together, our results suggest that water table and temperature are dominant controls on methane flux in pristine bogs and swamps, while other processes, such as vascular transport in pristine fens, have the potential to partially override the effect of these controls in other wetland types. Because wetland types vary in methane emissions and have distinct controls, these ecosystems need to be considered separately to yield reliable estimates of global wetland methane release.     

Photosynthetic traits of Sphagnum and feather moss species in undrained,drained and rewetted boreal spruce swamp forests

In restored peatlands, recovery of carbon assimilation by peat‐forming plants is a prerequisite for the recovery of ecosystem functioning. Restoration by rewetting may affect moss photosynthesis and respiration directly and/or through species successional turnover. To quantify the importance of the direct effects and the effects mediated by species change in boreal spruce swamp forests, we used a dual approach: (i) we measured successional changes in moss communities at 36 sites (nine undrained, nine drained, 18 rewetted) and (ii) photosynthetic properties of the dominant Sphagnum and feather mosses at nine of these sites (three undrained, three drained, three rewetted). Drainage and rewetting affected moss carbon assimilation mainly through species successional turnover. The species differed along a light‐adaptation gradient, which separated shade‐adapted feather mosses from Sphagnum mosses and Sphagnum girgensohnii from other Sphagna, and a productivity and moisture gradient, which separated Sphagnum riparium and Sphagnum girgensohnii from the less productive S. angustifolium, S. magellanicum and S. russowii. Undrained and drained sites harbored conservative, low‐production species: hummock‐Sphagna and feather mosses, respectively. Ditch creation and rewetting produced niches for species with opportunistic strategies and high carbon assimilation. The direct effects also caused higher photosynthetic productivity in ditches and in rewetted sites than in undrained and drained main sites.     

A monoclonal antibody recognizes an epitope common to an avian-specific nuclear antigen and to cytokeratins

X3, a monoclonal antibody of unusual specificity, is described. This antibody reacts with one or more cytokeratin polypeptides and also reacts with an avian (chicken, quail) nuclear antigen that appears to be present in all cell types (chicken) tested, although with variable staining pattern and intensity. This antigen is distinct from the cytokeratins but does have an epitope in common with this class of proteins. It disappears from the nucleus during the early stages of cell division and reappears during anaphase as a granular cytoplasmic structure. In late telophase the antigen is relocated in the nucleus. This antigen, which we have designated as avian-specific nuclear antigen (AVNA), is not associated with chromatin or ribonucleoproteins. From immunoblotting experiments on chicken fibroblast nuclei, AVNA is probably a complex composed of one or several polypeptides, one of which has a molecular weight of approximately 60 kD. The proteins were identified as nuclear matrix proteins rather than pore complex-lamina proteins by immunoblotting experiments on the purified nuclear matrix of chicken erythrocytes. The major polypeptide had a molecular weight of 60 kD and the minor polypeptide a molecular weight of 69 kD.     

The impacts of treatment with biocontrol fungus (Phlebiopsis gigantea) on bacterial diversity in Norway spruce stumps

The biocontrol agent Phlebiopsis gigantea has been intensively applied to the surface of Picea abies stumps to control Heterobasidion root rot. But little is known about the possible impact of this treatment on the resident bacteria community in the stumps. High throughput DNA bar-coded pyrosequencing was used to characterize the diversity of bacteria in the stumps of P. abies at 1, 6 and 13 years after treatment with P. gigantea. The sequences were classified into 12 phyla and 160 genera, of which Proteobacteria and Acidobacteria were the most abundant groups over time. Moreover, at the initial stages of decay, Proteobacteria were the most abundant whereas Acidobacteria were the most common at advanced stages of decay. Treatment with P. gigantea led to significant increase of the genus Acidobacteria-Gp1 at 1 year after treatment. The analysis of observed and estimated operational taxonomic units (OTUs) as well as diversity indices revealed that P. gigantea treatment significantly decreased the initial bacterial richness in the stumps, but the bacterial community gradually recovered and the negative effects of P. gigantea was attenuated. These results provide additional insight on the risk assessment as well as environmental impact on the long-term use of P. gigantea in the control of Heterobasidion root rot in conifer forests.     

Activation of Plasmin in Mastitic Milk

Milk and whey samples from healthy and inflamed udder quarters of 10 Ayrshire cows were analyzed for proteolytic activity using radial caseolysis procedures, a fluorogenic coumaryl peptide substrate, and casein agarose zymography. Free lysosomal enzyme activity (N–acetyl–beta–D–glucosaminidase) was used as the criterion for inflammation. All mastitic milk samples had proteolytic activity, tentatively identified as plasmin (comigration at Mr 83 000 and characteristic fragmentation). The plasmin activities in mastitic milk were on average 2.9 μg/ml (range 0.5–12.5) as measured by radial caseolysis. Milk or whey specimens from healthy quarters were all negative except 1 in which an activity of 0.1 μg/ml was found in both specimens. The caseolytic activities were totally inhibited by 50 KITJ/ml of aprotinin, a serine proteinase inhibitor from bovine lung. No free plasminogen activator (PA) activity was found in any of the samples. Howewer, according to zymographic analyses PA molecules corresponding to urokinase were found in healthy and especially in mastitic specimens. Analysis of plasmin may provide an alternative means of screening for mastitic milk samples.     

Loss of Occludin and Functional Tight Junctions, but Not ZO-1, during Neural Tube Closure—Remodeling of the Neuroepithelium Prior to Neurogenesis

Neuroepithelial cells can generate nonepithelial cells, the neurons. Here we have investigated, for chick and mouse embryos, the epithelial character of neuroepithelial cells in the context of neurogenesis by examining the presence of molecular components of tight junctions during the transition from the neural plate to the neural tube. Immunoreactivity for occludin, a transmembrane protein specific to tight junctions, was detected at the apical end of the lateral membrane of neuroepithelial cells throughout the chick neural plate. During neural tube closure, occludin disappeared from all neuroepithelial cells. Correspondingly, the addition of horseradish peroxidase to the apical side of the neuroepithelium by injection into the amniotic cavity of mouse embryos revealed the presence of functional tight junctions in the neural plate (Embryonic Day 8), but not the neural tube (Embryonic Day 9). In contrast to occludin, expression of ZO-1, a peripheral membrane protein of tight junctions, increased from the neural plate to the neural tube stage, also being confined to the apical end of the lateral neuroepithelial cell membrane. This localization coincided with that of N-cadherin, whose expression increased concomitantly with the disappearance of occludin. We propose that the loss of tight junctions from neuroepithelial cells reflects an overall decrease in their epithelial nature, which precedes the generation of neurons.