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Peatlands are common in many parts of the world. Draining and other changes in the use of peatlands increase atmospheric CO 2 concentration. If we are to make reliable quantitative predictions of that effect, we need good information on the CO 2 emission rates from peatlands. The present study uses two different methods for predicting CO 2 -C release of peatland soils: (i) a 40-year field investigation of balancing organic carbon stocks and (ii) short-term CO 2 -C release rates from laboratory experiments. To estimate long-term losses of peat, and its resulting C input to the atmosphere, we combined highly detailed maps of surface topography and its changes, and the organic C contents and bulk densities of a drained peatland from different years. Short-term CO 2 -C release rates were measured in the laboratory by incubating soil samples from several soil horizons at various temperatures and soil moistures. We then derived nonlinear CO 2 -C production functions, which we incorporated into a numerical simulation model (HYDRUS). Using HYDRUS, we calculated daily soil water components and CO 2 -release for (i) real-climate data from 1950 to 2003 and (ii) a climate scenario extending to 2050, including an increase in temperature of 2°C and 20% less rainfall during the summer half year, i.e. from April to September inclusive. From our field measurements, we found a mean annual decrease of 0.7 cm in the thickness of the peat. Large losses (> 1.5 cm year À1 ) occurred only during periods when groundwater levels were low (i.e. a deep water-table). The annual CO 2 -C release results in a mean loss from the peat of about 700 g CO 2 -C m À2 , mostly as a direct contribution to the atmosphere. Both methods produced very similar results. The model scenarios demonstrated that CO 2 -C loss is mainly controlled by the groundwater (i.e. water-table) depth, which controls subsurface aeration. A local climate scenario estimated a c. 5% increase of CO 2 -C losses within the next 50 years.

The ability of bacteria to aggregate and form biofilms impairs phagocytosis by polymorphonuclear leukocytes (PMNs). The aim of this study was to examine if the size of aggregates is critical for successful phagocytosis and how bacterial biofilms evade phagocytosis. We investigated the live interaction between PMNs and Pseudomonas aeruginosa, Staphylococcus aureus, Escherichia coli and Staphylococcus epidermidis using confocal scanning laser microscopy. Aggregate size significantly affected phagocytosis outcome and larger aggregates were less likely to be phagocytized. Aggregates of S. epidermidis were also less likely to be phagocytized than equally-sized aggregates of the other three species. We found that only aggregates of approx. 5 μm diameter or smaller were consistently phagocytosed. We demonstrate that planktonic and aggregated cells of all four species significantly reduced the viability of PMNs after 4 h of incubation. Our results indicate that larger bacterial aggregates are less likely to be phagocytosed by PMNs and we propose that, if the aggregates become too large, circulating PMNs may not be able to phagocytose them quickly enough, which may lead to chronic infection.

The compartmentalization of PAPS (the sulfate donor 39-phosphoadenosine 59-phosphosulfate) synthesis (mainly in plastids), PAPS consumption (in the cytosol), and PAP (the stress signaling molecule 39-phosphoadenosine 59-phosphate) degradation (in plastids and mitochondria) requires organellar transport systems for both PAPS and PAP. The plastidial transporter PAPST1 (PAPS TRANSPORTER1) delivers newly synthesized PAPS from the stroma to the cytosol. We investigated the activity of PAPST2, the closest homolog of PAPST1, which unlike PAPST1 is targeted to both the plastids and mitochondria. Biochemical characterization in Arabidopsis thaliana revealed that PAPST2 mediates the antiport of PAP, PAPS, ATP, and ADP. Strongly increased cellular PAP levels negatively affect plant growth, as observed in the fry1 papst2 mutant, which lacks the PAP-catabolizing enzyme SALT TOLERANCE 1 and PAPST2. PAP levels were specifically elevated in the cytosol of papst2 and fiery1 papst2, but not in papst1 or fry1 papst1. PAPST1 failed to complement the papst2 mutant phenotype in mitochondria, because it likely removes PAPS from the cell, as demonstrated by the increased expression of phytosulfokine genes. Overexpression of SAL1 in mitochondria rescued the phenotype of fry1 but not fry1 papst2. Therefore, PAPST2 represents an important organellar importer of PAP, providing a piece of the puzzle in our understanding of the organelle-tonucleus PAP retrograde signaling pathway.

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