Immobilisation of phosphorus by iron-coated roots of submerged macrophytes

Hydrobiologia - To observe effects on the phosphorus retention mechanisms of a lake after re-colonisation by macrophytes, Potamogeton crispus L. and Elodea canadensis Michx. were planted in lab...     

Complete nucleotide sequence of the Oenothera elata plastid chromosome, representing plastome I of the five distinguishable euoenothera plastomes

We describe the 159,4443-bp sequence of the plastid chromosome of Oenothera elata (evening primrose). The Oe. elata plastid chromosome represents type I of the five genetically distinguishable basic plastomes found in the subsection Euoenothera. The genus Oenothera provides an ideal system in which to address fundamental questions regarding the functional integration of the compartmentalised genetic system characteristic of the eukaryotic cell. Its highly developed taxonomy and genetics, together with a favourable combination of features in its genetic structure (interspecific fertility, stable heterozygous progeny, biparental transmission of organelles, and the phenomenon of complex heterozygosity), allow facile exchanges of nuclei, plastids and mitochondria, as well as individual chromosome pairs, between species. The resulting hybrids or cybrids are usually viable and fertile, but can display various forms of developmental disturbance. Received: 9 January 2000 / Accepted: 29 January 2000     

Sulphate-mediated phosphorus mobilization in riverine sediments at increasing sulphate concentration, River Spree, NE Germany

The study focuses on the response of a sulphate rich lowland river (River Spree) to a further increase in sulphate concentration as a result of mining activities in its catchments. It was hypothesized that riverine sediments could be conservative against an increase in sulphate concentration relating to both the intensity of sulphate reduction and the accompanying P mobilization. The usually lower amount of organic matter, compared to lakes or wetlands, and the high contents of iron oxides in the Spree sediment from discharged mining waters should counteract an enhanced P mobilization. Three short-term incubation experiments were carried out to test the sensitivity of different sediment horizons (0–10, 10–20 and 20–30 cm), the influence of temperature (5 and 25 °C) and the effect of a rising sulphate concentration (2.6–7.8 mM) on P mobilization rates (PMR) and sulphate reduction rates (SRR). Contrary to our initial hypothesis sulphate played a key role for P mobilization in riverine sediments because (1) all sulphate treated horizons showed a significant increase in pore water P concentrations, (2) increasing sulphate concentrations led to rising SRR and PMR, (3) the highest response on sulphate-mediated P mobilization was observed by a temperature enhancement of 20 °C. PMR increased one order of magnitude at all tested sulphate concentrations, but these increases in PMR only slightly effected the P concentrations in the overlying water. In conclusions, an increase of internal P load is only expected in case of doubling the recent in situ sulphate concentrations, but extended warm periods as an effect of climate change or increasing temperature, respectively, could be of more importance.     

Use of laser microdissection for phylogenetic characterization of polyphosphate-accumulating bacteria

Our novel approach for taxonomic identification of uncultured bacteria harboring specific physiological features in complex environmental samples combines cell collection by laser microdissection and subsequent DNA analysis. The newly developed approach was successfully tested for collection and phylogenetic characterization of polyphosphate-accumulating bacteria in activated sludge and lake sediment.     

A Metabolic Probe-Enabled Strategy Reveals Uptake and Protein Targets of Polyunsaturated Aldehydes in the Diatom Phaeodactylum tricornutum

Diatoms are unicellular algae of crucial importance as they belong to the main primary producers in aquatic ecosystems. Several diatom species produce polyunsaturated aldehydes (PUAs) that have been made responsible for chemically mediated interactions in the plankton. PUA-effects include chemical defense by reducing the reproductive success of grazing copepods, allelochemical activity by interfering with the growth of competing phytoplankton and cell to cell signaling. We applied a PUA-derived molecular probe, based on the biologically highly active 2,4-decadienal, with the aim to reveal protein targets of PUAs and affected metabolic pathways. By using fluorescence microscopy, we observed a substantial uptake of the PUA probe into cells of the diatom Phaeodactylum tricornutum in comparison to the uptake of a structurally closely related control probe based on a saturated aldehyde. The specific uptake motivated a chemoproteomic approach to generate a qualitative inventory of proteins covalently targeted by the α,β,γ,δ-unsaturated aldehyde structure element. Activity-based protein profiling revealed selective covalent modification of target proteins by the PUA probe. Analysis of the labeled proteins gave insights into putative affected molecular functions and biological processes such as photosynthesis including ATP generation and catalytic activity in the Calvin cycle or the pentose phosphate pathway. The mechanism of action of PUAs involves covalent reactions with proteins that may result in protein dysfunction and interference of involved pathways.