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Search Results: 1 - 10 of 20386 matches for " Sabine U. Gerbersdorf "
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Impairment of the Bacterial Biofilm Stability by Triclosan
Helen V. Lubarsky, Sabine U. Gerbersdorf, Cédric Hubas, Sebastian Behrens, Francesco Ricciardi, David M. Paterson
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0031183
Abstract: The accumulation of the widely-used antibacterial and antifungal compound triclosan (TCS) in freshwaters raises concerns about the impact of this harmful chemical on the biofilms that are the dominant life style of microorganisms in aquatic systems. However, investigations to-date rarely go beyond effects at the cellular, physiological or morphological level. The present paper focuses on bacterial biofilms addressing the possible chemical impairment of their functionality, while also examining their substratum stabilization potential as one example of an important ecosystem service. The development of a bacterial assemblage of natural composition – isolated from sediments of the Eden Estuary (Scotland, UK) – on non-cohesive glass beads (<63 μm) and exposed to a range of triclosan concentrations (control, 2 – 100 μg L?1) was monitored over time by Magnetic Particle Induction (MagPI). In parallel, bacterial cell numbers, division rate, community composition (DGGE) and EPS (extracellular polymeric substances: carbohydrates and proteins) secretion were determined. While the triclosan exposure did not prevent bacterial settlement, biofilm development was increasingly inhibited by increasing TCS levels. The surface binding capacity (MagPI) of the assemblages was positively correlated to the microbial secreted EPS matrix. The EPS concentrations and composition (quantity and quality) were closely linked to bacterial growth, which was affected by enhanced TCS exposure. Furthermore, TCS induced significant changes in bacterial community composition as well as a significant decrease in bacterial diversity. The impairment of the stabilization potential of bacterial biofilm under even low, environmentally relevant TCS levels is of concern since the resistance of sediments to erosive forces has large implications for the dynamics of sediments and associated pollutant dispersal. In addition, the surface adhesive capacity of the biofilm acts as a sensitive measure of ecosystem effects.
The Stabilisation Potential of Individual and Mixed Assemblages of Natural Bacteria and Microalgae
Helen V. Lubarsky,Cédric Hubas,Melanie Chocholek,Fredrik Larson,Werner Manz,David M. Paterson,Sabine U. Gerbersdorf
PLOS ONE , 2012, DOI: 10.1371/journal.pone.0013794
Abstract: It is recognized that microorganisms inhabiting natural sediments significantly mediate the erosive response of the bed (“ecosystem engineers”) through the secretion of naturally adhesive organic material (EPS: extracellular polymeric substances). However, little is known about the individual engineering capability of the main biofilm components (heterotrophic bacteria and autotrophic microalgae) in terms of their individual contribution to the EPS pool and their relative functional contribution to substratum stabilisation. This paper investigates the engineering effects on a non-cohesive test bed as the surface was colonised by natural benthic assemblages (prokaryotic, eukaryotic and mixed cultures) of bacteria and microalgae. MagPI (Magnetic Particle Induction) and CSM (Cohesive Strength Meter) respectively determined the adhesive capacity and the cohesive strength of the culture surface. Stabilisation was significantly higher for the bacterial assemblages (up to a factor of 2) than for axenic microalgal assemblages. The EPS concentration and the EPS composition (carbohydrates and proteins) were both important in determining stabilisation. The peak of engineering effect was significantly greater in the mixed assemblage as compared to the bacterial (x 1.2) and axenic diatom (x 1.7) cultures. The possibility of synergistic effects between the bacterial and algal cultures in terms of stability was examined and rejected although the concentration of EPS did show a synergistic elevation in mixed culture. The rapid development and overall stabilisation potential of the various assemblages was impressive (x 7.5 and ×9.5, for MagPI and CSM, respectively, as compared to controls). We confirmed the important role of heterotrophic bacteria in “biostabilisation” and highlighted the interactions between autotrophic and heterotrophic biofilm consortia. This information contributes to the conceptual understanding of the microbial sediment engineering that represents an important ecosystem function and service in aquatic habitats.
Vertical migration of phytoplankton in coastal waters with different UVR transparency
Sabine Gerbersdorf, Hendrik Schubert
Environmental Sciences Europe , 2011, DOI: 10.1186/2190-4715-23-36
Abstract: Chlorophyll a maxima of mainly motile dinoflagellates were observed in situ at all days and at both study sites (open marine, brackish waters), independent on prevailing weather conditions or cDOM concentrations. Phytoplankton migration was triggered solely by irradiance in the 400- to 700-nm wavelength range (PAR) at the particular water depth, irrespective of PAR/UVR ratios and surface UVR (290 to 400 nm), after an illumination period of about 40 min. Interestingly, the PAR tolerance levels of the phytoplankton, which have been lower in cDOM-rich waters, matched their light acclimation values determined by parallel PAM measurements.The response of the phytoplankton to PAR is not a sufficient protection strategy versus increasing UVR levels, which might have wide ecological implications beyond the level of primary producers to impact important ecosystem functions such as the delicate trophic interactions.Over the last decades, there have been increasing reports on the depletion of the stratospheric ozone layer (reviewed in [1]). At first, the thinning ozone layer and ozone holes have been mainly associated with polar regions [2], yet this has been observed in the northern hemisphere too [3-5]. Although the transmission of ultraviolet radiation (UVR) is highly variable due to e.g. solar variability or meteorological conditions, climate change is expected to enhance UVR, consisting of UVA (320 to 400 nm) and UVB (290 to 320 nm), in the long run [6,7]. These reports initiated numerous investigations on possible effects of UV radiation on terrestric and aquatic (marine and freshwater) organisms. In the pelagic zone, an elevated sensitivity of phytoplankton and zooplankton versus UVR could be observed with effects on growth, production, cell biochemistry, ontogeny, genome and mortality (reviewed in [8-10]).Beyond the UVR effects on single organisms, the ecosystem functions of the aquatic habitats may be threatened considering for instance the delicate balance of trophic
A new approach to investigate the interactions between sediment transport and ecotoxicological processes during flood events
Holger Schüttrumpf, Markus Brinkmann, Catrina Cofalla, Roy M Frings, Sabine U Gerbersdorf, Markus Hecker, Sebastian Hudjetz, Ulrike Kammann, Gottfried Lennartz, Sebastian Roger, Andreas Sch?ffer, Henner Hollert
Environmental Sciences Europe , 2011, DOI: 10.1186/2190-4715-23-39
Abstract: The objective of the Floodsearch project - which is funded by the Excellence Initiative of the German Federal and State Governments - is to combine the traditionally separated disciplines of hydraulic engineering and ecotoxicology in a single experimental approach in order to investigate the bioavailability and hazard potential of sediment-bound contaminants to aquatic organisms under simulated flood conditions. Depending on the flow velocity, sediments can either be eroded from or settle down in high and low flow sections in rivers, reservoirs and in harbour basins, respectively. In industrialised regions rivers and estuaries often contain large volumes of old cohesive sediments that can be polluted with toxic agents. Thus, the deposited sediments become a potential risk for the environment due to their ability to bind contaminants [1-3]. The behaviour of such contaminated materials during extreme hydraulic events is of particular interest because toxic fractions of eroded and newly suspended material can be re-suspended, and thus, become bioavailable in the water column again. Former investigations (cf. [4-6]) confirmed the bioavailability of previously immobilised particle-bound contaminants and concluded that re-suspension of sediments may have a major impact on aquatic biota. Unfortunately, no research is available combining hydraulic stresses, sedimentological response and resulting bioavailability of re-suspended contaminated sediments.The Floodsearch project combines hydraulic and ecotoxicological (hydro-toxicological) methodologies in a joint experimental study [7]. The interaction of hydraulic processes, contaminated sediments and aquatic organisms is investigated under controlled laboratory conditions. The main advantage of these experiments is the simulation of the important processes in a single model set-up (hydraulic processes, sediment erosion, transport and deposition, bioavailability of the sediment bound contaminants and the ecotoxicological effec
The nephrogenic potential of the transcription factors osr1, osr2, hnf1b, lhx1 and pax8 assessed in Xenopus animal caps
Christiane Drews, Sabine Senkel, Gerhart U Ryffel
BMC Developmental Biology , 2011, DOI: 10.1186/1471-213x-11-5
Abstract: We have investigated the expression kinetics of the early nephrogenic transcription factors in activin A and retinoic acid treated animal caps and their potential to induce pronephric differentiation. In treated animal caps, expression of osr1, osr2, hnf1b and lhx1 are induced early, whereas pax8 expression occurs later implying an indirect activation. Activin A alone is able to induce osr2 and lhx1 after three hours treatment in animal caps while retinoic acid fails to induce any of these nephrogenic transcription factors. The early expression of the five transcription factors and their interference with pronephros development when overexpressed in embryos suggest that these factors potentially induce nephrogenesis upon expression in animal caps. But no pronephros development is achieved by either overexpression of OSR1, by HNF1B injection with activin A treatment, or the combined application of LHX1 and PAX8, although they influenced the expression of several early nephrogenic transcription factors in some cases. In an additional approach we could show that HNF1B induces several genes important in nephrogenesis and regulates lhx1 expression by an HNF1 binding site in the lhx1 promoter.The early nephrogenic transcription factors play an important role in nephrogenesis, but have no pronephros induction potential upon overexpression in animal caps. They activate transcriptional cascades that partially reflect the gene activation initiated by activin A and retinoic acid. Significantly, HNF1B activates the lhx1 promoter directly, thus extending the known activin A regulation of the lhx1 gene via an activin A responsive element.During vertebrate development three kidney types of increasing complexity (pronephros, mesonephros and metanephros) form successively from the intermediate mesoderm, located between the paraxial mesoderm (developing somites) and the lateral plate [1]. The pronephros is the simplest, functional form of kidney in larval stages of fish and amphibian
4-Nitro-N-phenylbenzenesulfonamide
U. Chaithanya,Sabine Foro,B. Thimme Gowda
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812037798
Abstract: In the title compound, C12H10N2O4S, the dihedral angle between the aromatic rings is 36.19 (18)°. In the crystal, N—H...O hydrogen bonds link the molecules into C(4) chains running along the a axis.
N-(4-Methylphenyl)-2-nitrobenzenesulfonamide
U. Chaithanya,Sabine Foro,B. Thimme Gowda
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812035866
Abstract: In the crystal of the title compound, C13H12N2O4S, the conformation of the N—H bond in the –SO2—NH– segment is syn to the ortho-nitro group in the sulfonyl benzene ring. The molecule is twisted at the S—N bond with a torsion angle of 76.55 (18)°. The dihedral angle between the planes of the rings is 72.64 (8)°. In the crystal, molecules are linked by pairs of N—H...O(S) hydrogen bonds to form inversion dimers.
N-(2-Methylphenyl)-4-nitrobenzenesulfonamide
U. Chaithanya,Sabine Foro,B. Thimme Gowda
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812036331
Abstract: In the title compound, C13H12N2O4S, the dihedral angle between the planes of the rings is 51.11 (10)°. In the crystal, molecules are linked into inversion dimers through pairs of N—H...O(S) hydrogen bonds.
N-(3-Chloro-2-methylphenyl)succinamic acid
B. Thimme Gowda,Sabine Foro,U. Chaithanya
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812022763
Abstract: In the title compound, C11H12ClNO3, the dihedral angle between the benzene ring and the amide group is 44.9 (2)°. In the crystal, molecules form inversion dimers via pairs of O—H...O hydrogen bonds. These dimers are further linked into sheets parallel to (013) via N—H...O hydrogen bonds.
N-(2-Chlorophenyl)-2-nitrobenzenesulfonamide
U. Chaithanya,Sabine Foro,B. Thimme Gowda
Acta Crystallographica Section E , 2012, DOI: 10.1107/s1600536812033107
Abstract: In the title compound, C12H9ClN2O4S, the N—H bond in the –SO2—NH– segment is syn to both the ortho-nitro group in the sulfonylbenzene ring and the ortho-Cl atom in the aniline ring. The molecule is twisted at the S—N bond with a torsion angle of 75.0 (2)°. The dihedral angle between the sulfonylbenzene and aniline rings is 54.97 (11)°. The amide H atom shows bifurcated hydrogen bonding, generating S(7) and C(4) motifs. In the crystal, N—H...O(S) hydrogen bonds link the molecules into chains.
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