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Item type:Publication, Access status: without files , Measuring bacterial activity and community composition at high hydrostatic pressure using a novel experimental approach: A pilot studyIn this pilot study, we describe a high-pressure incubation system allowing multiple subsampling of a pressurized culture without decompression. The system was tested using one piezophilic (Photobacterium profundum), one piezotolerant (Colwellia maris) bacterial strain and a decompressed sample from the Mediterranean deep sea (3044 m) determining bacterial community composition, protein production (BPP) and cell multiplication rates (BCM) up to 27 MPa. The results showed elevation of BPP at high pressure was by a factor of 1.5 ± 1.4 and 3.9 ± 2.3 for P. profundum and C. maris, respectively, compared to ambient-pressure treatments and by a factor of 6.9 ± 3.8 fold in the field samples. In P. profundum and C. maris, BCM at high pressure was elevated (3.1 ± 1.5 and 2.9 ± 1.7 fold, respectively) compared to the ambient-pressure treatments. After 3 days of incubation at 27 MPa, the natural bacterial deep-sea community was dominated by one phylum of the genus Exiguobacterium, indicating the rapid selection of piezotolerant bacteria. In future studies, our novel incubation system could be part of an isopiestic pressure chain, allowing more accurate measurement of bacterial activity rates which is important both for modeling and for predicting the efficiency of the oceanic carbon pump.Publicationtype: Journal Article151 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Effect of high pressure on hydrocarbon-degrading bacteria(Springer, 2014-10-15); ; ; ; The blowout of the Deepwater Horizon in the Gulf of Mexico in 2010 occurred at a depth of 1500 m, corresponding to a hydrostatic pressure of 15 MPa. Up to now, knowledge about the impact of high pressure on oil-degrading bacteria has been scarce. To investigate how the biodegradation of crude oil and its components is influenced by high pressures, like those in deep-sea environments, hydrocarbon degradation and growth of two model strains were studied in high-pressure reactors. The alkane-degrading strain Rhodococcus qingshengii TUHH-12 grew well on n-hexadecane at 15 MPa at a rate of 0.16 h−1, although slightly slower than at ambient pressure (0.36 h−1). In contrast, the growth of the aromatic hydrocarbon degrading strain Sphingobium yanoikuyae B1 was highly affected by elevated pressures. Pressures of up to 8.8 MPa had little effect on growth of this strain. However, above this pressure growth decreased and at 12 MPa or more no more growth was observed. Nevertheless, S. yanoikuyae continued to convert naphthalene at pressure >12 MPa, although at a lower rate than at 0.1 MPa. This suggests that certain metabolic functions of this bacterium were inhibited by pressure to a greater extent than the enzymes responsible for naphthalene degradation. These results show that high pressure has a strong influence on the biodegradation of crude oil components and that, contrary to previous assumptions, the role of pressure cannot be discounted when estimating the biodegradation and ultimate fate of deep-sea oil releases such as the Deepwater Horizon eventPublicationtype: Journal ArticleScopus© Citations 47 479 354 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Intermittent riverine resuspension : effects on phosphorus transformations and heterotrophic bacteria(Wiley-Blackwell, 2013-03-04); ; ; ; Intermittent riverine resuspension (IRR), a common phenomenon, was applied to investigate its effects on sedimentary resources availability and bacteria in the water column. This lab experiment used organic-rich lowland river sediment in a newly designed erosion chamber, the Benthic Water Column Simulator, generating well-defined ratios of shear velocity u* to turbulence intensity. Eight consecutive resuspension events, 1-8, were initiated at u* = 1.1 cm s-1. Sedimentary and phosphorus entrainment decreased from 20.4 g m-2 h-1 and 111.6 mg m-2 h-1 at event 1 to 1.31 g m-2 h-1 and 18.7 mg m-2 h-1 at event 8, suggesting an exhaustion of particulate and dissolved sediment constituents. Entrainment of particle-associated (PA) bacteria (132.7 × 109-251.1 × 109 cells m-2 h-1) was strongly correlated to that of particles. Free-living (FL) bacteria (-27.6 × 109-36.4 × 109 cells m-2 h-1) were fractionally entrained. Numbers of PA bacteria remained low after each event, whereas those of FL bacteria strongly increased 5-15 h after an event because of growth due to increased availability of dissolved organic carbon and inorganic nutrients following each event. FL bacteria community structure also changed during IRR. The systematic changes over consecutive IRR cycles show a strong effect in all considered parameters that elude the typical single-event, steady-state experiments. IRR should thus be considered in two respects: experimental protocols on riverine water quality should be revised. In ecosystem modeling, IRR should be considered to better predict extent and effect of resuspension. Only IRR adequately reflects the natural interplay between hydrodynamics and organisms in rivers.Publicationtype: Journal Article113 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Influence of mixing and shear stress on Chlorella vulgaris, Scenedesmus obliquus, and Chlamydomonas reinhardtii(Springer, 2012-08-04); ; ; ; Photosynthetic activity (PA) and growth of different microalgae species (Chlorella vulgaris, Scenedesmus obliquus, and Chlamydomonas reinhardtii) depends in addition to other factors on mixing (tip speed) and shear stress (friction velocity) and was studied in a stirring tank (microcosm). In order to detect cause-effect relationships for an increase in photosynthetic activity, experiments were conducted under different pH values (6. 0-8. 5) and CO2 concentrations (0. 038 and 4 % (v/v)). The PA was determined as the effective quantum yield by pulse amplitude modulation during a stepwise increase of the tip speed from 0 to 589 cm s-1 (friction velocity: 0-6. 05 cm s-1) in short-term experiments. The increase caused a distinctive pattern of PA of each species. Compared to 0 cm s-1, C. vulgaris and S. obliquus showed a 4. 0 and 4. 8 % higher PA at the optimum tip speed of 126 cm s-1 (friction velocity of 2. 09 cm s-1) and a 48 and 71 % higher growth, respectively. At 203 cm s-1, the PA dropped to the value of the unstirred control, while at 589 cm s-1, the PA decreased of up to 7 and 8 %. In contrast, C. reinhardtii showed 7 % stronger growth at 126 cm s-1, while the PA decreased about 15 % at an increase of tip speed to 589 cm s-1. For all investigated microalgae, the pattern of PA and higher growth was not only explained by the main contributing factors like light supply, nutrient supply, and overcoming diffusion gradients. The results indicate that hydrodynamic forces have a stimulating effect on the physiological processes within the cells.Publicationtype: Journal Article53 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Transport of persistent organic pollutants by organo-mineral aggregates (OMAs) in the Lisboa-Setúbal Canyon systemIn this work we investigate the role of organo-mineral aggregates (OMAs) in the transport and deposition of persistent organic pollutants in the Lisboa-Setúbal Canyon system. OMAs are more easily remobilized than the underlying sediment surface, and are easily transported in the benthic boundary layer. Since aquatic sediments act as sinks for hydrophobic organic contaminants, OMAs must be a factor in the lateral transport of organic contaminants. Submarine canyons further facilitate the flux of these contaminants from source to deep-sea. Our results show that the difference between the behavior of the OMAs and the underlying superficial sediment is very important in the transport of carbon and persistent organic pollutants to the deep-sea. The Lisboa-Setúbal Canyon system is clearly exporting organic pollutants to the deep-sea through the transport of OMAs.Publicationtype: Journal Article17 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Impacts on supply chain management and its flexibility through component commonality and postponementThe current trend to shortening product lifecycles and the uncertainty in the dynamics of global markets force companies to increase flexibility in supply chain management. In spite of the importance of the interdependencies between product design and supply chains, the contribution of product design principles to supply chain management flexibility has not been, so far, sufficiently investigated in the scientific literature. This research will show the positive benefits of combining postponement and component commonality in the automotive industry. Insights from literature and a case study are combined to evaluated the impacts on the supply chain variables coordination, collaboration and configuration and its flexibility. The notion of this work is to convince companies in making combined component commonality and postponement decisions rather than separate ones.Publicationtype: Conference Paper29 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Hydrostatic pressure affects physiology and community structure of marine bacteria during settling to 4000 m : an experimental approachThe response of 5 strains of shallow-water microbes to changing hydrostatic pressure was explored in a pressurized microcosm setup, simulating a sinking at 1000 m d-1 from surface waters to 4000 m depth in an isothermal ocean. Technology and methods combined a new, computer- controlled pressure laboratory with classical and new genetic tools to evaluate pressure responses of selected bacterial strains. Size, number, growth and species composition were obtained in a time series pattern under regular, non-saturating feeding. Planned as an initial step in a quest for quantifying the role of hydrostatic pressure in observed oceanic microbial distributions, results from this study indicate that selected bacterial strains from the surface respond individually to pressure exposure. A strong physiological response led to reduced bacterial numbers of all strains at 4000 m depth, a result corroborated elsewhere in the literature. Unexpectedly, pressure changes (during sinking) generated depth-specific maxima and minima in number of the selected strains, not seen in the ambient pressure control. A reshuffling of species and changes in sizes of all strains tested occurred in the pressurized treatment. Therefore, time series experiments with non-intrusive sampling features rather than end-member experiments become mandatory to document physiological responses to pressure. Our results, together with recent findings on pressure-related effects on microbial growth and community structure in the deep-sea, indicate that estimates of microbial organic matter turnover in the deep-sea-not taking pressure-related effects into account-need to be revisited. © Inter-Research 2009.Publicationtype: Journal Article74 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: with files , Commentary on 'On generating uniform bottom shear stress. Part I: A quantitative study of microcosm chambers'(2009)Commentary on a published article, which used a numerical model to evaluate an experimentally fully calibrated microcosm chamber.Publicationtype: Working Paper377 199 - Some of the metrics are blocked by yourconsent settings
Item type:Publication, Access status: without files , Pressure effects on the biological degradation of organo-mineral aggregates in submarine canyons(Elsevier, 2007-12-07); 4