3 results
Now showing1 - 3 of 3
- Some of the metrics are blocked by yourconsent settings
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: 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 , 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