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Air Saturation (air + saturation)
Selected AbstractsIsolation and gene quantification of heterotrophic N2 -fixing bacterioplankton in the Baltic SeaENVIRONMENTAL MICROBIOLOGY, Issue 1 2007Kjärstin H. Boström Summary Cyanobacteria are regarded as the main N2 -fixing organisms in marine waters. However, recent clone libraries from various oceans show a wide distribution of the dinitrogenase reductase gene (nifH) originating from heterotrophic bacterioplankton. We isolated heterotrophic N2 -fixing bacteria from Baltic Sea bacterioplankton using low-nitrogen plates and semi-solid diazotroph medium (SSDM) tubes. Isolates were analysed for the nitrogenase (nifH) gene and active N2 fixation by nested polymerase chain reaction (PCR) and acetylene reduction respectively. A primer-probe set targeting the nifH gene from a , - proteobacterial isolate, 97% 16S rDNA similarity to Pseudomonas stutzeri, was designed for measuring in situ dynamics using quantitative real-time PCR. This nifH gene sequence was detected at two of 11 stations in a Baltic Proper transect at abundances of 3 × 104 and 0.8 × 103 copies per litre seawater respectively. Oxygen requirements of isolates were examined by cultivation in SSDM tubes where oxygen gradients were determined with microelectrodes. Growth, and thereby N2 fixation, was observed as horizontal bands formed at oxygen levels of 0,6% air saturation. The apparent microaerophilic or facultative anaerobic nature of the isolates explains why the SSDM approach is the most appropriate isolation method. Our study illustrates how combined isolation, functional analyses and in situ quantification yielded insights into the oxygen requirements of heterotrophic N2 -fixing bacterioplankton isolates, which were confirmed to be present in situ. [source] Effect of degree of fluid saturation on transport coefficients in disturbed soilsEUROPEAN JOURNAL OF SOIL SCIENCE, Issue 1 2004A. Tuli Summary To improve the predictive capability of transport models in soils we need experimental data that improve their understanding of properties at the scale of pores, including the effect of degree of fluid saturation. All transport occurs in the same soil pore space, so that one may intuitively expect a link between the different transport coefficients and key geometrical characteristics of the pores such as tortuosity and connectivity, and pore-size distribution. To understand the combined effects of pore geometry and pore-size distribution better, we measured the effect of degree of water saturation on hydraulic conductivity and bulk soil electrical conductivity, and of degree of air saturation on air conductivity and gaseous diffusion for a fine sand and a sandy loam soil. To all measured data were fitted a general transport model that includes both pore geometry and pore-size distribution parameters. The results show that both pore geometry and pore-size distribution determine the functional relations between degree of saturation, hydraulic conductivity and air conductivity. The control of pore size on convective transport is more for soils with a wider pore-size distribution. However, the relative contribution of pore-size distribution is much larger for the unsaturated hydraulic conductivity than for gaseous phase transport. For the other transport coefficients, their saturation dependency could be described solely by the pore-geometry term. The contribution of the latter to transport was much larger for transport in the air phase than in the water phase, supporting the view that connectivity dominates gaseous transport. Although the relation between effective fluid saturation and all four relative transport coefficients for the sand could be described by a single functional relation, the presence of a universal relationship between fluid saturation and transport for all soils is doubtful. [source] IMAGING OF OXYGEN DYNAMICS WITHIN THE ENDOLITHIC ALGAL COMMUNITY OF THE MASSIVE CORAL PORITES LOBATA,JOURNAL OF PHYCOLOGY, Issue 3 2008Michael Kühl We used transparent planar oxygen optodes and a luminescence lifetime imaging system to map (at a pixel resolution of <200 ,m) the two-dimensional distribution of O2 within the skeleton of a Porites lobata colony. The O2 distribution was closely correlated to the distribution of the predominant endolithic microalga, Ostreobium quekettii Bornet et Flahault that formed a distinct green band inside the skeleton. Oxygen production followed the outline of the Ostreobium band, and photosynthetic O2 production was detected at only 0.2 ,mol photons m,2 · s,1, while saturation occurred at ,37 ,mol photons m,2 · s,1. Oxygen levels varied from ,60% to 0% air saturation in the illuminated section of the coral skeleton in comparison to the darkened section. The O2 production within the Ostreobium band was lower in the region below the upward facing surface of the coral and elevated on the sides. Oxygen consumption in darkness was also greatest within the Ostreobium zone, as well as in the white skeleton zone immediately below the corallites. The rate of O2 depletion was not constant within zones and between zones, showing pronounced heterogeneity in endolithic respiration. When the coral was placed in darkness after a period of illumination, O2 levels declined by 50% within 20 min and approached steady-state after 40,50 min in darkness. Our study demonstrates the use of an important new tool in endolith photobiology and presents the first data of spatially resolved O2 concentration and its correlation to the physical structures and specific zones responsible for O2 production and consumption within the coral skeleton. [source] Changes in ventral head width, a discriminating shape factor among African cichlids, can be induced by chronic hypoxiaBIOLOGICAL JOURNAL OF THE LINNEAN SOCIETY, Issue 3 2009HENDRIKUS A. RUTJES A massive enlargement of the gill surface proved to be an important factor in the hypoxia survival of young cichlids. Because the heads of cichlids are densely packed with structures related to both feeding and breathing, we hypothesized that the extra space needed for gill enlargement requires such large structural reorganizations that outer head shape is affected. We used a three-dimensional model to describe changes in the outer head shape of cichlids. Broods of cichlids of different phylogenetic lineages, habitats, and trophic specialization were split and raised at either 10% or 80,90% air saturation. Despite the above-mentioned differences between the species that were used, all hypoxia raised groups showed similar volume enlargements. Volume increases were most prominent in the ventral suspensorial and ventral opercular subcompartments. A relation with the enlarged gills of hypoxia raised fish is likely because the gills are mainly located in these compartments. The differences in ventral width correspond to those found in other studies comprising a wide variety of genotypic and phenotypic variations. The present study shows that such variation in the ventral width is conceivable by phenotypic plasticity alone. © 2009 The Linnean Society of London, Biological Journal of the Linnean Society, 2009, 98, 608,619. [source] Optimization of Rosmarinic Acid Production by Lavandula vera MM Plant Cell Suspension in a Laboratory BioreactorBIOTECHNOLOGY PROGRESS, Issue 2 2005Atanas I. Pavlov The all-round effect of dissolved oxygen concentration, agitation speed, and temperature on the rosmarinic acid production by Lavandula veraMM cell suspension was studied in a 3-L laboratory bioreactor by means of the modified Simplex method. Polynomial regression models were elaborated for description of the process of rosmarinic acid production (Y) in the bioreactor as a consequence of the variation of the dissolved oxygen (X1) concentration between 10% and 50%; agitation (X2) between 100 and 400 rpm; and temperature (X3) between 22 and 30 °C. The optimization made it possible to establish the optimal conditions for the biosynthesis of rosmarinic acid by L. veraMM: dissolved oxygen (X1*), 50% of air saturation; agitation (X2*), 400 rpm; and temperature (X3*), 29.9 °C, where maximal yield (Ymax) of 3489.4 mg/L of rosmarinic acid was achieved (2 times higher compared with the shake-flasks cultivation). [source] Effects of Three-Dimensional Culturing on Osteosarcoma Cells Grown in a Fibrous Matrix: Analyses of Cell Morphology, Cell Cycle, and ApoptosisBIOTECHNOLOGY PROGRESS, Issue 5 2003Chunnuan Chen Osteosarcoma cells were cultured in stirred tank bioreactors with either a fibrous matrix or nonporous microcarriers to study the environmental effects on cell growth, morphology, cell cycle, and apoptosis. Cell cycle and apoptosis were analyzed using flow cytometry and visualized using confocal laser scanning microscopy and fluorescence microscopy. The three-dimensional (3-D) fibrous culture had better cell growth and higher metabolic rates than the two-dimensional (2-D) microcarrier culture because cells in the fibrous matrix were protected from shear stress and had lower apoptosis and cell death even under suboptimal conditions (e.g., nutrient depletion). The polyester fibrous matrix used in this study also exhibited the capability of selectively retaining viable and nonapoptotic cells and disposing apoptotic and nonviable cells. Consequently, very few apoptotic cells were found in the fibrous matrix even in the long-term (1 month) T-flask culture. In the continuous culture with packed fibrous matrixes for cell support, most cells were arrested in the G1/G0 phase after 4 days. Decreasing the dissolved oxygen level from 60 to 10% air saturation did not significantly change cell cycle and apoptosis, which remained low at ,15%. These results could explain why the fibrous bed bioreactor had good long-term stability and was advantageous for production of non-growth-associated proteins by animal cell cultures. [source] | ||||||||||