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Major Solute (major + solute)
Selected Abstracts,- d -Mannopyranosyl-(1,2)-,- d -glucopyranosyl-(1,2)-glycerate in the thermophilic bacterium Petrotoga miotherma , structure, cellular content and functionFEBS JOURNAL, Issue 12 2007Carla D. Jorge The intracellular accumulation of low molecular mass organic compounds in response to stressful conditions was investigated in the thermophilic bacterium Petrotoga miotherma, a member of the order Thermotogales. This led to the discovery of a new solute, whose structure was established as ,- d -mannopyranosyl-(1,2)-,- d -glucopyranosyl-(1,2)-glycerate (MGG) by MMR spectroscopy and MS. Under optimum growth conditions (3% NaCl; 55 °C), MGG was the major solute [up to 0.6 µmol·(mg protein),1]; ,-glutamate and proline were also present but in minor amounts [below 0.08 µmol·(mg protein),1]. The level of MGG increased notably with the salinity of the growth medium up to the optimum NaCl concentration. At higher NaCl concentrations, however, the level of MGG decreased, whereas the levels of proline and ,-glutamate increased about five-fold and 10-fold, respectively. MGG plays a role during low-level osmotic adaptation of Petrotoga miotherma, whereas ,-glutamate and, to a lesser extent, proline are used for osmoprotection under salt stress. MGG is not part of the cell strategy for coping with heat or oxidative stress. Nevertheless, MGG was an efficient protector of pig heart malate dehydrogenase against heat inactivation and freeze-drying, although mannosylglycerate was better. This is the first report on the occurrence of MGG in living systems. [source] The osmotic stress tolerance of basidiomycetous yeastsFEMS YEAST RESEARCH, Issue 4 2010Obakeng M. Tekolo Abstract The growth and accumulation of intracellular polyols at reduced water activity (aw) were studied in 40 basidiomycetous yeast strains. The growth of most strains showed greater tolerance to NaCl than sorbitol at the same aw. No strain was able to grow below 0.90aw. 13C nuclear magnetic resonance spectroscopy revealed that glycerol was the major solute accumulated intracellularly by all the yeasts when grown to 0.96aw (NaCl). Arabitol or mannitol was also accumulated in some yeasts, whereas a few only accumulated glycerol. Analysis of six yeasts in detail revealed that the intracellular glycerol concentrations of five yeasts increased significantly when grown at 0.96aw (NaCl or sorbitol) compared with growth at 0.998aw. Arabitol and mannitol concentrations also increased, but not to the same degree. Intracellular potassium concentrations decreased when grown at 0.96aw (NaCl or sorbitol) and sodium increased, but only when grown at 0.96aw (NaCl). The survival of nine strains was evaluated in soil cultures and it was found that all grew at 100% field capacity, whereas at lower field capacity, only some strains grew or survived. The growth of basidiomycetous yeasts appears to be more sensitive to reduced aw than ascomycetous yeasts. [source] Temporal and spatial variability of cation and silica export in an alpine watershed, Emerald Lake, CaliforniaHYDROLOGICAL PROCESSES, Issue 10 2004T. Meixner Abstract A reaction set of possible mineral weathering reactions is proposed to explain observed cation and silica export for the Emerald Lake watershed, a small Sierra Nevada, California catchment. The reaction set was calculated through a stoichiometric mole-balance method, using a multiyear record of stream flow and snowpack chemical analyses and site-specific mineral compositions. Reaction-set calculations were intended to explore how the processes controlling stream cation and silica export depend on differing bedrock mineralogy across the catchment as snowmelt and runoff patterns change over the year. Different regions within the watershed can be differentiated by lake inflow subdrainages, each exhibiting different stream-flow chemistry and calculated weathering stoichiometry, indicating that different silica and cation generation processes are dominant in wet steep portions of the catchment. Short-term differences in stream concentrations were assumed to reflect ion exchange equilibria and rapid biological processes, whereas long-term persistent stream concentration differences in different areas of the catchment were assumed to reflect spatial variability in mineral weathering stoichiometry. Mineralogical analyses of rock samples from the watershed provided site-specific chemical compositions of major mineral species for reaction calculations. Reaction sets were evaluated by linear regression of calculated versus observed differences between snowmelt and stream-flow chemistry and by a combined measure. Initially, single weathering reactions were balanced and evaluated to determine the reactions that best explained observed stream chemical export. Next, reactions were combined, using mineral compositions from different rock types to estimate the dependence of ion fluxes on lithology. The seasonal variability of major solute calculated fluxes is low, approximately one order of magnitude, relative to the observed three orders of magnitude variability in basin discharge. Reaction sets using basin-averaged lithology and Aplite lithologies gave superior explanations of stream chemical composition. Copyright © 2004 John Wiley & Sons, Ltd. [source] Hydrology and water quality in two mountain basins of the northeastern US: assessing baseline conditions and effects of ski area development,,HYDROLOGICAL PROCESSES, Issue 12 2007Beverley Wemple Abstract Mountain regions throughout the world face intense development pressures associated with recreational and tourism uses. Despite these pressures, much of the research on bio-geophysical impacts of humans in mountain regions has focused on the effects of natural resource extraction. This paper describes findings from the first 3 years of a study examining high elevation watershed processes in a region undergoing alpine resort development. Our study is designed as a paired-watershed experiment. The Ranch Brook watershed (9·6 km2) is a relatively pristine, forested watershed and serves as the undeveloped ,control' basin. West Branch (11·7 km2) encompasses an existing alpine ski resort, with approximately 17% of the basin occupied by ski trails and impervious surfaces, and an additional 7% slated for clearing and development. Here, we report results for water years 2001,2003 of streamflow and water quality dynamics for these watersheds. Precipitation increases significantly with elevation in the watersheds, and winter precipitation represents 36,46% of annual precipitation. Artificial snowmaking from water within West Branch watershed currently augments annual precipitation by only 3,4%. Water yield in the developed basin exceeded that in the control by 18,36%. Suspended sediment yield was more than two and a half times greater and fluxes of all major solutes were higher in the developed basin. Our study is the first to document the effects of existing ski area development on hydrology and water quality in the northeastern US and will serve as an important baseline for evaluating the effects of planned resort expansion activities in this area. Published in 2007 by John Wiley & Sons, Ltd. [source] Simultaneous measurement of water flow velocity and solute transport in xylem and phloem of adult plants of Ricinus communis over a daily time course by nuclear magnetic resonance spectrometryPLANT CELL & ENVIRONMENT, Issue 5 2001A. D. Peuke ABSTRACT A new method for simultaneously quantifying rates of flow in xylem and phloem using the FLASH imaging capabilities of nuclear magnetic resonance (NMR) spectrometry was applied in this study. The method has a time resolution of up to 4 min (for the xylem) and was used to measure the velocity of flows in phloem and xylem for periods of several hours to days. For the first time, diurnal time course measurements of flow velocities and apparent volume flows in phloem and xylem in the hypocotyl of 40-d-old Ricinus communis L were obtained. Additional data on gas exchange and the chemical composition of leaves, xylem and phloem sap were used to assess the role of leaves as sinks for xylem sap and sources for phloem. The velocity in the phloem (0·250 ± 0·004 mm s,1) was constant over a full day and not notably affected by the light/dark cycle. Sucrose was loaded into the phloem and transported at night, owing to degradation of starch accumulated during the day. Concentrations of solutes in the phloem were generally less during the night than during the day but varied little within either the day or night. In contrast to the phloem, flow velocities in the xylem were about 1·6-fold higher in the light (0·401 ± 0·004 mm s,1) than in the dark (0·255 ± 0·003 mm s,1) and volume flow varied commensurately. Larger delays were observed in changes to xylem flow velocity with variation in light than in gas exchange. The relative rates of solute transport during day and night were estimated on the basis of relative flow and solute concentrations in xylem and phloem. In general, changes in relative flow rates were compensated for by changes in solute concentration during the daily light/dark cycle. However, the major solutes (K+, NO3,) varied appreciably in relative concentrations. Hence the regulation of loading into transport systems seems to be more important to the overall process of solute transport than do changes in mass flow. Due to transport behaviour, the chemical composition of leaves varied during the day only with regard to starch and soluble carbohydrates. [source] | ||||||||||