scholarly journals Ice nucleators, bacterial cells and <i>Pseudomonas syringae</i> in precipitation at Jungfraujoch

2017 ◽  
Vol 14 (5) ◽  
pp. 1189-1196 ◽  
Author(s):  
Emiliano Stopelli ◽  
Franz Conen ◽  
Caroline Guilbaud ◽  
Jakob Zopfi ◽  
Christine Alewell ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Dynamic Range ◽  
Water Cycle ◽  
Bacterial Cells ◽  
New Host ◽  
Wind Speeds ◽  
Ice Nucleators ◽  
Order Of Magnitude ◽  
Airborne Microorganism ◽  
A Minor

Abstract. Ice nucleation is a means by which the deposition of an airborne microorganism can be accelerated under favourable meteorological conditions. Analysis of 56 snow samples collected at the high-altitude observatory Jungfraujoch (3580 m a.s.l.) revealed an order-of-magnitude-larger dynamic range of ice-nucleating particles active at −8 °C (INPs−8) compared to the total number of bacterial cells (of which on average 60 % was alive). This indicates a shorter atmospheric residence time for INPs−8. Furthermore, concentrations of INPs−8 decreased much faster, with an increasing fraction of water precipitated from the air mass prior to sampling, than the number of total bacterial cells. Nevertheless, at high wind speeds (> 50 km h−1) the ratio of INPs−8 to total bacterial cells largely remained in a range between 10−2 and 10−3, independent of prior precipitation, likely because of recent injections of particles in regions upwind. Based on our field observations, we conclude that ice nucleators travel shorter legs of distance with the atmospheric water cycle than the majority of bacterial cells. A prominent ice-nucleating bacterium, Pseudomonas syringae, has been previously supposed to benefit from this behaviour as a means to spread via the atmosphere and to colonise new host plants. Therefore, we targeted this bacterium with a selective cultivation approach. P. syringae was successfully isolated for the first time at such an altitude in 3 of 13 samples analysed. Colony-forming units of this species constituted a minor fraction (10−4) of the numbers of INPs−8 in these samples. Overall, our findings expand the geographic range of habitats where this bacterium has been found and corroborate theories on its robustness in the atmosphere and its propensity to spread to colonise new habitats.

scholarly journals Ice nucleators have shorter persistence in the atmosphere than other airborne bacteria

2016 ◽  
Author(s):  
Emiliano Stopelli ◽  
Franz Conen ◽  
Caroline Guilbaud ◽  
Jakob Zopfi ◽  
Christine Alewell ◽  
...  
Keyword(s):  
Pseudomonas Syringae ◽  
Dynamic Range ◽  
Water Cycle ◽  
Bacterial Cells ◽  
Wind Speeds ◽  
Colony Forming Units ◽  
Ice Nucleators ◽  
Order Of Magnitude ◽  
Airborne Microorganism ◽  
A Minor

Abstract. Ice nucleation is a means by which the deposition of an airborne microorganism can be accelerated under favourable meteorological conditions. Analysis of 56 snow samples collected at the high altitude observatory Jungfraujoch (3580 m a.s.l.) revealed an order of magnitude larger dynamic range of ice nucleating particles active at −8 °C (INPs−8) compared to the total number of bacterial cells (60 % was on average living). This indicates a shorter atmospheric residence time for INPs−8. Furthermore, concentrations of INPs-8 decreased much faster, with an increasing fraction of water precipitated from the air mass prior to sampling, than the number of total bacterial cells. Nevertheless, at high wind speeds (> 50 km h−1) the ratio of INPs−8 to total bacterial cells largely remained in a range between 10−2 to 10−3, independent of prior precipitation, perhaps because of recent injections of particles in regions upwind. Based on our field observations, we conclude that ice nucleators travel shorter legs of distance with the atmospheric water cycle than the majority of bacterial cells. Pseudomonas syringae, a prominent ice nucleating bacterium, was successfully isolated from 3 of 13 samples analysed. Colony forming units of this species constituted a minor fraction (10−4) of the numbers of INPs−8 in these samples. Overall, our findings expand the geographic range of habitats where this bacterium has been found and corroborates theories on its robustness in the atmosphere and its propensity to spread and to colonise new plants.

scholarly journals Discharge of debris from ice at the margin of the Greenland ice sheet

2002 ◽  
Vol 48 (161) ◽  
pp. 192-198 ◽  
Author(s):  
Peter G. Knight ◽  
Richard I. Waller ◽  
Carrie J. Patterson ◽  
Alison P. Jones ◽  
Zoe P. Robinson
Keyword(s):  
Ice Sheet ◽  
Greenland Ice Sheet ◽  
High Rate ◽  
Outlet Glacier ◽  
Tidewater Glaciers ◽  
Sediment Production ◽  
Basal Ice ◽  
Order Of Magnitude ◽  
Sediment Transfer ◽  
A Minor

AbstractSediment production at a terrestrial section of the ice-sheet margin in West Greenland is dominated by debris released through the basal ice layer. The debris flux through the basal ice at the margin is estimated to be 12–45 m3 m−1 a−1. This is three orders of magnitude higher than that previously reported for East Antarctica, an order of magnitude higher than sites reported from in Norway, Iceland and Switzerland, but an order of magnitude lower than values previously reported from tidewater glaciers in Alaska and other high-rate environments such as surging glaciers. At our site, only negligible amounts of debris are released through englacial, supraglacial or subglacial sediment transfer. Glaciofluvial sediment production is highly localized, and long sections of the ice-sheet margin receive no sediment from glaciofluvial sources. These findings differ from those of studies at more temperate glacial settings where glaciofluvial routes are dominant and basal ice contributes only a minor percentage of the debris released at the margin. These data on debris flux through the terrestrial margin of an outlet glacier contribute to our limited knowledge of debris production from the Greenland ice sheet.

Viability and respiratory activity ofPseudomonas syringaecells starved in buffer

1995 ◽  
Vol 41 (4-5) ◽  
pp. 372-377 ◽  
Author(s):  
João P. S. Cabral
Keyword(s):  
Oxygen Consumption ◽  
Electron Transport ◽  
Pseudomonas Syringae ◽  
Respiratory Activity ◽  
Bacterial Cells ◽  
Intact Cells ◽  
Rate Of Oxygen Consumption ◽  
Metabolic Activities ◽  
Different Levels ◽  
Number Of Cells

Pseudomonas syringae cells starved in buffer released orcinol-reactive molecules and materials that absorbed ultraviolet light. The number of cells culturable in nutrient medium decreased more rapidly than the number of intact particles determined by microscopy. The results suggested that starvation resulted in the lysis of an increasing number of cells, and that a fraction of the intact particles were not culturable. Starvation also resulted in a decrease in the rate of oxygen consumption with acetate, glycerol, and succinate, but at different levels. Whereas the respiration of acetate and glycerol decreased concomitantly with culturability, the respiration of succinate decreased to levels similar to the concentration of intact cells, suggesting that all intact particles respired the succinate, but only the culturable cells respired the acetate and glycerol. The results suggest that measuring the activity of the electron-transport system can overestimate the viability of starved bacterial cells, and that complex metabolic activities such as the respiration of acetate and glycerol are probably better suited for the evaluation of this parameter.Key words: Pseudomonas syringae, starvation, culturability, viability, respiration.

scholarly journals Effects of atmospheric conditions on ice nucleation activity of <i>Pseudomonas</i>

2012 ◽  
Vol 12 (22) ◽  
pp. 10667-10677 ◽  
Author(s):  
E. Attard ◽  
H. Yang ◽  
A.-M. Delort ◽  
P. Amato ◽  
U. Pöschl ◽  
...  
Keyword(s):  
Environmental Factors ◽  
Pseudomonas Syringae ◽  
Ice Nucleation ◽  
Acidic Ph ◽  
Bacterial Cells ◽  
Atmospheric Conditions ◽  
Ice Nucleation Protein ◽  
Ice Melt ◽  
Nucleation Activity ◽  
Ice Nucleation Activity

Abstract. Although ice nuclei from bacterial origin are known to be efficient at the highest temperatures known for ice catalysts, quantitative data are still needed to assess their role in cloud processes. Here we studied the effects of three typical cloud conditions (i) acidic pH (ii) NO2 and O3 exposure and (iii) UV-A exposure on the ice nucleation activity (INA) of four Pseudomonas strains. Three of the Pseudomonas syringae strains were isolated from cloud water and the phyllosphere and Pseudomonas fluorescens strain CGina-01 was isolated from Antarctic glacier ice melt. Among the three conditions tested, acidic pH caused the most significant effects on INA likely due to denaturation of the ice nucleation protein complex. Exposure to NO2 and O3 gases had no significant or only weak effects on the INA of two P. syringae strains whereas the INA of P. fluorescens CGina-01 was significantly affected. The INA of the third P. syringae strain showed variable responses to NO2 and O3 exposure. These differences in the INA of different Pseudomonas suggest that the response to atmospheric conditions could be strain-specific. After UV-A exposure, a substantial loss of viability of all four strains was observed whereas their INA decreased only slightly. This corroborates the notion that under certain conditions dead bacterial cells can maintain their INA. Overall, the negative effects of the three environmental factors on INA were more significant at the warmer temperatures. Our results suggest that in clouds where temperatures are near 0 °C, the importance of bacterial ice nucleation in precipitation processes could be reduced by some environmental factors.

The stress generated in a non-dilute suspension of elongated particles by pure straining motion

1971 ◽  
Vol 46 (4) ◽  
pp. 813-829 ◽  
Author(s):  
G. K. Batchelor
Keyword(s):  
Theoretical Formula ◽  
Rigid Sphere ◽  
Cross Sectional ◽  
Outer Flow ◽  
Rigid Particles ◽  
Bulk Stress ◽  
Order Of Magnitude ◽  
Sectional Plane ◽  
Dilute Suspension ◽  
A Minor

In a pure straining motion, elongated rigid particles in suspension are aligned parallel to the direction of the greatest principal rate of extension, provided the effect of Brownian motion is weak. If the suspension is dilute, in the sense that the particles are hydrodynamically independent, each particle of length 2l makes a contribution to the bulk deviatoric stress which is of roughly the same order of magnitude as that due to a rigid sphere of radius l. The fractional increase in the bulk stress due to the presence of the particles is thus equal to the concentration by volume multiplied by a factor of order l2/b2, where 2b is a measure of the linear dimensions of the particle cross-section. This suggests that the stress due to the particles might be relatively large, for volume fractions which are still small, with interesting implications for the behaviour of polymer solutions. However, dilute-suspension theory is not applicable in these circumstances, and so an investigation is made of the effect of interactions between particles. It is assumed that, when the average lateral spacing of particles (h) satisfies the conditions b [Lt ] h [Lt ] l, the disturbance velocity vector is parallel to the particles and varies only in the cross-sectional plane. The velocity near a particle is found to have the same functional form as for an isolated particle, and the modification to the outer flow field for one particle is determined by replacing the randomly placed neighbouring particles by an equivalent cylindrical boundary. The resulting expression for the contribution to the bulk stress due to the particles differs from that for a dilute suspension only in a minor way, viz. by the replacement of log 2l/b by log h/b, and the above suggestion is confirmed. The relative error in the expression for the stress is expected to be of order (log h/b)−1. Some recent observations by Weinberger of the stress in a suspension of glass-fibre particles for which 2l/h = 7·4 and h/2b = 7·8 do show a particle stress which is much larger than the ambient-fluid stress, although the theoretical formula is not accurate under these conditions.

scholarly journals Rapid detection of cytochrome cd1-containing nitrite reductase encoding gene nirS of denitrifying bacteria with loop-mediated isothermal amplification assay

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Xuzhi Zhang ◽  
Qianqian Yang ◽  
Qingli Zhang ◽  
Xiaoyu Jiang ◽  
Xiaochun Wang ◽  
...  
Keyword(s):  
Nitrite Reductase ◽  
Genomic Dna ◽  
Limit Of Detection ◽  
Lamp Assay ◽  
Denitrifying Bacteria ◽  
Isothermal Amplification ◽  
Target Sequence ◽  
Bacterial Cells ◽  
Loop Mediated Isothermal Amplification ◽  
Order Of Magnitude

Abstract The cytochrome cd1-containing nitrite reductase, nirS, plays an important role in biological denitrification. Consequently, investigating the presence and abundance of nirS is a commonly used approach to understand the distribution and potential activity of denitrifying bacteria, in addition to denitrifier communities. Herein, a rapid method for detecting nirS gene with loop-mediated isothermal amplification (LAMP) was developed, using Pseudomonas aeruginosa PAO1 (P. aeruginosa PAO1) as model microorganism to optimize the assay. The LAMP assay relied on a set of four primers that were designed to recognize six target sequence sites, resulting in high target specificity. The limit of detection for the LAMP assay under optimized conditions was 1.87 pg/reaction of genomic DNA, which was an order of magnitude lower than that required by conventional PCR assays. Moreover, it was validated that P. aeruginosa PAO1 cells as well as genomic DNA could be directly used as template. Only 1 h was needed from the addition of bacterial cells to the reaction to the verification of amplification success. The nirS gene of P. aeruginosa PAO1 in spiked seawater samples could be detected with both DNA-template based LAMP assay and cell-template based LAMP assay, demonstrating the practicality of in-field use.

scholarly journals Cerebrospinal fluid ceftazidime kinetics in patients with external ventriculostomies.

1996 ◽  
Vol 40 (3) ◽  
pp. 763-766 ◽  
Author(s):  
R Nau ◽  
H W Prange ◽  
M Kinzig ◽  
A Frank ◽  
A Dressel ◽  
...  
Keyword(s):  
Central Nervous System ◽  
Cerebrospinal Fluid ◽  
Nervous System ◽  
High Performance ◽  
Elimination Half ◽  
Daily Dose ◽  
Order Of Magnitude ◽  
The Central Nervous System ◽  
Occlusive Hydrocephalus ◽  
A Minor

Ceftazidime has proven to be effective for the treatment of bacterial meningitis caused by multiresistant gram-negative bacteria. Since nosocomial central nervous system infections are often accompanied by only a minor dysfunction of the blood-cerebrospinal fluid (CSF) barrier, patients with noninflammatory occlusive hydrocephalus who had undergone external ventriculostomy were studied (n = 8). Serum and CSF were drawn repeatedly after the administration of the first dose of ceftazidime (3 g over 30 min intravenously), and concentrations were determined by high-performance liquid chromatography by using UV detection. The concentrations of ceftazidime in CSF were maximal at 1 to 13 h (median, 5.5 h) after the end of the infusion and ranged from 0.73 to 2.80 mg/liter (median, 1.56 mg/liter). The elimination half-lives were 3.13 to 18.1 h (median, 10.7 h) in CSF compared with 2.02 to 5.24 h (median, 3.74 h) in serum. The ratios of the areas under the concentration-time curves in CSF and serum (AUCCSF/AUCS) ranged from 0.027 to 0.123 (median, 0.054). After the administration of a single dose of 3 g, the maximum concentrations of ceftazidime in CSF were approximately four times higher than those after the administration of 2-g intravenous doses of cefotaxime (median, 0.44 mg/liter) and ceftriaxone (median, 0.43 mg/liter) (R. Nau, H. W. Prange, P. Muth, G. Mahr, S. Menck, H. Kolenda, and F. Sörgel, Antimicrob. Agents Chemother. 37:1518-1524, 1993). The median AUCCSF/AUCS ratio of ceftazidime was slightly below that of cefotaxime (0.12), but it was 1 order of magnitude above the median AUCCSF/AUCS of ceftriaxone (0.007) (Nau et al., Antimicrob. Agents Chemother. 37:1518-1524, 1993). The concentrations of ceftazidime observed in CSF were above the MICs for most Pseudomonas aeruginosa strains. However, they are probably not high enough to be rapidly bactericidal. For this reason, the daily dose should be increased to 12 g in cases of P. aeruginosa infections of the central nervous system when the blood-CSF barrier is minimally impaired.

scholarly journals Single particle inductively coupled plasma mass spectrometry: investigating nonlinear response observed in pulse counting mode and extending the linear dynamic range by compensating for dead time related count losses on a microsecond timescale

2020 ◽  
Vol 35 (1) ◽  
pp. 84-99 ◽  
Author(s):  
Ingo Strenge ◽  
Carsten Engelhard
Keyword(s):  
Inductively Coupled Plasma ◽  
Nonlinear Response ◽  
Dynamic Range ◽  
Dead Time ◽  
Linear Dynamic Range ◽  
Pulse Counting ◽  
Inductively Coupled ◽  
Linear Dynamic ◽  
Order Of Magnitude ◽  
Plasma Mass Spectrometry

Sampling of the pulse-counting signal with μs time-resolution provided a functional compensation for dead-time related count losses in spICP-MS, ultimately improving the linear dynamic range by one order of magnitude towards higher count rates.

The Refinement of the Nanoporous Copper by Adding Third Elements

2014 ◽  
Vol 783-786 ◽  
pp. 1986-1989
Author(s):  
Zhen Hua Dan ◽  
Feng Xiang Qin ◽  
Nobuyoshi Hara
Keyword(s):  
Lower Surface ◽  
Pore Sizes ◽  
Surface Diffusivity ◽  
Minor Addition ◽  
Cu Alloys ◽  
Nanoporous Copper ◽  
Order Of Magnitude ◽  
A Minor ◽  
Trace Formation ◽  
Nanoporous Structures

Fine nanoporous copper was fabricated from the amorphous Ti-Cu alloys with a minor addition of silver in 10 mM HF solutions. The pore sizes decreased from 100 nm to 12 nm with the increase of the Ag contents in comparison of Ti60Cu40 ribbons free of Ag. With increasing of the dealloying time, the sizes of the nanopores and ligaments increased for the nanostrucutres on Ti60Cu38Ag2 ribbons since the segregation of the Ag phase which triggered the galvanic dissolution of the adjacent Cu matrix in form of micro-couplings to further coarsen the nanoporous Cu. On the contrary, the trace formation of the Ag phase on the Ti60Cu39Ag1 ribbons had a weak ability to motivate the galvanic dissolution, indicating by the constant pore sizes and slight decrease in the ligament sizes with the increase in the dealloying time. The refinement of the nanoporous structures was ascribed to the drastic decrease in the surface diffusivity. The decrease in the surface diffusivity due to the involvement of Ag with a lower surface diffusivity in comparison of Cu was more than one order of magnitude. The involvement of Ag adatoms restricted the diffusion of Cu adatoms in the interface regions in the inward and outward directions.

The role of surface cohesion is wind-driven snow transport

2020 ◽  
Author(s):  
Francesco Comola ◽  
Johan Gaume ◽  
Jasper Kok ◽  
Michael Lehning
Keyword(s):  
Blowing Snow ◽  
Snow Surface ◽  
Wind Speeds ◽  
Wide Range ◽  
Bed Forms ◽  
Geophysical Processes ◽  
Order Of Magnitude ◽  
History Of ◽  
Snow Transport

&lt;p&gt;The wind-driven saltation of sediments, such as snow and sand, is responsible for a wide range of geophysical processes. Blowing-snow, in particular, affects snow surface properties and drives snow redistribution in alpine terrain. As such, it is of fundamental importance for avalanche mechanics. One of the most important controls on initiation and development of snow saltation is the surface cohesion induced by ice particle sintering. Although inter-particle cohesion is known to limit the number of grains lifted from the surface through aerodynamic entrainment and granular splash, the role of cohesion in the development of saltation from onset to steady state is still poorly understood. Using a numerical model based on the discrete element method, we show that saltation over cohesive beds sustains itself at wind speeds one order of magnitude smaller than those necessary to initiate it, giving rise to hysteresis in which the occurrence of transport depends on the history of the wind. Our results further suggest that saltation over cohesive beds requires much longer distances to saturate, thereby increasing the size of the smallest stable bed forms.&lt;/p&gt;

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