EFFECT OF pH ON LOW TEMPERATURE GROWTH OF SALMONELLA1

1972 ◽  
Vol 35 (1) ◽  
pp. 49-52 ◽  
Author(s):  
J. R. Matches ◽  
J. Liston
Keyword(s):  
Low Temperature ◽  
Growth Temperature ◽  
Low Temperatures ◽  
Food Poisoning ◽  
Combined Effects ◽  
Temperature Growth ◽  
Ph Values ◽  
Effects Of Ph ◽  
Salmonella Serotypes ◽  
Ph Range

The combined effects of pH and temperature on growth of three serotypes of salmonellae are reported. Salmonela heidelberg grew on the surface of agar over the pH range of 5.0 to 9.0. Minimum growth temperatures of 5.3, 5.2, and 5.3 C were obtained at pH values of 6.0, 7.0, and 8.0, respectively. In broth, S. heidelberg increased in number over the pH range of 6.0 to 8.0, with the lowest growth temperature of 6.0 C obtained at pH 7.0. Salmonella typhimurium increased in number in broth at pH values of 6.0 to 9.0. A time-temperature effect was shown by this organism after 16 days. Salmonella derby grew over the pH range of 6.0 to 8.0 in broth, with the lowest growth temperature of 9.0 C obtained at pH 6.0 and pH 7.0. The results indicate that food-poisoning Salmonella serotypes grow only over a narrow pH range at low temperatures.

The Influence of Growth Temperature on Oxygen Concentration in GaN Buffer Layer

2008 ◽  
Vol 1068 ◽  
Author(s):  
Ewa Dumiszewska ◽  
Wlodek Strupinski ◽  
Piotr Caban ◽  
Marek Wesolowski ◽  
Dariusz Lenkiewicz ◽  
...  
Keyword(s):  
High Temperature ◽  
Buffer Layer ◽  
Oxygen Concentration ◽  
Growth Temperature ◽  
Low Temperatures ◽  
Buffer Layers ◽  
Crystalline Quality ◽  
Temperature Growth ◽  
Gan Buffer Layer

ABSTRACTThe influence of growth temperature on oxygen incorporation into GaN epitaxial layers was studied. GaN layers deposited at low temperatures were characterized by much higher oxygen concentration than those deposited at high temperature typically used for epitaxial growth. GaN buffer layers (HT GaN) about 1 μm thick were deposited on GaN nucleation layers (NL) with various thicknesses. The influence of NL thickness on crystalline quality and oxygen concentration of HT GaN layers were studied using RBS and SIMS. With increasing thickness of NL the crystalline quality of GaN buffer layers deteriorates and the oxygen concentration increases. It was observed that oxygen atoms incorporated at low temperature in NL diffuse into GaN buffer layer during high temperature growth as a consequence GaN NL is the source for unintentional oxygen doping.

scholarly journals Effects of pH and Aeration on Sclerotium rolfsii sacc. Mycelial Growth, Sclerotial Production and Germination

2018 ◽  
Vol 7 (3) ◽  
pp. 123-129 ◽  
Author(s):  
Fakher Ayed ◽  
Hayfa Jabnoun-Khiareddine ◽  
Rania Aydi-Ben-Abdallah ◽  
Mejda Daami-Remadi
Keyword(s):  
Mycelial Growth ◽  
Sclerotium Rolfsii ◽  
Dry Weight ◽  
Ph Values ◽  
Effects Of Ph ◽  
Ph Range ◽  
Sclerotial Development ◽  
Sclerotial Germination

Sclerotium rolfsii is one of the devastating soilborne fungus responsible for significant plant losses. The effects of pH and aeration on pathogen mycelial growth, sclerotial production and germination were investigated for three Tunisian isolates. Optimal mycelial growth occurred at pH 6 for Sr2 and Sr3 isolates and at pH 6-7 for Sr1. Dry mycelial growth was optimum at pH values ranging between 4 and 7. Sclerotial initiation started on the 3rd day of incubation at all pH values tested and mature sclerotia were formed after 6 to 12 days. Optimal sclerotial production was noted at pH 5. The dry weight of 100 sclerotia varied depending on isolates and pH and occurred at pH range 4-7. At pH 9, mycelial growth, sclerotial production and dry weight of 100 sclerotia were restricted. The optimum sclerotial germination, noted after 24 h of incubation, varied depending on isolates and pH and occurred at pH 4-9. Mycelial growth was optimum in aerated plates with a significant isolates x aeration treatments interaction. Sclerotial initiation occurred at the 3rd day of incubation and mature sclerotia were observed after 6-9 days. Sclerotial development was very slow in completely sealed plates and dark sclerotia were produced only after 15 days of incubation. The highest sclerotial yields were noted in aerated plates. The highest dry weight of 100 sclerotia for Sr1 isolate was recorded in ½ sealed, no sealed and completely sealed plates, while for Sr2, it was noted in ½ and ⅔ sealed plates. For Sr3, the maximum dry weight of 100 sclerotia was recorded in ½, ⅔ and completely sealed plates. Germination of S. rolfsii sclerotia, after 24 h of incubation, did not vary significantly depending on aeration treatments and ranged from 90 to 100% for all isolates.

EFFECTS OF pH AND NITROGEN SOURCES ON GROWTH OF MICROCYSTIS AERUGINOSA KÜTZ.

1962 ◽  
Vol 8 (1) ◽  
pp. 1-11 ◽  
Author(s):  
Jack McLachlan ◽  
P. R. Gorham
Keyword(s):  
Growth Inhibition ◽  
Microcystis Aeruginosa ◽  
Nitrate Nitrogen ◽  
Nitrogen Sources ◽  
Cesium Chloride ◽  
Potassium Nitrate ◽  
Degree Of Ionization ◽  
Ph Values ◽  
Effects Of Ph ◽  
Ph Range

Microcystis aeruginosa Kütz. (strain NRC-1) grew equally well throughout the pH range 6.5 to 10 when provided with suitable media. Toxicity of tris(hydroxymethyl)aminomethane (TRIS) towards the alga was found to decrease as the pH decreased and could be correlated with the degree of ionization of the TRIS molecule. Other organic buffers examined were either toxic at all concentrations and pH values tested or promoted lysis. When TRIS was used as a buffer, higher concentrations of cesium chloride and potassium nitrate were tolerated without growth inhibition at pH 6.5 than at 7.5. In the presence of TRIS, Microcystis grew equally well with nitrate, ammonium, or urea as nitrogen sources. Eight out of 20 amino compounds examined served as nitrogen sources in TRIS-buffered medium, but growth was poorer than with nitrate nitrogen.

scholarly journals Adsorption Properties of Sepiolite in Relation to Uranium and Lanthanide Ions

Minerals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 686 ◽  
Author(s):  
Gładysz-Płaska
Keyword(s):  
Adsorption Capacity ◽  
Adsorption Properties ◽  
Lanthanide Ions ◽  
Ambient Conditions ◽  
Initial Concentration ◽  
Ph Values ◽  
Batch Technique ◽  
Effects Of Ph ◽  
Ph Range

The batch technique was used to study the adsorption of La(III), Eu(III), Lu(III), and U(VI) ions on sepiolite and ODTMA–sepiolite under ambient conditions. The effects of pH, time, and initial concentration were investigated. The highest U(VI) adsorption was found on ODTMA-sepiolite in the pH range of 6–8, while in the case of lanthanide ions, adsorption on sepiolite was 80% in the pH range of 4–8 and 98% for pH values above 8. The adsorption capacity of ODTMAsepiolite was found to be 285.6 mg/g for uranium, and raw sepiolite: 142.8 mg/g for U(VI), 91.6 mg/g for La(III), 91.4 mg/g for Eu (III), and 104.9 mol/g for Lu(III). ODTMA–sepiolite turned out to be a weak sorbent for lanthanide ions. Two short- and long-lived fluorescence species were observed in the TRLFS spectra of U(VI) adsorbed on sepiolite at pH 6.5. The average lifetimes of short- (τ1) and long-lived (τ2) fluorescence are τ1 = 2420 ± 430 ns and τ2 = 37950 ± 5710 ns for U-sepiolite; τ1 = 3523 ± 160 ns and τ2 = 45400 ± 1830 ns for U-ODTMA–sepiolite.

Adsorption and desorption of boron by goethite

Soil Research ◽  
1987 ◽  
Vol 25 (4) ◽  
pp. 377 ◽  
Author(s):  
PM Bloesch ◽  
LC Bell ◽  
JD Hughes
Keyword(s):  
Elevated Temperature ◽  
Boron Concentration ◽  
Soil Testing ◽  
Adsorption And Desorption ◽  
Ph Values ◽  
Competing Anions ◽  
Effects Of Ph ◽  
Ph Range ◽  
Best Fit ◽  
Boron Adsorption

The effects of varying pH, concentration of boron, and competing anions on the adsorption of boron were examined. Boron adsorption initially increased with pH, peaked at approximately pH 8, and then declined. The presence of phosphate reduced adsorption over the pH range 5.2-10.6; the effect of sulfate was less than that of phosphate and ceased at about pH 7. The presence of mannitol caused virtually no difference in boron adsorption up to about pH 6, but reduced adsorption at higher values. The model by Bowden and coworkers was successful in describing both the charge characteristics of goethite in the absence of boron adsorption and the effects of pH and boron concentration on adsorption of the element. The best fit of the model was achieved when B(OH)4-, B3O3(OH)4-, B4O5(OH):- and B5O6(OH)4- were considered as the adsorbing species, although B(OH)4- and B4O5(OH)24- were predicted to be the major adsorbing ions. Boron adsorption was found to be reversible with respect to both concentration and pH. Elevated temperature increased the amount of desorption at both pH 6 and 8. The effect of mannitol on boron desorption mirrored the effect of the compound on adsorption of the element; there was no effect up to pH 6, but at higher pH values desorption was increased. The significance of the desorption data for soil testing for boron is discussed.

Split Defect of Swiss Cheese

1975 ◽  
Vol 38 (1) ◽  
pp. 31-35 ◽  
Author(s):  
D. H. HETTINGA ◽  
G. W. REINBOLD
Keyword(s):  
Low Temperature ◽  
Malate Dehydrogenase ◽  
Low Temperatures ◽  
Specific Activity ◽  
Preceding Paper ◽  
Co2 Production ◽  
Swiss Cheese ◽  
Temperature Growth ◽  
Metabolic Characteristics ◽  
Specific Activities

In a preceding paper we reported that certain strains of Propionibacterium which grow at low temperatures are able to split Swiss cheese. The metabolic characteristics of these strains differ from those of strains unable to grow and produce CO2 at low temperatures. The optimal pH for malate dehydrogenase activity of cell-free extracts of the low-temperature growing strains was 7.5, whereas it was 8.5 for strains lacking the ability to grow at low temperatures. Arrhenius plots of enzymic specific activity for lactate and malate dehydrogenases of cell-free extracts obtained from low-temperature growing strains showed greatest activities at temperatures below 10 C. At 15 C or greater, cell-free extracts of strains without low-temperature growth ability showed equal or greater lactate or malate dehydrogenase specific activities. Thus, enzymes of low-temperature growing strains showed greater capacities for activity at both lower temperatures and lower pH. These data support the hypothesis that such strains at low temperature are capable of CO2 production which creates a predisposition for Swiss cheese to split when stored at temperatures of 10 C or lower.

scholarly journals Zinc adsorption in highly weathered soils

2008 ◽  
Vol 43 (1) ◽  
pp. 131-139 ◽  
Author(s):  
José Carlos Casagrande ◽  
Marcio Roberto Soares ◽  
Ernesto Rinaldi Mouta
Keyword(s):  
Ionic Strength ◽  
Ph Value ◽  
Batch Adsorption ◽  
Adsorption Mechanisms ◽  
Ionic Strength Effect ◽  
Ph Values ◽  
Effects Of Ph ◽  
Ph Range ◽  
Highly Weathered Soils ◽  
Zinc Adsorption

The objective of this work was to assess the effects of pH and ionic strength upon zinc adsorption, in three highly weathered variable charge soils. Adsorption isotherms were elaborated from batch adsorption experiments, with increasing Zn concentrations (0-80 mg L-1), and adsorption envelopes were constructed through soil samples reactions with 0.01, 0.1 and 1 mol L-1 Ca(NO3)2 solutions containing 5 mg L-1 of Zn, with an increasing pH value from 3 to 8. Driving force of reaction was quantified by Gibbs free energy and separation factor. Isotherms were C-, H- and L-type and experimental results were fitted to nonlinear Langmuir model. Maximum adsorption ranged from 59-810 mg kg-1, and Zn affinity was greater in subsoil (0.13-0.81 L kg-1) than in the topsoil samples (0.01-0.34 L kg-1). Zinc adsorption was favorable and spontaneous, and showed sharply increase (20-90%) in the 4-6 pH range. No effect of ionic strength was observed at pH values below 5, because specific adsorption mechanisms predominated in the 3-5 pH range. Above pH 5, and in subsoil samples, Zn was adsorbed by electrostatic mechanisms, since ionic strength effect was observed. Despite depth and ionic strength effects, Zn adsorption depends mainly on the pH.

Low Temperature Growth Mechanism of GaN Crystal by Hydride Vapor Phase Epitaxy

2003 ◽  
Vol 764 ◽  
Author(s):  
Hai-Ping Liu ◽  
In-Gann Chen ◽  
Jenq-Dar Tsay ◽  
Wen-Yueh Liu ◽  
Yih-Der Guo ◽  
...  
Keyword(s):  
Low Temperature ◽  
Vapor Phase ◽  
Growth Mechanism ◽  
Growth Temperature ◽  
Vapor Phase Epitaxy ◽  
High Index ◽  
Hydride Vapor Phase Epitaxy ◽  
Temperature Growth ◽  
Low Temperature Growth ◽  
Gan Crystal

AbstractThe low temperature growth of GaN crystal using epitaxy lateral overgrowth (ELO) on SiO2 dot pattern below 900°C by hydride vapor phase epitaxy (HVPE) have been studied. It is observed that the growth rate of GaN hexagonal pyramidal crystals along [1101] direction increases as growth temperature decreases. At low temperature of ∼ 850°C, hexagonal GaN columnar crystals with high index facet at the top can be observed. It is proposed that the surface diffusion length of precursors, such as NH3 and GaCl, decreases at lower temperature that reduces the probability of desorption and increase the lifetime. The condensation of Ga liquid droplets on the GaN surface will change the relative stability of {1101} facet. Therefore, the formation of high index planes such as {2122} facet on the top of hexagonal column along with the formation of stacking fault on the (0001) plane can be observed. A detailed study of the effect of growth temperature on the crystal growth mechanism will be presented.

The Effect Of The Nucleation Layer On The Low Temperature Growth Of Gan Using A Remote Plasma Enhanced – Ultrahigh Vacuum Chemical Vapor Deposition (RPE-UHVCVD)

1997 ◽  
Vol 482 ◽  
Author(s):  
Kyoung-Kook Kim ◽  
Dong-Jun Kim ◽  
Jong-Sik Paek ◽  
Je-Hee Jo ◽  
Hyo-Gun Kim ◽  
...  
Keyword(s):  
Chemical Vapor Deposition ◽  
Low Temperature ◽  
Growth Temperature ◽  
Vapor Deposition ◽  
Ultrahigh Vacuum ◽  
Chemical Vapor ◽  
Remote Plasma ◽  
Nucleation Layer ◽  
Temperature Growth ◽  
Low Temperature Growth

AbstractThis study investigated the low temperature growth of GaN on a nucleation layer in a remote plasma enhanced-ultrahigh vacuum chemical vapor deposition (RPE-UHVCVD) system which is equipped with an rf plasma cell for a nitrogen source. It was found that the growth temperature and the film thickness of the nucleation layer and the nitrogen flow rate for GaN growth play important roles in the improvement of crystallinity of the GaN layer. The nitridation of sapphire was also found to enhance the formation of facet shaped nuclei on the nucleation layer. As the temperature of the nucleation layer increased, islands with hexagonal and other facet shapes were formed on the grown GaN surface. This facet formation was related with the surface morphology and crystallinity of GaN. The best crystallinity was measured in a GaN layer with hexagonal facets on the surface and such GaN layers could be grown on a nucleation layer grown at 375 °C. Nitridation of sapphire and the growth temperature of the nucleation layer were also found to change the island shapes which enhances the formation of columnar structures in the GaN layer, resulting in the growth of a high crystalline GaN layer at low temperature.

scholarly journals Psychrobacter arcticus 273-4 Uses Resource Efficiency and Molecular Motion Adaptations for Subzero Temperature Growth

2009 ◽  
Vol 191 (7) ◽  
pp. 2340-2352 ◽  
Author(s):  
Peter W. Bergholz ◽  
Corien Bakermans ◽  
James M. Tiedje
Keyword(s):  
Gene Expression ◽  
Energy Metabolism ◽  
Low Temperature ◽  
Low Temperatures ◽  
Extreme Environments ◽  
Resource Efficiency ◽  
Subzero Temperature ◽  
Rna Helicases ◽  
Temperature Growth ◽  
Peptidyl Prolyl Isomerases

ABSTRACT Permafrost soils are extreme environments that exert low-temperature, desiccation, and starvation stress on bacteria over thousands to millions of years. To understand how Psychrobacter arcticus 273-4 survived for >20,000 years in permafrost, transcriptome analysis was performed during growth at 22°C, 17°C, 0°C, and −6°C using a mixed-effects analysis of variance model. Genes for transcription, translation, energy production, and most biosynthetic pathways were downregulated at low temperatures. Evidence of isozyme exchange was detected over temperature for d-alanyl-d-alanine carboxypeptidases (dac1 and dac2), DEAD-box RNA helicases (csdA and Psyc_0943), and energy-efficient substrate incorporation pathways for ammonium and acetate. Specific functions were compensated by upregulation of genes at low temperature, including genes for the biosynthesis of proline, tryptophan, and methionine. RNases and peptidases were generally upregulated at low temperatures. Changes in energy metabolism, amino acid metabolism, and RNase gene expression were consistent with induction of a resource efficiency response. In contrast to results observed for other psychrophiles and mesophiles, only clpB and hsp33 were upregulated at low temperature, and there was no upregulation of other chaperones and peptidyl-prolyl isomerases. relA, csdA, and dac2 knockout mutants grew more slowly at low temperature, but a dac1 mutant grew more slowly at 17°C. The combined data suggest that the basal biological machinery, including translation, transcription, and energy metabolism, is well adapted to function across the growth range of P. arcticus from −6°C to 22°C, and temperature compensation by gene expression was employed to address specific challenges to low-temperature growth.

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