Inhibition of Phytophthora cactorum by a bacterial antagonist

1983 ◽  
Vol 61 (12) ◽  
pp. 3343-3348 ◽  
Author(s):  
R. S. Utkhede ◽  
A. P. Gaunce
Keyword(s):  
Molecular Weight ◽  
Low Ph ◽  
Low Molecular Weight ◽  
Ion Exchange Resins ◽  
Field Soil ◽  
Acid Molecule ◽  
Phytophthora Cactorum ◽  
Fatty Acid Molecule ◽  
Cornmeal Agar ◽  
Exchange Resins

Bacterial iolate B8 inhibited the growth of six isolates of Phytophthora cactorum on cornmeal agar. Under greenhouse conditions, B8 reduced infections by three isolates of P. cactorum in sterile field soil. Growth of P. cactorum on cornmeal agar was completely inhibited with 40% autoclaved B8 extract. The growth was significantly reduced by low pH alone (pH 4.5 or less) but even when the pH of B8 extract was raised to 6, P. cactorum growth was completely inhibited. Cornmeal agar buffered with 15 mM citrate, pH 5, was suitable for assaying extracts for antagonism to P. cactorum. Acetic acid and other fatty acids (possible metabolites of B8) were also inhibitory, with degree of antibiosis increasing with the size of the fatty acid molecule. The antibiotic produced by B8 was characterized as neutral (not absorbed by ion exchange resins) and of low molecular weight.

Effect of pH on the Desorption of Trace Metals by Different LMWOAs from a Field Soil

2014 ◽  
Vol 1073-1076 ◽  
pp. 193-196 ◽  
Author(s):  
Yu Shuang Li ◽  
Yong Xia Hou ◽  
Xue Ying Song ◽  
Li Qi Sun ◽  
Shuang Li ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Citric Acid ◽  
Trace Metals ◽  
Malonic Acid ◽  
Dominant Factor ◽  
Low Molecular Weight ◽  
Field Soil ◽  
Initial Ph ◽  
The Stability ◽  
Factor Governing

Effects of initial pH on desorption of copper (Cu), cadmium (Cd), and lead (Pb) by different low molecular weight organic acids (LMWOAs) from soils were examined. Cu, Cd, and Pb removal by LMWOAs was highly dependent on the initial pH. With an increase in pH, the amounts of the three trace metals desorbed by malonic acid and DL-hydroxybutanedioic acid sharply decreased, and desorption of Cd and Pb by malonic acid followed the same trend. These results indicate that pH was the dominant factor governing the release of trace metals by LMWOA extraction. When the pH of the solutions was not adjusted, malonic acid was found to be most effective in extracting Cd and Cu from the field soil. Desorption of both Cu and Cd from soil followed a descending order (malonic acid >citric acid > DL-hydroxybutanedioic acid) that was consistent with the acids’ acidity from strong to weak. However, Pb desorption followed a release order (citric acid > malonic acid > DL-hydroxybutanedioic acid) that was well matched by the same sequence in the stability constants of their produced Pb-ligand complexes.

scholarly journals Dissolution of mimetite Pb5(AsO4)3Cl in malic acid solutions

Mineralogia ◽  
2015 ◽  
Vol 45 (1-2) ◽  
pp. 3-12 ◽  
Author(s):  
Piotr Turek ◽  
Tomasz Bajda ◽  
Maciej Manecki
Keyword(s):  
Molecular Weight ◽  
Malic Acid ◽  
Equilibrium Solution ◽  
Solubility Product ◽  
Low Ph ◽  
Organic Ligands ◽  
Low Molecular Weight ◽  
Acid Solutions ◽  
Lead Arsenate ◽  
Organic Solutions

Abstract Mimetite Pb5(AsO4)3Cl is the most insoluble lead arsenate mineral and could be used in remediation techniques to reduce As(V) mobility in soils. However, low-molecular-weight organic acids such as malic acid increase its solubility. The effect of malic acid on the dissolution of mimetite strongly depends on the pH of the equilibrium solution. At low pH, mimetite is decomposed mostly by the mechanism of protonation. With increasing pH, the solubility of mimetite decreases and a greater influence in its dissolution is ascribed to complexation of Pb(II) by organic ligands. During dissolution experiments, the amount of arsenic released to solution was > 26% higher in organic solutions than in inorganic solutions, and the amount of lead was > 8% greater. The solubility product of mimetite (KSP) was calculated in order to quantify the thermodynamic stability of the investigated mineral. The value obtained, i.e., -24.52 ± 0.49 fluctuates between the values of -21.69 ± 1.05 and -27.87 ± 0.42 reported in the literature.

scholarly journals Succinoglycan Production Contributes to Acidic pH Tolerance in Sinorhizobium meliloti Rm1021

2017 ◽  
Vol 30 (12) ◽  
pp. 1009-1019 ◽  
Author(s):  
Justin P. Hawkins ◽  
Barney A. Geddes ◽  
Ivan J. Oresnik
Keyword(s):  
Molecular Weight ◽  
Sinorhizobium Meliloti ◽  
Degree Of Polymerization ◽  
Low Ph ◽  
Nodule Development ◽  
Low Molecular Weight ◽  
Nodule Occupancy ◽  
Acidic Ph ◽  
Ph Tolerance ◽  
Genes Encoding

In this work, the hypothesis that exopolysaccharide plays a role in the survival of Sinorhizobium meliloti at low pH levels is addressed. When S. meliloti was grown at pH 5.75, synthesis of succinoglycan increased, whereas synthesis of galactoglucan decreased. Succinoglycan that was isolated from cultures grown at low pH had a lower degree of polymerization relative to that which was isolated from cultures grown at neutral pH, suggesting that low–molecular weight (LMW) succinoglycan might play a role in adaptation to low pH. Mutants unable to produce succinoglycan or only able to produce high–molecular weight polysaccharide were found to be sensitive to low pH. However, strains unable to produce LMW polysaccharide were 10-fold more sensitive. In response to low pH, transcription of genes encoding proteins for succinoglycan, glycogen, and cyclic β(1-2) glucans biosynthesis increased, while those encoding proteins necessary for the biosynthesis of galactoglucan decreased. While changes in pH did not affect the production of glycogen or cyclic β(1-2) glucan, it was found that the inability to produce cyclic β(1-2) glucan did contribute to pH tolerance in the absence of succinoglycan. Finally, in addition to being sensitive to low pH, a strain carrying mutations in exoK and exsH, which encode the glycanases responsible for the cleavage of succinoglycan to LMW succinoglycan, exhibited a delay in nodulation and was uncompetitive for nodule occupancy. Taken together, the data suggest that the role for LMW succinoglycan in nodule development may be to enhance survival in the colonized curled root hair.

scholarly journals A simple two-step labeling procedure for ultrastructural localization of cell surface anionic sites.

1987 ◽  
Vol 35 (10) ◽  
pp. 1063-1067 ◽  
Author(s):  
E Skutelsky ◽  
E A Bayer
Keyword(s):  
Molecular Weight ◽  
Cell Surface ◽  
Blood Cells ◽  
Ultrastructural Localization ◽  
Low Ph ◽  
Low Molecular Weight ◽  
Cationized Ferritin ◽  
Anionic Sites ◽  
Secondary Interaction ◽  
Membrane Bound

We propose a new method for ultrastructural localization of cell surface anionic sites. The method consists of sequential interaction of aldehyde-fixed cells with a polycationic reagent, poly-L-lysine (PL), followed by secondary interaction with a negatively charged marker, ferritin. By use of PL of low molecular weight (4000) on aldehyde-pre-fixed red blood cells and macrophages, the reaction resulted in binding of ferritin particles to cell surface anionic sites with a density distribution resembling that of cationized ferritin (CF). The density of the attached ferritin molecules increased in direct correlation with the MW of PL used. The primary PL interaction can be carried out at low pH (less than 2), thus restricting the labeling mainly to membrane-bound sialyl residues.

Embedding Procedure for Water Swollen Samples

1970 ◽  
Vol 28 ◽  
pp. 504-505
Author(s):  
Ann M. Thomas ◽  
Virginia Shemeley
Keyword(s):  
Electron Microscopy ◽  
Transmission Electron Microscopy ◽  
Ion Exchange ◽  
Structural Changes ◽  
Cross Linking ◽  
Ion Exchange Resins ◽  
Transmission Electron ◽  
First Pass ◽  
Exchange Resins

Those samples which swell rapidly when exposed to water are, at best, difficult to section for transmission electron microscopy. Some materials literally burst out of the embedding block with the first pass by the knife, and even the most rapid cutting cycle produces sections of limited value. Many ion exchange resins swell in water; some undergo irreversible structural changes when dried. We developed our embedding procedure to handle this type of sample, but it should be applicable to many materials that present similar sectioning difficulties.The purpose of our embedding procedure is to build up a cross-linking network throughout the sample, while it is in a water swollen state. Our procedure was suggested to us by the work of Rosenberg, where he mentioned the formation of a tridimensional structure by the polymerization of the GMA biproduct, triglycol dimethacrylate.

A high-performance oil-free backing pump for electron microscopes

1978 ◽  
Vol 36 (1) ◽  
pp. 110-111
Author(s):  
G.K.W. Balkau ◽  
E. Bez ◽  
J.L. Farrant
Keyword(s):  
Molecular Weight ◽  
Electron Microscope ◽  
Hot Spots ◽  
High Performance ◽  
Carbonaceous Material ◽  
Contamination Rate ◽  
Low Molecular Weight ◽  
Principal Source ◽  
Rotary Pumps ◽  
Electron Microscopes

The earliest account of the contamination of electron microscope specimens by the deposition of carbonaceous material during electron irradiation was published in 1947 by Watson who was then working in Canada. It was soon established that this carbonaceous material is formed from organic vapours, and it is now recognized that the principal source is the oil-sealed rotary pumps which provide the backing vacuum. It has been shown that the organic vapours consist of low molecular weight fragments of oil molecules which have been degraded at hot spots produced by friction between the vanes and the surfaces on which they slide. As satisfactory oil-free pumps are unavailable, it is standard electron microscope practice to reduce the partial pressure of organic vapours in the microscope in the vicinity of the specimen by using liquid-nitrogen cooled anti-contamination devices. Traps of this type are sufficient to reduce the contamination rate to about 0.1 Å per min, which is tolerable for many investigations.

Low-molecular-weight heparin in the prevention and treatment of thromboembolic disorders

1998 ◽  
Vol 1 (5) ◽  
pp. 166-174 ◽  
Author(s):  
Evelyn R Hermes De Santis ◽  
Betsy S Laumeister ◽  
Vidhu Bansal ◽  
Vandana Kataria ◽  
Preeti Loomba ◽  
...  
Keyword(s):  
Molecular Weight ◽  
Low Molecular Weight Heparin ◽  
Low Molecular Weight ◽  
Prevention And Treatment
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