scholarly journals Characterization of a Ralstonia solanacearum Operon Required for Polygalacturonate Degradation and Uptake of Galacturonic Acid

2003 ◽  
Vol 16 (6) ◽  
pp. 536-544 ◽  
Author(s):  
Enid T. González ◽  
Caitilyn Allen
Keyword(s):  
Ralstonia Solanacearum ◽  
Cell Walls ◽  
Galacturonic Acid ◽  
Degradation Products ◽  
Plant Cell Walls ◽  
Reaction Products ◽  
Wild Type ◽  
Pathogen Virulence ◽  
Wild Type Parent

The bacterial wilt pathogen Ralstonia solanacearum produces three extracellular polygalacturonases (PGs): PehA, PehB, and PehC. All three PGs hydrolyze pectin's polygalacturonic acid backbone, but each releases different reaction products. PehA and PehB contribute significantly to pathogen virulence, probably by facilitating root invasion and colonization. To determine the collective contribution of PGs to virulence and saprophytic survival, we cloned, characterized, and mutated the R. solanacearum pehC gene, which encodes a distinctive monogalacturonate-releasing exo-PG. The virulence of a pehC mutant on tomato was indistinguishable from that of its wild-type parent; thus, this exo-PG alone does not contribute significantly to wilt pathogenesis. Unexpectedly, a completely PG-deficient triple pehA/B/C mutant was slightly more virulent than a pehA/B mutant. PehC may degrade galacturonide elicitors of host defense, thereby protecting the pathogen from plant antimicrobial responses. A galacturonate transporter gene, exuT, is immediately downstream of pehC and the two genes are co-transcribed. It has been hypothesized that galacturonic acid released by PGs from plant cell walls nourishes bacteria during pathogenesis. To separate the pectolytic and nutrient-generating roles of the PGs, we made an exuT mutant, which still produces all three isozymes of PG but cannot uptake PG degradation products. This exuT mutant had wild-type virulence on tomato, demonstrating that metabolism of galacturonic acid does not contribute significantly to bacterial success inside the plant.

Characterization of dissolved material during the initial phase of softwood kraft pulping

TAPPI Journal ◽  
2013 ◽  
Vol 12 (1) ◽  
pp. 37-43 ◽  
Author(s):  
HANNU PAKKANEN ◽  
TEEMU PALOHEIMO ◽  
RAIMO ALÉN
Keyword(s):  
Mass Transfer ◽  
Molecular Mass ◽  
Initial Phase ◽  
Degradation Products ◽  
Kraft Pulping ◽  
Reaction Products ◽  
Cooking Temperature ◽  
Molecular Masses ◽  
Aliphatic Carboxylic Acids

The influence of various cooking parameters, such as effective alkali, cooking temperature, and cooking time on the formation of high molecular mass lignin-derived and low molecular mass carbohydrates-derived (aliphatic carboxylic acids) degradation products, mainly during the initial phase of softwood kraft pulping was studied. In addition, the mass transfer of all of these degradation products was clarified based on their concentrations in the cooking liquor inside and outside of the chips. The results indicated that the degradation of the major hemicellulose component, galactoglucomannan, typically was dependent on temperature, and the maximum degradation amount was about 60%. In addition, about 60 min at 284°F (140°C) was needed for leveling off the concentrations of the characteristic reaction products (3,4-dideoxy-pentonic and glucoisosaccharinic acids) between these cooking liquors. Compared with low molecular mass aliphatic acids, the mass transfer of soluble lignin fragments with much higher molecular masses was clearly slower.

Isolation and Characterization of Plant Cell Walls and Cell Wall Components

1988 ◽  
pp. 3-40 ◽  
Author(s):  
WILLIAM S. YORK ◽  
ALAN G. DARVILL ◽  
MICHAEL MCNEIL ◽  
THOMAS T. STEVENSON ◽  
PETER ALBERSHEIM
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Cell Walls ◽  
Plant Cell Walls ◽  
Cell Wall Components ◽  
Isolation And Characterization ◽  
Wall Components

Isolation and characterization of plant cell walls and cell wall components

1986 ◽  
pp. 3-40 ◽  
Author(s):  
William S. York ◽  
Alan G. Darvill ◽  
Michael McNeil ◽  
Thomas T. Stevenson ◽  
Peter Albersheim
Keyword(s):  
Cell Wall ◽  
Plant Cell ◽  
Cell Walls ◽  
Plant Cell Walls ◽  
Cell Wall Components ◽  
Isolation And Characterization ◽  
Wall Components

scholarly journals Genetics and Virulence Association of the Shigella flexneri Sit Iron Transport System

2009 ◽  
Vol 77 (5) ◽  
pp. 1992-1999 ◽  
Author(s):  
Carolyn R. Fisher ◽  
Nicola M. L. L. Davies ◽  
Elizabeth E. Wyckoff ◽  
Zhengyu Feng ◽  
Edwin V. Oaks ◽  
...  
Keyword(s):  
Epithelial Cells ◽  
Transport System ◽  
Iron Transport ◽  
Shigella Flexneri ◽  
Lung Model ◽  
Mouse Lung ◽  
Wild Type ◽  
Insertion Elements ◽  
Wild Type Parent

ABSTRACT The sit-encoded iron transport system is present within pathogenicity islands in all Shigella spp. and some pathogenic Escherichia coli strains. The islands contain numerous insertion elements and sequences with homology to bacteriophage genes. The Shigella flexneri sit genes can be lost as a result of deletion within the island. The formation of deletions was dependent upon RecA and occurred at relatively high frequency. This suggests that the sit region is inherently unstable, yet sit genes are maintained in all of the clinical isolates tested. Characterization of the sitABCD genes in S. flexneri indicates that they encode a ferrous iron transport system, although the genes are induced aerobically. The sit genes provide a competitive advantage to S. flexneri growing within epithelial cells, and a sitA mutant is outcompeted by the wild type in cultured epithelial cells. The Sit system is also required for virulence in a mouse lung model. The sitA mutant was able to infect the mice and induce a protective immune response but was avirulent compared to its wild-type parent strain.

Solid-state 13C NMR characterization of cell walls of ripening strawberries

1997 ◽  
Vol 75 (11) ◽  
pp. 1957-1964 ◽  
Author(s):  
T. H. Koh ◽  
L. D. Melton ◽  
R. H. Newman
Keyword(s):  
Solid State ◽  
Cell Walls ◽  
Proton Spin ◽  
Plant Cell Walls ◽  
Fragaria Ananassa ◽  
Nmr Characterization ◽  
Strawberry Fruit Ripening ◽  
Wall Components ◽  
C Nmr

Ripe and unripe cell walls isolated from the cortical tissues of strawberry (Fragaria × ananassa Duchesne cv. Yolo) using HEPES-buffered phenol of pH 6.5 were analysed using solid-state 13C nuclear magnetic resonance. Changes in cell wall components during ripening were investigated by separating the spectra, using proton spin relaxation editing, into three subspectra based on the mobility of the molecules. The subspectra can be assigned to rigid material (cellulose), semirigid components (primarily polygalacturonic acid) and semimobile (other detectable noncellulosic substances). The results show that, with ripening, separation between the semirigid and semimobile domains became more distinct. Associated with this, the ratio of noncellulosic material (i.e., pectins and hemicelluloses) to rigid cellulose decreased from 2.3 for unripe to 1.9 for ripe. The crystallinity of the cellulose molecules remained unaltered throughout ripening. Furthermore, our work indicates that the basic cellulose crystallite of strawberry cell walls appeared exceptionally small compared with other systems studied thus far. Key words: solid-state CP-MAS 13C NMR, cellulose, plant cell walls, strawberry, fruit ripening.

Characterization of some non-fixing mutants of common bean (Phaseolus vulgaris L.)

1993 ◽  
Vol 73 (4) ◽  
pp. 977-983 ◽  
Author(s):  
B. R. Buttery ◽  
S. J. Park
Keyword(s):  
Phaseolus Vulgaris ◽  
Nitrate Reductase ◽  
Common Bean ◽  
Rhizobium Leguminosarum ◽  
Variable Number ◽  
Wild Type ◽  
Parent Line ◽  
Rhizobium Strains ◽  
Wild Type Parent

With 18 strains of Rhizobium leguminosarum bv. phaseoli the bean mutants R99 and NOD125 remained essentially non-nodulating, while the mutant R69 produced a variable number of small white ineffective nodules, and the wild-type parent-line OAC Rico formed a variable number of pink effective nodules. Both R69 and R99 grew less vigorously than OAC Rico, but possessed similar levels of nitrate reductase in both roots and leaves, and responded in a normal way to increased supply of combined nitrogen. Reciprocal grafts between the non-nodulating R99 and NOD125, the ineffective R69, the wild-type parent line OAC Rico, and the supernodulating R32BS, demonstrated that the non-nodulating and ineffective characters were controlled by the root, and confirmed that the supernodulation character was controlled by the shoot. Key words: Common bean, nitrate reductase, non-fixing mutants, Phaseolus vulgaris, Rhizobium strains, supernodulation

scholarly journals Ekstraksi Pektin dari Limbah Kulit Jeruk (Citrus sinensis) dengan Metode Ekstraksi Gelombang Ultrasonik Menggunakan Pelarut Asam Klorida (HCl)

2019 ◽  
Vol 8 (2) ◽  
pp. 85-89
Author(s):  
Delvia Ariska Damanik ◽  
Setiaty Pandia
Keyword(s):  
Ultrasonic Wave ◽  
Cell Walls ◽  
Citrus Sinensis ◽  
Galacturonic Acid ◽  
Wave Speed ◽  
Ash Content ◽  
Plant Cell Walls ◽  
Effect Of Solvent ◽  
Orange Peels ◽  
Food And Beverage

Pectin is complex polysaccharide contained D-galacturonic acid bonded by α -1,4 glucosidic in plant cell walls. Pectin widely used in pharmaceutical, food and beverage industries. This study evaluates the effect of solvent and stirring speed on pectin characteristic. The study utilizes ultrasonic wave and acid solvent at the presence of ethanol to yield pectin following by drying to obtain dried pectin. This study carries out using 25 grams orange peels, 10 %, chloride acid solvent, 60 minutes extraction time, temperature of 60 oC, ultrasonic wave speed 50 KHz and 16 hours settling time at various solvent concentrations 0.025 N; 0.05 N; 0.075 N and stirring speed 0 rpm; 50 rpm; 100 rpm; 150 rpm. The results showed that the highest yield of pectin extraction was obtained at concentration of 0.075 N with 20.12 %; stirring speed 150 rpm, water content 8.0 %; 4,0 % ash content, and 7.44 % methoxyl content.

scholarly journals Identification and Characterization of a Phase-Variable Nonfimbrial Salmonella typhimurium Gene That Alters O-Antigen Production

1998 ◽  
Vol 66 (12) ◽  
pp. 5725-5730 ◽  
Author(s):  
Lola Y. Kwan ◽  
Richard E. Isaacson
Keyword(s):  
Salmonella Typhimurium ◽  
Phenotypic Switching ◽  
Phase Variable ◽  
Wild Type ◽  
Phagocytic Cells ◽  
Antigen Production ◽  
O Antigen ◽  
Identification And Characterization ◽  
Wild Type Parent

ABSTRACT Salmonella typhimurium 798, which was isolated from a pig, is known to phase vary from a nonadhesive to an adhesive phenotype. Cells of the adhesive phenotype adhere to porcine enterocytes, are more readily phagocytized by porcine neutrophils and macrophages, and once phagocytized can survive intracellularly, while cells of the nonadhesive phenotype die rapidly. The effect of phenotypic switching also can be visualized by changes in colony morphologies and the presence of between 10 and 15 proteins in the envelopes of cells in the adhesive phenotype. Mutants previously constructed with cells in the adhesive phenotype and the transposon TnphoA were screened to identify mutants lacking one or more of the unique proteins. One mutation was cloned and sequenced, and the mutation was shown to be in rfaL (O-antigen ligase). Expression of O antigen was shown to be phase variable. The adhesive strain expressed an O antigen that was at least eightfold longer than that for the nonadhesive strain and by virtue of O-antigen production was resistant to porcine complement. The mutant survived intracellularly in phagocytic cells as well as its wild-type parent.

scholarly journals Purification and Partial Characterization of Melanoidins Fractions from Toasted Oak Heartwood, Comparison with Melanoidins from Roasted Coffee

2018 ◽  
Vol 7 (6) ◽  
pp. 37 ◽  
Author(s):  
M. F. Nonier ◽  
N. Vivas ◽  
N. Vivas de Gaulejac ◽  
C. Mouche ◽  
C. Rossy Huguet ◽  
...  
Keyword(s):  
Antioxidant Activities ◽  
Degradation Products ◽  
Partial Characterization ◽  
Maillard Reaction Products ◽  
Reaction Products ◽  
Roasted Coffee ◽  
Oak Wood ◽  
Processing And Storage ◽  
And Storage

During the cooking, processing, and storage of food products, a whole range of browning reactions occurs, initiated by the reaction of a carbohydrate with a compound possessing a free amino group. Melanoidins formed, influence food quality, mainly their colour, their flavour, and their antioxidant activities. Melanoidins are complex Maillard reaction products. We developed a method to isolate coffee melanoidins and melanoidins from toasted oak wood. We noted that coffee is richer in melanoidin compounds than oak wood. We presented a partial characterization of melanoidins fractions from toasted oak heartwood, and a comparison with melanoidins from roasted coffee. Mass spectra of the fractions isolated from toasted oak wood indicate the presence of pentose and hexose-based oligosaccharides with different degrees of polymerisation. The presence of the oligosaccharide moieties, as well as their degradation products found in the oak wood melanoidins, supports the postulated carbohydrate-based origin of melanoidins.

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