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W J Page

Publications and source records attributed to W J Page.

At least 37 records · Page 2Linked to original sources
PubMed1986

Stimulation of Agrobacterium tumefaciens Growth by Azotobacter vinelandii Ferrisiderophores.

Azotobacter vinelandii stimulated the growth of Agrobacterium tumefaciens H2, H23, H24, H27, and ATCC 15955 on media containing insoluble iron sources. The Azotobacter vinelandii siderophores appeared to promote Agrobacterium tumefaciens growth by solubilizing mineral iron, and the ferrisiderophores so formed then acted as iron sources for Agrobacterium tumefaciens. Agrobactin, the Agrobacterium siderophore, appeared to be inefficient in solubilizing mineral iron directly.

Journal Article↗
PubMed1986

Sodium-Dependent Growth of Azotobacter chroococcum.

The majority of Azotobacter chroococcum strains in a collection obtained from Alberta soils were absolutely dependent on Na for growth. Two strains from the American Type Culture Collection also were either Na dependent or were stimulated by Na. Optimal growth required 0.8 mM Na and was limited at 0.2 to 0.35 mM Na. Growth promoted by 0.8 mM Na was inhibited by Rb > K >> NH(4) but was not affected by Li. Growth inhibition by Rb and K was overcome by increasing the Na concentration present in the medium. Excellent growth in media containing limiting Na was obtained when 25 mM Li or 25 mM Mg was added. Li was significantly more effective in replacing Na than was Mg. Na was required for growth on all C sources (glucose, sucrose, melibiose, and mannitol) and N sources (N(2), NH(4), and NO(3)) and was required throughout the pH range of growth. Cells suspended in Na -deficient medium or in distilled water did not appear to lyse or lose viability.

Journal Article↗
PubMed1984

Derepression of the Azotobacter vinelandii siderophore system, using iron-containing minerals to limit iron repletion.

Azotobacter vinelandii solubilized iron from certain minerals using only dihydroxybenzoic acid, which appeared to be produced constitutively. Solubilization of iron from other minerals required dihydroxybenzoic acid and the siderophore N,N'-bis-(2,3- dihydroxybenzoyl )-L-lysine ( azotochelin ) or these chelators plus the yellow-green fluorescent siderophore azotobactin . In addition to this sequential production of siderophores, cells also demonstrated partial to hyperproduction relative to the iron-limited control. The iron sources which caused partial derepression of the siderophores caused derepression of all the high-molecular-weight iron-repressible outer membrane proteins except a 77,000-molecular-weight protein, which appeared to be coordinated with azotobactin production. Increased siderophore production correlated with increased production of outer membrane proteins with molecular weights of 93,000, 85,000, and 77,000, but an 81,000-molecular-weight iron-repressible protein appeared at a constant level despite the degree of derepression. When iron was readily available, it appeared to complex with a 60,000-molecular-weight protein believed to form a surface layer on the A. vinelandii cell.

Azotobacter↗
PubMed1984

Regular surface layer of Azotobacter vinelandii.

Washing Azotobacter vinelandii UW1 with Burk buffer or heating cells at 42 degrees C exposed a regular surface layer which was effectively visualized by freeze-etch electron microscopy. This layer was composed of tetragonally arranged subunits separated by a center-to-center spacing of approximately 10 nm. Cells washed with distilled water to remove an acidic major outer membrane protein with a molecular weight of 65,000 did not possess the regular surface layer. This protein, designated the S protein, specifically reattached to the surface of distilled-water-washed cells in the presence of the divalent calcium, magnesium, strontium, or beryllium cations. All of these cations except beryllium supported reassembly of the S protein into a regular tetragonal array. Although the surface localization of the S protein has been demonstrated, radioiodination of exposed envelope proteins in whole cells did not confirm this. The labeling behavior of the S protein could be explained on the basis of varying accessibilities of different tyrosine residues to iodination.

Azotobacter↗
PubMed1984

Siderophore-mediated uptake of iron in Azotobacter vinelandii.

Azotobacter vinelandii produces two siderophores, N,N'-bis-(2,3-dihydroxybenzoyl)-L-lysine (azotochelin) and a yellow-green fluorescent peptide (azotobactin), under iron-limited growth conditions. 55Fe uptake was not observed until the substantial nonspecific binding of 55Fe to the cell surface was eliminated by the addition of 10 mM sodium citrate to the uptake medium. Citrate alone did not promote rapid 55Fe uptake in A. vinelandii, nor did it induce Fe-repressible outer membrane proteins. Siderophore-mediated 55Fe uptake appeared biphasic, with both the initial rapid and ensuing slower uptake being energy dependent. The purified siderophores demonstrated the same uptake pattern as the Fe-limited culture supernatant fluid, but either individually or in combination accounted for less than the total 55Fe uptake activity found in the latter. The purified siderophores appeared to be sensitive to acid, but the inhibition of 55Fe uptake was in fact caused by salt generated during neutralization. Similar 60% inhibition of 55Fe uptake activity was caused by the addition of 40 mM Na+, K+, Li+, or Mg2+ salts to the uptake medium. Ammonium was less inhibitory than the latter ions. 55Fe uptake mediated by azotobactin was more sensitive to added NaCl than was that mediated by azotochelin. Neither the chelation of iron nor the stability of the ferrisiderophore was affected by added NaCl.

Azotobacter↗
PubMed1983

Heat sensitivity of Azotobacter vinelandii genetic transformation.

Heating competent Azotobacter vinelandii at 37 or 42 degrees C resulted in a total loss of competence with no loss of viability. The transformation process was relatively insensitive to heating at either temperature once DNase-resistant DNA binding was nearly complete. Although competent and 42 degrees C-treated cells bound equivalent amounts of [32P]DNA in a DNase-resistant state, no donor DNA marker (nif) or radioactivity was detected in the envelope-free cell lysate of heated cells, suggesting that DNA transport across the cell envelope was a heat-sensitive event. Competence was reacquired in a 42 degrees C-treated culture after 2 h of incubation at 30 degrees C by a process which required RNA and protein syntheses. The release of a surface glycoprotein, required for competence, from cells treated at 42 degrees C occurred in an insufficient amount to account for the total loss of competence. Recovery of competence in 42 degrees C-treated cells and further transformation of competent cells were prevented by the exposure of cells to saturating amounts of transforming DNA. Further DNase-resistant DNA binding, however, still occurred, suggesting that there were two types of receptors for DNase-resistant DNA binding to competent A. vinelandii. DNase-resistant DNA binding was dependent on magnesium ions, and at least one receptor type did not discriminate against heterologous DNA.

Azotobacter↗
PubMed1982

Iron- and molybdenum-repressible outer membrane proteins in competent Azotobacter vinelandii.

Azotobacter vinelandii produced three major proteins of 93,000, 85,000, and 81,000 daltons and a minor 77,000-dalton protein in the outer membrane of Fe-limited cells, and these cells were competent for transformation by DNA. The synthesis of these proteins was repressed in Fe-sufficient medium. Mo limitation of nitrogen-fixing cells resulted in the hyperproduction of a 44,000-dalton protein and the production of a minor 77,000-dalton protein in the outer membrane. Mo limitation enhanced competence in Fe-limited medium and induced competence in Fe-sufficient medium. The 44,000-dalton protein was replaced by a 45,000-dalton protein when Fe-sufficient medium also contained NH4+, but the cells were noncompetent. The synthesis of these proteins was repressed in Mo-sufficient medium and by NH4+ in Fe-limited medium. All of the culture supernatants contained a blue-white fluorescent material (absorbance maximum, 214 nm) which appeared to coordinate Fe3+, Fe2+, MoO4(2-), WO3(2-), and VO3(-).

Azotobacter↗
PubMed1981

Recovery of competence in calcium-limited Azotobacter vinelandii.

Azotobacter vinelandii cells required 0.5 mM calcium in the iron-limited competence induction medium. This requirement also was fulfilled by strontium, but not by magnesium. Cells pregrown in competence medium lacking calcium rapidly recovered competence with the addition of 0.5 mM calcium, provided they were suspended in the growth supernatant. A 60,000-dalton glycoprotein (pI 5.10) present in competent or incompetent culture supernatants participated in calcium-mediated competence recovery. Cells grown in calcium-limited medium appeared to have leaky cell envelopes and released a diverse array of proteins into the culture supernatant and into distilled water washes of the cells, seven of which appeared to be more dominant in competent cells. Two distilled water washes of cells grown in calcium-limited medium did not prevent calcium-mediated recovery of competence in the culture supernatant. Four to six distilled water washes removed a competence-specific protein (pI 5.19) and prevented calcium-mediated recovery of competence in the culture supernatant.

Azotobacter↗
PubMed1979

Optimal conditions for transformation of Azotobacter vinelandii.

Optimal transformation of Azotobacter vinelandii OP required a 20-min incubation of the competent cells with deoxyribonucleic acid at 30 degrees C in buffer (pH 6.0 to 8.0) containing 8 mM magnesium sulfate. Nitrogen-fixing transformants of nitrogen fixation-deficient recipients could be plated immediately on selective medium, but transformants acquiring rifampin and streptomycin resistance required preincubation in nonselective medium. The three phenotypes achieved an approximately equal and stable frequency after 17 h (six generations) of growth in nonselective medium.

Azotobacter↗
PubMed1978

Transformation of Azotobacter vinelandii strains unable to fix nitrogen with Rhizobium spp. DNA.

The phenotypes of Azotobacter vinelandii ATCC 12837 strains defective in nitrogen fixation (Nif-) were characterized by intrageneric transformation with known Nif- strains of A. vinelandii OP. These former mutant strains were used as recipients for intergeneric transformation by deoxyribonucleic acid (DNA) prepared from Rhizobium spp. to determine if the rhizobia would transform the Azotobacter Nif- phenotypes to Nif+. The frequency of Nif+ transformants using Rhizobium DNA was always less than the frequency using Azotobacter wild-type DNA but was greater than the spontaneous reversion frequency. The Azotobacter Nif+ recombinants also were stable. DNA from all of the Rhizobium spp. transformed to Nif+ Azotobacter mutants defective in the nitrogenase component I (molybdoferredoxin); however, some recombinants had a lower nitrogenase activity and a delayed nitrogenase depression time. Mutants defective in the pleiotrophic transcriptional control of both nitrogenase components were transformed to Nif+ by the asymbiotic nitrogen fixing Rhizobium sp. 32H1 and 41A1, but not the symbiotic nitrogen-fixing species. The significance of these results and the possible future applications of this system are discussed.

Azotobacter↗
PubMed1978

Survival of microbial films in the microwave oven.

Air-dried films of Escherichia coli, Saccharomyces cerevisiae, and Bacillus subtilis spores on membrane filters, exposed to 10 min full power (650 W, 2450 MHz) irradiation in a Toshiba model ER776BT microwave oven, showed a 5-, 2-, and 0-log reduction of viable organisms respectively. Suspensions of cells or spores in phosphate buffer treated under similar conditions showed 8 logs of killing within 30 s (S. cerevisiae), 45 s(E. coli), and by 10 min (B. subtilis spores) of exposure.

Bacillus subtilis↗
PubMed1978

Induction of transformation competence in Azotobacter vinelandii iron-limited cultures.

Azotobacter vinelandii strains UW (Nif+) or UW1 (Nif-) were induced to form competent cells by growing cultures in Burk medium without added iron. Competent cells were generated in either liquid or solid medium. The competent culture was highly colored by the characteristic fluorescent green pigment of A. vinelandii but all pigmented cultures were not competent. In liquid culture, competent cells required a fixed nitrogen source (ammonia, nitrate, or urea) that was also a nitrogenase repressor. Glucose, sucrose, glycerol, and mannitol (1% w/v) were excellent C-sources for competence induction while acetate (1% w/v) and beta-hydroxybutyrate (0.2% w/v) were ineffective. Cells induced in liquid culture remained competent for a 12-h period before the end of the exponential growth phase, then competence decreased rapidly upon the initiation of the stationary phase of growth.

Azotobacter↗
PubMed1976

Physiological factors affecting transformation of Azotobacter vinelandii.

Cells of Azotobacter vinelandii (ATCC 12837) can be transformed by exogenous deoxyribonucleic acid towards the end of exponential growth. Transformation occurs at very low frequencies when the deoxyribonucleic acid is purified or when the transformation is carried out in liquid medium. Optimal transformation occurs on plates of Burk nitrogen-free glucose medium containing either high phosphate (10 mM) or low calcium (0 to 0.29 mM) content. Higher levels of calcium are inhibitory, whereas magnesium ions are essential for transformation and growth. Extracellular polymer and capsule are increasingly inhibitory to transformation and are most abundant when the calcium content of the medium is high. Transformation is optimal at pH 7.0 to 7.1 and at 30 C, conditions which also coincide with minimal extracellular polymer production. Nonencapsulated strains are excellent transformation recipients. Glycine-induced pleomorphism reduces the transformation frequency and the degree of inhibition is dependent on the phosphate concentration of the medium. Rifampin resistance and shifts from adenine, hypoxanthine, uracil, and nitrogenase auxotrophy to prototrophy can be achieved. Although single marker transfer is always greater than double marker transfer, the data suggest that rifampin resistance is linked to hypoxanthine, adenine and uracil protorophy at intervals of increasing distance. Rifampin resistance did not appear to be linked to nitrogenase.

Adenine↗
PubMed1976

Control of transformation competence in Azotobacter vinelandii by nitrogen catabolite derepression.

Azotobacter vinelandii (ATCC 12837) became competent to be transformed by exogenous deoxyribonucleic acid towards the end of exponential growth. Competence in wild-type and nitrogenase auxotrophic (nif-) strains was repressed by the addition of ammonium salts or urea to the transformation medium. Transformation of wild-type cells and nif- strains was optimal on nitrogen-free or nitrogen-limiting medium, respectively. Transformation of wild-type cells also was enhanced when the transformation medium had low molydbate content. During the development of competence, nitrogen was growth limiting, whereas carbon (glucose) was in excess. Carbon source shift-down was not effective in inducing competence. Shifting glucose-grown wild-type cells to medium containing 0.2% beta-hydroxybutyrate initiated encystment and also induced competence. The addition of glucose to this medium blocked encystment and early competence induction and reduced the transformation frequency to the basal level. Cyclic adenosine 3',5'-monophosphate induced competence in wild-type nitrogen-fixing cells and increased the transformation frequency 1,000-fold over the basal level. Exogenous cyclic adenosine 3',5'-monophosphate however, did not reverse nitrogen repression of competence in ammonia-grown wild-type or nif- strains.

Ammonia↗
PubMed1975

Relationship between calcium and uroinic acids in the encystment of Azotobacter vinelandii.

Encystment of Azotobacter vinelandii (ATCC 12837) in modified Burk nitrogen-free medium (pH 7.0) containing 0.2 percent beta-hydroxybutyrate occurs optimally in 0.37 to 0.44 mM solutions of calcium ions. Suspension of cells in media deficient in calcium results in abortive encystment characterized by the release of viscous cyst coat material. Mature cysts rupture in ethylene glycol-bis-(beta-aminoethyl ether)-N,N'-tetraacetic acid, suggesting that calcium is a structural component of the cyst coat. Maximal stimulation of encystment by calcium ions occurs prior to the completion of the cyst exine or outer coat. The uronic acid composition of cyst components is dependent on calcium levels in the medium. Uronic acids account for 31.7 percent of the intine (inner coat) and 13 percent of the exine dry weight, and only mannuronic and guluronic acids are present in these fractions. These can be extracted as homo- and heteropolymeric sequence "blocks" characteristic of alginic acids. The polyuronic acid fraction of both the cyst coats contain approximately equal amounts of heteropolymeric (mannuronic acid/guluronic acid) blocks. The exine, however, is richer in polyguluronic acid and the intine is richer in polymannuronic acid. As a result, the mannuronic acid/guluronic acid ratio of the exine is lower than that of the intine. Slimes that form in abortive encystment are rich in polymannuronic acid and have a high mannuronic acid/guluronic acid ratio. A polymannuronic acid 5-epimerase is active in the mature cyst central body and the encystment culture fluid.

Azotobacter↗
PubMed1974

Phosphate-mediated alteration of the Microsporum gypseum germination protease specificity for substrate: enhanced keratinase activity.

Inorganic phosphate was found to decrease the caseinolytic and ethyl-esterase activities of the Microsporum gypseum germination protease. The germination protease possessed exokeratinase (beta-keratinase) activity immediately after release from the fungal spore. After phosphate treatment of the enzyme, the germination protease also possessed endo-keratinase (alpha-keratinase) activity. Phosphate altered the protease's pH optimum from 9.0 to 7.0 and decreased the molecular weight from 33,000 to 16,000. These values were identical to those found for the keratinase. Alpha- and beta-keratinase activities were stimulated in excess of 200-fold by disulfide reducing agents. Natural and suspected keratin degradation products also enhanced keratinase activity. Cell fractionation and in vitro conversion of the alkaline germination protease into a functional keratinase suggested that the subunits comprising the germination protease and the keratinase were of a common origin.

Animals↗
PubMed1974

Changes in Microsporum gypseum mycelial wall and spore coat glycoproteins during sporulation and spore germination.

Ethylenediamine-soluble glycoproteins were extracted from isolated Microsporum gypseum hyphal walls during sporulation and from spore coats before and after germination. This study was carried out to identify a sporulation-specific cell wall protein that possibly served as a substrate for the alkaline protease which initiated the macroconidial germination of this fungus. Analyses revealed that water-insoluble glycoprotein accounted for 10% of the ungerminated spore coat but only for 4 to 5% of the mycelial wall dry weight. This fraction was modified in its amino acid composition during sporulation, and it decreased in protein content during spore germination. Water-soluble glycoprotein, which accounted for approximately 3 to 3.5% of either the spore coat or mycelial wall dry weight, was of similar amino acid composition from both sources and did not decrease in protein content upon spore germination. The water-insoluble glycoprotein was found to be rich in leucine, aspartic acid, glycine, glutamic acid, and phenylalanine residues. The water-soluble glycoprotein was rich in proline, threonine, glycine, serine, glutamic acid, and alanine.

Amino Acids↗