bluuebunny/crossref_metadata_2025 huggingface dataset:
Urea metabolism and urease regulation in the cyanobacterium Anabaena variabilis
Authors: Ge Xin , Cain Karen , Hirschberg Rona
Published: May 2010

Anabaena variabilis can use urea as a nitrogen source, which it breaks down via the action of urease. No evidence of urea amidolyase activity was found. Urease synthesis is constitutive; no major difference in enzyme levels was found when cultures were grown with urea, ammonia, or N2. Urea is not required for urease synthesis, and ammonia does not repress urease synthesis. However, urea does repress nitrogenase synthesis at the transcription level, probably by the same mechanism as ammonia. Anabaena variabilis urease is inhibited by phenylphosphorodiamidate, hydroxyurea, and acetohydroxamic acid, which suggests that the enzyme contains nickel. A Km for urea of 46 μM was observed in crude cell free extracts. The enzyme is cytoplasmic and relatively heat resistant. Key words: urea, urease, cyanobacteria, Anabaena variabilis.
Fluctuations in the fluorescent pseudomonad and actinomycete populations of rhizosphere and rhizoplane during the growth of spring wheat
Authors: Miller H. J. , Liljeroth E. , Henken G. , Veen J. A. van
Published: May 2010

The total bacterial populations, fluorescent pseudomonads, and actinomycetes in the rhizosphere, rhizoplane, and endorhizosphere of two wheat lines (C-R5B and C-R5D) were investigated weekly during plant growth. The total numbers of bacteria (colony-forming units) were counted on a low-nutrient agar medium, while the numbers of fluorescent pseudomonads and actinomycetes were determined by means of selective media. Fluorescent pseudomonads generally constituted less than 0.5% of the total bacterial numbers and the percentage significantly decreased with time in the rhizosphere, rhizoplane, and root-free soil. The percentages of fluorescent pseudomonads were lower in the rhizoplane than in the rhizosphere, and in the endorhizosphere they were barely detectable. The rapid decline of fluorescent pseudomonads frequently observed in survival studies may be explained by the inability of the plant to support this group of bacteria during later development of its rhizosphere. Actinomycetes generally represented no more than 7% of the total bacterial numbers. Actinomycete percentages were highest in the rhizosphere and root-free soil and lowest in the endorhizosphere. Only minor differences were found in total bacterial numbers and in the numbers of fluorescent pseudomonads between the two wheat lines. However, numbers of actinomycetes were significantly different over the whole experiment between wheat line C-R5B and C-R5D in the rhizosphere, rhizoplane, and endorhizosphere. Key words: actinomycetes, bacteria, fluorescent pseudomonads, rhizosphere, sampling time.
Melanin-producing Streptomyces spp. respond to potato plant growth and differentially to potato cultivars
Authors: Keinath Anthony P. , Loria Rosemary
Published: May 2010

Population dynamics of Streptomyces spp. producing melanoid pigments were monitored in field plots planted to the potato cultivars 'Chippewa' (susceptible to common scab) or 'Superior' (resistant), and in fallow control plots. Relative frequencies of streptomycetes most commonly isolated from soil, the rhizosphere, and potato tuber surfaces were determined during two growing seasons. Shannon indices of diversity indicated populations in soils planted to potatoes were more diverse than populations in fallow soil. In 1986, S. diastatochromogenes and S. longisporus accounted for ≥38% of all streptomycetes observed in all three environments. In 1987, S. diastatochromogenes was observed frequently in soil, while S. longisporus was observed rarely in all environments. Relative numbers of three Streptomyces spp. differed in the rhizospheres of 'Chippewa' and 'Superior' (P ≤ 0.05). This is the first report of a differential response of Streptomyces spp. to potato cultivars. Key words: rhizosphere, Solanum tuberosum, Streptomyces spp., melanin.
Étude des interactions hôte–Bifidobacterium chez la souris axénique: caractérisation partielle des facteurs bifidigènes du contenu intestinal
Authors: Romond Marie Bénédicte , Hamze Monzer , Romond Charles , Bourlioux Pierre
Published: May 2010

Growth factors for Bifidobacterium bifidum were detected in faeces of axenic mice strain C3H. Most of these factors were found in the nondialyzable fraction obtained after aqueous extraction and dialysis. SDS–PAGE and filtration chromatography on Sepharose 4B revealed that many glycosylated components harbored a bifidigenic activity. Intestinal colinization of mice by B. bifidum involved the utilization and eventually the disappearance of the intestinal bifidigenic factors. There was no change in the protein concentration in fecal extracts, but the total hexose concentration was lower. Comparison of electrophoretic PAGE profiles after periodic acid Schiff coloration showed that bacteria used up the glycosylated fractions of many glycopeptides, particularly those of mucins and four glycoproteins. There was no correlation between the hexose concentration detected in every active fraction and the degree of in vivo degradation of bifidigenic factors. The attack on active glycopeptides having a molecular mass greater than 670 kDa thus revealed hexose sites that were not detectable previously by the phenol – sulfuric acid method. However, the amount of bifidigenic factors detected in vitro allowed us to measure the importance of the degradation of a component by B. bifidum in vivo. Key words: Bifidobacterium, bifidigenic factors, intestinal mucus, axenic mice. [Journal translation]
Aerobactin uptake system, ColV production, and drug resistance encoded by a plasmid from an urinary tract infection Escherichia coli strain of human origin
Authors: Žgur-Bertok Darja , Modrič Evgenija , Grabnar Miklavž
Published: May 2010

A study of Escherichia coli strains isolated from patients suffering from urinary tract infections in Ljubljana, Yugoslavia, revealed a plasmid encoding the aerobactin iron uptake system, ColV production, and drug resistance. The plasmid is conjugative and at least 85 kilobases in length. Key words: Escherichia coli, plasmid, aerobactin, ColV, resistance.
Lipid metabolism and cell composition of the oleaginous yeast Apiotrichum curvatum grown at different carbon to nitrogen ratios
Authors: Park Wan-Soo , Murphy Patricia A. , Glatz Bonita A.
Published: May 2010

Apiotrichum curvatum ATCC 20509, an oleaginous yeast that can accumulate up to 60% of its cellular dry weight as intracellular lipid when grown with excess carbon, was grown in nitrogen-limited, balanced, and lactose-free medium with asparagine as nitrogen source and lactose as carbon source. Biomass and lipid accumulation were measured, cell composition was analyzed, and catalase activity was followed as marker enzyme for peroxisomes. The organism accumulated 54% of its dry weight as total cellular lipid when grown under nitrogen limitation and accumulated only 20–25% of its dry weight as lipid when grown in balanced medium. When starved for carbon, cells utilized endogenous lipid and carbohydrate as carbon and energy sources; the intracellular contents of lipid and carbohydrate decreased by 31 and 26%, respectively. Intracellular carbohydrates also seemed to be used as intermediates for lipid accumulation and lipid turnover. Catalase activity was strongly induced (over 10-fold increase in specific activity) when cells metabolized endogenous lipid. The lipid content of cells was inversely related to catalase activity and to intracellular protein or total nitrogen content. Lipid content showed no correlation with intracellular carbohydrate content. Key words: lipid, peroxisomes, oleaginous, Apiotrichum curvatum.
Equilibrium analysis of binding of Candida albicans to human buccal epithelial cells
Authors: Staddon William , Todd Tom , Irvin Randall T.
Published: May 2010

The effect of growth temperature on the binding of Candida albicans to human buccal epithelial cells (BECs) was examined using an equilibrium of binding analysis. Candida albicans was cultured in M9 medium either for 12 h at 25 °C or for 9 h at 25 °C and then shifted to 37 °C for 3 h. The temperature shift did not result in germ tube formation; however, the adherence of C. albicans to BECs was altered. Shifting temperature increased the yeast's ability to bind to BECs. A Langmuir adsorption isotherm was used to calculate the maximum number of available binding sites (N) and the apparent association constants of binding (Ka) for all resolvable adhesin–receptor interactions. Three classes of adhesin–receptor interactions were resolved when the yeast was cultured at 25 °C and included a low copy number site (N = 3.0 cfu/BEC; Ka = 2.11 × 10−6 mL/cfu), a medium copy number site (N = 23.6 cfu/BEC, Ka = 8.21 × 10−7 mL/cfu), and a high copy number site (N = 91.7 cfu/BEC, Ka = 3.35 × 10−8 mL/cfu). Two classes of adhesin–receptor interactions were resolved when the incubation temperature was shifted to 37 °C: a low copy number site (N = 4.5 cfu/BEC, Ka = 3.98 × 10−6 mL/cfu) and a high copy number site (N = 150.5 cfu/BEC, Ka = 8.47 × 10−8 mL/cfu). Augmented C. albicans adherence to BECs due to the elevated growth temperatures appears to result from a temperature-regulated alteration in the C. albicans adhesin that recognizes a high copy number receptor site with relatively low affinity.
Studies on transformation in Shigella
Authors: Shireen Tasnina , Sarker Mahfuzur R. , Ahmed Zia U.
Published: May 2010

Transformation of pBR322 DNA into Shigella occurred at a low frequency. The efficiency of transformation was highest in S. dysenteriae 1 and lowest in S. flexneri. Treatment of cells with CaCl2 for a prolonged period (24 h) increased the efficiency of transformation in all strains, except in S. flexneri, where transformation efficiency could not be improved by a variety of manipulations. Transformation efficiency did not increase in any of the strains when transformation was carried out with plasmid DNA obtained from a transformant (homologous transformation), suggesting the absence of a strong restriction–modification system. Extracellular deoxyribonuclease (DNase) levels were low in all the strains tested, but the levels of endogenous DNase, released after CaCl2 treatment or sonication of the cells, were high. Washing the cells with a solution of CaCl2 did not enhance transformation, suggesting that endogenous DNase could be a significant factor affecting transformation efficiency in species of Shigella. Key words: Shigella, transformation, plasmid DNA.
Interaction of iturin A, a lipopeptide antibiotic, with Saccharomyces cerevisiae cells: influence of the sterol membrane composition
Authors: Latoud Chantal , Peypoux Françoise , Michel Georges
Published: May 2010

The binding of the membrane-active lipopeptide antibiotic iturin A to yeast cells was studied using radioactive iturin A. Saccharomyces cerevisiae had a maximum binding capacity of 5.6 × 109 molecules per single cell. The Scatchard plot of binding showed a biphasic profile, with a lower dissociation constant for small concentrations of iturin A. The break of slope at 30 μM iturin A corresponds to the micellization of antibiotic in solution. The binding is also dependent on the nature of the sterol present in the membrane. A mutant yeast strain with a membrane containing cholesterol instead of ergosterol showed the highest affinity for iturin A and the highest sensitivity to this antibiotic, as measured by K+ ion release. In contrast the presence of stigmasterol increased the resistance of the cells to iturin A. Key words: antifungal lipopeptide, iturin A, yeast cell binding capacity, membrane sterol.
Properties of a hemolysin related to the thermostable direct hemolysin produced by a Kanagawa phenomenon negative, clinical isolate of Vibrio parahaemolyticus
Authors: Honda Takeshi , Ni Yuxin , Hata Atsuko , Yoh Myonsun , Miwatani Toshio , Okamoto Tadashi , Goshima Kiyota , Takakura Hikaru , Tsunasawa Susumu , Sakiyama Fumio
Published: May 2010

A hemolytic toxin (Vp-TRH) produced by a Kanagawa phenomenon negative, clinical isolate of Vibrio parahaemolyticus was further characterized. The purified Vp-TRH showed various biological activities, such as fluid accumulation in rabbit ileal loops, increase of rabbit skin vascular permeability, and cardiotoxicity on cultured myocardial cells, all of which are essentially similar to the activities found with thermostable direct hemolysin (Vp-TDH), a pathogenic toxin produced by Kanagawa phenomenon positive V. parahaemolyticus. Immunological similarities of Vp-TRH not only to Vp-TDH but also to hemolytic toxins produced by Vibrio hollisae and Vibrio cholerae non-O1, both of which are also enteropathogens closely related to V. parahaemolyticus, were demonstrated. The amino acid composition and sequence of N-terminal amino acids of Vp-TRH were determined. These results suggest that Vp-TRH has biological and immunological characters similar to Vp-TDH, although they are distinct molecules. Key words: thermostable direct hemolysin, Vibrio parahaemolyticus, Kanagawa phenomenon.
Changes in membrane lipids and amino acid transport in a nystatin-resistant Aspergillus niger
Authors: Mazumder Chitra , Basu Joyoti , Kundu Manikuntala , Chakrabarti Parul
Published: May 2010

A nystatin-resistant mutant of Aspergillus niger is described that has quantitative changes in phospholipid composition compared with the wild type. The proportion of linoleic acid in total phospholipids was elevated in the mutant from 38 to 56% and the proportion of oleic acid was lowered from 28 to 12%. Amino acid transport is also altered, the Vmax values for the uptake of leucine, lysine, and glutamic acid being generally higher in the mutant; for glutamic acid the increase was from 15 to 35 nmol∙mg−1∙min−1. Key words: Aspergillus niger, nystatin resistance, phospholipid composition, amino acid transport.
The fine structure of Thioploca araucae and Thioploca chileae
Authors: Maier Siegfried , Völker Horst , Beese Marita , Gallardo Victor A.
Published: May 2010

Thioploca araucae and Thioploca chileae from the sublittoral soft bottoms of the coastal upwelling ecosystem off central Chile were examined by scanning and transmission electron microscopy. Except for filament diameter (30–43 and 12–20 μm, respectively) and slight differences in other dimensions and surface topology, the details of fine structure were essentially identical in the two species. The wall consisted of five layers, and only the inner layer was present in the septum. Multiple membrane intrusions dissected the procaryotic cytoplasmic material, which was restricted to a relatively thin layer within the wall. Sulfur inclusions and two other extracytoplasmic inclusions, as well as one kind of intracytoplasmic inclusion, were described. The central part of each cell consisted of one large vacuole, extending from septum to septum and representing a volume at least more than three times larger than the combined volume of wall and cytoplasm. The vacuole was separated from the other cell parts by a membrane. Electron-dense material was deposited between vacuole membrane and plasma membrane, between plasma membrane and wall, and inside membrane intrusions. A continuity between the vacuolar membrane and the other membranes was never encountered. The possible origin of such an extracytoplasmic membrane is discussed. Key words: benthos, electron microscopy, fine structure, Thioploca.
Catalase activity in Campylobacter jejuni: comparison of a wild-type strain with an aerotolerant variant
Authors: Vercellone Pamela A. , Smibert Robert M. , Krieg Noel R.
Published: May 2010

A comparison of Campylobacter jejuni VPI strain H840 (ATCC 29428), which can grow at O2 levels up to 15%, with variant strain MC711-01 (which can grown at O2 levels up to 21–26%) indicated that the specific activity of catalase in crude cell extracts was higher in the variant by a factor of 1.6 to 2.5, depending on cultural conditions. Smaller differences occurred with superoxide dismutase activity, while peroxidase activities were invariably lower in the variant strain. The variant strain was much more resistant than the wild type to the bactericidal effects of H2O2. The results suggest that catalase activity might be one of the factors associated with the greater tolerance of O2 by the variant strain. However, both strains became more susceptible to H2O2 when cultures were initially grown at 6% O2 and then shifted to 21% O2; thus the role of catalase in the oxygen tolerance of C. jejuni is probably minor. Key words: Campylobacter jejuni, catalase, oxygen tolerance.
Incidence of bacteriocinogeny among fresh isolates of Streptococcus mutans
Authors: Parrot M. , Dréan M.-F. , Trahan L. , Lavoie M. C.
Published: May 2010

Among 139 Streptococcus mutans fresh isolates tested, using the deferred-antagonism test and Streptococcus sanguis Ny 101 as the indicator strain, we observed that the frequency of detection of inhibition zones was reduced by 19% (from 53 to 34%) when arginine (1%) was used in the overlay agar. Among pigmented strains, the frequency of mutacin-like production was 70%. The frequency with which inhibition zones were detected varied from 7 to 91%, depending on the indicator strain used. These results indicate that the ability to detect the presence of mutacin-like substances varies widely and is dependent to a great extent on the methodology used. Key words: mutacin, bacteriocin, antagonism, Streptococcus mutans, inhibitory substance.
Ammonia-induced cell envelope injury in Escherichia coli and Enterobacter aerogenes
Authors: Naundorf Gerardo , Aumen Nicholas G.
Published: May 2010

Ammonia-induced cell envelope injury was examined in pure cultures of Escherichia coli and Enterobacter aerogenes. Cell injury, as determined by the ratio of colony-forming units on m-T7 agar to colony-forming units on m-Endo agar, increased with exposure to increasing concentrations of ammonia. Cell envelopes appeared to be the site of injury as indicated by increasing susceptibility to lysozyme with increasing ammonia concentration. Cells exposed to ammonia also exhibited more cellular leakage than control cells. Leakage from cells exposed to ammonia included proteins, and all leaked substances increased in concentration as ammonia concentrations increased. The concentration of 2-keto-3-deoxyoctonate (KDO) in the outer membrane of E. coli increased with ammonia exposure, while KDO concentration in the outer membrane of E. aerogenes decreased. The results suggest that exposure of E. coli cells to high concentrations of ammonia disrupts the outer membrane and lipopolysaccharide-associated proteins, while E. aerogenes cells are affected through the disruption of bonds between KDO and the outer membrane. Key words: injury, coliform, ammonia, cell envelope.
Improved detection of acid mine water stressed coliform bacteria on media containing catalase and sodium pyruvate
Authors: Calabrese Joseph P. , Bissonnette Gary K.
Published: May 2010

Pure culture suspensions of two strains of exponential and stationary phase Escherichia coli exhibited significant reductions in catalase activity following exposure to acid mine water (AMW). The exogenous addition of catalase (500–2000 U) or sodium pyruvate (0.05–5%) to a nonselective recovery medium resulted in enhanced detection (12- to 465-fold) of AMW-stressed E. coli as compared with recovery on the medium lacking these supplements, whereas addition of 3,3′-thiodipropionic acid failed to improve recovery. Additional in vitro experiments utilizing selective M-FC, mT7, and M-Endo media containing 1000 U catalase or 1.0% pyruvate similarly resulted in improved detection of AMW-stressed cells, with the exception of M-Endo containing pyruvate. Appropriately modified media were then used to analyze an AMW-impacted stream by the membrane filtration technique. Addition of catalase, pyruvate, or a combination of both significantly improved recovery of fecal and total coliforms without promoting growth of noncoliforms. Supplementation of plate count agar with pyruvate and (or) catalase enhanced detection of total heterotrophs. These findings suggest that addition of catalase or pyruvate to standard recovery media may improve detection of coliform and total heterotrophic bacteria in AMW-impacted waters. Key words: acid mine water, coliforms, stress.
Polyamines and their biosynthetic activities in nonphytopathogenic marine agrobacteria
Authors: Amana Koei H , Matsuzaki Shigeru
Published: May 2010

Eight strains of nonphytopathogenic agrobacteria, whose taxonomic positions are uncertain, were analyzed for their polyamine contents and their polyamine biosynthetic activities. They were separated into five types on the basis of polyamine distribution patterns. The first group contains putrescine, cadaverine, and spermidine as major polyamines, the second spermidine alone, the third cadaverine alone, the fourth putrescine, spermidine, spermine, homospermidine, and aminopropyl-homospermidine, and the last contains trace amounts of diaminopropane and spermidine. These polyamine patterns of eight species seem to suggest no close phylogenic relationship among these agrobacteria and are different from those of other typical, phytopathogenic species belonging to Agrobacterium. Key words: agrobacteria, decarboxylases, polyamines, homospermidine, aminopropylhomospermidine.
Bactericidal activity of magainin 2: use of lipopolysaccharide mutants
Authors: Macias Elizabeth A. , Rana Fazale , Blazyk Jack , Modrzakowski Malcolm C.
Published: May 2010

Salmonella typhimurium and a series of rough lipopolysaccharide mutants derived from it were used as target bacteria to examine the antimicrobial capacity of magainin 2. Magainin 2 demonstrated a dose-related bactericidal activity against the smooth parent strain and the series of lipopolysaccharide mutants. The lipopolysaccharide mutant series showed an ordered increase in sensitivity to the magainin 2 as the depth of the rough lesion in the lipopolysaccharide increased. Key words: Salmonella typhimurium, lipopolysaccharide, antimicrobial capacity, magainin.
Recherches sur le mode d'action d'un antifongique non polyénique (désertomycine) produit par une souche de Streptomyces spectabilis
Authors: Benallaoua S. , Van P. Nguyen , Meo M. P. De , Coulon J. , Dumenil G. , Bonaly R.
Published: May 2010

A metabolite with antifungal activity, of non polyenic macrolide structure, was extracted and purified from the culture supernatant of a soil-isolated Streptomyces spectabilis strain, BT 352. This product was found to be related to (or being) desertomycin. Six yeast and five filamentous fungus strains were used to determine minimum concentration of the metabolite that inhibits growth by 80% (IMC); it was established at 50 μg/mL for the fungi and at 100 μg/mL or more for the yeasts tested. Short-term genotoxicity tests showed no antifungal effect on the bacterial genome, and desertomycin at concentration levels of 100 μg/mL or more affected protein synthesis. The antifungal metabolite had no immediate inhibiting effect upon yeast respiration, even at high concentrations; however, the respiration activity of cells grown in the presence of subinhibiting doses and collected during their growth phase was reduced by as much as 40%. Saccharomyces uvarum spheroplast regeneration in a liquid medium containing desertomycin was inhibited at doses fivefold weaker than the IMC determined with intact cells. Contrary to amphotericin B, desertomycin subinhibiting doses do not modify, and if so lightly, the yeast latent phase or the spheroplast wall regeneration phase, thus indicating a fungicidal action. Moreover, following a 30-min contact with desertomycin subinhibiting and inhibiting doses, yeasts liberated potassium in large amounts, indicating that plasma membranes were affected. Key words: Streptomyces spectabilis, desertomycin, antifungal activity, genotoxicity, yeast. [Translated by the journal]
Recherche de nouvelles activités saccharifiantes thermostables chez les champignons filamenteux
Authors: Vanacker P. , Bacle B. , Vidal G. , Lacoste L.
Published: May 2010

We have searched for producers of a saccharifying activity with improved thermostability compared with industrial amyloglucosidases. These producers were chosen among thermophilic, thermotolerant, or even mesophilic fungi. Among the 846 isolated strains, five species (two Thermoascus spp., a member of the Aspergillus fumigatus group, and two members of the Aspergillus niger group) showed an amyloglucosidasic complex with the required property. Whereas the first three of these were thermophilic or thermotolerant strains, the latter two strengthen the idea that mesophilic strains can produce thermostable enzymes. The thermostability of the saccharifying complex of the Thermoascus spp., established with a half-life measure, was found to be far better than the other ones. The industrial use of these strains was discussed, and Thermoascus crustaceus seems to be the most advantageous one. Key words: filamentous fungi, amyloglucosidases, thermostability, Thermoascus.
Growth of Frankia in the rhizosphere of Betula pendula, a nonhost tree species
Authors: Smolander A. , Rönkkö R. , Nurmiaho-Lassila E.-L. , Haahtela K.
Published: May 2010

The growth of Frankia in the rhizosphere of Betula pendula was studied to understand the favourable effect of this nonhost species on Alnus-nodulating Frankia in soil. Axenic Betula pendula and Alnus incana seedlings were inoculated with Frankia strains. The development of Frankia in the rhizosphere was examined by light and scanning electron microscopy. Some Frankia strains grew in the rhizosphere of Betula pendula seedlings without addition of a carbon and energy source. In addition to hyphae and sporangia, vesicles were also formed. Growth (if any) was more local and less abundant in the rhizosphere of Alnus incana seedlings. Frankia strains were grown in defined medium supplemented with tryptophan. Indole-3-ethanol was detected in the culture solution by gas chromatography – mass spectrometry. Key words: Alnus incana, Betula pendula, Frankia, indole-3-ethanol.
Detection and identification of poliovirus in environmental samples using nucleic acid hybridization
Authors: Preston David R. , Chaudhry G. Rasul , Farrah Samuel R.
Published: May 2010

A procedure was developed to effectively extract viral RNA from poliovirus tissue-culture lysates while eliminating the hybridization background associated with tissue cultures uninfected with poliovirus. Poliovirus cDNA cloned into a pUC vector was used as probe. Both the recombinant plasmids and the cDNA showed great specificity towards poliovirus. However, both probes hybridized with the single-stranded DNA coliphage [Formula: see text]. Tissue culture was found to be an effective method to increase the number of viruses found in environmental samples to a level detectable by hybridization procedures, whereas direct hybridization of RNA from unamplified and highly concentrated raw wastewater showed poor hybridization signals. The specificity and sensitivity of the hybridization procedure developed during these studies indicate that this method may be best suited for the identification rather than the detection of viruses isolated from environmental samples. Key words: nucleic acid hybridization, polio virus, water, dot blot.
Ontological and environmental influences on ergosterol content and activities of polyamine biosynthesis enzymes in Hebeloma crustuliniforme mycelia
Authors: Johnson B. N. , McGill W. B.
Published: May 2010

Analyses of ergosterol and activities of arginine decarboxylase (ADC) and ornithine decarboxylase (ODC) were used as estimates of fungal mass and metabolic activity, respectively, in aerial mycelia of Hebeloma crustuliniforme (Bull.: St. Amans) Quel. Omission of inorganic P from the medium decreased the ergosterol concentration of perimeter mycelia by 15–30% and increased ADC and ODC activities up to 6-fold. The magnitude of changes with omission of glucose C were similar but the trend was reversed. Ergosterol content and enzyme activities differed among colony locations; perimeter mycelia contained up to 1.8 times more ergosterol and up to 3.6 times more ADC and ODC activity per gram than mycelia at the core. Ergosterol mass and colony mass were positively correlated; the equation Y = −5.46 + 0.38(X), where Y = mycelia mass (mg) and X = ergosterol mass (μg), accounted for 77% of the variance in colony mass. The ratio of ODC:ADC activity was 21 at the perimeter and 30 at the core; activity ratios may be used to infer maturation state of a fungal colony. Potential application of ergosterol content and activities of ADC and ODC as biochemical indices in mycological research is discussed. Key words: arginine decarboxylase, colony development, ergosterol, Hebeloma, ornithine decarboxylase.
Homology among bacterial catalase genes
Authors: Switala Jacek , Triggs-Raine Barbara L. , Loewen Peter C.
Published: May 2010

Catalase activities in crude extracts of exponential and stationary phase cultures of various bacteria were visualized following gel electrophoresis for comparison with the enzymes from Escherichia coli. Citrobacter freundii, Edwardsiella tarda, Enterobacter aerogenes, Klebsiella pneumoniae, and Salmonella typhimurium exhibited patterns of catalase activity similar to E. coli, including bifunctional HPI-like bands and a monofunctional HPII-like band. Proteus mirabilis, Erwinia carotovora, and Serratia marcescens contained a single band of monofunctional catalase with a mobility intermediate between the HPI-like and HPII-like bands. The cloned genes for catalases HPI (katG) and HPII (katE) from E. coli were used as probes in Southern hybridization analyses for homologous sequences in genomic DNA of the same bacteria. katG was found to hybridize with fragments from C. freundii, Ent. aerogenes, Sal. typhimurium, and K. pneumoniae but not at all with Ed. tarda, P. mirabilis, S. marcesens, or Er. carotovora. katE hydridized with C. freundii and K. pneumoniae DNAs and not with the other bacterial DNAs. Key words: catalase genes, bacteria, homology.
Inactivation of viral agents in bovine serum by gamma irradiation
Authors: House Carol , House James A. , Yedloutschnig Ronald J.
Published: May 2010

Cell culture origin or suckling mouse brain origin viruses of Akabane disease, Aino, bovine ephemeral fever, swine vesicular disease, hog cholera, bluetongue, and minute virus of mice were each suspended in bovine serum. Aliquots (1 mL) were exposed to various doses of gamma radiation from a 60Co source while at −68 °C. Aliquots (100-mL) of serum from a steer experimentally infected with foot-and-mouth disease virus were similarly irradiated. The samples were assayed for infectivity in cell culture systems before and after irradiation, and the data points were analyzed by linear regression. The irradiation doses (in megarads) necessary to inactivate one log10 of viral infectivity (D10) was calculated for each virus. D10 is otherwise known as the slope of the regression line. The r2 value, a measure of association with 1.0 = perfect fit, was also calculated for each regression line. The values (D10, r2) for each virus were as follows: Akabane, 0.25, 0.998; Aino, 0.35, 0.997; bovine ephemeral fever, 0.29, 0.961; swine vesicular disease, 0.50, 0.969; foot-and-mouth disease, 0.53, 0.978; hog cholera, 0.55, 0.974; bluetongue, 0.83, 0.958; and minute virus of mice, 1.07, 0.935. Key words: irradiation, bovine serum, viral agents.
Production of amylases by yeasts
Authors: Linardi Valter R. , Machado Katia M. G.
Published: May 2010

Yeasts (228) isolated for natural habitats were screened for their ability to produce amylases in semisolid medium of wheat bran. Strains of Aureobasidium pullulans, Candida famata, and Candida kefyr showed high enzymatic activity for α-amylase, glucoamylase, and debranching enzyme. Key words: Aureobasidium, Candida, amylolytic yeasts, α-amylase, glucoamylase.
Selection of strains of Epicoccum purpurascens for tolerance to fungicides and improved biocontrol of Sclerotinia sclerotiorum
Authors: Zhou Ting , Reeleder R. D.
Published: May 2010

A wild-type isolate of Epicoccum purpurascens was exposed to shortwave ultraviolet light. One of the resulting cultures (M-20-A) was grown on media amended with the fungicides iprodione or vinclozolin and fungicide-tolerant strains were obtained. Several comparisons were made between new strains and the wild type. Sporulation was improved compared with the wild type. Strains varied in their tolerance to iprodione and vinclozolin but were not tolerant to the fungicide benomyl. Strains R4000, 16-B, and 7-A inhibited Sclerotinia sclerotiorum in vitro more than either the wild type or M-20-A, and exhibited improved control of white mold of bean in the greenhouse compared with M-20-A. Key words: biological control, fungicide resistance, white mold, iprodione, vinclozolin.
Glucose oxidase as the antifungal principle of talaron from Talaromyces flavus
Authors: Kim Kay Kwang-Ae , Fravel Deborah R. , Papavizas G. C.
Published: May 2010

Analysis of an authentic sample of the antifungal antibiotic talaron from the biocontrol fungus Talaromyces flavus indicated that approximately 40% of the solid sample was glucose oxidase. High-performance liquid chromatography elution profiles of the antimicrobial activity of talaron coeluted with those of glucose oxidase. Fluorescence emission and excitation wavelength maxima for talaron were similar to those of glucose oxidase from Aspergillus niger. The molecular weight of talaron was 152 000 with a subunit molecular weight of 71 000. The isoelectric point of talaron was pH 4.2. Mobilities of talaron on native, sodium dodecylsulfate, and isoelectric focusing polyacrylamide gels were identical with those of glucose oxidase produced by T. flavus. Furthermore, talaron had antimicrobial activity only in the presence of glucose. Hydrogen peroxide produced by the action of glucose oxidase is toxic to Verticillium dahliae. This study indicates that the antifungal activity of authentic talaron resulted from glucose oxidase produced by T. flavus. Key words: biological control, glucose oxidase, hydrogen peroxide, talaron, Talaromyces flavus, Verticillium dahliae.
Dissimilatory ammonia production vs. denitrification in vitro and in inoculated agricultural soil samples
Authors: Fazzolari E. , Mariotti A. , Germon J. C.
Published: May 2010

A dissimilatory ammonia-producing isolate identified as Enterobacter amnigenus and a denitrifier identified as Agrobacterium radiobacter isolated from the same soil were studied. The products of nitrate reduction in a minimal medium, enriched with glucose and containing nitrate N as the sole nitrogen source, were quantified when each of these isolates was cultured anaerobically, alone or mixed together in the presence or absence of C2H2. When they were cultured together, ammonia was the principal product of nitrate reduction. The distribution between denitrification and dissimilatory ammonia production (DAP) for nonsterilised soil samples inoculated with E. amnigenus or A. radiobacter, or a mixture of these two isolates, was also investigated. Production of NH4+ was increased under these conditions (strict anaerobiosis and much available fermentable carbon), but the inoculation of soil samples with 1.2 × 107 cells of E. amnigenus·g dried soil−1 was not sufficient to shift nitrate reduction from nitrous oxide (denitrification) to ammonia production, suggesting that inoculation with a greater number of DAP bacteria than introduced would probably be required to enable ammonia production to exceed nitrous oxide release. Key words: dissimilatory ammonia production, denitrification, Enterobacter amnigenus, Agrobacterium radiobacter.
Role of the gut proteinases from mosquito larvae in the mechanism of action and the specificity of the Bacillus sphaericus toxin
Authors: Nicolas Luc , Lecroisey Anne , Charles Jean-François
Published: May 2010

Gut proteinases from larvae of mosquito species both susceptible and not susceptible to Bacillus sphaericus converted the 43-kDa toxin to a 40-kDa polypeptide exhibiting enhanced cytotoxicity to mosquito cell cultures. The toxin was also activated by gut proteinases from the nonsusceptible Lepidoptera Spodoptera littoralis in vitro and in vivo. Therefore, the specificity of Bacillus sphaericus toxin does not seem to be determined by gut proteinase action. However, susceptibility of mosquito cell cultures did not reflect the specificity of the toxin, which must now be investigated at the cellular level in the larvae. Key words: mosquitoes, Bacillus sphaericus, bacterial toxins, proteinases, specificity.
Degradation of dimethyl nitrosamine by Methylosinus trichosporium OB3b
Authors: Yoshinari Tadashi , Shafer David
Published: May 2010

The degradation of dimethyl nitrosoamine (DMNA) by a methanotroph, Methylosinus trichosporium OB3b, was studied using 14C-labelled DMNA. The organism was capable of assimilating DMNA-carbon and converting it to CO2. The rates of CO2 production [Formula: see text] from DMNA and its cellular uptake (VP) were linearly correlated with DMNA concentrations of 0.03–10 mM, which corresponded to approximately 3% of added DMNA metabolized in 24 h. These rates were two to three orders of magnitude less than the rate of uptake of methane [Formula: see text], [Formula: see text] was suppressed when the concentrations of DMNA exceeded 0.3 mM. In the presence of 0.1 mM DMNA, VP and [Formula: see text] were essentially the same in the presence or absence of methane in the first 8 h of incubation, but declined sharply thereafter only when methane was absent. These observations suggest that the metabolism of DMNA was carried out by methane monooxygenase (MMO), and that NADH, a cofactor for MMO, may be provided by the oxidation of the stored compounds in the cells when methane is not available. Key words: dimethyl nitrosamine, degradation, Methylosinus trichosporium, methane monooxygenase.
Shelf life of phosphate-solubilizing inoculants as influenced by type of carrier, high temperature, and low moisture
Authors: Gaind S. , Gaur A. C.
Published: May 2010

A charcoal–soil mixture, paddy straw compost, and wheat bran were tested to explore their possible use as carriers for phosphate-solubilizing bacteria and fungi. The charcoal–soil mixture was found to be the best carrier for phosphate-solubilizing bacteria, and wheat bran, for phosphate-solubilizing fungi. Higher temperatures during storage markedly influenced the shelf life of phosphate-solubilizing microorganisms. Thermotolerant strains, such as Bacillus subtilis, Bacillus circulans, and Aspergillus niger, were found to survive not only at high storage temperatures (40 and 45 °C), but also at low moisture status in the carrier. Key words: inoculum carriers, thermotolerant strains, shelf life.
Expression of a Bacillus thuringiensis crystal protein gene in Pseudomonas cepacia 526
Authors: Stock Carolyn A. , McLoughlin Thomas J. , Klein Janet A. , Adang Michael J.
Published: May 2010

An insecticidal crystal protein gene, cryIA(C), from Bacillus thuringiensis HD-1 was cloned into a broad host range vector, pSUP204, and the resulting plasmid, pSUP89A, was conjugated into a plant-colonizing bacterium, Pseudomonas cepacia 526. Southern blot analysis detected the presence of the cry gene in Pseudomonas cepacia 526 transconjugants. Production of a truncated insecticidal crystal protein in Pseudomonas cepacia was detected by Western blotting and ELISA techniques and was found to have insecticidal activity against the tobacco hornworm, Manduca sexta, in an artificial diet assay. We also followed the establishment of the Pseudomonas cepacia 526/Bt transconjugant on axenically grown tobacco plants and found that approximately 1% of the Pseudomonas cells retained pSUP89A 3 days after application. In spite of this instability, treated tobacco plants were protected from Manduca sexta infestation. Key words: Bacillus thuringiensis, Pseudomonas cepacia, insecticidal crystal protein, Cry protein.
Antibiotic resistance indexing of Escherichia coli to identify sources of fecal contamination in water
Authors: Kaspar Charles W. , Burgess Janie L. , Knight Ivor T. , Colwell R. R.
Published: May 2010

A total of 202 Escherichia coli isolated from urban and rural water were tested with 11 antibiotics to assess the prevalence of antibiotic resistance from each source. Urban waters harbored higher percentages of resistant E. coli strains than rural waters. Antibiotic-resistant E. coli may offer an index of water quality related to source. Key words: Escherichia coli, antibiotic resistance, indicator.
Purification and characterization of intracellular proteases of Clostridium perfringens type A
Authors: Park Kyong Bin , Labbé Ronald G.
Published: May 2010

Five intracellular proteases from sporulating cells of Clostridium perfringens type A were identified and three could be separated by DEAE–Sephacel. Two, I-A and I-B, had caseinolytic activity and one, I-C, was only active on N-benzoyl-DL-arginine-p-nitroanilide. I-A and I-B could each be further separated by Sephacryl S-300 into I-A-1 and I-A-2 and I-B-1 and I-B-2, respectively. I-A-1, a chymotrypsin-like enzyme, was the major intracellular protease, constituting 74% of the intracellular caseinolytic activity. In addition to cytoplasmic proteases both trypsin and chymotrypsin-like enzyme activity was associated with the membrane fraction. I-A-1 had a molecular weight of 330 000, with subunits of 120 000 and 138 000. I-A-1 cleaved a 1200 molecular weight peptide from C. perfringens enterotoxin. Early sporulating cell extracts of C. perfringens contained three presumptive enterotoxin precursors, which disappeared following treatment with I-A. Such cells also contained at least 10 spore coat related proteins, only one (51 500 molecular weight) of which was sensitive to I-A-1. The results indicate a possible role for the major intracellular protease in the processing of C. perfringens enterotoxin and a less important role, if any, in spore coat formation. Key words: Clostridium perfringens, protease, spores, sporulation.
Nodulation competitiveness of Tn5-induced mutants of Rhizobium fredii USDA208 that are altered in motility and extracellular polysaccharide production
Authors: Zdor Robert E. , Pueppke Steven G.
Published: May 2010

The role of motility and extracellular polysaccharide production in nodulation competitiveness of Rhizobium fredii was examined. Transposon Tn5 was used to mutagenize strain USDA208, and mutants with reduced motility on semisolid agar medium were isolated. One such mutant, 208M3, migrated to only one-seventh the distance of the parental strain. Solid medium amended with triphenyltetrazolium chloride was used to identify mutants altered in extracellular polysaccharide production. Type 1 colonies, typified by mutant 208T13, were heavily mucoid, while type 2 colonies, represented by mutant 208T3, were dry and nonmucoid. Compared with strain USDA208, these mutants produced 4- to 5-fold more extracellular polysaccharide and 20% as much extracellular polysaccharide, respectively. Marker exchange of 208T3 genomic DNA containing Tn5 into strain USDA208 resulted in a mutant, 208K1, that produced extracellular polysaccharide levels similar to mutant 208T3. Mutants 208M3, 208T3, and 208T13 contained single Tn5 insertions. All formed pink nodules on 'Peking' soybean that were structurally indistinguishable and contained proteins with similar profiles. Rates of nodulation were similar in the mutants and the parental strain. Mutants 208M3 and 208T13 were as competitive against an isolate of Bradyrhizobium japonicum serogroup 123 as was strain USDA208. In contrast, mutants 208T3 and 208K1 were competitively superior. Key words: nodulation competition, motility, extracellular polysaccharide, Rhizobium.
Unusual association of a plasmid with nalidixic acid resistance in an epidemic strain of Shigella dysenteriae type 1 from Asia
Authors: Ashraf M. Musharraf , Ahmed Zia U. , Sack David A.
Published: May 2010

The association of a 20-MDa plasmid with nalidixic acid resistant (Nalr) strains of Shigella dysenteriae 1 has been examined. The plasmid, which is readily transferable, does not itself code for nalidixic acid resistance but offers a survival advantage to its host under nalidixic acid stress. The plasmid-containing cultures of S. dysenteriae 1 produced Nalr mutants in vitro at a frequency 1000-fold higher than their plasmidless parent strains, after two exposures to nalidixic acid. Using a similar procedure, mutants resistant to other antibiotics such as chloramphenicol, tetracycline, or ciprofloxacin could not be isolated. The genome of S. dysenteriae 1 appears to carry a heavy load of the insertion sequence IS1. The propensity of the plasmid-containing strains to readily mutate to nalidixic acid resistance and its possible relevance to the observed association of the plasmid with Nalr clinical isolates is discussed. Key words: Shigella, nalidixic acid, plasmid, shigellosis.
Phosphatase activity during development cycle of Myxococcus xanthus
Authors: Gonzalez Francisco , Vargas Antonio , Arias Jose M. , Montoya Enrique
Published: May 2010

Cell-bound and extracellular acid and alkaline phosphatase activity have been studied in Myxococcus xanthus strains DK101, DK1050, DK2834, and DK2836. Both phosphatases were released into a liquid medium during vegetative growth and the levels were similar in all strains. On solid media, M. xanthus DK101 showed maximum activity at the end of the developmental process, when mature myxospores appeared. An increase in phosphatase activity was also observed in glycerol-induced myxospores. A transitory increase in phosphatase activity occurred during the germination of both glycerol-induced and fruiting-body myxospores, although the activity of both phosphatases in fruiting-body myxospores was greater than that in glycerol-induced ones. Key words: acid phosphatase, alkaline phosphatase, Myxococcus xanthus.
Colicinogeny of O157:H7 enterohemorrhagic Escherichia coli and the shielding of colicin and phage receptors by their O-antigenic side chains
Authors: Bradley D. E. , Howard S. P. , Lior H.
Published: May 2010

Twenty O157:H7 enterohemorrhagic Escherichia coli strains from patients with different clinical conditions were tested for colicinogeny and the presence of Verotoxin (VT) genes. From bloody diarrhea cases, 7/8 isolates and from hemolytic uremic syndrome cases 3/5 isolates all synthesized what appeared to be colicin D. The remaining strains, which included 7 from asymptomatic sources, were noncolicinogenic. The plasmid determining the colicin was found to be 1.4 kb larger than the 5.2-kb pColD. The colicin D protein had a molecular weight of about 90 000, whereas the O157 colicin was 87 000. The plasmid was designated pColD157 to reflect these differences. Of O157:H7 isolates 17/20 had genes for both of the Verotoxins VT1 and VT2, and the remaining 3/20 for VT1 only. There was no correlation between the presence of VT determinants and colicinogeny or symptoms. The O157:H7 strains exhibited significant resistance to other colicins and bacteriophages. Key words: O-antigens, enterohemorrhagic, colicin, Verotoxin, bacteriophages.
Gene expression associated with light-induced conidiation in Colletotrichum graminicola
Authors: Yang Zhenfan , Panaccione Daniel G. , Hanau Robert M.
Published: May 2010

Light was used to induce conidiation in uniform populations of vegetative hyphae of Collectotrichum graminicola grown on agar medium. Differentiation of conidiogenous cells, the first detectable event in conidial morphogenesis, was rapid and highly synchronized. In vitro translation of poly(A)+ RNA from dark-grown (nondifferentiating) and light-induced (differentiating) hyphae demonstrated that conidiogenous cell development was accompanied by detectable changes in gene expression. Key words: Colletotrichum, conidia, asexual development, conidiogenous cell, light induction.