bluuebunny/crossref_metadata_2025 huggingface dataset:
Fimbrial-dependent mating inMicrobotryum violaceuminvolves a mannose–lectin interaction
Authors: Castle Alan J. , Stocco Nadia , Boulianne Robert
Published: February 2010

Fimbriae of the anther smut fungus, Microbotryum violaceum are polymers of six 74-kDa glycoprotein isoforms. Digestion of fimbrial monomers with α-mannosidase yielded two polypeptides with masses of 70 and 48 kDa. The 70-kDa polypeptide is probably a product of incomplete digestion and the 48-kDa polypeptide is the aglycone. Thus, most of the carbohydrate component of fimbrial protein is mannose. Previous observations have suggested that fimbriae are necessary for mating in M. violaceum. Further evidence for this role was obtained in the present study by showing that mating is inhibited by an anti-fimbrial protein antiserum, by mannose and related sugars glucose and arabinose, and by the lectin concanavalin A. Since inhibition was not complete, however, two mechanisms for adhesion between compatible cells were proposed, one fimbrial dependent and one independent. Lastly, fimbrial protein from a1but not a2mating types bound to a mannose–agarose column, suggesting a lectin-like capability. The fimbrial dependent mechanism of cell-to-cell adhesion may involve binding of the mannose residues of the fimbriae of a2cells by the fimbriae of a1cells.Key words: mating, Microbotryum violaceum, lectin, fimbriae.
Isolation and characterization ofAzospirillum lipoferumlocus that complementsRhizobium meliloti dctAanddctBmutations
Authors: Tripathi A. K. , Mishra B. M.
Published: February 2010

A DNA probe containing the structural gene for dicarboxylate transport (dctA) of Rhizobium meliloti hybridized strongly with the fragments of Azospirillum lipoferum genomic DNA. A genomic library of A. lipoferum was screened for the dctA gene by complementation of a dctA mutant of Rhizobium meliloti. A recombinant cosmid, p37D, capable of restoring growth of the dctA mutant on dicarboxylates was isolated and found to hybridize to the dctA probe. The ability of p37D to complement the dctB mutant of R. meloliti indicated that dctA and dctB genes in A. lipoferum may be organized adjacent to each other.Key words: Azospirillum lipoferum, dicarboxylate transport gene, complementation cloning.
Electrophoretic characterization of endo-(1,4)-β-glucanases secreted during assimilative growth and antheridiol-induced branching inAchlya ambisexualis
Authors: Hill Terry W.
Published: February 2010

Secreted endo-(1,4)-β-glucanases ("cellulases") of Achlya ambisexualis were analyzed by a technique that permits visualization of enzyme activity in situ after electrophoresis in gels containing sodium dodecyl sulfate. Catalytic polypeptides with molecular masses of about 97, 74, 36, 29, and 25 kDa were observed in media from young cultures, though progressively fewer bands were observed as cultures aged. Based on size estimations of native enzymes with gel exclusion chromatography, the 97- and 36-kDa polypeptides were concluded to be subunits of a 245-kDa holoenzyme and the 25-kDa polypeptides were concluded to be subunits of a second holoenzyme of about 92 kDa. The data were insufficient to allow similar assignments for the more ephemeral 74- and 29-kDa polypeptides. The endoglucanases secreted during branch induction by antheridiol or 0.2% peptone comigrated in electrophoretic gels with enzymes secreted during normal assimilative growth. No endoglucanases specific to induced branching were observed.Key words: oomycetes, cell walls, endoglucanases, cellulases, antheridiol.
The biotransformation of chrysene totrans-1,2-dihydroxy-1,2-dihydrochrysene by filamentous fungi
Authors: Kiehlmann Eberhard , Pinto Linda , Moore Margo
Published: February 2010

The purpose of this study was to assess the ability of filamentous fungi isolated from petroleum-contaminated soils to oxidize chrysene. Only 4 of the 17 isolates known to oxidize pyrene and benzo[a]pyrene were found to produce polar products when incubated in the presence of chrysene and Tween 80: Penicillium janthinellum, Syncephalastrum racemosum, and 2 Penicillium spp. Trows-1,2-dihydroxy-1,2-dihydrochrysene was identified by1H-NMR as one of three fungal metabolites. The extent of bioconversion to diol was approximately 3% of chrysene in 6 days. Experiments to increase chrysene oxidation with other polycyclic aromatic hydrocarbons were not successful. To our knowledge, this is the first identification of a chrysene metabolite from any microorganism and the first report of fungal oxidation of chrysene.Key words: chrysene, polycyclic aromatic hydrocarbons, filamentous fungi, bioremediation, cytochrome P450.
Value of substrate utilization data for characterization of Mucor isolates
Authors: Vágvölgyi Csaba , Magyar Klaudia , Papp Tames , Palágyi Zsuzsanna , Ferenczy Lajos , Nagy Ágnes
Published: February 2010

Twenty-seven strains representing 10 Mucor species were assayed for their ability to utilize various substrates as carbon sources. They were also examined for their exoenzyme activities by means of the API-ZYM microtest system. Cluster analysis of resulting data revealed a loose correlation between these physiological patterns and the species designation of the isolates. Though different strains of the same species often vary in their substrate utilization abilities, the value of this approach to provide complementary data for the characterization of Mucor isolates has been demonstrated.Key words: Mucor, substrate utilization, API-ZYM, numerical taxonomy.
Modulation of protein profiles inRhizobiumsp. under salt stress
Authors: Saxena Deepti , Khanna Sunil , Amin Mohammed
Published: February 2010

Salinity-induced changes in the protein profiles in Rhizobium sp. exhibited alterations in the expression of as many as 19 proteins, which either showed an enhanced rate of synthesis or a decline in the levels as compared with controls. All these proteins were predominantly of low molecular mass (below 40 kDa) except for one (52 kDa). Induction and repression of proteins in salt-grown cells and salt-shocked cells were qualitatively similar. However, the difference in the protein profiles was more marked in salt-grown cells as compared with salt-shocked cells.Key words: Rhizobium, SDS–PAGE, salt stress, proteins.
Changes in the surface charge of bacteria caused by heavy metals do not affect survival
Authors: Collins Y. E. , Stotzky G.
Published: February 2010

Bacillus subtilis and Agrobacterium radiobacter remained viable when exposed to Ni (1 × 10−4 M; ionic strength (μ) = 3 × 10−4) at pH values known to cause a change of the net negative charge of the cells to a net positive charge (charge reversal). The gross morphology, as determined by scanning electron microscopy, of these and other bacteria and of Saccharomyces cerevisiae was not altered in the presence of Ni, Cu, and Zn (1 × 10−4 M; μ = 3 × 10−4), which caused a charge reversal at pH values between 6.0 and 9.0. Similar results were obtained in the presence of Na and Mg, which did not cause charge reversal at the same μ and pH values. These results confirmed that cells remain viable when their surface charge is changed in the presence of some heavy metals at high pH values.Key words: heavy metals, electrokinetic properties, survival of bacteria.
Characterization and distribution of amylases during vegetative cell growth and sporulation ofClostridium perfringens
Authors: Shih Neng-Jen , Labbé Ronald G.
Published: February 2010

Clostridium perfringens produced eight extracellular and two intracellular amylolytic activities when examined by zymograms following polyacrylamide gel electrophoresis under native conditions. The major intracellular amylase was isolated from vegetative cells of C. perfringens. It possessed an estimated molecular mass of 112 kDa. Sulfhydryl and phenol functional groups were essential to its activity. The amylase was endo-acting on starch and also hydrolyzed pullulan. Polyclonal antisera against a purified extracellular amylase did not cross-react with intracellular amylase and the two amylases were biochemically different. The distribution of extracellular amylolytic activities of sporulating cells was different from that of vegetative cells, whereas the distribution of intracellular amylolytic activities remained identical. A significant increase of a particular amylase (A8) occurred in the extracellular fluid during sporulation compared with that during vegetative growth. Regulation of the excretion of amylase(s) may be sporulation and enterotoxingenicity related.Key words: Clostridium perfringens, amylase, sporulation.
Immunocytochemical localization ofBacillus thuringiensisCryl toxins in the midguts of three forest insects andBombyx mori
Authors: Yi S. , Pang A. S. D. , Frankenhuyzen K. van
Published: February 2010

Light microscopy was used to investigate the relation between toxicity, cytopathological effects, and in vivo binding of Bacillus thuringiensis CrylA(b) and CrylE toxin proteins in larvae of Lymantria dispar, Choristoneura fumiferana, Actebia fennica, and Bombyx mori. These target insects were selected for their contrasting susceptibility to the two toxins. Lymantria dispar is susceptible to CrylA(b), B. mori is susceptible to CrylE, C. fumiferana is susceptible to both, and A. fennica is not susceptible to either. In the susceptible species, both toxins caused typical pathological changes in midgut epithelial cells, including disruption and shedding of the brush border membrane, vacuolization of the cytoplasm, and swelling of the cells and their nuclei, followed by disintegration and release of cytoplasmic content into the lumen. In the highly resistant A. fennica, no cell damage was observed, but the midguts of toxin-fed larvae had a shrunken appearance. Immunohistochemical staining of midgut sections from toxin-fed larvae revealed that the toxins bound to the microvilli of the midgut epithelial cells of susceptible species only, with the exception of B. mori. In this species, the CrylA(b) toxin bound to the apical microvilli without causing cell damage or larval death. In vivo binding of toxins is thus not always correlated with larval toxicity. Accumulation of the toxins at the peritrophic membrane depended on both toxin and insect species and was not correlated with larval toxicity.Key words: Bacillus thuringiensis, Cryl toxins, forest Lepidoptera, immunocytochemical localization, cytopathology.
Inhibition ofAzotobacter salinestrïsgrowth by zinc under iron-limited conditions
Authors: Page William J. , Manchak Janet , Yohemas Michael
Published: February 2010

The growth yield of Azotobacter salinestris, a Na+-dependent, microaerophilic nitrogen-fixing bacterium, was inhibited more than 60% by 5 μM Zn2+. This organism was much more sensitive to Zn2+than the obligate aerobe Azotobacter vinelandii. Inhibition of A. salinestris was most evident in iron-limited cells and exogenously added Fe2+was more effective than Fe3+in preventing inhibition by Zn2+. While Zn2+decreased the Fe content of the cells, decreased the activity of the soluble cytoplasmic ferric reductase, and altered the intracellular Fe2+/Fe3+ratio, which in turn increased siderophore production, none of these effects appeared severe enough to account for growth inhibition. However, Zn2+also was observed to be a powerful inhibitor of Fe-limited whole cell respiration. As the cells became more Fe sufficient, this inhibition of respiration was decreased. Growth of A. salinestris also was inhibited by Cd2+ > Zn2+ > Cu2+ > Cr2+ > Ni2+ > Co2+, and inhibition by these ions also was reversed by exogenous Fe2+or Fe3+. Examination of isolated cell membranes showed that the sensitivity of A. salinestris NADH oxidase activity to Zn2+and other respiratory poisons changed as the cells became Fe sufficient, but a similar change did not occur in A. vinelandii. It is proposed that Fe-limited A. salinestris cells present a sensitive target for Zn2+inhibition, possibly a sulfhydryl group in a terminal oxidase, but this target is lost or is of decreased importance in Fe-sufficient cells.Key words: ferric reductase, iron uptake, respiratory poison, zinc, microaerophile.
Differentiation of Altemaria infectoria and Alternaria alternata based on morphology, metabolite profiles, and cultural characteristics
Authors: Andersen Birgitte , Thrane Ulf
Published: February 2010

Some small-spored species belonging to the genus Alternaria Nees have been studied according to their chemical, morphological, and cultural characteristics. A data matrix was constructed based on a combination of characters. Cluster analysis of the combined data set showed good resolution of two groups of small-spored Alternaria: the Alternaria infectoria group and the Alternaria alternata group. Isolates in the A. infectoria group produced only unique metabolites of unknown identity, whereas all isolates in the A. alternata group produced alternariol and alternariol monomethyl ether. Furthermore, the analysis showed that the A. alternata group and A. infectoria group each could be subdivided into three groups. The colour of fungal colonies on dichloran rose bengal yeast extract sucrose agar was another useful character to differentiate between the A. infectoria and A. alternata groups.Key words: Alternaria infectoria, Alternaria alternata, secondary metabolites, cluster analysis.
Effects of amphotericin B on glucose metabolism inCandida albicansblastospores evidenced by13C NMR
Authors: Rabaste Françoise , Sancelme Martine , Delort Anne-Marie
Published: February 2010

Candida albicans blastospores harvested from 8- (exponential phase) or 48-h (stationary phase) cultures were incubated with 60 × 10−3 M [1-13C]glucose with or without 10−4 M amphotericin B (AmB). The utilization of [1-13C]glucose was monitored by in vivo13C NMR under anaerobiosis. With exponential phase cells, in the presence of AmB, the consumption of glucose and the production of ethanol, trehalose, and glycerol continuously decreased with time, and after 25 min, the metabolism was blocked. On stationary phase cells AmB had almost no effect on glucose metabolism. Comparison with previous experiments evidenced that AmB induced first K+leakage, then acidification, and finally a stop of the metabolism. In parallel, in vitro13C NMR spectra were performed on supernatants and cell-free extracts of yeast suspension incubated under the same conditions. For both exponential and stationary phase cells, AmB induced an increase in the membrane permeability to glycerol; no change was observed for the other metabolites.Key words: Candida albicans,13C NMR, amphotericin B, glucose metabolism, glycerol.
Involvement of a surface-active high molecular weight factor in degradation of polycyclic aromatic hydrocarbons by Pseudomonas marginalis
Authors: Burd G. , Ward O. P.
Published: February 2010

A strain of Pseudomonas marginalis PD-14B, isolated from polycyclic aromatic hydrocarbon (PAH) contaminated soil, produced an extracellular surface-active factor of high molecular weight containing protein and lipopolysaccharide. A crude preparation of the factor, obtained from the culture broth of cells grown in mineral salts (MS) medium with succinate and yeast extract, affected the extent of PAH degradation by the bacterial cells and prevented flocculation of PAHs in an aqueous suspension. A washed suspension of P. marginalis cells also prevented flocculation of PAH suspensions and emulsified liquid hydrocarbons. Incubation of the factor and the factor-producing strain in the presence of different PAHs resulted in gradual increase of turbidity of the PAH dispersions. The factor markedly stimulated rate and extent of turbidity generation by bacterial cells. The surface-active factor may promote infection of lettuce and other plants by this known pathogen and may also have application in bioremediation.Key words: biosurfactant, polycyclic aromatic hydrocarbons, Pseudomonas marginalis, bioremediation, plant pathogenesis.
Effect of heat flushing on the concentrations of Legionella pneumophila and other heterotrophic microbes in hot water systems of apartment buildings
Authors: Zacheus Outi M. , Martikainen Pertti J.
Published: February 2010

The decontamination of Legionella pneumophila and other heterotrophic microbes by heat flushing in four legionellae-positive hot water systems was studied. Before the decontamination procedure, the concentration of legionellae varied from 3.0 × 10−3 to 3.5 × 10−5 cfu/L and the hot water temperature from 43.6 to 51.5 °C. During the contamination the temperature was raised to 60–70 °C. All taps and showers were cleaned from sediments and flushed with hot water twice a day for several minutes. The decontamination lasted for 2–4 weeks. In a few weeks the heat-flushing method reduced the concentration of legionellae below the detection limit (50 cfu/L) in the hot circulating water system just before and after the heat exchanger. The high hot water temperature also decreased the viable counts of heterotrophic bacteria, fungi, and total microbial cells determined by the epifluorescent microscopy. However, the eradication of legionellae failed in a water system where the water temperature remained below 60 °C in some parts of the system. After the decontamination, the temperature of hot water was lowered to 55 °C. Thereafter, all the studied hot water systems were recolonized by legionellae within a few months, showing that the decontamination by heat flushing was temporary. Also, the contamination of other bacteria increased in a few months to the level before decontamination.Key words: legionellae, hot water system, decontamination, water temperature, heterotrophic bacteria.
Biosynthesis of the trichothecene 3-acetyldeoxynivalenol: cell-free hydroxylations of isotrichodermin
Authors: Zamir L. O. , Devor K. A. , Nikolakakis A. , Sauriol F.
Published: February 2010

3-Acetyldeoxynivalenol is the major trichothecene produced by the fungus Fusarium culmorum. Studies in vivo with F. culmorum have established the following biosynthetic precursors of 3-acetyldeoxynivalenol: isotrichool → isotrichodiol → isotrichodermin → 15-deacetylcalonectrin, 7α-hydroxyisotrichodermin, 8α-hydroxyisotrichodermin → calonectrin → deoxynivalenol. In this paper, we describe in vitro investigations of one of these metabolic steps. The cell-free system of F. culmorum that converts isotrichodermin into 15-deacetylcalonectrin, 7α-hydroxyisotrichodermin, and 8α-hydroxyisotrichodermin is described here. This preparation requires NADPH but not NADH for activity and is not inhibited by carbon monoxide, cyanide, or known oxygenase inhibitors, such as SKF-525-A or ancymidol.Key words: trichothecene, Fusarium culmorum, cell-free system, isotrichodermin, 15-deacetylcalonectrin.
ASaccharomyces cerevisiaemutant defines a new locus essential for resistance to the antitumour drug bleomycin
Authors: Ramotar Dindial , Masson Jean-Yves
Published: February 2010

The antitumor drug bleomycin can produce a variety of lesions in the cellular DNA by a free radical dependent mechanism. To understand how these DNA lesions are repaired, bleomycin-hypersensitive mutants were isolated from the yeast Saccharomyces cerevisiae. We report here the analysis of one mutant, DRY25, that showed extreme sensitivity to bleomycin. This mutant also exhibited hypersensitivity to hydrogen peroxide and t-butyl hydroperoxide, but showed no sensitivity to other DNA-damaging agents, including γ-rays, ultraviolet light, and methyl methanesulfonate. Subsequent analysis revealed that strain DRY25 was severely deficient in the repair of bleomycin-induced DNA lesions. Under normal growth conditions, DRY25 displayed a 3-fold increase in the frequency of chromosomal translocation that was further stimulated by 5- to 15-fold when the cells were treated with either bleomycin or hydrogen peroxide, but not by methyl methanesulfonate, as compared with the wild type. Genetic analysis indicated that the mutant defect was independent of the nucleotide excision, postreplication, or recombinational DNA-repair pathways. These data suggest that one conceivable defect of DRY25 is that it lacks a protein that protects the cell against oxidative damage to DNA. A clone that fully complemented DRY25 defect was isolated and the possible roles of the complementing gene are discussed.Key words: yeast, bleomycin, DNA repair, mutations.
A novel fluorochrome for the microscopic observation of microbial morphology in wet mounts
Authors: Chan E. C. S. , Noble P. B. , Stranix B. R. , Darling G. D.
Published: February 2010

A family of novel nontoxic fluorochromes, including trans-4-(p-N,N-dimethylaminostyryl)-N-butoxycarbonylmethylpyridinium bromide and other dimethylaminostyrylpyridinium salts, has been used for the examination of microorganisms in the living state. Equipment required is similar to that for immunofluorescence, but the technique does not necessitate the utilization of specific antibodies. Procaryotic vegetative cells and endospores were readily visualized by their fluorescence with no observable quenching. Other bacteria observed included capsule-forming species, acid-fast mycobacteria, and spirochetes. In addition, the technique is also applicable to the examination of eucaryotic microorganisms. The technique as described is simple and convenient, and serves as an alternate means for the microscopic study of viable microorganisms.Key words: fluorochrome, fluorescence, microbial morphology, 4-p-dimethylaminostyrylpyridium.
The amino acids ofEscherichia colienterotoxin B subunit involved in binding to Bio-Gel A-5m or to the glycoprotein from mouse intestinal epithelial cells
Authors: Kawase Hidetsugu , Kato Michio , Imamura Seizi , Tsuji Takao , Miyama Akio
Published: February 2010

We determined whether Arg13, Met31, and Ser95 of the heat-labile enterotoxin B subunit (LT-B) might be involved in Lt-B binding to oligosaccharides, which did not bind to the B subunit of the cholera toxin (CT-B). Three LT-B mutants, R13H, M31L, and S95A were prepared by substituting three amino acid residues that differ in CT-B. These mutants formed a pentamer and exhibited the same binding ability to the GM1ganglioside as native LT-B. Although these mutants did not bind to Bio-Gel A-5m, they did bind to the glycoprotein from mouse intestinal cells in the order R13H > M31L > S95A. These data suggest that Ser95, Met31, and Arg13 are important for LT-B binding to Bio-Gel A-5m, and that although Ser95 is also partially responsible for LT-B binding to the glycoprotein, Arg13 has no significant involvement in it.Key words: heat-labile enterotoxin, cholera toxin, Bio-Gel A-5m, glycoprotein.
Numerical analysis of fatty acid patterns of coryneform bacteria and related taxa
Authors: Kämpfer Peter , Kroppenstedt Reiner M.
Published: February 2010

A numerical study of the fatty acid patterns of 263 reference strains belonging to the genera Arthrobacter, Aureobacterium, Brevibacterium, Cellulomonas, Clavibacter, Corynebacterium, Curtobacterium, Erysipelothrix, Microbacterium, and Rhodococcus was undertaken based on cultural and chemical standardized techniques. Clustering was by the unweighted pair group method using the correlation coefficient. Two cluster groups could be defined at the 62% level, one containing strains characterized by saturated and monounsaturated fatty acids and the second group characterized by iso- and anteiso-branched fatty acids. Within the first cluster group, a clear separation of strains assigned to the genera Rhodococcus, Erysipelothrix, and Corynebacterium could be achieved. Furthermore, strains of the species Corynebacterium glutamicum, Corynebacterium ammoniagenes, Corynebacterium diphtheriae, 'Corynebacterium ulcerans,' and Erysipelothrix rhusiopathiae could be found in distinct clusters, based on quantitative differences in fatty acid patterns. Within the second cluster group, a high degree of similarity between the genera Aureobacterium, Cellulomonas, Clavibacter, Curtobacterium, and Microbacterium found in phylogenetically based studies could be shown also by fatty acid patterns. Several strains of the plant pathogenic coryneform bacteria assigned to the genus Clavibacter and Curtobacterium flaccumfaciens were found within one cluster, indicating a high similarity between these genera. Strains of the genus Arthrobacter were grouped into three adjacent clusters and could not be differentiated by fatty acid patterns. The results of the study are essentially in line with a previously published numerical survey and with other chemotaxonomic and genetic data. Thus, quantitative fatty acid patterns are recommended for identification of several coryneform bacterial genera. In some cases an identification at the species level is possible.Key words: fatty acid analysis, coryneform bacteria, differentiation, numerical analysis.
Iron acquisition by oral hemolytic spirochetes: isolation of a hemin-binding protein and identification of iron reductase activity
Authors: Scott D. , Siboo R. , Chan E. C. S.
Published: February 2010

Oral anaerobic spirochetes (OAS) have been implicated in the etiology of periodontal disease. To adapt to the environment of the subgingiva, OAS must be able to acquire iron from limited sources. OAS have previously been shown not to produce siderophores but are β-hemolytic and can bind hemin via a proteinaceous 47-kDa outer membrane sheath (OMS) receptor. Present studies show that [3H]hemin is not transported into the cytoplasm, that hemin and ferric ammonium citrate, as the sole iron sources, can support the growth of OAS and that protoporphyrin IX and Congo red are inhibitory, thereby implying an important in vivo role for hemin as an iron source. Treponema denticola ATCC 35405 produces an iron reductase. The iron reductase can reduce the central ferric iron moiety of hemin. The 47-kDa OMS hemin-binding protein has been purified to apparent homogeneity by methanol–chloroform extraction of cellular lipoproteins and the use of a hemin–agarose bead affinity column. A model of iron acquisition by OAS is presented.Key words: Treponema denticola, hemin-binding protein, iron limitation, iron reductase.
Distinctive control of metabolic pathways byChlorella autotrophicain semicontinuous culture
Authors: Fábregas Jaime , Patiño Manuel , Morales Ever D. , Dominguez Adolfo , Otero Ana
Published: February 2010

The marine microalga Chlorella autotrophica was cultured semicontinuously under light–dark synchronizing conditions at two nutrient concentrations (2 and 4 mmol N∙L−1) and five rates of daily renewal (from 10 to 50% of culture volume). Under such conditions, the biochemical composition of C. autotrophica was strongly influenced by the renewal rate, but unlike other marine microalgae, the nutrient concentration had no effect on the biochemical composition of the organic fraction of the microalga at a given growth rate. Results suggest that this species exerts a strong control over metabolic pathways, independent of the nutrient concentration in the medium.Key words: Chlorella autotrophica, semicontinuous culture, biochemical composition.
Ochratoxin A: an antiinsectan metabolite from the sclerotia of Aspergillus carbonarius NRRL 369
Authors: Wicklow D. T. , Dowd P. F. , Alfatafta A. A. , Gloer J. B.
Published: February 2010

Ochratoxin A, a known mycotoxin with demonstrated toxicity to insects, has been isolated from the sclerotia of the fungus Aspergillus carbonarius NRRL 369. The sclerotia, harvested from a solid substrate fermentation of corn kernels at 28 °C, produced quantities of ochratoxin A exceeding 50 ppm/g dry weight of sclerotia. Evidence is presented that ochratoxin A accounts for the activity of the methanol extract against larvae of the detritivorous beetle Carpophilus hemipterus (Nitidulidae) (75% reduction in feeding rate) and corn ear worm Helicoverpa zea (50% mortality with 99% reduction in weight gain among surviving larvae) when incorporated into a pinto bean diet at levels less than those occurring naturally in the sclerotia.Key words: ochratoxin A, Aspergillus carbonarius, sclerotia, Helicoverpa zea, Carpophilus hemipterus, antiinsectan, chemical defense.
Cytochemistry of defense responses in cassava infected by Xanthomonas campestris pv. manihotis
Authors: Kpémoua K. , Boher B. , Nicole M. , Calatayud P. , Geiger J. P.
Published: February 2010

Stems of susceptible and resistant cassava plants have been cytologically investigated for their defense reactions to an aggressive strain of Xanthomonas campestris pv. manihotis. Histochemistry, in conjunction with gold cytochemistry, revealed that in susceptible and resistant plants, phloem and xylem parenchyma cells displayed a wide range of responses that limited the bacterial growth within the infected plants. Lignification and suberization associated with callose deposition were effective mechanisms that reinforced host barriers in the phloem. In the infected xylem, vessels were plugged by a material of pectic and (or) lignin-like origin. Flavonoids have been seen to be incorporated in secondary cell wall coatings. These reactions occurred at a higher intensity in the resistant plants. The number of phoem and xylem cells producing autofluorescent compounds was higher in infected resistant plants than in susceptible plants. Reactions have been observed in the resistant variety only, such as secretion of phenol-like molecules by tyloses and hyperplasic activity of phloem cells that compartmentalized bacterial lysis pockets, which are potent secondary inoculum sources.Key words: lignin, suberin, callose, phenol, tylose, flavonoid, pectin.
Immunological detection and localization of the cotton endophyte Enterobacter asburiae JM22 in different plant species
Authors: Quadt-Hallmann A. , Kloepper J. W.
Published: February 2010

Immunological methods were used to study the colonization of internal tissues of different plant species by the endophytic bacterium Enterobacter asburiae JM22. Polyclonal and monoclonal antibodies applied in enzyme-linked immunosorbent assay (ELISA), dot blot assay, tissue printing, or immunogold labeling were sensitive and specific enough to detect JM22 in plant tissues. Detection limits were 1.0 × 103 colony-forming units (CFUs)/mL for tissue printing, 1.0 × 104 CFUs/mL for ELISA and 1.0 × 105 CFUs/mL for dot blot assay. Polyclonal and monoclonal antibodies showed a positive immunological reaction with nearly all tested Enterobacter spp. In contrast with polyclonal antibodies, the monoclonal antibodies differentiated Enterobacter spp. and closely related genera like Pantoea or Serratia. Other bacterial genera, plant sap from nontreated field-grown crops, and soil solutions did not react with the antisera. When applied as a seed treatment, JM22 colonized roots, stems, and cotyledons of bean, cucumber, and cotton plants. Fourteen days after inoculation of cotton cotyledons or leaves, JM22 was detected inside the inoculated plant tissue and the bacteria moved to the roots. JM22 reached concentrations up to 1.0 × 105 CFUs/g in roots, 1.0 × 104 CFUs/g in stems, and 1.0 × 103 CFUs/g in cotyledons or leaves. Population densities of JM22 varied between the different plant species, being highest in bean and lowest in cotton. JM22 was detected with ELISA in different plant growth media. While sand, ground clay, and loamy sand showed high and comparable ELISA readings, the extinctions of sandy loam and Promix were significantly lower than the ones of the other three growth media, indicating a strong influence of soil mixes on immunological reactions. JM22 showed an intensive gold label in drop preparations of bacterial suspensions in phosphate buffer, plant sap, and ultrathin sections of plant tissue. After seed treatment, the bacteria were located on the root surface, concentrated in grooves between epidermal cells, below collapsed epidermal cells, within epidermal cells, and inside intercellular spaces in the root cortex close to conducting elements. Inoculation of leaves or cotyledons resulted in the occurrence of many gold labeled cells of JM22 on the petiole surfaces. Enterobacter asburiae colonizes different plant species and establishes endophytic populations in various tissues.Key words: immunology, endophytic bacteria, colonization, localization, plant species.
Studies on keratinophilic fungi. X. Arthrographis alba sp.nov.
Authors: Gené Josepa , Guarro Josep , Guillamón José Manuel , Ulfig Krzysztof
Published: February 2010

In our studies on keratinophilic fungi in Spain, an arthroconidial anamorphic species has been recovered and is herein described as new. Arthrographis alba sp.nov. is characterized by having arthroconidia borne from laterally or pseudodichotomously branched conidiophores, white colonies, and nil or restricted growth at 37 °C. Analysis of restriction fragment length polymorphisms of ribosomal DNA reveals differences with Arthrographis kalrae, a morphologically similar species.Key words: Arthrographis alba, Hyphomycetes, rDNA.
Induction of superoxide dismutase synthesis inHumicola lutea110 by pentachlorophenol
Authors: Angelova Maria B. , Genova Lubka K. , Pashova Svetlana B. , Slokoska Ludmila S.
Published: February 2010

Pentachlorophenol (PCP) caused a rapid and pronounced increase in the rate of biosynthesis of the superoxide dismutase (SOD) in fungal strain Humicola lutea 110. Mn-containing SOD (Mn-SOD) was mainly responsible for modulating total cell SOD. The kinetics of SOD synthesis in the presence of PCP demonstrated the induction model of enzyme formation. This model was also supported by deinduction experiments, because the removal of the PCP was followed by a marked decrease in SOD activity. PCP also caused a moderate induction of catalase. The concentrations, which were effective in inducing the Mn-SOD, increased the cyanide-resistant respiration. It seems likely that PCP increased the rate of intracellular production of superoxide [Formula: see text]. Addition of inhibitors of transcription and translation to cultures in the presence of inducer (PCP) inhibited further accumulation of SOD activity. These data suggest that PCP, probably by the increase of [Formula: see text] content, accelerates new enzyme synthesis in fungal strain Humicola lutea 110.Key words: superoxide dismutase, superoxide, induction, pentachlorophenol, fungi, Humicola lutea.
Detection and identification ofEntamoeba gingivalisby specific amplification of rRNA gene
Authors: Kikuta Noriko , Yamamoto Ayako , Goto Nobuichi
Published: February 2010

A pair of oligonucleotide primers were designed from the nucleotide sequence of the gene encoding the small subunit ribosomal RNA (SrRNA) of the oral protozoan parasite Entamoeba gingivalis. The primers amplified a 1.4-kb DNA fragment by polymerase chain reaction and were specific for Entamoeba gingivalis but not for other protozoa, oral protists and bacteria, or human leukocytes. With this method, the DNA from as few as 30 cells of Entamoeba gingivalis could be detected. These results suggest that this approach is applicable to the detection and identification of Entamoeba gingivalis in the human oral cavity.Key words: Entamoeba gingivalis, small subunit rRNA, polymerase chain reaction, diagnostics.
Nucleotide sequence, insertional mutagenesis, and transcriptional mapping of a conserved region of the baculovirusAutographa californicanuclear polyhedrosis virus (map unit 64.8–66.9)
Authors: Lu Albert , Craig Andrew , Casselman Richard , Carstens Eric B.
Published: February 2010

The nucleotide sequence of a 2773-bp region of the Autographa californica nuclear polyhedrosis virus HR3 variant (AcMNPV) (map unit 64.4–68.2) has been determined. This region lies between the previously analyzedp6.9 and p80 genes. Three open reading frames were contained within this region, potentially coding for proteins of 45, 40, and 12 kDa. The 5′ ends of transcripts capable of coding for the 45- and 12-kDa proteins map to consensus baculovirus late transcription start sites (ATAAG), while the major 5′ end of the transcript coding for the 40-kDa protein maps 16 nucleotides downstream from another late transcription start site sequence, GTAAG. Attempts to prepare recombinant viruses containing insertions within these three genes were negative, suggesting that they are all essential for virus replication in cell culture. The size and organization of transcripts expressed from this region of AcMNPV were very similar to those of the previously described homologous region of Orgyia pseudotsugata nuclear polyhedrosis virus (OpMNPV). The three AcMNPV protein sequences (p45, p40, and p12) showed amino acid sequence homology with the proteins p48, p45, and p12 of OpMNPV, suggesting this region is highly conserved in baculoviruses.Key words: baculovirus, Autographa californica nuclear polyhedrosis virus, nucleotide sequence, transcript mapping, essential genes.
A 4-year study of the diversity and persistence of coliforms and Aeromonas in the water of a Swedish drinking water well
Authors: Kühn I. , Huys G. , Coopman R. , Kersters K. , Janssen P.
Published: February 2010

Coliforms and Aeromonas, isolated over a sampling period of 4 years from a Swedish drinking water well, were analysed for their phenotypical diversity and for their ability to persist in the well water. From each of the 40 water samples collected from the well, 32 bacterial isolates were subjected to typing by the PhenePlate (PhP) biochemical fingerprinting system. Strains able to persist in the well water were further characterized using the API 20E system, gas–liquid chromatographic cellular fatty acid analysis, and the DNA fingerprinting technique AFLP. Using the PhP system, a total of 170 different phenotypes were identified among 1143 studied isolates. Most phenotypes were only represented by a few isolates and (or) were restricted to one or two sampling occasions. However, one particular phenotype (RV-C01), identified as Aeromonas hydrophila using the API 20E system and fatty acid analysis, reoccurred in 28 samples distributed over the whole study period and often dominated the bacterial population in the well water. AFLP analysis revealed that the RV-C01 isolates displayed basically identical fingerprints. Our results thus suggest that a genetically stable Aeromonas clone resided in the well water over the whole 4-year study, whereas other bacterial strains studied were only transient inhabitants of the well.Key words: Aeromonas, coliform, water, diversity.
Bacterial degradation of emulsified crude oil and the effect of various surfactants
Authors: Bruheim Per , Bredholt Harald , Eimhjellen Kjell
Published: February 2010

A Rhodococcus sp. 094 bacterium was tested for its ability to oxidize alkanes in crude oil emulsified by nonionic chemical and biological surfactants. Oxidation rates were measured in a 3-h period by Warburg respirometry.14CO2recovery was measured from the [1-14C]hexadecane spiked crude oil. Response to emulsified oil depended on the physiological state of the bacteria (i.e., cells harvested in the exponential and stationary growth phases) were tested. Oxidation rates by cells in the exponential growth phase were negatively affected by surfactant amendment. Oxidation rates by cells in the stationary growth phase were in some cases stimulated by surfactants. The stimulatory effect depended on both the chemical structure and the physicochemical properties (i.e., hydrophilic–lipophilic balance (HLB)) of the surfactants. Surfactants with intermediate HLB values (8–12) gave the best results. Neither the biosurfactants nor the commercial oil-spill dispersants tested had any significant stimulatory effect.Key words: biodegradation, bacteria, surfactants, crude oil, Warburg.
Estimation of spore hydrophobicity for members of the genera Beauveria, Metarhizium, and Tolypocladium by salt-mediated aggregation and sedimentation
Authors: Jeffs Lloyd B. , Khachatourians George G.
Published: February 2010

The surface hydrophobicities of fungal spores from the entomopathogenic genera Beauveria, Metarhizium, and Tolypocladium were quantitatively measured and compared using a novel assay employing salt-mediated aggregation and sedimentation (SAS). Spores with greater hydrophobicities were easily identified by their aggregation and sedimentation out of suspension at faster rates under lower salt concentrations. Of the three ammonium salts investigated for their salting-out potentials, ammonium sulfate gave the most pronounced effect, closely followed by ammonium chloride, and then ammonium acetate. Using the SAS assay, spores exhibited more pronounced hydrophobic properties at pH 5.8 than at higher pH values of 6.8 and 7.8. The effects of temperature and spore concentration upon the SAS assay were also investigated, with greater spore sedimentation occurring at elevated temperature. By plotting SAS values for two ammonium salt concentrations (0.01 and 0.1 M) in a coordinate system, it was possible to differentiate the hydrophobicities of all five spore isolates, clearly demonstrating the superiority of SAS over an existing phase-exclusion assay. The significance and potential of the SAS assay are also discussed.Key words: fungal spores, hydrophobicity, microassay, SAS, salting out, microbial insecticides.
Analysis of population structure of cactophilic yeast from the genusPichia:P.cactophilaandP.norvegensis
Authors: Ganter Philip F. , Quarles Bryan
Published: February 2010

DNAs from 40 strains of Pichia cactophila and Pichia norvegensis, yeasts characteristic of cactus necroses, were compared using randomly amplified polymorphic DNA (RAPD) banding patterns and killer/sensitive phenotypes. Both species belong to the same species complex within the genus. The levels of between-strain RAPD variation were high in both species (higher in the automictic P. cactophila than in the heterothallic P. norvegensis), although there is little variation in physiological abilities within either species. Although each species was a separate lineage, RAPD analysis confirms that the species are related. Within each species, RAPD variation was related to the geographic origin of the strains. Pichia cactophila strains from southern Florida were more related to those from Antigua than to those from northern Florida. These results correlated well with the differences among killer/sensitive phenotypes of strains. Principal component analysis indicated that the phenotypes of each species differ. Here too, strains from southern Florida were more similar to those from Antigua than to those from northern Florida. Previous work had identified differences in the cactophilic yeast communities from southern and northern Florida, and these results indicate that the differences are detectable at the population level as well.Key words: RAPD phylogeny, Pichia, killer factor.
Membrane fatty acid composition and membrane fluidity as parameters of stress tolerance in yeast
Authors: Swan Tracey M. , Watson Kenneth
Published: February 2010

The relationship among membrane fatty acid composition, membrane fluidity, and stress tolerance was investigated in yeast cells. Several strains were examined for their ability to survive heat, ethanol, and hydrogen peroxide stresses. Membrane fluidity was determined by measuring fluorescence anisotropy using diphenylhexatriene as a probe. There was no obvious relationship among membrane fatty acyl composition, membrane fluidity, and stress tolerance in the strains examined. A consistent trend in the present study was an observed decrease in membrane fluidity following thermal treatment, which coincided with a reduction in cell viability. We suggest that protein denaturation may be responsible for the observed effect of elevated temperature on membrane fluidity and viability. This was implied by observations on the irreversible nature of thermal transitions, as measured by breaks in Arrhenius plots, in which stationary phase cells were shown to exhibit higher transition temperatures (53.9–55.5 °C) than exponential phase cells (49.5–51 °C). Furthermore, the thermal transition temperature was shown to increase in exponential phase cells following heat shock, which was associated with an increase in thermotolerance. We suggest that the thermotolerant state of heat-shocked cells and cells entering stationary phase may be associated with increased protein stability. However, despite the relatively good correlation between thermal transition temperature and stress tolerance, the thermal transition temperature did not predict the stress tolerance of a given strain, as stress-sensitive strains had similar transition temperatures to those of stress-resistant strains.Key words: membrane fluidity, stress tolerance, yeast, membrane lipids.
Biodegradation of N-phosphonomethyliminodiacetic acid by microorganisms from industrial activated sludge
Authors: Carson David B. , Hallas Laurence E. , Heitkamp Michael A.
Published: February 2010

A microbial population that biodegraded N-phosphonomethyliminodiacetic acid (PIA), a key component of glyphosate (N-phosphonomethylglycine) process waste, was established. The stoichiometric conversion of PIA to aminomethylphosphonic acid (AMPA) was observed in a laboratory sequencing batch reactor (SBR) containing activated sludge from a glyphosate-manufacturing facility and PIA as sole source of carbon. PIA degradation was determined by high-performance liquid chromatography and confirmed by radiolabeled studies. Greater than 90% of the [carboxymethyl-2-14C]-label of PIA was released as 14CO2 in 7 days using samples of sludge from the SBR. The cycle time required to biodegrade up to 7.5 mM PIA in SBRs was reduced from 21 to < 3 days. PIA biodegradation was also established in an immobilized bacteria column inoculated with mixed liquor from a SBR; > 99% PIA removal was achieved at an influent concentration of 2.2 mM and a hydraulic retention time of < 10 h. A pure bacterial culture was isolated from a SBR by streaking samples of sludge on solid media with PIA as sole carbon source. The isolate was identified as Xanthomonas maltophilia. In liquid culture, X. maltophilia degraded up to 4.4 mM PIA within 10 days and produced stoichiometric amounts of AMPA. The results demonstrate the biodegradation of PIA and suggest the potential for its treatment in industrial biological treatment systems.Key words: degradation, activated sludge, glyphosate.
Isolation and cultivation of spore-forming filamentous bacteria fromPorcellio scaber
Authors: Jorgensen Jeremy , Dolan Sona , Haselton Aaron , Kolchinsky Rita
Published: February 2010

An endospore-forming rod-shaped filamentous bacterium was taken from boiled intestines of common sow bugs (Porcellio scaber, isopod crustaceans). The bacteria were grown on peptone – yeast extract medium. As many as 180 cells per filament were counted in culture; filament length was a function of time after germination and oxic conditions. Cultures continued to grow filamentously after 10 successive transfers. The development of spores was inhibited by strict anaerobiosis for 3 months. Spore-forming filaments over 100 μm long in fresh intestinal material were observed only in guts taken from sow bugs cultivated in darkness. Phenotypic tests presented here show this isolate to be a member of the genus Bacillus, most closely resembling B. cereus.Key words: Arthromitus, motile bacilli, isopod, sow bug, intestinal filaments.