bluuebunny/crossref_metadata_2025 huggingface dataset:
Flocculation of Saccharomyces cerevisiae: inhibition by sugars
Authors: Masy C. L. , Henquinet A. , Mestdagh M. M.
Published: May 2010

Flocculation is governed by the competition between electrostatic repulsion (nonspecific interactions) and polysaccharide–protein bonds (specific interactions). In our study, the inhibition of flocculation by sugars for 12 strains of Saccharomyces cerevisiae leads us to extend the classification described in the literature and to define three groups of yeasts: flocculation mannose sensitive (MS), flocculation glucose–mannose sensitive (GMS), and flocculation mannose insensitive (MI). Only the first two groups showed specific interactions between proteins and mannans. In the MI group, the sugars tested did not inhibit flocculation. To characterize the particularities of the stereochemistry of the cell-wall proteic receptors of strains belonging to the MS and GMS groups, 31 sugars were used as inhibitor probes on two representative strains. The results show that the lectin specificity of strains belonging to the GMS group is less restricted regarding C-1 and C-2 hydroxyl groups than the lectin from strains belonging to the MS group, which interacts with all of the hydroxyl groups of mannopyranose. The two groups also differ with respect to inhibition by sugars: strains belonging to the MS group are partially inhibited whereas strains of the GMS group are completely inhibited. We observed that the presence of ethanol increases sugar fixation by strains from the MS group, but not from the GMS group. Moreover, both receptors interact with disaccharides, provided the two monomers are linked by an α(1 → 4), α(1 → 3), or α(1 → 2) bond. Key words: yeast flocculation, proteic receptors, sugars, lectins.
Corrosion products associated with attached bacteria at an oil field water injection plant
Authors: Ferris F. G. , Jack T. R. , Bramhill B. J.
Published: May 2010

Attached populations of corrosion enhancing sulfate-reducing bacteria (SRB) and organic acid-producing bacteria (APB) were measured on steel plugs at an oil field water injection plant near Wainwright, Alberta. The sample plugs were colonized to ca. 106 SRB/cm2. Counts for APB ranged from 102 to 10/cm2. Scanning electron microscopic examination of the sample plugs revealed an uneven distribution of surface corrosion deposits. A thin iron sulfide layer covered most of the exposed areas. Thicker sulfur-enriched deposits occurred randomly. The bulk of the thicker deposits were smooth, whereas peripheral regions exhibited a porous texture. The elemental composition of the different regions was the same; however, bacterial cells were concentrated in the porous areas and were not found in the thinner deposits. In transmission electron microscopic thin sections cut perpendicularly through corrosion deposits, bacterial cells were found mineralized in successive stages by iron sulfides. The corrosion deposit matrix also generated strong Cl peaks in energy dispersive X-ray spectra. This entrainment of bacterial cells within a corrosion deposit matrix is consistent with the concept of bacterial enhancement of corrosion by removal of reducing power from iron sulfides galvanically coupled to the steel surface. Key words: microbial corrosion, iron sulfide, cathodic hydrogen, electron microscopy.
Regulation of extracellular N-acetyl-D-glucosaminidase production in the entomopathogenic fungus Beauveria bassiana
Authors: Bidochka Michael J. , Khachatourians George G.
Published: May 2010

The entomopathogenic fungus Beauveria bassiana produces two extracellular N-acetylglucosaminidases (NAGase) in liquid medium containing colloidal chitin as the sole source of carbon and nitrogen. To study the regulation of NAGase synthesis, N-acetyl-D-glucosamine (GlcNAc), glucose NH4NO3, or amino acids were added to the colloidal chitin medium and NAGase activity was measured. NAGase synthesis was (i) induced with GlcNAc, and no repression was observed with GlcNAc provided at 2% (w/v); (ii) repressed in the presence of glucose plus NH4NO3; (iii) partially repressed when glucose or NH4NO3 was provided; and (iv) repressed to levels that were < 40% of the control levels when glutamic acid, tyrosine, arginine, proline, valine, and histidine were provided to the colloidal chitin medium. Total NAGase activity levels were > 60% of the control activity when alanine, glycine, isoleucine, aspartic acid, and leucine were tested. It appears that synthesis of NAGase is sensitive to cell energy and the carbon and nitrogen requirements.Key words: Beauveria bassiana, N-acetyl-D-glucosaminidase, entomopathogenic fungus, extracellular enzyme, regulation.
Characterization of bacteria isolated from a bleached kraft pulp mill wastewater treatment system
Authors: Fulthorpe Roberta R. , Liss Steven N. , Allen D. Grant
Published: May 2010

Water samples from the wastewater treatment system of a bleach kraft mill and from the river that supplies the mill were plated on six different media and culturable isolates were screened for substrate utilization patterns, taxonomic characters, plasmid content, and resistance to ampicillin, streptomycin, kanamycin, tetracycline, naldixic acid, mercury, nickel, copper, cobalt, cadmium, and zinc. A cluster analysis of the substrate utilization profiles and taxonomic characters revealed that Pseudomonas, Acinetobacter, and Acidovorax spp. were common among the culturable isolates from the river, while Ancylobacter aquaticus, Klebsiella spp., and an unknown group of pleomorphic Gram-negative methylotrophs were common among the culturable isolates from the mill treatment system. Of isolates from the settling pond and aerated lagoon, 78 and 64% carried plasmids, while only 56% of isolates from the river carried plasmids. Plasmids were significantly associated with resistance to cadmium but not with any other resistance characters. Large numbers of plasmid-carrying A. aquaticus strains and pleomorphic methylotrophs accounted for high plasmid incidence levels in the mill treatment system, and the ability to dechlorinate simple aliphatic substrates was found in these two groups as well as in one Pseudomonas strain.Key words: pulp and paper, wastewater treatment, chlorinated organics, culturable heterotrophs, methylotrophs, plasmids.
The mitochondrial genome of the entomopathogenic fungus Beauveria bassiana: analysis of the ribosomal RNA region
Authors: Pfeifer Tom A. , Hegedus Dwayne D. , Khachatourians George G.
Published: May 2010

The 28.5-kbp mitochondrial (mt) genome from the entomopathogenic fungus Beauveria bassiana was studied using restriction enzyme analysis, gene probe hybridization, and DNA sequence comparisons. A detailed restriction enzyme map allowed cloning of the entire genome into a number of segments. Hybridization of heterologous gene probes to the mtDNA resulted in the identification of the large ribosomal RNA (lrRNA) and small ribosomal RNA (srRNA) genes. Gene probes derived from several yeasts and fungi failed to identify any additional genes. However, partial DNA sequence analysis revealed the lrRNA and srRNA genes as well as four protein-encoding genes: the NADH dehydrogenase subunit 1 (NAD1), NADH dehydrogenase subunit 6 (NAD6), cytochrome oxidase subunit 3 (C03), and ATPase subunit 6 (ATP6) genes. The ATPase subunit 9 (ATP9) gene was not identified by hybridization to mtDNA, but could be detected by hybridization to total cellular DNA. The portions of the genes sequenced were homologous to the equivalent genes from yeast and other filamentous fungi, most notably Aspergillus nidulans. No introns were identified in these regions. The organization of the sequenced region of the B. bassiana mt genome more closely resembled that of A. nidulans than that of Podospora anserina or Neurospora crassa.Key words: Beauveria bassiana, mtDNA, gene mapping, mitochondrial rRNA, mitochondrial organization.
Partial purification and characterization of two extracellular N-acetyl-D-glucosaminidases produced by the entomopathogenic fungus Beauveria bassiana
Authors: Bidochka Michael J. , Tong Kit I. , Khachatourians George G.
Published: May 2010

Beauveria bassiana grown in a liquid medium containing N-acetyl-D-glucosamine and colloidal chitin produced two distinct N-acetyl-D-glucosaminidases, NAGase 1 and NAGase 2. NAGase 1 had a molecular weight of 97 000 and NAGase 2 was comprised of two subunits, of molecular weights 64 000 and 66 000. The optimal temperature and pH for NAGase 1 were 57 °C and pH 5 and for NAGase 2 they were 37 °C and pH 5. NAGase 1 was more thermostable than NAGase 2. The isoelectric points of NAGase 1 and 2 were ca. pH 9.5 and 5.5, respectively. NAGase 1 and 2 were unaffected by a 10 mM concentration of chloride salts of the ions Ca2+, Mg2+, or Zn2+, by 10 mM EDTA, and by 0.25–1 mM of short chain fatty acids. Dithiothreitol caused some inactivation of NAGase 2 while stimulating activity of NAGase 1. NAGase 1 had a Km of 0.38 mM and a Kcat/Km of 3923.88 M−1∙s−1. NAGase 2 had a Km of 2.095 mM and a Kcat/Km of 411.88 M−1∙s−1 when p-nitrophenyl-β-N-acetylglucosaminide was used as the substrate.Key words: Beauveria bassiana, N-acetyl-D-glucosaminidase, entomopathogenic fungus, extracellular enzyme.
IS1071-mediated recombinational equilibrium in Alcaligenes sp. BR60 carrying the 3-chlorobenzoate catabolic transposon Tn5271
Authors: Ng James , Wyndham R. Campbell
Published: May 2010

In experiments designed to Tn5 mutagenize the indigenous plasmid pBRC60 of Alcaligenes sp. BR60, kanamycin-resistant mutants were isolated that were cured of this plasmid and that exhibited recombination of the plasmid-located chlorobenzoate catabolic transposon Tn5271 into the chromosome. These events were independent of the location of Tn5 insertions into the genome of strain BR60. The chromosomal recombinants carried at least two novel copies of IS1071, the class II insertion sequence flanking Tn5271, compared with the parent strain. Recombination of Tn5271 into the chromosome of Alcaligenes sp. BR60 was also detected following mating in of pBRC60-incompatible (IncP1) plasmids, R68 and pGS65. Chromosomal copies of Tn5271 could be mobilized between Alcaligenes strains via plasmids pBRC40 or R68. Conjugation of the incompatible plasmid pGS65 into Alcaligenes strains in the absence of selection for 3-chlorobenzoate catabolism resulted in the recovery of 85% of transconjugants in which the entire pBRC60 plasmid had integrated into the chromosome. These transconjugants exhibited complex rearrangements in chromosomal IS1071 copies. A model of recombinational equilibrium involving homologous recombination between plasmid and chromosomal copies of IS1071 is presented. The results are discussed in terms of the IS1071 (class II) transposition mechanism and the observed products of IS 1071-mediated recombination in natural recipients of pBRC60 in aquatic environments.Key words: transposon, 3-chlorobenzoate catabolism, rearrangement.
Effects of light- and altered-cercosporin phenotypes on gene expression in Cercospora kikuchii
Authors: Rollins J. A. , Ehrenshaft M. , Upchurch R. G.
Published: May 2010

Cercospora kikuchii is a fungal pathogen of soybean that produces a photosensitizing and phytotoxic polyketide, cercosporin, in culture and in planta. We have studied the influence of growth stage, light, and growth medium on cercosporin accumulation in a wild-type isolate and three mutant strains with altered toxin phenotypes. After an initial logarithmic growth phase, the wild-type isolate accumulated high levels of cercosporin on either complete medium or potato dextrose broth, but only when cultured in the light. Dark-grown cultures of the wild-type and light-grown cultures of two uv-induced mutant derivatives accumulated 100-fold lower cercosporin levels. A third mutant strain accumulated wild-type cercosporin levels, but only when cultured in the light in potato dextrose broth. Two-dimensional gel electrophoresis of both extracted proteins and in vitro translation products from wild-type cultures revealed the presence of polypeptides and poly A + RNAs whose accumulation was positively regulated by light. Comparison of translated polypeptide patterns from wild-type and mutant cultures also demonstrated differential accumulation of translatable poly A + RNAs in cercosporin-producing and nonproducing cultures.Key words: nonspecific toxin, photo induction, in vitro translation.
Mannosyl transfer in Cryptococcus neoformans
Authors: White Catherine W. , Jacobson Eric S.
Published: May 2010

A particulate enzyme preparation from Cryptococcus neoformans transferred the mannosyl residue from GDP-mannose:o an acceptor consisting of a commercial preparation of methyl 3-O-α-mannopyranosyl-α-mannopyranoside (confining 10% 2-O-α-mannopyranosyl-α-mannopyranoside). The configuration of the new bond was alpha by its susceptibility to α-mannosidase; the amount of product was dependent on the concentration of enzyme, of GDP-mannose, and of acceptor. The optimal temperature and pH were 37 °C and 7.0, respectively. Manganous ion was required for activity and acetyl coenzyme A was stimulatory. Studies suggested that dolichyl phosphate intermediates were not involved in this mannose transfer. The fact that none of the several acapsular mutants tested were deficient in this mannosyltransferase suggested that this enzyme was not involved in synthesis of backbone mannan linkages in capsular polysaccharide. NMR analysis of the methylmannotriose product showed only α(1 → 2) linkages between sugar moieties. This mannosyltransferase evidently extends α(1 → 2) mannan by adding another α(1 → 2)-linked mannosyl residue. Its activity is appropriate for a role in synthesis of "high mannose" oligosaccharide moieties of glycoproteins.Key words: virulence, capsular polysaccharide, acapsular mutants, dolichol pathway, oligomannans.
Indoleacetic acid production by the rhizosphere bacterium Azospirillum brasilense Cd under in vitro conditions
Authors: Omay S. H. , Schmidt W. A. , Martin P. , Bangerth F.
Published: May 2010

Factors influencing indoleacetic acid release from Azospirillum brasilense Cd (ATCC 29729) were investigated under batch culture conditions. In the presence of ammonium in the liquid culture solution, indoleacetic acid release from bacterial cells was considerably higher than in the corresponding N-free medium that was slightly solidified with agar to provide conditions for N2 fixation. In the solution culture, the concentration of indoleacetic acid was low during the logarithmic growth phase and increased rapidly with the beginning of the stationary phase. A similar time course was found for the indoleacetic acid content (dry weight basis) of the bacterial cells. Addition of tryptophan strongly stimulated the release of indoleacetic acid, which again showed a steep rise in the early stationary phase. The pH of the nutrient solution increased from 6.8 to 9.3 during incubation but this was not responsible for the steep rise in indoleacetic acid levels. The sole carbon source in the substrate (DL-malic acid) was identified as the limiting growth factor. This suggests that the high increase in indoleacetic acid production in the stationary phase is the expression of an overall change in cell metabolism when the carbon source is exhausted. At this developmental stage the high production of indoleacetic acid seems to have the character of a secondary product. Press sap from wheat roots did not promote indoleacetic acid production by bacterial cells.Key words: Azospirillum, indoleacetic acid, tryptophan, pH solution.
Purification and properties of mercuric reductase from Yersinia enterocolitica 138A14
Authors: Blaghen Mohamed , Vidon Dominique J. M. , Kebbaj Mohamed Said El
Published: May 2010

A mercuric ion-reducing flavoprotein was purified from Yersinia enterocolitica 138A14 using dye matrix affinity chromatography. The purified enzyme had a characteristic absorption spectrum similar to those of flavin compounds, and FAD was detected as a part of the purified enzyme by thin-layer chromatography. Freshly purified preparations of the enzyme showed a single band on SDS polyacrylamide gel electrophoresis with a molecular weight of 70 000. The isolated enzyme had a molecular weight of about 200 000 as determined by gel filtration and disc gel electrophoresis. These results suggest an apparently trimeric structure of the enzyme. Dithiothreitol treatment disrupted the trimer into a dimeric structure of 140 000. Along with ageing, as well as limited proteolytic digestion, the enzyme evolved to give a dimeric molecule of 105 000 composed of two identical subunits of 52 000. The combination of the purified enzyme with HgCl2, or unexpectedly with merthiolate, oxidised the NADPH, which was followed spectrophotometrically. The Km for HgCl2 was dependent on the concentration of exogenous thiol compounds. A comparison of physical properties as well as kinetic characteristics indicated that the enzyme from Y. enterocolitica 138A14 is similar to mercuric reductases isolated from other mercury-resistant bacteria.Key words: Yersinia enterocolitica, mercury resistance, mercuric reductase.
Insertion sequences on plasmid pHV1 of Haloferax volcanii
Authors: Schalkwyk Leonard C. , Charlebois Robert L. , Doolittle W. Ford
Published: May 2010

We have searched the cloned 86 kilo base pair plasmid pHV1 from Haloferax volcanii for repeated sequence elements, of which we expected it to be a rich source. It contains five copies of the previously characterized element ISH51 and a total of five copies of three uncharacterized elements. pHV1 is part of an AT-rich fraction of the DNA that is likely to be a preferred site for IS insertion.Key words: Haloferax volcanii, pHV1 repeated sequence elements, ISH51.
Degradation of acrylamide by immobilized cells of a Pseudomonas sp. and Xanthomonas maltophilia
Authors: Nawaz Mohamed S. , Franklin Wirt , Cerniglia Carl E.
Published: May 2010

Two bacterial isolates capable of utilizing acrylamide as the sole source of carbon and nitrogen were isolated from herbicide-contaminated soil samples and identified as Pseudomonas sp. and Xanthomonas maltophilia. Batch cultures of Pseudomonas sp. and X. maltophilia completely degraded 62.8 mM acrylamide to acrylic acid and ammonia in 24 and 48 h, respectively. Pseudomonas sp. And X. maltophilia, when immobilized in calcium alginate, markedly increased the rate of degradation of acrylamide over batch cultures. Cells of the isolates immobilized in calcium alginate degraded acrylamide to acrylic acid and ammonia in less than 6 h. Initial metabolism of acrylamide by immobilized cells of Pseudomonas sp. followed by inoculation with nonimmobilized cells after 6 h totally removed acrylamide and its metabolites in 72 h. A similar procedure with X. maltophilia resulted in the total metabolism of acrylamide in 96 h. An inducible, intracellular amidase was responsible for the hydrolysis of acrylamide to acrylic acid and ammonia. The specific activity of Pseudomonas sp. amidase was higher than the specific activity of X. maltophilia amidase.Key words: acrylamide, biodegradation, immobilization.
Localization of carbon monoxide dehydrogenase in acetate-adapted Methanosarcina barkeri
Authors: Gokhale J. U. , Aldrich H. C. , Bhatnagar L. , Zeikus J. G.
Published: May 2010

Immunogold labeling techniques were utilized to determine the cellular location of carbon monoxide dehydrogenase in the methanogenic bacterium Methanosarcina barkeri grown on acetate to enhance levels of the enzyme. Formaldehyde fixation followed by dehydration in methanol and embedment in Lowicryl K4M resin preserved the antigens. Sections were labelled with primary polyclonal rabbit antibody followed by protein A - gold. Low levels of labeling were improved by use of an antibody to protein A followed by a second incubation on protein A - gold. The enzyme is primarily located in the cytoplasm, which agrees with biochemical results showing that it resides in the soluble cellular fraction.Key words: Methanosarcina barkeri, methanogen, methanogenesis, enzyme localization, immunogold.
Evidence for a dual-specificity isocitrate dehydrogenase in the euryarchaeotan Thermoplasma acidophilum
Authors: Potter Simon
Published: May 2010

The thermoacidophilic euryarchaeotan Thermoplasma acidophilum occupies a paradoxical place in phylogenetic trees. It has been found to possess both NAD- and NADP-dependent isocitrate dehydrogenase activities. Kinetic evidence presented suggests that both activities are functions of the same protein. The significance of this result, evolutionary and otherwise, is discussed.Key words: archaea, isocitrate dehydrogenase, molecular evolution.
Na+ responses of two marine bacteria that did not appear to require Na+ for growth
Authors: Manuel Michelle F. , Wisse Gesine A. , MacLeod Robert A.
Published: May 2010

Two Gram-negative heterotrophic marine bacterial strains had been reported not to require Na+ when grown on a chemically defined medium solidifed with purified agar and prepared without added Na+. When these strains were tested in a chemically defined liquid medium they required at least 3 mM Na + for growth. The agar used in the plating medium was found to contribute 3.3 mM Na+. Increasing the concentrations of Na+ in the liquid medium above 3 mM increased the rate and extent of growth of both organisms and decreased the lag periods. Optimal Na+ concentrations for growth varied from 100 to 500 mM depending on the organism and the carbon source in the medium. Na+ was also required for the transport of the carbon source into the cells. For the maximal rate of transport of L-glutamate, one organism required only 10 mM Na +, the other, 50 mM. For acetate and succinate transport the optimal Na+ concentrations varied from 30 to 200 mM depending on the substrate and the organism. When the initial rate of transport of glutamate into one of the organisms was plotted against Na+ concentration the reponse curve was sigmoid and a Hill plot of the data indicated that the transport protein may possess three binding sites for Na+. Evidence was obtained indicating that both organisms possess a Na+-stimulated NADH oxidase. The results indicate that there are marine bacteria that grow to a limited extent at appreciably lower concentrations of Na+ than have been realized previously and for these a much more definitive examination of the requirement for Na+ is necessary.Key words: marine bacteria, Na+ requirement, growth, membrane transport, NADH oxidase.
Polyamine distribution patterns serve as a phenotypic marker in the chemotaxonomy of the Proteobacteria
Authors: Hamana Koei , Matsuzaki Shigeru
Published: May 2010

Polyamines of various genera of the class Proteobacteria were analyzed by high-performance liquid chromatography to determine if they can serve as taxonomic markers. The major polyamine of Zymomonas was homospermidine, whereas the Acetobacter–Gluconobacter complex contained spermidine, suggesting the presence of two different polyamine distribution patterns in the alpha subclass. Both the homospermidine-dominant type and the spermidine-dominant type were found in heterogeneous Sphingomonas species. Typical species belonging to the gamma subclass have their own unique polyamine pattern in Xanthomonas (spermidine), Azomonas (putrescine), Frateuria (spermidine), Alteromonas (putrescine–spermidine or spermidine), Shewanella (putrescine), Marinomonas (putrescine–spermidine or spermidine), Halomonas (putrescine–spermidine or spermidine), and Deleya (spermidine). Cadaverine was sporadically distributed in some species in these genera. Some strains classified into Rhizobacter, Zoogloea, Azomonas, or Alteromonas contained 2-hydroxyputrescine found exclusively in the beta subclass. Polyamine distribution patterns are genus- and (or) species-specific and can serve as a phenotypic marker in the chemotaxonomy of the Proteobacteria.Key words: polyamine, chemotaxonomy, Proteobacteria.
The use of bioluminescence as a reporter to study the adherence of the plant growth promoting rhizopseudomonads 7NSK2 and ANP15 to canola roots
Authors: Boelens J. , Zoutman D. , Campbell J. , Verstraete W. , Paranchych W.
Published: May 2010

The adherence of the plant growth promoting rhizopseudomonads Pseudomonas aeruginosa 7NSK2 and Pseudomonas fluorescens ANP15 to canola roots (Brassica campestris L. c.v. Tobin) was examined by means of a bacterial bioluminescence system. The bioluminescence broad host range vector pDLUX-I was constructed from pLAFR-I and the lux A–E genes of Vibrio fischerii. This vector was conjugally transferred into the plant growth promoting rhizopseudomonads 7NSK2 and ANP15. The transformed strains were constitutively bioluminescent at an optimal temperature of 21 °C. The measured bioluminescence was directly proportional to the density of the bacteria in suspension and was the same for both planktonic and sessile bacteria adhering to the root surface. The adherence of the plant growth promoting rhizopseudomonads was proportional to the density of the bacterial inoculum, approached saturation at 60 min, and was reversible. The kinetics of the microbial adhesion was described by a Freundlich isotherm suggesting that the adherence of the bacteria to the canola root surface does not involve specific receptors. We conclude that the pDLUX-I vector is an easy and accurate way to study the kinetics of microbial adherence to the rhizoplane.Key words: rhizopseudomonads, bioluminescence, adhesion, plant growth promotion.not available
Metabolic regulation of endoglucanase synthesis in Trichoderma reesei: participation of cyclic AMP and glucose-6-phosphate
Authors: Šesták Sergej , Farkaš Vladimír
Published: May 2010

The synthesis of endoglucanase by young induced mycelia of Trichoderma reesei QM 9414 incubated in the presence of 1 mM sophorose (a potent cellulase inducer) was stimulated or repressed by additions of dibutyryl cyclic AMP (dBcAMP), depending on the concentration. At low concentrations (10−6 and 10−5 M), dBcAMP stimulated the formation of endoglucanase; higher concentrations of dBcAMP (10−3 and 10−2 M) repressed the synthesis of endoglucanase. Addition of the phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (IBMX) at 1 and 10 μM concentrations to young induced mycelia caused an increase in intracellular cAMP and stimulated the production of endoglucanase. Neither exogenous dBcAMP nor IBMX was capable of inducing endoglucanase synthesis by itself, and neither was able to relieve catabolite repression of endoglucanase synthesis caused by glucose. All of the monosaccharides tested caused a more or less transient increase in intracellular cAMP. However, the effect of these treatments on endoglucanase synthesis was varied. The phosphorylable hexoses, both metabolizable and nonmetabolizable, increased the intracellular level of glucose-6-phosphate or its analogs and repressed endoglucanase synthesis. Nonphosphorylable sugars, such as 6-deoxyglucose, xylose, L-fucose, and (or) L-sorbose, did not influence the glucose-6-phosphate level and stimulated endoglucanase production to varying degrees. It is concluded that both cAMP and glucose-6-phosphate are involved in regulating cellulase synthesis in T. reesei. However, these factors seem to act in opposing directions.Key words: endoglucanase, induction, catabolite repression, metabolic regulation, glucose-6-phosphate, cyclic AMP, Trichoderma reesei.
Accumulation of factor F395 in nifNE mutants of Klebsiella pneumoniae
Authors: Downs Diana M. , Ludden Paul W. , Shah Vinod K.
Published: May 2010

The nifNE gene products of Klebsiella pneumoniae are required for the in vivo and in vitro synthesis of the iron-molybdenum cofactor (FeMo-co) of nitrogenase. Derepression of nifNE mutants for nitrogenase resulted in the accumulation of a small molecule, factor F395. Factor F395 is protein associated in vivo. We report here initial spectral characterization of this factor.Key words: FeMo-co, nitrogen fixation, Klebsiella pneumoniae, nifNE.
Accumulation of intracellular carbon reserves in relation to chloramphenicol biosynthesis by Streptomyces venezuelae
Authors: Ranade Neelima , Vining Leo C.
Published: May 2010

Two chloramphenicol-producing strains of Streptomyces venezuelae accumulated small amounts of polyhydroxybutyrate during exponential growth; the compound disappeared from the mycelium as the cultures entered stationary phase. Depletion of polyhydroxybutyrate coincided with chloramphenicol production but the amount of polymer stored in the mycelium was insufficient to supply the precursor requirement for biosynthesis of the antibiotic. Accumulation of polyhydroxybutyrate in the S. venezuelae strains was appreciably lower than in two other streptomycetes examined. Glycogen and lipids accumulated in the mycelium of S. venezuelae 13s during the stationary phase, after nitrogen depletion; under the culture conditions used, they were the principal storage compounds in S. venezuelae. Trehalose was absent from the mycelium in vegetative cultures grown under nonsporulating conditions but it was abundant in spores obtained from submerged and surface cultures. Glycogen and polyhydroxybutyrate were absent from spores.Key words: storage compounds, biosynthesis, polyhydroxybutyrate, glycogen, trehalose, lipid.
Conformity and diversity among field isolates of Rhizobium leguminosarum bv. viciae, bv. trifolii, and bv. phaseoli revealed by DNA hybridization using chromosome and plasmid probes
Authors: Laguerre Gisèle , Geniaux Eric , Mazurier Sylvie Isabelle , Casartelli Raquel Rodriguez , Amarger Noëlle
Published: May 2010

A study was made of 113 bacterial isolates from root nodules of peas, lentils, red clover, and French beans, which had been grown in the same soil. Plasmid band profiles visualized in Eckhardt gels were analysed in relation to DNA hybridization patterns obtained by probing restricted total cellular DNA in Southern blots. Rhizobium leguminosarum chromosomal probes (plac12, pCOS309.1) and various symbiotic plasmid (nod gene region) probes were used. Dominant plasmid DNA hybridization patterns and more frequent combinations of plasmid patterns and chromosomal types were found among the isolates of each host plant species; the occurrence of alternative combinations indicated that genetic transfer and recombination among members of this soil population had taken place. About 40% of all isolates belonged to the same chromosomal type. Isolates of the same chromosomal type were often found with cryptic plasmids of the same size in different host plant species. Although isolates could not be assigned to their respective plant host groups using chromosomal probes alone, this was generally possible using symbiotic plasmid probes and the results were in complete accordance with plant tests. However, there was a group of bean isolates in which no homology to any of the R. leguminosarum probes was detected under the conditions of high stringency used. Other exceptional isolates of beans conformed in probe tests and subsequent plant host specificity tests better to biovars viciae or trifolii than to biovar phaseoli; thus, the nodulation of beans (i.e., Phaseolus vulgaris) in the field appears less subject to stringent control of specificity than that of other host plant species. It was also noted that the nod gene regions probed showed greater diversity in isolates of biovars viciae and trifolii than in biovar phaseoli.Key words: Rhizobium leguminosarum, genetic diversity, plasmid, DNA hybridization, restriction fragment length polymorphism.
Nitroaromatic compounds serve as nitrogen source for Desulfovibrio sp. (B strain)
Authors: Boopathy R. , Kulpa C. F.
Published: May 2010

A sulfate-reducing bacterium, Desulfovibrio sp. (B strain), isolated from a continuous anaerobic digester, used various nitroaromatic compounds such as 2,4-dinitrophenol, 2,4-dinitrotoluene, and 2,6-dinitrotoluene as sole nitrogen sources for growth and also used these compounds as electron acceptors in the absence of sulfate in the culture medium. More than 60% of the nitroaromatics were transformed within 6 days of incubation. The organism also used aniline as sole nitrogen source, but not as an electron acceptor. Desulfovibrio sp. (B strain) did not use nitroaromatics as sole source of carbon and energy. The nitro groups in the aromatic ring were reduced and reductively deaminated to ammonia, which was used as nitrogen source, leaving the aromatic ring intact. Even though this organism did not degrade the nitroaromatics completely, it may be useful in degrading nitroaromatics in contaminated soil and water containing other aromatic degraders in a syntrophic culture system under anaerobic conditions.Key words: anaerobic process, biotransformation, nitroaromatics, aniline, Desulfovibrio sp.
Reduction of ferric iron by Listeria monocytogenes and other species of Listeria
Authors: Deneer Harry G. , Boychuk Irene
Published: May 2010

One mechanism by which Listeria monocytogenes is thought to obtain iron required for growth is through the extracellular reduction of a ferric iron source to the ferrous form. To better characterize this reductase activity we have developed a simple plate assay that allows detection of colonies of Listeria species able to reduce ferric iron. Cells are plated on an agar base medium containing a ferric iron source and ethylenediamine dihydroxyphenylacetic acid. Colonies are then overlain with soft agarose containing NADH, flavin mononucleotide, and Ferrozine, a chelator of ferrous iron. Colonies able to reduce the ferric iron source form a red-purple color as the ferrous iron is complexed with ferrozine. Using this qualitative assay we have shown that all species of Listeria are able to reduce ferric iron when presented as ferric ammonium citrate whereas most other species of Gram-positive and Gram-negative bacteria are not. Only Clostridium perfringens was able to reduce ferric iron to the same extent as Listeria. Listeria monocytogenes was further shown to be capable of reducing various ferric iron salts as well as iron bound to ferritin, transferrin, and 2,3-dihydroxybenzoic acid in the agar plate assay. The utility of this assay was demonstrated by using it to screen a bank of Tn9/6-derived mutants of L. monocytogenes for clones unable to reduce ferric iron. Four such mutants were identified and all were shown to have greatly decreased ferric reductase activity.Key words: Listeria, ferric reductase, reductase mutants.
Properties of the genus Tatlockia. Differentiation of Tatlockia (Legionella) maceachernii and micdadei from each other and from other legionellae
Authors: Fox K. F. , Brown A.
Published: May 2010

The biochemical reactions, carbohydrate content, and 16S-rRNA sequences of Tatlockia (Legionella) maceachernii and Tatlockia micdadei strains were studied. Except for catalase activity, Tatlockia strains were relatively inert in the biochemical tests commonly used in clinical laboratories. Phenotypically, the two Tatlockia species could be distinguished from other legionellae by the presence of yersiniose A, by their inability to hydrolyze hippurate or starch, by the absence of colony or media fluorescence, and by the absence of distinct browning of tyrosine-containing medium. These two species differed from one another by the production of acetoin by T. micdadei but not by T. maceachernii. Gelatinase activity, which had been reported in T. maceachernii, was observed in only one of the four strains studied. The 16S-rRNA sequences and carbohydrate profiles of T. maceachernii and T. micdadei were essentially identical. In preparing the RNA for study, it was noted that the 23S rRNA was fragmented in all T. maceachernii strains tested, while the 23S rRNA of T. micdadei strains was intact. Among the legionellae studied, T. maceachernii was most closely related to T. micdadei.Key words: legionellae, Tatlockia, 16S rRNA, 23S rRNA, sugars, taxonomy.
Antibody specificities of polyclonal rabbit and rainbow trout antisera against Vibrio ordalii and serotype 0:2 strains of Vibrio anguillarum
Authors: Mutharia Lucy W. , Raymond Bonnie T. , Dekievit Teri R. , Stevenson Roselynn M. W.
Published: May 2010

Polyclonal rabbit antisera raised against Vibrio ordalii and serotype 02 strains of Vibrio anguillarum showed extensive cross-reactivity with lipopolysaccharide from these bacterial pathogens of fish when tested in western immunoblot analysis. Results with absorbed polyclonal antisera indicated that lipopolysaccharide molecules from these strains had both common and strain-specific antigenic determinants, which allowed the antisera to be used to differentiate between V. ordalii and serotype 02 strains of V. anguillarum. Unlike rabbits, the immune response in rainbow trout to serotype 02 common antigenic epitopes was dependent on the source of the immunizing lipopolysaccharide antigens. Serum from fish immunized with V. ordalii antigens reacted more extensively with serotype 02 common antigens. In contrast, fish anti-V. anguillarum 02 serum did not interact with O antigens from the V. ordalii strains. Lipopolysaccharide from V. anguillarum serotype 02 and 02a strains showed identical antibody binding properties when interacted with rabbit or fish antiserum to either V. anguillarum 02 or V. ordalii. Lipopolysaccharide from V. anguillarum 02b strains did not interact with the tested rabbit or fish polyclonal sera. The results from this study suggest that fish and rabbits recognise different antigenic determinants in lipopolysaccharide from V. ordalii and serotpye 02 V. anguillarum strains; that V. ordalii and serotype 02 strains of V. anguillarum should be regarded as distinct serotype 02 subgroups based on the strain-specific antigenic determinants; and finally that the serological classification of V. anguillarum serotype 02b strains should be reexamined.Key words: antigenic heterogeneity, lipopolysaccharides, fish immune response.not available
Influence of inoculum production temperature on carpogenic germination of sclerotia of Sclerotinia sclerotiorum
Authors: Huang H. C. , Kozub G. C.
Published: May 2010

Three isolates of Sclerotinia sclerotiorum, sun-87 from Alberta, Tai from Taiwan, and SS-12 from Florida, were compared for carpogenic germination of sclerotia produced on potato dextrose agar cultures incubated at 20 °C for 14, 21, or 42 days. Sclerotia formed at 20 °C could germinate carpogenically without a cold conditioning treatment and the level of germination was dependent on specific inoculum temperature requirements for isolate sources. The favorable inoculum temperature for carpogenic germination of daughter sclerotia formed at 20 °C was 10 °C for isolate sun-87, but 25 or 30 °C for isolates Tai and SS-12. There was no difference in carpogenic germination of sclerotia from different inoculum types (mycelial mats or sclerotia) or of different culture ages (14, 21, or 42 days old).Key words: Sclerotinia sclerotiorum, carpogenic germination, source of inoculum.
Occurrence and isolation of vesicular–arbuscular mycorrhizae in cropped field soils of Saskatchewan, Canada
Authors: Talukdar Narayan C. , Germida James J.
Published: May 2010

Soil and root samples collected from fields cropped to spring wheat (Triticum aestivum L. cv. Katepwa) and lentil (Lens esculenta L. cv. Eston) at 11 sites across four soil zones of Saskatchewan were analyzed for spore numbers, level of vesicular–arbuscular mycorrhizal (VAM) colonization, and VAM species. The number of VAM spores detected in field soils ranged from 78 to 272 per 100 g soil. Vesicular–arbuscular mycorrhizae colonized wheat and lentil at all the field study sites, but levels of colonization in the two crops varied from site to site and the differences were more pronounced in wheat than in lentil. Generally, lentil both exhibited a higher percentage of VAM colonized roots and contained more arbuscules and vesicles than wheat roots. However, wheat appeared to be colonized by different types of VAM depending on the field sites. Differences in VAM colonization were not related to the moisture and temperature gradient of the four soil zones or soil properties. Seven VAM species were isolated by enriching indigenous VAM mixtures (collected from wheat field soils of six field sites) on maize. The VAM isolated most closely resembled Acaulospora denticulata, Gigaspora decipiens, Glomus clarum, Glomus etunicatum, Glomus fasciculatum, Glomus mosseae, and Glomus versiforme. The species composition of the VAM community varied at the different field sites.Key words: VAM, Acaulospora, Gigaspora, Glomus.
Host range and transfer efficiency of incompatibility group HI plasmids
Authors: Maher Declan , Taylor Diane E.
Published: May 2010

HI plasmids are distinguished by their thermosensitive mode of conjugation (transfer efficiency is optimal at 22–30 °C) and their capacity to encode multiple antibiotic resistance. These traits have implicated HI plasmids as potential vectors in the dissemination of antibiotic resistance among pathogenic and indigenous bacterial species in water and soil environments. We compared the transfer efficiency of HI plasmids with that of plasmids from 13 other incompatibility groups at 37, 24, and 14 °C in intragenic conjugations between laboratory strains of Escherichia coli K-12 under in vitro conditions. Only the HI plasmids and a representative plasmid from incompatibility groups M, N, Pα, T, and W were observed to be transmissible at 14 °C. These plasmids, along with HI plasmids and the related HII representative, were tested for their host range and transfer proficiency to Enterobacteria species and some other Gram-negative organisms of environmental significance at 24 and 14 °C. Notable differences in the host range of HI plasmids compared with plasmid representatives from the other enterobacterial groups were not evident at 24 °C. At 14 °C, R478 (HI2) displayed the broadest host range and transfer proficiency among the test plasmids. The ability of several plasmid groups, including HI, to transfer at 14–24 °C to Vibrio cholerae non 01, Salmonella typhi, and the fish pathogens Aeromonas salmonicida, Vibrio anguillarum, and Yersinia ruckeri needs to be corroborated by in situ studies.Key words: conjugation, plasmids, thermosensitive transfer, host range.
Factors affecting PCB degradation by an implanted bacterial strain in soil microcosms
Authors: Barriault Diane , Sylvestre Michel
Published: May 2010

Pseudomonas testosteroni B-356 was able to degrade approximately 50% of the Aroclor 1242 mixture in shaken culture. The aims of the present study were to evaluate the capabilities of this bacterial strain to degrade PCBs in soil microcosms and to identify some of the factors likely to favor the degradative performance of the implanted bacteria. The presence of biphenyl as cosubstrate was the most important factor affecting PCB degradation in soil. However, because biphenyl was rapidly depleted in soil microcosms, repeated addition of small amounts of biphenyl to maintain a constant level of the cosubstrate allowed the achievement of a higher degree of degradation of the tetrachlorinated components of Aroclor 1242 than was achieved with a single addition at the time of inoculation. Degradation of di- and tri-chlorinated PCB congeners was less affected by repeated addition of biphenyl because these congeners were degraded very fast and complete degradation was achieved before biphenyl was depleted in the soil. Biodegradation was also related to bioavailability of the substrate. We observed that the proportion of each congener degraded was higher in the microcosms receiving both the producer of the surface-active agent, Alcaligenes faecalis B-556, and strain B-356. Under the best conditions (presence of a constant level of biphenyl and of strain B-556) P. testosteroni B-356 was able to degrade approximately 30% of the Aroclor 1242 added to soil microcosms; some other factors reducing the PCB degradation capabilities of the implanted bacteria are also discussed.Key words: Aroclor 1242, biodegradation, bioremediation, Pseudomonas, soil.
Incorporation of 5-fluorouracil into RNA by Mycobacterium avium complex strain LM1
Authors: Abdulmalek S. , Montoya D. P. , McCarthy C. M.
Published: May 2010

The incorporation of 5-fluorouracil (FUra) into RNA of Mycobacterium avium complex strain LM1 was evaluated. Cells were labeled with either [14C]FUra or [3H]uracil and the ribonucleosides were analyzed by high-performance liquid chromatography. The identification of the ribonucleosides was facilitated by the use of an isocratic system that provided unambiguous identification of the RNA pyrimidine components. Uracil was incorporated into RNA as uridine, but an equal amount was converted to cytidine. [14C]FUra was incorporated directly into RNA as 5-fluorouridine and there was no evidence of its conversion to other pyrimidines. The ratio of 5-fluorouridine:uridine was 2.8-fold greater for cells grown in 100 μg FUra/mL than for cells grown in 20 μg FUra/mL. Analysis of the RNA nucleotides was performed and deoxyribonucleotides were present; DNA contamination was estimated to range from about 2 to 8% of the RNA preparations.Key words: 5-fluorouracil, RNA, Mycobacterium avium complex, HPLC, ribonucleoside.
Inhibition of the growth of grain-storage molds in vitro by the yeast Pichia anomala (Hansen) Kurtzman
Authors: Björnberg Anna , Schnürer Johan
Published: May 2010

The potential use of yeasts to control grain-storage molds was evaluated by coculturing the yeast Pichia anomala with Penicillium roqueforti and Aspergillus candidus on agar plates, using different temperatures, water activities (aw), and nutrient concentrations. Addition of 10 ppm cycloheximide to malt-extract agar inhibited Pichia anomala completely without affecting mold growth, making it possible to quantify the inhibition as a reduction in colony-forming units (cfu). For A. candidus, numbers of cfu and hyphal lengths were reduced at an initial yeast concentration of 104 cells/plate and reduced below detection limit at 108 cells/plate. A clear reduction in growth of Penicillium roqueforti was only observed at 108 yeast cells/plate. The antagonistic effect was generally more pronounced at low (6, 15 °C) and high (30, 37 °C) temperatures than at ambient ones. Pichia anomala inhibited growth of both molds more strongly in a substrate-rich medium than in a medium with a low substrate content. In water agar (low substrate concentration) the degree of inhibition of Penicillium roqueforti was larger at 0.96 aw than at 0.98 aw.Key words: biological control, Aspergillus candidus, Penicillium roqueforti.
Inhibitory action of elemental sulphur (S°) on fungal spores
Authors: Beffa Trello
Published: May 2010

The fungitoxic effect of increasing concentrations of elemental sulphur (S°) was studied during the pregermination period of spores of Phomopsis viticola and conidia of Neurospora crassa. High concentrations of S° (> 10 μM final concentration) inhibited respiratory activities strongly and decreased the ATP content of spores and conidia. S° at low concentrations (1 and 3 μM final concentration) did not inhibit the respiratory activities or ATP content of spores and conidia. In spores of P. viticola, low concentrations of S° were reduced by the cells with the production of hydrogen sulphide (H2S), principally at the level of the respiratory chain. However, in the presence of a high concentration of S°, the capacity to reduce S° increased, and was then most probably independent of the respiratory activities. Proteic and nonproteic sulphydryl groups important in cellular metabolism were probably responsible for almost all the reduction of S°. In fact, the addition of increasing concentrations of S° to spores of P. viticola resulted in a dramatic increase in oxidized glutathione, suggesting the participation of reduced glutathione in S° reduction. In conclusion, we suggest that the fungicidal action of S° is probably related to the oxidation of important sulphydryl groups and not to the competitive interaction between S° and oxygen at the level of the respiratory chain.Key words: elemental sulphur, fungicide, fungi, Neurospora crassa, Phomospis viticola.