bluuebunny/crossref_metadata_2025 huggingface dataset:
Exopolymers from curdlan production: incorporation of glucose-related sugars by Agrobacterium sp. strain ATCC 31749
Authors: Lee Jin W. , Yeomans Walter G. , Allen Alfred L. , Kaplan David L. , Deng Frank , Gross Richard A.
Published: February 2010

Three different exopolymers were purified from cultures of Agrobacterium sp. strain ATCC 31749 grown in a mineral salts medium containing 2% glucose at 30 °C for 5 days under aerobic culture conditions. These exopolymers were curdlan (extracellular, homo-β-(1-3)-glucan, water insoluble at neutral pH), a water-soluble noncurdlan-type exopolymer A (WSNCE-A), and a water-soluble noncurdlan-type exopolymer B (WSNCE-B). Curdlan, WSNCE-A, and WSNCE-B composed by weight 61, 27, and 12%, respectively, of the exopolymer produced from glucose. Compositions of all polymers were confirmed by gas chromatography (GC) and gas chromatography – mass spectrometry (GC–MS). The WSNCE-A is composed of glucose and galactose with lower contents of rhamnose. The WSNCE-B consists of glucose and mannose. To biosynthesize modified biopolymers, glucose-related sugars including 3-O-methyl-D-glucose, 2-amino-2-deoxy-D-glucose, and 2-acetamido-2-deoxy-D-glucose (N-acetylglucosamine) were fed separately as the sole carbon source. Using 3-O-methyl-D-glucose, 8 – 12 mol% of the curdlan repeats were 3-O-methyl-D-glucose based on GC and 1H-nuclear magnetic resonance spectrometry. N-Acetylglucosamine was incorporated into WSNCE-A at 10 mol% based on the GC–MS but was not found in curdlan or WSNCE-B.Key words: Agrobacterium sp., curdlan, exopolymer, 3-O-methyl-D-glucose, 2-acetamido-2-deoxy-D-glucose.
Identification of soil bacteria expressing a symbiotic plasmid from Rhizobium leguminosarum bv. trofolii
Authors: Sivakumaran S. , Jarvis B. D. W. , Lockhart P. J.
Published: February 2010

A hundred strains of non-nodulating, Gram-negative, rod-shaped bacteria were isolated from clover–ryegrass pastures on three different soil types and from a sandy loam under lupins. When crossed with Escherichia coli PN200 containing the cointegrate plasmid pPN1, 11 transconjugants gained the ability to form nodules on the roots of white clover (Trifolium repens cv. Grasslands Huia). A nodA probe indicated that they had gained nodulation genes. The identities of these 11 strains and 4 others derived from earlier work on non-nodulating root nodule bacteria, were determined by ribotyping, DNA – DNA hybridization, and partial 16S rRNA sequencing. Good agreement was obtained between the three methods, and 11 of the strains were identified as Rhizobium leguminosarum (6), Rhizobium loti (2), Rhizobium etli (1), Rhizobium tropici (1), and Sinorhizobium meliloti (1). DNA –DNA hybridization indicated that the remaining four strains were related to the Rhizobium leguminosarum reference strains. The existence of several species of non-nodulating rhizobia in pasture soil, including species for which the normal host plant was absent, is discussed in relation to the fate of symbiotic plasmids from Rhizobium seed inoculants. It is also suggested that new species should be named for the geographical region from which they are first isolated rather than the host plant.Key words: Rhizobium, non-nodulating, nonsymbiotic, isolation, identification.
Colonization and weathering of natural sulfide mineral assemblages by Thiobacillus ferrooxidans
Authors: Lawrence J. R. , Kwong Y. T. J. , Swerhone G. D. W.
Published: February 2010

Selected polished thin sections were used as model substrata to investigate the influence of geochemical and electrochemical factors on bacterial colonization and weathering of mixed sulfide minerals. Naturally occurring sulfide assemblages including combinations of pyrite, chalcopyrite, sphalerite, galena, and pyrrhotite were studied. The distribution of Thiobacillus ferrooxidans was mapped using viable negative and positive staining techniques in combination with scanning confocal laser microscopy. The minerals were characterized using scanning electron microscopy and microprobe analyses. Inter- and intra-granular electrode potentials were monitored using microelectrodes. Results of the experiments indicated that the T. ferrooxidans strain preferentially colonized sulfide minerals that were the most electrochemically active. For example, when pyrite, chalcopyrite, and pyrrhotite were in combination, bacteria preferentially colonized the pyrrhotite. In each case it was shown that the mineral colonized was also the anode in a galvanic cell and the site of preferential weathering. Microelectrode measurements confirmed the existence of intergranular potentials. In addition, trace and minor element composition appeared to influence the electrochemical property of the mineral, thus its colonization and weathering pattern. Information of this nature should facilitate prediction of the fate of sulfide minerals in natural and mining environments.Key words: image analysis, confocal microscopy, sulfide minerals, microelectrodes, electrode potential.
Overexpression, purification, and analysis of thec1repressor protein ofPseudomonas aeruginosabacteriophage D3
Authors: Farinha Mark A. , Kropinski Andrew M.
Published: February 2010

A 3.1-kb region of the bacteriophage D3 genome which contains the immunity functions has recently been sequenced (GenBank accession No. L22692). Sequence analysis indicated the presence of a putative repressor gene (c1) whose protein product functions to maintain the bacteriophage genome as a stably integrated prophage in the chromosome of Pseudomonas aeruginosa. A plasmid was constructed that overexpresses repressor C1 protein under control of Ptacin Escherichia coli. C1 protein was subsequently purified and characterized as a 223 amino acid protein with specific binding affinity for 14-base imperfect palindromic operator sequences located on the genome of bacteriophage D3. N-terminal protein sequence data obtained from automated Edman degradation (16 cycles) of purified repressor protein were identical to the predicted sequence based on DNA sequence analysis of the c1 open reading frame.Key words: promoter, repressor, operator, lambdoid phage, Pseudomonas aeruginosa.
Multiple forms of pectic lyases and polygalacturonase fromFusarium oxysporumf,.sp.radicis lycopersici: regulation of their synthesis by galacturonic acid
Authors: Guevara M. A. , Estévez P. , González-Jaén M. T.
Published: February 2010

The r2 isolate of Fusarium oxysporum f.sp. radicis-lycopersici produced several pectic enzymes that differ in substrate preference, reaction mechanism, and action pattern. We detected three forms that have lyase activity, four forms with polygalacturonase activity and one form with pectinesterase activity. Lyases had an absolute requirement for calcium and pIs of 9.20, 9.00, and 8.65. The two more alkaline forms had a weak preference for pectin, whereas the other was more active on polygalacturonate. Polygalacturonases had pIs of 9.30, 7.35, 6.85, and 6.55 and were inhibited by calcium ions. Lyases and polygalacturonases were induced by galacturonic acid and were subject to catabolite repression. Induced synthesis occurred at pHs 5.5 and 8.0 and no increase in lyase activities were promoted by alkalinization of cultures. Pectin lyase had an endo mode of action, whereas pectate lyase and polygalacturonase behaved more as exoenzymes. These results are discussed in relation to the appearance of the different pectic enzymes when the fungus is confronted with a pectic polymer.Key words: Fusarium oxysporum f.sp. radicis-lycopersici, Lycopersicon esculentum, pectate lyase, pectin lyase, polygalacturonase.
Microbiological oxidation of hydrogen sulphide in a biofilter
Authors: Degorce-Dumas J. R. , Kowal S. , Cloirec P. Le
Published: February 2010

The microbial oxidation of hydrogen sulphide present in an air stream was performed using a laboratory-scale biofilter packed with dry wastewater sludge (BSE, boues de station d'épuration) from an urban wastewater treatment plant. This granular and heterogeneous material contains organic and mineral components which favour colonization by bacteria. Adsorption and absorption of hydrogen sulphide taking place on such a packing (moisture content 30–40%) were determined. Results obtained with abiotic pilot units, fed with air (superficial air flow rate, 16 m/h) containing a sulphide level as high as 3260 mg/m3, showed that chemical oxidation can occur. The presence of numerous bacteria such as Thiobacillus spp. (i.e., 108–109 CFU/g dry weight) in biotic pilot units favoured complete oxidation to sulphate. High initial bacterial numbers and a neutral pH improved the removal efficiency of the biofilter. A high sulphide concentration (>3000 mg/m3) had a negative effect on the removal efficiency. The leaching of the metals contained in the sludges was studied. Peat and BSE biofilters were compared.Key words: Thiobacillus spp., hydrogen sulphide, biofilter, deodorization, bioleaching.
Change of cell membrane hydrophobicity in a bacterium tolerant to toxic alcohols
Authors: Tsubata Takuichi , Tezuka Toshiyuki , Kurane Ryuichiro
Published: February 2010

An n-heptanol-tolerant bacterium, i.e., Pseudomonas putida No. 69-3, can be derived from an organic solvent sensitive bacterium with the ability to degrade dibenzothiophene by applying ultraviolet rays and exposing to n-heptanol, as reported previously. When the log P value of the alcohol used during cultivation was low, the quantity ratios of individual free fatty acids to the quantity of free fatty acids plus the fatty acids incorporated in lipids was high, the level of high molecular weight lipopolysaccharides was low, and the cell-surface membrane became hydrophobic. This suggests that when the bacterium was exposed to alcohols with low log P values, meaning ones that easily dissolve in water, the bacterium changed degrees of cell-surface hydrophobicity and adapted to the alcohols.Key words: Pseudomonas putida, organic solvent tolerance, fatty acid, lipopolysaccharide, cell-membrane hydrophobicity.
Energy-dependent accumulation of particulate biosurfactant byPseudomonas marginalis
Authors: Burd G. , Ward O. P.
Published: February 2010

The amount of particulate lipopolysaccharide-containing polymeric biosurfactant PM-factor formed by Pseudomonas marginalis was proportional to the amount of biomass produced. Specific production of PM-factor by growing cells was independent of the substrate used as carbon source and of hydrocarbons added to the growth medium. Rifamycin and chloramphenicol did not influence extracellular surfactant accumulation. Respiratory inhibitors (cyanide and azide), uncouplers of oxidative phosphorylation (carbonylcyanide m-chlorophenylhydrazone), and an ion conductor (gramicidin D) strongly suppressed PM-factor accumulation in the culture broth. Inhibitors of H+-ATPase (dicyclohexylcarbodiimide) and glycolysis (fluoride) did not affect PM-factor accumulation. These observations suggest that PM-factor is released into the surrounding medium by an energy-dependent mechanism.Key words: biosurfactant, Pseudomonas, lipopolysaccharide, energy.
Unusual localization of nod and nif genes in Rhizobium leguminosarum bv. viciae
Authors: Mazurier Sylvie-Isabelle , Laguerre Gisele
Published: February 2010

Genomic DNA from seven strains of Rhizobium leguminosarum bv. viciae isolated from nodules of field-grown lentils showed homology to nod and nif gene probes, whereas plasmid DNA did not hybridize with these probes. The results suggest that symbiotic genes could be located on the chromosome or perhaps on a very large plasmid that could not be resolved in Eckhardt gels. Each strain contained one plasmid that hybridized with a pSym isolated from a R. leguminosarum strain of the same field population. This finding led us to hypothesize that the nod and nif genes of the seven strains might have originated from a Sym plasmid and have been integrated into another replicon. The ability to nodulate vetch was confirmed for all of the seven strains. Thus, wild strains of R. leguminosarum bv. viciae that nodulate vetch carry nod and nif genes either on the chromosome or on an extrachromosomal replicon of size much larger than the pSyms hitherto described.Key words: Rhizobium leguminosarum, nod genes, nif genes, chromosome, symbiotic plasmid, megaplasmid.
Application of the Scholander pressure bomb to studies on endophytic bacteria of plants
Authors: Hallmann J. , Kloepper J. W. , Rodríguez-Kábana R.
Published: February 2010

The Scholander pressure bomb system, which expresses vascular plant sap, was compared with the trituration method, in which roots are surface disinfested and triturated, for recovery of endophytic bacteria. The two methods were compared for recovery of indigenous and introduced endophytes from roots of several plant genera. The pressure bomb method was acceptable for routine recovery of endophytes from cotton (Gossypium hirsutum), soybean (Glycine max), and bean (Phaseolus vulgaris), but owing to tissue collapse under pressure, the method did not work reliably for cucumber (Cucumis sativa) or tomato (Lycopersicon esculentum) seedlings. High bacterial densities on the root surface, experimentally obtained by dipping cotton roots into a suspension of Enterobacter asburiae JM22 immediately prior to processing, did not affect the population densities of recovered indigenous endophytic bacteria by the pressure bomb technique but resulted in increased bacterial densities for the trituration method. Internal populations of JM22 following application as a seed treatment were statistically equivalent with the trituration and pressure bomb techniques. Analysis of taxonomic diversity of a group of indigenous endophytes recovered with the trituration and pressure bomb techniques indicated some differences between the two groups. The total number of bacterial genera and species recovered was greater using the pressure bomb method. Gram-positive species, such as Bacillus spp., were more frequently isolated with the trituration method than with the pressure bomb method. Agrobacterium radiobacter and less common species were more often isolated using the pressure bomb technique. Pseudomonas spp. and Phyllobacterium spp. were recovered with equal frequencies using both techniques. These results suggest that the two techniques sample two different internal habitats available for colonization by endophytic bacteria, i.e., the trituration method recovering mainly endophytes residing in the root cortex and the pressure bomb method detecting vascular colonists. A combination of both methods is recommended for understanding the full pattern of internal plant colonization by endophytic bacteria.Key words: endophytic bacteria, Scholander pressure bomb, isolation method, cotton.
Chitinolytic activity of the acaropathogenic fungiHirsutella thompsoniiandHirsutella necatrix
Authors: Chernin Leonid , Gafni Aviva , Sztejnberg Abraham , Mozes-Koch Rita , Gerson Uri
Published: February 2010

Two isolates of the acaropathogenic fungus Hirsutella thompsonii (Nos. 255 and 414), and Hirsutella necatrix, were able to produce and excrete chitinolytic enzymes. A chitobiase of > 205 kDa was excreted by all fungi and a chitobiase of 112 kDa only by isolate 414. An endochitinase of 162 kDa was excreted by isolate 414 and two endochitinases of 66 and 38 kDa were excreted by isolate 255. Both H. thompsonii isolates produced chitinolytic enzymes only under inducible conditions, in the presence of colloidal chitin as the sole source of carbon. Hirsutella necatrix produced a chitobiase constitutively when grown in the presence of glucose. In addition to chitinolytic enzymes, the H. thompsonii isolates excreted proteolytic activities, including elastase, as well as α-esterase and α-amylase activities. Hirsutella necatrix was unable to use casein, milk powder, or elastin as the sole carbon source. The acaropathogenicity of these isolates was assayed on the carmine spider mite (Tetranychus cinnabarinus). Isolates 414 and 255 and H. necatrix killed ca. 80, 35, and 15%, respectively, of the infected mites. The role of chitinolytic and other enzymatic activities in the acaropathogenicity of these fungi is discussed.Key words: acaropathogenic fungi, Hirsutella, chitobiase, endochitinase, α-amylase.
Acetobacterstrains contain DNA modified at GAATTC and GANTC
Authors: Coucheron Dag H.
Published: February 2010

Total DNAs from nine strains of Acetobacter xylinum, two strains of Acetobacter aceti, and one Acetobacter pasteurianus strain were examined for the extent of digestion by various restriction endonucleases. The majority of the endonucleases cleaved the total DNAs with a frequency expected from the number of sites present in DNA sequences deposited in the GenBank data base. However, the restriction enzyme digestions identified two different genomic DNA modifications in Acetobacter. One sequence-specific modification protected total DNAs from seven of the A. xylinum strains against cleavage by EcoRI (GAATTC). Digestion of total DNAs from A. xylinum ATCC 10245 (DNA not cut by EcoRI) and the closely related A. xylinum NRCC 17005 (DNA cut by EcoRI) with Tsp509I (AATT) revealed differences in restriction frequencies that indicated methylation of the first or second adenine within GAATTC. Another sequence-specific modification rendered total DNAs from all the 12 strains recalcitrant to digestion by HinfI. The latter modification indicated that species of the genus Acetobacter contain a solitary DNA methyltransferase that probably methylates adenine in GANTC.Key words: Acetobacter, genomic DNA, modifications, EcoRI, HinfI.
A simple method for enumerating bacteriophages in soil
Authors: Yin X. , Zeph L. R. , Stotzky G.
Published: February 2010

A plaque technique that uses antibiotic-resistant bacteria growing on antibiotic-containing agar for the assay lawn resulted in significantly better recovery of bacteriophages P1 of Escherichia coli and F116 of Pseudomonas aeruginosa from nonsterile soil than standard membrane filtration or centrifugation techniques. Adsorption of the phages on soil particles appeared to be involved in their recovery and survival in soil.Key words: bacteriophages, soil, antibiotic-resistant bacteria, enumeration, filtration, centrifugation.
Immunolocalization of a β-1,4-endoglucanase from Macrophomina phaseolina expressed in planta
Authors: Jones Richard W. , Wang Haiyin
Published: February 2010

The in planta endoglucanase production by Macrophomina phaseolina was analyzed by probing tissue blots with a peptide-specific antibody. Endoglucanase (EGL 1) was readily detected at 60 h after microsclerotial inoculation to corn and tobacco stems. Production continued through the study, along with growth of the fungus in stem tissue. Endoglucanase was rapidly transported through the xylem, resulting in distribution to distal portions of the plant. Production at the site of infection was correlated with symptom expression, suggesting a role for endoglucanases in disease progression.Key words: cellulase, charcoal rot.
Induction of desiccation tolerance by osmotic treatment in Saccharomyces uvarum var. carlsbergensis
Authors: Eleutherio Elis C. A. , Maia Fernanda M. , Pereira Marcos D. , Panek Anita D. , Degré Richard , Cameron David
Published: February 2010

Saccharomyces uvarum var. carlsbergensis is heat sensitive and when dried by usual procedures exhibits very poor survival. Our results demonstrate that these cells are capable of accumulating trehalose when submitted to an osmotic treatment using 20% solutions of either sorbitol or dextrin endowing them with the capacity of surviving posterior dehydration.Key words: Saccharomyces uvarum var. carlsbergensis, dehydration, trehalose.
Comparison of partial 23S rDNA sequences fromRhizobiumspecies
Authors: Tesfaye Mesfin , Petersen Daniel J. , Holl F. Brian
Published: February 2010

A hypervariable region of Rhizobium 23S rDNA was amplified by polymerase chain reaction and phylogenetic relationships of several strains were determined by comparing nucleotide sequences of the amplified product. Variation in the 23S rDNA nucleotide sequences was consistent with phylogenetic relationships determined by host nodulation specificity and (or) 16S rDNA sequence analysis. Six strains representing three Rhizobium species (R. leguminosarum bv. trifolii, R. meliloti, and R. etli), and two strains each of Bradyrhizobium and Agrobacterium were clustered into five rDNA groups. Unique features identified by secondary structure analysis of the 23S rRNA sequenced region were consistent with the hypothesis that 23S rDNA could be used to design species- or strain-specific Rhizobium probes.Key words: Rhizobium, rDNA, strain identification, phylogeny.
Recombinant plasmid mobilization betweenE.colistrains in seven sterile microcosms
Authors: Lebaron P. , Bauda P. , Frank N. , Lett M. C. , Roux B. , Hubert J. C. , Duval-Iflah Y. , Simonet P. , Faurie G. , Normand P. , Jacq E. , Prieur D. , Baleux B. , Schmitt S. , Block J. C.
Published: February 2010

Transfer by mobilization of a pBR derivative recombinant plasmid lacking transfer functions (oriT+, tra−, mob−) from one E. coli K12 strain to another was investigated in seven sterile microcosms corresponding to different environments. These microcosms were chosen as representative of environments that genetically engineered microorganisms (GEMOs) encounter after accidental release, namely attached biomass in aquatic environments (biofilm), soil, seawater, freshwater, wastewater, mouse gut, and mussel gut. GEMOs survived in the same way as the host strains in all microcosms. Recombinant DNA mobilization occurred in the mouse gut, in sterile soil, and in biofilm. The plasmid transfer rates principally reflected the environmental conditions encountered in each microcosm.Key words: recombinant DNA, plasmid transfer, mobilization, conjugation, microcosm.
Bacterial endophytes in cotton: mechanisms of entering the plant
Authors: Quadt-Hallmann A. , Kloepper J. W. , Benhamou N.
Published: February 2010

Investigations were conducted to determine how a systemic plant-colonizing bacterium Enterobacter asburiae JM22 enters cotton plant tissues. Passive uptake was excluded for JM22 by experimentation with glutaraldehyde-fixed (killed) bacterial cells applied to seeds and leaves; no bacteria were found internally or externally on roots or leaves. In contrast, application of live JM22 cells led to colonization of external and internal root and leaf tissues. Active penetration of JM22 in the absence of external wounding was demonstrated for cotton seedlings germinated on water agar and inoculated with the bacterial suspension. The mean internal bacterial population density for seedlings was 3.8 × 103 CFU/g surface-disinfected radicle tissue. Studies of in planta enzymatic activity demonstrated hydrolysis of wall-bound cellulose in the vicinity of JM22 bacterial cells. The same phenomenon was observed for a cortical root colonizing bacterium, Pseudomonas fluorescens 89B-61, a plant growth-promoting strain with biocontrol potential against various pathogens.Key words: endophytic bacteria, cotton, cell wall hydrolysis.
Recovery of coliform bacteria from rural groundwater supplies using reduced oxygen concentrations during incubation
Authors: Shirey J. J. , Bissonnette G. K.
Published: February 2010

The effect of decreased oxygen concentration during incubation of M-Endo medium on detection of coliforms from rural groundwater supplies was examined. Incubation oxygen concentrations of 0 (anaerobic GasPak), 4, 8, and 21% (atmospheric) were examined. Our findings point to several advantages of using anaerobic incubation for the isolation of coliforms: (i) higher verification rates with concomitant decreases in occurrence of false-positive coliforms; (ii) overall reduction in growth of nonsheen colonies; and (iii) reduction in colony size for nonsheen organisms, thereby minimizing crowding effects and facilitating enumeration of coliform colonies. However, these advantages were not sufficient to permit increased recovery of total coliforms as compared with standard aerobic incubation. In addition, the increased frequency of detecting false-negative coliforms during anaerobic incubation is a disadvantage to this method. While detection of total coliforms was reduced under conditions of anaerobiosis, the detection of fecal coliforms and (or) E. coli was not impeded.Key words: coliforms, anaerobiosis, groundwater, sheen formation.
X-ray microanalysis of intracellular ions in the anaerobic halophilic eubacterium Haloanaerobium praevalens
Authors: Oren Aharon , Heldal Mikal , Norland Svein
Published: February 2010

The intracellular concentrations of Na+, K+, and Cl− of the anaerobic halophilic eubacterium Haloanaerobium praevalens were assayed by means of X-ray microanalysis with the transmission electron microscope. Apparent intracellular cation concentrations between 1.22 and 1.91 M and chloride concentrations of 0.93–1.57 M were measured in cells growing exponentially in 2.6 M total salts. In exponentially growing cells, K+ was the major cation (70% of the cation sum). Stationary phase cells showed a high variability among individual cells, some of the cells containing higher Na+ than K+ concentrations.Key words: Haloanaerobium praevalens, intracellular ion concentrations, sodium, potassium, X-ray microanalysis.
Tributyltin oxide affects energy production in the yeastRhodotorula ferulica, a utilizer of phenolic compounds
Authors: Veiga Alexandra , Pinto Ana Ferreira , Loureiro-Dias Maria C.
Published: February 2010

Rhodotorula ferulica, a yeast able to utilize phenolic compounds, was chosen for evaluating the effects of tributyltin oxide (TBTO) on this utilization. TBTO reduced respiratory capacity when vanillic or benzoic acid was the energy source. The ATP level of the cells was severely affected by 2 μM TBTO. The mitochondrial ATPase was strongly inhibited by 0.5 μM TBTO, whereas the activity of the plasma membrane ATPase was not affected by concentrations of TBTO up to 30 μM. Our data support the hypothesis that the target for TBTO action is the mitochondrial ATPase, resulting in a severe disturbance of the yeast utilization of aromatic compounds.Key words: TBTO, tributyltin, yeast, Rhodotorula ferulica, respiration, ATPase.
Les entérocoques dans l'environnement proche de l'homme
Authors: Flahaut Sigrid , Auffray Yanick , Boutibonnes Philippe
Published: February 2010

Enterococci, fomerly confounded with faecal streptococci, are recognized since the beginning of the century as being faecal in origin and are generally searched for in waste waters and food products; their detection may in fact indicate the presence of enteropathogenic organisms. Although nearly ubiquitous, their preferred ecological niche is the intestine sphere. Rejected in the environment by means of human faeces or animal dejecta, they are scattered afterwards in diverse niches. Once in the external environment, their survival is linked with their exceptional aptitude to resist or grow in hostile environments that are usually detrimental to the development of most mesophilic microorganisms. However, a certain ambiguity exists concerning their relationships with human beings. In fact, certain enterococcus strains or species are used in the elaboration of some milk products. Conversely, others are opportunists and may cause severe infections to people from infants to adults. Moreover, undergoing adaptation perpetually, they present a multiresistance pattern to antibiotics. Thus, the barrier that separates bacteria as nonoffensive contaminants from powerful pathogens appears most fragile, suggesting that people must systematically consider suspect the presence of enterococci in their near environment.Key words: enterococci, biochemical properties, resistance, biotopes, opportunism.
Typing Tuber ectomycorrhizae by polymerase chain amplification of the internal transcribed spacer of rDNA and the sequence characterized amplified region markers
Authors: Gandeboeuf Delphine , Dupré Chantal , Chevalier Gérard , Nicolas Paul , Roeckel-Drevet Patricia
Published: February 2010

Identification of some economically important Tuber species using classical morphological characteristics is sometimes difficult. We report here the molecular characterization of a species coming from China, Tuber indicum, mistaken with Tuber melanosporum species. Using restriction analysis of the amplified internal transcribed spacer (ITS) of rDNA, ITS sequence analysis, and sequence characterized amplified region markers, with DNA from fruit bodies or mycorrhizae, genetic variation was found between these two species, allowing to differentiate and characterize them.Key words: molecular identification, Tuber, internal transcribed spacer, sequence characterized amplified region.
Comparative analysis of subcellular distribution of protein antigens inMycobacterium bovisbacillus Calmette–Guérin
Authors: Florio W. , Freer G. , Casa B. Dalla , Batoni G. , Maisetta G. , Senesi S. , Campa M.
Published: February 2010

The distribution of protein antigens in purified subcellular fractions of Mycobacterium bovis bacillus Calmette–Guérin (BCG) was comparatively analysed by sodium dodecyl sulfate – polyacrylamide gel electrophoresis and immunoblotting with specific monoclonal antibodies and polyclonal sera. The 19- and 38-kDa lipoproteins were mainly detected in the cell wall and cell membrane enriched fractions, and they were extracted from the former by Triton X-114 and Nonidet P-40. The 65-kDa heat-shock protein (hsp) was present in the cytoplasmic fraction and only trace amounts were found in the crude cell wall preparation. In contrast, the 14-kDa hsp was highly represented in the cell wall fraction, besides being present in cytoplasmic fraction. Both superoxide dismutase (SOD) and antigen 85 complex (Ag 85) were abundantly released in culture medium, and to a lower extent, they were present in the cell wall fraction; SOD was present in comparable amounts also in the cytoplasmic fraction, while Ag 85 was far less represented in the same. Sera from mice immunized with culture filtrate (CF) proteins of BCG recognized several antigens in CFs, which were not detectable in cell wall, cell membrane, and cytoplasmic fractions, indicating that CF proteins include secreted antigens which have not yet been identified.Key words: bacillus Calmette–Guérin, monoclonal antibodies, subcellular localization.
Seasonal and site-specific variations in nitrogen fixation in a high arctic area, Ny-Ålesund, Spitsbergen
Authors: Liengen Turid , Olsen Rolf Arnt
Published: February 2010

Nitrogen fixation was measured in different habitats in the area of Ny-Ålesund, Spitsbergen, using the acetylene reduction method on intact soil cores and Nostoc commune growing in macroscopic sheet communities. The samples were incubated both under constant conditions (19 °C and 200 μE∙m−2∙s−1) and under in situ conditions. Cyanobacteria were considered to be the major nitrogen-fixing organisms. The nitrogen fixation rates showed a seasonal variation during the growing season of 1994, with low activities just after the snow melt, increasing until the middle of August and showing a rapid decline after the snow fell on August 29. The soil temperature at the time of sampling showed a positive, linear correlation with the nitrogen fixation activities measured on intact soil cores, whereas the nitrogen fixation activities measured in situ of N. commune showed a positive, linear dependence on the moisture content in the sheets and the incubation temperatures inside the incubation vessels during the experiments. The optimal temperature of the nitrogen fixation activity was about 20 °C, both for N. commune and a Puccinellia salt marsh. The highest nitrogen fixation rate measured in situ was at a patterned ground, which had the highest pH, the highest concentrations of extractable calcium and magnesium, and the highest C:N ratio measured.Key words: nitrogen fixation, cyanobacteria, Nostoc commune, high arctic.
Randomly amplified polymorphic DNA using the M13 core sequence of the vesicular–arbuscular mycorrhizal fungi Gigaspora margarita and Gigaspora gigantea
Authors: Gadkar Vijay , Adholeya Alok , Satyanarayana T.
Published: February 2010

Vesicular–arbuscular mycorrhizal (VAM) fungi are obligate symbionts, and a primary benefit provided to the host is the alleviation of stress. The recalcitrance of these fungi to grow in pure culture has spurred researchers to develop an alternative form of cultivation, namely the root organ culture (ROC). This synthetic form of production is new and efforts were made to use randomly amplified polymorphic DNA with the M13 minisatellite sequence as the polymerase chain reaction primer to look into polymorphism, if any, in the spores of Gigaspora margarita produced both in vitro and in situ (soil). The fingerprint patterns obtained from in vitro and in situ spores were similar. Extramatrical structures, such as auxiliary cells, were also examined by DNA fingerprinting. Their amplification pattern did not vary from the mother or daughter spores. A few interesting observations were made. For instance, the mother spore, which seemed hollow and inactive after germination, nevertheless contained nuclei after 4 months under in vitro conditions and generated a fingerprint pattern. The fingerprint pattern for Gigaspora margarita was different from that of Gigaspora gigantea, indicating that the minisatellite sequence could be exploited for identifying VAM fungi. ROC appears to be a truly representative system, in the sense that it mimics the essential features of the complex rhizosphere, allowing the fungi to complete their life cycle without any induced genetic changes per se. Key words : root organ culture, arbuscular mycorrhiza, M13 minisatellite sequence, randomly amplified polymorphic DNA.
Mapping of sequences required for the translation of the β subunit ofEscherichia coliRNA polymerase
Authors: Passador Luciano , Linn Thomas
Published: February 2010

Previous experiments using expression plasmids which overproduce the β and β′ subunits of Escherichia coli RNA polymerase suggested that regions considerably upstream of the start of the rpoB gene, which encodes the β subunit, are required for its efficient synthesis. To further delineate the required regions, a collection of genetic constructs that contained varying amounts of the region either upstream or downstream of the translational start of rpoB was assembled. Measurements of β and β′ synthesis and rpoB mRNA production from a series of rpoBC expression plasmids indicated that sequences extending more than 43 bp but less than 79 bp upstream of rpoB are required for the efficient translation of rpoB mRNA. This result was confirmed by β-galactosidase measurements from a series of rpoB-lacZ fusions that have the same set of end points upstream of rpoB as the expression plasmids. A second set of gene fusions containing differing amounts of the sequence distal to the start of rpoB fused in frame to lacZ revealed that more than 29 bp but less than 70 bp of rpoB was required for efficient translation.Key words: RNA polymerase, E. coli, translational regulation.
Inhibition by polyphosphate of phytopathogenic polygalacturonases from Botrytis cinerea
Authors: Meller-Harel Yael , Argaman Anat , Aharonowitz Yair , Gutnick David , Ben-Bashat Dafna , Navon Gil
Published: February 2010

Polygalacturonase activity from the phytopathogenic fungus Botrytis cinerea was inhibited in vitro by extracellular polyphosphate from Streptomyces sp. A50, as well as other polyphosphates of biological and chemical origin. The extent of inhibition increased with polyphosphate chain length between 20 and 100 Pi residues. Although the activity of polygalacturonase from B. cinerea appeared not to depend on the presence of cations, inhibition was partially blocked by divalent cations such as Mg2+or Ca2+. Production of polyphosphate in Streptomyces sp. A50 was followed by chemical measurements, as well as by in vivo 31P-NMR analysis. During the first 2 days of growth, polyphosphate accumulated within the cells, after which it appeared in the broth as an extracellular product. A maximum concentration of extracellular polyphosphate (1 mM Pi equivalent) was reached, corresponding to about 25% of the input Pi. NMR analysis suggested that the intracellular form of polyphosphate exists as a mobile soluble pool. In contrast, the extracellular form of polyphosphate appears to be complexed with cations.Key words: polygalacturonase, polyphosphate, Botrytis cinerea, Streptomyces, 31P-NMR.
On the origin of variants of the marine bacteriumDeleya aesta134 able to grow at low Na+concentration
Authors: MacLeod Robert A. , MacLeod Patricia R. , Berthelet Marc
Published: February 2010

Deleya aesta 134 grows optimally at 200 mM Na+in a chemically defined medium but at 10 mM Na+only after an extended lag period which was reduced if the cells that grew were reinoculated into medium of the same low Na+concentration. Cells that eventually grew at low Na+formed colonies on agar containing 17 mM Na+in the agar supernatant (the liquid released when the agar was compacted). Cells of the parent failed to form colonies at this Na+concentration when 102cells were plated. Colonies that formed on low Na+agar differed in appearance from colonies of the parent and three colony types were distinguished. When 106cells of D. aesta grown in liquid medium containing optimum Na+were spread on plates containing 17 mM Na+, a few variant colonies first appeared on day 4 and then increased in numbers over a 20-day period. In nine similar cultures the yield of colonies varied over a 3-log range. Fluctuation tests applied to the numbers arising from the similar cultures after different periods of incubation of the plates showed that the ratio of the variance to the mean was much greater than one initially and then increased with time. A total of seven different variants were isolated. These could be distinguished by the colony type formed, the length of the lag time preceding the first appearance of colonies, and the rate of colony accumulation on low (and in one case, high) Na+plates. The variants retained their distinctive characteristics when replated at low Na+after growth at optimum Na+. Differences in lag time and rate of colony accumulation were related to differences in Na+requirement of the variants and to the presence of other colonies on the plates. The variants appear to arise as the result of random mutations in the growing culture. There was no evidence of adaptive mutation.Key words: Deleya aesta, marine bacteria, variants, Na+response, colony accumulation, adaptive mutation.
Influence of fatty acids and detergents on polyether antibiotic production byStreptomyces hygroscopicusNRRL B-1865
Authors: Mouslim Jamal , Haloui Nour-Edine El , David Lucien
Published: February 2010

Addition of pure methyl oleate to a Streptomyces hygroscopicus NRRL B-1865 culture improved polyether antibiotic production, particularly of the closely related nigericin and abierixin, more than did technical methyl oleate. Among the fatty acid constituents of technical methyl oleate, the methyl esters of stearate and particularly linoleate were detrimental to growth and antibiotic production, while the methyl esters of palmitate and palmitoleate had the same effect as technical methyl oleate. The presence of Tween 80 or cyclodextrin in S. hygroscopicus cultures supplemented with methyl oleate increased valine uptake and antibiotic production. Antibiotic production was highest with a mixture of 1% methyl oleate, 0.1% Tween 80, and 0.1% cyclodextrin. The results suggested that the stimulatory effect of methyl oleate might be enhanced by a substance increasing the accumulation of branched amino acids known to be direct precursors of polyether antibiotics. The rate of abierixin synthesis was more important than that of nigericin at the end of the culture. The nigericin/abierixin ratio decreased from 6 in basal medium supplemented with methyl oleate to 2 in basal medium supplemented with methyl oleate, Tween 80, and cyclodextrin. A strong decrease in culture pH seen in the presence of Tween 80 and cyclodextrin might lead to a Michael transformation of nigericin to abierixin.Key words: Streptomyces hygroscopicus, nigericin, abierixin, methyl oleate, Tween 80, cyclodextrin.
Bacillus isolates as potential biocontrol agents against chocolate spot on Faba beans
Authors: Sharga Boris M.
Published: February 2010

Chocolate spot caused by Botrytis cinerea and Botrytis fabae is a serious disease of Vicia faba L. beans. Aggressive infection of that disease can result in severe yield losses (up to 100%). Genetic resistance to chocolate spot in V. faba L. is weak. Chemical control of the disease gives only partial crop protection because of widespread fungicide resistance in both chocolate spot agents. Biological control with applications of bacteria antagonistic to Botrytis may provide a useful alternative to chemicals. Of 270 Bacillus isolates tested, 54 (20%) were found to cause necrosis and (or) chlorosis when placed on leaves of V. faba L. Only 14 strains (6.5%) were able to prevent chocolate spot symptoms from developing in vivo and all of these antagonised Botrytis cinerea and Botrytis fabae in vitro by antibiosis. Bacillus macerans BS 153 was selected for biocontrol experiments in both the greenhouse and field in which plants were sprayed with bacterial suspensions. Detached leaves were inoculated with Botrytis at intervals after Bacillus macerans BS 153 application. The beneficial effect of the biocontrol agent persisted much longer in greenhouse-grown plants. The estimated ED50 was 1.3 times less in the greenhouse spray than in the field spray. From the high number of bacteria required and the rate of decline of introduced Bacillus population in field-grown plants, it was concluded that biocontrol of chocolate spot by Bacillus is impractical unless improved formulations and spray application techniques are developed.Key words: chocolate spot, Bacillus isolates, biocontrol.
The response of methane consumption by pure cultures of methanotrophic bacteria to oxygen
Authors: Ren Tie , Amaral John A. , Knowles Roger
Published: February 2010

The rates of CH4 oxidation by strains of groups I and II methanotrophs in pure culture were studied at various O2 concentrations from 0 to 63 % v/v. In the presence of nonlimiting dissolved CH4 and inorganic nitrogen, O2 concentrations from 0.45 to 20% v/v supported maximum rates of CH4 oxidation. The critical dissolved O2 concentration under our conditions was about 5.7 μM, below which O2 was limiting for CH4 oxidation. Concentrations of O2 up to 63% v/v depressed the activity of CH4 oxidation by ≥ 23%. We conclude that methanotrophs are not microaerophilic under the conditions of our experiments and that they have a high affinity for O2.Key words: CH4 oxidation, O2 response, Methylosinus trichosporium, Methylobacter luteus.
Influence of altered plasma membrane fatty acid composition on cesium transport characteristics and toxicity inSaccharomyces cerevisiae
Authors: Hoptroff Michael J. , Avery Simon V. , Thomas Simon
Published: February 2010

The influence of altered plasma membrane fatty acid composition on cesium uptake and toxicity was investigated in Saccharomyces cerevisiae. Detailed kinetic studies revealed that both the Vmaxand Kmvalues for Cs+transport increased (by approximately twofold in the latter case) when S. cerevisiae was grown in medium supplemented with the polyunsaturated fatty acid linoleate. In addition, Cs+uptake by linoleate-enriched cells was considerably less sensitive to the competitive effects of other monovalent cations (K+, Rb+, and NH4+) than that by unsupplemented cells. Stimulation of Cs+uptake in the presence of certain K+and Rb+concentrations was only evident in linoleate-enriched S. cerevisiae. At 100 mM CsCl, the initial rate of Cs+uptake was greater in linoleate-supplemented cells than in unsupplemented cells and this was reflected in a more rapid displacement of cellular K+. However, little difference in net Cs+accumulation between linoleate-supplemented and unsupplemented cells was evident during prolonged incubation in buffer or during growth. Thus, Cs+toxicity was similar in linoleate-supplemented and unsupplemented cells. The results were consistent with the Cs+(K+) transport mechanism adopting an altered conformational state in linoleate-enriched S. cerevisiae.Key words: monovalent cation transport, plasma membrane fatty acid composition, lipid–protein interactions, metal–microbe interactions, cation competition.
Polarity, spatial organisation of cytoskeleton, and nuclear division in morphologically altered cells ofSchizosaccharomyces pombe
Authors: Sipiczki M. , Grallert A.
Published: February 2010

To gain more information about the determination of cell polarity and its relationship to the organisation of cytoskeleton, we have examined the mycelial mutant sep1-1 and the multinucleate multipolar syncytia of the triple mutant sep1-1 spl1-1 cdc4-8 by indirect immunofluorescence techniques. We have found that polarity is predetermined by the shape of the cell. During transition from mitosis to interphase the microtubules of the arising cytoplasmic cytoskeleton gradually form a basket-like pattern that reflects the curvatures of the cell envelope. The presumable growing poles, where actin accumulates, usually correlates with the sites where the cell tapers and the microtubules converge. However, no growth can be launched at these sites if the cell surface has not been properly processed. Mitosis and meiosis are not affected significantly by changes in cell morphology and polarity, but larger cells are less effective during sporulation. The azygotic asci produced by multinucleate syncytia frequently contain over 20 ascospores.Key words: cell division cycle, cytokinesis, cytoskeleton, fission yeast.
Ceftazidime, gentamicin, and rifampicin, in combination, kill biofilms of mucoidPseudomonas aeruginosa
Authors: Ghani M. , Soothill J. S.
Published: February 2010

In continuous flow biofilm cultures in medium resembling cystic fibrosis bronchial secretions, Pseudomonas aeruginosa was not eradicated from biofilms by 1 week of treatment with high concentrations of ceftazidime and gentamicin, to which the strains were sensitive on conventional testing. The addition of rifampicin, which has little activity against the strains as measured by the minimum inhibitory concentration, led to the apparent elimination of the bacteria from the biofilms. The effect was not strain specific.Key words: Pseudomonas aeruginosa, biofilm, rifampicin.
Properties of NAD-dependent glutamate dehydrogenase from the tylosin producerStreptomyces fradiae
Authors: Nguyen Kien Trung , Nguyen Lieu Thi , Kopecký Jan , Běhal Vladislav
Published: February 2010

Glutamate dehydrogenase is an enzyme responsible for ammonium assimilation and glutamate catabolism in organisms. The tylosin producer Streptomyces fradiae possesses both NADP- and NAD-dependent glutamate dehydrogenases. The latter enzyme was purified 498-fold with a 7.5% recovery by a six-step protocol. The enzyme is composed of two subunits, each of Mr47 000, and could form active aggregates of four or eight subunits. Its activity was inactivated by alkaline pH or temperatures of −20 °C or above 40 °C. Activities assayed in the direction of oxidative deamination and reductive amination were optimal at pH 9.2 and 8.8, respectively, and at temperatures of 30–35 °C. No activity was found when NAD(H) was replaced with NADP(H). The Kmvalues were 32.2 mM for L-glutamate, 0.3 mM for NAD+, 3.4 mM for 2-ketoglutarate, 14.2 mM for NH4+, and 0.05 mM for NADH. Deamination activity was partially inhibited by adenyl nucleotides and several divalent cations; amination activity was not affected by the nucleotides but significantly inhibited by Cu2+or Ni2+.Key words: Streptomyces fradiae, NAD-dependent glutamate dehydrogenase, purification, properties.