bluuebunny/crossref_metadata_2025 huggingface dataset:
Characterization of albumin-binding properties of Peptostreptococcus magnus
Authors: Lämmler C. , Alaboudi A. , Hildebrand A.
Published: November 2009

A Peptostreptococcus magnus strain demonstrated binding activity for albumin preparations from humans, mice, and dogs, but not for rabbit or bovine albumin. The albumin binding site appeared to be heat stable and of protein nature. Treatment of P. magnus cells with trypsin under specified conditions enhanced this albumin binding. Electron micrographs and kinetic analyses revealed that this enhancement was the result of the removal of some cell wall associated proteins leading to a higher binding affinity without significant changes in binding site numbers. The albumin-binding proteins could be readily solu-bilized and purified by affinity chromatography. Upon gel electrophoresis the molecular mass of the albumin-binding proteins was estimated as 130 kilodaltons.Key words: Peptostreptococcus magnus, albumin binding, trypsin enhancement.
Isolation and characterization of a Pseudomonas aeruginosa bacteriophage with a very limited host range
Authors: Bigby Dianne , Kropinski Andrew M. B.
Published: November 2009

A Pseudomonas aeruginosa bacteriophage, [Formula: see text], with extremely limited host range has been isolated. It belongs to the virus family Podoviridae, morphological type C1, and possesses a head diameter of 45 nm. The phage has a buoyant density in CsCl of 1.516 g/cm3, and its mass is 45 × 106 daltons. The phage particles are composed of double-stranded DNA (49.9 mol% G + C; 42.4 kilobase pairs) and 11 structural proteins (66% by weight). The major head protein, P5, has a Mr of 34 500. The DNA is not cut by SalI or XhoI restriction endonucleases, but is cut by PvuII (1 site), KpnI and BglII (2 sites), PvuI (4 sites), BamHI (7 sites), EcoRI (9 sites), and HindIII (12 sites). A restriction endonuclease map is presented.Key words: Pseudomonas, bacteriophage, DNA, restriction map, structural proteins, electron microscopy.
Factors affecting the colonization of isolated rabbit intestinal epithelial cells by Vibrio cholerae 01 in vitro
Authors: Sasmal D. , Guhathakurta B. , Sikdar S. N. , Datta A.
Published: November 2009

The adhesive capability of Vibrio cholerae 01 strains to isolated rabbit intestinal epithelial cells was maximally expressed when the bacteria were grown in synthetic broth and was enhanced by the presence of Ca2+ in the growth media. N-Acetyl-D-glucosamine could inhibit the adhesion of the bacteria to rabbit intestinal epithelial cells as could lipopolysaccharide O-antigen from Vibrio cholerae 01 and lectin from Triticum vulgaris. Since the lipopolysaccharide is known to contain N-acetyl-D-glucosamine and because the lectin from Triticum vulgaris shows specificity for this sugar, it is probable that N-acetyl-D-glucosamine is actively involved in the adhesion of Vibrio cholerae 01 to isolated rabbit intestinal epithelial cells.Key words: adhesion, Vibrio cholerae 01, rabbit intestinal epithelial cell.
Effect of dimethyl sulfoxide on L-lysine production by a regulatory mutant of Brevibacterium flavum
Authors: Tang Ren Tian , Zhu Xiao Zhong , Gong C. S.
Published: November 2009

A regulatory mutant of Brevibacterium flavum was isolated. Mutant HA42 required L-homoserine for growth and was resistant to S-(2-aminoethyl)-L-cysteine. When grown in a glucose-containing medium, mutant HA42 produced higher levels of L-lysine than the wild type. Stimulation of lysine production was observed when a low concentration of dimethyl sulfoxide was added to the glucose medium during the course of fermentation. In the best case, the lysine yield increased by 166%. The stimulatory effect of dimethyl sulfoxide on lysine production was probably due to enhanced permeability of the organism's cell wall or membrane.Key words: lysine, fermentation, surfactant, permeability, dimethyl sulfoxide.
Application of gene probe methods for monitoring specific microbial populations in freshwater ecosystems
Authors: Steffan R. J. , Breen A. , Atlas R. M. , Sayler G. S.
Published: November 2009

Several gene probe methods were used to monitor specific microbial populations in freshwater microcosms. Detection methods included nonselective plating – colony hybridization, selective plating – colony hybridization, most probable number – filter hybridization, and community DNA extraction – dot blot hybridization. Tests were conducted in freshwater microcosms inoculated with a 4-chlorobiphenyl degrading Alcaligenes A5 or a 2,4,5-trichlorophenoxyacetic acid degrading Pseudomonas cepacia AC1100. Colony hybridization performed on colonies detected on a nonselective medium sometimes failed to detect both Alcaligenes A5 and P. cepacia AC1100 when the target populations comprised less than 0.1% of the total population, even though the target populations comprised less than 0.1% of the total population, even though the target populations were present at concentrations of greater than 104 viable cells/mL as indicated by other detection methods. Selective plating – colony hybridization, most probable number – filter hybridization, and dot blot hybridization using DNA extracted from the microbial community consistently indicated persistence of the added P. cepacia AC1100 in the microcosms. Although differing in their detection reliability and sensitivity, the various gene probe detection methods indicated persistence with a slow decline of both the Alcaligenes A5 and P. cepacia AC1100 over an 8-week period.Key words: DNA probes, environmental, bacteria, detection, biodegradation.
Coupling of the seasonal patterns of bacterioplankton and phytoplankton in a eutrophic lake
Authors: Marvalin O. , Aleya L. , Hartmann H. J. , Lazarek S.
Published: November 2009

Developments of bacterial and phytoplankton biomass were assessed during an annual sampling cycle in a eutrophic lake (Lake Aydat, France). Bacterial abundance, estimated by epifluorescence microscopy counting, varied from 0.61 to 12.72 × 106 cells/mL, confirming the eutrophic status attributed to this lake. Cellular densities were nearly homogeneously distributed in the water column. Mean values for bacterial abundance, obtained from three sampling depths (2, 7, and 14 m) were 3.70, 4.23, and 3.66 × 106 cells/mL. In the epilimnion, phytoplankton productivity and community composition, as well as temperature, appeared to control bacterial development. Bacterial biomass varied from 0.5 to 43.5 × 10−2 mg C/L. Mean values for the three sampling depths were 8.1, 10.1, and 9.1 × 10−2 mg C/L. Although bacterial biomass was significantly correlated with bacterial abundance, only 45 to 65% of its variation could be explained by abundance. Individual cell biovolumes varied up to sixfold, from 0.014 μm3 in spring and autumn to 0.090 μm3 in summer. The largest bacterial cells and the most elevated bacterial biomass were reached when bacteria were attached to phytoplankton or detrital organic matter, primarily during summer. Mucilaginous phytoplankton, such as Gomphosphaeria and Sphaerocystis, was found to be particularly good substrate available for the development of large and attached bacteria.Key words: eutrophic lake, bacterioplankton, phytoplankton, seasonal coupling, bacterial attachment.
Denitrification activity of phage types representative of two populations of indigenous Rhizobium meliloti
Authors: Chan Y.-K. , Barran L. R. , Bromfield E. S. P.
Published: November 2009

Isolates of Rhizobium meliloti from indigenous populations at two sites were previously characterized according to phage sensitivity. Isolates representative of the 55 and 65 phage types comprising these two populations, respectively, were tested for denitrification activity with nitrate or nitrite as substrate. Fifty-seven of 120 isolates were capable of denitrification with activities varying considerably between phage types. Only one isolate was able to denitrify nitrite but not nitrate, indicating the presence of a truncated denitrification pathway. Each of five phage types showed variation in denitrification ability between isolates from different sites, indicating possible adaptation of indigenous R. meliloti to their respective environments. The estimated frequency of occurrence of denitrifiers in the two indigenous populations of R. meliloti (9 and 13%) differed significantly between sites with and without a previous history of Medicago sativa cultivation, respectively.Key words: Rhizobium, denitrification, populations, phage.
Effect of mineral substrate hardness on the population density of epilithic microorganisms in two Ontario rivers
Authors: Ferris F. G. , Fyfe W. S. , Witten T. , Schultze S. , Beveridge T. J.
Published: November 2009

Adherent epilithic microorganisms recovered from rocks submerged 10 to 20 cm in two different rivers were examined by electron microscopy and enumerated after dispersion in M-9 salts by viable plate counts. Bacterial cells concentrated in microcolonies were often observed attached to the surface of algae, cyanobacteria, and organic detritus. This structured communal mode of growth was common among epilithic microbial communities of different rock types. However, counts of heterotrophic bacteria from limestone (106 to 107 cfu/cm2) were 10- to 100-fold greater than corresponding values from granite, gabbro, rhyolite, basalt, and quartz. Cyanobacteria and algae were an order of magnitude less abundant compared with their bacterial counterparts. These variations in population densities of epilithic microorganisms present on different rocks were inversely related to mineral substrate hardness.Key words: epilithic microorganisms, mineral hardness.
Detection of bacterial cell wall hydrolases after denaturing polyacrylamide gel electrophoresis
Authors: Leclerc Denis , Asselin Alain
Published: November 2009

Cell walls from various Gram-positive bacteria were incorporated at a concentration of 0.2% (w/v) into polyacrylamide gels as a substrate for detection of cell wall hydrolases. Bacterial extracts from crude cell wall preparations were denatured with sodium dodecyl sulfate and 2-mercaptoethanol and subjected to denaturing polyacrylamide gel electrophoresis in gels containing bacterial cell walls. After renaturation in the presence of purified and buffered 1% (v/v) Triton X-100, cell wall hydrolases were visualized as clear lytic zones against the opaque cell wall background. One to fifteen bands with lytic activity could be detected, depending on bacterial extracts and on the nature of the cell walls incorporated into gels. Crude cell wall extracts were the best source of cell wall hydrolases from various Gram-positive bacteria such as Clostridium perfringens (15 bands), Micrococcus luteus (1 band), Bacillus megaterium (4 bands), Bacillus sp. (6 bands), B. cereus (3 bands), B. subtilis (7 bands), Staphylococcus aureus (13 bands), Streptococcus faecalis (3 bands), and Strep. pyogenes (5 bands). Molecular masses of cell wall hydrolases ranged from 17 to 114.6 kDa. Lytic activities against cell walls of Corynebacterium sepedonicum (Clavibacter michiganense pv. sepedonicum) could be shown with the cell wall extracts of Strep. pyogenes (45.7 kDa), Strep. faecalis (67 kDa), B. megaterium (67 kDa), and Staph. aureus (67 kDa).Key words: autolysins, electrophoresis, hydrolases, muramidases, peptidoglycan.
Acetate, propionate, butyrate, glucose, and sucrose as carbon sources for denitrifying bacteria in soil
Authors: Paul J. W. , Beauchamp E. G. , Trevors J. T.
Published: November 2009

Acetate, propionate, and butyrate were compared with glucose and sucrose as carbon substrates for denitrifying bacterial activity in an agricultural soil. After 216 h of incubation in the laboratory, the denitrification capacity per mole of carbon differed in the order sucrose < glucose < acetate < propionate < butyrate. In the acetate-, propionate-, and butyrate-amended soil, the denitrification activity was positively related to the amount of electrons available per mole of carbon. The low denitrification activity in soil amended with glucose was probably caused by competition for carbon between denitrifying and fermentative bacterial populations. Significant production of acetate occurred in soil amended with both glucose and nitrate, suggesting that denitrification and fermentation could occur simultaneously under anaerobic conditions.Key words: Short-chain fatty acids, denitrification, carbon sources, metabolic pathways, fermentation.
L-Alanine and inosine enhancement of glucose triggering in Bacillus megaterium spores
Authors: Bédard Jean , Lefebvre Gerald M.
Published: November 2009

Both rate and extent of germination of Bacillus megaterium 14581 (ATCC) spores are considerably augmented when L-alanine and inosine are added to the glucose commonly used as triggering agent for this strain. This enhancement does not arise from heterogeneity in germination requirements of the dormant spore, but is rather a consequence of the combined action of glucose and either or both of the added reagents on a sizeable fraction of spores unable to germinate in glucose alone. Nearly half of the spores that eventually germinate in the mixture of germinants used are either triggered by glucose or are sensitized by it to subsequent triggering by L-alanine and inosine in the first 10 s of imbibition. For a good number of these spores, then, triggering consists of a sequence of separable events.Key words: Bacillus megaterium, spore germination, L-alanine, inosine, glucose.
Isolation and characterization of marine and salt pond halophylic bdellovibrios
Authors: Amat A. Sánchez , Torrella F.
Published: November 2009

A method to enrich and isolate bdellovibrios from marine waters and solar salt evaporation ponds of a salinity up to 15.5% has been developed. The method promotes growth of gram-negative autochthonous bacteria followed by bdellovibrios that prey on them. Various Vibrio and Pseudomonas strains have been used to reveal Bdellovibrio plaques and in no case have bacteriophages interfered with the isolation technique. A total of 13 strains have been characterized by electron microscopy, host range, cytochrome spectra, and capacity to grow at different salt concentrations. All isolates show typical Bdellovibrio morphology and life cycle. Little differences could be found among the Bdellovibrio strains according to host range patterns with the exception of Bdellovibrio BS42 and BS43 that were unable to lyse various of the hosts used. These two Bdellovibrio strains differed too from the others in the cytochrome spectra of whole cell suspensions (α and β bands of the cytochrome c). All of the bdellovibrios isolated showed the typical bands of cytochromes a and c, and in some cases, the peak of cytochrome b could also be discerned. The Soret band has proved to be of great value to distinguish halophylic from freshwater bdellovibrios. The saline growth range found in this study is broader than the one described previously for marine bdellovibrios (1–6%). Some of the strains isolated from seawaters or from salt ponds could grow from 1 to 15% total salts salinity. The growth capacity at the highest salinities depends to a great extent on the proportion of salts in the medium. A compensated saline solution supports better Bdellovibrio proliferation than a solution where only the NaCl concentration has been increased. Tolerance to salinity divides the isolated bdellovibrios into two groups: a low salinity group of strains of marine origin able to grow at a salinity of 1% total salts, but not in freshwater media nor above 12% total salts, and a high salinity group isolated from solar evaporation ponds, with strains able to multiply in liquid media up to a salinity of 15% total salts, but unable to grow at a salinity of 1%. These results broaden the habitat of Bdellovibrio in saline waters of marine origin up to salinities of 15%, as well as indicate further diversity in this group of bacterial predators.Key words: halophylic Bdellovibrio, salterns, marine bacteria.
Genetic mapping of katB, a locus that affects catalase 2 levels in Bacillus subtilis
Authors: Loewen Peter C.
Published: November 2009

A locus affecting the synthesis of spore-specific catalase 2 in Bacillus subtilis was mapped using two- and three-factor trans-ductional crosses at 342 °between hsrE and iol. It was named katB. Strains lacking catalase 2 remained sporulation proficient, but blockage of sporulation at stage IV or earlier affected the electrophoretic mobility of the native enzyme.Key words: Bacillus subtilis, catalase 2, katB, sporulation, mapping.
ATP-related specific heterotrophic activity in petroleum contaminated and uncontaminated groundwaters
Authors: Jensen Bjørn K.
Published: November 2009

Bacterial numbers, ATP content, heterotrophic potentials, and thymidine incorporation were determined for petroleum contaminated and uncontaminated groundwaters. ATP measurements and cell counts gave variations of a factor of 7 in values among the sites. The acridine orange direct counting yielded counts 2 to 3 orders of magnitude higher than the plate counts and counts 1 to 2 orders of magnitude higher than counts given by the ATP measurement using a conversion factor of 10−6 ng ATP/cell. Mean Vmax values for 14C-labled glucose, acetate, and naphthalene were 0.59, 0.17, and 1.14 μg ∙ L−1 ∙ h−1, respectively. Naphthalene was only used as substrate in the contaminated samples. Acetate and naphthalene showed fairly good correlations to ATP contents, 0.94 and 0.95, respectively, as well as with tritiated thymidine incorporation rates, r = 0.94. Vmax specific activity indices (SAI) based on ATP content showed very little variation for the selected groundwaters compared with SAI values reported earlier for groundwaters.Key words: groundwater, heterotrophic potential, tritiated thymidine incorporation, ATP.
The isolation, from a prosthetic device site, of a rare bacterium belonging to CDC enteric group 58
Authors: Dalton Maurice T. , Bezanson Gregory S.
Published: November 2009

We describe a gram-negative bacterium that belongs to a group tentatively classified at the Centres for Disease Control as CDC Enteric Group 58. It was recovered from bone at the site of internal fixation plates in a left forearm following a traumatic fracture. This is a rare isolate and, in this case, it was not associated with systemic signs of infection. Biochemical identification of the isolate is described.Key words: enteric group CDC58, osteomyelitis, internal fixation A.O. plate.
Modification de la structure des enveloppes et du contenu en proteins d'Escherichia coli en survie dans l'eau de mer
Authors: Gauthier Michel J. , Thomas Pierre , Munro Patrick M.
Published: November 2009

A toxigenic strain of Escherichia coli displayed important structural modifications when placed in seawater which naturally lacked nutritive elements, as observed by electron microscopy. These include cell wall and cell body distortion, modification of the membranes, central segregation of the chromosome, and retraction of the cytoplasm. These modifications were accompanied by a decrease in cell protein content of approximately 40%. Certain cytoplasmic membrane proteins were lost, and new ones appeared. The development of these changes was considerably slower in cells that had previously been grown in a seawater medium. This suggests that osmotic regulation mechanisms, which enable E. coli to survive much longer in marine conditions, may have a protective influence.Key words: Escherichia coli, structure, envelopes, survival, seawater.[Journal translation]
Unequal accumulation of 26S and 17S RNAs in ribosomes during spore germination in Dictyostelium discoideum
Authors: Ramagopal S.
Published: November 2009

Ribosome synthesis was studied in spores at the swelling stage and compared with freshly emerged and logarithmically growing vegetative amoebae. During the swelling stage of spore germination, ribosome synthesis was abnormal. Newly made ribosomes accumulated unequal amounts of 26S and 17S rRNAs. The stoichiometric ratio 26S:17S was 0.5 in swelling spores, compared with 0.9 in amoebae. The relative level of pre-rRNA persisting in the nucleus was apparently 2- to 3-fold higher in swelling spores than in amoebae. All of the known ribosomal proteins, except for a few, were made during the swelling stage and were associated with the newly made ribosomes in expected amounts. Analysis of the 2′-O-methyl ribose content in the newly made rRNAs suggests that methylation was defective in swelling spores. Compared with growing amoebae, the methyl content was 30 and 64% less in 26S and 17S RNAs from the swelling stage, respectively. It is suggested that undermethylation could be partly responsible for the differential accumulation of newly made 26S and 17S RNAs during the early stages of spore germination in Dictyostelium discoideum.Key words: cellular slime mold, rRNA synthesis, ribosomal proteins, methylation, cell differentiation.
Fate of Tn5 mutants of root growth-inhibiting Pseudomonas sp. in intact soil-core microcosms
Authors: Fredrickson Jim K. , Bentjen S. A. , Bolton Jr. H. , Li S. W. , Voris P. Van
Published: November 2009

Transposon Tn5 mutants of a wheat root growth-inhibiting nonfluorescent Pseudomonas sp. were inoculated into intact soil-core microcosms to determine the utility of intact soil cores for evaluating the fate and transport of microorganisms in agricultural ecosystems. Transposon Tn5 mutants that no longer produced a toxin (tox−) to inhibit the growth of wheat roots or Escherichia coli, and Tn5 mutants that retained the toxin-producing ability (tox+), were inoculated into plow layer soil of intact soil-core microcosms. Spring wheat was then planted, and Tn5 mutant populations were enumerated over time in the bulk soil and with depth in the bulk soil, rhizosphere, and rhizoplane. Pseudomonas sp. Tn5 mutants were observed in soil-core leachates and in the gut of earthworms introduced into microcosms. The population of the introduced Tn5 mutants declined over time in the surface soil, but colonized the wheat rhizosphere and rhizoplane throughout the 60-cm soil-core depth. Rhizoplane populations of the tox+ Tn5 mutants were higher than populations of tox− mutants at the seedling stage, but significant differences were not observed at later stages of plant growth or in the rhizosphere. The Tn5 mutants were transported through the core with percolating water and were present in the gut of earthworms. Intact soil-core microcosms could be useful in assessing the fate and transport of genetically engineered microorganisms in the environment prior to field testing.Key words: microcosms, Pseudomonas sp., rhizosphere, soil, Tn5.
Bacterial growth kinetics: modelling and evaluation of two-compartment radioassay
Authors: Boonkitticharoen Vipa , Ehrhardt James C. , Kirchner Peter T.
Published: November 2009

Quantitative measurements of bacterial growth may be made using a radioassay technique. This method measures, by scintillation counting, the 14CO2 derived from die bacterial metabolism of a 14C-labeled substrate. Mathematical growth models may serve as reliable tools for estimation of the generation rate constant (or slope of the growth curve) and provide a basis for evaluating assay performance. Two models, i.e., exponential and logistic, are proposed. Both models yielded an accurate fit to the data from radioactive measurement of bacterial growth. The exponential model yielded high precision values of the generation rate constant, with an average relative standard deviation of 1.2%. Under most conditions the assay demonstrated no changes in the slopes of growth curves when the number of bacteria per inoculation was changed. However, the radiometric assay by scintillation method had a growth-inhibiting effect on a few strains of bacteria. The source of this problem was thought to be hypersensitivity to trace amounts of toluene remaining on the detector.Key words: bacterial growth modelling.
Flagellar antibody stimulated opsonophagocytosis of Pseudomonas aeruginosa associated with response to either a- or b-type flagellar antigen
Authors: Anderson Tina R. , Montie Thomas C.
Published: November 2009

Pseudomonas aeruginosa exhibit one of two flagella types: a homogeneous b type, with molecular weight of 53 000, or a heterogeneous a type (subtypes a0, a1, a2, a3, and a4), with molecular weights ranging from 45 000 to 52 000. Pseudomonas aeruginosa flagellar antiserum was shown to promote uptake of radiolabeled bacteria by mouse polymorphonuclear leukocytes. Bacteria were detected directly associated with washed leukocytes and visualized, by electron microscopy, internalized in polymorphonuclear leukocytes. Phagocytosis was specific for the flagella type (a or b) in that homologous flagella serum enhanced uptake three to four times greater than heterologous serum or normal rabbit serum. An a-type antiserum was shown to enhance phagocytosis of four different a-type strains with varying subantigen types, indicating the presence of a common cross-reactive a0 antigen in this flagella type. Phagocytic killing of internalized bacteria was not seen with the addition of only flagellar antiserum.Key words: flagella, Pseudomonas aeruginosa, phagocytosis, opsonic, polymorphonuclear leukocytes.
Identification of a chromosomal region required for biosynthesis of the phytotoxin coronatine by Pseudomonas syringae pv. tomato
Authors: Moore R. A. , Starratt A. N. , Ma S.-W. , Morris V. L. , Cuppels D. A.
Published: November 2009

Pseudomonas syringae pv. tomato produces the chlorosis-inducing phytotoxin coronatine. Five of 3700 (0.13%) kanamycin-resistant mutants generated by random Tn5 mutagenesis were unable to synthesize this toxin. Clone pEC18, isolated from a cosmid pLAFR1 library of wild-type P. syringae pv. tomato DC3000 genomic DNA, complemented four of the mutants. Restriction enzyme analysis of pEC18 and corresponding clones from the four mutants indicated that the Tn5 insertion sites of these four mutants spanned a 19-kb region of DC3000 genomic DNA. Complementation tests with subclones of pEC18 confirmed the relative locations of the Tn5 insertions. Because pEC18 did not complement all five mutants or confer the ability to produce toxin on nonproducing P. syringae pathovars, sequences outside this cloned region must also be involved in toxin synthesis. As demonstrated by Southern blot analysis, this cloned region was not on the 68-kb indigenous plasmid of DC3000. The only P. syringae pathovars with DNA homologous to sequences within the coronatine gene cluster were the coronatine producers P. syringae pv. tomato, P. syringae pv. atropurpurea, and P. syringae pv. glycinea. Since the hybridization patterns of these toxin producers were identical, this locus is highly conserved and appears crucial to the synthesis of coronatine.Key words: coronatine, phytotoxin mutants, Pseudomonas syringae pv. tomato.
Respiratory differences associated with culture aeration in Azotobacter vinelandii
Authors: Peterson Jay B.
Published: November 2009

Respiratory oxygen uptake of nitrogen-fixing Azotobacter vinelandii cells was altered by culturing at different levels of culture agitation (aeration). Cells were grown at low agitation or moderate agitation and with three different carbon substrates. The low-agitation cultures had much lower dissolved-oxygen concentrations than moderate-agitation cultures at the stage of growth at which they were studied. The respiration systems of cells from the moderate-agitation cultures had lower apparent affinities (higher Ks (O2) values) for oxygen than cells grown at low agitation. The higher Ks (O2)) values were dependent on the presence of Ca2+ and (or) Mg2+ in the medium. In low-agitation cultures, the oxygen concentrations were below the Ks (O2 values and the respiration rates in the cultures were therefore well below the maximal respiration (Vmax) rates. The oxygen concentrations in moderate-agitation cultures were above the Ks (O2) values and the culture respiration rates were much higher. The culture oxygen concentration relative to the Ks (O2) had a much greater effect on culture respiration rate than did the Vmax. It is proposed that changes in the respiration system resulting from culture agitation (aeration) reflect an "oxygen-sensing mechanism" that regulates respiration. This would provide at least a partial explanation for the increased respiration rates with increased culture oxygen concentration in A. vinelandii.Key words: Azotobacter, oxygen, respiration, nitrogen fixation.
DNA relatedness of oil-field isolates of Shewanella putrefaciens
Authors: Semple Kathleen M. , Doran James L. , Westlake D. W. S.
Published: November 2009

Classification of several oil-field isolates of Shewanella putrefaciens was assessed by nucleic acid hybridization techniques. The results of DNA – DNA hybridization analysis generally confirmed the phenetic characterization of these isolates and supported the classification of oil-field isolates of S. putrefaciens groups 1, 3, and 4. However, two group 2 isolates were considered to be mistakenly classified. Strain ESSO 1-1 appeared to belong to group 3, a result which was supported by the pattern of 5S rRNA hybridization to restriction digests of genomic DNA, and strain 213 appeared to be a member of group 1. Several of the oil-field strains of S. putrefaciens were found to possess indigenous plasmids, a feature which was not shared by the other strains of S. putrefaciens examined. This study indicates mat these oil-field isolates were more closely related to strains of S. putrefaciens isolated from various environments than to the other Shewanella species (S. benthica and S. hanedai) that shared the important metabolic characteristics of iron reduction and sulfide production from thiosulfate. There was very little genetic relationship found between Shewanella spp. and the other species studied.Key words: Shewanella putrefaciens, DNA relatedness, oil-field iron reduction, sulfide production, taxonomy.
Factors affecting adsorption of Azospirillum brasilense Cd to root hairs as compared with root surface of wheat
Authors: Bashan Yoav , Levanony Hanna
Published: November 2009

Electron microscopy of wheat (Triticum aestivum) roots inoculated with Azospirillum brasilense Cd revealed massive adsorption of bacterial cells to the root surface and less adsorption to root hairs. Quantitative analysis of A. brasilense Cd adsorption to root surface and to root hairs, confirmed qualitatively by light microscopy observations, revealed a bacterial adsorption ratio of 5 (+2): 1 (root surface: root hairs). Extreme bacterial adsorption ratios were recorded when bacteria were previously grown in the presence of KNO3 (27:1) or when bacterial cells were inoculated under hydroponic plant growth conditions (80:1). Adsorption of A. brasilense Cd to roots was directly related to the bacterial growth phase, with logarithmic phase cultures demonstrating a greater adsorption than stationary phase cultures. Adsorption to root hairs was dependent mainly on the number of root hairs developed under certain growth conditions. When very few root hairs had developed, most of the bacterial cells were adsorbed to the root surface. Factors such as starvation, bacteria grown in culture in the presence of KNO3, addition of several nutrients, and protease or NaEDTA treatments of bacterial cells before the adsorption assay decreased bacterial adsorption to root hairs. Other factors such as microaerophilic growth conditions, addition of several bacterial chemoattractants, and cellulase-treated root hairs enhanced bacterial adsorption. It is proposed that although A. brasilense Cd adsorbed to every part of the root system, more cells adsorbed to the root surface of wheat than to the root hairs.Key words: associative bacteria, Azospirillum, bacterial adsorption, beneficial bacteria, rhizosphere bacteria, root-hair colonization.
Survival of Pseudomonas fluorescens containing plasmids RP4 or pRK2501 and plasmid stability after introduction into two soils of different texture
Authors: Elsas J. D. Van , Trevors J. T. , Overbeek L. S. Van , Starodub M. E.
Published: November 2009

Survival of Pseudomonas fluorescens R2f containing either the conjugative plasmid RP4 or the nonconjugative plasmid pRK2501, and stability of the plasmids were studied in two soils, Ede loamy sand and Guelph loam, and in extracts prepared from these soils. In sterile soils, the introduced bacterial populations initially increased and then remained stable over a 47-day period. The presence of wheat roots did not significantly influence bacterial numbers in Guelph loam, whereas a slight increase occurred in Ede loamy sand. In Guelph loam, both plasmids were stably maintained in the introduced populations, but in Ede loamy sand substantial plasmid loss was observed. The presence of added phosphate in Ede loamy sand enhanced plasmid maintenance in the introduced R2f population. In nonsterile Guelph loam, a slow decline in the introduced populations was noted, regardless of plasmid type, whereas in Ede loamy sand the decline was more rapid. There was no detectable effect of plasmid type on host survival. Both plasmids RP4 and pRK2501 remained present in the R2f populations in these soils. The results obtained with sterile soil extracts substantiated the data on plasmid loss in both soils; both plasmids were rather unstable during starvation in minimal medium. The results indicated the absence of an effect of plasmid type on host survival. Soil type significantly affected host survival and plasmid maintenance, and higher survival and stability were observed in the heavier-textured Guelph loam.Key words: survival, plasmid stability, Pseudomonas spp., soil, microcosms.
Application of two-dimensional protein analysis for strain fingerprinting and mutant analysis of Azospirillum species
Authors: Mot René De , Vanderleyden Jos
Published: November 2009

Phenol-extracted total proteins from wild-type and mutant strains of Azospirillum brasilense and A. lipoferum were subjected to two-dimensional polyacrylamide gel electrophoresis. The protein patterns of both species could be readily distinguished by specific configurations of a limited number of spots. The resolving power of the technique allowed its application for strain fingerprinting. Thus, near-identity of A. brasilense strains Sp7 and Cd was demonstrated. In addition, minor changes in protein profiles resulting from spontaneous, chemically induced, or transposon-mediated mutations in the A. brasilense genome were evidenced. For a nitrate reductase negative mutant of strain Sp245 and a Sp7 mutant affected in exopolysaccharide synthesis, production of a truncated protein was involved. In Tn5-generated mutants, a gene dosage effect for the transposon-encoded neomycine phosphotransferase was observed.Key words: Azospirillum, two-dimensional protein analysis, fingerprinting.
Effect of pH and temperature on the infectivity of human coronavirus 229E
Authors: Lamarre Alain , Talbot Pierre J.
Published: November 2009

The stability of human coronavirus 229E infectivity was maximum at pH 6.0 when incubated at either 4 or 33 °C. However, the influence of pH was more pronounced at 33 °C. Viral infectivity was completely lost after a 14-day incubation period at 22, 33, or 37 °C but remained relatively constant at 4 °C for the same length of time. Finally, the infectious titer did not show any significant reduction when subjected to 25 cycles of thawing and freezing. These studies will contribute to optimize virus growth and storage conditions, which will facilitate the molecular characterization of this important pathogen.Key words: coronavirus, pH, temperature, infectivity, human coronavirus.
Diazotroph establishment and maintenance in the Sorghum – Glomus – Azospirillum association
Authors: Pacovsky Raymond S.
Published: November 2009

Sorghum (Sorghum bicolor (L.) Moench cv. Bok 8) plants were grown in either a high peat or a low organic matter substrate and inoculated with a pigmented strain of Azospirillum brasilense (Cd). Half of the plants were also inoculated with the vesicular–arbuscular mycorrhizal (VAM) fungus Glomus etunicatum, while the remaining plants were fertilized with levels of phosphorus that had been found to be comparable to P input resulting from mycorrhizal colonization. Plants were harvested 1, 3, 5, and 7 weeks postemergence. Total plant dry weight was statistically similar (p > 0.05) between the two treatments for each substrate at all harvests. For each substrate, Azospirillum counts per gram of root were significantly (p < 0.05) higher in mycorrhizal roots at all harvests than in P-fertilized roots, and also higher in the high peat substrate compared with the low organic matter substrate. The ratio of the total number of inoculated A. brasilense cells in the Glomus-colonized compared to the P-fertilized roots was positively and significantly correlated (r = 0.81; p < 0.05) with % VAM colonization. Colonization of sorghum roots by G. etunicatum thus enhanced the establishment and persistence of A. brasilense in the endorhizosphere of sorghum.Key words: Azospirillum brasilense, endomycorrhizae, Glomus etunicatum, rhizosphere, Sorghum bicolor.
Effet cytotoxique in vitro et chez l'insecte hôte des destruxines, toxines cyclodepsipeptidiques produites par le champignon entomopathogène Metarhizium anisopliae
Authors: Vey A. , Quiot J. M.
Published: November 2009

The cytotoxic effect of the cyclodepsipeptide mycotoxins of the group of destruxins (DA, DB, DE) has been investigated in the insect host, Galleria mellonella, and in invertebrate cell cultures, mainly at the ultrastructural level. The strong effect of DE is characterized by changes in the morphology of the cells, and the development of structural alterations at the nuclear and cytoplasmic levels. The major lesions observed even at low doses consist in a pycnotic evolution of the nucleus and a degradation of mitochondria, while the rough endoplasmic reticulum and the ribosomes are also impaired. In the host, the main organs and tissues attacked by DE are the midgut, the malpighian tubules, and the circulating hemocytes. A comparative study of the effect of DE, DA, and DB has revealed a specificity in the cytotoxic action of these compounds. The following classification has been observed in the efficiency of the molecules: DE > DA > DB. These results allow a better understanding of the role of peptidic mycotoxins in the pathogenesis of fungal infections. They also reveal similarities with the action of other mycotoxins, and constitute a valuable foundation for studies on the molecular aspects of the mechanism of action of destruxins.Key words: mycotoxin, destruxin, mode of action, cytotoxic effect, in vitro toxicity.
Influence of far-ultraviolet radiation on the permeability of the outer membrane of Escherichia coli
Authors: Mody Rustom , Krishnamurthy Sudha , Dave Prafulla
Published: November 2009

Far-ultraviolet radiation (254 nm) at a dose of 10, 20, and 30 J/m2 was found to disrupt the outer membrane permeability barrier of Escherichia coli to various antibiotics, dyes, and detergents. The degree of sensitization to these agents was proportional to the radiation dose. The irradiated cells showed a significant increase in the sensitivity of hydrophilic antibiotics (ampicillin, carbenicillin, penicillin), whereas much less sensitization was found towards hydrophobic probes (kanamycin, erythromycin, rifamycin SV, crystal violet, phenol, novobiocin) and detergents (dodecyl sulfate, bile salt, Triton X-100). The biochemical data and ultrastructural analysis of the outer membrane by freeze-etching have shown that the increase in phospholipid:protein ratio after irradiation had changed the architecture of the outer membrane from a highly asymmetric bilayer structure with densely packed lipopolysaccharide–protein particles on the outer half, to one predominantly exhibiting smooth phospholipid bilayer characteristics. The structure, composition, and barrier function of the outer membrane were restored to normal within 3 h of postirradiation incubation in nonproliferative medium. During this period, the acquisition of resistance towards a hydrophilic antibiotic (ampicillin) was faster than that for a hydrophobic agent (phenol).Key words: far-ultraviolet, outer membrane, permeability, disorganization, recovery.
Brown pigmentation in Serratia marcescens cultures associated with tyrosine metabolism
Authors: Trias Joaquim , Viñas Miquel , Guinea Jesus , Lorèn José G.
Published: November 2009

Serratia marcescens produced a brown pigment when grown in minimal medium in the presence of tyrosine and high concentrations of copper(II) ion. The pigment was not related to the melanin pigments, but was similar to the pigment produced by autooxidation and polymerization of 3,4-dihydroxyphenylacetate, which is synthesized in S. marcescens from tyrosine through the 3,4-dihydroxyphenylacetate catabolic pathway. The enzymes of this pathway were induced under pigment production conditions; however, 3,4-dihydroxyphenylacetate 2,3-dioxygenase remained at low activity levels, permitting the accumulation and excretion of the substrate. Mutants unable to use tyrosine as a sole carbon and energy source were able to produce brown pigments only if the step blocked by the mutation was after the synthesis of 3,4-dihydroxyphenylacetate. The ability to produce brown pigments was common to all the S. marcescens strains tested.Key words: brown pigment, 3,4-dihydroxyphenylacetate 2,3-dioxygenase, Serratia marcescens, tyrosine, aromatic amino acid catabolism.
Bactericidal effect of lactoferrin on Legionella pneumophila: effect of the physiological state of the organism
Authors: Bortner Carol A. , Arnold Roland R. , Miller Richard D.
Published: November 2009

Lactoferrin has been previously shown to be bactericidal for Legionella pneumophila. The current study showed that CaCl2, Mg(NO3)2, and MgCl2, but not NaCl, blocked killing. Activity was pH dependent with the greatest activity at 5.0. Sensitivity of the organism was dramatically affected by the growth conditions. Log phase 12 h, broth-grown cells were most sensitive, with older cultures becoming more resistant. Plate-grown cells were completely resistant. Lactoferrin binding, as detected by immunofluorescence microscopy, was temperature dependent (no binding at 4 °C), but was independent of killing.Key words: Legionella pneumophila, lactoferrin, mucosal proteins.
Revival of saprotrophic and mycorrhizal basidiomycete cultures from cold storage in sterile water
Authors: Richter Dana L. , Bruhn Johann N.
Published: November 2009

Vegetatively colonized agar cores of 135 basidiomycete isolates, representing 83 species in 38 genera, were stored at 5 °C in tubes of sterile distilled water. Viability, based on growth at room temperature, was determined after storage periods ranging from 3 to 48 months. Thirty-seven isolates of saprotrophic fungi represented 32 species of 22 genera; 98 isolates of mycorrhizal fungi represented 51 species of 16 genera. Most isolates of saprotrophic species were viable, even after the most extended periods of storage. Many isolates of mycorrhizal species demonstrated lower viability, especially over longer periods of storage. Among our isolates of mycorrhizal fungi, Laccaria bicolor (seven isolates) and Laccaria laccata (nine isolates) appeared well suited to this method of long-term storage, whereas Scleroderma species (22 isolates) did not.Key words: culture maintenance, culture viability, fungal preservation, long-term storage, vegetative cultures.
Biochemical and genetic studies with arginine and proline auxotrophs of Neisseria gonorrhoeae
Authors: Picard F. J. , Dillon J. R.
Published: November 2009

The prevalence of specific arginine biosynthesis gene defects was studied for 319 arginine-requiring clinical isolates of Neisseria gonorrhoeae by using the ability of the strains to utilize intermediates of arginine biosynthesis. Only 11 % of the uracil-requiring strains defective in the carbamylation of ornithine to yield citrulline had a defective carbamoylphosphate synthetase gene (carAB). Strains defective in carAB were of auxotype CUH. The other strains (89%) having a dual requirement for citrulline and uracil, which were mostly of auxotype PCU, were defective in the ornithine transcarbamoylase gene (argF). Over 90% of the strains were defective either in argJ (174 strains) or in argF (126 strains). Three argininosuccinate-requiring strains (i.e., defective in argG) of auxotype PAU were identified. Some of the arginine auxotrophs of N. gonorrhoeae defective in carAB, argJ, argF, or argG were complemented by genetic transformation with DNA from recombinant bacteriophages carrying characterized gonococcal arginine biosynthesis genes. Gene defects in proA (five strains) and in proB (six strains) were identified by gonococcal transformation assays with recombinant bacteriophages or plasmids carrying proline biosynthesis genes from N. gonorrhoeae. None of the 11 proline-requiring strains tested was defective in proC.Key words: Neisseria gonorrhoeae, arginine biosynthesis, proline biosynthesis, gene defect, marker rescue.
Ultrastructural examination of Gibberella fujikuroi mycelia: effect of immobilization in calcium alginate beads
Authors: Saucedo José Edmundo Nava , Barbotin Jean-Noël , Velut Martine , Thomas Daniel
Published: November 2009

Ultrastructural examination of free and calcium alginate immobilized Gibberella fujikuroi mycelia showed that in addition to the changes occurring during the transition phase from primary to secondary metabolism, there are several alterations in the ultrastructure of hyphae as a response to microenvironmental changes owing to immobilization constraints. Internal changes included (i) the presence of large glyoxisomelike bodies and of active vesicle-generating systems, which appeared as cloudy structures in electron micrographs; (ii) the formation of endocells, resulting in hyphae with up to three cell walls and the concomitant accumulation of secondary metabolites, mainly pigments, in peripheral cell compartments; and (iii) the progressive development of autophagic vacuoles involved in the turnover of cell constituents.Key words: Gibberella fujikuroi, immobilized fungi, alginate entrapment, ultrastructure modification, immobilization.
Effectiveness and competition for nodulation of Vigna unguiculata and Macroptilium atropurpureum with Bradyrhizobium from Parasponia
Authors: Trinick M. J. , Hadobas P. A.
Published: November 2009

Strains of Bradyrhizobium sp., from Parasponia and from legumes, were tested in Leonard jars and enclosed plant tubes for their effectiveness at nitrogen fixation and competitiveness for nodulation of Vigna unguiculata and Macroptilium atropurpureum. With the exception of CP283, strains of Bradyrhizobium from Parasponia were ineffective in fixing nitrogen on both legumes; on V. unguiculata, they were poor competitors with strains from legumes of similar host effectiveness, only occupying 29 of 1189 nodules examined. On M. atropurpureum. the highly effective strain CP283 was a strong competitor with equally effective legume strains. Dual occupancy of nodules was common in competition studies on M. atropurpureum, but not with V. unguiculata as the host plant. The time taken to nodulate the legume host did not appear to be a factor influencing competition for nodulation. Of the strains isolated from Parasponia, only strain CP283 had attributes common to both groups of Bradyrhizobium. The poor compatibility of Bradyrhizobium strains from Parasponia with the two tested legumes further supports their inclusion in a group separate from the Bradyrhizobium strains isolated from legumes.Key words: Parasponia, Bradyrhizobium, competition, nitrogen fixation, specificity, Macroptilium, Vigna.
PASSAGE OF RADIATION THROUGH WORMHOLES
Authors: DOROSHKEVICH ANDREY , HANSEN JAKOB , NOVIKOV IGOR , SHATSKIY ALEXANDER
Published: November 2009

We investigate numerically the process of the passage of a radiation pulse through a wormhole and the subsequent evolution of the wormhole that is caused by the gravitational action of this pulse. The initial static wormhole is modeled by a spherically symmetrical solution with zero mass. The radiation pulses are modeled by spherically symmetrical shells of self-gravitating massless scalar fields. We demonstrate that the compact signal propagates through the wormhole and investigate the dynamics of the fields in this process for both cases: collapse of the wormhole into the black hole and for the expanding wormhole.