bluuebunny/crossref_metadata_2025 huggingface dataset:
Transfer and expression of the genetic determinants for O and K antigen synthesis in Escherichia coli O9:K(A)30 and Klebsiella sp. Ol:K20, in Escherichia coli K12
Authors: Laakso Dayle H. , Homonylo Mary K. , Wilmot Sheila J. , Whitfield Chris
Published: May 2010

Escherichia coli serotype O9:K(A)30 and Klebsiella O1:K20 produce thermostable capsular polysaccharides or K antigens, which are chemically and serologically indistinguishable. Plasmid pULB113 (RP4::mini-Mu) has been used to mediate chromosomal transfer from E. coli O9:K30 and Klebsiella O1:K20 to a multiply marked, unencapsulated, E. coli K12 recipient. Analysis of the cell surface antigens of the transconjugants confirmed previous reports that the genetic determinants for the E. coli K(A) antigens are located near the his and rfb (O antigen) loci on the E. coli linkage map. The Klebsiella K20 capsule genes were also found to be in close proximity to the his and rfb loci. Electron microscopy revealed significant differences in the structural organization of capsular polysaccharides in these two microorganisms and the morphological differences were also readily apparent in transconjugants expressing the respective K antigens. These results are consistent with the interpretation that at least some of the organizational properties of capsular polysaccharides may be genetically determined, rather than being a function of the outer membrane to which the capsular polysaccharides are ultimately attached.
Bacterial overgrowth by indigenous microflora in the phytohemagglutinin-fed rat
Authors: Banwell J. G. , Howard R. , Kabir I. , Costerton J. W.
Published: May 2010

Phytohemagglutinin lectin (PHA) derived from red kidney bean (Phaseolus vulgaris) causes bacterial and protozoal colonization of the rat small intestine. To provide additional insights into this phenomenon we have studied the time course and population dynamics of microbial colonization of the major aerobe – facultative anaerobe groups which characterize this microflora. Compared with controls, PHA caused proliferation of a consistent adherent microbial flora in the jejunum (P < 0.01). The predominant bacteria identified were Escherichia coli. a Streptococcal sp., and Lactobacillus. Escherichia coli isolates expressed no predominant serotype or fimbriae; none elaborated heat-labile or heat-stable toxin. Both E. coli and Streptococcal sp. populations increased within 24 h of PHA feeding and were sustained during further exposure to PHA (P < 0.05). On reversion to a control diet, coliform counts fell progressively within 24–48 h and continued to decline, whereas gram-positive rod and coccus flora became the more prominent colonizers through days 1 to 4 of the reversion.
Speculative cell cycle in yeast-phase growth of Sporothrix schenckii: plasma membrane ultrastructure as revealed by freeze-fracture electron microscopy
Authors: Maeda Manabu , Kitajima Yasuo , Mori Shunji
Published: May 2010

The cell cycle in yeast-phase growth of Sporothrix schenckii was investigated by light microscopy and freeze-fracture electron microscopy after a 3- to 7-day cultivation on brain heart infusion agar medium at 37 °C. Mother yeastlike cells were able to bear daughter yeastlike cells. They were also able to produce germ tubes that had the potential to develop into pseudohyhae and hyphae. On the other hand, hyphae or pseudohyphae born from yeastlike cells were able to bear yeastlike cells directly. These results lead us to propose a hypothetical cell cycle for yeast-phase growth involving yeastlike vegetative cells, pseudohyphae, and hyphae.
A direct viable counting method for measuring tolerance of aquatic microbial communities to Hg2+
Authors: Liebert Cynthia , Barkay Tamar
Published: May 2010

Direct counts of Hg2+ resistant cells in natural waters were obtained by fluorescence microscopy after incubation for 20 h in the presence of a growth substrate, nalidixic acid to halt cell division, and inhibiting concentrations of Hg2+. This method discriminated Hg2+ resistant from Hg2+ sensitive Escherichia coli strains. Estuarine samples were used to compare this procedure with two other toxicity measurements that determine the effect of Hg2+ on colony growth and on rates of radioactive thymidine incorporation into cellular material. Toxicity measurements based on direct viable counts and thymidine incorporation rates had comparable sensitivities, and both were 3–4 orders of magnitude more sensitive than the method that utilized colony counts. Thus, the direct enumeration of Hg2+ resistant cells is useful for predicting the potential of aquatic communities to sustain heterotrophic activity, an essential microbial process, in the presence of Hg2+.
Alterations in the pattern of polypeptide synthesis resulting from amino acid limitation in Neurospora crassa
Authors: Flint Harry J. , McKormick Janis
Published: May 2010

Two-dimensional electrophoresis was used to examine the pattern of polypeptide synthesis in Neurospora crassa mycelium of an arg-6 strain grown in the presence of [14C]arginine. Reduction in the arginine supply rate led to amino acid limited growth, and to major alterations in the pattern of polypeptide synthesis. Strains carrying wild-type (cpc-1+) or mutant (cpc-1) alleles at a locus governing cross-pathway control of amino acid synthetic enzymes differed markedly with respect to their pattern of polypeptide synthesis under limitation conditions, but differed little during arginine sufficient growth. Among 160 abundant polypeptide species classified for their response to limitation in two dimensional fluorographs, 31 were induced by limitation only in a cpc-1+ strain, 13 only in a cpc-1 strain, and 9 showed induction in both strains.
Response of hydroperoxidase and superoxide dismutase deficient mutants of Escherichia coli K-12 to oxidative stress
Authors: Schellhorn Herb E. , Hassan Hosni M.
Published: May 2010

In Escherichia coli, the coordinate action of two antioxidant enzymes, superoxide dismutase and hydroperoxidase (catalase), protect the cell from the deleterious effects of oxyradicals generated during normal aerobic respiration. To evaluate the relative importance of these two classes of enzymes, strains of E. coli deficient in superoxide dismutase and (or) hydroperoxidase were constructed by generalized transduction and their physiological responses to oxygen and oxidant stress examined. Superoxide dismutase was found to be more important than hydroperoxidase in preventing oxygen-dependent growth inhibition and mutagenesis, and in reducing sensitivity to redox-active compounds known to generate the superoxide anion. However, both types of enzymes were required for an effective defense against chemical oxidants that generate superoxide radicals and hydrogen peroxide.
The requirements for bicarbonate and metabolism of the inducer during germ tube formation by Candida albicans
Authors: Pollack Jordan H. , Hashimoto Tadayo
Published: May 2010

Factors affecting germ tube formation in Candida albicans at suboptimal temperatures were investigated. Candida albicans formed germ tubes between 22 and 30 °C in solution when incubated without shaking, in the presence of bicarbonate (2 mg mL−1). Other conditions depended on the inducer used. Proline could induce germ tube formation optimally only when its concentration was between 200 and 400 mM. A concentration of 0.05 mM N-acetylglucosamine was sufficient to induce germ tube formation. N-Acetylglucosamine could induce germ tube formation at 30 but not at 25 °C. N-Acetylglucosamine induced germ tube formation was most reproducible when the cells were first starved by incubation in water for 16–24 h at 20 °C. Germ tubes induced by proline could be formed at pH values between 3.8 and 9.0 at 30 °C, but only between 7.0 and 7.5 at 25 °C. The addition of 0.05 to 5 mM glucose to a 5 mM proline induction solution allowed germ tube formation at 30 but not at 25 °C. Glucose (400 mM) did not suppress germ tube formation at 30 °C but only 5 mM was sufficient to cause a 65% suppression at 25 °C. The results show the importance of CO2 and (or) bicarbonate to the induction of germ tube formation and are consistent with the metabolism of the inducer.
The Bacteroides glycocalyx as visualized by differential interference contrast microscopy
Authors: Lambe Jr. Dwight W. , Ferguson Kaethe P. , Ferguson Jr. Donald A.
Published: May 2010

The glycocalyx of eight strains representing six species of Bacteroides was examined by differential interference contrast microscopy. Wet mounts in India ink were prepared from bacteria cultured in broth and on an agar medium; the wet mounts were observed by phase-contrast microscopy and differential interference contrast microscopy. With differential interference contrast microscopy, all bacteria demonstrated a glycocalyx, which included capsules surrounding single cells and microcolonies, strands of glycocalyx connecting cells and microcolonies, detached slime, and solid masses of glycocalyx in which innumerable bacteria were enmeshed. Bacteria showed comparable amounts of glycocalyx by visual observation with differential interference contrast microscopy whether grown on plates or in broth. Serial transfers of cultures did not diminish the amount of glycocalyx. Differential interference contrast microscopy proved to be a superior method to phase contrast for examining wet preparations of Bacteroides.
Purification and initial characterization of deacetoxycephalosporin C synthase from Streptomyces clavuligerus
Authors: Rollins M. J. , Westlake D. W. S. , Wolfe S. , Jensen S. E.
Published: May 2010

Deacetoxycephalosporin C synthase, the penicillin N ring expansion enzyme from Streptomyces clavuligerus, was purified to near homogeneity, as judged by sodium dodecyl sulphate – polyacrylamide gel electrophoresis. The synthase was monofunctional and could be completely separated from deacetoxycephalosporin C hydroxylase activity early in the purification sequence. Synthase specific activity was increased 97-fold over crude cell-free extracts, and the purified enzyme appeared to be a monomer with a molecular weight of 36 000 and a Km for the penicillin N substrate of 50 μM. Deacetoxycephalosporin C synthase activity required α-ketoglutarate, Fe2+, and oxygen and was specifically stimulated by ascorbate and dithiothreitol. The enzyme was sensitive to thiol-specific inhibitors, the most effective of which was N-ethylmaleimide.
The composition of the rhizosphere of chicory (Cichorium intybus L. var. foliosum Hegi)
Authors: Outryve M. F. Van , Gosselé F. , Kersters K. , Swings J.
Published: May 2010

The bacterial composition of the chicory rhizosphere (Cichorium intybus L. var. foliosum Hegi) was examined at four different growth stages in the field and also after 1 month storage of the roots. Based on protein fingerprints (SDS – polyacrylamide gel electrophoresis of total cell proteins) 233 isolates were grouped into 117 different groups. Forty percent of the isolates belonged to one of three groups: CH001, CH002, or CH213. Fingerprint type CH001 and CH002 were comprised of fluorescent pseudomonads. Fingerprint type CH213 was identified as Alcaligenes paradoxus. Fingerprint type CH213 strains, normally isolated early in the growing season, were inhibited in vitro by fingerprint type CH001 strains which appeared later in the growing season. Gram-negative isolates were predominant among the remaining fingerprint types: Pseudomonas paucimobilis, Xanthomonas maltophilia, Agrobacterium radiobacter, and Flavobacterium spp. A few Gram-positive isolates were found at the beginning of the growing season, i.e., Bacillus spp. and Streptomyces spp. The production of antifungal compounds was restricted to the 11 isolates among which were fluorescent Pseudomonas and Bacillus spp. Twenty-four fluorescent pseudomonad isolates from the rhizosphere were pathogenic on chicory leaves.
Antibodies to arboviruses in an Alaskan population at occupational risk of infection
Authors: Stansfield Sally K. , Calisher Charles H. , Hunt Ann R. , Winkler William G.
Published: May 2010

A total of 435 United States Geological Survey and United States Forest Service workers in Alaska were studied for serologic evidence of past infections with four arboviruses known or suspected to be human pathogens. Of the personnel tested, 36 (8.3%) had the neutralizing antibody to Jamestown Canyon but not snowshoe hare virus, 6 (1.4%) had the antibody to snowshoe hare but not Jamestown Canyon virus, 53 (12.2%) had the antibody to both viruses, 17 (3.9%) had the antibody to Northway virus, and 15 (3.4%) had the antibody to Klamath virus. The indices most significantly correlated with presence of the Jamestown Canyon and snowshoe hare antibodies were the amount of field work (p < 0.0001 for both antibodies) and the duration of employment by the agencies (p < 0.0001 for Jamestown Canyon and 0.004 for snowshoe hare). The antibody to the four arboviruses also correlated strongly with a history of travel in certain remote or wilderness areas in Alaska (p values ranged from < 0.001 to 0.086).
Activity of phosphoenolpyruvate carboxylase of an anthracycline-producing streptomycete
Authors: Dekleva Michael L. , Strohl William R.
Published: May 2010

During fermantation studies on the production of anthracycline antibiotics by Streptomyces C5, it was observed that among the intermediate metabolism enzymes tested, only phosphoenolpyruvate carboxylase (PEPCase; EC 4.1.1.31) increased significantly in specific activity during stationary phase. The specific activity of the Streptomyces C5 PEPCase increased ca. 3-fold during antibiotic production phase from the logarithmic phase levels. To characterize the regulation of the enzyme further, the Streptomyces C5 PEPCase was purified 150-fold from crude extracts. Acetyl-CoA and Mg2+ were shown to be required for PEPCase activity. The activity of the partially purified PEPCase was stimulated slightly by fructose 1,6-bisphosphate and AMP, and was inhibited severely by oxaloacetate, aspartate, malate, succinate, ATP, citrate, and Co ASH.
Influence de la cytochalasine A sur la composition de fractions subcellulaires d'hyphes en croissance du Mucor mucedo L. I. Composition du plasmalemme
Authors: Mougith Abdou Ahmed Abd El Razak El , Fonvieille Jean-Louis , Dargent Robert , Rami Jacques , Touzé-Soulet Jane-Marie
Published: May 2010

The plasma membrane of young hyphae of Mucor mucedo L. growing in presence or absence of cytochalasine A was isolated by continuous density gradient centrifugation using Percoll at 10% or on discontinuous sucrose density gradient. Isolated membranes were characterized by enzymatic markers and cytochemical reactions, using electron microscopy. Lipid composition and protein content were determined. From the enzymatic point of view, the cytochalasine A induced a decrease (60%) in ATPase activity and with regard to the chemical composition of the membrane, a decrease in sterol content and in the sterol – phospholipid ratio as well as a decrease in protein content and an increase in the proportion of cysteine relative to other amino acids.
para-Hydroxybenzoate supported nitrogen fixation in Azotobacter vinelandii strain OP (13705)
Authors: Peterson Jay B. , Peterson Lynn S.
Published: May 2010

Azotobacter vinelandii cells grew with molecular nitrogen and p-hydroxybenzoate as the sole added nitrogen and carbon sources. Nitrogenase activity in p-hydroxybenzoate grown cells was demonstrated with the acetylene reduction assay. Cell extracts contained the enzymes p-hydroxybenzoate hydroxylase (EC 1.14.13.2) and protocatechuate 3,4-dioxygenase (EC 1.13.1.3); oxygenases associated with p-hydroxybenzoate metabolism. These enzymes separated from respiration particles with gel filtration chromatography, indicating that they are soluble and not membrane bound. This evidence indicates that oxygen enters to the inner face of the cytoplasmic membrane during nitrogen fixation.
An analytical procedure for the measurement of ATP extracted from activated sludge
Authors: Lefebvre Yves , Couture Pierre , Couillard Denis
Published: May 2010

There has been numerous attempts to link the ATP content of activated sludge to certain wastewater characteristics or to certain control parameters used in the operation of wastewater treatment plants. Published results vary and result from the use of different ATP extraction and measurement methods. This study deals with the development of an analytical method that requires filtration on polycarbonate membrane (0.4 μm) and a subsequent ATP extraction with DMSO. The filtration step overcomes problems of enzymatic inhibition in the firefly bioluminescence assay due to dissolved substances in the liquid fraction of the activated sludge samples. In comparison with extraction in boiling TRIS buffer, the most widely used method, extraction in DMSO was found to be effective and advantageous owing to its simplicity and reliability, the ease of its execution, and its potential use in routine measurements. The application of this analytical procedure to aerobic sludges in batch culture yielded a higher estimate of the average value of the ATP pool than previously published results.
Production of pili on Vibrio parahaemolyticus
Authors: Honda Takeshi , Arita Michiko , Ayala Edelira , Miwatani Toshio
Published: May 2010

Electron microscopic examination showed that all strains of Vibrio parahaemolyticus examined had pili on their surface when the organism was grown on marine agar at 28 °C for 6–12 h. The pili were morphologically stable on heat treatment at 60 °C for 10 min, but both the lateral and polar flagella possessed by this organism were labile. No immunological cross-reactivity between pili of enterotoxigenic Escherichia coli and Vibrio cholerae non-01 and those of V. parahaemolyticus was observed.
Polythionates and adenosine-5-phosphosulfate formation during thiosulfate oxidation by Thiobacillus neapolitanus
Authors: Skłodowska Aleksandra
Published: May 2010

The intermediates formed during thiosulfate oxidation by Thiobacillus neapolitanus were examined. Tetrathionate occurred as an intermediate compound and trithionate as one of the by-products. Adenosine-5-phosphosulfate was formed from the inner sulfur of the thiosulfate molecule, without reductive cleavage of Na2S2O3. A pathway for thiosulfate oxidation by T. neapolitanus is proposed.
Microbiological and virological analysis of water from two water filtration plants and their distribution systems
Authors: Payment Pierre , Gamache France , Paquette Gilles
Published: May 2010

The microbial flora of the water produced by two water filtration plants and their drinking water distribution system were evaluated: the Pont-Viau (PV) and the Repentigny (RE) water filtration plants. Untreated water entering the plants contained 3.6 (PV) and 16.8 most probable number of infectious units (mpniu)/L (RE) enteric viruses and total coliform bacteria counts were 300 000 (PV) and 500 000 cfu/L (RE). Treated water leaving the plant was essentially free of all the bacterial indicators measured (total, stressed, and fecal coliforms; Aeromonas hydrophila; Pseudomonas aeruginosa; Clostridium perfringens; enterococci) as well as of human enteric viruses. Heterotrophic plate counts at 20 and 35 °C were low in the freshly treated water leaving the plants, but bacterial regrowth was observed in both distribution systems at all sampling sites. Average counts for the heterotrophic plate count (20 °C) were between 106 and 107 cfu/L and counts were clearly increased with the distance from the plant. The most numerous bacterial genera encountered were Bacillus, Flavobacterium, and Pseudomonas (nonaeruginosa).
Tubulin and actin patterns in the life cycle of Saccharomycodes ludwigii Hansen
Authors: Daňková R. , Hašek J. , Streiblová E.
Published: May 2010

The proliferation mode of Saccharomycodes ludwigii was analyzed by immunofluorescence using monoclonal antibody Tu01 for examination of microtubules and rhodamine-labelled phalloidin for examination of F-actin. The patterns of staining of both the microtubular and actin components of the cytoskeleton confirmed that vegetative reproduction in this apiculate yeast occurs by combination of budding and fission. Treatment of vegetative cells with nocodazole (10 μg/mL) led to the formation of doublets. Agglutination, polarization of cells, and formation of irregularly shaped zygotes undergoing karyogamy were commonly obtained using haploid strains of opposite mating types. Microtubule and actin deployment during mating of S. ludwigii was basically the same as observed during sexual interactions in Saccharomyces cerevisiae.
Comparison of hemolysins of Vibrio cholerae non-O1 and Vibrio hollisae with thermostable direct hemolysin of Vibrio parahaemolyticus
Authors: Yoh Myonsun , Honda Takeshi , Miwatani Toshio
Published: May 2010

Hemolysin (Vh-rTDH) produced by Vibrio hollisae and hemolysin (NAG-rTDH) produced by Vibrio cholerae non-O1 were characterized and compared with hemolysin (Vp-TDH) produced by Vibrio parahaemolyticus. These three hemolysins are each composed of two subunits and have similar, but not identical, molecular weights. The amino acid compositions of Vp-TDH and NAG-rTDH are similar, but are different from that of Vh-rTDH. The three hemolysins showed similar lethal toxicities to mice. The effects of temperature on hemolysis and the time dependencies of hemolysis by the three hemolysins were similar. The three were concluded to be immunologically related, but not identical, and to have common and also unique antigenic determinants.
Glucose metabolism in Xanthomonas campestris and influence of methionine on the carbon flow
Authors: Pielken P. , Schimz K. -L. , Eggeling L. , Sahm H.
Published: May 2010

The glucose flow in Xanthomonas campestris was investigated with radio-labelled glucose and by enzymological studies. Only 7% of the radioactivity was incorporated into the cell material, but 41% was oxidized to carbon dioxide and 28% transformed to xanthan. Up to 16% of cell dry weight consisted of the polysaccharide glycogen. In the presence of 2.7 mM methionine, which is an inhibitor of xanthan formation, increased carbon dioxide formation (51%) occurred. This increase was in accordance with a twofold increase in the NAD-dependent isocitrate dehydrogenase activity. The other carbon dioxide liberating enzyme, 6-P-gluconate dehydrogenase, was not influenced by methionine, but its occurrence indicates the presence of an active pentose phosphate pathway in X. campestris. Among the other enzymes detected in X. campestris was glucose dehydrogenase. The presence of this enzyme together with hexokinase indicates the operation of two different glucose metabolizing steps: one oxidative, the other phosphorylative. Only the latter directly provides phosphorylated glucose as a precursor for the activated sugars required for xanthan synthesis.
Recovery of a marine chemolithotrophic ammonium-oxidizing bacterium from long-term energy-source deprivation
Authors: Johnstone Brian H. , Jones Ronald D.
Published: May 2010

The marine chemolithotrophic ammonium-oxidizing bacterium Nitrosomonas crytolerans was monitored during recovery after 5 weeks of energy-source deprivation. The organism responded immediately to the addition of [Formula: see text], producing [Formula: see text] at a constant rate. The cells used stored energy sources (ATP) and reducing equivalents (possibly NAD(P)H + H+) to immediately begin biosynthesis. However, these sources were quickly exhausted. Consequently, anabolism (14CO2 incorporation) decreased until levels of ATP and reducing potential were increased through oxidation of [Formula: see text]. Electron transport system activity steadily increased after the addition of [Formula: see text]. The increases in activities were greater than the increase in the total number of cells, suggesting that the increase in activity of the whole culture was due to either a physiological change in each cell or a reactivation of cells which had entered dormancy during energy-source deprivation. These results indicate that N. cryotolerans is well adapted to oligotrophic environments.
Neutralizing response of rabbits to an experimental rubella subunit vaccine made from immunostimulating complexes
Authors: Trudel Michel , Nadon Francine , Séguin Cécile , Payment Pierre
Published: May 2010

The purpose of this study was to evaluate experimentally the immunogenicity in rabbits of rubella subunits adsorbed to the adjuvant Quil A. The adsorbed viral proteins form structurally defined ImmunoStimulating COMplexes (ISCOMs). Rubella ISCOMs were tested for their capacity to induce neutralizing and hemagglutination-inhibiting antibodies, in comparison with a commercial live attenuated vaccine. Rubella ISCOMs were as efficient as the live vaccine in inducing neutralizing and hemagglutination inhibiting antibodies, suggesting the possibility of developing an ISCOMs subunit vaccine.
Mobilization and transfer of Azospirillum lipoferum plasmid by the Tn5-Mob transposon into a plasmid-free Agrobacterium tumefaciens strain
Authors: Bally René , Givaudan Alain
Published: May 2010

Azospirillum lipoferum 4B harbors five cryptic plasmids. Several suicide plasmids were used to transfer Tn5-Mob to A. lipoferum 4B. Tn5-Mob insertion mutations of this strain could be obtained at frequencies of 10−8–10−7 per recipient cell. One hundred Tn5-Mob A. lipoferum 4B mutants were used in bacterial matings with a plasmid-free Agrobacterium tumefaciens recipient strain. This is the first report of mobilization, transfer, and replication of an Azospirillum plasmid in Agrobacterium tumefaciens. One transconjugant was found which had lost an indigenous plasmid.
Phage typing set for differentiating Staphylococcus epidermidis
Authors: Gershman M. , Hunter J. A. , Harmon R. J. , Wilson R. A. , Markowsky G.
Published: May 2010

A phage typing set composed of 13 phages is described for characterizing Staphylococcus epidermidis. Isolates (372) from cases of bovine mastitis were used in this study. Of these, 350 or 94% were successfully delineated, and 63 phage types were observed. Twenty two cultures were not typeable.
Evidence for de novo synthesis of an aflatoxin pathway methyltransferase near the cessation of active growth and the onset of aflatoxin biosynthesis in Aspergillus parasiticus mycelia
Authors: Cleveland T. E. , Bhatnagar D.
Published: May 2010

The accumulation of both activity and protein of a methyltransferase (MTase) from Aspergillus parasiticus, which catalyzes conversion of sterigmatocystin to O-methylsterigmatocystin in the aflatoxin pathway, was detected in fungal mycelia slightly before the onset of aflatoxin biosynthesis in the same cultures. MTase protein was identified in mycelial postmicrosomal (soluble protein) fractions by electrophoresis and subsequent immunoblotting using antiserum raised against purified MTase protein; MTase activity was determined by measuring the rate of conversion of sterigmatocystin to O-methylsterigmatocystin in the presence of soluble protein fractions. Using the above technique, it was determined that MTase protein as well as MTase activity increased sharply in mycelia 30 to 45 h after inoculation, shortly after which, mycelial growth rate began to decline. During the subsequent time interval (45 to 70 h after inoculation), a sharp increase in aflatoxin levels was detected in the culture medium. Results obtained from an experiment in which cycloheximide was added to cultures at various times to inhibit protein synthesis and from an experiment in which mycelial proteins were radiolabelled to identify newly synthesized proteins indicated that accumulation of MTase activity and protein in late growth phase mycelia is due to de novo protein synthesis. Key words: aflatoxin, methyltransferase, biosynthetic pathway.
Trichoderma protoplast fusion: a tool for improving biocontrol agents
Authors: Pe'er S. , Chet I.
Published: May 2010

Protoplasts from two auxotrophic mutants of Trichoderma harzianum Rifai (ATCC 32173), obtained from young thalli following cell wall digestion by NovoZym 234, were fused in 33% PEG suspended in 10 mM Tris-HCl and 10 mM CaCl2, pH 7.5. The frequency of fusion between lysine- and arginine-requiring auxotrophs resulting in prototrophic strains was about 5%. These prototrophic strains were classified into parental and nonparental types. Colonies developed from single conidia of the nonparental phenotype exhibited prototrophic parental or recombinant phenotypes. The ability of both prototrophic and parental strains to overgrow the soil-borne pathogenic fungi Rhizoctonia solani, Sclerotium rolfsii, and Pythium aphanidermatum in dual cultures was used to evaluate their antagonistic capability. The antagonistic abilities of the prototrophic strains were found to vary with each pathogenic fungus. The prototrophic strain A2 overgrew all the pathogenic fungi more rapidly than the parental strains. Strain A2 effectively controlled Rhizoctonia damping-off of cotton seedlings, in the greenhouse, when compared with the parental strains. Protoplast fusion appears to be a useful tool for combining desirable traits from parental strains to produce improved biocontrol strains. Key words: Trichoderma harzianum, biocontrol, protoplast fusion.
Possible mode of action of Azospirillum brasilense strain Cd on the root morphology and nodule formation in burr medic (Medicago polymorpha)
Authors: Yahalom Eli , Okon Yaacov , Dovrat Amos
Published: May 2010

The mechanism(s) involved in the effect of Azospirillum brasilense strain Cd on root susceptibility to nodulation was studied in medic seedlings grown in pouches. The number of nodules above the position of the root-tip mark at the time of inoculation and the position of the uppermost nodule were used as parameters for determining the rate of nodule initiation. Cell-free extracts and culture supernatants prepared from Azospirillum and the cytokinin benzyladenine (10−9 M) significantly increased the number of nodules formed above the root-tip mark when applied together with Rhizobium compared with those formed with Rhizobium alone. The application of indoleacetic acid did not cause an increase in the number of nodules. In the absence of Rhizobium, exposure to Azospirillum at a concentration of 109 cfu/mL or to compounds excreted by the bacteria into the growth medium caused a 40% increase in endogenous ethylene production by the roots. A less concentrated inoculum did not increase ethylene production. Inoculation with Azospirillum significantly increased the specific activity of the enzymes glucose-6-phosphate dehydrogenase, L-phenylalanine ammonia-lyase, and shikimate dehydrogenase compared with roots inoculated with Rhizobium alone. Key words: Azospirillum, Rhizobium, Medicago polymorpha, root morphology, nodule initiation.
Restriction endonuclease fingerprinting analysis of Canadian isolates of Aeromonas salmonicida
Authors: McCormick Wayne A. , Stevenson Roselynn M. W. , MacInnes Janet I.
Published: May 2010

Restriction endonuclease fingerprinting (REF) analysis was used to examine total cellular DNA prepared from 56 independent field isolates of the fish pathogen, Aeromonas salmonicida. DNA was digested singly with the restriction enzymes EcoRI and HindIII, and the resulting fragments separated by polyacrylamide gel electrophoresis and visualized by silver staining. The REF patterns of typical isolates of A. salmonicida subsp. salmonicida were distinct from those of A. hydrophila, A. salmonicida subsp. achromogenes, A. salmonicida subsp. masoucida, and atypical isolates of A. salmonicida subsp. salmonicida. Differences between strains of typical A. salmonicida subsp. salmonicida could also be distinguished. Canadian isolates examined could be assigned to 1 of 12 different groups (REF groups), with the majority of the isolates belonging to REF groups 1 and 5. REF group 1 strains were isolated from British Columbia and New Brunswick while REF group 5 isolates were found in Ontario. None of the European strains examined had REF patterns identical to those of Canadian isolates. Based on REF analysis, there was little genetic heterogeneity detected among 23 isolates from two short-term studies of naturally occurring infections. Several different REF groups were seen among A. salmonicida collected over a 10-year period from coho salmon from the Credit River. Consistent with earlier biochemical and hybridization studies, the REF data suggest that A. salmonicida is a clonal pathogen. REF analysis can, however, permit the identification of subgroups, which may be useful in epidemiological studies. Key words: Aeromonas salmonicida, restriction fragment length polymorphism, restriction endonuclease fingerprinting, furunculosis, epidemiologic method.
A biometric study of higher alcohol production in Saccharomyces cerevisiae
Authors: Giudici Paolo , Romano Patrizia , Zambonelli Carlo
Published: May 2010

A hundred strains of Saccharomyces cerevisiae were examined for the ability to produce higher alcohols. In the strains tested the production of higher alcohols was found to be an individual strain characteristic and, as such, was statistically significant. The characteristics of the strains used (flocculation ability, foaming ability, killer character, and non-H2S production) were found to be uncorrelated to isobutanol and isoamyl alcohol production, whereas the production of high levels of n-propanol was found to be related to inability to produce H2S. This, in turn, suggests a link to methionine biosynthesis. Key words: Saccharomyces cerevisiae, higher alcohols, biometry, H2S production.
Influence of elevation and applied nitrogen on rhizosphere colonization and competition for nodule occupancy by different rhizobial strains on field-grown soybean and common bean
Authors: Abaidoo Robert C. , George Thomas , Bohlool B. Ben , Singleton Paul W.
Published: May 2010

In the absence of indigenous rhizobial populations, the pattern of competition between inoculum strains for nodule occupancy is found to be a stable characteristic, independent of rhizosphere population size, nitrogen application, or elevation. Soybean (Glycine max (L.) Merrill) and common bean (Phaseolus vulgaris L.), inoculated with peat-based rhizobia, were grown with three nitrogen levels at 320- and 150-m sites along an elevational transect on the island of Maui, Hawaii. Rhizosphere soil of 8-day-old plants was examined by immunofluorescence for populations of three strains each of Bradyrhizobium japonicum and Rhizobium leguminosarum bv. phaseoli, which made up the inocula applied to the respective host legumes at planting. Nodules were examined for occupancy by specific strains at two sampling times. Site differences and nitrogen treatment had no significant effect on rhizosphere colonization or nodule occupancy by the three strains. The three inoculum strains colonized their respective host rhizosphere in approximately equal numbers. In soybean, strain TAL 102(USDA 110) occupied most of the nodules, while strain TAL 379 (USDA 1366) was the least competitive in nodule formation in all treatments. In common bean, TAL 182 outcompeted the other two strains in nodule formation, while TAL 1797 (CIAT 899) occupied the least number of nodules. High elevation decreased nodulation by soybean more than that by common bean. Nitrogen application reduced nodule number and mass of both legumes more at the low-elevation than the high-elevation site; the reductions in nodule mass were more pronounced in common bean. The pattern of nodule occupancy remained stable regardless of the differences in nodule number and mass between elevations, N levels, and sampling times. Key words: rhizobial ecology, rhizosphere colonization, interstrain competition, immunofluorescence, legumes.
A freeze-fracture electron microscopic study of Frankia in root nodules of Alnus incana grown at three oxygen tensions
Authors: Abeysekera R. M. , Newcomb William , Silvester W. B. , Torrey John G.
Published: May 2010

Nodulated plants of Alnus incana ssp. rugosa and ssp. incana were grown with the roots exposed to 5, 21, and 40 kPa O2. The nodules were studied by freeze-fracture transmission electron microscopy to determine the effect of varying O2 tension on the numbers of lipid laminae in the Frankia envelope. Lipid laminae were present in the cell envelopes of hyphae, stalks, and symbiotic vesicles. The mean number of lipid laminae in hyphal envelopes varied from five to nine. Stalks of symbiotic vesicles contained mean numbers of 35–59 lipid laminae over the range of pO2's studied. Symbiotic vesicle envelopes showed mean numbers of lipid laminae varying from 48 to 94. The numbers of lipid laminae were observed to increase significantly in the distal regions of the symbiotic vesicles in response to raised pO2 while the numbers on the proximal portions remained unchanged. The increase in the numbers of lipid laminae in response to raised pO2 was not sufficient to account for the expected increase in resistance to O2 required at the symbiotic vesicle envelope if lipid laminae formed the exclusive diffusion barrier to O2. These results suggest that lipid laminae surrounding symbiotic vesicles may not constitute the only O2 protection mechanism in Alnus nodules. Key words: Alnus incana, Frankia, nitrogen fixation, actinorhizal nodules, Actinomycetes.
Disinfection of bacteria in water systems by using electrolytically generated copper:silver and reduced levels of free chlorine
Authors: Yahya Moyasar T. , Landeen Lee K. , Messina Maria C. , Kutz Susan M. , Schulze Richard , Gerba Charles P.
Published: May 2010

As an alternative disinfectant to chlorination, electrolytically generated copper:silver (400 and 40 μg/L copper and silver, respectively) with and without free chlorine (0.3 mg/L) was evaluated over a period of 4 weeks in indoor and outdoor water systems (100 L tap water with natural body flora and urine). Numbers of total coliform, pseudomonas, and staphylococci were all less than drinking water standards in systems treated with copper:silver and free chlorine and systems treated with free chlorine alone (1.0 mg/L). No significant differences (p ≤ 0.05) in bacterial numbers were observed between systems with copper:silver and free chlorine and those with free chlorine alone. Overall, free-chlorine treatments (0.3 or 1.0 mg/L) showed significantly lower heterotrophic plate numbers than those without free chlorine. When challenged with a natural Staphylococcus sp. isolate, water with copper:silver and free chlorine had a 2.4 log10 reduction in bacterial numbers within 2 min, while free chlorine alone or copper:silver alone showed 1.5 and 0.03 log10 reductions, respectively. Addition of copper:silver to water systems may allow the concentration of free chlorine to be reduced while still providing comparable sanitary quality of the water. Key words: disinfection, water, copper, silver, chlorine.
Antibodies to meningococcal H.8 (Lip) antigen fail to show bactericidal activity
Authors: Bhattacharjee Apurba K. , Moran Elizabeth E. , Zollinger Wendell D.
Published: May 2010

Purified H.8 (Lip) antigen was coupled to tresyl-activated Sepharose 4B and used in affinity columns to purify anti-Lip antibodies from convalescent patient sera and from immune rabbit sera. Affinity-purified anti-Lip antibodies isolated from two convalescent patient sera contained 1000 and 1280 ELISA units of antibody and included antibodies of IgG, IgA, and IgM isotypes. An anti-Lip mouse monoclonal ascites (2-1-CA2) had 28 400 ELISA units of antibody. Bactericidal assays were performed using three different case strains of Neisseria meningitidis group B, namely 44/76, 8532, and 8047. Neither preparation of purified human anti-Lip antibodies had detectable bactericidal activity against strains 44/76 and 8532, but one of the two had a titer of 1:4 against strain 8047. Anti-Lip antibodies that were purified from immune rabbit serum and contained 1600 ELISA units of anti-Lip antibodies also failed to show detectable bactericidal activity. The rabbits were immunized with purified Lip antigen and showed specific antibody levels of 2000–2200 units by ELISA, but even the unfractionated sera had little or no bactericidal activity against the test strains. The high titer mouse monoclonal ascites had no bactericidal activity against the test strains. The poor bactericidal activity associated with monoclonal and polyclonal antibodies to the Lip antigen suggest that in spite of other attractive properties it may not be useful as a meningococcal vaccine. Key words: anti-Lip, antibodies, bactericidal, Neisseria, Lip.
Preliminary characterization of four bacteriocins from Streptococcus mutans
Authors: Parrot M. , Caufield P. W. , Lavoie M. C.
Published: May 2010

The various properties of the inhibitory substances produced by Streptococcus mutans strains C67-1, Ny257-S, Ny266, and T8, and the fact that inhibitory zones produced could not be associated with lactic acid (or other organic acids), bacteriophages, or hydrogen peroxide indicate that these substances can be classified as mutacins. The substances produced by strains C67-1, Ny266, and T8 possessed similar properties. They were shown to be thermoresistant (100 °C, 30 min), low molecular weight (< 3500) substances sensitive to proteolytic enzymes (chymotrypsin, papain, pronase E, proteinase K, and trypsin) and they were active against most of the Gram-positive bacteria tested but not against most of the Gram-negative bacteria. The substance produced by strain Ny257-S differs from the other three by its narrower activity spectrum, its lower thermoresistance (80 °C, 30 min), and its higher molecular weight (8 000–14 000). The gene or the genes coding for the mutacins are probably located on the chromosome since no plasmid DNA could be detected in these four producing strains. Restriction-fragment patterns of C67-1 and T8 suggest that these strains are closely related, as supported by the strong similarity observed between the properties of their mutacins. Key words: bacteriocin, mutacin, Streptococcus mutans, inhibitory substance.
Competitiveness of inoculant strains of Rhizobium leguminosarum bv. trifolii in red clover using repeated inoculation and increased inoculum levels
Authors: Mårtensson Anna M.
Published: May 2010

The effects of inoculation of red clover with Rhizobium leguminosarum bv. trifolii strains 285 and 7612 were studied. In greenhouse experiments repeated inoculations were made. Strain 285 occupied all nodules when included, and strain 7612 increased its nodule occupancy with repeated inoculation. In field studies, where native, ineffective red clover bacteria were present, increased levels of inoculum were added, which increased dry matter production and nitrogen content of the plants. Yields from plants inoculated with strain 7612 were higher but dependent on inoculum concentration. The number of early nodules occupied by inoculant bacteria increased with increasing inoculum concentrations of strain 7612 but not of strain 285. The inoculant strain occupancy of late nodules was unaffected by inoculum levels in both cases. Acetylene reduction and accumulation of 14C-labelled metabolites in nodules situated at different distances from the shoots and in nodules of different ages, including overwintering nodules, were studied. Nodule placement did not influence the biological activity of the nodules. Old nodules were less active on a dry matter basis, but since they are larger, they may have contributed to the nitrogen balance of the plants as much as young nodules. Overwintering the plants did not change this pattern. Key words: competition, inoculation, nodule life cycle, Rhizobium.
Electron microscopy study of the bacteria adherent to the rumen wall in young conventional lambs
Authors: Rieu Franoise , Fonty G. , Gaillard Brigitte , Gouet P.
Published: May 2010

The lamb rumen walls were rapidly colonized by an abundant bacterial population after birth. This colonization was examined by electron microscopy in neonatal conventional lambs. The sequence of establishment of the epimural species during the 3 weeks following birth, and the distribution of bacteria on the different sacs of the rumen, were examined by scanning electron microscopy. The population was very dense and consisted of a limited number of morphological types by 2 days after birth. Three types of rods were dominant at that time. The microflora was more complex 2 weeks later. Observations by transmission electron microscopy of desquamated epithelial cells revealed the presence of adherent bacteria that are surrounded by fibrous carbohydrate coats and sometimes partially enclosed by invaginations of the epithelial cell. Key words: rumen, lamb, microflora, scanning electron microscopy, adherence.
Mineralization of [14C]hexadecane and [14C]phenanthrene in crude oil: specificity among bacterial isolates
Authors: Foght J. M. , Fedorak P. M. , Westlake D. W. S.
Published: May 2010

Bacteria isolated from freshwater, marine, and estuarine samples were tested for the ability to produce 14CO2 from n-[1-14C]hexadecane or [9-14C]phenanthrene added to Prudhoe Bay crude oil. Of 138 isolates tested, 54 (39%) mineralized the model aliphatic compound hexadecane and 6 (4%) mineralized the model aromatic compound phenanthrene. None mineralized both compounds. There was no apparent correlation between degradative ability and genus or source. Additional hydrocarbon-degrading bacteria from diverse sources were tested and found to mineralize either hexadecane or phenanthrene. Of 61 hexadecane- and 21 phenanthrene-mineralizing bacteria tested, none mineralized both model compounds. Selected isolates and commercially available cultures were tested for mineralization of specific 14C-labelled mono-, di-, and tri-cyclic aromatics. An apparent hierarchy of degradation was observed: strains mineralizing the mono- and di-cyclic aromatics toluene and naphthalene did not mineralize biphenyl or the tricyclic aromatics anthracene and phenanthrene, whereas those strains that mineralized the tricyclic aromatics also mineralized the smaller substrates. Similarly, not all n-alkane-mineralizing isolates tested mineralized the isoprenoid pristane. A combined culture consisting of one aliphatic- and one aromatic-degrading isolate was tested for mineralization of the model compounds and for degradation of other crude oil components by gas chromatography. No synergism or antagonism was observed compared with degradation by the individual isolates. Key words: aromatic, aliphatic, bioegradation, petroleum.
Growth dynamics of cyclomaltodextrin glucanotransferase producing Bacillus circulans var. alkalophilus
Authors: Mäkelä Mauri J. , Paavilainen Sari K. , Korpela Timo K.
Published: May 2010

The time course of the growth of cyclomaltodextrin glucanotransferase (EC 2.4.1.19; CGTase) producing Bacillus circulans var. alkalophilus (ATCC 21783) was studied using shaking-flask cultivations. The growth curve was diauxic and during the initial phase the pH decreased sharply by 1.3–1.5 units. Most of the total carbohydrates disappeared prior to the bulk growth, which corresponded to a transient peak of amylolytic enzyme activity and of reducing sugars followed by acid production. During active cell growth the pH recovered by about 0.5 units and 65% of the final CGTase appeared in the medium. Another 20% was produced during the stationary phase and 15% was produced in the death phase. The growth dynamics of two randomly selected alkalophilic Bacillus strains (ATCC 27647 and 27557) were compared with those of ATCC-strain 21783. The reference strains showed related growth behavior with the exception that the timing and magnitudes of the changes in the growth parameters measured were different. The effects of carbon source (starch), nitrogen source (yeast extract plus Bacto-pantone), sodium carbonate, and temperature were studied from the point of view of CGTase production. Key words: cyclomaltodextrin glucanotransferase; alkalophilic bacilli; cyclodextrins.