bluuebunny/crossref_metadata_2025 huggingface dataset:
Molecular analyses of conjugative, gentamicin-resistance plasmids from staphylococcal clinical isolates
Authors: Zorbas Ioannis , Hall Robert T. , Hall Sue L. , Barnes William G. , Rogolsky Marvin
Published: May 2010

Gentamicin-resistant Staphylococcus aureus and Staphylococcus epidermidis strains which were isolated from infants with staphylococcal bacteremia were analyzed for the presence of self-transmissible gentamicin-resistance (Gmr) plasmids. Conjugative GMr plasmids of approximately 43.8–63 kilobases (kb) were found in all S. aureus strains. Inter- and intra-species transfer of Gmr plasmids by conjugation was observed from S. aureus to S. aureus and to S. epidermidis recipient strains. However, neither inter- nor intra-species transfer of gentamicin resistance by conjugation was observed with nine out of nine S. epidermidis donor strains which were mated with either S. epidermidis or S. aureus recipient strains. These conjugative Gmr plasmids were unable to comobilize a smaller (15-kb) plasmid present in all but two S. aureus clinical isolates. Many of the conjugative Gmr plasmids also carried genetic determinants for kanamycin, tobramycin, neomycin, and ethidium bromide resistance, and for β-lactamase synthesis. EcoRI restriction endonuclease digests of the S. aureus Gmr conjugative plasmids revealed three different digestion patterns. Four EcoRI restriction endonuclease digestion fragments of 15, 11.4, 6.3, and 4.6 kb in size were common to all plasmids. These plasmids and conjugative Gmr staphylococcal plasmids from other geographical regions shared restriction digestion fragments of similar molecular weights. DNA hybridization with biotinylated S. aureus plasmid pIZ7814 DNA revealed a high degree of homology among these plasmids. A 50.9-kb plasmid from one of the nonconjugative S. epidermidis clinical isolates showed homology with the probe DNA but lacked a portion of a 6.3-kb fragment which was present in all conjugative plasmids and believed to carry much genetic information for conjugation.
Effect of incubation temperature, ageing, and bisulfite content of unsupplemented Brucella agar on aerotolerance of Campylobacter jejuni
Authors: Lee Mann-Hsi T. , Smibert Robert M. , Krieg Noel R.
Published: May 2010

A mutant strain of Campylobacter jejuni ATCC 29428 was isolated that grows on unsupplemented Brucella agar at O2 levels as high as 21% at 37 °C. While measuring the degree of aerotolerance of this mutant on unsupplemented Brucella medium and comparing it with that of the wild type, we found considerable variation among our estimates. As measured by colony counts on unsupplemented Brucella agar incubated at various oxygen levels, the degree of aerotolerance was affected by incubation temperature and the age of the medium. Aerotolerance was consistently higher on plates incubated at 42 °C than at 37 °C. When the commercial dehydrated Brucella medium that was used to prepare the Brucella agar was stored in a beaker for 2.5 months, the degree of aerotolerance of C. jejuni was decreased. Addition of 0.01% sodium bisulfite reversed this inhibition. Storage of bottles of hydrated Brucella agar for 1.5 months also resulted in a decreased aerotolerance; again, an addition of 0.01% bisulfite reversed the effect. Aerotolerance was greatly decreased when Brucella agar was prepared from all its individual components except 0.01% bisulfite. The results indicate that the bisulfite component of Brucella agar deteriorates during storage of the dehydrated and hydrated media, and that this deterioration can affect measurements of aerotolerance.
Inhibition of Metarhizium anisopliae by the gut bacterial flora of the desert locust: characterisation of antifungal toxins
Authors: Dillon R. J. , Charnley A. K.
Published: May 2010

Antifungal compounds have been found in gut fluid and aqueous faecal extracts from parasite-free and conventional desert locusts (Schistocerca gregaria), but not from germ-free locusts. These compounds inhibit germination of four isolates of Metarhizium anisopliae and 10 other species of insect and plant pathogenic fungi. Low molecular weight (< 200) antifungal compounds were purified from faecal extracts using ion-exchange and gel chromatography. Hydroquinone, 3,4-dihydroxy-and 3,5-dihydroxy-benzoic acid were identified using gas chromatography and mass spectrometry. The phenols possessed antifungal activity at concentrations estimated to be present in the inhibitory faecal extract. The low molecular weight compounds were found in extracts from conventional and parasite-free locusts, but were absent from extracts from germ-free insects. The results are consistent with the hypothesis that antifungal phenols, produced by the gut bacterial flora, are responsible for the fungitoxic activity in the gut of the desert locust. Antifungal activity was also located in the guts of seven Orthopteran species of insects using conidia of M. anisopliae (strain ME1) as a bioassay.
In vitro regulation of chitinase and chitin synthase activity of two mucoraceous hosts of a mycoparasite
Authors: Manocha M. S. , Balasubramanian R.
Published: May 2010

Effects of partially purified preparations of proteinases extracted from Choanephora cucurbitarum and Phascolomyces articulosus, susceptible and resistant hosts of Piptocephalis virginiana, respectively, were studied in vitro on the activities of chitinase and chitin synthase of the same hosts. Both chitinase and chitin synthase are membrane bound, zymogenic, and activated by partial proteolysis. Host proteinases of acid and neutral type stimulated chitinase activity, but only the acid proteinase stimulated chitin synthase activity of the two hosts. Neutral proteinase of C. cucurbitarum inhibited its chitin synthase, whereas that of Ph. articulosus increased its chitin synthase activity. Partially purified preparations of neutral proteinase from the mycoparasite, Piptocephalis virginiana, however, enhanced chitinase and suppressed chitin synthase activity of both the hosts alike. The role of host proteinases in regulating the activity of chitinase and chitin synthase of the two host species is suggested.
Comparison of whole-cell protein electrophoretic profiles of Haemophilus influenzae: implementation of a microcomputer mainframe linked system and description of a new similarity coefficient
Authors: Albritton W. L. , Chen X. P. , Khanna V.
Published: May 2010

A microcomputer mainframe linked system is described which allows video camera data capture and storage of one-dimensional whole-cell protein electrophoresis gel images, processing of normalized traces to produce a similarity matrix, and analysis of the matrix using the commercial cluster analysis program CLUSTAN. A new similarity coefficient is introduced which takes into account both band position and intensity. Forty-five strains of Haemophilus influenzae, including the eight biotypes and six serotypes, were analyzed using this system. Results demonstrated groupings which are consistent with known genetic relationships.
Heat-shock response in Legionella pneumophila
Authors: Lema Michael W. , Brown Arnold , Butler Charles A. , Hoffman Paul S.
Published: May 2010

The heat-shock response of Legionella pneumophila was examined by radiolabelling bacterial cell proteins with [35S]methionine following a temperature shift from 30 to 42 °C. Five heat-shock proteins were identified as having molecular masses of 17, 60, 70, 78, and 85 kilodaltons (kDa). The 85- and 60-kDa proteins were equally distributed between supernatant and pellet fractions following ultracentrifugation at 100 000 × g, the 70- and 78-kDa proteins were found primarily in the supernatant, and the 17-kDa protein was found primarily in the pellet. Synthesis of subsets of the heat-shock proteins could be stimulated by novobiocin, patulin, or puromycin. Ethanol, an effector of the heat-shock response in other microorganisms, had little effect on L. pneumophila, even at the highest concentration tolerated by the bacterial cells (1.9%). Finally, the 60-kDa heat-shock protein of L. pneumophila was immunologically cross-reactive with a polyclonal antibody prepared to the Escherichia coli groEL protein. However, a mouse monoclonal antibody reactive with the 60-kDa protein of all legionellae tested did not cross-react with the E. coli groEL protein, suggesting that the Legionella 60-kDa protein contains common and unique epitopes.
Role of the carbon source in regulating chloramphenicol production by Streptomyces venezuelae: studies in batch and continuous cultures
Authors: Bhatnagar R. K. , Doull J. L. , Vining L. C.
Published: May 2010

Both carbon- and nitrogen-limited media that supported a biphasic pattern of growth and chloramphenicol biosynthesis were devised for batch cultures of Streptomyces venezuelae. Where onset of the idiophase was associated with nitrogen depletion, a sharp peak of arylamine synthetase activity coincided with the onset of antibiotic production. The specific activity of the enzyme was highest when the carbon source in the medium was also near depletion at the trophophase–idiophase boundary. In media providing a substantial excess of carbon source through the idiophase, the peak specific activity was reduced by 75%, although the timing of enzyme synthesis was unaltered. Morever, chemostat cultures in which the growth rate was limited by the glucose concentration in the input medium failed to show a decrease in specific production of chloramphenicol as the steady-state intracellular glucose concentration was increased. The results suggest that a form of "carbon catabolite repression" regulates synthesis of chloramphenicol biosynthetic enzymes during a trophophase–idiophase transition induced by nitrogen starvation. However, this regulatory mechanism does not establish the timing of antibiotic biosynthesis and does not function during nitrogen-sufficient growth in the presence of excess glucose.
Chemical characterization of lipopolysaccharide from Edwardsiella ictaluri, a fish pathogen
Authors: Weete J. D. , Blevins W. T. , Chitrakorn S. , Saeed M. O. , Plumb J. A.
Published: May 2010

The chemical components of lipopolysaccharide (LPS) from the fish pathogen Edwardsiella ictaluri (Ed. ictaluri) were analyzed by SDS–PAGE, gas chromatography, and spectrophotometry, and compared with those of Salmonella typhimurium and Escherichia coli 0111:B4. Only four to five low molecular weight species of LPS from Ed. ictaluri were detected by silver staining after separation by polyacrylamide gel electrophoresis. The low molecular weight species, as well as a low sugar content, indicated that the LPS from Ed. ictaluri was of the rough type, compared with that of S. typhimurium and E. coli which were both of the smooth type LPS. Quantitatively, mannose was not a major sugar component in Ed. ictaluri, unlike S. typhimurium. Palmitic, palmitoleic, and cis-9,10-methylene-hexadecanoic acids were predominant fatty acids among the total cellular lipids of Ed. ictaluri. C14 fatty acids comprised 78% of the total in the LPS of this bacterium, with β-hydroxy-myristate representing 55%. The results of this study suggest that the lipid A segment of the LPS molecule of Ed. ictaluri is similar to S. typhimurium and E. coli, at least with respect to fatty acid content; however, the core polysaccharide of E. ictaluri differs in that it has twice the heptose content.
Attenuation of transcription of biotin genes in Escherichia coli
Authors: Nath Swapan K.
Published: May 2010

The nature of RNA synthesis from the divergent bioA:BFCD operon has been studied in vivo in Escherichia coli minicells. Minicells containing bio-recombinant plasmids produce 96 nucleotide long RNA. This small RNA was characterized by blotting on diazobenzyloxymethyl cellulose paper and hybridization with the appropriate bio-probe DNA. Determination of β-galactosidase, using biotin requiring mutant cells of E. coli JM101 infected with a bio-M13 recombinant phage containing the functional bioB region of the operon, demonstrated the presence of a transcription termination site in the bioBFCD segment. There was a three- to five-fold reduction in β-galactosidase activity in this system at an appropriate d-biotin concentration which indicated that the early termination of transcription is biotin dependent. From the nucleotide sequence of the promoter proximal region of the bioB gene, a 13-oligonucleotide sequence believed to be the early transcription termination site has been located. A model of regulation at termination has been proposed on the basis of the not-too-stable RNA secondary structure at the site of early termination of transcription.
Induction of tyrosinase by L-methionine in Streptomyces antibioticus
Authors: Katz Edward , Betancourt Aline
Published: May 2010

Investigations were carried out to establish conditions favorable for the formation of tyrosinase, an inducible metalloenzyme synthesized by Streptomyces antibioticus. It was determined that the size of the inoculum and age of the culture as well as the temperature of incubation were important factors for enzyme synthesis. Induction of tyrosinase by S. antibioticus appears to be specific for L-methionine with maximal enzyme synthesis observed at 0.1 mM. Addition of CuSO4 and D-glucose at the time of induction also are important for increased enzyme activity. Inhibition of tyrosinase synthesis was observed with actinomycin D, rifampicin, and chloramphenicol suggesting that both transcriptional and translational events are required for tyrosinase induction.
Pseudo-exponential growth in length of the fission yeast, Schizosaccharomyces pombe
Authors: Miyata Hisao , Miyata Machiko , Johnson Byron F.
Published: May 2010

The growth patterns of individual cells of the fission yeast (Schizosaccharomyces pombe wild-type cells, strain 972 h−; cells exposed to hydroxyurea; and cdc mutants, 11-123, 2-33) were investigated by time-lapse photomicrography. Wild-type cells showed one, two, or three linear-growth segments followed by a constant-length stage. Cells with two segments were most frequent. Hydroxyurea cells that divided as oversized cells (about three times the birth length) had three linear-growth segments in a cycle. Mutant cdc11-123 cells did not divide but had a constant-length stage separating the cycles; both the first and second cycles consisted of two linear-growth segments, and cells were oversized at the second constant-length stage (about 3.5 times the birth length). Elongating cdc2-33 cells that did not divide and were oversized (about five times the birth length) while under observation, showed four linear-growth segments. Cells of all strains showed 30 to 40% increase in growth rate at the rate-change point and maintained approximate exponential (pseudo-exponential) growth. We conclude that the normal growth pattern of individual fission-yeast cells is the pseudo-exponential pattern.
Isolation and immunochemical characterization of fractions from membranes of Aspergillus fumigatus with protease activity
Authors: Piechura James E. , Kurup Viswanth P. , Daft Laureen J.
Published: May 2010

Two fractions exhibiting acid protease activity (AFPI and AFPII) were isolated by extraction of membrane vesicles of Aspergillus fumigatus with Triton X-100. These two fractions produced single bands in both polyacrylamide and sodium dodecyl sulfate polyacrylamide gel electrophoresis and showed apparent molecular weights of 73 000 and 43 000, respectively. Molecular weights determined by gel filtration in the absence and presence of Triton X-100 and sedimentation velocities in analytical ultracentrifugation indicated hydrophobic characteristics, since both fractions readily aggregated and complexed with Triton X-100; both exhibited elevated enzyme activities in the presence of Triton X-100. Carbohydrate content was 93% for AFPI and 85% for AFPII. The enzymatic fractions demonstrated different pH optima in the acid range as well as different temperature stabilities. Both protease fractions cross reacted in double immunodiffusion, while in crossed immunoelectrophoresis both demonstrated five precipitin peaks, each with similar patterns. AFPI demonstrated two additional precipitin peaks in crossed immunoelectrophoresis. As determined by crossed immunoaffinoelectrophoresis, the protease fractions demonstrated galactose and mannose residues. In biotin–avidin enzyme-linked immunosorbent assay both fractions reacted with allergic bronchopulmonary aspergillosis and aspergilloma sera. It can be concluded that the two fractions with protease activity of A. fumigatus reported here may be of significance in Aspergillus-induced diseases. Key words: Aspergillus, membrane, allergens, proteases, aspergillosis.
Molecular epidemiology and novel combinations of auxotype, serovar, and plasmid content in tetracycline-resistant Neisseria gonorrhoeae isolated in Canada
Authors: Dillon Jo-Anne R. , Carballo Maria
Published: May 2010

Between October 1987 and June 1989, 84 isolates of Neisseria gonorrhoeae carrying the TetM resistance determinant (TRNG) were received at the Laboratory Centre for Disease Control, Ottawa, from six Canadian provinces and were characterized into classes based on auxotype, serovar and plasmid content. One-fifth (17/84) of the TRNG were also penicillinase producing (PPNG). The PPNG–TRNG isolates comprised six classes based on auxotype, serovar, and plasmid content. Most (16/17) PPNG–TRNG carried 3.2-MDa β-lactamase plasmids and the 25.2-MDa TetM-containing plasmid. We report, for the first time, the association of a 4.5-MDa β-lactamase plasmid with the 25.2-MDa plasmid in a clinical TRNG isolate. Non-PPNG TRNG isolates comprised 11 classes based on auxotype, serovar, and plasmid content, including two previously unreported auxotype–serovar classes, P/IB-26 and P/IB-20. Key words: Neisseria gonorrhoeae, tetracycline resistance, plasmid, epidemiology.
Production of conidia by Phomopsis convolvulus
Authors: Morin Louise , Watson Alan K. , Reeleder Richard D.
Published: May 2010

Various solid-substrate fermentation and shake-flask liquid fermentation systems were investigated as spore production methods for Phomopsis convolvulus, a potential bioherbicide. Among them, "pot" barley grains and modified Richard's (V-8) liquid medium produced 5 × 108 conidia/g and 5 × 106 conidia/mL, respectively. Distinct pycnidia, covering the surface of pot barley grains, produced virulent conidia in a water-soluble mucilage approximately 10 days after seeding the substrate with conidia. In complex liquid media, conidia were produced in pycnidia 3 to 4 days after seeding the media with mature pycnidia or conidia. A negative relationship was demonstrated between inoculum density and yield of conidia in modified Richard's (V-8) liquid culture. Omission of V-8 juice or decrease of the carbon to nitrogen ratio in modified Richard's (V-8) medium inhibited sporulation. Conidia lost viability after 30 days when held at −10 °C in a sucrose solution, but conidia stored at −70 °C remained viable and pathogenic for at least 6 months. Key words: Phomopsis convolvulus, bioherbicide, sporulation.
Binding of staphylococcal cell surface polysaccharide to human fibrinogen
Authors: Ohtomo Toshichika , Kobayashi Tsugiaki , Ohshima Yukio , Usui Yukio , Suganuma Masaru , Yoshida Kosaku
Published: May 2010

The interaction between the binding site of a polysaccharide (called compact colony forming active substance (CCFAS)), obtained from the cell surface of a strain of Staphylococcus, and human fibrinogen (HF) was investigated. The CCFAS was found to bind specifically to both the Bβ and γ chains of HF at pH 7.0 and 8.0, and the Aα chain at pH 5.0. The binding of CCFAS with fibrinogen fragments obtained by digestion with plasmin were also investigated. Fragments with Mr of 55 000, 24 000, and 19 000 were the major bands precipitated by CCFAS at pH 7.0 and 8.0. Fragments with Mr of 85 000 and 75 000 bound to CCFAS at pH 5.0. Binding of CCFAS (7 μg) with fibrinogen could be inhibited by 1.2 μg of Bβ chain and 1.5 μg γ chain at alkaline pH or 6.2 μg of the Aα chain at pH 5.0. CCFAS was, therefore, assumed to be specifically bonded with HF molecules, in the alkaline range at least, resulting in compact colony forming activity in serum soft agar and paracoagulation. Key words: cell surface, polysaccharide, Staphylococcus aureus, fibrinogen.
Synthesis of cell wall glucan, chitin, and protein by regenerating protoplasts and mycelia of Trichoderma reesei
Authors: Messner Robert , Kubicek Christian P.
Published: May 2010

The synthesis of constituent polymers of the cell wall by either growing mycelia or regenerating protoplasts of Trichoderma reesei QM 9414 was investigated by following the incorporation of radioactive precursors of the individual polymers (i.e., N[14C] acetyl-glucosamine, [3H] and [14C]glucose, [14C]mannose, and [35S]methionine) into individual fractions. N-Acetyl-glucosamine and glucose were found to become specifically incorporated into cell wall chitin and glucan by both mycelia and regenerating protoplasts, indicating the activity of chitin and glucan synthases in both systems. Cell wall glucan from regenerating protoplasts, however, consisted only of α-glucan and specifically lacked β-glucan which is found in mycelial cell walls. Mannose became metabolized to glucose before its label appeared in the cell wall, and was thus unsuitable for specific labelling. [35S]Methionine was found in a small (< 21 kDa) polypeptide from the first alkali-soluble cell wall fraction, but also in cell wall bound secretory proteins, i. e., β-glucosidase. These results indicate that cell wall biogenesis in T. reesei, in contrast to a report by other authors, is similar to that of other filamentous fungi. Key words: Trichoderma reesei, protoplast regeneration, cell wall polymer, β-glucan, cell wall protein.
Occurrence of homospermidine as a major polyamine in the authentic genus Flavobacterium
Authors: Hamana Koei , Matsuzaki Shigeru
Published: May 2010

Polyamines in various Flavobacterium strains and related eubacteria were analyzed. The major polyamine was homospermidine in all 12 strains of the eight authentic species of the genus Flavobacterium studied (F. aquatile, F. breve, F. balustinum, F. gleum, F. meningosepticum, F. odoratum, F. multivorum, and F. spiritivorum), and in F. ferrugineum, whose taxonomic position is uncertain but related to Flavobacterium. Spermidine was not detected in these flavobacteria. In another seven Flavobacterium species that are taxonomically different from Flavobacterium and belong to other genera, homospermidine was not detected. Key words: Flavobacterium, homospermidine, spermidine, arginine decarboxylase.
Plant growth promoting rhizobacteria: strain identification by restriction fragment length polymorphisms
Authors: Brown Gerry , Khan Zeayen , Lifshitz Ran
Published: May 2010

A genomic library of the Pseudomonas putida strain GR12-2 was screened to identify both genus-universal and strain-specific 8-kilobase inserts. The genus-universal clone (pAM141), in combination with the restriction enzymes EcoRI, PstI, and PvuII, was used to generate unique restriction fragment length polymorphisms for 20 related plant growth promoting rhizobacteria and seven reference strains. Strain restriction fragment length polymorphism profiles based on the genus-universal clone pAM141 allow positive identification of individual pseudomonad strains. The strain-specific clone (pAM227) clearly distinguished the parent strain (GR12-2) from 16 other pseudomonad strains, including 8 P. putida, 7 P. fluorescens, and 1 P. cepacia. pAM227 may be useful for monitoring the fate of the P. putida strain GR12-2 in the environment. Key words: pseudomonads, rhizobacteria, restriction fragment length polymorphism, strain identification.
Plant growth promoting rhizobacteria for winter wheat
Authors: Freitas J. Renato de , Germida James J.
Published: May 2010

The association of winter wheat (Triticum aestivum L. cv. Norstar) with root-colonizing bacteria (rhizobacteria) was studied in potted soil experiments in the growth chamber. Thirty-six known bacteria, some of which have been reported to stimulate plant growth, and 75 isolates obtained from the rhizosphere of winter wheat were tested for their effects on plant growth and development in two different soils. Two known bacteria and 12 isolates stimulated growth of winter wheat. Of these, the most effective were nine isolates that significantly (P < 0.01) increased plant height, root and shoot biomass, and number of tillers. The plant growth promoting effects of isolates were different in the two soils. Three of these strains were tentatively classified as Pseudomonas aeruginosa, and two each as Pseudomonas cepacia, Pseudomonas fluorescens, and Pseudomonas putida. Some isolates induced significant increases in seedling emergence rates and (or) demonstrated antagonism in vitro against Rhizoctonia solani and Leptosphaeria maculans. These results demonstrate the potential use of plant growth promoting rhizobacteria as inoculants for winter wheat. Key words: pseudomonads, plant growth promoting rhizobacteria, winter wheat, rhizosphere, bacterial inoculants.
Denitrifïcation in Flexibacter canadensis
Authors: Jones Alison M. , Knowles Roger
Published: May 2010

Denitrifïcation was studied in pure cultures of Flexibacter canadensis (ATCC 29591), a Gram-negative gliding bacterium found in soil. Flexibacter canadensis was capable of using nitrate, nitrite, and nitrous oxide as terminal electron acceptors for growth. Sodium sulfide (200 μM) inhibited all of the nitrogen oxide reductases, but only temporarily. Acetylene (4 kPa) inhibited nitrous oxide reduction but did not affect the reduction of either nitrate or nitrite. However, sulfide (100 and 200 μM) alleviated the acetylene block and permitted reduction of nitrous oxide in the presence of 4 kPa acetylene. These data may have important implications regarding the use of the acetylene inhibition assay for measuring denitrifïcation rates in highly anaerobic, sulfidic environments. Key words: Flexibacter canadensis, denitrification, N2O reductase, sulfide, acetylene.
Binding specificity of the combining site of cholera toxin for human erythrocytes
Authors: Sugii Shunji
Published: May 2010

The reactivity of cholera toxin (CT) with blood-group determinant(s) on human erythrocytes was studied by competitive binding assays. 125I-labeled CT was found to bind more efficiently to pronase- and neuraminidase-treated human type A, B, and O erythrocytes than their untreated ones. The binding of 125I-labeled CT to neuraminidase-treated human type B erythrocytes was effectively inhibited by ganglioside GM1, but not by porcine gastric mucin with both A and H determinants (hog A + H), blood group specific lectins, and other substances at the highest concentrations used. Ganglioside GM1 was at least 105 times more potent than other inhibitors. These findings strongly suggest that the predominant binding substance for CT on human erythrocytes is not the blood-group determinant(s) but ganglioside GM1. Key words: binding specificity, cholera toxin, human erythrocytes.
Osmoregulation in Rhizobium meliloti: characterization of enzymes involved in glutamate synthesis
Authors: Gonzalez-Gonzalez Rigoberto , Botsford James L. , Lewis Thomas
Published: May 2010

Rhizobium meliloti, like many bacteria, accumulates elevated levels of glutamate when osmotically stressed. The biochemical basis for this increase in glutamate production was investigated. Enzymes involved in glutamate synthesis, including glutamine synthetase, glutamate synthase, and glutamic dehydrogenase, were characterized in dialyzed crude cell-free extracts. A transaminase activity, which uses branched chain amino acids for the amination of 2-ketoglutaric acid, was also characterized. With the exception of glutamic dehydrogenase, the specific activity of the enzymes did not vary more than 4-fold in response to the available source of nitrogen or supplemental glutamate. Glutamic dehydrogenase activity was 13-fold greater when cells grew with 10 mM [Formula: see text] than when cells grew with 0.5 mM [Formula: see text]. Glutamate synthase was repressed 2-fold when cells grew with supplemental glutamate. Conversely, this enzyme was derepressed 2× when cells grew with 0.5 mM [Formula: see text] or nitrate. Growing cells in minimal defined medium with 400 mM NaCl to cause osmotic stress had little effect on the specific activity of any of the enzymes. The addition of K+ to the reactions stimulated heat-stable glutamine synthetase activity, but inhibited the other enzymes. Glutamate synthase was inhibited to a limited extent by several intermediates in the Krebs' cycle and very severely by glyoxylate. The addition of 10 mM glutamate to the reaction inhibited glutamate synthase 20%, but had no effect on the other enzymes. Key words: enzymes, glutamate synthesis, osmotic stress.
Products in light-mediated reactions of free methionine-riboflavin mixtures that are biocidal to microorganisms
Authors: Tzeng Dean D. , Lee Miin-Huey , Chung Kuang-Ren , DeVay James E.
Published: May 2010

Solutions of methionine (1 mM) plus riboflavin (26.6 μM) (MR mixture) in the presence of light are toxigenic to a wide spectrum of microorganisms. Agrobacterium tumefaciens and Verticillium dahliae are representative of these microorganisms and were used in this study. The biocidal activity of the MR mixture was significantly enhanced when aerated or supplemented with Cu2+ or Fe2+ ions; the increased toxicity suggested the involvement of the O2−-driven Haber–Weiss reaction, from which the associated production and reactivity of O2−, H2O2, and 1O2 may have contributed to the biocidal activity. Although the presence of EDTA did not lessen the toxicity of the MR mixture, the addition of butylated hydroxyanisole effectively quenched its biocidal activity. Supplementation of MR mixture with antioxidants like α-tocopherol and β-carotene also was effective in reducing its biocidal activity and suggested further that the production of the above-mentioned oxygen species was critical for a photodynamic toxigenic reaction. In addition to the involvement of oxygen derivatives, the role of various methionine photodegradation products in the biocidal reaction was also evaluated. Methional and acrolein were among the methionine-derived components that were toxic. The highest amounts of methional and acrolein detected in the MR reaction system during an 8-h period by HPLC were approximately 46.5 and 10.6 μM, respectively. However, to achieve the toxicity equivalent to that of the MR mixture, the production of more than 5 mM methional or 100 μM acrolein would be necessary. Thus, the overall toxicity of the MR mixture appeared to be associated with the generation of highly reactive oxygen radicals. Key words: methionine–riboflavin mixture, photodynamic toxicity, methional, acrolein, activated oxygen derivatives, Agrobacterium tumefaciens, Verticillium dahliae.
Survival and inoculum potential of conidia and chlamydospores of Fusarium oxysporum f.sp. lini in soil
Authors: Couteaudier Yvonne , Alabouvette C.
Published: May 2010

The kinetics of survival and inoculum potential of Fusarium oxysporum f. sp. lini were studied in soil. Two types of inoculum were compared: microconidia freshly harvested from a laboratory-grown culture and microchlamydospores produced in sterilized soil. Introduced at the same inoculum densities into a natural soil, the two types of inoculum showed similar behaviour; the inoculum densities changed little with time, at least during 100 days. However, the two types of inoculum did differ in disease potential. A higher percentage of microchlamydospores than microconidia germinated in the rhizosphere of flax seedlings, and the heterotrophic fluorescein diacetate hydrolysing activity of the microchlamydospores was 100 times higher than that of microconidia. Moreover, the microchlamydospores produced more disease on flax than the microconidia even at a much lower inoculum density. Key words: survival, inoculum potential, enzymatic activity, conidia, chlamydospores, Fusarium oxysporum, soil.
Effects of ozone treatment on the infectivity of hepatitis A virus
Authors: Vaughn James M. , Chen Yu-Shiaw , Novotny James F. , Strout Deborah
Published: May 2010

The inactivation of a large-focus-forming variant of hepatitis A virus (HM-175) by ozone was investigated. Experiments using mainly single-particle virus preparations suspended in phosphate–carbonate buffer were conducted over a range of pH levels (6–8) at 4 °C. Viral enumerations involved the use of a radioimmunofocus assay. While some tolerance to lower (i.e., 0.1–0.5 mg/L) ozone residuals was noted, the exposure of virus particles to ozone concentrations of 1 mg/L or greater at all pH levels resulted in their complete (5 log) inactivation within 60 s. The pH-related effects that were observed were not considered to be significant. Key words: hepatitis A virus, ozone, disinfection.
Study of the antigenic relationships between strains of Bacteroides. intermedius, B. melaninogenicus, B. corporis, and B. denticola revealed by immunoblotting with rabbit antisera
Authors: Bowden G. H. , Nolette N.
Published: May 2010

Antigen profiles of saccharolytic oral black-pigmented Bacteroides have been developed by Western blotting. Visual comparisons indicated extensive cross-reactions between B. intermedius, B. melaninogenicus, B. denticola, and B. corporis. Porphyromonas gingivalis, P. asaccharolyticus, and B. buccae showed less cross-reaction. Quantitation of antigenic similarity was made from densitometric scans. Calculation of the Jackard coefficient gave results of 33–72% similarity among the saccharolytic pigmented species, with the two homology groups of B. intermedius separated at 53%. Species were separated below 70%. Subtraction of the profile of a cross-reacting strain from that of the homologous strain also allowed quantitation of similarities. These similarities were lower; the range between species was 4–62%, although the two homology groups of B. intermedius still separated at 50 and 58%. Species were separated below 63%. Sera absorbed with a cross-reacting strain gave reduced reactions with the homologous strain and cross-reacting strains, indicating several common antigens among the four species. The species-specific antigens demonstrated by sera absorbed with cells of cross-reacting species were relatively few (3–6) compared with cross-reacting antigens detected by non-absorbed sera (18–28). The method appears useful to quantitate antigenic similarities among Bacteroides species and strains and allows analysis and quantitation of individual humoral responses in animals to these bacteria. Key words: oral Bacteroides, Porphyromonas, antigenic similarities, immunoblotting.
Molecular size variation of the hemagglutinating adhesin HA-Ag2, a common antigen of Bacteroides gingivalis
Authors: Chandad Fatiha , Mouton Christian
Published: May 2010

The array of Bacteroides gingivalis W83 antigens revealed by crossed Immunoelectrophoresis includes one antigen that is associated with an erythrocyte-binding capacity, termed the hemagglutinating adhesin HA-Ag2. This antigen was excised from crossed-immunoelectrophoresis plates to produce two polyclonal antisera, VL 011 and WL 303, whose restricted specificity for HA-Ag2 was assessed using crossed Immunoelectrophoresis, crossed Immunoelectrophoresis with an intermediate gel, and crossed imunoaffinoelectrophoresis. Both antisera, when used to probe blots of an EDTA cell surface extract of B. gingivalis W83, reacted with two bands, at 33 and 38 kDa, which were also detected by a monoclonal antibody (Naito et al. 1985. Infect. Immun. 50:231–235), specific for a hemagglutinin of B. gingivalis. Antiserum WL 303 was used to examine by immunoblotting the distribution of HA-Ag2 among a variety of human and animal strains of B. gingivalis. All human strains tested showed two major bands at 33 and 38 kDa in the EDTA cell surface extract, and at 43 and 49 kDa in outer membrane preparations. Only one band, at 29 kDa, was detected in EDTA cell surface extracts from the animal strains, while the outer membrane preparation of a single strain showed a positive reaction. We concluded that HA-Ag2 is an antigen common to human and animal strains of B. gingivalis and that its subunits may show heterogeneity in apparent molecular mass. Key words: Bacteroides, EDTA extract, outer membranes, crossed immunoelectrophoresis, immunoblot.
Accumulation of radiocaesium in fungi
Authors: Bakken Lars R. , Olsen Rolf A.
Published: May 2010

The accumulation of radioactive Cs by fungi was studied by analysis of fruit bodies (n (total) = 205, n ≥ 5 for 22 species) collected in 1988 in a Norwegian mountain area with high deposition of radiocaesium from the Chernobyl accident. To account for site variation, the radiocaesium content of soil and plants was determined for each sampling spot. The soil contained 5–600 kBq/m2 (median = 50 kbq/m2, 134Cs + 137Cs). The plant content ranged from 0.25 to 23 Bq/g dry weight (median = 3.1 Bq/g) and was positively correlated with radiocaesium concentration in the soil (r = 0.56) and negatively correlated with soil pH (r = −0.28). The ratio between radiocaesium content in fungi and that in plants at the same spot (F/P) differed among species: 25 species had F/P values between 30 and 270, 12 species had F/P values between 10 and 30, and the rest (16 species) had F/P values below 10 (only four samples had values below 1). The concentration of nonradioactive Cs in fruit bodies was positively correlated with their radiocaesium content. Certain species selectively accumulated one or several trace elements (V, Cd, Hg, Pb, Th). Key words: radioactivity, caesium, fungi, plants, soil.
Soluble factors from rabbit spleen cells kill and lyse Treponema pallidum in vitro
Authors: Fitzgerald Thomas J. , Elmquist Barbara J.
Published: May 2010

Antibody and complement immobilize (kill) Treponema pallidum in vitro. Recent evidence also documents immobilization by soluble factors released by activated macrophages and lymphocytes. Immune-mediated lysis of treponemes, however, has not been reported. The findings in this paper focus on apparent treponemal lysis by rabbit splenic cell preparations. Using cells from animals infected testicularly for 9 to 12 days, unfractionated splenic preparations, as well as adherent and nonadherent preparations, killed and lysed T. pallidum. Phagocytosis alone could not explain the detrimental effects of adherent cells. When cytochalasin B was used to block phagocytosis, decreases in treponemal numbers were still detected. In related studies, immune rabbit sera did not enhance treponemicidal activity of the adherent cells. To assess the specificity of these reactions, T. pallidum was incubated with two monocyte-like cell lines (human U937 and mouse P388D1). Neither cell line was detrimental, and treponemal numbers were not lowered. The soluble nature of the treponemicidal factors from adherent and nonadherent preparations was shown by physically separating these cells from the organisms and demonstrating treponemal killing and lysis. In summary, clearance of T. pallidum from infected tissues is probably at least partially attributed to macrophage phagocytosis. Our findings suggest another mechanism involving lytic factors secreted by activated adherent and nonadherent cells. Key words: syphilis, splenic treponemicidal activity, Treponema pallidum.
Optimization of 7α-hydroxysteroid dehydrogenase production by Escherichia coli 080
Authors: Prabha V. , Gupta Meenakshi , Gupta K. G.
Published: May 2010

7α-Hydroxysteroid dehydrogenase (EC 1.1.1.159) production by Escherichia coli strain 080 was highest when the organism was grown in brain heart infusion broth at pH 6.5 for 72–96 h with shaking at 37 °C. The oxygen consumption rate had a strong effect on the production of this constitutive enzyme. Glucose and lactose at 0.2–0.4%, detergents, and ethylenediaminetetraacetic acid were found to increase the enzyme production. Key words: 7α-hydroxysteroid dehydrogenase, Escherichia coli 080, optimal conditions for 7α-hydroxysteroid dehydrogenase production.
Survival and degradative capacity of Pseudomonas putida induced or constitutively expressing plasmid-mediated degradation of 2,4-dichlorophenoxyacetate (TFD) in soil
Authors: Short Kevin A. , Seidler Ramon J. , Olsen Ronald H.
Published: May 2010

The survival of genetically altered Pseudomonas putida strains harboring an inducible plasmid, pRO101, or a constitutive plasmid, pRO103, was compared. These plasmids encode for the degradation of 2,4-dichlorophenoxyacetate (TFD) to 2-chloromaleylacetate, and the maintenance of either plasmid did not alter survival of P. putida PPO301(pRO101) or PPO301(pRO103) in an unamended agricultural soil. Moreover, in TFD-amended soil, survival of PPO301, PPO301(pRO101), and PPO301(pRO103) was statistically the same after 50 days. Reapplication of TFD to soil 50 days after the original application did not change the numbers of PPO301(pRO101) or PPO301(pRO103), which cannot use TFD as a sole source of carbon. However, a mutant strain, PPO301KS(pRO101), which is able to use TFD as a sole source of carbon, was stimulated by the second addition of TFD: PPO301KS(pRO101) cfu/g soil increased by greater than 20-fold. Although the microbiota indigenous to the study soil was capable of degrading TFD, the addition of plasmid-bearing PPO301 had a dramatic effect on TFD degradation. After 10 days, the concentration of TFD in soil inoculated with plasmid-bearing PPO301 was approximately five times lower (84 ppm) than that in uninoculated soil (435 ppm). In a parallel study, Raphanus sativus (radish) seeds failed to germinate in uninoculated and PPO301-inoculated soil amended with 500 ppm TFD. Seed germination was 53 and 80% in soils inoculated with PPO301(pRO101) and PPO301(pRO103), respectively (P < 0.001). However, the difference in the rate of TFD degradation between the native soil and soil inoculated with plasmid-bearing P. putida was probably related to the relatively high inoculum density of P. putida strains (108 cfu) and the relatively low population density of TFD metabolizers indigenous to the soil. Key words: survival, degradation, plasmid, 2,4-dichlorophenoxyacetate, soil.
Protozoa abundance, growth, and bacterivory in the water column, on sedimenting particles, and in the sediment of Halifax Harbor
Authors: Novitsky James A.
Published: May 2010

The role of protozoan grazing in controlling bacterial populations was examined in four microbial habitats in Halifax Harbor, Canada: the water column, setting particles, the sediment–water interface, and the sediment. Large numbers of protozoans were found in all habitats although most (>56%) were small (<5 μm) flagellates. Protozoans larger than 10 μm were rarely observed; protozoans >20 μm were never observed. Protozoans were also observed to a depth of 9 cm below the sediment surface although efforts to culture viable protozoa failed except for the top 1 cm. The use of the metabolic inhibitor cycloheximide with and without colchicine to selectively inhibit eucaryotic metabolism was shown to severely affect procaryotic metabolism in sediment (and presumably particle and water) samples. Using fluorescently labelled bacteria as food, and under optimum conditions, up to 42% of the Protozoa population exhibited active grazing within 7 h. Using protozoan and bacterial community sizes and doubling times, it was calculated that each protozoan in Halifax Harbor would have to consume 13–118 bacteria per hour for the enumerated nanoplanktonic (<20 μm) Protozoa to be the sole control of the size of the bacterial community. Key words: marine, Protozoa, bacterivory, particles, bacteria.
Hybrid biovars of Agrobacterium species isolated from conifer roots
Authors: Bell C. R. , Ramey W. D.
Published: May 2010

A total of 377 heterotrophic bacteria were isolated on nonselective medium from the rhizoplanes of five species of conifer. The species were western hemlock (Tsuga heterophylla), Douglas-fir (Pseudotsuga menziesii), lodgepole pine (Pinus contorta), white spruce (Picea glauca), and western red cedar (Thuja plicata). Twenty-eight strains from this population were identified as presumptive agrobacteria. All proved nontumourigenic. Principal-component analysis indicated that the strains, which had clustered into two discrete groups, had intermediate biovar characteristics. Cluster 1 was predominately biovar 3/2 in character, cluster 2 was predominately biovar 2/3. All the presumptive agrobacteria were distributed randomly with respect to the tree species. This study demonstrates that agrobacteria, although atypical, do occur in forest soils and attests to the ubiquity of the genus in soil. Key words: Agrobacterium, biovars, crown gall, conifers.
Implantation d'Escherichia coli en pilote expérimental et influence des compétitions de flore
Authors: Guyader Françoise Le , Pommepuy Monique , Cormier Michel
Published: May 2010

Implantation in seawater and (or) sediment of bacterial flora and the influence of such flora upon the survival and growth of an Escherichia coli of human origin have been the object of experimental pilot studies. The selected pilot plant permitted work on large volumes of seawater and sediment, and maintenance of the structure of the latter. Diverse experiments were carried out in the presence or absence of seawater and (or) sediment bacterial flora during 13 days. Escherichia coli bacteria were introduced in the seawater experimental system at concentrations of 1 to 3 × 105 colony-forming units (cfu) per 100 mL. In sterile sediment, E. coli bacteria first went through a proliferative phase and then implanted themselves (3 × 104 cfu/100 g at 0 days and 4 × 105 cfu/100 g at 13days). Diffusion in the supernatant sterile seawater of organic matter released from sediment allowed the strain to proliferate (8 × 106 cfu/100 mL at 1 day) and survive for a few days (1 × 104 cfu/100 mL at 6 days), prior to an ultimate decreasing phase (1 cfu/100 mL at 13 days). In the presence of the seawater indigenous flora, an immediate decrease (2 × 103 cfu/100 mL at 6 days), without a growth or even a survival phase, evidenced a selection pressure. In a nonsterile sediment, in the presence or absence of seawater indigenous flora, E. coli bacteria implanted themselves quickly (5 × 104 cfu/100 g at 1 day) and survived (1 × 104 cfu/100 g at 13 days). In the supernatant seawater, a decrease was observed from the 1st day. Our results show that a state of equilibrium was reached, with E. coli bacteria disappearing from the seawater under the pressure selection created by the indigenous marine flora (an important role of the organic matter), and with a considerable survival in the sediment, whatever the conditions might be. Key words: Escherichia coli, bacterial flora, seawater, sediment, competition. [Translated by the Journal]
Two new genes (smhA and lytE) apparently functionally related to the murH gene of Escherichia coli
Authors: Dai Dexi , Ishiguro Edward E.
Published: May 2010

The murH mutant of Escherichia coli exhibits temperature-sensitive growth and lysis at the restrictive temperature. Temperature-resistant derivatives of the mutant occurred at a frequency of about 3 × 10−6. All of the seven independent isolates examined were shown to be pseudorevertants carrying extragenic suppressors of murH, which mapped at 24.5 min on the linkage map. One allele, apparently representing a new locus, designated smhA, was characterized further. The smhA mutation by itself conferred no recognizable phenotype. However, smhA suppressed the temperature-sensitive lysis phenotype of the murH mutant. The smhA mutant acquired a spontaneous mutation in another new gene, designated lytE, which was mapped at 25 min. The lytE mutation by itself conferred a temperature-sensitive lysis phenotype indistinguishable from that of the murH mutant. The lytE mutation was suppressed by smhA as well as by another suppressor of murH designated smhB. The suppressor activity of smhA was apparently relatively specific in that smhA failed to prevent lysis caused by either mutational or antibiotic-induced blocks in peptidoglycan synthesis. The possibility that the smhA and lytE genes are functionally related to murH is considered. Key words: bacteriolysis, peptidoglycan, smhA, lytE.