bluuebunny/crossref_metadata_2025 huggingface dataset:
Transport mechanism in aluminum nitride-metal multilayer junctions
Authors: Kabulski A. , Korakakis D.
Published: November 2009

The electrical behavior of aluminum nitride (AlN) thin film structures consisting of alternating AlN and platinum (Pt) layers has been studied. Typical single layer AlN thin films are insulating due to the wide bandgap properties of the material, but stacked AlN–Pt structures can be conductive. Conductivity studies of the structures indicate regions of semiconductor behavior as well as regions where tunneling occurs. The thickness of the AlN layers, as well as the number of AlN–Pt interfaces in the structures, is found to impact the conduction and tunneling mechanism. Fowler–Nordheim theory and plots were used to determine trends in the electrical behavior and it was found that the field enhancement factor depends on the total thickness of the AlN layers, while the conduction mechanism, tunneling, or multistep hopping between midbandgap states, depends on the number of interfaces as well.
Effects of Al doping and annealing on chemical states and band diagram of Y2O3∕Si gate stacks studied by photoemission and x-ray absorption spectroscopy
Authors: Toyoda Satoshi , Okabayashi Jun , Komatsu Makoto , Oshima Masaharu , Lee Dong-Ick , Sun Shiyu , Sun Yun , Pianetta Piero A. , Kukuruznyak Dmitry , Chikyow Toyohiro
Published: November 2009

The authors have investigated the effects of Al doping and annealing on the photoemission spectra and thermal stability of Y2O3∕Si gate stacks by photoemission spectroscopy and x-ray absorption spectroscopy. They have found that the SiO2 components diffuse into the Y2O3 layer by annealing, resulting in the formation of Y silicate; however, the formation of metallic Y silicide is not observed. The changes in valence- and conduction-band offsets by doping Y2O3 with Al with respect to both Al concentration and annealing temperature have been systematically investigated. With an increase in the Al concentration, the band offsets and band gaps increase and the conduction-band edges change nonlinearly.
Solvent exposure and cognitive ability at age 67: a follow-up study of the 1947 Scottish Mental Survey
Authors: Dick Finlay D , Bourne Victoria J , Semple Sean E , Fox Helen C , Miller Brian G , Deary Ian J , Whalley Lawrence J
Published: November 2009

Objectives

Organic solvent exposure may be associated with cognitive impairment in later life although the evidence for this association is inconsistent. This study sought to examine the association between organic solvent exposure and cognitive function in later life.

Methods

A prospective longitudinal study set in Aberdeen, Scotland examined 336 men and women born in 1936 who participated in the 1947 Scottish Mental Survey. Cognitive function at age 67 years was measured using the Trail Making Test B (TMT B), the Digit Symbol (DS) test, and the Auditory Verbal Learning Test (AVLT). Occupational hygienists reviewed occupational histories, blind to cognitive function, and estimated lifetime solvent exposures. Multiple regression analyses were employed to explore the association between solvent exposure and cognitive performance after adjustment for confounders.

Results

After adjusting for childhood IQ, smoking, alcohol and sex, the solvent exposed group took on average almost 10 s longer than the unexposed group to complete the TMT B, a highly significant difference. For the DS test, after adjusting for childhood IQ, smoking and gender, the exposed group scored on average two points lower than the unexposed group, which was again highly significant. There was no evidence of an effect for cumulative solvent exposure on the TMT B or DS test. For the AVLT there were no significant differences associated with exposure.

Conclusions

This study of subjects with generally low exposures, found no clear evidence of an association between solvent exposure and cognitive function.
An archaebacterial promoter sequence assigned by RNA polymerase binding experiments
Authors: Thomm Michael , Wich Günter , Brown James W. , Frey Gerhard , Sherf Bruce A. , Beckler Gregory S.
Published: November 2009

To identify an archaebacterial promoter sequence, nuclease protection studies with the purified RNA polymerase of Methanococcus vannielii were performed. The enzyme binds specifically both at protein-encoding (hisA and methyl CoM reductase, component C) and tRNA–rRNA genes. The binding region of the RNA polymerase extends from 30 base pairs (bp) upstream (−30) to 20 bp downstream (+20) from the in vivo transcription start site. This finding indicates that the archaebacterial enzyme recognizes promoters without transacting traascription factors. The DNA segment protected from nuclease digestion by bound RNA polymerase contains an octanucleotide sequence centered at −25, which is conserved between the protein-encoding and the stable RNA genes. According to the specific binding of the enzyme to only DNA-fragments harbouring this motif, we propose the sequence TTTATATA as the major recognition signal of the Methanococcus RNA polymerase. Comparison of this motif with published archaebacterial DNA sequences revealed the presence of homologous sequences at the same location upstream of 36 genes. We therefore consider the overall consensus [Formula: see text] as a general element of promoters in archaebacteria. In spite of the specific binding of the enzyme, most preparations of the Methanococcus vannielii RNA polymerase are unable to initiate transcription at the correct sites in vitro. Here we present first evidence for the possible existence of a transcription factor conferring the ability to the enzyme to initiate and terminate transcription specifically in vitro.Key words: promoter, footprint, TATA box, RNA polymerase, transcription.
Sequence comparison of glyceraldehyde-3-phosphate dehydrogenases from the three urkingdoms: evolutionary implication
Authors: Hensel Reinhard , Zwickl Peter , Fabry Stefan , Lang Jutta , Palm Peter
Published: November 2009

The primary structure of the glyceraldehyde-3-phosphate dehydrogenase from the archaebacteria shows striking deviation from the known sequences of eubacterial and eukaryotic sequences, despite unequivocal homologies in functionally important regions. Thus, the structural similarity between the eubacterial and eukaryotic enzymes is significantly higher than that between the archaebacterial enzymes and the eubacterial and eukarytic enzymes. This preferred similarity of eubacterial and eukaryotic glyceraldehyde-3-phosphate dehydrogenase structures does not correspond to the phylogenetic distances among the three urkingdoms as deduced from comparisons of ribosomal ribonucleic acid sequences. Indications will be presented that the closer relationship of the eubacterial and eukaryotic glyceraldehyde-3-phosphate dehydrogenase resulted from a gene transfer from eubacteria to eukaryotes after the segregation of the three urkingdoms.Key words: glyceraldehyde-3-phosphate dehydrogenase, archaebacteria, protein evolution.
Characterization of the small endogenous plasmid of Halobacterium strain SB3 and its use in transformation of H. halobium
Authors: Hackett Neil R. , DasSarma Shiladitya
Published: November 2009

To study the molecular biology of the halophilic archaebacterium Halobacterium halobium, the introduction of DNA engineered in vitro is desirable. As a first step in developing a cloning vector, the complete 1736 base pair nucleotide sequence of the natural, high copy number, Halobacterium plasmid pHSB1 has been determined. The plasmid was found to show homology to the small plasmids of Halobacterium strains GRB and GN101. Plasmid pHSB1 encodes a 317 amino acid protein of unknown function. The related halophile, H. halobium, could be transformed by pHSB1, demonstrating its utility as the basis of a cloning vector.Key words: archaebacteria, Halobacterium, plasmid.
A comparison of the methyl reductase genes and gene products
Authors: Weil Clifford F. , Sherf Bruce A. , Reeve John N.
Published: November 2009

The DNA sequences encoding component C of methyl coenzyme M reductase (mcr genes) in Methanothermus fervidus, Methanobacterium thermoautotrophicum, Methanococcus vannielii, and Methanosarcina barkeri have been published. Comparisons of transcription initiation and termination sites and of the amino acid sequences of the mcr gene products are presented. Structural features conserved within the amino acid sequences are identified and a comparison of methyl reductase with other disulfide bond synthesizing enzymes is presented.Key words: archaebacterium, methanogen, methyl reductases, gene cloning, heterodisulfide synthesis.
Regulation of the bacterio-opsin gene of a halophilic archaebacterium
Authors: Betlach Mary C. , Shand Richard F. , Leong Diane M.
Published: November 2009

The protein bacterio-opsin, complexed with retinal, functions as a light-driven proton pump in the purple membrane of the halophilic archaebacterium, Halobacterium halobium. Bacterio-opsin deficient mutants have been characterized in attempts to elucidate regulation of the gene encoding bacterio-opsin (bop). Analysis of the mutational defect in Bop mutants has revealed the existence of at least two genes that affect bop gene expression and (or) purple membrane formation: (i) the brp gene, located 526 base pairs upstream of the bop gene, is transcribed in the opposite orientation, and (ii) the bat gene, located 1602 base pairs upstream of the bop gene, is transcribed in the same orientation as the brp gene. The bat gene start codon overlaps the stop codon of the brp gene. The bat gene could encode an acidic protein of 73 000 Da (674 amino acids) with a predicted secondary structure typical of a soluble alpha–beta type protein. This type of secondary structure is in contrast to the hydrophobic structure predicted for the putative brp protein. Transcriptional analyses of the wild type, 11 Bop mutants, and a Bop revenant suggest that the bat gene has a more direct role than the brp gene in bop gene expression and is involved in activating bop and brp gene expression.Key words: purple membrane, bacterio-opsin, bop gene cluster, transcripts, activator.
The expression of the superoxide dismutase gene in Halobacterium cutirubrum and Halobacterium volcanii
Authors: May Bruce P. , Tam Patrick , Dennis Patrick P.
Published: November 2009

The gene encoding the Mn-containing superoxide dismutase (SOD) from Halobacterium cutirubrum has been cloned and sequenced. The deduced amino acid sequence is homologous to the sequences of Fe and Mn SODs from eubacteria. The high degree of amino acid identity between the archaebacterial and eubacterial proteins suggests that a SOD gene may have been laterally transferred between eubacteria and archaebacteria sometime after the accumulation of atmospheric oxygen. Consensus elements of halobacterial promoters are found upstream of the coding region, however, the spacing between them and the transcription start site is greater than in other genes. Termination of transcription occurs in five consecutive T residues that are preceded by a GC-rich sequence that has short inverted repeats. In addition to the authentic SOD gene, H. cutirubrum also contains a putative pseudogene. The SOD levels and growth rates of H. cutirubrum and Halobacterium volcanii were tested in response to treatment by paraquat, an intracellular generator of superoxide. In H. volcanii the growth rate slowed, and SOD was strongly induced throughout prolonged treatment with paraquat. In H. cutirubrum the same effects were noticed initially, but after 48 h exposure to the drug, the growth rate increased and the SOD level decreased. Production of paraquat resistant mutants of H. cutirubrum may play a part in this process, however, some type of physiological adaptation is also probably required.Key words: archaebacteria, oxygen radicals, paraquat.
Presence of an intron in elongator methionine-tRNA of Halobacterium volcanii
Authors: Datta Prasun K. , Hawkins Lynda K. , Gupta Ramesh
Published: November 2009

The gene for the elongator (internal) methionine transfer RNA [Formula: see text] in the archaebacterium Halobacterium volcanii contains a 75 base pair intron (intervening sequence) and lacks the 3′-terminal CCA sequence of the mature tRNA. There is a single copy of this gene in the genome and it is expressed. Northern hybridization experiments indicate that the precursor is processed to produce mature tRNA and a free intron species. A secondary structure of the transcript can be formed in which the anticodon stem of the tRNA is extended. Two symmetrically placed three-base bulge loops separated by a 4 base pair stem are present in this extension. The cleavage sites for the removal of the intron are placed between the middle and 3′ residues of these loops.Key words: archaebacteria, methionine-tRNA, intron, splicing.
Gene organization and structure of two transcriptional units from Methanococcus coding for ribosomal proteins and elongation factors
Authors: Auer Johannes , Lechner Konrad , Bock August
Published: November 2009

Two transcriptional units coding for ribosomal proteins and protein synthesis elongation factors in Methanococcus vannielii have been cloned and analysed in detail. They correspond to the "streptomycin operon" and "spectinomycin operon" of the Escherichia coli chromosome. The following general conclusions can be drawn from comparison of the nucleotide and the derived amino acid sequences of ribosomal proteins from Methanococcus with those from eubacteria and eukaryotes. (i) Ribosomal protein and elongation factor genes in Methanococcus are clustered in transcriptional units corresponding closely to E. coli ribosomal protein operons with respect to both gene composition and organization. (ii) These transcriptional units contain, in addition, a few open reading frames whose putative gene products share sequence similarity with eukaryotic 80S but not with eubacterial, ribosomal proteins. They may correspond to "additional" ribosomal proteins of the Methanococcus ribosome, there being no functional homologues in the eubacterial ribosome. (iii) Methanococcus ribosomal proteins and elongation factors almost exclusively exhibit a higher sequence similarity to eukaryotic 80S ribosomal proteins than to those of eubacteria. (iv) Many Methanococcus ribosomal proteins have a size intermediate between those of their eukaryotic and eubacterial homologues. These results are discussed in terms of a hypothesis which implies that the recent eubacterial ribosome developed by a "minimization" process from a more complex organelle and that the archaebacterial ribosome has maintained features of this ancestor.Key words: archaebacteria, Methanococcus, transcription factors, clonal analysis.
Halobacterium sp. GRB: a species to work with!?
Authors: Soppa J. , Oesterhelt D.
Published: November 2009

The properties of the halobacterial isolate Halobacterium sp. GRB are discussed, especially in relation to its use as a laboratory strain. Experimental results on this species are described, including the isolation of point mutants in the bacterioopsin gene leading to single amino acid replacements in bacteriorhodopsin, the application of a selection procedure for the isolation of different types of mutants, the genetic stability of Halobacterium sp. GRB and the possibility of isolating a set of isogenic mutants, the conditions for transformation experiments with this species, and specific features of Halobacterium sp. GRB, such as halocin production and the absence of a restriction system, as well as DNA adenosine methylation.Key words: halobacteria, Halobacterium sp. GRB, in vivo mutagenesis, 5-bromo-2′-deoxyuridine selection, bacteriorhodopsin.
Comparison of transfer RNA and ribosomal RNA intron splicing in the extreme thermophile and archaebacterium Desulfurococcus mobilis
Authors: Kjems Jørgen , Jensen Jonna , Olesen Tina , Garrett Roger A.
Published: November 2009

The structure of the exon–intron boundary was compared for an intron within 23S ribosomal RNA of Desulfurococcus mobilis and a newly discovered intron in tRNAMet from the same organism. The occurrence of a putative common structural feature suggests that intron excision occurs by the same mechanism. The possible recognition of this structural feature by the cleavage enzyme was investigated for the ribosomal RNA intron using RNA substrates exhibiting various exon and intron deletions. The results support the involvement of the structural features in the cleavage process. The evolutionary implications of these results are considered.Key words: archaebacteria, tRNA, ribosomal RNA, introns, intron evolution.
Physiological studies on the growth and utilization of sugars by Listeria species
Authors: Pine L. , Malcolm G. B. , Brooks J. B. , Daneshvar M. I.
Published: November 2009

Experiments, relevant to growth in milk, were done to delineate the aerobic and anaerobic growth of Listeria species on selected sugars in several media. All species grew on glucose aerobically, forming lactic acid and (or) acetic acid. Anaerobically, only lactic acid was formed; cell yields were 80% of those obtained aerobically. When incubated aerobically, small amounts (1.5 μm/mL) of isovaleric acid, 2-hydroxyisovaleric acid, and trace amounts of isobutyric acid were formed. These products were characteristically formed by 26 strains representing all the species of Listeria. Added leucine stimulated isovaleric acid formation. Anaerobic fermentations of glucose could be followed by 60 to 80% cell lysis; less lysis occurred in air. Anaerobically, only hexoses and pentoses supported growth; aerobically, maltose and lactose supported growth of some strains, but sucrose did not support growth of any strain tested. Listeria grayi and Listeria murrayi utilized the galactose and glucose moieties of lactose for growth; Listeria monocytogenes and Listeria innocua used only the glucose moiety. Glucosamine and N-acetylglucosamine supported aerobic and anaerobic growth as well as glucose, and their presence stimulated the utilization of lactose by "lactose-negative" strains. Analyses of cultures grown at 5 °C in sterile milk treated with glucose oxidase supported the conclusion that the glucose of the milk was the major, if not the limiting, substrate that supported growth.Key words: Listeria, growth, sugar use.
Fungi colonizing preservative-treated Douglas-fir poles after remedial treatment with fumigants
Authors: Giron Magdalena Y. , Morrell Jeffrey J.
Published: November 2009

The microfungi present in transmission poles of preservative-treated Douglas-fir remedially treated with one of four fumigants were determined by removing increment cores 5 and 15 years later and culturing them on nutrient media. The microfungi isolated from the wood were then characterized according to their ability to cause a loss in wood weight, to tolerate conventional wood preservatives, and to tolerate wood fumigants. The wood treated with fumigants 5 years earlier was sparsely colonized, while that treated 15 years earlier was colonized more heavily. In general, many of the same species of microfungi occurred in treated and untreated poles. In both, fungal populations were dominated by Scytalidium and Trichoderma spp. None of the isolates caused losses in wood weight greater than 5%, but several exhibited tolerance to short fumigant exposures. The latter trait may help explain the presence of these fungi in wood still containing measurable levels of fumigant. The presence in fumigant-treated wood of fungi previously shown to be antagonistic toward wood decay fungi may help explain the ability of the four test fumigants to provide long-term protection.Key words: fungi, Scytalidium, Trichoderma, colonization, Douglas-fir.
Mapping of transfer and H pilus coding regions of the IncHII plasmid pHH1508a
Authors: Yan William , Taylor Diane E.
Published: November 2009

The IncHII plasmid pHH1508a (208 kilobases) encodes resistance to potassium tellurite, trimethoprim, and streptomycin. Conjugative pili encoded by pHH1508a were isolated, purified, and used for preparation of anti-H pilus antiserum. Immuno-gold labelling experiments using H pilus specific antiserum showed that antigenic determinants were located along the entire length of the H pilus. Immuno-gold labelling and lysis studies using pilHα, a bacteriophage specific for H pili, were used to investigate transfer-deficient mutants of pHH1508a obtained by Tn5 mutagenesis and an in vitro constructed derivative of 96 kilobases, pDT1178, which also conferred resistance to potassium tellurite, trimethoprim, and streptomycin. The transfer-deficient mutants did not specify H pili, whereas pDT1178, which transferred at low frequency (1 × 10−4 transconjugants per recipient), specified a small number of H pili. A naturally occurring plasmid, pMG110, was found to encode the production of H pili, but was completely transfer deficient (< 1 × 10−7 transconjugants per recipient). This study suggests that genes required for H pilus production and assembly as well as low level transfer are located separately within the 96-kilobase fragment of pDT1178 and that other genes, located outside this region, are essential for the regulation and full expression of conjugative transfer.Key words: plasmid, incompatibility, mapping, antibiotic, resistance.
Purification and properties of three endopeptidases from baker's yeast
Authors: Nowak Jerzy , Tsai Hsin
Published: November 2009

Three endopeptidases, proteinases A, B, and Y, were purified from baker's yeast, Saccharomyces cerevisiae. Two molecular forms of proteinase A (PRA), Mr 45 000 and 54 000, (estimated on SDS-PAGE) were obtained. Both forms were inhibited by pepstatin and other acid proteinase inhibitors. The enzyme digested hemoglobin most rapidly at pH 2.7–3.2 and casein at pH 2.4–2.8 and 5.5–6.0. The optimum pH for hydrolysis of protein substrates could be shifted to about 5 with 4–6 M urea. Urea also stimulated the enzyme activity by 30–50%. As other acid proteinases, the enzyme preferentially cleaved peptide bonds of X–Tyr and X–Phe type. A proteinase B (PRB) preparation of approximately Mr 33 000 possessed milk clotting activity and showed an inhibition pattern typical for seryl-sulfhydryl proteases. The purified enzyme could be stabilized with 40% glycerol and stored at −20 °C without significant loss of activity for several months. The third endopeptidase, designated PRY, of Mr 72 000 when estimated by Sephadex G-100 gel filtration, had properties resembling PRA and PRB. Similar to PRB, it could be inhibited by up to 90% with phenylmethylsulfonyl fluoride and para-chloromercuribenzoate and preferentially hydrolyzed the Leu15–Tyr16 peptide bond of the oxidized β-chain of insulin. On the other hand, contrary to PRB, it had neither milk clotting activity nor esterolytic activity toward N-acetyl-L-tyrosine ethyl ester and N-benzoyl-L-tyrosine ethyl ester and was stable during storage at −20 °C without glycerol. The enzyme also showed a lower pH optimum for hydrolysis of casein yellow than PRB. Similar to PRA, 4 M urea shifted its pH optimum for hydrolysis of protein substrates. PRY degraded apo-aminopeptidase Y much more efficiently than PRB or a PRA–PRB mixture. The possibility of PRY being a precursor form of PRA and PRB is discussed.Key words: yeast, endopeptidase, proteinase, purification.
Effets de la carence en sodium sur la cytologie de la cyanobactérie Anabaena cylindrica Lemm
Authors: Roussard-Jacquemin Monique
Published: November 2009

The effects of sodium deficiency on the distribution and the ultrastructural aspect of the various cell types in the filaments were studied during growth of Anabaena cylindrica (strain 1403/2A) in presence of different amounts of nitrate (0, 1 or 10 mequiv./L). Visible symptoms such as chlorosis and reduced growth were clearly apparent several days after inoculation only when nitrate was present in the medium. The filaments broke up and contained exclusively vegetative cells rich in polyglucan granules and showing ultrastructural analogies with akinetes. In absence of sodium increasing nitrate uptake and nitrite efflux were observed in nitrate-enriched cultures (10 mequiv./L). The amount of excreted nitrite was too low to explain the described disturbances. The needs for sodium were lower for cultures without added nitrate. However, whatever the medium, the sodium deficiency brought about a delay in heterocyst differentiation without detrimental effect to the further development of cultures.Key words: cyanobacterium, Anabaena cylindrica, sodium deficiency, heterocyst differentiation, akinete differentiation, ultrastructural changes, nitrate uptake, nitrite efflux.
Seasonal changes in heterotrophic bacteria under fast ice near Syowa station, Antarctica
Authors: Satoh Hiroo , Fukami Kimio , Watanabe Kentaroo , Takahashi Eiji
Published: November 2009

Seasonal changes in the number of heterotrophic bacteria and the species composition of their communities were investigated in the fast ice area of Syowa station (69°00′S, 39°35′E), from May 1983 to January 1984. Numbers of heterotrophic bacteria under the fast ice began to increase in October and the maximum number of colony-forming units/mL (2.4 × 102) were obtained in late December. The changes in bacterial numbers coincided well with those of particulate organic carbon, suggesting that the growth of heterotrophic bacteria depends on the supply of particulate organic carbon from ice algal assemblages which grow rapidly at the bottom of sea ice during the austral spring. Vibrionaceans in the communities in September accounted for as much as 35% of the isolates, whereas in December, they were not detected at all. These results indicate that there is a seasonal succession in the bacterial communities between September and December.Key words: heterotrophic bacteria, vibrionaceans, fast ice, Antarctica.
Infectivity-deficient vesicular stomatitis virus produced in the presence of interferon has a functional virion core
Authors: Jay Francis T. , Dawood Magdy R. , Luk Sandy K. S.
Published: November 2009

Interferon induces two antiviral actions against vesicular stomatitis virus by (i) inhibiting viral protein synthesis which leads to a reduction in virion production, and (ii) producing progeny which are deficient in infectivity (VSV1F). At low or physiological concentrations of interferon, while the virion production was decreased by less than 10-fold, the virion infectivity yield was suppressed more than 1000-fold. The VSVIF was found to be deficient (quantitatively) in envelop glycoprotein G and protein M. Tryptic peptide mapping indicated mat there was no detectable structural abnormality in the G, M, and N proteins of VSVIF. The virion cores, lacking only the envelop G protein, isolated from VSVIF and control VSV have essentially identical specific infectivity. This indicated that the virion proteins L, N, NS, and M, as well as viral RNA that make up the virion core, must be functionally normal, and the observed deficiency in G protein was likely to be the cause of the functional deficiency of the virion. Low concentrations of DEAE-dextran, which is known to partially overcome the virion's dependence on the G protein for adsorption to the cell during infection, were found to enhance the infectivity of VSVIF more than the control virion. These results together indicated that the loss of infectivity in the VSV1F was due to the deficiency of the surface glycoprotein G.Key words: interferon, vesicular stomatitis virus, defective virions.
Ultrastructural study of galacturonic acid distribution in some pathogenic fungi using gold-complexed Aplysia depilans gonad lectin
Authors: Benhamou Nicole
Published: November 2009

Aplysia gonad lectin, isolated from the mollusc Aplysia depilans, was successfully conjugated to colloidal gold and used for ultrastructural detection of galacturonic acids in some pathogenic fungi. These sugar residues were found to occur in the fibrillar sheath surrounding hyphal cells of Ascocalyx abietina and in intravacuolar dense inclusions of this fungus spores. In hyphae and spores of Ophiostoma ulmi, galacturonic acids were detected mainly in the outermost wall layers. In contrast, these saccharides appeared associated with the innermost wall layers and especially the plasma membrane of Verticillium albo-atrum cells. Galacturonic acids were found to be absent in cells of Fusarium oxysporum f.sp. radicis-lycopersici and Candida albicans. These cytochemical data indicate therefore that a heterogeneity in wall composition exists between ascomycete fungi. The significance of the presence of galacturonic acids in the cell walls of certain fungi is still open to question.Key words: galacturonic acid, fungi, gold labeling, Aplysia depilans gonad lectin.
Comparative analysis of the transferrin and lactoferrin binding proteins in the family Neisseriaceae
Authors: Schryvers Anthony B. , Lee B. Craig
Published: November 2009

Intact cells of several bacterial species were tested for their ability to bind human transferrin and lactoferrin by a solid-phase binding assay using horseradish peroxidase conjugated transferrin and lactoferrin. The ability to bind lactoferrin was detected in all isolates of Neisseria and Branhamella catarrhalis but not in isolates of Escherichia coli or Pseudomonas aeruginosa. Transferrin-binding activity was similarly detected in most isolates of Neisseria and Branhamella but not in E. coli or P. aeruginosa. The expression of transferrin- and lactoferrin-binding activity was induced by addition of ethylenediamine di-o-phenylacetic acid and reversed by excess FeCl3, indicating regulation by the level of available iron in the medium. The transferrin receptor was specific for human transferrin and the lactoferrin receptor had a high degree of specificity for human lactoferrin in all species tested. The transferrin- and lactoferrin-binding proteins were identified after affinity isolation using biotinylated human transferrin or lactoferrin and streptavidin–agarose. The lactoferrin-binding protein was identified as a 105-kilodalton protein in all species tested. Affinity isolation with biotinylated transferrin yielded two or more proteins in all species tested. A high molecular mass protein was observed in all isolates, and was of similar size (approximately 98 kilodaltons) in all species of Neisseria but was larger (105 kilodaltons) in B. catarrhalis.Key words: iron, Neisseria, transferrin, lactoferrin, receptor.
2-Oxoaldehyde metabolism in microorganisms
Authors: Murata Kousaku , Inoue Yoshiharu , Rhee Hae-ik , Kimura Akira
Published: November 2009

The properties of methylglyoxal-metabolizing enzymes in prokaryotic and eukaryotic microorganisms were studied systematically and compared with those of mammalian enzymes. The enzymes constitute a glycolytic bypass and convert methylglyoxal into pyruvate via lactate. The first step in this conversion is catalyzed by glyoxalase I, methylglyoxal reductase, or methylglyoxal dehydrogenase. The regulation of the yeast glyoxalase system was analyzed. The system was closely related to the proliferative states of yeast cells, the activity of the system being high in dividing cells and low in nondividing ones. The gene for the glyoxalase I of Pseudomonas putida and the genes responsible for the activity of glyoxalase I and methylglyoxal reductase in Saccharomyces cerevisiae were cloned and their structural and phenotypic characters studied.Key words: 2-oxoaldehydes metabolism, regulation of glyoxalase system, cloning, glyoxalase I gene, methylglyoxal reductase gene, methylglyoxal metabolism.
Characterization of pyrimidine metabolism in the cellular slime mold, Dictyostelium discoideum
Authors: Wales Melinda E. , Mann-Dean Mary G. , Wild James R.
Published: November 2009

The arginine-independent, de novo biosynthetic pathway of pyrrolidines in Dictyostelium discoideum is initiated by a class II carbamoyl-phosphate synthetase (EC 6.3.5.5) specific for pyrimidine biosynthesis which utilized L-glutamine as its N donor and was partially inhibited by both UTP and CTP. The second step in the de novo pathway was provided by an unregulated aspartate transcarbamoylase (EC 2.1.3.2) which primarily appeared as a multimeric enzyme of 105 kilodaltons. The next enzyme, dihydroorotase (EC 3.5.2.3), was approximately 90–100 kilodaltons. Although the early enzymatic activities of the pyrimidine pathway appeared to reside in independent protein complexes, various unstable molecular species were observed. These structural variants may represent proteolytic fragments of a multienzyme complex. In addition to de novo synthesis, the amoeba demonstrated the capacity for salvage utilization of uracil, uridine, and cytidine. Upon starvation on a solid substratum, axenically grown amoebas began a concerted developmental program accompanied by a restructuring of nucleotide metabolism. The absolute levels of the ribonucleotide pools droppedby 98% within 30 h; however, both the adenylate energy charge and the GTP/ATP ratios were maintained for 50 h after the initiation of development. The maintenance of these metabolic energy parameters required the tight cell–cell contact necessary for development, and the capacity for pyrimidine metabolism was maintained throughout developmental morphogenesis.Key words: aspartate transcarbamoylase, carbamoyl phosphate synthetase, development, pyrimidine biosynthesis.
Isolation and preliminary characterization of a 2-chlorobenzoate degrading Pseudomonas
Authors: Sylvestre Michel , Mailhiot Karen , Ahmad Darakhshan , Massé Robert
Published: November 2009

Pseudomonas sp. strain B-300, which is able to utilize 2-chlorobenzoic acid, was isolated from a soil sample by enrichment culture. This strain was shown to grow on 2-chlorobenzoic acid and to completely degrade the substrate with concomitant chlorine ion release. Concentrations of 2-chlorobenzoic acid higher than 0.5% (w/v) were toxic to the cells. Our study also suggested that in the presence of glucose, 2-chlorobenzoic acid is converted to catechol or chlorocatechol; these are in turn transformed to muconic and chloromuconic acid, respectively, suggesting a repression by glucose of some of the degradation pathway enzymes. A similar scheme was already described for 3-chlorobenzoate degradation by pAC25 plasmid.Key words: 2-chlorobenzoate, biodegradation, catabolism, metabolism, Pseudomonas.
Distribution of spermine in bacilli and lactic acid bacteria
Authors: Hamana Koei , Akiba Teruhiko , Uchino Fuji , Matsuzaki Shigeru
Published: November 2009

Obligate moderately thermophilic bacilli and obligate moderately thermoacidophilic bacilli contained spermine as the major polyamine in addition to putrescine and spermidine. The identity of spermine was confirmed by thin-layer chromatography and high-performance liquid chromatography before and after treatment with putrescine oxidase. Using these methods, thermospermine and spermine can be separated; thermospermine was not present in these organisms. On the other hand, various facultative thermophiles and mesophilic strains of the genus Bacillus, including alkalophiles and halophiles, lack spermine and other tetraamines. No spermine was detected in several strains of mesophilic or facultative slightly thermophilic lactic acid bacteria, Lactobacillus and Streptococcus.Key words: polyamine, spermine, Bacillus, Lactobacillus, Streptococcus.
Isolation from soil of Rhizobium leguminosarum lacking symbiotic information
Authors: Soberón-Chávez Gloria , Nájera Rebeca
Published: November 2009

Bacteria resembling Rhizobium leguminosarum, but lacking symbiotic information, were isolated from soil of two different geographical origins. One of these bacteria belongs to a previously described Rhizobium leguminosarum bv. phaseoli somatic serogroup, is fully complemented for nodulation and nitrogen fixation by an R. leguminosarum bv. phaseoli symbiotic plasmid, and is able to compete for bean nodulation with indigenous R. leguminosarum bv. phaseoli strains. This is the first report giving evidence for persistence in soil of Rhizobium lacking symbiotic information.Key words: Rhizobium ecology, symbiotic plasmid, nodulation, plasmid transfer.
Decomposition of cotton by Trichoderma species: influence of temperature, soil type, and nitrogen levels
Authors: Widden Paul , Cunningham John , Breil Brenda
Published: November 2009

The effect of temperature on the ability of five species of Trichoderma to decompose cellulose was evaluated in three types of sterilized soils. The loss in tensile strength of cotton strips was used as an index of cellulose decomposition. The influence of levels of nitrogen on cotton degradation was also evaluated using silica sand as a substitute for soil. A greater loss in cotton tensile strength was obtained with T. virens and T. viride than with T. hamatum, T. polysporum, or T. koningii. All species responded similarly to nitrogen levels and temperature, with decreased activity at low nitrogen and low temperature. The soil also had a large influence on the rate of decomposition of the strips. The soil from a maple forest gave rise to greater losses in tensile strength than did soil from a white pine or Norway spruce plantation. These results emphasize the importance of the soil chemistry in determining fungal activities in the field, and the difficulties of extrapolating results of cellulose utilization studies in the laboratory to the field.Key words: Trichoderma, cellulolysis, soil, nitrogen, temperature.
Thermal and water source effects upon the stability of enteroviruses in surface freshwaters
Authors: Hurst Christon J. , Benton William H. , McClellan Kim A.
Published: November 2009

The long-term survival of three human enterovirus serotypes, Coxsackievirus B3, echovirus 7, and poliovirus 1 was examined in samples of surface freshwater collected from five sites of physically different character. These were an artificial lake created by damming a creek, a small groundwater outlet pond, both a large- and a medium-sized river, and a small suburban creek. Survival was studied at temperatures of −20, 1, and 22 °C. The average amount of viral inactivation was 6.50–7.0 log10 units over 8 weeks at 22 °C, 4–5 log10 units over 12 weeks at 1 °C, and 0.4–0.8 log10 units over 12 weeks at −20 °C. The effect of incubation temperature upon viral inactivation rate was statistically significant (p < 0.00001). As determined by pairing tests, survival was also significantly related to both viral serotype and water source at each of the three incubation temperatures (p ≤ 0.05). Efforts were made to determine whether the rate of viral inactivation observed at the different incubation temperatures was related to characteristics inherent to the water that was collected from the different locations. The characteristics examined included physical and chemical parameters, indigenous bacterial counts, and the amount of bacterial growth that the waters would support (measured as the maximum number of generations which seeded bacteria could undergo after being placed into either pasteurized or sterile-filtered water samples). Analysis of viral inactivation rate versus these characteristics revealed three apparent effectors of viral persistence. These were (i) hardness and conductivity, both of which strongly correlated with one another; (ii) turbidity and suspended solids content, both of which strongly correlated with one another; and (iii) the number of generations of bacterial growth that a sample was capable of supporting, which also correlated with hardness and conductivity.Key words: virus, survival, inactivation rate, water.
Evidence for proton motive force dependent transport of selenite by Clostridium pasteurianum
Authors: Bryant Richard D. , Laishley Edward J.
Published: November 2009

The proton motive force mediated the transport of selenite [Formula: see text] in Clostridium pasteurianum cells by proton symport. The proton conductor, carbonyl cyanide m-chlorophenylhydrazone, inhibited [Formula: see text] uptake while N,N′-dicyclohexylcarbodiimide prevented [Formula: see text] uptake by presumably inhibiting the unidirectional ATPase. Acid pulse studies and antibiotic experiments with valinomycin suggest that the transmembrane ΔpH component of the proton motive force mediated the transport of [Formula: see text] into the cells. The [Formula: see text] porter system in C. pasteurianum was found to be dependent upon energy source, temperature, and medium pH.Key words: proton motive force, anion transport, selenite, Clostridium pasteurianum.
Cloning and expression of Xylella fastidiosa antigens in Escherichia coli and Erwinia stewartii
Authors: Goodwin Paul H.
Published: November 2009

Xylella fastidiosa DNA, partially digested with Sau3A, was ligated into the cosmid vector, pUCD615. Approximately 4500 ampicillin-resistant Escherichia coli colonies were obtained. The frequency of complementation of leucine auxotrophy in transfected E. coli indicated that the cosmid gene bank was representative of X. fastidiosa genomic DNA. Colonies were lysed directly onto nitrocellulose membranes using a thermo-inducible λ lysogen and screened for expression of X. fastidiosa antigens. Approximately 16.5% of a random sample of clones were found to express X. fastidiosa antigens as determined by Western blots. These proteins comigrated with proteins of X. fastidiosa and ranged in molecular weight from 10 000 to 160 000. Conjugation of several of the plasmids into Erwinia stewartii resulted in expression of the similar molecular weight cloned proteins with similar levels of expression as in E. coli.Key words: Xylella fastidiosa, Pierce's disease, immunological clone screening, thermo-inducible lysogeny.
Invasion of HeLa cells by β-hemolytic group G streptococci
Authors: Nath Swapan K.
Published: November 2009

The invasion of HeLa cells by β-hemolytic Lancefield group G streptococci was studied by measuring the number of bacterial cells that survive exposure to gentamicin. Approximately 50% of bacteria introduced to the HeLa cell monolayer survived gentamicin treatment, suggesting that they were intracellular. Electron microscopy of these preparations showed intracellular bacteria in the cytoplasm, not surrounded by host cell membranes. Trypsinized bacteria incubated with HeLa cells were all killed by gentamicin. It appears that the β-hemolytic group G streptococci have mechanisms for entry into human epithelial cells which may have importance in the virulence of the organisms.Key words: Virulence, invasion, HeLa cells, β-hemolytic, streptococci.
A nonsclerotial pathogenic mutant of Sclerotinia sclerotiorum
Authors: Miller R. Vincent , Ford Eugene J. , Sands David C.
Published: November 2009

A nonsclerotial mutant of Sclerotinia sclerotiorum was produced by mutagenesis with 8-methoxypsoralen and ultraviolet light. The mutant, SL-1, failed to produce sclerotia on artificial media, infested grain, or on infected plants. The mutant remained pathogenic to eight plant species susceptible to the wild-type parental strain of the fungus. The mutant, SL-1, is potentially useful for physiological studies on sclerotial development and for investigation of its potential for biological weed control.Key words: Sclerotinia, mutant, sclerotialess, biocontrol, weeds.
Iodine sensitivity of bacteria isolated from iodinated water systems
Authors: Pyle Barry H. , McFeters Gordon A.
Published: November 2009

Fourteen bacterial isolates, predominantly Pseudomonas sp., from two water systems disinfected by iodinated anion-exchange resins were studied and compared with an isolate of Pseudomonas aeruginosa from a povidone-iodine solution and four other isolates. Pseudomonas cepacia and P. aeruginosa grown in brain heart infusion were 3 to 5 logs less sensitive to 1 mg/L I2 (pH 7.2, 1 min) when compared with cultures grown in phosphate buffer. Another P. cepacia isolate was the least sensitive culture when grown in brain heart infusion (1 log decrease) but was more sensitive after cultivation in phosphate buffer (5 logs). Isolates from an iodinated potable water system, including P. cepacia, Staphyloccus warneri, and a Bacillus sp., were all less sensitive to iodine than a "resistant" P. aeruginosa and three other isolates when grown in brain heart infusion. A clinical isolate of P. aeruginosa exhibited intermediate sensitivity. The sensitivity of bacteria to iodine is thus highly variable, depending on the organism as well as the growth conditions.Key words: iodine, disinfection, water.
Production and characterization of neutralizing monoclonal antibodies against poliovirus type 1, 2, and 3
Authors: Payment Pierre , Trudel Michel , Thibodeau Lise , Lecomte Jacqueline
Published: November 2009

Neutralizing monoclonal antibodies were produced against a reference vaccine or a reference wild strain of poliovirus type 1, 2, and 3. After 26 fusions, 55 monoclonal antibodies were obtained with serotype 1 as the immunizing antigen, 180 with serotype 2, and 115 with serotype 3. The neutralizing activity of these monoclonal antibodies was tested first with the two reference strains and then if reactive, against a panel of 10 well-characterized strains of each serotype, 5 vaccinelike (VL) and 5 non vaccinelike (NVL). All monoclonal antibodies were type specific without reactivity with any of the heterologous strains. There was a wide range of reactivity within the strains of each serotype. Several monoclonal antibodies to serotype 1 reacted with all type 1 strains, while several neutralized strongly all VL strains and weakly one or more of the NVL strains. Most of the 180 monoclonal antibodies to serotype 2 neutralized to various degrees all strains of this serotype and about half reacted very strongly with all homologous strains whether VL or NVL. None could differentiate all VL and NVL homologous strains. Of the 115 monoclonal antibodies to serotype 3, several monoclonal antibodies neutralize to various levels all homologous strains and some can differentiate VL and NVL strains.Key words: poliovirus, monoclonal antibody, neutralization, serodifferentiation.
Characterization of partially purified microbodies from hydrocarbon-grown cells of Cladosporium resinae
Authors: Carson David B. , Cooney Joseph J.
Published: November 2009

Cells of the filamentous fungus Cladosporium resinae synthesize many more microbodies when they are grown on an n-alkane than when they are grown on glucose. Cladosporium resinae was grown on n-dodecane and spheroplasts were prepared, disrupted, and fractionated by differential and density gradient centrifugation. A fraction was isolated which was enriched in catalase, a marker enzyme for microbodies. Another fraction was isolated which was enriched in cytochrome c oxidase, a marker for mitochondria. Urate oxidase, a second marker for microbodies, was not detected in cell extracts. The microbody and mitochondrial fractions were relatively free of contamination from the endoplasmic reticulum and cytosol as indicated by the amounts of glucose-6-phosphatase and glucose-6-phosphate dehydrogenase present, respectively. Transmission electron microscopy revealed that the catalase-enriched fraction contained intact microbodies, with mitochondria as a minor contaminant. Catalase was localized in microbodies by staining with 3,3′-diaminobenzidine. Mitochrondria were present in the cytochrome c oxidase enriched fraction and took up the vital stain Janus green B. In similar preparations from cells grown on glucose, catalase was largely nonparticulate. Microbodies were not observed in thin sections prepared from density gradient fractions, but mitochondria were present in a cytochrome c oxidase enriched fraction.Key words: Cladosporium resinae, microbodies, mitochondria, catalase, cytochrome c oxidase.