bluuebunny/crossref_metadata_2025_split huggingface dataset:
Correlation of surface hydrophilicity and surface static properties in epoxy/glass fibre after plasma treatment
Authors: Lim Kyung‐Bum , Lee Beak‐Su , Kim Jong‐Taek , Lee Duck‐Chool 
Published: November 2002

AbstractIn this study, which was performed to identify a degradation mechanism in macromolecular insulating material, the contact angle, surface potential decay, surface resistance rate and XPS analysis were compared after exposure of fibre‐glass‐reinforced polymer (FRP) laminate to plasma discharge.In the case of the contact angle, the surface of the untreated specimen showed weak hydrophobicity at 73°. However, the contact angle was decreased to 20° in the plasma‐treated specimen. In the case of chemical changes arising from plasma treatment, carboxyl radicals were generated mainly in the plasma‐treated surface, which was rapidly changed to a hydrophilic surface. In the corona potential decay study to determine the electrical changes of the surface, positive charges were decreased rapidly when compared with negative charges, leading to a negative surface for the untreated specimen. However, in the case of the hydrophilic surface, a lot of carboxyl radicals ( COO) acting as positive polarity were generated, resulting in a positive surface. Owing to such a positive surface, the charges of applied negative polarity were decreased rapidly. Copyright © 2002 John Wiley & Sons, Ltd.
Characterization of sequentially grafted polysaccharide coatings using time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) and principal component analysis (PCA)
Authors: McArthur Sally L. , Wagner Matthew S. , Hartley Patrick G. , McLean Keith M. , Griesser Hans J. , Castner David G. 
Published: November 2002

AbstractSequentially grafted polymer layers are playing an increasingly important role in a variety of biomedical applications. Characterization of the chemistry and structure of these coatings has typically followed a layer‐by‐layer approach, ignoring potential interactions between the adjacent layers and the effects that these interactions may have on the resulting physicochemical characteristics of the surface. Using a sequential grafting protocol to couple the polysaccharide carboxymethyldextran (CMD), previous surface force and x‐ray photoelectron spectroscopy studies have suggested that there was some intercalation of the CMD and intermediate poly(ethyleneimine) (PEI) layers. We have utilized the surface and chemical specificity of time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS) to investigate the intercalation of the polymer layers. Owing to the complexity of the data, principal component analysis (PCA) was used to interpret the spectra of the grafted polymer films. The results of the PCA indicated that variations between spectra could be related directly to the carboxyl density (1 : 2 or 1 : 30 carboxyls per glucose unit) of the CMD. Variations between the spectra were shown to be due to the presence of nitrogen‐rich species from the PEI at the outermost surface in the CMD 1 : 30 samples, whereas the CMD 1 : 2 spectra contained oxygen‐rich species related to the presence of the polysaccharide. These results enabled a model to be developed combining the new data with the previous studies to show the carboxyl‐density‐dependent intercalation of the CMD and PEI layers in this polymer graft. The application of ToF‐SIMS and PCA allowed conclusive determination of the surface structure of this complex grafted polymer layer. Copyright © 2002 John Wiley & Sons, Ltd.
Surface core‐level shift and AFM study of the galena (100) surface
Authors: Leiro J. A. , Laajalehto K. , Peltoniemi M. S. , Torhola M. , Szczerbakow A. 
Published: November 2002

AbstractThe core‐level S 2p and Pb 5d spectra of galena (natural PbS) single crystals have been investigated using synchrotron radiation. Comparison between a synthetic PbS and a mineral galena has been made and the former gave broader S 2p lines than the latter. In both samples a strong broadening of the line was observed when the temperature was increased. Also, the surface core‐level shift (SCLS) was slightly smaller for the synthetic sample. No shift was found for the Pb 5d lines. The atomic force microscopy (AFM) study of the mineral (100) surface showed that only one type of atom (most likely sulphur) is visible, in agreement with Heinzelmann et al. (Z. Phys. B 1992; 88:321). Copyright © 2002 John Wiley & Sons, Ltd.
The respiration and hypoxic tolerance of Nucula nitidosa and N. nucleus: factors responsible for determining their distribution?
Authors: Holmes Sebastian P. , Miller Nicola , Weber Anke 
Published: November 2002

Measurement of the respiration of Nucula nitidosa and N. nucleus determined that N. nucleus had a respiration rate approximately a third greater than that of N. nitidosa, 215·28 and 135·64 μl O2 gdfw−1 h−1, respectively. This was calculated to be equivalent to a metabolic rate of 0·648 J individual−1 24 h−1 for N. nitidosa and 1·752 J individual−1 24 h−1 for N. nucleus. Estimation of the production of N. nucleus, from its respiration rate, revealed that for comparable populations, N. nucleus was approximately a third more productive than N. nitidosa, 30 kJ g dry flesh weight (dfw)−1 m−2 y−1 as opposed to 20 kJ gdfw−1 m−2 y−1. Examination of the Kleiber's constant (β) obtained for each species, demonstrated that for N. nitidosa β fell in the range 0·75–1 and that for N. nucleus β fell in the range 1–1·25. This suggests, in combination with other data, that N. nucleus adopts an ‘exploitative’ functional strategy as opposed to N. nitidosa, which can be regarded as adopting a ‘conservationist’ functional strategy.Observations on the hypoxic tolerance of both N. nitidosa and N. nucleus revealed that N. nucleus had a hypoxic tolerance about twice that of N. nucleus. The mean survival time±standard error for N. nitidosa was 3·53±0·18 d in contrast to 7·72±0·21 d for N. nitidosa. The hypoxic tolerance of either species was not related to body size and was independent of any possible effects of starvation. These results are discussed with reference to their potential effects to determine the distribution of N. nitidosa and N. nucleus.
Modeling the Lag Time ofListeria monocytogenesfrom Viable Count Enumeration and Optical Density Data
Authors: Baty F. , Flandrois J. P. , Delignette-Muller M. L. 
Published: November 2002

ABSTRACTThe following two factors significantly influence estimates of the maximum specific growth rate (μmax) and the lag-phase duration (λ): (i) the technique used to monitor bacterial growth and (ii) the model fitted to estimate parameters. In this study, nine strains ofListeria monocytogeneswere monitored simultaneously by optical density (OD) analysis and by viable count enumeration (VCE) analysis. Four usual growth models were fitted to our data, and estimates of growth parameters were compared from one model to another and from one monitoring technique to another. Our results show that growth parameter estimates depended on the model used to fit data, whereas there were no systematic variations in the estimates of μmaxand λ when the estimates were based on OD data instead of VCE data. By studying the evolution of OD and VCE simultaneously, we found that while log OD/VCE remained constant for some of our experiments, a visible linear increase occurred during the lag phase for other experiments. We developed a global model that fits both OD and VCE data. This model enabled us to detect for some of our strains an increase in OD during the lag phase. If not taken into account, this phenomenon may lead to an underestimate of λ.
Genealogy Profiling through Strain Improvement by Using Metabolic Network Analysis: Metabolic Flux Genealogy of Several Generations of Lysine-Producing Corynebacteria
Authors: Wittmann Christoph , Heinzle Elmar 
Published: November 2002

ABSTRACT

A comprehensive approach of metabolite balancing,
13
C tracer studies, gas chromatography-mass spectrometry, matrix-assisted laser desorption ionization-time of flight mass spectrometry, and isotopomer modeling was applied for comparative metabolic network analysis of a genealogy of five successive generations of lysine-producing
Corynebacterium glutamicum
. The five strains examined (
C. glutamicum
ATCC 13032, 13287, 21253, 21526, and 21543) were previously obtained by random mutagenesis and selection. Throughout the genealogy, the lysine yield in batch cultures increased markedly from 1.2 to 24.9% relative to the glucose uptake flux. Strain optimization was accompanied by significant changes in intracellular flux distributions. The relative pentose phosphate pathway (PPP) flux successively increased, clearly corresponding to the product yield. Moreover, the anaplerotic net flux increased almost twofold as a consequence of concerted regulation of C
3
carboxylation and C
4
decarboxylation fluxes to cover the increased demand for lysine formation; thus, the overall increase was a consequence of concerted regulation of C
3
carboxylation and C
4
decarboxylation fluxes. The relative flux through isocitrate dehydrogenase dropped from 82.7% in the wild type to 59.9% in the lysine-producing mutants. In contrast to the NADPH demand, which increased from 109 to 172% due to the increasing lysine yield, the overall NADPH supply remained constant between 185 and 196%, resulting in a decrease in the apparent NADPH excess through strain optimization. Extrapolated to industrial lysine producers, the NADPH supply might become a limiting factor. The relative contributions of PPP and the tricarboxylic acid cycle to NADPH generation changed markedly, indicating that
C. glutamicum
is able to maintain a constant supply of NADPH under completely different flux conditions. Statistical analysis by a Monte Carlo approach revealed high precision for the estimated fluxes, underlining the fact that the observed differences were clearly strain specific.
Macedocin, a Food-Grade Lantibiotic Produced by
Streptococcus macedonicus
ACA-DC 198
Authors: Georgalaki Marina D. , Van den Berghe Erika , Kritikos Dimitrios , Devreese Bart , Van Beeumen Jozef , Kalantzopoulos George , De Vuyst Luc , Tsakalidou Effie 
Published: November 2002

ABSTRACT

Streptococcus macedonicus
ACA-DC 198, a strain isolated from Greek Kasseri cheese, produces a food-grade lantibiotic named macedocin. Macedocin has a molecular mass of 2,794.76 ± 0.42 Da, as determined by electrospray mass spectrometry. Partial N-terminal sequence analysis revealed 22 amino acid residues that correspond with the amino acid sequence of the lantibiotics SA-FF22 and SA-M49, both of which were isolated from the pathogen
Streptococcus pyogenes
. Macedocin inhibits a broad spectrum of lactic acid bacteria, as well as several food spoilage and pathogenic bacteria, including
Clostridium tyrobutyricum
. It displays a bactericidal effect towards the most sensitive indicator strain,
Lactobacillus sakei
subsp.
sakei
LMG 13558
T
, while the producer strain itself displays autoinhibition when it is grown under conditions that do not favor bacteriocin production. Macedocin is active at pHs between 4.0 and 9.0, and it retains activity even after incubation for 20 min at 121°C with 1 atm of overpressure. Inhibition of macedocin by proteolytic enzymes is variable.
Temperature- and Surfactant-Induced Membrane Modifications That Alter
Listeria monocytogenes
Nisin Sensitivity by Different Mechanisms
Authors: Li Jie , Chikindas Michael L. , Ludescher Richard D. , Montville Thomas J. 
Published: November 2002

ABSTRACT

Nisin interacts with target membranes in four sequential steps: binding, insertion, aggregation, and pore formation. Alterations in membrane composition might influence any of these steps. We hypothesized that cold temperatures (10°C) and surfactant (0.1% Tween 20) in the growth medium would influence
Listeria monocytogenes
membrane lipid composition, membrane fluidity, and, as a result, sensitivity to nisin. Compared to the membranes of cells grown at 30°C, those of
L. monocytogenes
grown at 10°C had increased amounts of shorter, branched-chain fatty acids, increased fluidity (as measured by fluorescence anisotropy), and increased nisin sensitivity. When 0.1% Tween 20 was included in the medium and the cells were cultured at 30°C, there were complex changes in lipid composition. They did not influence membrane fluidity but nonetheless increased nisin sensitivity. Further investigation found that these cells had an increased ability to bind radioactively labeled nisin. This suggests that the modification of the surfactant-adapted cell membrane increased nisin sensitivity at the binding step and demonstrates that each of the four steps can contribute to nisin sensitivity.
A Novel High-Cell-Density Protein Expression System Based on
Ralstonia eutropha
Authors: Srinivasan Sriram , Barnard Gavin C. , Gerngross Tillman U. 
Published: November 2002

ABSTRACT

We describe the development of a novel protein expression system based on the industrial fermentation organism
Ralstonia eutropha
(formerly known as
Alcaligenes eutrophus
) NCIMB 40124. This new system overcomes some of the shortcomings of traditional
Escherichia coli
-based protein expression systems, particularly the propensity of such systems to form inclusion bodies during high-level expression. Using a proteomics approach, we identified promoters that can be induced by simple process parameters or medium compositions in high-density cell culture or shake flasks, respectively. By combining newly developed molecular biological tools with a high-cell-density fermentation process, we were able to produce high levels (>1 g/liter) of soluble, active organophosphohydrolase, a model enzyme prone to inclusion body formation in
E. coli
.
Gene Cloning and Characterization of Multiple Alkane Hydroxylase Systems inRhodococcusStrains Q15 and NRRL B-16531
Authors: Whyte L. G. , Smits T. H. M. , Labbé D. , Witholt B. , Greer C. W. , van Beilen J. B. 
Published: November 2002

ABSTRACTThe alkane hydroxylase systems of twoRhodococcusstrains (NRRL B-16531 and Q15, isolated from different geographical locations) were characterized. Both organisms contained at least four alkane monooxygenase gene homologs (alkB1,alkB2,alkB3, andalkB4). In both strains, thealkB1andalkB2homologs were part ofalkgene clusters, each encoding two rubredoxins (rubA1andrubA2;rubA3andrubA4), a putative TetR transcriptional regulatory protein (alkU1;alkU2), and, in thealkB1cluster, a rubredoxin reductase (rubB). ThealkB3andalkB4homologs were found as separate genes which were not part ofalkgene clusters. Functional heterologous expression of some of the rhodococcalalkgenes (alkB2,rubA2, andrubA4[NRRL B-16531];alkB2andrubB[Q15]) was achieved inEscherichia coliandPseudomonasexpression systems.Pseudomonasrecombinants containing rhodococcalalkB2were able to mineralize and grow on C12to C16n-alkanes. All rhodococcal alkane monooxygenases possessed the highly conserved eight-histidine motif, including two apparent alkane monooxygenase signature motifs (LQRH[S/A]DHH and NYXEHYG[L/M]), and the six hydrophobic membrane-spanning regions found in all alkane monooxygenases related to thePseudomonas putidaGPo1 alkane monooxygenase. The presence of multiple alkane hydroxylases in the two rhodococcal strains is reminiscent of other multiple-degradative-enzyme systems reported inRhodococcus.
Arthrobacter aurescens
TC1 Metabolizes Diverse
s
-Triazine Ring Compounds
Authors: Strong Lisa C. , Rosendahl Charlotte , Johnson Gilbert , Sadowsky Michael J. , Wackett Lawrence P. 
Published: November 2002

ABSTRACT

Arthrobacter aurescens
strain TC1 was isolated without enrichment by plating atrazine-contaminated soil directly onto atrazine-clearing plates.
A. aurescens
TC1 grew in liquid medium with atrazine as the sole source of nitrogen, carbon, and energy, consuming up to 3,000 mg of atrazine per liter.
A. aurescens
TC1 is metabolically diverse and grew on a wider range of
s
-triazine compounds than any bacterium previously characterized. The 23
s
-triazine substrates serving as the sole nitrogen source included the herbicides ametryn, atratone, cyanazine, prometryn, and simazine. Moreover, atrazine substrate analogs containing fluorine, mercaptan, and cyano groups in place of the chlorine substituent were also growth substrates. Analogs containing hydrogen, azido, and amino functionalities in place of chlorine were not growth substrates.
A. aurescens
TC1 also metabolized compounds containing chlorine plus
N
-ethyl,
N
-propyl,
N
-butyl,
N
-
s
-butyl,
N
-isobutyl, or
N
-
t
-butyl substituents on the
s
-triazine ring. Atrazine was metabolized to alkylamines and cyanuric acid, the latter accumulating stoichiometrically. Ethylamine and isopropylamine each served as the source of carbon and nitrogen for growth. PCR experiments identified genes with high sequence identity to
atzB
and
atzC
, but not to
atzA
, from
Pseudomonas
sp. strain ADP.
Oligonucleotide Fingerprinting of rRNA Genes for Analysis of Fungal Community Composition
Authors: Valinsky Lea , Della Vedova Gianluca , Jiang Tao , Borneman James 
Published: November 2002

ABSTRACTThorough assessments of fungal diversity are currently hindered by technological limitations. Here we describe a new method for identifying fungi, oligonucleotide fingerprinting of rRNA genes (OFRG). ORFG sorts arrayed rRNA gene (ribosomal DNA [rDNA]) clones into taxonomic clusters through a series of hybridization experiments, each using a single oligonucleotide probe. A simulated annealing algorithm was used to design an OFRG probe set for fungal rDNA. Analysis of 1,536 fungal rDNA clones derived from soil generated 455 clusters. A pairwise sequence analysis showed that clones with average sequence identities of 99.2% were grouped into the same cluster. To examine the accuracy of the taxonomic identities produced by this OFRG experiment, we determined the nucleotide sequences for 117 clones distributed throughout the tree. For all but two of these clones, the taxonomic identities generated by this OFRG experiment were consistent with those generated by a nucleotide sequence analysis. Eighty-eight percent of the clones were affiliated withAscomycota, while 12% belonged toBasidiomycota. A large fraction of the clones were affiliated with the generaFusarium(404 clones) andRaciborskiomyces(176 clones). Smaller assemblages of clones had high sequence identities to theAlternaria,Ascobolus,Chaetomium,Cryptococcus, andRhizoctoniaclades.
Bile Stress Response inListeria monocytogenesLO28: Adaptation, Cross-Protection, and Identification of Genetic Loci Involved in Bile Resistance
Authors: Begley Máire , Gahan Cormac G. M. , Hill Colin 
Published: November 2002

ABSTRACTBile is one of many barriers thatListeria monocytogenesmust overcome in the human gastrointestinal tract in order to infect and cause disease. We demonstrated that stationary-phase cultures ofL. monocytogenesLO28 were able to tolerate concentrations of bovine, porcine, and human bile and bile acids well in excess of those encountered in vivo. Strain LO28 was relatively bile resistant compared with other clinical isolates ofL. monocytogenes, as well as withListeria innocua,Salmonella entericaserovar Typhimurium LT2, andLactobacillus sakei. While exponential-phaseL. monocytogenesLO28 cells were exquisitely sensitive to unconjugated bile acids, prior adaptation to sublethal levels of bile acids or heterologous stresses, such as acid, heat, salt, or sodium dodecyl sulfate (SDS), significantly enhanced bile resistance. This adaptive response was independent of protein synthesis, and in the cases of bile and SDS adaptation, occurred in seconds. In order to identify genetic loci involved in the bile tolerance phenotype ofL. monocytogenesLO28, transposon (Tn917) and plasmid (pORI19) integration banks were screened for bile-sensitive mutants. The disrupted genes included a homologue of thecapAlocus required for capsule formation inBacillus anthracis; a gene encoding the transcriptional regulator ZurR; a homologue of anEscherichia coligene,lytB, involved in isoprenoid biosynthesis; a gene encoding a homologue of theBacillus subtilismembrane protein YxiO; and a gene encoding an amino acid transporter with a putative role in pH homeostasis,gadE. Interestingly, all of the identified loci play putative roles in maintenance of the cell envelope or in stress responses.
Photoreactivation of
Escherichia coli
after Low- or Medium-Pressure UV Disinfection Determined by an Endonuclease Sensitive Site Assay
Authors: Oguma Kumiko , Katayama Hiroyuki , Ohgaki Shinichiro 
Published: November 2002

ABSTRACT

Photoreactivation of
Escherichia coli
after inactivation by a low-pressure (LP) UV lamp (254 nm), by a medium-pressure (MP) UV lamp (220 to 580 nm), or by a filtered medium-pressure (MPF) UV lamp (300 to 580 nm) was investigated. An endonuclease sensitive site (ESS) assay was used to determine the number of UV-induced pyrimidine dimers in the genomic DNA of
E. coli
, while a conventional cultivation assay was used to investigate the colony-forming ability (CFA) of
E. coli.
In photoreactivation experiments, more than 80% of the pyrimidine dimers induced by LP or MPF UV irradiation were repaired, while almost no repair of dimers was observed after MP UV exposure. The CFA ratios of
E. coli
recovered so that they were equivalent to 0.9-, 2.3-, and 1.7-log inactivation after 3-log inactivation by LP, MP, and MPF UV irradiation, respectively. Photorepair treatment of DNA in vitro suggested that among the MP UV emissions, wavelengths of 220 to 300 nm reduced the subsequent photorepair of ESS, possibly by causing a disorder in endogenous photolyase, an enzyme specific for photoreactivation. On the other hand, the MP UV irradiation at wavelengths between 300 and 580 nm was observed to play an important role in reducing the subsequent recovery of CFA by inducing damage other than damage to pyrimidine dimers. Therefore, it was found that inactivating light at a broad range of wavelengths effectively reduced subsequent photoreactivation, which could be an advantage that MP UV irradiation has over conventional LP UV irradiation.
Impact of Integrated Fish Farming on Antimicrobial Resistance in a Pond Environment
Authors: Petersen Andreas , Andersen Jens Strodl , Kaewmak Tawatchai , Somsiri Temdoung , Dalsgaard Anders 
Published: November 2002

ABSTRACT

Integrated fish farming combines livestock production with fish farming. Animal manure is shed directly into a fish pond as fertilizer and supports the growth of photosynthetic organisms. The livestock, mainly chickens and pigs, is often fed feed containing growth promoters. In this study we investigated the impact of integrated fish farming on the levels of antimicrobial-resistant bacteria in a pond environment. One integrated broiler chicken-fish farm was studied for 2 months immediately after the start of a new fish production cycle. A significant increase over time in the resistance to six different antimicrobials was found for the indicator organism
Acinetobacter
spp. isolated from composite water-sediment samples. The initial resistance levels prior to the new production cycle were 1 to 5%. After 2 months the levels of resistance to oxytetracycline and sulfamethoxazole reached 100%, and the levels of resistance to ciprofloxacin were more than 80%. The long-term effects of resistance on integrated farming were studied on seven additional farms. The resistance levels were particularly high among
Enterococcus
spp. and were also high among
Acinetobacter
spp. isolated from water-sediment samples compared to the resistance levels at four control farms. In conclusion, integrated fish farming seems to favor antimicrobial-resistant bacteria in the pond environment. This could be attributed to the selective pressure of antimicrobials in the pond environment and/or to the introduction of antimicrobial-resistant bacteria from animal manure. Potential risks to human health were not addressed in this study and remain to be elucidated.