bluuebunny/crossref_metadata_2025 huggingface dataset:
Cultural Selection and Genetic Diversity in Matrilineal Whales
Authors: Whitehead Hal
Published: July 2002

Low diversities of mitochondrial DNA (mtDNA) have recently been found in four species of matrilineal whale. No satisfactory explanation for this apparent anomaly has been previously suggested. Culture seems to be an important part of the lives of matrilineal whales. The selection of matrilineally transmitted cultural traits, upon which neutral mtDNA alleles “hitchhike,” has the potential to strongly reduce genetic variation. Thus, in contrast to other nonhuman mammals, culture may be an important evolutionary force for the matrilineal whales.
Diminishing Returns from Mutation Supply Rate in Asexual Populations
Authors: Arjan G. J. , Visser M. de , Zeyl Clifford W. , Gerrish Philip J. , Blanchard Jeffrey L. , Lenski Richard E.
Published: July 2002

Mutator genotypes with increased mutation rates may be especially important in microbial evolution if genetic adaptation is generally limited by the supply of mutations. In experimental populations of the bacterium
Escherichia coli
, the rate of evolutionary adaptation was proportional to the mutation supply rate only in particular circumstances of small or initially well-adapted populations. These experiments also demonstrate a “speed limit” on adaptive evolution in asexual populations, one that is independent of the mutation supply rate.
Estimating the Mass of Asteroid 433 Eros During the NEAR Spacecraft Flyby
Authors: Yeomans D. K. , Antreasian P. G. , Cheng A. , Dunham D. W. , Farquhar R. W. , Gaskell R. W. , Giorgini J. D. , Helfrich C. E. , Konopliv A. S. , McAdams J. V. , Miller J. K. , Owen W. M. , Thomas P. C. , Veverka J. , Williams B. G.
Published: July 2002

The Near Earth Asteroid Rendezvous (NEAR) spacecraft flew within 3830 kilometers of asteroid 433 Eros on 23 December 1998. The gravitational perturbation on NEAR was evident in the spacecraft tracking data. Ground-based Doppler and range tracking of the spacecraft as well as spacecraft images of the asteroid's center of figure and surface features were used to determine the mass and rotation pole of Eros. The mass of Eros is (7.2 ± 1.8) × 10
18
grams and, coupled with a volume estimate provided by the NEAR imaging team, this mass suggests a bulk density of 2.5 ± 0.8 grams per cubic centimeter. The rotation pole position is 15.6 (±3.7) degrees in right ascension and 16.4 (±1.8) degrees in declination, which is consistent with ground-based and NEAR imaging team observations.
Dynamical Role of Predators in Population Cycles of a Forest Insect: An Experimental Test
Authors: Turchin P. , Taylor A. D. , Reeve J. D.
Published: July 2002

Population cycles occur frequently in forest insects. Time-series analysis of fluctuations in one such insect, the southern pine beetle (
Dendroctonus frontalis
), suggests that beetle dynamics are dominated by an ecological process acting in a delayed density-dependent manner. The hypothesis that delayed density dependence in this insect results from its interaction with predators was tested with a long-term predator-exclusion experiment. Predator-imposed mortality was negligible during the increase phase, grew during the year of peak population, and reached a maximum during the period of population decline. The delayed nature of the impact of predation suggests that predation is an important process that contributes significantly to southern pine beetle oscillations.
Reversible Molecular Adsorption Based on Multiple-Point Interaction by Shrinkable Gels
Authors: Oya Taro , Enoki Takashi , Grosberg Alexander Yu. , Masamune Satoru , Sakiyama Takaharu , Takeoka Yukikazu , Tanaka Kazunori , Wang Guoqiang , Yilmaz Yasar , Feld Michael S. , Dasari Ramachandra , Tanaka Toyoichi
Published: July 2002

A general approach is presented for creating polymer gels that can recognize and capture a target molecule by multiple-point interaction and that can reversibly change their affinity to the target by more than one order of magnitude. The polymers consist of majority monomers that make the gel reversibly swell and shrink and minority monomers that constitute multiple-point adsorption centers for the target molecule. Multiple-point interaction is experimentally proven by power laws found between the affinity and the concentration of the adsorbing monomers within the gels.
Phase-Coherent Amplification of Matter Waves
Authors: Kozuma Mikio , Suzuki Yoichi , Torii Yoshio , Sugiura Toshiaki , Kuga Takahiro , Hagley E. W. , Deng L.
Published: July 2002

Phase-coherent matter-wave amplification was demonstrated using Bose- Einstein–condensed rubidium-87 atoms. A small seed matter wave was created with coherent optical Bragg diffraction. Amplification of this seed matter wave was achieved by using the initial condensate as a gain medium through the superradiance effect. The coherence properties of the amplified matter wave, studied with a matter-wave interferometer, were shown to be locked to those of the initial seed wave. The active matter-wave device demonstrated here has great potential in the fields of atom optics, atom lithography, and precision measurements.
Fractional Quantum Hall Effect in Organic Molecular Semiconductors
Authors: Schön J. H. , Kloc Ch. , Batlogg B.
Published: July 2002

High-quality crystals of the organic molecular semiconductors tetracene and pentacene were used to prepare metal-insulator-semiconductor (MIS) structures exhibiting hole and electron mobilities exceeding 10
4
square centimeters per volt per second. The carrier concentration in the channel region of these ambipolar field-effect devices was controlled by the applied gate voltage. Well-defined Shubnikov–de Haas oscillations and quantized Hall plateaus were observed for two-dimensional carrier densities in the range of 10
11
per square centimeter. Fractional quantum Hall states were observed in tetracene crystals at temperatures as high as ∼2 kelvin.
Perception of Brassinosteroids by the Extracellular Domain of the Receptor Kinase BRI1
Authors: He Zuhua , Wang Zhi-Yong , Li Jianming , Zhu Qun , Lamb Chris , Ronald Pamela , Chory Joanne
Published: July 2002

An assay was developed to study plant receptor kinase activation and signaling mechanisms. The extracellular leucine-rich repeat (LRR) and transmembrane domains of the
Arabidopsis
receptor kinase BRI1, which is implicated in brassinosteroid signaling, were fused to the serine/threonine kinase domain of XA21, the rice disease resistance receptor. The chimeric receptor initiates plant defense responses in rice cells upon treatment with brassinosteroids. These results, which indicate that the extracellular domain of BRI1 perceives brassinosteroids, suggest a general signaling mechanism for the LRR receptor kinases of plants. This system should allow the discovery of ligands for the LRR kinases, the largest group of plant receptor kinases.
An Organic Solid State Injection Laser
Authors: Schön J. H. , Kloc Ch. , Dodabalapur A. , Batlogg B.
Published: July 2002

We report on electrically driven amplified spontaneous emission and lasing in tetracene single crystals using field-effect electrodes for efficient electron and hole injection. For laser action, feedback is provided by reflections at the cleaved edges of the crystal resulting in a Fabry-Perot resonator. Increasing the injected current density above a certain threshold value results in the decreasing of the spectral width of the emission from 120 millielectron volts to less than 1 millielectron volt because of gain narrowing and eventually laser action. High electron and hole mobilities as well as balanced charge carrier injection lead to improved exciton generation in these gate-controlled devices. Moreover, the effect of charge-induced absorption is substantially reduced in high-quality single crystals compared with amorphous organic materials.
Recovery and Management Options for Spring/Summer Chinook Salmon in the Columbia River Basin
Authors: Kareiva Peter , Marvier Michelle , McClure Michelle
Published: July 2002

Construction of four dams on the lower Snake River (in northwestern United States) between 1961 and 1975 altered salmon spawning habitat, elevated smolt and adult migration mortality, and contributed to severe declines of Snake River salmon populations. By applying a matrix model to long-term population data, we found that (i) dam passage improvements have dramatically mitigated direct mortality associated with dams; (ii) even if main stem survival were elevated to 100%, Snake River spring/summer chinook salmon (
Oncorhynchus tshawytscha)
would probably continue to decline toward extinction; and (iii) modest reductions in first-year mortality or estuarine mortality would reverse current population declines.
Macroscopic Fibers and Ribbons of Oriented Carbon Nanotubes
Authors: Vigolo Brigitte , Pénicaud Alain , Coulon Claude , Sauder Cédric , Pailler René , Journet Catherine , Bernier Patrick , Poulin Philippe
Published: July 2002

A simple method was used to assemble single-walled carbon nanotubes into indefinitely long ribbons and fibers. The processing consists of dispersing the nanotubes in surfactant solutions, recondensing the nanotubes in the flow of a polymer solution to form a nanotube mesh, and then collating this mesh to a nanotube fiber. Flow-induced alignment may lead to a preferential orientation of the nanotubes in the mesh that has the form of a ribbon. Unlike classical carbon fibers, the nanotube fibers can be strongly bent without breaking. Their obtained elastic modulus is 10 times higher than the modulus of high-quality bucky paper.
The Ecological Risks and Benefits of Genetically Engineered Plants
Authors: Wolfenbarger L. L. , Phifer P. R.
Published: July 2002

Discussions of the environmental risks and benefits of adopting genetically engineered organisms are highly polarized between pro- and anti-biotechnology groups, but the current state of our knowledge is frequently overlooked in this debate. A review of existing scientific literature reveals that key experiments on both the environmental risks and benefits are lacking. The complexity of ecological systems presents considerable challenges for experiments to assess the risks and benefits and inevitable uncertainties of genetically engineered plants. Collectively, existing studies emphasize that these can vary spatially, temporally, and according to the trait and cultivar modified.
Fluconazole plus Cyclosporine: a Fungicidal Combination Effective against Experimental Endocarditis Due to
Candida albicans
Authors: Marchetti O. , Entenza J. M. , Sanglard D. , Bille J. , Glauser M. P. , Moreillon P.
Published: July 2002

Recent observations demonstrated that fluconazole plus cyclosporine (Cy) synergistically killed
Candida albicans
in vitro. This combination was tested in rats with
C. albicans
experimental endocarditis. The MICs of fluconazole and Cy for the test organism were 0.25 and >10 mg/liter, respectively. Rats were treated for 5 days with either Cy, amphotericin B, fluconazole, or fluconazole-Cy. Although used at high doses, the peak concentrations of fluconazole in the serum of rats (up to 4.5 mg/liter) were compatible with high-dose fluconazole therapy in humans. On the other hand, Cy concentrations in serum (up to 4.5 mg/liter) were greater than recommended therapeutic levels. Untreated rats demonstrated massive pseudohyphal growth in both the vegetations and the kidneys. However, only the kidneys displayed concomitant polymorphonuclear infiltration. The therapeutic results reflected this dissociation. In the vegetations, only the fungicidal fluconazole-Cy combination significantly decreased fungal densities compared to all groups, including amphotericin B (
P
< 0.0001). In the kidneys, all regimens except the Cy regimen were effective, but fluconazole-Cy remained superior to amphotericin B and fluconazole alone in sterilizing the organs (
P
 < 0.0001). While the mechanism responsible for the fluconazole-Cy interaction is hypothetical, this observation opens new perspectives for fungicidal combinations between azoles and other drugs.
Delavirdine in Combination with Zidovudine in Treatment of Human Immunodeficiency Virus Type 1-Infected Patients: Evaluation of Efficacy and Emergence of Viral Resistance in a Randomized, Comparative Phase III Trial
Authors: Joly Véronique , Moroni Mauro , Concia Ercole , Lazzarin Adriano , Hirschel Bernard , Jost Josef , Chiodo Francesco , Bentwich Zvi , Love W. Campbell , Hawkins David A. , Wilkins Edmund G. L. , Gatell Aritigas J. , Vetter Norbert , Greenwald Cynthia , Freimuth William W. , de Cian Wanda ,   The M/3331/0013B Study Group
Published: July 2002

We compared the activity of delavirdine (DLV) plus zidovudine (AZT) (
n
= 300) with that of AZT (
n
= 297) against human immunodeficiency virus type 1 in a randomized, double-blind, placebo-controlled trial. DLV exerted a transient antiviral effect, and mutations for resistance to DLV were found in more than 90% of subjects at week 12. The K103N mutation, which confers nonnucleoside reverse transcriptase inhibitor cross-resistance, was found in 85% of the patients.
Antibiotic Resistance Trends in Enteropathogenic Bacteria Isolated in 1985–1987 and 1995–1998 in Barcelona
Authors: Prats Guillermo , Mirelis Beatriz , Llovet Teresa , Muñoz Carmen , Miró Elisenda , Navarro Ferran
Published: July 2002

Trends in resistance to antimicrobial agents used for therapy have been evaluated with 3,797 enteropathogenic bacteria,
Campylobacter
,
Salmonella
,
Shigella
, and
Yersinia
, between 1985–1987 and 1995–1998. The greater increase in the rate of resistance was observed in
Campylobacter jejuni
for quinolones (from 1 to 82%) and tetracycline (from 23 to 72%) and in gastroenteric salmonellae for ampicillin (from 8 to 44%), chloramphenicol (from 1.7 to 26%), and trimethoprim-sulfamethoxazole and nalidixic acid (from less than 0.5 to 11%). Multidrug resistance was detected in several
Salmonella
serotypes. In the 1995–1998 period, 76% of
Shigella
strains were resistant to trimethoprim-sulfamethoxazole, 43% were resistant to ampicillin, and 39% were resistant to chloramphenicol. Seventy-two percent of
Yersinia enterocolitica
O3 strains were resistant to streptomycin, 45% were resistant to sulfonamides, 28% were resistant to trimethoprim-sulfamethoxazole, and 20% were resistant to chloramphenicol.
Activities of BMS 284756 (T-3811) against
Haemophilus influenzae
,
Moraxella catarrhalis
, and
Streptococcus pneumoniae
Isolates from SENTRY Antimicrobial Surveillance Program Medical Centers in Latin America (1999)
Authors:   SENTRY Participants Group (Latin America), Gales Ana , Sader Helio , Jones Ronald N.
Published: July 2002

The antimicrobial activity of BMS 284756, a novel des-F(6)-quinolone, was comparatively evaluated against 257
Streptococcus pneumoniae
, 198
Haemophilus influenzae
, and 88
Moraxella catarrhalis
strains isolated in Latin America between July and September of 1999 as part of the SENTRY Antimicrobial Surveillance Program. Nearly 28.0% of
S. pneumoniae
strains were nonsusceptible to penicillin. The rank order of quinolone potency versus
S. pneumoniae
was BMS 284756 (MIC at which 90% of isolates were inhibited [MIC
90
], 0.12 μg/ml) > trovafloxacin (MIC
90
, 0.25 μg/ml) > gatifloxacin (MIC
90
, 0.5 μg/ml) > levofloxacin and ciprofloxacin (MIC
90
, 1 to 2 μg/ml). All
S. pneumoniae
strains that were not susceptible to other quinolones were inhibited by BMS 284756 at ≤2 μg/ml. The overall prevalence of β-lactamase production was 15.2% in
H. influenzae
and 98.9% in
M. catarrhalis.
BMS 284756 showed excellent potency and spectrum against this group of pathogens, inhibiting all isolates at ≤0.12 μg/ml. BMS 284756 exhibited activity similar to those displayed by the new fluoroquinolones, such as levofloxacin, trovafloxacin, or gatifloxacin, and could be a therapeutic option for empirical treatment of community-acquired respiratory tract infections.
Amprenavir Inhibitory Quotient and Virological Response in Human Immunodeficiency Virus-Infected Patients on an Amprenavir-Containing Salvage Regimen without or with Ritonavir
Authors: Duval Xavier , Lamotte Claire , Race Ester , Descamps Diane , Damond Florence , Clavel François , Leport Catherine , Peytavin Gilles , Vilde Jean-Louis
Published: July 2002

The efficacy of an amprenavir (APV)-containing therapy without (group A) or with (group B) ritonavir was assessed in patients with failure of previous protease inhibitor therapy for human immunodeficiency virus (HIV) infection. The mean minimal plasma APV concentrations in groups A and B were 58 and 1,320 ng/ml, respectively, corresponding to APV inhibitory quotients of 0.2 (range, 0.03 to 0.70) and 7.0 (range, 1.4 to 145), respectively. At week 24, 2 of 8 and 13 of 14 patients in groups A and B, respectively, had <200 HIV RNA copies/ml of plasma, including 4 of 5 patients infected with APV-resistant viruses.
Distribution of Azithromycin in Plasma and Tonsil Tissue after Repeated Oral Administration of 10 or 20 Milligrams per Kilogram in Pediatric Patients
Authors: Blandizzi Corrado , Malizia Tecla , Batoni Giovanna , Ghelardi Emilia , Baschiera Fabio , Bruschini Paolo , Senesi Sonia , Campa Mario , Del Tacca Mario
Published: July 2002

Azithromycin concentrations in the tonsils of 56 pediatric patients, treated with 10 or 20 mg of the drug per kg of body weight for 3 days, were compared. Azithromycin levels in plasma and tonsil samples were determined up to 8.5 days after the last dose. The 20-mg/kg regimen resulted in an improved tonsillar distribution of azithromycin, suggesting the achievement of enhanced therapeutic concentrations at infective sites of the upper respiratory tract.
Bacterial Community Structure Associated with a Dimethylsulfoniopropionate-Producing North Atlantic Algal Bloom
Authors: González José M. , Simó Rafel , Massana Ramon , Covert Joseph S. , Casamayor Emilio O. , Pedrós-Alió Carlos , Moran Mary Ann
Published: July 2002

The bacteria associated with oceanic algal blooms are acknowledged to play important roles in carbon, nitrogen, and sulfur cycling, yet little information is available on their identities or phylogenetic affiliations. Three culture-independent methods were used to characterize bacteria from a dimethylsulfoniopropionate (DMSP)-producing algal bloom in the North Atlantic. Group-specific 16S rRNA-targeted oligonucleotides, 16S ribosomal DNA (rDNA) clone libraries, and terminal restriction fragment length polymorphism analysis all indicated that the marine
Roseobacter
lineage was numerically important in the heterotrophic bacterial community, averaging >20% of the 16S rDNA sampled. Two other groups of heterotrophic bacteria, the SAR86 and SAR11 clades, were also shown by the three 16S rRNA-based methods to be abundant in the bloom community. In surface waters, the
Roseobacter
, SAR86, and SAR11 lineages together accounted for over 50% of the bacterial rDNA and showed little spatial variability in abundance despite variations in the dominant algal species. Depth profiles indicated that
Roseobacter
phylotype abundance decreased with depth and was positively correlated with chlorophyll
a
, DMSP, and total organic sulfur (dimethyl sulfide plus DMSP plus dimethyl sulfoxide) concentrations. Based on these data and previous physiological studies of cultured
Roseobacter
strains, we hypothesize that this lineage plays a role in cycling organic sulfur compounds produced within the bloom. Three other abundant bacterial phylotypes (representing a cyanobacterium and two members of the α
Proteobacteria
) were primarily associated with chlorophyll-rich surface waters of the bloom (0 to 50 m), while two others (representing
Cytophagales
and δ
Proteobacteria
) were primarily found in deeper waters (200 to 500 m).
Bacterial Primary Colonization and Early Succession on Surfaces in Marine Waters as Determined by Amplified rRNA Gene Restriction Analysis and Sequence Analysis of 16S rRNA Genes
Authors: Dang Hongyue , Lovell Charles R.
Published: July 2002

The nearly universal colonization of surfaces in marine waters by bacteria and the formation of biofilms and biofouling communities have important implications for ecological function and industrial processes. However, the dynamics of surface attachment and colonization in situ, particularly during the early stages of biofilm establishment, are not well understood. Experimental surfaces that differed in their degrees of hydrophilicity or hydrophobicity were incubated in a salt marsh estuary tidal creek for 24 or 72 h. The organisms colonizing these surfaces were examined by using a cultivation-independent approach, amplified ribosomal DNA restriction analysis. The goals of this study were to assess the diversity of bacterial colonists involved in early succession on a variety of surfaces and to determine the phylogenetic affiliations of the most common early colonists. Substantial differences in the representation of different cloned ribosomal DNA sequences were found when the 24- and 72-h incubations were compared, indicating that some new organisms were recruited and some other organisms were lost. Phylogenetic analyses of the most common sequences recovered showed that the colonists were related to organisms known to inhabit surfaces or particles in marine systems. A total of 22 of the 26 clones sequenced were affiliated with the
Roseobacter
subgroup of the α subdivision of the division
Proteobacteria
(α-
Proteobacteria
), and most of these clones were recovered at a high frequency from all surfaces after 24 or 72 h of incubation. Two clones were affiliated with the
Alteromonas
group of the γ-
Proteobacteria
and appeared to be involved only in the very early stages of colonization (within the first 24 h). A comparison of the colonization patterns on the test surfaces indicated that the early bacterial community succession rate and/or direction may be influenced by surface physicochemical properties. However, organisms belonging to the
Roseobacter
subgroup are ubiquitous and rapid colonizers of surfaces in coastal environments.
Controlling Instability in
gacS-gacA
Regulatory Genes during Inoculant Production of
Pseudomonas fluorescens
Biocontrol Strains
Authors: Duffy Brion K. , Défago Geneviève
Published: July 2002

Secondary metabolism in fluorescent pseudomonads is globally regulated by
gacS
, which encodes a membrane-bound sensor kinase, and
gacA
, which encodes a transcriptional response regulator. Spontaneous mutation in either gene blocked biosynthesis of the antimicrobial compounds hydrogen cyanide, 2,4-diacetylphloroglucinol, pyoluteorin, and pyrrolnitrin by the model biocontrol strain
Pseudomonas fluorescens
CHA0. Spontaneous mutants also had altered abilities to utilize several carbon sources and to increase medium pH compared with the wild type, suggesting that
gacS
and
gacA
influence primary as well as secondary bacterial metabolism. Inoculant efficacy for biocontrol was significantly reduced by contamination with regulatory mutants which accumulated during inoculum production. Spontaneous mutants accumulated in all 192 separate liquid cultures examined, typically at a frequency of 1% or higher after 12 days. During scale-up in a simulated industrial fermentation process, mutants increased exponentially and accounted for 7, 23, and 61% of the total viable cells after transfer to 20-, 100-, and 500-ml preparations, respectively. GacS
−
and GacA
−
mutants had identical phenotypes and occurred at the same frequency, indicating that the selective pressures for the two mutants were similar. We developed a simple screening method for monitoring inoculant quality based on the distinctive appearance of mutant colonies (i.e., orange color, enlarged diameter, hyperfluorescence). Mutant competitiveness was favored in a nutrient-rich medium with a high electrolyte concentration (nutrient broth containing yeast extract). We were able to control mutant accumulation and to clean up contaminated cultures by using certain mineral amendments (i.e., zinc, copper, cobalt, manganese, and ammonium molybdate) or by diluting media 1/10. Spontaneous mutants and genetic constructs had the same response to culture conditions. Zinc and medium dilution were also effective for improving the genetic stability of other
P. fluorescens
biocontrol strains obtained from Ghana and Italy.
Rapid Characterization of Spores of
Bacillus cereus
Group Bacteria by Matrix-Assisted Laser Desorption-Ionization Time-of-Flight Mass Spectrometry
Authors: Ryzhov Victor , Hathout Yetrib , Fenselau Catherine
Published: July 2002

Matrix-assisted laser desorption-ionization (MALDI) time-of-flight mass spectrometry was used to characterize the spores of 14 microorganisms of the
Bacillus cereus
group. This group includes the four
Bacillus
species
B. anthracis
,
B. cereus
,
B. mycoides
, and
B. thuringiensis
. MALDI mass spectra obtained from whole bacterial spores showed many similarities between the species, except for
B. mycoides
. At the same time, unique mass spectra could be obtained for the different
B. cereus
and
B. thuringiensis
strains, allowing for differentiation at the strain level. To increase the number of detectable biomarkers in the usually peak-poor MALDI spectra of spores, the spores were treated by corona plasma discharge (CPD) or sonicated prior to MALDI analysis. Spectra of sonicated or CPD-treated spores displayed an ensemble of biomarkers common for
B. cereus
group bacteria. Based on the spectra available, these biomarkers differentiate
B. cereus
group spores from those of
Bacillus subtilis
and
Bacillus globigii
. The effect of growth medium on MALDI spectra of spores was also explored.
Distinct Combinations of
Borrelia burgdorferi
Sensu Lato Genospecies Found in Individual Questing Ticks from Europe
Authors: Kurtenbach Klaus , De Michelis Simona , Sewell Henna-Sisko , Etti Susanne , Schäfer Stefanie M. , Hails Rosie , Collares-Pereira Margarida , Santos-Reis Margarida , Haninçová Klára , Labuda Milan , Bormane Antra , Donaghy Michael
Published: July 2002

The genetic diversity of
Borrelia burgdorferi
sensu lato was assessed in individual adult
Ixodes ricinus
ticks from Europe by direct PCR amplification of spirochetal DNA followed by genospecies-specific hybridization. Analysis of mixed infections in the ticks showed that
B
.
garinii
and
B
.
valaisiana
segregate from
B
.
afzelii
. This and previous findings suggest that host complement interacts with spirochetes in the tick, thereby playing an important role in the ecology of Lyme borreliosis.
Rapid Extraction of DNA From
Escherichia coli
and
Cryptosporidium parvum
for Use in PCR
Authors: Higgins James A. , Jenkins Mark C. , Shelton Daniel R. , Fayer Ron , Karns Jeffrey S.
Published: July 2002

The Xtra Amp tube, Isocode paper, Instagene matrix, and PrepMan matrix methods were evaluated for their ability to rapidly extract PCR-quality DNAs from
Escherichia coli
O157:H7 and
Cryptosporidium parvum
. All methods provided satisfactory DNA from
E. coli
, and the Xtra Amp and Instagene reagents provided satisfactory DNA from
C. parvum
.
Shewanella putrefaciens
Adhesion and Biofilm Formation on Food Processing Surfaces
Authors: Bagge Dorthe , Hjelm Mette , Johansen Charlotte , Huber Ingrid , Gram Lone
Published: July 2002

Laboratory model systems were developed for studying
Shewanella putrefaciens
adhesion and biofilm formation under batch and flow conditions.
S. putrefaciens
plays a major role in food spoilage and may cause microbially induced corrosion on steel surfaces.
S. putrefaciens
bacteria suspended in buffer adhered readily to stainless steel surfaces. Maximum numbers of adherent bacteria per square centimeter were reached in 8 h at 25°C and reflected the cell density in suspension. Numbers of adhering bacteria from a suspension containing 10
8
CFU/ml were much lower in a laminar flow system (modified Robbins device) (reaching 10
2
CFU/cm
2
) than in a batch system (reaching 10
7
CFU/cm
2
), and maximum numbers were reached after 24 h. When nutrients were supplied,
S. putrefaciens
grew in biofilms with layers of bacteria. The rate of biofilm formation and the thickness of the film were not dependent on the availability of carbohydrate (lactate or glucose) or on iron starvation. The number of
S. putrefaciens
bacteria on the surface was partly influenced by the presence of other bacteria (
Pseudomonas fluorescens
) which reduced the numbers of
S. putrefaciens
bacteria in the biofilm. Numbers of bacteria on the surface must be quantified to evaluate the influence of environmental factors on adhesion and biofilm formation. We used a combination of fluorescence microscopy (4′,6′-diamidino-2-phenylindole staining and in situ hybridization, for mixed-culture studies), ultrasonic removal of bacteria from surfaces, and indirect conductometry and found this combination sufficient to quantify bacteria on surfaces.
Evidence that Certain Clones of
Campylobacter jejuni
Persist during Successive Broiler Flock Rotations
Authors: Petersen L. , Wedderkopp A.
Published: July 2002

Through the national surveillance program for
Campylobacter
spp., nine broiler chicken farms that were infected with
Campylobacter jejuni
in at least five rotations in 1998 were identified. One additional farm, located at the island of Bornholm where divided slaughter is used extensively, was also selected. Twelve broiler houses located on 10 farms were included in the study. The
C. jejuni
isolates collected from the selected houses during the surveillance were typed using
fla
typing and macrorestriction profiling (MRP), and a subset of the isolates, representing each of the identified clones, was serotyped according to the Penner scheme. Pulsed-field gel electrophoresis typing using
Sma
I and
Kpn
I revealed that the majority of houses (11 of 12) carried identical isolates in two or more broiler flocks. Such persistent clones were found in 63% of all flocks (47 of 75). The majority of persistent clones (7 of 13) had
fla
type 1/1, but MRPs distinguished between isolates from different houses, and
fla
type 1/1 clones belonged to different serotypes. Seven houses carried persistent clones that covered an interval of at least four broiler flock rotations, or at least one half year. The dominant
fla
type (1/1) was represented by 44% of isolates, or by at least one isolate from 31 of 62 broiler flocks. This significantly exceeded the prevalence of
fla
type 1/1
C. jejuni
isolates that we have estimated from other studies and suggests that isolates carrying this
fla
type are overrepresented in flocks with recurrent
Campylobacter
problems. The MRPs of clones belonging to
fla
type 1/1 serotype O:2 isolated from persistently infected flocks shared a high percentage of bands compared to the remaining isolates, indicating that some clones that have the ability to cause persistent infections in broiler farms are highly related to each other.
Salmonella enterica
Serovar Typhimurium DT104 Displays a Rugose Phenotype
Authors: Anriany Yuda A. , Weiner Ronald M. , Johnson Judith A. , De Rezende Christian E. , Joseph Sam W.
Published: July 2002

Rugose phenotypes, such as those observed in
Vibrio cholerae
, have increased resistance to chlorine, oxidative stress, and complement-mediated killing. In this study we identified and defined a rugose phenotype in
Salmonella enterica
serovar Typhimurium DT104 and showed induction only on certain media at 25°C after 3 days of incubation. Incubation at 37°C resulted in the appearance of the smooth phenotype. Observation of the ultrastructure of the rugose form and a stable smooth variant (Stv), which was isolated following a series of passages of the rugose cells, revealed extracellular substances only in cells from the rugose colony. Observation of the extracellular substance by scanning electron microscopy (SEM) was correlated with the appearance of corrugation during development of rugose colony morphology over a 4-day incubation period at 25°C. In addition, the cells also formed a pellicle in liquid broth, which was associated with the appearance of interlacing slime and fibrillar structures, as observed by SEM. The pellicle-forming cells were completely surrounded by capsular material, which bound cationic ferritin, thus indicating the presence of an extracellular anionic component. The rugose cells, in contrast to Stv, showed resistance to low pH and hydrogen peroxide and an ability to form biofilms. Based on these results and analogy to the rugose phenotype in
V. cholerae
, we propose a possible role for the rugose phenotype in the survival of
S. enterica
serovar Typhimurium DT104.
Production of Penicillin by Fungi Growing on Food Products: Identification of a Complete Penicillin Gene Cluster in
Penicillium griseofulvum
and a Truncated Cluster in
Penicillium verrucosum
Authors: Laich Federico , Fierro Francisco , Martín Juan F.
Published: July 2002

Mycobiota growing on food is often beneficial for the ripening and development of the specific flavor characteristics of the product, but it can also be harmful due to the production of undesirable compounds such as mycotoxins or antibiotics. Some of the fungi most frequently isolated from fermented and cured meat products such as
Penicillium chrysogenum
and
Penicillium nalgiovense
are known penicillin producers; the latter has been shown to be able to produce penicillin when growing on the surface of meat products and secrete it to the medium. The presence of penicillin in food must be avoided, since it can lead to allergic reactions and the arising of penicillin resistance in human-pathogenic bacteria. In this article we describe a study of the penicillin production ability among fungi of the genus
Penicillium
that are used as starters for cheese and meat products or that are frequently isolated from food products.
Penicillium griseofulvum
was found to be a new penicillin producer and to have a penicillin gene cluster similar to that of
Penicillium chrysogenum
. No other species among the studied fungi were found to produce penicillin or to possess the penicillin biosynthetic genes, except
P. verrucosum
, which contains the
pcbAB
gene (as shown by hybridization and PCR cloning of fragments of the gene) but lacks
pcbC
and
penDE
. Antibacterial activities due to the production of secondary metabolites other than penicillin were observed in some fungi.
Reduced Oxidative Pentose Phosphate Pathway Flux in Recombinant Xylose-Utilizing
Saccharomyces cerevisiae
Strains Improves the Ethanol Yield from Xylose
Authors: Jeppsson Marie , Johansson Björn , Hahn-Hägerdal Bärbel , Gorwa-Grauslund Marie F.
Published: July 2002

In recombinant, xylose-fermenting
Saccharomyces cerevisiae
, about 30% of the consumed xylose is converted to xylitol. Xylitol production results from a cofactor imbalance, since xylose reductase uses both NADPH and NADH, while xylitol dehydrogenase uses only NAD
+
. In this study we increased the ethanol yield and decreased the xylitol yield by lowering the flux through the NADPH-producing pentose phosphate pathway. The pentose phosphate pathway was blocked either by disruption of the
GND1
gene, one of the isogenes of 6-phosphogluconate dehydrogenase, or by disruption of the
ZWF1
gene, which encodes glucose 6-phosphate dehydrogenase. Decreasing the phosphoglucose isomerase activity by 90% also lowered the pentose phosphate pathway flux. These modifications all resulted in lower xylitol yield and higher ethanol yield than in the control strains. TMB3255, carrying a disruption of
ZWF1,
gave the highest ethanol yield (0.41 g g
−1
) and the lowest xylitol yield (0.05 g g
−1
) reported for a xylose-fermenting recombinant
S. cerevisiae
strain, but also an 84% lower xylose consumption rate. The low xylose fermentation rate is probably due to limited NADPH-mediated xylose reduction. Metabolic flux modeling of TMB3255 confirmed that the NADPH-producing pentose phosphate pathway was blocked and that xylose reduction was mediated only by NADH, leading to a lower rate of xylose consumption. These results indicate that xylitol production is strongly connected to the flux through the oxidative part of the pentose phosphate pathway.
Inducible Gene Expression by Nonculturable Bacteria in Milk after Pasteurization
Authors: Gunasekera Thusitha S. , Sørensen Anders , Attfield Paul V. , Sørensen Søren J. , Veal Duncan A.
Published: July 2002

The viability of bacteria in milk after heat treatments was assessed by using three different viability indicators: (i) CFU on plate count agar, (ii) de novo expression of a
gfp
reporter gene, and (iii) membrane integrity based on propidium iodide exclusion. In commercially available pasteurized milk, direct viable counts, based on dye exclusion, were significantly (
P
< 0.05) higher than viable cell counts determined from CFU, suggesting that a significant subpopulation of cells in pasteurized milk are viable but nonculturable. Heating milk at 63.5°C for 30 min resulted in a >4-log-unit reduction in the number of CFU of
Escherichia coli
and
Pseudomonas putida
that were marked with
lac
-inducible
gfp
. However, the reduction in the number of
gfp
-expressing cells of both organisms under the same conditions was <2.5 log units. These results demonstrate that a substantial portion of cells rendered incapable of forming colonies by heat treatment are metabolically active and are able to transcribe and translate genes de novo.
High-Density Microarray of Small-Subunit Ribosomal DNA Probes
Authors: Wilson Kenneth H. , Wilson Wendy J. , Radosevich Jennifer L. , DeSantis Todd Z. , Viswanathan Vijay S. , Kuczmarski Thomas A. , Andersen Gary L.
Published: July 2002

Ribosomal DNA sequence analysis, originally conceived as a way to provide a universal phylogeny for life forms, has proven useful in many areas of biological research. Some of the most promising applications of this approach are presently limited by the rate at which sequences can be analyzed. As a step toward overcoming this limitation, we have investigated the use of photolithography chip technology to perform sequence analyses on amplified small-subunit rRNA genes. The GeneChip (Affymetrix Corporation) contained 31,179 20-mer oligonucleotides that were complementary to a subalignment of sequences in the Ribosomal Database Project (RDP) (B. L. Maidak et al., Nucleic Acids Res.
29:
173-174, 2001). The chip and standard Affymetrix software were able to correctly match small-subunit ribosomal DNA amplicons with the corresponding sequences in the RDP database for 15 of 17 bacterial species grown in pure culture. When bacteria collected from an air sample were tested, the method compared favorably with cloning and sequencing amplicons in determining the presence of phylogenetic groups. However, the method could not resolve the individual sequences comprising a complex mixed sample. Given these results and the potential for future enhancement of this technology, it may become widely useful.
Controlled Production of Stable Heterologous Proteins in
Lactococcus lactis
Authors: Miyoshi A. , Poquet I. , Azevedo V. , Commissaire J. , Bermudez-Humaran L. , Domakova E. , Le Loir Y. , Oliveira S. C. , Gruss A. , Langella P.
Published: July 2002

The use of
Lactococcus lactis
(the most extensively characterized lactic acid bacterium) as a delivery organism for heterologous proteins is, in some cases, limited by low production levels and poor-quality products due to surface proteolysis. In this study, we combined in one
L. lactis
strain use of the nisin-inducible promoter P

nisA

and inactivation of the extracellular housekeeping protease HtrA. The ability of the mutant strain, designated
htrA
-NZ9000, to produce high levels of stable proteins was confirmed by using the staphylococcal nuclease (Nuc) and the following four heterologous proteins fused or not fused to Nuc that were initially unstable in wild-type
L. lactis
strains: (i)
Staphylococcus hyicus
lipase, (ii) the bovine rotavirus antigen nonstructural protein 4, (iii) human papillomavirus antigen E7, and (iv)
Brucella abortus
antigen L7/L12. In all cases, protein degradation was significantly lower in strain
htrA
-NZ9000, demonstrating the usefulness of this strain for stable heterologous protein production.
Species-Specific Monoclonal Antibodies to
Escherichia coli
-Expressed p36 Cytosolic Protein of
Mycoplasma hyopneumoniae
Authors: Caron J. , Sawyer N. , Moumen B. Ben Abdel , Bouh K. Cheikh Saad , Dea S.
Published: July 2002

The p36 protein of
Mycoplasma hyopneumoniae
is a cytosolic protein carrying species-specific antigenic determinants. Based on the genomic sequence of the reference strain ATCC 25934, primers were designed for PCR amplification of the p36-encoding gene (948 bp). These primers were shown to be specific to
M. hyopneumoniae
since no DNA amplicons could be obtained with other mycoplasma species and pathogenic bacteria that commonly colonize the porcine respiratory tract. The amplified p36 gene was subcloned into the pGEX-4T-1 vector to be expressed in
Escherichia coli
as a fusion protein with glutathione
S
-transferase (GST). The GST-p36 recombinant fusion protein was purified by affinity chromatography and cut by thrombin, and the enriched p36 protein was used to immunize female BALB/c mice for the production of anti-p36 monoclonal antibodies (MAbs). The polypeptide specificity of the nine MAbs obtained was confirmed by Western immunoblotting with cell lysates prepared from the homologous strain. Cross-reactivity studies of the anti-p36 MAbs towards two other
M. hyopneumoniae
reference strains (ATCC 25095 and J strains) and Quebec field strains that had been isolated in culture suggested that these anti-p36 MAbs were directed against a highly conserved epitope, or closely located epitopes, of the p36 protein. No reactivity was demonstrated against other mycoplasma species tested. Clinical signs and lesions suggestive of enzootic pneumonia were reproduced in specific-pathogen-free pigs infected experimentally with a virulent Quebec field strain (IAF-DM9827) of
M. hyopneumoniae
. The bacteria could be recovered from lung homogenates of pigs that were killed after the 3-week observation period by both PCR and cultivation procedures. Furthermore, the anti-p36 MAbs permitted effective detection by indirect immunofluorescence of
M. hyopneumoniae
in frozen lung sections from experimentally infected pigs. However, attempts to use the recombinant p36 protein as an antigen in an indirect enzyme-linked immunosorbent assay for the detection of antibodies in sera from convalescent pigs showed no correlation with clinical and pathological findings.
Gastrointestinal Colonization by
Candida albicans
Mutant Strains in Antibiotic-Treated Mice
Authors: Wiesner Stephen M. , Jechorek Robert P. , Garni Robb M. , Bendel Catherine M. , Wells Carol L.
Published: July 2002

Antibiotic-treated mice orally inoculated with one of three
Candida albicans
strains (including two mutant strains) or indigenous
Candida pelliculosa
showed levels of candidal gastrointestinal colonization that were strain specific. However, regardless of strain, the numbers of viable candida were intermediate to high in the stomach, were consistently lowest in the upper small intestine, and increased progressively down the intestinal tract.
Elastase Deficiency Phenotype ofPseudomonas aeruginosaCanine Otitis Externa Isolates
Authors: Petermann Shana R. , Doetkott Curt , Rust Lynn
Published: July 2002

Pseudomonas aeruginosaveterinary isolates were assayed for elastase and total matrix protease activity. The elastase activity of canine ear isolates was much less than that of strain PAO1 and that of all other veterinary isolates (P< 0.0001). The results indicate that canine ear isolates have a distinct elastase phenotype.
Specific Serum Immunoglobulin G Response to Urease and CagA Antigens of
Helicobacter pylori
in Infected Children and Adults in a Country with High Prevalence of Infection
Authors: Torres Javier , Camorlinga-Ponce Margarita , Perez-Perez Guillermo , Muñoz Leopoldo , Muñoz Onofre
Published: July 2002

Few studies have analyzed the immune response to
Helicobacter pylori
CagA and urease antigens across age groups in the same population. The aim of this study was to analyze the serologic immunoglobulin G (IgG) response to CagA and urease proteins in children and adults with gastrointestinal symptoms and belonging to the same population and similar socioeconomic levels. The serologic response was studied in 352 children and 293 adults with gastrointestinal symptoms. IgG antibodies against CagA and urease were tested by enzyme-linked immunosorbent assay methods using highly purified recombinant antigens.
H. pylori
infection was defined as a positive result in a serologic assay using whole-cell
H. pylori
extracts as the antigen. We found, in
H. pylori
-positive children, a seroprevalence of 46.9% to CagA and 16.2% to urease, whereas in
H. pylori
-positive adults, a seroprevalence of 78.9% to CagA and 59% to urease was found. In children, the magnitude of the response to CagA was significantly higher and the response to urease was significantly lower than those in adults. The kinetics of serologic response to CagA and to urease across age groups was contrastably different. Whereas CagA is a strong immunogen, urease is a poor immunogen during natural infection. These differences in the humoral response may be important for the short-term or long-term outcome of the infection. These results add to our knowledge of the epidemiology of
H. pylori
infection.
Animal Model ofMycoplasma pneumoniaeInfection Using Germfree Mice
Authors: Hayakawa Masayuki , Taguchi Haruhiko , Kamiya Shigeru , Fujioka Yasunori , Watanabe Hidehiro , Kawai Shin , Kobayashi Hiroyuki
Published: July 2002

We have attempted to establish a gnotobiotic mouse model monoassociated withMycoplasma pneumoniaefollowing single or repeated infection to examine the mechanism of pathogenesis followingM. pneumoniaeinfection.M. pneumoniaeinoculated into germfree mice colonized equally well at 105CFU/lung in both single infection and repeated infection. In histopathological observation, repeatedly infected mice showed pneumonia with mild infiltration of mononuclear cells and macrophages. Antibody titers againstM. pneumoniaerose in the repeatedly infected mice but not in the singly infected mice. The percentage of CD4-positive, CD8-positive, and CD25-positive lymphocytes infiltrated in the lung was increased in the repeatedly infected mice. In contrast, the lymphocyte subset in the spleen was not significantly different among mock-, singly, and repeatedly infected mice. In the study of cytokine productivity of spleen cells, production of interleukin (IL)-4 and IL-10 was significantly increased and that of gamma interferon was remarkably increased in the mice following repeated infection. These results indicate that a gnotobiotic mouse model monoassociated withM. pneumoniaewas established and that immune mechanisms might be involved in the pathogenesis in pneumonia followingM. pneumoniaeinfection.
Use of Reverse Transcriptase PCR in Early Diagnosis of Rift Valley Fever
Authors: Sall A. A. , Macondo E. A. , Sène O. K. , Diagne M. , Sylla R. , Mondo M. , Girault L. , Marrama L. , Spiegel A. , Diallo M. , Bouloy M. , Mathiot C.
Published: July 2002

Reverse transcriptase PCR (RT-PCR) for diagnosis of Rift Valley fever (RVF) was evaluated by using 293 human and animal sera sampled during an RVF outbreak in Mauritania in 1998. Results of the RT-PCR diagnostic method were compared with those of virus isolation (VI) and detection of immunoglobulin M (IgM) antibodies. Our results showed that RT-PCR is a specific, sensitive tool for RVF diagnosis in the early phase of the disease and that its results do not differ significantly from those obtained by VI. Moreover, the combined results of RT-PCR and IgM antibody detection were in 100% concordance with the results of VI.