bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Gain-of-Function Mutation in the Transcription Factor Upc2p Causes Upregulation of Ergosterol Biosynthesis Genes and Increased Fluconazole Resistance in a Clinical
Candida albicans
Isolate
Authors: Dunkel Nico , Liu Teresa T. , Barker Katherine S. , Homayouni Ramin , Morschhäuser Joachim , Rogers P. David 
Published: May 2008

ABSTRACT

In the pathogenic yeast
Candida albicans
, the zinc cluster transcription factor Upc2p has been shown to regulate the expression of
ERG11
and other genes involved in ergosterol biosynthesis upon exposure to azole antifungals.
ERG11
encodes lanosterol demethylase, the target enzyme of this antifungal class. Overexpression of
UPC2
reduces azole susceptibility, whereas its disruption results in hypersusceptibility to azoles and reduced accumulation of exogenous sterols. Overexpression of
ERG11
leads to the increased production of lanosterol demethylase, which contributes to azole resistance in clinical isolates of
C. albicans
, but the mechanism for this has yet to be determined. Using genome-wide gene expression profiling, we found
UPC2
and other genes involved in ergosterol biosynthesis to be coordinately upregulated with
ERG11
in a fluconazole-resistant clinical isolate compared with a matched susceptible isolate from the same patient. Sequence analysis of the
UPC2
alleles of these isolates revealed that the resistant isolate contained a single-nucleotide substitution in one
UPC2
allele that resulted in a G648D exchange in the encoded protein. Introduction of the mutated allele into a drug-susceptible strain resulted in constitutive upregulation of
ERG11
and increased resistance to fluconazole. By comparing the gene expression profiles of the fluconazole-resistant isolate and of strains carrying wild-type and mutated
UPC2
alleles, we identified target genes that are controlled by Upc2p. Here we show for the first time that a gain-of-function mutation in
UPC2
leads to the increased expression of
ERG11
and imparts resistance to fluconazole in clinical isolates of
C. albicans
.
Combined Deletion of Four
Francisella novicida
Acid Phosphatases Attenuates Virulence and Macrophage Vacuolar Escape
Authors: Mohapatra Nrusingh P. , Soni Shilpa , Reilly Thomas J. , Liu Jirong , Klose Karl E. , Gunn John S. 
Published: May 2008

ABSTRACT

Francisella tularensis
is a facultative intracellular pathogen and the etiologic agent of tularemia. It is capable of escape from macrophage phagosomes and replicates in the host cell cytosol. Bacterial acid phosphatases are thought to play a major role in the virulence and intracellular survival of a number of intracellular pathogens. The goal of this study was to delete the four primary acid phosphatases (Acps) from
Francisella novicida
and examine the interactions of mutant strains with macrophages, as well as the virulence of these strains in mice. We constructed
F. novicida
mutants with various combinations of
acp
deletions and showed that loss of the four Acps (AcpA, AcpB, AcpC, and histidine acid phosphatase [Hap]) in an
F. novicida
strain (ΔABCH) resulted in a 90% reduction in acid phosphatase activity. The ΔABCH mutant was defective for survival/growth within human and murine macrophage cell lines and was unable to escape from phagosome vacuoles. With accumulation of Acp deletions, a progressive loss of virulence in the mouse model was observed. The ΔABCH strain was dramatically attenuated and was an effective single-dose vaccine against homologous challenge. Furthermore, both
acpA
and
hap
were induced when the bacteria were within host macrophages. Thus, the
Francisella
acid phosphatases cumulatively play an important role in intracellular trafficking and virulence.
Vibrio cholerae
RND Family Efflux Systems Are Required for Antimicrobial Resistance, Optimal Virulence Factor Production, and Colonization of the Infant Mouse Small Intestine
Authors: Bina Xiaowen R. , Provenzano Daniele , Nguyen Nathalie , Bina James E. 
Published: May 2008

ABSTRACT

Vibrio cholerae
is a gram-negative human intestinal pathogen that causes the diarrheal disease cholera. Humans acquire cholera by ingesting
V. cholerae
-contaminated food or water. Upon ingestion,
V. cholerae
encounters several barriers to colonization, including bile acid toxicity and antimicrobial products of the innate immune system. In many gram-negative bacteria, resistance to the antimicrobial effects of these products is mediated by RND (resistance-nodulation-division) family efflux systems. In this study we tested the hypothesis that the
V. cholerae
RND efflux systems are required for antimicrobial resistance and virulence. The six
V. cholerae
genes encoding RND efflux pumps were deleted from the genome of the O1 El Tor strain N16961, resulting in the generation of 14 independent RND deletion mutants, including one RND-null strain. Determination of the antimicrobial susceptibilities of the mutants revealed that the RND efflux systems were responsible for resistance to multiple antimicrobial compounds, including bile acids, antimicrobial peptides, and antibiotics. VexB (VC0164) was found to be the RND efflux pump primarily responsible for the resistance of
V. cholerae
to multiple antimicrobial compounds in vitro. In contrast, VexD (VC1757) and VexK (VC1673) encoded efflux pumps with detergent-specific substrate specificities that were redundant with VexB. A strain lacking VexB, VexD, and VexK was attenuated in the infant mouse model, and its virulence factor production was unaffected. In contrast, a
V. cholerae
RND-null strain produced significantly less cholera toxin and fewer toxin-coregulated pili than the wild type and was unable to colonize the infant mouse. The decreased virulence factor production in the RND-null strain was linked to reduced transcription of
tcpP
and
toxT
. Our findings show that the
V. cholerae
RND efflux systems are required for antimicrobial resistance, optimal virulence factor production, and colonization of the infant mouse.
Characterization of Two β-1,3-Glucosyltransferases fromEscherichia coliSerotypes O56 and O152
Authors: Brockhausen Inka , Hu Bo , Liu Bin , Lau Kenneth , Szarek Walter A. , Wang Lei , Feng Lu 
Published: May 2008

ABSTRACTThe O antigens of outer membrane-bound lipopolysaccharides (LPS) in gram-negative bacteria are oligosaccharides consisting of repeating units with various structures and antigenicities. The O56 and O152 antigens ofEscherichia coliboth contain a Glc-β1-3-GlcNAc linkage within the repeating unit. We have cloned and identified the genes (wfaPin O56 andwfgDin O152) within the two O-antigen gene clusters that encode glucosyltransferases involved in the synthesis of this linkage. A synthetic substrate analog of the natural acceptor substrate undecaprenol-pyrophosphate-lipid [GlcNAc-α-PO3-PO3-(CH2)11-O-phenyl] was used as an acceptor and UDP-Glc as a donor substrate to demonstrate that bothwfgDandwfaPencode glucosyltransferases. Enzyme products from both glucosyltransferases were isolated by high-pressure liquid chromatography and analyzed by nuclear magnetic resonance. The spectra showed the expected Glc-β1-3-GlcNAc linkage in the products, confirming that both WfaP and WfgD are forms of UDP-Glc: GlcNAc-pyrophosphate-lipid β-1,3-glucosyltransferases. Both WfaP and WfgD have a DxD sequence, which is proposed to interact with phosphate groups of the nucleotide donor through the coordination of a metal cation, and a short hydrophobic sequence at the C terminus that may help to associate the enzymes with the inner membrane. We showed that the enzymes have similar properties and substrate recognition. They both require a divalent cation (Mn2+or Mg2+) for activity, are deactivated by detergents, have a broad pH optimum, and require the pyrophosphate-sugar linkage in the acceptor substrate for full activity. Substrates lacking phosphate or pyrophosphate linked to GlcNAc were inactive. The length of the aliphatic chain of acceptor substrates also contributes to the activity.
Transcription of theehxEnterohemolysin Gene Is Positively Regulated by GrlA, a Global Regulator Encoded within the Locus of Enterocyte Effacement in EnterohemorrhagicEscherichia coli
Authors: Saitoh Takehito , Iyoda Sunao , Yamamoto Shouji , Lu Yan , Shimuta Ken , Ohnishi Makoto , Terajima Jun , Watanabe Haruo 
Published: May 2008

ABSTRACTThe pathogenicity island termed locus of enterocyte effacement (LEE) encodes a type 3 protein secretion system, whose function is required for full virulence of enterohemorrhagicEscherichia coli(EHEC). GrlR and GrlA are LEE-encoded negative and positive regulators, respectively, for controlling transcription of thelergene, which encodes a central activator of LEE gene expression. We previously reported that the GrlR-GrlA regulatory system controls not only the LEE genes but also flagellar gene expression in EHEC (S. Iyoda et al., J. Bacteriol.188:5682-5692, 2006). In order to further explore virulence-related genes under the control of the GrlR-GrlA regulatory system, we characterized agrlR-deleted EHEC O157 strain, which was found to have high and low levels of expression of LEE and flagellar genes, respectively. We report here that thegrlRdeletion significantly induced enterohemolysin (Ehx) activity of EHEC O157 on plates containing defibrinated sheep erythrocytes. Ehx levels were not induced in thegrlR grlAdouble mutant strain but increased markedly by overexpression of GrlA even in thelermutant, indicating that GrlA is responsible for this regulation. Ehx of the EHEC O157 Sakai strain is encoded by theehxCABDgenes, which are carried on the large plasmid pO157. The expression ofehxCfused with FLAG tag or a promoterlesslacZgene on pO157 was significantly induced under conditions in which GrlA was overproduced. These results together suggest that GrlA acts as a positive regulator for theehxtranscription in EHEC.
The
Burkholderia mallei
BmaR3-BmaI3 Quorum-Sensing System Produces and Responds to
N
-3-Hydroxy-Octanoyl Homoserine Lactone
Authors: Duerkop Breck A. , Herman Jake P. , Ulrich Ricky L. , Churchill Mair E. A. , Greenberg E. Peter 
Published: May 2008

ABSTRACT

Burkholderia mallei
has two acyl-homoserine lactone (acyl-HSL) signal generator-receptor pairs and two additional signal receptors, all of which contribute to virulence. We show that
B. mallei
produces
N
-3-hydroxy-octanoyl HSL (3OHC
8
-HSL) but a
bmaI3
mutant does not. Recombinant
Escherichia coli
expressing BmaI3 produces hydroxylated acyl-HSLs, with 3OHC
8
-HSL being the most abundant compound. In recombinant
E. coli
, BmaR3 responds to 3OHC
8
-HSL but not to other acyl-HSLs. These data indicate that the signal for BmaR3-BmaI3 quorum sensing is 3OHC
8
-HSL.
Roles of Coenzyme F
420
-Reducing Hydrogenases and Hydrogen- and F
420
-Dependent Methylenetetrahydromethanopterin Dehydrogenases in Reduction of F
420
and Production of Hydrogen during Methanogenesis
Authors: Hendrickson Erik L. , Leigh John A. 
Published: May 2008

ABSTRACT

Reduced coenzyme F
420
(F
420
H
2
) is an essential intermediate in methanogenesis from CO
2
. During methanogenesis from H
2
and CO
2
, F
420
H
2
is provided by the action of F
420
-reducing hydrogenases. However, an alternative pathway has been proposed, where H
2
-dependent methylenetetrahydromethanopterin dehydrogenase (Hmd) and F
420
H
2
-dependent methylenetetrahydromethanopterin dehydrogenase (Mtd) together reduce F
420
with H
2
. Here we report the construction of mutants of
Methanococcus maripaludis
that are defective in each putative pathway. Their analysis demonstrates that either pathway supports growth on H
2
and CO
2
. Furthermore, we show that during growth on formate instead of H
2
, where F
420
H
2
is a direct product of formate oxidation, H
2
production occurs. H
2
presumably arises from the oxidation of F
420
H
2
, and the analysis of the mutants during growth on formate suggests that this too can occur by either pathway. We designate the alternative pathway for the interconversion of H
2
and F
420
H
2
the Hmd-Mtd cycle.
Population Heterogeneity inCorynebacterium glutamicumATCC 13032 Caused by Prophage CGP3
Authors: Frunzke Julia , Bramkamp Marc , Schweitzer Jens-Eric , Bott Michael 
Published: May 2008

ABSTRACTThe genome ofCorynebacterium glutamicumtype strain ATCC 13032 (accession number BX927147) contains three prophages, CGP1, CGP2, and CGP3. We recently observed that many genes within the CGP3 prophage region have increased mRNA levels in adtxRdeletion mutant that lacks the master regulator of iron homeostasis (J. Wennerhold and M. Bott, J. Bacteriol.188:2907-2918, 2006). Here, we provide evidence that this effect is due to the increased induction of the prophage CGP3 in thedtxRmutant, possibly triggered by DNA damage caused by elevated intracellular iron concentrations. Upon induction, the CGP3 prophage region is excised from the genome and forms a circular double-stranded DNA molecule. Using quantitative real-time PCR, an average copy number of about 0.1 per chromosome was determined for circular CGP3 DNA in wild-typeC. glutamicum. This copy number increased about 15-fold in thedtxRmutant. In order to visualize the CGP3 DNA within single cells, a derivative of the wild type was constructed that contained an array oftetoperators integrated within the CGP3 region and a plasmid-encoded YFP-TetR fusion protein. As expected, one to two fluorescent foci that represented the chromosomally integrated CGP3 prophage were detected in the majority of cells. However, in a small fraction (2 to 4%) of the population, 4 to 10 CGP3 DNA molecules could be observed in a single cell. Interestingly, the presence of many CGP3 copies in a cell often was accompanied by an efflux of chromosomal DNA, indicating the lysis of the corresponding cell. However, evidence for the formation of functional infective CGP3 phage particles could not be obtained.
Effects of cycle strategy and fibre composition on muscle glycogen depletion pattern and subsequent running economy
Authors: Suriano R , Edge J , Bishop D 
Published: May 2008

PurposeIn this study, the effects of variable and constant-intensity cycling on muscle glycogen depletion patterns and subsequent running economy was examined. 60 minutes of cycling at a constant power (CON) or variable intensity (VAR) followed by a treadmill run to determine running economy was completed by nine male triathletes (Vo2max = 67.7 (4.9 ml) kg−min−1). During CON, there was greater glycogen depletion in the type I fibres compared with type II (0.08 (0.04) vs 0.02 (0.01) optical density (OD) units; p<0.05), while during VAR, there was greater glycogen depletion in the type II fibres compared with type I (0.06 (0.03) vs 0.03 (0.02) OD; p<0.05). The variation in muscle glycogen depletion patterns was not associated with the detriment in running economy, which was not significantly different between conditions (52.1 vs 52.8 ml kg−1min−1). There was a strong correlation between total muscle glycogen depletion and the change in running Vo2(r = 0.73, p<0.05) when the data from both trials were combined. There was also a negative correlation between type I fibre percentage and glycogen depletion within type II fibres during CON (r = −0.85, p<0.05). The results demonstrate that the decrease in running economy, subsequent to 60 minutes of cycling, is not affected by the cycling strategy employed. While different glycogen depletion patterns in the type I and II fibres were observed between conditions, total glycogen depletion may be more important to subsequent running economy. The percentage of type I fibres was associated with the glycogen depletion pattern during constant load, but not variable-intensity exercise.
Independent and inverse association of healthcare utilisation with physical activity in older adults with multiple chronic conditions
Authors: Liu-Ambrose T Y L , Ashe M C , Marra C ,   the Physical Activity and Chronic Conditions Research Team
Published: May 2008

ObjectiveIn this study, whether physical activity is independently associated with direct healthcare costs in community-dwelling older adults with multiple chronic conditions was examined.DesignCross-sectional analysisSettingResearch laboratoryParticipants299 community-dwelling men and women volunteers aged 65 years and older with chronic conditions.InterventionNone.Main outcome measuresPrimary dependent variable was direct healthcare costs incurred in the previous 3 months. Participants completed the Health Resource Utilisation (HRU) questionnaire. To estimate HRU, direct costs in the previous 3 months were calculated using the three-party payer perspective of the British Columbia Ministry of Health, deemed representative of the Canadian healthcare system costs. For medications, the Retail Pharmacy Dispensed prescription cost tables were used. Primary independent variables were (1) self-report current level of physical activity as assessed by the Physical Activity Scale for Individuals with Physical Disabilities (PASIPD) and (2) general balance and mobility as assessed by the National Institute on Aging Balance Scale.ResultsThe mean number of chronic conditions per participant was six. Current level of physical activity was independently and inversely associated with HRU. Age, sex, number of chronic conditions, global cognitive function, body mass index, and general balance and mobility together accounted for 24.3% of the total variance. Adding the PASIPD score resulted in an R2 change of 3.3% and significantly improved the model. The total variance accounted by the final model was 27.6%.ConclusionsPhysical activity promotion may reduce healthcare costs in older adults with chronic conditions.
Reduced Expression of ATP-Binding Cassette Transporter G1 Increases Cholesterol Accumulation in Macrophages of Patients With Type 2 Diabetes Mellitus
Authors: Mauldin Jeremy P. , Nagelin Melissa H. , Wojcik Allison J. , Srinivasan Suseela , Skaflen Marcus D. , Ayers Carlos R. , McNamara Coleen A. , Hedrick Catherine C. 
Published: May 2008

Background—Patients with type 2 diabetes mellitus are at increased risk for the development of atherosclerosis. A pivotal event in the development of atherosclerosis is macrophage foam cell formation. The ATP-binding cassette (ABC) transporters ABCA1 and ABCG1 regulate macrophage cholesterol efflux and hence play a vital role in macrophage foam cell formation. We have previously found that chronic elevated glucose reduces ABCG1 expression. In the present study, we examined whether patients with type 2 diabetes mellitus had decreased ABCG1 and/or ABCA1, impaired cholesterol efflux, and increased macrophage foam cell formation.Methods and Results—Blood was collected from patients with and without type 2 diabetes mellitus. Peripheral blood monocytes were differentiated into macrophages, and cholesterol efflux assays, immunoblots, histological analysis, and intracellular cholesteryl ester measurements were performed. Macrophages from patients with type 2 diabetes mellitus had a 30% reduction in cholesterol efflux with a corresponding 60% increase in cholesterol accumulation relative to control subjects. ABCG1 was present in macrophages from control subjects but was undetectable in macrophages from patients with type 2 diabetes mellitus. In contrast, ABCA1 expression in macrophages was similar in both control subjects and patients with type 2 diabetes mellitus. Macrophage expression of ABCG1 in both patients and control subjects was induced by treatment with the liver X receptor agonist TO-901317. Upregulation of liver X receptor dramatically reduced foam cell formation in macrophages from patients with type 2 diabetes mellitus.Conclusions—ABCG1 expression and cholesterol efflux are reduced in patients with type 2 diabetes mellitus. This impaired ABCG1-mediated cholesterol efflux significantly correlates with increased intracellular cholesterol accumulation. Strategies to upregulate ABCG1 expression and function in type 2 diabetes mellitus could have therapeutic potential for limiting the accelerated vascular disease observed in patients with type 2 diabetes mellitus.
Modeling Optical Turbulence and Seeing over Mauna Kea*
Authors: Cherubini T. , Businger S. , Lyman R. , Chun M. 
Published: May 2008

Abstract
Atmospheric turbulence is a primary concern for astronomers. Turbulence causes amplitude and phase fluctuations in electromagnetic waves propagating through the atmosphere, constraining the maximum telescope resolution and resulting in telescope image degradation. Astronomical parameters that quantify these effects are generically referred to as seeing. Adaptive optics (AO) is used to reduce image degradation associated with optical turbulence. However, to optimize AO, knowledge of the vertical profile of turbulence and overall (integrated) seeing is needed. In this paper, an optical turbulence algorithm is described that makes use of the information on turbulence kinetic energy provided by a planetary boundary layer scheme available in the fifth-generation Pennsylvania State University–NCAR Mesoscale Model (MM5). Optical turbulence data collected on Mauna Kea during the 2002 site monitoring campaign are used to validate the algorithm, which has been implemented in operational runs of MM5 at the Mauna Kea Weather Center.
An Effective Radius Retrieval for Thick Ice Clouds Using GOES
Authors: Lindsey Daniel T. , Grasso Louie 
Published: May 2008

Abstract
Satellite retrieval of cirrus cloud microphysical properties is an important but difficult problem because of uncertainties in ice-scattering characteristics. Most methods have been developed for instruments aboard polar-orbiting satellites, which have better spatial and spectral resolution than geostationary sensors. The Geostationary Operational Environmental Satellite (GOES) series has the advantage of excellent temporal resolution, so that the evolution of thunderstorm-cloud-top properties can be monitored. In this paper, the authors discuss the development of a simple ice cloud effective radius retrieval for thick ice clouds using three bands from the GOES imager: one each in the visible, shortwave infrared, and window infrared portion of the spectrum. It is shown that this retrieval compares favorably to the MODIS effective radius algorithm. In addition, a comparison of the retrieval for clouds viewed simultaneously from GOES-East and GOES-West reveals that the assumed ice-scattering properties perform very well. The algorithm is then used to produce maps of mean ice cloud effective radius over the continental United States. A real-time version of this retrieval is currently running and may be used to study the evolution of thunderstorm-top ice crystal size in rapidly evolving convection.
The Operational Mesogamma-Scale Analysis and Forecast System of the U.S. Army Test and Evaluation Command. Part I: Overview of the Modeling System, the Forecast Products, and How the Products Are Used
Authors: Liu Yubao , Warner Thomas T. , Bowers James F. , Carson Laurie P. , Chen Fei , Clough Charles A. , Davis Christopher A. , Egeland Craig H. , Halvorson Scott F. , Huck Terrence W. , Lachapelle Leo , Malone Robert E. , Rife Daran L. , Sheu Rong-Shyang , Swerdlin Scott P. , Weingarten Dean S. 
Published: May 2008

Abstract
Given the rapid increase in the use of operational mesoscale models to satisfy different specialized needs, it is important for the community to share ideas and solutions for meeting the many associated challenges that encompass science, technology, education, and training. As a contribution toward this objective, this paper begins a series that reports on the characteristics and performance of an operational mesogamma-scale weather analysis and forecasting system that has been developed for use by the U.S. Army Test and Evaluation Command. During the more than five years that this four-dimensional weather system has been in use at seven U.S. Army test ranges, valuable experience has been gained about the production and effective use of high-resolution model products for satisfying a variety of needs. This paper serves as a foundation for the rest of the papers in the series by describing the operational requirements for the system, the data assimilation and forecasting system characteristics, and the forecaster training that is required for the finescale products to be used effectively.