bluuebunny/crossref_metadata_2025_split huggingface dataset:
Invasive Candidiasis Stimulates Hepatocyte and Monocyte Production of Active Transforming Growth Factor β
Authors: Letterio John J. , Lehrnbecher Thomas , Pollack Greg , Walsh Thomas J. , Chanock Stephen J. 
Published: July 2002

ABSTRACTCandida albicansis an opportunistic fungal pathogen and a major cause of morbidity and mortality in patients with compromised immune function. The cytokine response to tissue invasion byC. albicanscan influence the differentiation and function of lymphocytes and other mononuclear cells that are critical components of the host response. While the production of transforming growth factor β (TGF-β) has been documented in mice infected withC. albicansand is known to suppress phagocyte function, the cellular source and role of this cytokine in the pathogenesis of systemic candidiasis are not well understood. We have investigated the source of production of TGF-β by immunohistochemical studies in tissue samples from patients with an uncommon complication of lymphoreticular malignancy, chronic disseminated candidiasis (CDC), and from a neutropenic-rabbit model of CDC. Liver biopsy specimens from patients with documented CDC demonstrated intense staining for extracellular matrix-associated TGF-β1 within inflammatory granulomas, as well as staining for TGF-β1 and TGF-β3 within adjacent hepatocytes. These results correlate with the immunolocalization of TGF-β observed in livers of infected neutropenic rabbits, using a neutralizing antibody that recognizes the mature TGF-β protein. Human peripheral blood monocytes incubated withC. albicansin vitro release large amounts of biologically active TGF-β1. The data demonstrate that local production of active TGF-βs by hepatocytes and by infected mononuclear cells is a component of the response toC. albicansinfection that most probably contributes to disease progression in the immunocompromised host.
Characterization of the Murine T-Lymphocyte Response toSalmonella entericaSerovar Typhimurium Infection
Authors: Mittrücker Hans-Willi , Köhler Anne , Kaufmann Stefan H. E. 
Published: July 2002

ABSTRACTInfection of mice withSalmonella entericaserotype Typhimurium induces a strong Th1 cell response that is central for the control of infection. We infected mice of a resistant background with a virulent strain ofS. entericaserovar Typhimurium and analyzed the kinetics and magnitude of the T-cell response. After infection, the majority of CD4+and CD8+splenocytes acquired an activated phenotype, as indicated by expression levels of CD44 and CD62L. In addition, after 3 to 4 weeks of infection, more than 20% of the CD4+and more than 30% of the CD8+T cells produced gamma interferon (IFN-γ) in response to short-term polyclonal stimulation. In contrast, we detected only a moderate (two- to threefold) expansion of both T-cell populations, and BrdU incorporation revealed that there was either no or only a limited increase in the in vivo proliferation of CD4+and CD8+T cells, respectively. Our results indicate that although an unexpectedly large population of both CD4+and CD8+T cells is activated and acquires the potential to secrete IFN-γ, this activation is not paralleled by substantial expansion of these T-cell populations.
Leishmania majorPromastigotes Inhibit Dendritic Cell Motility In Vitro
Authors: Jebbari Heather , Stagg Andrew J. , Davidson Robert N. , Knight Stella C. 
Published: July 2002

ABSTRACTUsing an in vitro transwell migration assay, we have demonstrated that products secreted byLeishmania majorpromastigotes inhibit the motility of dendritic cells (DC) by up to 93%. Inhibition was dose dependent and reversible. By inhibiting DC migration in vivo,L. majormay therefore subvert DC from their potentially protective role during leishmaniasis.
Improved Immunogenicity and Efficacy of the Recombinant 19-Kilodalton Merozoite Surface Protein 1 by the Addition of Oligodeoxynucleotide and Aluminum Hydroxide Gel in a Murine Malaria Vaccine Model
Authors: Near Karen A. , Stowers Anthony W. , Jankovic Dragana , Kaslow David C. 
Published: July 2002

ABSTRACTVaccination of mice with yeast-secretedPlasmodium yoelii-derived 19-kilodalton merozoite surface protein 1 (yMSP119) has been shown to afford protection from challenge with a lethal strain ofP. yoelii. Sterile immunity can be achieved when MSP119is emulsified in Freund adjuvant but not when it is adsorbed to aluminum hydroxide gel (alum). Because complete Freund adjuvant is not an acceptable adjuvant for use in humans, alternative adjuvants must be identified for formulating MSP119as a vaccine for use in humans. To determine whether oligodeoxynucleotides with CpG motifs (ODN), reported to be a powerful new class of adjuvants, could enhance the immunogenicity of yMSP119, C57BL/6 mice were vaccinated either with yMSP119formulated with Freund adjuvant, with alum, or with ODN plus alum and challenged intravenously withP. yoelii17XL asexual blood-stage parasites. Adsorption of immunogen and adjuvant to alum was optimized by adjusting buffer (phosphate versus acetate) and pH. We found that the adjuvant combination of ODN plus alum with yMSP119, injected intraperitoneally (i.p.), increased immunoglobulin G (IgG) yMSP119-specific antibody production 12-fold over Freund adjuvant given i.p., 3-fold over Freund adjuvant given subcutaneously (s.c.), 300-fold over alum given i.p., and 48-fold over alum given s.c. The predominant antibody isotype in the group receiving alum-ODN-yMSP119was IgG1. Increased antibody levels correlated to protection from a challenge withP. yoelii17XL. Supernatant cytokine levels of gamma interferon in yMSP119-stimulated splenocytes were dramatically elevated in the alum-ODN-yMSP119group. Interleukin-10 (IL-10) levels were also elevated; however, no IL-5 was detected. The cytokine profile, as well as the predominant IgG1 antibody isotype, suggests the protective immune response was a mixed Th1/Th2 response.
Characterization of the
spv
Locus in
Salmonella enterica
Serovar Arizona
Authors: Libby Stephen J. , Lesnick Marc , Hasegawa Patricia , Kurth Michael , Belcher Christopher , Fierer Joshua , Guiney Donald G. 
Published: July 2002

ABSTRACT

Salmonella enterica
serovar Arizona (
S. enterica
subspecies IIIa) is a common
Salmonella
isolate from reptiles and can cause serious systemic disease in humans. The
spv
virulence locus, found on large plasmids in
Salmonella
subspecies I serovars associated with severe infections, was confirmed to be located on the chromosome of serovar Arizona. Sequence analysis revealed that the serovar Arizona
spv
locus contains homologues of
spvRABC
but lacks the
spvD
gene and contains a frameshift in
spvA
, resulting in a different C terminus. The SpvR protein functions as a transcriptional activator for the
spvA
promoter, and SpvB and SpvC are highly conserved. The analysis supports the proposal that the chromosomal
spv
sequence more closely corresponds to the ancestral locus acquired during evolution of
S. enterica
, with plasmid acquisition of
spv
genes in the subspecies I strains involving addition of
spvD
and polymorphisms in
spvA
.
A Study of the CopF Repressor of Plasmid pAMβ1 by Phage Display
Authors: d'Alençon Emmanuelle , Ehrlich S. Dusko 
Published: July 2002

ABSTRACT
We studied DNA binding of a transcriptional repressor, CopF, displayed on a filamentous phage. Mutagenesis of a putative helix-turn-helix motif of CopF and of certain bases of the operator abolished the protein-DNA interaction, establishing the elements involved in CopF function and showing that phage display can be used to study repressor proteins.
Morphogenesis, Adhesive Properties, and Antifungal Resistance Depend on the Pmt6 Protein Mannosyltransferase in the Fungal Pathogen
Candida albicans
Authors: Timpel Claudia , Zink Sigrid , Strahl-Bolsinger Sabine , Schröppel Klaus , Ernst Joachim 
Published: July 2002

ABSTRACT

Protein mannosyltransferases (Pmt proteins) initiate O glycosylation of secreted proteins in fungi. We have characterized
PMT6
, which encodes the second Pmt protein of the fungal pathogen
Candida albicans
. The residues of Pmt6p are 21 and 42% identical to those of
C. albicans
Pmt1p and
S. cerevisiae
Pmt6p, respectively. Mutants lacking one or two
PMT6
alleles grow normally and contain normal Pmt enzymatic activities in cell extracts but show phenotypes including a partial block of hyphal formation (dimorphism) and a supersensitivity to hygromycin B. The morphogenetic defect can be suppressed by overproduction of known components of signaling pathways, including Cek1p, Cph1p, Tpk2p, and Efg1p, suggesting a specific Pmt6p target protein upstream of these components. Mutants lacking both
PMT1
and
PMT6
are viable and show
pmt1
mutant phenotypes and an additional sensitivity to the iron chelator ethylenediamine-di(
o
-hydroxyphenylacetic acid). The lack of Pmt6p significantly reduces adherence to endothelial cells and overall virulence in a mouse model of systemic infection. The results suggest that Pmt6p regulates a more narrow subclass of proteins in
C. albicans
than Pmt1p, including secreted proteins responsible for morphogenesis and antifungal sensitivities.
Characterization of
devH
, a Gene Encoding a Putative DNA Binding Protein Required for Heterocyst Function in
Anabaena
sp. Strain PCC 7120
Authors: Hebbar Pratibha B. , Curtis Stephanie E. 
Published: July 2002

ABSTRACT

The
devH
gene was identified in a screen for
Anabaena
sp. strain PCC 7120 sequences whose transcripts increase in abundance during a heterocyst development time course. The product of
devH
contains a helix-turn-helix motif similar to the DNA binding domain of members of the cyclic AMP receptor protein family, and the protein is most closely related to the cyanobacterial transcriptional activator NtcA.
devH
transcripts are barely detectable in vegetative cells and are induced approximately fivefold after nitrogen starvation. This induction is absent in the two developmental mutants
hetR
and
ntcA
. The gene is expressed as monocistronic transcripts with multiple 5′ termini, and the ∼500-bp region 5′ to
devH
was shown to have promoter activity in vivo. The
devH
gene was insertionally inactivated by the integration of plasmid sequences within the open reading frame. Nitrogen starvation of the
devH
mutant induces heterocysts of wild-type morphology, but the mutant is inviable in the absence of fixed nitrogen and unable to reduce acetylene aerobically.
Constitutive Expression of a Transcription Termination Factor by a Repressed Prophage: Promoters for Transcribing the Phage HK022
nun
Gene
Authors: King Rodney A. , Madsen Peter L. , Weisberg Robert A. 
Published: July 2002

ABSTRACT

Lysogens of phage HK022 are resistant to infection by phage λ. Lambda resistance is caused by the action of the HK022 Nun protein, which prematurely terminates early λ transcripts. We report here that transcription of the
nun
gene initiates at a constitutive prophage promoter,
P
Nun
, located just upstream of the protein coding sequence. The 5′ end of the transcript was determined by primer extension analysis of RNA isolated from HK022 lysogens or RNA made in vitro by transcribing a template containing the promoter with purified
Escherichia coli
RNA polymerase. Inactivation of
P
Nun
by mutation greatly reduced Nun activity and Nun antigen in an HK022 lysogen. However, a low level of residual activity was detected, suggesting that a secondary promoter also contributes to
nun
expression. We found one possible secondary promoter,
P
Nun
′, just upstream of
P
Nun
. Neither promoter is likely to increase the expression of other phage genes in a lysogen because their transcripts should be terminated downstream of
nun
. We estimate that HK022 lysogens in stationary phase contain several hundred molecules of Nun per cell and that cells in exponential phase probably contain fewer.
Role of the
Escherichia coli
Nucleotide Excision Repair Proteins in DNA Replication
Authors: Moolenaar Geri F. , Moorman Celine , Goosen Nora 
Published: July 2002

ABSTRACT

DNA polymerase I (PolI) functions both in nucleotide excision repair (NER) and in the processing of Okazaki fragments that are generated on the lagging strand during DNA replication.
Escherichia coli
cells completely lacking the PolI enzyme are viable as long as they are grown on minimal medium. Here we show that viability is fully dependent on the presence of functional UvrA, UvrB, and UvrD (helicase II) proteins but does not require UvrC. In contrast, Δ
polA
cells grow even better when the
uvrC
gene has been deleted. Apparently UvrA, UvrB, and UvrD are needed in a replication backup system that replaces the PolI function, and UvrC interferes with this alternative replication pathway. With specific mutants of UvrC we could show that the inhibitory effect of this protein is related to its catalytic activity that on damaged DNA is responsible for the 3′ incision reaction. Specific mutants of UvrA and UvrB were also studied for their capacity to support the PolI-independent replication. Deletion of the UvrC-binding domain of UvrB resulted in a phenotype similar to that caused by deletion of the
uvrC
gene, showing that the inhibitory incision activity of UvrC is mediated via binding to UvrB. A mutation in the N-terminal zinc finger domain of UvrA does not affect NER in vivo or in vitro. The same mutation, however, does give inviability in combination with the Δ
polA
mutation. Apparently the N-terminal zinc-binding domain of UvrA has specifically evolved for a function outside DNA repair. A model for the function of the UvrA, UvrB, and UvrD proteins in the alternative replication pathway is discussed.
Characterization of the
ccpA
Gene of
Enterococcus faecalis
: Identification of Starvation-Inducible Proteins Regulated by CcpA
Authors: Leboeuf Céline , Leblanc Laurence , Auffray Yanick , Hartke Axel 
Published: July 2002

ABSTRACT

Inactivation of
ccpA
in
Enterococcus faecalis
leads to reduction of the growth rate, derepression of the
galKETR
operon in the presence of a mixture of glucose and galactose, and reduction of transcription of
ldh
in the presence of glucose. Moreover, the
E. faecalis ccpA
gene fully complements a
Bacillus subtilis ccpA
mutant, arguing for similar functions of these two homologous proteins. Protein comparison on two-dimensional gels from the wild-type cells and the
ccpA
mutant cells revealed a pleiotropic effect of the mutation on gene expression. The HPr protein of the carbohydrate-phosphotransferase system was identified by microsequencing, and a modification of its phosphorylation state was observed between the wild-type and the mutant strains. Moreover, at least 16 polypeptides are overexpressed in the mutant, and 6 are repressed. Interestingly, 13 of the 16 polypeptides whose synthesis is enhanced in the mutant were also identified as glucose starvation proteins. The N-terminal amino acid sequences of four of them match sequences deduced from genes coding for
l
-serine dehydratase, dihydroxyacetone kinase (two genes), and a protein of unknown function from
Deinococcus radiodurans.
Deletion of the
min
Operon Results in Increased Thermosensitivity of an
ftsZ84
Mutant and Abnormal FtsZ Ring Assembly, Placement, and Disassembly
Authors: Yu Xuan-Chuan , Margolin William 
Published: July 2002

ABSTRACT

To investigate the interaction between FtsZ and the Min system during cell division of
Escherichia coli
, we examined the effects of combining a well-known thermosensitive mutation of
ftsZ
,
ftsZ84
, with Δ
minCDE
, a deletion of the entire
min
locus. Because the Min system is thought to down-regulate Z-ring assembly, the prediction was that removing
minCDE
might at least partially suppress the thermosensitivity of
ftsZ84
, which can form colonies below 42°C but not at or above 42°C. Contrary to expectations, the double mutant was significantly more thermosensitive than the
ftsZ84
single mutant. When shifted to the new lower nonpermissive temperature, the double mutant formed long filaments mostly devoid of Z rings, suggesting a likely cause of the increased thermosensitivity. Interestingly, even at 22°C, many Z rings were missing in the double mutant, and the rings that were present were predominantly at the cell poles. Of these, a large number were present only at one pole. These cells exhibited a higher than expected incidence of polar divisions, with a bias toward the newest pole. Moreover, some cells exhibited dramatically elongated septa that stained for FtsZ, suggesting that the double mutant is defective in Z-ring disassembly, and providing a possible mechanism for the polar bias. Thermoresistant suppressors of the double mutant arose that had modestly increased levels of FtsZ84. These cells also exhibited elongated septa and, in addition, produced a high frequency of branched cells. A thermoresistant suppressor of the
ftsZ84
single mutant also synthesized more FtsZ84 and produced branched cells. The evidence from this study indicates that removing the Min system exposes and exacerbates the inherent defects of the FtsZ84 protein, resulting in clear septation phenotypes even at low growth temperatures. Increasing levels of FtsZ84 can suppress some, but not all, of these phenotypes.
Characterization of Alginate Lyase from
Pseudomonas syringae
pv. syringae
Authors: Preston Lori A. , Wong T. Y. , Bender Carol L. , Schiller Neal L. 
Published: July 2002

ABSTRACT

The gene encoding alginate lyase (
algL
) in
Pseudomonas syringae
pv. syringae was cloned, sequenced, and overexpressed in
Escherichia coli
. Alginate lyase activity was optimal when the pH was 7.0 and when assays were conducted at 42°C in the presence of 0.2 M NaCl. In substrate specificity studies, AlgL from
P. syringae
showed a preference for deacetylated polymannuronic acid. Sequence alignment with other alginate lyases revealed conserved regions within AlgL likely to be important for the structure and/or function of the enzyme. Site-directed mutagenesis of histidine and tryptophan residues at positions 204 and 207, respectively, indicated that these amino acids are critical for lyase activity.
Transcriptional Control of the Hydrogen Cyanide Biosynthetic Genes
hcnABC
by the Anaerobic Regulator ANR and the Quorum-Sensing Regulators LasR and RhlR in
Pseudomonas aeruginosa
Authors: Pessi Gabriella , Haas Dieter 
Published: July 2002

ABSTRACT

Virulence factors of
Pseudomonas aeruginosa
include hydrogen cyanide (HCN). This secondary metabolite is maximally produced at low oxygen tension and high cell densities during the transition from exponential to stationary growth phase. The
hcnABC
genes encoding HCN synthase were identified on a genomic fragment complementing an HCN-deficient mutant of
P. aeruginosa
PAO1. The
hcnA
promoter was found to be controlled by the FNR-like anaerobic regulator ANR and by the quorum-sensing regulators LasR and RhlR. Primer extension analysis revealed two transcription starts, T1 and T2, separated by 29 bp. Their function was confirmed by transcriptional
lacZ
fusions. The promoter sequence displayed an FNR/ANR box at −42.5 bp upstream of T2 and a
lux
box centered around −42.5 bp upstream of T1. Expression of the
hcn
genes was completely abolished when this
lux
box was deleted or inactivated by two point mutations in conserved nucleotides. The
lux
box was recognized by both LasR [activated by
N
-(oxododecanoyl)-homoserine lactone] and RhlR (activated by
N
-butanoyl-homoserine lactone), as shown by expression experiments performed in quorum-sensing-defective
P. aeruginosa
mutants and in the
N
-acyl-homoserine lactone-negative heterologous host
P. fluorescens
CHA0. A second, less conserved
lux
box lying 160 bp upstream of T1 seems to account for enhanced quorum-sensing-dependent expression. Without LasR and RhlR, ANR could not activate the
hcn
promoter. Together, these data indicate that expression of the
hcn
promoter from T1 can occur under quorum-sensing control alone. Enhanced expression from T2 appears to rely on a synergistic action between LasR, RhlR, and ANR.
Evolution of Drug Resistance in Experimental Populations of
Candida albicans
Authors: Cowen Leah E. , Sanglard Dominique , Calabrese David , Sirjusingh Caroline , Anderson James B. , Kohn Linda M. 
Published: July 2002

ABSTRACT

Adaptation to inhibitory concentrations of the antifungal agent fluconazole was monitored in replicated experimental populations founded from a single, drug-sensitive cell of the yeast
Candida albicans
and reared over 330 generations. The concentration of fluconazole was maintained at twice the MIC in six populations; no fluconazole was added to another six populations. All six replicate populations grown with fluconazole adapted to the presence of drug as indicated by an increase in MIC; none of the six populations grown without fluconazole showed any change in MIC. In all populations evolved with drug, increased fluconazole resistance was accompanied by increased resistance to ketoconazole and itraconazole; these populations contained ergosterol in their cell membranes and were amphotericin sensitive. The increase in fluconazole MIC in the six populations evolved with drug followed different trajectories, and these populations achieved different levels of resistance, with distinct overexpression patterns of four genes involved in azole resistance: the ATP-binding cassette transporter genes,
CDR1
and
CDR2
; the gene encoding the target enzyme of the azoles in the ergosterol biosynthetic pathway,
ERG11
; and the major facilitator gene,
MDR1
. Selective sweeps in these populations were accompanied by additional genomic changes with no known relationship to drug resistance: loss of heterozygosity in two of the five marker genes assayed and alterations in DNA fingerprints and electrophoretic karyotypes. These results show that chance, in the form of mutations that confer an adaptive advantage, is a determinant in the evolution of azole drug resistance in experimental populations of
C. albicans.
Intra- and Interspecies Signaling between
Streptococcus salivarius
and
Streptococcus pyogenes
Mediated by SalA and SalA1 Lantibiotic Peptides
Authors: Upton M. , Tagg J. R. , Wescombe P. , Jenkinson H. F. 
Published: July 2002

ABSTRACT

Streptococcus salivarius
20P3 produces a 22-amino-acid residue lantibiotic, designated salivaricin A (SalA), that inhibits the growth of a range of streptococci, including all strains of
Streptococcus pyogenes
. Lantibiotic production is associated with the
sal
genetic locus comprising
salA
, the lantibiotic structural gene;
salBCTX
genes encoding peptide modification and export machinery proteins; and
salYKR
genes encoding a putative immunity protein and two-component sensor-regulator system. Insertional inactivation of
salB
in
S. salivarius
20P3 resulted in abrogation of SalA peptide production, of immunity to SalA, and of
salA
transcription. Addition of exogenous SalA peptide to
salB
mutant cultures induced dose-dependent expression of
salA
mRNA (0.2 kb), demonstrating that SalA production was normally autoregulated. Inactivation of
salR
encoding the response regulator of the SalKR two-component system led to reduced production of, and immunity to, SalA. The
sal
genetic locus was also present in
S. pyogenes
SF370 (M type 1), but because of a deletion across the
salBCT
genes, the corresponding lantibiotic peptide, designated SalA1, was not produced. However, in
S. pyogenes
T11 (M type 4) the
sal
locus gene complement was apparently complete, and active SalA1 peptide was synthesized. Exogenously added SalA1 peptide from
S. pyogenes
T11 induced
salA1
transcription in
S. pyogenes
SF370 and in an isogenic
S. pyogenes
T11
salB
mutant and
salA
transcription in
S. salivarius
20P3
salB
. Thus, SalA and SalA1 are examples of streptococcal lantibiotics whose production is autoregulated. These peptides act as intra- and interspecies signaling molecules, modulating lantibiotic production and possibly influencing streptococcal population ecology in the oral cavity.