bluuebunny/crossref_metadata_2025_split huggingface dataset:
Role of Osteopontin in Murine Lyme Arthritis and Host Defense againstBorrelia burgdorferi
Authors: Potter Melissa R. , Rittling Susan R. , Denhardt David T. , Roper Randall J. , Weis John H. , Teuscher Cory , Weis Janis J. 
Published: July 2002

ABSTRACTSeveral genetic loci in the mouse have been identified that regulate the severity of Lyme arthritis. The region of chromosome 5 including the osteopontin (OPN) gene (Opn) has been identified in intercross populations of C3H/HeN × C57BL/6 and C3H/HeJ × BALB/cAnN mice. OPN is of particular interest as it is involved in the maintenance and remodeling of tissue during inflammation, it regulates production of interleukin-10 (IL-10) and IL-12 (cytokines implicated in Lyme arthritis), it is necessary for host control of certain bacterial infections, and mice displaying different severities of Lyme arthritis possess different alleles of the OPN gene. Macrophages and splenocytes from OPN-deficient mice on mixed C57BL/6J-129S or inbred 129S backgrounds were stimulated with the Pam3Cys modified lipoprotein fromBorrelia burgdorferi, OspA. OPN was not required for OspA-induced cytokine production; however, macrophages from 129S-Opn−/−mice displayed a reduced level of IL-10 production. OPN was also not required for resistance to severe arthritis, asB. burgdorferi-infected 129S-Opn−/−mice developed mild arthritis, as did their wild-type littermates. Arthritis was more severe in OPN-deficient mice on the mixed C57BL/6J-129S backgrounds than in inbred mice of either strain. This increase was most likely due to a gene(s) closely linked toOpnon chromosome 5 in conjunction with other randomly assorting genes. Deficiency in OPN did not influence the numbers of spirochetes in tissues fromB. burgdorferi-infected mice, indicating OPN is not part of the host defense to this pathogen. Interestingly, there was no alteration in theB. burgdorferi-specific antibody isotypes in OPN-deficient mice, indicating that its effect on helper T-cell responses is not relevant to the host response toB. burgdorferi.
Identification of Motility and Autoagglutination
Campylobacter jejuni
Mutants by Random Transposon Mutagenesis
Authors: Golden Neal J. , Acheson David W. K. 
Published: July 2002

ABSTRACT

Campylobacter jejuni
has been identified as the leading cause of acute bacterial diarrhea in the United States, yet compared with other enteric pathogens, considerably less is understood concerning the virulence factors of this human pathogen. A random in vivo transposon mutagenesis system was recently developed for the purpose of creating a library of
C. jejuni
transformants. A total of 1,065
C. jejuni
transposon mutants were screened for their ability to swarm on motility agar plates and autoagglutinate in liquid cultures; 28 mutants were subsequently identified. The transposon insertion sites were obtained by using random-primed PCR, and the putative genes responsible for these phenotypes were identified. Of these mutants, all 28 were found to have diminished motility (0 to 86% that of the control). Seventeen motility mutants had insertions in genes with strong homology to functionally known motility and chemotaxis genes; however, 11 insertions were in genes of unknown function. Twenty motility mutants were unable to autoagglutinate, suggesting that the expression of flagella is correlated with autoagglutination (AAG). However, four mutants expressed wild-type levels of surface FlaA, as indicated by Western blot analysis, yet were unable to autoagglutinate (Cj1318, Cj1333, Cj1340c, and Cj1062). These results suggest that FlaA is necessary but not sufficient to mediate the AAG phenotype. Furthermore, two of the four AAG mutants (Cj1333 and Cj1062) were unable to invade INT-407 intestinal epithelial cells, as determined by a gentamicin treatment assay. These data identify novel genes important for motility, chemotaxis, and AAG and demonstrate their potential role in virulence.
EnterohemorrhagicEscherichia coliInfection Induces Interleukin-8 Production via Activation of Mitogen-Activated Protein Kinases and the Transcription Factors NF-κB and AP-1 in T84 Cells
Authors: Dahan Stephanie , Busuttil Valere , Imbert Veronique , Peyron Jean-Francois , Rampal Patrick , Czerucka Dorota 
Published: July 2002

ABSTRACTEnterohemorrhagicEscherichia coli(EHEC) infections are associated with hemorrhagic colitis and the hemolytic-uremic syndrome (HUS). In vivo, elevated plasma levels of the proinflammatory cytokine interleukin-8 (IL-8) in EHEC-infected children are correlated with a high risk of developing HUS. As IL-8 gene transcription is regulated by the transcription factors NF-κB and AP-1, we analyzed the role of these factors in the regulation of IL-8 production after infection of the epithelial intestinal T84 cell line by EHEC. By 6 h of infection, EHEC had induced significant secretion of IL-8 (35.84 ± 6.76 ng/ml versus 0.44 ± 0.04 ng/ml in control cells). EHEC induced AP-1 and NF-κB activation by 3 h of infection. Moreover, the three mitogen-activated protein kinases (MAPK) (ERK1/2, p38, and JNK) were phosphorylated in EHEC-infected T84 cells concomitant with induction of AP-1 DNA binding activity, and IκB-α was phosphorylated and then degraded concomitant with induction of NF-κB DNA binding activity. Pretreatment of cells with the highly specific MEK1/2 inhibitor U0126, the p38 inhibitor SB203580, and/or the proteasome inhibitor ALLN led to inhibition of the IL-8 secretion induced in EHEC-infected T84 cells. These findings demonstrate that (i) EHEC can induce in vitro a potent proinflammatory response by secretion of IL-8 and (ii) the secretion of IL-8 is due to the involvement of MAPK, AP-1, and NF-κB signaling pathways.
Protection of Killer Antiidiotypic Antibodies against Early Invasive Aspergillosis in a Murine Model of Allogeneic T-Cell-Depleted Bone Marrow Transplantation
Authors: Cenci Elio , Mencacci Antonella , Spreca Antonio , Montagnoli Claudia , Bacci Angela , Perruccio Katia , Velardi Andrea , Magliani Walter , Conti Stefania , Polonelli Luciano , Romani Luigina 
Published: July 2002

ABSTRACTAntiidiotypic monoclonal antibodies (MAbs) representing the internal image of a yeast killer toxin (KT) have therapeutic potential against several fungal infections. The efficacy of KT MAbs againstAspergillus fumigatuswas investigated in a mouse model of T-cell-depleted allogeneic bone marrow transplantation (BMT) with invasive pulmonary aspergillosis. Mice were highly susceptible to infection at 3 days post-BMT, when profound neutropenia was observed both in the periphery and in the lungs. Treatment with KT MAbs protected the mice from infection, as judged by the long-term survival and decreased pathology associated with inhibition of fungal growth and hyphal development in the lungs. In vitro, similar to polymorphonuclear neutrophils, KT MAbs significantly inhibited the hyphal development and metabolic activity of germinatedAspergillusconidia. These results indicate that mimicking the action of neutrophils could be a strategy through which KT MAbs exert therapeutic efficacy inA. fumigatusinfections.
Complete Nucleotide Sequence of Tn
10
Authors: Chalmers Ronald , Sewitz Sven , Lipkow Karen , Crellin Paul 
Published: July 2002

ABSTRACT

The complete nucleotide sequence of Tn
10
has been determined. The dinucleotide signature and percent G+C of the sequence had no discontinuities, indicating that Tn
10
constitutes a homogeneous unit. The new sequence contained three new open reading frames corresponding to a glutamate permease, repressors of heavy metal resistance operons, and a hypothetical protein in
Bacillus subtilis
. The glutamate permease was fully functional when expressed, but Tn
10
did not protect
Escherichia coli
from the toxic effects of various metals.
Identification of
Sinorhizobium meliloti
Genes Regulated during Symbiosis
Authors: Cabanes Didier , Boistard Pierre , Batut Jacques 
Published: July 2002

ABSTRACT

RNA fingerprinting by arbitrarily primed PCR was used to isolate
Sinorhizobium meliloti
genes regulated during the symbiotic interaction with alfalfa (
Medicago sativa
). Sixteen partial cDNAs were isolated whose corresponding genes were differentially expressed between symbiotic and free-living conditions. Thirteen sequences corresponded to genes up-regulated during symbiosis, whereas three were instead repressed during establishment of the symbiotic interaction. Seven cDNAs corresponded to known or predicted
nif
and
fix
genes. Four presented high sequence similarity with genes not yet identified in
S. meliloti
, including genes encoding a component of the pyruvate dehydrogenase complex, a cell surface protein component, a copper transporter, and an argininosuccinate lyase. Finally, five cDNAs did not exhibit any similarity with sequences present in databases. A detailed expression analysis of the nine non-
nif-fix
genes provided evidence for an unexpected variety of regulatory patterns, most of which have not been described so far.
Analysis of the Polar Flagellar Gene System of
Vibrio parahaemolyticus
Authors: Kim Yun-Kyeong , McCarter Linda L. 
Published: July 2002

ABSTRACT

Vibrio parahaemolyticus
has dual flagellar systems adapted for locomotion under different circumstances. A single, sheathed polar flagellum propels the swimmer cell in liquid environments. Numerous unsheathed lateral flagella move the swarmer cell over surfaces. The polar flagellum is produced continuously, whereas the synthesis of lateral flagella is induced under conditions that impede the function of the polar flagellum, e.g., in viscous environments or on surfaces. Thus, the organism possesses two large gene networks that orchestrate polar and lateral flagellar gene expression and assembly. In addition, the polar flagellum functions as a mechanosensor controlling lateral gene expression. In order to gain insight into the genetic circuitry controlling motility and surface sensing, we have sought to define the polar flagellar gene system. The hierarchy of regulation appears to be different from the polar system of
Caulobacter crescentus
or the peritrichous system of enteric bacteria but is pertinent to many
Vibrio
and
Pseudomonas
species. The gene identity and organization of 60 potential flagellar and chemotaxis genes are described. Conserved sequences are defined for two classes of polar flagellar promoters. Phenotypic and genotypic analysis of mutant strains with defects in swimming motility coupled with primer extension analysis of flagellar and chemotaxis transcription provides insight into the polar flagellar organelle, its assembly, and regulation of gene expression.
Global Adaptations Resulting from High Population Densities in
Escherichia coli
Cultures
Authors: Liu XueQiao , Ng Christina , Ferenci Thomas 
Published: July 2002

ABSTRACT

The scope of population density effects was investigated in steady-state continuous cultures of
Escherichia coli
in the absence of complications caused by transient environmental conditions and growth rates. Four distinct bacterial properties reflecting major regulatory and physiological circuits were analyzed. The metabolome profile of bacteria growing at high density contained major differences from low-density cultures. The 10-fold-elevated level of trehalose at higher densities pointed to the increased role of the RpoS sigma factor, which controls trehalose synthesis genes as well as the general stress response. There was an eightfold difference in RpoS levels between bacteria grown at 10
8
and at 10
9
cells/ml. In contrast, the cellular content of the DNA binding protein H-NS, controlling many genes in concert with RpoS, was decreased by high density. Since H-NS and RpoS also influence porin gene expression, the influence of population density on the intricate regulation of outer membrane composition was also investigated. High culture densities were found to strongly repress
ompF
porin transcription, with a sharp threshold at a density of 4.4 × 10
8
cells/ml, while increasing the proportion of OmpC in the outer membrane. The density-dependent regulation of
ompF
was maintained in
rpoS
or
hns
mutants and so was independent of these regulators. The consistently dramatic changes indicate that actively growing, high-density cultures are at least as differentiated from low-density cultures as are exponential- from stationary-phase bacteria.
AnkB, a Periplasmic Ankyrin-Like Protein in
Pseudomonas aeruginosa
, Is Required for Optimal Catalase B (KatB) Activity and Resistance to Hydrogen Peroxide
Authors: Howell Michael L. , Alsabbagh Eyad , Ma Ju-Fang , Ochsner Urs A. , Klotz Martin G. , Beveridge Terry J. , Blumenthal Kenneth M. , Niederhoffer Eric C. , Morris Randall E. , Needham David , Dean Gary E. , Wani Maqsood A. , Hassett Daniel J. 
Published: July 2002

ABSTRACT

In this study, we have cloned the
ankB
gene, encoding an ankyrin-like protein in
Pseudomonas aeruginosa
. The
ankB
gene is composed of 549 bp encoding a protein of 183 amino acids that possesses four 33-amino-acid ankyrin repeats that are a hallmark of erythrocyte and brain ankyrins. The location of
ankB
is 57 bp downstream of
katB
, encoding a hydrogen peroxide-inducible catalase, KatB. Monomeric AnkB is a 19.4-kDa protein with a pI of 5.5 that possesses 22 primarily hydrophobic amino acids at residues 3 to 25, predicting an inner-membrane-spanning motif with the N terminus in the cytoplasm and the C terminus in the periplasm. Such an orientation in the cytoplasmic membrane and, ultimately, periplasmic space was confirmed using AnkB-BlaM and AnkB-PhoA protein fusions. Circular dichroism analysis of recombinant AnkB minus its signal peptide revealed a secondary structure that is ∼65% α-helical. RNase protection and KatB- and AnkB-LacZ translational fusion analyses indicated that
katB
and
ankB
are part of a small operon whose transcription is induced dramatically by H
2
O
2
, and controlled by the global transactivator OxyR. Interestingly, unlike the spherical nature of ankyrin-deficient erythrocytes, the cellular morphology of an
ankB
mutant was identical to that of wild-type bacteria, yet the mutant produced more membrane vesicles. The mutant also exhibited a fourfold reduction in KatB activity and increased sensitivity to H
2
O
2
, phenotypes that could be complemented in
trans
by a plasmid constitutively expressing
ankB
. Our results suggest that AnkB may form an antioxidant scaffolding with KatB in the periplasm at the cytoplasmic membrane, thus providing a protective lattice work for optimal H
2
O
2
detoxification.
An A-Factor-Dependent Extracytoplasmic Function Sigma Factor (ς
AdsA
) That Is Essential for Morphological Development in
Streptomyces griseus
Authors: Yamazaki Haruka , Ohnishi Yasuo , Horinouchi Sueharu 
Published: July 2002

ABSTRACT

A-factor (2-isocapryloyl-3
R
-hydroxymethyl-γ-butyrolactone) at an extremely low concentration triggers streptomycin production and aerial mycelium formation in
Streptomyces griseus
. A-factor induces the expression of an A-factor-dependent transcriptional activator, AdpA, essential for both morphological and physiological differentiation by binding to the A-factor receptor protein ArpA, which has bound and repressed the
adpA
promoter, and dissociating it from the promoter. Nine DNA fragments that were specifically recognized and bound by histidine-tagged AdpA were isolated by cycles of a gel mobility shift-PCR method. One of them was located in front of a gene encoding an extracytoplasmic function ς factor belonging to a subgroup of the primary ς
70
family. The cloned gene was named AdpA-dependent sigma factor gene (
adsA
), and the gene product was named ς
AdsA
. Transcription of
adsA
depended on A-factor and AdpA, since
adsA
was transcribed at a very low and constant level in an A-factor-deficient mutant strain or in an
adpA
-disrupted strain. Consistent with this, transcription of
adsA
was greatly enhanced at or near the timing of aerial hyphae formation, as determined by low-resolution S1 nuclease mapping. High-resolution S1 mapping determined the transcriptional start point 82 nucleotides upstream of the translational start codon. DNase I footprinting showed that AdpA bound both strands symmetrically between the transcriptional start point and the translational start codon; AdpA protected the antisense strand from positions +7 to +41 with respect to the transcriptional start point and the sense strand from positions +12 to +46. A weak palindrome was found in the AdpA-binding site. The unusual position bound by AdpA as a transcriptional activator, in relation to the promoter, suggested the presence of a mechanism by which AdpA activates transcription of
adsA
in some unknown way. Disruption of the chromosomal
adsA
gene resulted in loss of aerial hyphae formation but not streptomycin or yellow pigment production, indicating that ς
AdsA
is involved only in morphological development and not in secondary metabolic function. The presence of a single copy in each of the
Streptomyces
species examined by Southern hybridization suggests a common role in morphogenesis in this genus.
Analysis of Genetic Elements ControllingStaphylococcus aureus lrgABExpression: Potential Role of DNA Topology in SarA Regulation
Authors: Fujimoto David F. , Brunskill Eric W. , Bayles Kenneth W. 
Published: July 2002

ABSTRACTPenicillin-induced killing and murein hydrolase activity inStaphylococcus aureusare dependent on a variety of regulatory elements, including the LytSR two-component regulatory system and the virulence factor regulators Agr and Sar. The LytSR effects on these processes can be explained, in part, by the recent finding that a LytSR-regulated operon, designatedlrgAB, affects murein hydrolase activity and penicillin tolerance. To examine the regulation oflrgABexpression in greater detail, we performed Northern blot and promoter fusion analyses. Both methods revealed that Agr and Sar, like LytSR, positively regulatelrgABexpression. A mutation in theagrlocus reducedlrgABexpression approximately sixfold, while thesarmutation reducedlrgABexpression to undetectable levels.cis-acting regulatory elements involved inlrgABexpression were identified by fusing various fragments of thelrgABpromoter region to thexylEreporter gene and integrating these constructs into the chromosome. Catechol 2,3-dioxygenase assays identified DNA sequences, including an inverted repeat and intrinsic bend sites, that contribute to maximallrgABexpression. Confirmation of the importance of the inverted repeat was achieved by demonstrating that multiple copies of the inverted repeat reducedlrgABpromoter activity, presumably by titrating out a positive regulatory factor. The results of this study demonstrate thatlrgABexpression responds to a variety of positive regulatory factors and suggest that specific DNA topology requirements are important for optimal expression.
A Role for the
umuDC
Gene Products of
Escherichia coli
in Increasing Resistance to DNA Damage in Stationary Phase by Inhibiting the Transition to Exponential Growth
Authors: Murli Sumati , Opperman Timothy , Smith Bradley T. , Walker Graham C. 
Published: July 2002

ABSTRACT

The
umuDC
gene products, whose expression is induced by DNA-damaging treatments, have been extensively characterized for their role in SOS mutagenesis. We have recently presented evidence that supports a role for the
umuDC
gene products in the regulation of growth after DNA damage in exponentially growing cells, analogous to a prokaryotic DNA damage checkpoint. Our further characterization of the growth inhibition at 30°C associated with constitutive expression of the
umuDC
gene products from a multicopy plasmid has shown that the
umuDC
gene products specifically inhibit the transition from stationary phase to exponential growth at the restrictive temperature of 30°C and that this is correlated with a rapid inhibition of DNA synthesis. These observations led to the finding that physiologically relevant levels of the
umuDC
gene products, expressed from a single, SOS-regulated chromosomal copy of the operon, modulate the transition to rapid growth in
E. coli
cells that have experienced DNA damage while in stationary phase. This activity of the
umuDC
gene products is correlated with an increase in survival after UV irradiation. In a distinction from SOS mutagenesis, uncleaved UmuD together with UmuC is responsible for this activity. The
umuDC
-dependent increase in resistance in UV-irradiated stationary-phase cells appears to involve, at least in part, counteracting a Fis-dependent activity and thereby regulating the transition to rapid growth in cells that have experienced DNA damage. Thus, the
umuDC
gene products appear to increase DNA damage tolerance at least partially by regulating growth after DNA damage in both exponentially growing and stationary-phase cells.
Succinyl Coenzyme A Synthetase of
Pseudomonas aeruginosa
with a Broad Specificity for Nucleoside Triphosphate (NTP) Synthesis Modulates Specificity for NTP Synthesis by the 12-Kilodalton Form of Nucleoside Diphosphate Kinase
Authors: Kapatral Vinayak , Bina Xiaowen , Chakrabarty A. M. 
Published: July 2002

ABSTRACT

Pseudomonas aeruginosa
secretes copious amounts of an exopolysaccharide called alginate during infection in the lungs of cystic fibrosis patients. A mutation in the
algR2
gene of mucoid
P. aeruginosa
is known to exhibit a nonmucoid (nonalginate-producing) phenotype and showed reduced activities of succinyl-coenzyme A (CoA) synthetase (Scs) and nucleoside diphosphate kinase (Ndk), implying coregulation of Ndk and Scs in alginate synthesis. We have cloned and characterized the
sucCD
operon encoding the α and β subunits of Scs from
P. aeruginosa
and have studied the role of Scs in generating GTP, an important precursor in alginate synthesis. We demonstrate that, in the presence of GDP, Scs synthesizes GTP using ATP as the phosphodonor and, in the presence of ADP, Scs synthesizes ATP using GTP as a phosphodonor. In the presence of inorganic orthophosphate, succinyl-CoA, and an equimolar amount of ADP and GDP, Scs synthesizes essentially an equimolar amount of ATP and GTP. Such a mechanism of GTP synthesis can be an alternate source for the synthesis of alginate as well as for the synthesis of other macromolecules requiring GTP such as RNA and protein. Scs from
P. aeruginosa
is also shown to exhibit a broad NDP kinase activity. In the presence of inorganic orthophosphate (P
i
), succinyl-CoA, and either GDP, ADP, UDP or CDP, it synthesizes GTP, ATP, UTP, or CTP. Scs was previously shown to copurify with Ndk, presumably as a complex. In mucoid cells of
P. aeruginosa
, Ndk is also known to exist in two forms, a 16-kDa cytoplasmic form predominant in the log phase and a 12-kDa membrane-associated form predominant in the stationary phase. We have observed that the 16-kDa Ndk-Scs complex present in nonmucoid cells, synthesizes all three of the nucleoside triphosphates from a mixture of GDP, UDP, and CDP, whereas the 12-kDa Ndk-Scs complex specifically present in mucoid cell predominantly synthesizes GTP and UTP but not CTP. Such regulation may promote GTP synthesis in the stationary phase when the bulk of alginate is synthesized by mucoid
P. aeruginosa
.