bluuebunny/crossref_metadata_2025_split huggingface dataset:
Disruption of the Genes for ClpXP Protease inSalmonella entericaSerovar Typhimurium Results in Persistent Infection in Mice, and Development of Persistence Requires Endogenous Gamma Interferon and Tumor Necrosis Factor Alpha
Authors: Yamamoto Tomoko , Sashinami Hiroshi , Takaya Akiko , Tomoyasu Toshifumi , Matsui Hidenori , Kikuchi Yuji , Hanawa Tomoko , Kamiya Shigeru , Nakane Akio 
Published: July 2002

ABSTRACTThe enteric pathogenSalmonella entericaserovar Typhimurium, similar to other facultative intracellular pathogens, has been shown to respond to the hostile conditions inside macrophages of the host organism by producing a set of stress proteins that are also induced by various environmental stresses. The stress-induced ClpXP protease is a member of the ATP-dependent proteases, which are known to be responsible for more than 90% of all proteolysis inEscherichia coli. To investigate the contribution of the ClpXP protease to the virulence of serovar Typhimurium we initially cloned theclpPandclpXoperon from the pathogenic strain serovar Typhimurium χ3306 and then created insertional mutations in theclpPand/orclpXgene. The ΔclpPand ΔclpXmutants were used to inoculate BALB/c mice by either the intraperitoneal or the oral route and found to be limited in their ability to colonize organs of the lymphatic system and to cause systemic disease in the host. A variety of experiments were performed to determine the possible reasons for the loss of virulence. An oxygen-dependent killing assay using hydrogen peroxide and paraquat (a superoxide anion generator) and a serum killing assay using murine serum demonstrated that all of the serovar Typhimurium ΔclpPand ΔclpXmutants were as resistant to these killing mechanisms as the wild-type strain. On the other hand, the macrophage survival assay revealed that all these mutants were more sensitive to the intracellular environment than the wild-type strain and were unable to grow or survive within peritoneal macrophages of BALB/c mice. In addition, it was revealed that the serovar Typhimurium ClpXP-depleted mutant was not completely cleared but found to persist at low levels within spleens and livers of mice. Interferon gamma-deficient mice and tumor necrosis factor alpha-deficient mice failed to survive the attenuated serovar Typhimurium infections, suggesting that both endogenous cytokines are essential for regulation of persistent infection with serovar Typhimurium.
P13, an Integral Membrane Protein ofBorrelia burgdorferi, Is C-Terminally Processed and Contains Surface-Exposed Domains
Authors: Noppa Laila , Östberg Yngve , Lavrinovicha Marija , Bergström Sven 
Published: July 2002

ABSTRACTTo elucidate antigens present on the bacterial surface ofBorrelia burgdorferisensu lato that may be involved in pathogenesis, we characterized a protein, P13, with an apparent molecular mass of 13 kDa. The protein was immunogenic and was expressed in large amounts during in vitro cultivation compared to other known antigens. An immunofluorescence assay, immunoelectron microscopy, and protease sensitivity assays indicated that P13 is surface exposed. The deduced sequence of the P13 peptide revealed a possible signal peptidase type I cleavage site, and computer analysis predicted that P13 is an integral membrane protein with three transmembrane-spanning domains. Mass spectrometry, in vitro translation, and N- and C-terminal amino acid sequencing analyses indicated that P13 was posttranslationally processed at both ends and modified by an unknown mechanism. Furthermore,p13belongs to a gene family with five additional members inB. burgdorferisensu stricto. Thep13gene is located on the linear chromosome of the bacterium, in contrast to five paralogous genes, which are located on extrachromosomal plasmids. The size of thep13transcript was consistent with a monocistronic transcript. This new gene family may be involved in functions that are specific for this spirochete and its pathogenesis.
Preparation, Immunogenicity, and Protective Efficacy, in a Murine Model, of a Conjugate Vaccine Composed of the Polysaccharide Moiety of the Lipopolysaccharide of
Vibrio cholerae
O139 Bound to Tetanus Toxoid
Authors: Boutonnier Alain , Villeneuve Sylvain , Nato Farida , Dassy Bruno , Fournier Jean-Michel 
Published: July 2002

ABSTRACT

The epidemic and pandemic potential of
Vibrio cholerae
O139 is such that a vaccine against this newly emerged serogroup of
V. cholerae
is required. A conjugate made of the polysaccharide moiety (O-specific polysaccharide plus core) of the lipopolysaccharide (LPS) of
V. cholerae
O139 (pmLPS) was prepared by derivatization of the pmLPS with adipic acid dihydrazide and coupling to tetanus toxoid (TT) by carbodiimide-mediated condensation. The immunologic properties of the conjugate were tested using BALB/c mice injected subcutaneously three times at 2 weeks interval and then a fourth time 4 weeks later. Mice were bled 7 days after each injection and then once each month for the following 6 months. LPS and TT antibody levels were determined by enzyme-linked immunosorbent assay using immunoplates coated with either O139 LPS or TT. Both pmLPS and pmLPS-TT conjugate elicited low levels of immunoglobulin M (IgM), peaking 5 weeks after the first immunization. The conjugate elicited high levels of IgG antibodies, peaking 3 months after the first immunization and declining slowly during the following 5 months. TT alone, or as a component of conjugate, induced mostly IgG antibodies. Antibodies elicited by the conjugate recognized both capsular polysaccharide and LPS from
V. cholerae
O139 and were vibriocidal. They were also protective in the neonatal mouse model of cholera infection. The conjugation of the O139 pmLPS, therefore, enhanced its immunogenicity and conferred T-dependent properties to this polysaccharide.
Anaerobic Conditions Induce Expression of Polysaccharide Intercellular Adhesin in
Staphylococcus aureus
and
Staphylococcus epidermidis
Authors: Cramton Sarah E. , Ulrich Martina , Götz Friedrich , Döring Gerd 
Published: July 2002

ABSTRACT

Products of the intercellular adhesion (
ica
) operon in
Staphylococcus aureus
and
Staphylococcus epidermidis
synthesize a linear β-1,6-linked glucosaminylglycan. This extracellular polysaccharide mediates bacterial cell-cell adhesion and is required for biofilm formation, which is thought to increase the virulence of both pathogens in association with prosthetic biomedical implants. The environmental signal(s) that triggers
ica
gene product and polysaccharide expression is unknown. Here we demonstrate that anaerobic in vitro growth conditions lead to increased polysaccharide expression in both
S. aureus
and
S. epidermidis
, although the regulation is less stringent in
S. epidermidis
. Anaerobiosis also dramatically stimulates
ica
-specific mRNA expression in
ica
- and polysaccharide
-
positive strains of both
S. aureus
and
S. epidermidis.
These data suggest a mechanism whereby
ica
gene expression and polysaccharide production may act as a virulence factor in an anaerobic environment in vivo.
Long-Term Pertussis-Specific Immunity after Primary Vaccination with a Combined Diphtheria, Tetanus, Tricomponent Acellular Pertussis, and Hepatitis B Vaccine in Comparison with That after Natural Infection
Authors: Esposito Susanna , Agliardi Tiziano , Giammanco Anna , Faldella Giacomo , Cascio Antonio , Bosis Samantha , Friscia Ornella , Clerici Mario , Principi Nicola 
Published: July 2002

ABSTRACT

The aim of this study was to compare pertussis-specific humoral and cellular immunity in children 5 years after a primary vaccination with a combined diphtheria, tetanus, tricomponent acellular pertussis, and hepatitis B vaccine (DTaP-HBV; InfanrixHepB; SmithKline Beecham) with immunity after natural infection. The subjects were 38 children aged 5 to 6 years who received DTaP-HBV at 3, 5, and 11 months of life and 21 subjects of similar ages and sex who acquired pertussis in the first year of life. Immunoglobulin G (IgG) antibody titers against
Bordetella pertussis
antigens, peripheral blood mononuclear cell-specific proliferation, and the secretion of cytokines were evaluated. After 5 years, only a small proportion of vaccinated and infected children had significant specific concentrations of IgG in serum against all three
B. pertussis
antigens, and T-cell responses persisted in a minority of subjects. A preferential type 1 cytokine response with the secretion of gamma interferon was observed in the pertussis group, whereas a type 2 skewed response was observed in the vaccinated children; however, the quantitative differences in the cytokines produced by DTaP-HBV and natural infection were minimal. In conclusion, our results show that the immune responses induced by primary pertussis vaccination are qualitatively and quantitatively similar to those seen in children who recovered from natural infection and highlight the need for booster immunization with pertussis vaccines in order to maintain adequate levels of a specific immune response to
B. pertussis
.
Tandem Repeat Deletion in the Alpha C Protein of Group B
Streptococcus
Is
recA
Independent
Authors: Puopolo Karen M. , Hollingshead Susan K. , Carey Vincent J. , Madoff Lawrence C. 
Published: July 2002

ABSTRACT

Group B streptococci (GBS) contain a family of protective surface proteins characterized by variable numbers of repeating units within the proteins. The prototype alpha C protein of GBS from the type Ia/C strain A909 contains a series of nine identical 246-bp tandem repeat units. We have previously shown that deletions in the tandem repeat region of the alpha C protein affect both the immunogenicity and protective efficacy of the protein in animal models, and these deletions may serve as a virulence mechanism in GBS. The molecular mechanism of tandem repeat deletion is unknown. To determine whether RecA-mediated homologous recombination is involved in this process, we identified, cloned, and sequenced the
recA
gene homologue from GBS. A strain of GBS with
recA
deleted, A909Δ
recA
, was constructed by insertional inactivation in the
recA
locus. A909Δ
recA
demonstrated significant sensitivity to UV light, and the 50% lethal dose of the mutant strain in a mouse intraperitoneal model of sepsis was 20-fold higher than that of the parent strain. The spontaneous rate of tandem repeat deletion in the alpha C protein in vitro, as well as in our mouse model of immune infection, was studied using A909Δ
recA
. We report that tandem repeat deletion in the alpha C protein does occur in the absence of a functional
recA
gene both in vitro and in vivo, indicating that tandem repeat deletion in GBS occurs by a
recA
-independent recombinatorial pathway.
Intimin-Specific Immune Responses Prevent Bacterial Colonization by the Attaching-Effacing PathogenCitrobacter rodentium
Authors: Ghaem-Maghami Marjan , Simmons Cameron P. , Daniell Sarah , Pizza Mariagrazia , Lewis David , Frankel Gad , Dougan Gordon 
Published: July 2002

ABSTRACTThe formation of attaching and effacing (A/E) lesions on gut enterocytes is central to the pathogenesis of enterohemorrhagic (EHEC)Escherichia coli,enteropathogenicE. coli(EPEC), and the rodent pathogenCitrobacter rodentium.Genes encoding A/E lesion formation map to a chromosomal pathogenicity island termed the locus of enterocyte effacement (LEE). Here we show that the LEE-encoded proteins EspA, EspB, Tir, and intimin are the targets of long-lived humoral immune responses inC. rodentium-infected mice. Mice infected withC. rodentiumdeveloped robust acquired immunity and were resistant to reinfection with wild-typeC. rodentiumor aC. rodentiumderivative, DBS255(pCVD438), which expressed intimin derived from EPEC strain E2348/69. The receptor-binding domain of intimin polypeptides is located within the carboxy-terminal 280 amino acids (Int280). Mucosal and systemic vaccination regimens using enterotoxin-based adjuvants were employed to elicit immune responses to recombinant Int280α from EPEC strain E2348/69. Mice vaccinated subcutaneously with Int280α, in the absence of adjuvant, were significantly more resistant to oral challenge with DBS255(pCVD438) but not with wild-typeC. rodentium. This type-specific immunity could not be overcome by employing an exposed, highly conserved domain of intimin (Int388–667) as a vaccine. These results show that anti-intimin immune responses can modulate the outcome of aC. rodentiuminfection and support the use of intimin as a component of a type-specific EPEC or EHEC vaccine.
Cryptosporidium parvum
Infection Requires Host Cell Actin Polymerization
Authors: Elliott David A. , Coleman Daniel J. , Lane Michael A. , May Robin C. , Machesky Laura M. , Clark Douglas P. 
Published: July 2002

ABSTRACT

The intracellular protozoan parasite
Cryptosporidium parvum
accumulates host cell actin at the interface between the parasite and the host cell cytoplasm. Here we show that the actin polymerizing proteins Arp2/3, vasodilator-stimulated phosphoprotein (VASP), and neural Wiskott Aldrich syndrome protein (N-WASP) are present at this interface and that host cell actin polymerization is necessary for parasite infection.
Induction of an AIDS Virus-Related Tuberculosis-Like Disease in Macaques: a Model of Simian Immunodeficiency Virus- Mycobacterium Coinfection
Authors: Shen Yun , Zhou Dejiang , Chalifoux Laura , Shen Ling , Simon Meredith , Zeng Xuejun , Lai Xioamin , Li Yunyuan , Sehgal Prabhat , Letvin Norman L. , Chen Zheng W. 
Published: July 2002

ABSTRACTThe mechanism by which human immunodeficiency virus (HIV)-Mycobacterium tuberculosiscoinfection facilitates development of HIV-related tuberculosis is poorly characterized. Macaque models of simian immunodeficiency virus (SIVmac)-Mycobacterium bovisBCG coinfection were employed to explore the pathogenesis of AIDS virus-related tuberculosis. Following BCG coinfection, SIV (SIV)-infected macaques with high viral loads developed an SIV-related tuberculosis-like disease. This disease was characterized clinically by a syndrome of diarrhea, anorexia, weight loss, and altered levels of consciousness and pathologically by the presence of disseminated granulomas. In contrast, SIVmac-infected macaques with low viral loads either showed no evidence of BCG-induced disease or developed focal granulomatous lesions. Pathogenic SIV-BCG interactions appeared to play a critical role in triggering the development of this SIV-related tuberculosis-like disease. BCG coinfection enhanced the destruction of CD4+T cells in SIVmac-infected macaques whose viral loads were high. Reciprocally, exacerbations of SIV disease led to marked suppression of BCG-specific T-cell responses, persistence of the BCG infection, and development of an SIV-related tuberculosis-like disease. Furthermore, development of this SIV-related tuberculosis-like disease was also seen in naïve macaques simultaneously inoculated with SIVmacand BCG. These results provide in vivo evidence that coinfection of AIDS virus-infected individuals with an avirulent mycobacterium can lead to development of a tuberculosis-like disease.
Naturally Attenuated, Orally Administered
Mycobacterium microti
as a Tuberculosis Vaccine Is Better than Subcutaneous
Mycobacterium bovis
BCG
Authors: Manabe Yukari C. , Scott Cherise P. , Bishai William R. 
Published: July 2002

ABSTRACT

Mycobacterium microti
is phylogenetically closely related to
Mycobacterium tuberculosis
and is a member of that complex of organisms. It is a curved, acid-fast bacillus that is naturally attenuated with a narrow host range for
Microtus
species only. In this study, we confirm the unique susceptibility of voles to infection with
M. microti
and the relative resistance of mice with a significantly lower organism burden after 8 weeks of infection. In addition, histopathologic examination of lungs reveals a lack of cellular, granulomatous aggregates characteristically seen in murine
M. tuberculosis
infection. In the past,
M. microti
has been used successfully in humans as a vaccine against tuberculosis but was associated with cutaneous reactions. In an attempt to circumvent this adverse effect, we report the efficacy of aerosol and oral vaccination with
M. microti.
High-dose orogastric vaccination with
M. microti
resulted in a statistically significant improvement in protection against aerosol challenge with virulent
M. tuberculosis
in the murine model compared with subcutaneous
M. bovis
BCG Pasteur vaccination.
Identification of
Escherichia coli
Genes That Are Specifically Expressed in a Murine Model of Septicemic Infection
Authors: Khan Muhammad A. , Isaacson Richard E. 
Published: July 2002

ABSTRACT

Identification and characterization of bacterial genes that are induced during the disease process are important in understanding the molecular mechanism of disease and can be useful in designing antimicrobial drugs to control the disease. The identification of in vivo induced (
ivi
) genes of an
Escherichia coli
septicemia strain by using antibiotic-based in vivo expression technology is described. Bacterial clones resistant to chloramphenicol in vivo were recovered from the livers of infected mice. Most of the
ivi
clones were sensitive to chloramphenicol when grown in vitro. Using reverse transcription-PCR, it was demonstrated that selected
ivi
clones expressed
cat
in the livers of infected mice but not during in vitro growth. A total of 750 colonies were recovered after three successive rounds of in vivo selection, and 168 isolated
ivi
clones were sequenced. The sequence analysis revealed that 37 clones encoded hypothetical proteins found in
E. coli
K-12, whereas 10 clones contained genes that had no significant homology to DNA sequences in GenBank. Two clones were found to contain transposon-related functions. Other clones contained genes required for amino acid metabolism, anaerobic respiration, DNA repair, the heat shock response, and the cellular repressor of the SOS response. In addition, one clone contained the aerobactin biosynthesis gene
iucA.
Mutations were introduced in to seven of the identified
ivi
genes. An in vivo mouse challenge-competition assay was used to determine if the mutants were attenuated. The results suggested that these
ivi
genes were important for survival in vivo, and three of the seven mutant
ivi
clones were required for successful infection of mice.
Expression of Uptake Hydrogenase and Molybdenum Nitrogenase in
Rhodobacter capsulatus
Is Coregulated by the RegB-RegA Two-Component Regulatory System
Authors: Elsen Sylvie , Dischert Wanda , Colbeau Annette , Bauer Carl E. 
Published: July 2002

ABSTRACT

Purple photosynthetic bacteria are capable of generating cellular energy from several sources, including photosynthesis, respiration, and H
2
oxidation. Under nutrient-limiting conditions, cellular energy can be used to assimilate carbon and nitrogen. This study provides the first evidence of a molecular link for the coregulation of nitrogenase and hydrogenase biosynthesis in an anoxygenic photosynthetic bacterium. We demonstrated that molybdenum nitrogenase biosynthesis is under the control of the RegB-RegA two-component regulatory system in
Rhodobacter capsulatus
. Footprint analyses and in vivo transcription studies showed that RegA indirectly activates nitrogenase synthesis by binding to and activating the expression of
nifA2
, which encodes one of the two functional copies of the
nif
-specific transcriptional activator, NifA. Expression of
nifA2
but not
nifA1
is reduced in the
reg
mutants up to eightfold under derepressing conditions and is also reduced under repressing conditions. Thus, although NtrC is absolutely required for
nifA2
expression, RegA acts as a coactivator of
nifA2
. We also demonstrated that in
reg
mutants, [NiFe]hydrogenase synthesis and activity are increased up to sixfold. RegA binds to the promoter of the hydrogenase gene operon and therefore directly represses its expression. Thus, the RegB-RegA system controls such diverse processes as energy-generating photosynthesis and H
2
oxidation, as well as the energy-demanding processes of N
2
fixation and CO
2
assimilation.
Prolonged Stationary-Phase Incubation Selects for
lrp
Mutations in
Escherichia coli
K-12
Authors: Zinser Erik R. , Kolter Roberto 
Published: July 2002

ABSTRACT

Evolution by natural selection occurs in cultures of
Escherichia coli
maintained under carbon starvation stress. Mutants of increased fitness express a growth advantage in stationary phase (GASP) phenotype, enabling them to grow and displace the parent as the majority population. The first GASP mutation was identified as a loss-of-function allele of
rpoS
, encoding the stationary-phase global regulator, ς
S
(M. M. Zambrano, D. A. Siegele, M. A. Almirón, A. Tormo, and R. Kolter, Science 259:1757–1760, 1993). We now report that a second global regulator, Lrp, can also play a role in stationary-phase competition. We found that a mutant that took over an aged culture of an
rpoS
strain had acquired a GASP mutation in
lrp
. This GASP allele,
lrp-1141
, encodes a mutant protein lacking the critical glycine in the turn of the helix-turn-helix DNA-binding domain. The
lrp-1141
allele behaves as a null mutation when in single copy and is dominant negative when overexpressed. Hence, the mutant protein appears to retain stability and the ability to dimerize but lacks DNA-binding activity. We also demonstrated that a
lrp
null allele generated by a transposon insertion has a fitness gain identical to that of the
lrp-1141
allele, verifying that cells lacking Lrp activity have a competitive advantage during prolonged starvation. Finally, we tested by genetic analysis the hypothesis that the
lrp-1141
GASP mutation confers a fitness gain by enhancing amino acid catabolism during carbon starvation. We found that while amino acid catabolism may play a role, it is not necessary for the
lrp
GASP phenotype, and hence the
lrp
GASP phenotype is due to more global physiological changes.
Function of the ς
E
Regulon in Dead-Cell Lysis in Stationary-Phase
Escherichia coli
Authors: Nitta Takeshi , Nagamitsu Hiroshi , Murata Masayuki , Izu Hanae , Yamada Mamoru 
Published: July 2002

ABSTRACT

Elevation of active ς
E
levels in
Escherichia coli
by either repressing the expression of
rseA
encoding an anti-ς
E
factor or cloning
rpoE
in a multicopy plasmid, led to a large decrease in the number of dead cells and the accumulation of cellular proteins in the medium in the stationary phase. The numbers of CFU, however, were nearly the same as those of the wild type or cells devoid of the cloned gene. In the wild-type cells,
rpoE
expression was increased in the stationary phase and a low-level release of intracellular proteins was observed. These results suggest that dead cell lysis in stationary-phase
E. coli
occurs in a ς
E
-dependent fashion. We propose there is a novel physiological function of the ς
E
regulon that may guarantee cell survival in prolonged stationary phase by providing nutrients from dead cells for the next generation.
Role of
Azotobacter vinelandii mucA
and
mucC
Gene Products in Alginate Production
Authors: Núñez Cinthia , León Renato , Guzmán Josefina , Espı́n Guadalupe , Soberón-Chávez Gloria 
Published: July 2002

ABSTRACT

Azotobacter vinelandii
produces the exopolysaccharide alginate, which is essential for its differentiation to desiccation-resistant cysts. In different bacterial species, the alternative sigma factor ς
E
regulates the expression of functions related to the extracytoplasmic compartments. In
A. vinelandii
and
Pseudomonas aeruginosa
, the ς
E
factor (AlgU) is essential for alginate production. In both bacteria, the activity of this sigma factor is regulated by the product of the
mucA
,
mucB
,
mucC
, and
mucD
genes. In this work, we studied the transcriptional regulation of the
A. vinelandii algU-mucABCD
gene cluster, as well as the role of the
mucA
and
mucC
gene products in alginate production. Our results show the existence of AlgU autoregulation and show that both MucA and MucC play a negative role in alginate production.