bluuebunny/crossref_metadata_2025_split huggingface dataset:
Enterotoxin Plasmid from
Clostridium perfringens
Is Conjugative
Authors: Brynestad Sigrid , Sarker Mahfuzur R. , McClane Bruce A. , Granum Per Einar , Rood Julian I. 
Published: July 2002

ABSTRACT

Clostridium perfringens
enterotoxin is the major virulence factor involved in the pathogenesis of
C. perfringens
type A food poisoning and several non-food-borne human gastrointestinal illnesses. The enterotoxin gene,
cpe
, is located on the chromosome of food-poisoning isolates but is found on a large plasmid in non-food-borne gastrointestinal disease isolates and in veterinary isolates. To evaluate whether the
cpe
plasmid encodes its own conjugative transfer, a
C. perfringens
strain carrying pMRS4969, a plasmid in which a 0.4-kb segment internal to the
cpe
gene had been replaced by the chloramphenicol resistance gene
catP
, was used as a donor in matings with several
cpe
-negative
C. perfringens
isolates. Chloramphenicol resistance was transferred at frequencies ranging from 2.0 × 10
−2
to 4.6 × 10
−4
transconjugants per donor cell. The transconjugants were characterized by PCR, pulsed-field gel electrophoresis, and Southern hybridization analyses. The results demonstrated that the entire pMRS4969 plasmid had been transferred to the recipient strain. Plasmid transfer required cell-to-cell contact and was DNase resistant, indicating that transfer occurred by a conjugation mechanism. In addition, several fragments of the prototype
C. perfringens
tetracycline resistance plasmid, pCW3, hybridized with pMRS4969, suggesting that pCW3 shares some similarity to pMRS4969. The clinical significance of these findings is that if conjugative transfer of the
cpe
plasmid occurred in vivo, it would have the potential to convert
cpe
-negative
C. perfringens
strains in normal intestinal flora into strains capable of causing gastrointestinal disease.
EspG, a Novel Type III System-Secreted Protein from Enteropathogenic
Escherichia coli
with Similarities to VirA of
Shigella flexneri
Authors: Elliott Simon J. , Krejany Efrosinia O. , Mellies Jay L. , Robins-Browne Roy M. , Sasakawa Chihiro , Kaper James B. 
Published: July 2002

ABSTRACT

The function of the
rorf2
gene located on the locus of enterocyte effacement (LEE) pathogenicity island of enteropathogenic
Escherichia coli
(EPEC) has not been described. We report that
rorf2
encodes a novel protein, named EspG, which is secreted by the type III secretory system and which is translocated into host epithelial cells. EspG is homologous with
Shigella flexneri
protein VirA, and the cloned
espG
(
rorf2
) gene can rescue invasion in a
Shigella virA
mutant, indicating that these proteins are functionally equivalent in
Shigella
. An EPEC
espG
mutant had no apparent defects in in vitro assays of virulence phenotypes, but a rabbit diarrheagenic
E. coli
strain carrying a mutant
espG
showed diminished intestinal colonization and yet diarrheal attack rates similar to those of the wild type. A second EspG homolog, Orf3, is encoded on the EspC pathogenicity islet. The cloned
orf3
gene could also rescue invasion in a
Shigella virA
mutant, but an EPEC
espG orf3
double mutant was not diminished in any tested in vitro assays for EPEC virulence factors. Our results indicate that EspG plays an accessory but as yet undefined role in EPEC virulence that may involve intestinal colonization.
Antigens of
Mycobacterium tuberculosis
Expressed during Preclinical Tuberculosis: Serological Immunodominance of Proteins with Repetitive Amino Acid Sequences
Authors: Singh K. K. , Zhang X. , Patibandla A. S. , Chien P. , Laal S. 
Published: July 2002

ABSTRACT

Four antigens of
Mycobacterium tuberculosis
that are expressed in vivo after aerosol infection but prior to the development of clinical tuberculosis (TB) in rabbits were identified by immunoscreening of an expression library of
M. tuberculosis
genomic DNA with sera obtained 5 weeks postinfection. Three of the proteins identified, PirG (Rv3810), polymorphic GC-repetitive sequence (PE-PGRS; Rv3367), and proline-threonine repetitive protein (PTRP) (Rv0538), have multiple tandem repeats of unique amino acid sequences and have characteristics of surface or secreted proteins. The fourth protein, MtrA (Rv3246c), is a response regulator of a putative two-component signal transduction system,
mtrA
-
mtrB,
of
M. tuberculosis
. All four antigens were recognized by pooled sera from TB patients and not from healthy controls, confirming their in vivo expression during active infection in humans. Three of the antigens (PE-PGRS, PTRP, and MtrA) were also recognized by retrospective preclinical TB sera obtained, prior to the clinical manifestation of TB, from human immunodeficiency virus-TB patients, suggesting that they are potential candidates for devising diagnostic tests for active, preclinical TB.
Differences in Components at Delayed-Type Hypersensitivity Reaction Sites in Mice Immunized with Either a Protective or a Nonprotective Immunogen ofCryptococcus neoformans
Authors: Nichols Kasie L. , Bauman Sean K. , Schafer Fredda B. , Murphy Juneann W. 
Published: July 2002

ABSTRACTCell-mediated immunity is the major protective mechanism againstCryptococcus neoformans. Delayed swelling reactions, i.e., delayed-type hypersensitivity (DTH), in response to an intradermal injection of specific antigen are used as a means of detecting a cell-mediated immune (CMI) response to the antigen. We have found previously that the presence of an anticryptococcal DTH response in mice is not always indicative of protection against a cryptococcal infection. Using one immunogen that induces a protective anticryptococcal CMI response and one that induces a nonprotective response, we have shown that mice immunized with the protective immunogen undergo a classical DTH response characterized by mononuclear cell and neutrophil infiltrates and the presence of gamma interferon and NO. In contrast, immunization with the nonprotective immunogen results in an influx of primarily neutrophils and production of tumor necrosis factor alpha (TNF-α) at the DTH reaction site. Even when the anticryptococcal DTH response was augmented by blocking the down-regulator, CTLA-4 (CD152), on T cells in the mice given the nonprotective immunogen, the main leukocyte population infiltrating the DTH reaction site is the neutrophil. Although TNF-α is increased at the DTH reaction site in mice immunized with the nonprotective immunogen, it is unlikely that TNF-α activates the neutrophils, because the density of TNF receptors on the neutrophils is reduced below control levels. Uncoupling of DTH reactivity and protection has been demonstrated in other infectious-disease models; however, the mechanisms differ from our model. These findings stress the importance of defining the cascade of events occurring in response to various immunogens and establishing the relationships between protection and DTH reactions.
Immunogenicity and Safety Testing of a Group B Intranasal Meningococcal Native Outer Membrane Vesicle Vaccine
Authors: Katial Rohit K. , Brandt Brenda L. , Moran Ellen E. , Marks Stephen , Agnello Victor , Zollinger Wendell D. 
Published: July 2002

ABSTRACTThe presently licensed meningococcal vaccine is a tetravalent capsular polysaccharide vaccine that induces immunity to serogroups A, C, Y, and W-135 but not to group B, which causes nearly half of the meningitis cases in the United States. The purpose of this study was to evaluate the safety and immunogenicity of an intranasal native outer membrane vesicle (NOMV) vaccine prepared from a capsule negative strain of group B ofNeisseria meningitidis.In this study all volunteers received the same dose of vaccine, but we evaluated two different immunization schedules and the oropharyngeal and intranasal routes of vaccine delivery, assessed nasal cytology for cellular infiltration, and measured antibody-secreting cells (enzyme-linked immunospot assay [ELISPOT]) as an early marker for systemic immune response. Additionally, both intranasal and serum vaccine-specific antibodies were measured as well as serum bactericidal activity. Four groups with a total of 42 subjects were immunized on days 0, 28, and 56. Group 3 received an additional dose on day 7. Group 2 subjects were immunized both intranasally and oropharyngeally. Group 4 received a different lot of vaccine. All groups received approximately 1,200 μg of vaccine per subject. Patients were evaluated for side effects. The vaccine was well tolerated without evidence of inflammation on nasal cytology. The group receiving the extra vaccine dose showed the maximum increase in bactericidal activity. Thirty of 42 subjects demonstrated an increase in meningococcus-specific intranasal immunoglobulin A (IgA) titers, while 23 of 42 demonstrated an increase in specific IgG titers. The group receiving vaccine intranasally and oropharyngeally showed the highest rise in intranasal titers for both IgA and IgG. Groups 1, 3, and 4 showed a significant increase in antibody-secreting cells on ELISPOT. Eighteen of 42 volunteers demonstrated a fourfold or greater rise in bactericidal titers, with 81% showing an increase over baseline. We have demonstrated the immunogenicity and safety of a group B lipopolysaccharide-containing, intranasal, NOMV vaccine.
Modulation of Mouse Endotoxic Fever by Complement
Authors: Li S. , Holers V. M. , Boackle S. A. , Blatteis C. M. 
Published: July 2002

ABSTRACTIt was recently reported that the complement system may be critically involved in the febrile response of guinea pigs to systemic, particularly intraperitoneally (i.p.) injected, lipopolysaccharides (LPS). The present study was designed to identify which component(s) of the complement cascade may be specifically critical. To this end, we used mice with C3, C5, and CR2 gene deletions. To assess preliminarily the suitability of mice for such a study, we replicated our earlier studies with guinea pigs. Thus, to verify initially whether complement is similarly involved in the febrile response of wild-type (C57BL/6J) mice to i.p. LPS (Escherichia coli, 1 μg/mouse), we depleted complement with cobra venom factor (CVF; 7 U/mouse, intravenously [i.v.]). These animals did not develop fever, whereas the core temperature (Tc) of CVF vehicle-treated controls rose ∼1°C by 80 min postinjection and then gradually abated over the following 2.5 h, confirming the involvement of complement in fever production after i.p. LPS injection and the suitability of this species for these studies. C3- and C5-sufficient (C3+/+and C5+/+) mice also developed 1°C fevers within 80 min after i.p. LPS (1 or 2 μg/mouse) injection. These fevers were totally prevented by CVF (10 U/mouse, i.v.) pretreatment. C3- and C5-deficient (C3−/−and C5−/−) mice were also unable to developTcrises after i.p. LPS. Both CR2+/+and CR2−/−mice responded normally to i.p. LPS (1 μg/mouse). These data indicate that C5, but not C3d acting through CR2, may play a critical role in the febrile response of mice to i.p. LPS.
Malaria-Induced Acquisition of Antibodies toPlasmodium falciparumVariant Surface Antigens
Authors: Ofori Michael F. , Dodoo Daniel , Staalsoe Trine , Kurtzhals Jørgen A. L. , Koram Kwadwo , Theander Thor G. , Akanmori Bartholomew D. , Hviid Lars 
Published: July 2002

ABSTRACTIn areas of intensePlasmodium falciparumtransmission, protective immunity is acquired during childhood in parallel with acquisition of agglutinating antibodies to parasite-encoded variant surface antigens (VSA) expressed on parasitized red blood cells. In a semi-immune child in such an area, clinical disease is caused mainly by parasites expressing VSA not recognized by preexisting VSA-specific antibodies in that child. Such malaria episodes are known to cause an increase in agglutinating antibodies specifically recognizing VSA expressed by the parasite isolate causing the illness, whereas antibody responses to other parasite isolates are relatively unaffected. However, the detailed kinetics of this VSA antibody acquisition are unknown and hence were the aim of this study. We show thatP. falciparummalaria in Ghanaian children generally caused a rapid and sustained increase in variant-specific VSA antibody levels, while more transient and limited increases in levels of antibodies to VSA expressed by other parasite isolates were also seen. Plasma VSA antibody levels were positively correlated with the age of the healthy plasma donors but negatively correlated with the age of the parasite donors (the malaria patient). The data from this first detailed longitudinal study of acquisition of VSA antibodies support the hypothesis that naturally acquired protective immunity toP. falciparummalaria is mediated, at least in part, by VSA-specific antibodies.
Conversion of 4-Hydroxyacetophenone into 4-Phenyl Acetate by a Flavin Adenine Dinucleotide-Containing Baeyer-Villiger-Type Monooxygenase
Authors: Tanner Adam , Hopper David J. 
Published: July 2002

ABSTRACT

An arylketone monooxygenase was purified from
Pseudomonas putida
JD1 by ion exchange and affinity chromatography. It had the characteristics of a Baeyer-Villiger-type monooxygenase and converted its substrate, 4-hydroxyacetophenone, into 4-hydroxyphenyl acetate with the consumption of one molecule of oxygen and oxidation of one molecule of NADPH per molecule of substrate. The enzyme was a monomer with an
M
r
of about 70,000 and contained one molecule of flavin adenine dinucleotide (FAD). The enzyme was specific for NADPH as the electron donor, and spectral studies showed rapid reduction of the FAD by NADPH but not by NADH. Other arylketones were substrates, including acetophenone and 4-hydroxypropiophenone, which were converted into phenyl acetate and 4-hydroxyphenyl propionate, respectively. The enzyme displayed Michaelis-Menten kinetics with apparent

K
m

values of 47 μM for 4-hydroxyacetophenone, 384 μM for acetophenone, and 23 μM for 4-hydroxypropiophenone. The apparent

K
m

value for NADPH with 4-hydroxyacetophenone as substrate was 17.5 μM. The N-terminal sequence did not show any similarity to other proteins, but an internal sequence was very similar to part of the proposed NADPH binding site in the Baeyer-Villiger monooxygenase cyclohexanone monooxygenase from an
Acinetobacter
sp.
Metabolic Signals Trigger Glucose-Induced Inactivation of Maltose Permease in
Saccharomyces
Authors: Jiang Hua , Medintz Igor , Zhang Bin , Michels Corinne A. 
Published: July 2002

ABSTRACT

Organisms such as
Saccharomyces
capable of utilizing several different sugars selectively ferment glucose when less desirable carbon sources are also available. This is achieved by several mechanisms. Glucose down-regulates the transcription of genes involved in utilization of these alternate carbon sources. Additionally, it causes posttranslational modifications of enzymes and transporters, leading to their inactivation and/or degradation. Two glucose sensing and signaling pathways stimulate glucose-induced inactivation of maltose permease. Pathway 1 uses Rgt2p as a sensor of extracellular glucose and causes degradation of maltose permease protein. Pathway 2 is dependent on glucose transport and stimulates degradation of permease protein and very rapid inactivation of maltose transport activity, more rapid than can be explained by loss of protein alone. In this report, we characterize signal generation through pathway 2 using the rapid inactivation of maltose transport activity as an assay of signaling activity. We find that pathway 2 is dependent on
HXK2
and to a lesser extent
HXK1
. The correlation between pathway 2 signaling and glucose repression suggests that these pathways share common upstream components. We demonstrate that glucose transport via galactose permease is able to stimulate pathway 2. Moreover, rapid transport and fermentation of a number of fermentable sugars (including galactose and maltose, not just glucose) are sufficient to generate a pathway 2 signal. These results indicate that pathway 2 responds to a high rate of sugar fermentation and monitors an intracellular metabolic signal. Production of this signal is not specific to glucose, glucose catabolism, glucose transport by the Hxt transporters, or glucose phosphorylation by hexokinase 1 or 2. Similarities between this yeast glucose sensing pathway and glucose sensing mechanisms in mammalian cells are discussed.
Glutathione Is Involved in Environmental Stress Responses in
Rhizobium tropici
, Including Acid Tolerance
Authors: Riccillo Pablo M. , Muglia Cecilia I. , de Bruijn Frans J. , Roe Andrew J. , Booth Ian R. , Aguilar O. Mario 
Published: July 2002

ABSTRACT

The isolation of rhizobial strains which exhibit an intrinsic tolerance to acidic conditions has been reported and has facilitated studies on the basic mechanisms underlying acid tolerance.
Rhizobium tropici
strain CIAT899 displays a high intrinsic tolerance to acidity and therefore was used in this work to study the molecular basis of bacterial responses to acid conditions and other environmental stresses. We generated a collection of
R. tropici
CIAT899 mutants affected in acid tolerance using Tn
5-luxAB
mutagenesis, and one mutant strain (CIAT899-13T2), which fails to grow under acid conditions, was characterized in detail. Strain CIAT899-13T2 was found to contain a single Tn
5-luxAB
insertion in a gene showing a high degree of similarity with the
Escherichia coli gshB
gene, encoding the enzyme glutathione synthetase. Intracellular potassium pools and intracellular pH levels were found to be lower in the mutant than in the parent. The glutathione-deficient mutant was shown to be sensitive to weak organic acids, osmotic and oxidative stresses, and the presence of methylglyoxal. Glutathione restores responses to these stresses almost to wild-type levels. Our data show that in
R. tropici
the production of glutathione is essential for growth in extreme environmental conditions. The mutant strain CIAT899-13T2 induced effective nodules; however, it was found to be outcompeted by the wild-type strain in coinoculation experiments.
Proteins ofMycobacterium bovisBCG Induced in the Wayne Dormancy Model
Authors: Boon Calvin , Li Rong , Qi Robert , Dick Thomas 
Published: July 2002

ABSTRACTOxygen starvation triggers the shiftdown of the obligate aerobeMycobacterium bovisBCG to a state of dormancy. Two-dimensional electrophoresis showed a drastic up-regulation of the α-crystallin homolog, the putative response regulator Rv3133c, and the two conserved hypothetical proteins Rv2623 and Rv2626c in dormant bacilli.
Transcription Analysis of the
Bacillus subtilis
PucR Regulon and Identification of a
cis
-Acting Sequence Required for PucR-Regulated Expression of Genes Involved in Purine Catabolism
Authors: Beier Lars , Nygaard Per , Jarmer Hanne , Saxild Hans H. 
Published: July 2002

ABSTRACT

The PucR protein of
Bacillus subtilis
has previously been suggested to regulate the expression of 15 genes,
pucABCDE
,
pucFG
,
pucH
,
pucI
,
pucJKLM
,
pucR
, and
gde
, all of which encode proteins involved in purine catabolism. When cells are grown under nitrogen-limiting conditions, the expression of these genes is induced and intermediary compounds of the purine catabolic pathway affect this expression. By using
pucR
deletion mutants, we have found that PucR induces the expression of
pucFG
,
pucH
,
pucI
,
pucJKLM
, and
gde
while it represses the expression of
pucR
and
pucABCDE
. Deletions in the promoters of the five induced operons and genes combined with bioinformatic analysis suggested a conserved upstream activating sequence, 5′-WWWCNTTGGTTAA-3′, now named the PucR box. Potential PucR boxes overlapping the −35 and −10 regions of the
pucABCDE
promoter and located downstream of the
pucR
transcription start point were also found. The positions of these PucR boxes are consistent with PucR acting as a negative regulator of
pucABCDE
and
pucR
expression. Site-directed mutations in the PucR box upstream of
pucH
and
pucI
identified positions that are essential for the induction of
pucH
and
pucI
expression, respectively. Mutants with decreased
pucH
or increased
pucR
expression obtained from a library of clones containing random mutations in the
pucH
-to-
pucR
intercistronic region all contained mutations in or near the PucR box. The induction of
pucR
expression under nitrogen-limiting conditions was found to be mediated by the global nitrogen-regulatory protein TnrA. In other gram-positive bacteria, we have found open reading frames that encode proteins similar to PucR located next to other open reading frames encoding proteins with similarity to purine catabolic enzymes. Hence, the PucR homologues are likely to exert the same function in other gram-positive bacteria as PucR does in
B. subtilis
.
Gas Channels for NH
3
: Proteins from Hyperthermophiles Complement an
Escherichia coli
Mutant
Authors: Soupene Eric , Chu Tony , Corbin Rebecca W. , Hunt Donald F. , Kustu Sydney 
Published: July 2002

ABSTRACT

Ammonium transport (Amt) proteins appear to be bidirectional channels for NH
3
. The
amt
genes of the hyperthermophiles
Aquifex aeolicus
and
Methanococcus jannaschii
complement enteric
amtB
mutants for growth at 25 nM NH
3
at 37°C. To our knowledge, Amt proteins are the first hyperthermophilic membrane transport proteins shown to be active in a mesophilic bacterium. Despite low expression levels, His-tagged
Aquifex
Amt could be purified by heating and nickel chelate affinity chromatography. It could be studied genetically in
Escherichia coli
.
Correlation between Genotype and Phenotypic Categorization of Staphylococci Based on Methicillin Susceptibility and Resistance
Authors: Gradelski Elizabeth , Valera Lourdes , Aleksunes Lauren , Bonner Daniel , Fung-Tomc Joan 
Published: July 2002

ABSTRACT

Positive correlation between methicillin and oxacillin susceptibility test results and the detection of the
mecA
gene was observed for
Staphylococcus
aureus, S. epidermidis,
and
S. haemolyticus
as well as among
mecA
+
strains of other species of coagulase-negative staphylococci (CNS). However, at least 50% of the
mecA
-negative strains of these other species of CNS were falsely classified as methicillin and oxacillin resistant.
Molecular Analysis of Bacterial Species Associated with Childhood Caries
Authors: Becker Mitzi R. , Paster Bruce J. , Leys Eugene J. , Moeschberger Melvin L. , Kenyon Sarah G. , Galvin Jamie L. , Boches Susan K. , Dewhirst Floyd E. , Griffen Ann L. 
Published: July 2002

ABSTRACT

Although substantial epidemiologic evidence links
Streptococcus
mutans
to caries, the pathobiology of caries may involve more complex communities of bacterial species. Molecular methods for bacterial identification and enumeration now make it possible to more precisely study the microbiota associated with dental caries. The purpose of this study was to compare the bacteria found in early childhood caries (ECC) to those found in caries-free children by using molecular identification methods. Cloning and sequencing of bacterial 16S ribosomal DNAs from a healthy subject and a subject with ECC were used for identification of novel species or uncultivated phylotypes and species not previously associated with dental caries. Ten novel phylotypes were identified. A number of species or phylotypes that may play a role in health or disease were identified and warrant further investigation. In addition, quantitative measurements for 23 previously known bacterial species or species groups were obtained by a reverse capture checkerboard assay for 30 subjects with caries and 30 healthy controls. Significant differences were observed for nine species:
S
.
sanguinis
was associated with health and, in order of decreasing cell numbers,
Actinomyces
gerencseriae
,
Bifidobacterium
,
S
.
mutans
,
Veillonella
,
S
.
salivarius
,
S
.
constellatus
,
S
.
parasanguinis
, and
Lactobacillus
fermentum
were associated with caries. These data suggest that
A
.
gerencseriae
and other
Actinomyces
species may play an important role in caries initiation and that a novel
Bifidobacterium
may be a major pathogen in deep caries. Further investigation could lead to the identification of targets for biological interventions in the caries process and thereby contribute to improved prevention of and treatment for this significant public health problem.