bluuebunny/crossref_metadata_2025_split huggingface dataset:
Conservation of Outer Membrane Protein E among Strains of
Moraxella catarrhalis
Authors: Murphy Timothy F. , Brauer Aimee L. , Yuskiw Norine , McNamara Erin R. , Kirkham Charmaine 
Published: July 2002

ABSTRACT

Outer membrane protein E (OMP E) is a 50-kDa protein of
Moraxella catarrhalis
which has several features that suggest that the protein may be an effective vaccine antigen. To assess the conservation of OMP E among strains of
M. catarrhalis,
22 isolates were studied with eight monoclonal antibodies which recognize epitopes on different regions of the protein. Eighteen of 22 strains were reactive with all eight antibodies. The sequences of
ompE
from 16 strains of
M. catarrhalis
were determined, including the 4 strains which were nonreactive with selected monoclonal antibodies. Analysis of sequences indicate a high degree of conservation among strains, with sequence differences clustered in limited regions of the gene. To assess the stability of
ompE
during colonization of the human respiratory tract, the sequences of
ompE
of isolates collected from patients colonized with the same strain for 3 to 9 months were determined. The sequences remained unchanged. These results indicate that OMP E is highly conserved among strains of
M. catarrhalis,
and preliminary studies indicate that the gene which encodes OMP E remains stable during colonization of the human respiratory tract.
Intrachromosomal Recombination within the
vsp
Locus of
Mycoplasma bovis
Generates a Chimeric Variable Surface Lipoprotein Antigen
Authors: Lysnyansky Inessa , Ron Yael , Sachse Konrad , Yogev David 
Published: July 2002

ABSTRACT

A family of 13 related but divergent
vsp
genes was recently found in the chromosome of the bovine pathogen
Mycoplasma bovis
. The
vsp
genomic locus was shown to undergo high-frequency rearrangements and to mediate phenotypic switching of variable lipoprotein antigens (Vsps) on the mycoplasma cell surface. Here we report that the
vsp
gene repertoire is subject to changes. Genetic analysis of
M. bovis
clonal isolates displaying distinct Vsp phenotypes showed that an intergenic recombination event between two closely related members of the
vsp
gene family, the formerly expressed
vspA
gene and the
vspO
gene, led to the formation of a new chimeric and functional
vsp
gene,
vspC
. The 5′ end of the recombination event was identified within the highly conserved
vsp
-upstream region, while the 3′ end was localized within the first repetitive domain (R
A
1) present in both
vspA
and
vspO
structural genes. As a result, the
vspC
gene is an embodiment of the following domains: an N-terminus-encoding region linked to the highly conserved
vsp
-upstream region provided by the
vspO
gene; and a C-terminus-encoding region and the more distal and divergent
vsp
-upstream region acquired from the
vspA
gene. The generation of chimeric genes encoding surface antigens may provide an important element of genetic variation and an additional source of antigenic diversification within the mycoplasma population.
Haemophilus ducreyi
Lipooligosaccharide Mutant Defective in Expression of β-1,4-Glucosyltransferase Is Virulent in Humans
Authors: Young Royden S. , Filiatrault Melanie J. , Fortney Kate R. , Hood Antoinette F. , Katz Barry P. , Munson Robert S. , Campagnari Anthony A. , Spinola Stanley M. 
Published: July 2002

ABSTRACT

The lipooligosaccharide (LOS) of
Haemophilus ducreyi
contains a major glycoform that is immunochemically identical to paragloboside, a glycosphingolipid precursor of major human blood group antigens. We recently identified the gene responsible for the glucosyltransferase activity and constructed an isogenic mutant (35000glu-) deficient in this activity. 35000glu- makes an LOS that consists only of the heptose trisaccharide core and 2-keto-deoxyoctulosonic acid (KDO). For this study, the mutant was reconstructed in the 35000HP (human passaged [HP]) background. Five human subjects were inoculated with 35000HP and 35000HPglu- in a dose-response trial. The pustule formation rates were 40% (95% confidence interval [CI], 13.7 to 72.6%) at 10 sites for 35000HP and 46.7% (95% CI, 24.8 to 69.9%) at 15 sites for 35000HPglu-. The histopathology and recovery rates of
H. ducreyi
from surface cultures and biopsies obtained from mutant and parent sites were similar. These results indicate that the expression of glycoforms with sugar moieties extending beyond the heptose trisaccharide core is not required for pustule formation by
H. ducreyi
in humans.
Extracellular Arginine Aminopeptidase from
Streptococcus gordonii
FSS2
Authors: Goldstein J. M. , Nelson D. , Kordula T. , Mayo J. A. , Travis J. 
Published: July 2002

ABSTRACT

Streptococcus gordonii
is a primary etiological agent in the development of subacute bacterial endocarditis (SBE), producing thrombus formation and tissue damage on the surfaces of heart valves. This is ironic, considering its normal role as a benign inhabitant of the oral microflora. However, strain FSS2 of
S. gordonii
has been found to produce several extracellular aminopeptidase- and fibrinogen-degrading activities during growth in a pH-controlled batch culture. In this report, we describe the purification, characterization, and partial cloning of a predicted serine class arginine aminopeptidase (RAP) with some cysteine class characteristics. Isolation of this enzyme by anion-exchange, gel filtration, and isoelectric focusing chromatography yielded a protein monomer of approximately 70 kDa, as shown by matrix-assisted laser desorption ionization, gel filtration, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis under denaturing conditions. Nested-PCR cloning enabled the isolation of a 324-bp-long DNA fragment encoding the 108-amino-acid N terminus of RAP. Culture activity profiles and N-terminal sequence analysis indicated the export of this protein from the cell surface. Homology was found with a putative dipeptidase from
Streptococcus pyogenes
and nonspecific dipeptidases from
Lactobacillus helveticus
and
Lactococcus lactis
. We believe that RAP may serve as a critical factor for arginine acquisition during nutrient stress in vivo and also in the proteolysis of host proteins and peptides during SBE pathology.
A Superoxide Dismutase C Mutant of
Haemophilus ducreyi
Is Virulent in Human Volunteers
Authors: Bong Cliffton T. H. , Fortney Kate R. , Katz Barry P. , Hood Antoinette F. , Mateo Lani R. San , Kawula Thomas H. , Spinola Stanley M. 
Published: July 2002

ABSTRACT

Haemophilus ducreyi
produces a periplasmic copper-zinc superoxide dismutase (Cu-Zn SOD), which is thought to protect the organism from exogenous reactive oxygen species generated by neutrophils during an inflammatory response. We had previously identified the gene,
sodC
, responsible for the production and secretion of Cu-Zn SOD and constructed an isogenic
H. ducreyi
strain with a mutation in the
sodC
gene (35000HP-
sodC-cat
). Compared to the parent, the mutant does not survive in the presence of exogenous superoxide (L. R. San Mateo, M. Hobbs, and T. H. Kawula, Mol. Microbiol. 27:391-404, 1998) and is impaired in the swine model of
H. ducreyi
infection (L. R. San Mateo, K. L. Toffer, P. E. Orndorff, and T. H. Kawula, Infect. Immun. 67:5345-5351, 1999). To test whether Cu-Zn SOD is important for bacterial survival in vivo, six human volunteers were experimentally infected with 35000HP and 35000HP-
sodC-cat
and observed for papule and pustule formation. Papules developed at similar rates at sites inoculated with the mutant or parent. The pustule formation rates were 75% (95% confidence intervals [CI], 43 to 95%) at 12 parent-inoculated sites and 67% (95% CI, 41 to 88%) at 18 mutant-inoculated sites (
P
= 0.47). There was no significant difference in levels of
H. ducreyi
recovery from mutant- and parent-inoculated biopsy sites. These results suggest that expression of Cu-Zn SOD does not play a major role in the survival of this pathogen in the initial stages of experimental infection of humans.
Antibodies against a Synthetic Peptide of SagA Neutralize the Cytolytic Activity of Streptolysin S from Group A Streptococci
Authors: Dale James B. , Chiang Edna Y. , Hasty David L. , Courtney Harry S. 
Published: July 2002

ABSTRACT

Virtually all group A streptococci (GAS) produce streptolysin S (SLS), a cytolytic toxin that is responsible for the beta-hemolysis surrounding colonies of the organisms grown on blood agar. SLS is an important virulence determinant of GAS, and recent studies have identified a nine-gene locus that is responsible for synthesis and transport of the toxin. SLS is not immunogenic; thus, no neutralizing antibodies are evoked during the course of natural infection. In the present study, we show that a synthetic peptide containing amino acid residues 10 to 30 of the putative SLS (SagA) propeptide [SLS(10-30)] coupled to keyhole limpet hemocyanin evoked antibodies in rabbits that completely neutralized the hemolytic activity of the toxin in vitro. Inhibition of hemolysis was reversed by preincubation of the immune serum with soluble, unconjugated peptide, indicating the specificity of the antibodies. In addition, antibodies that were affinity purified over an SLS(10-30) peptide column completely inhibited SLS-mediated hemolysis. The SLS(10-30) antisera did not opsonize group A streptococci; however, when combined with type-specific M protein antisera, the SLS antibodies significantly enhanced phagocytosis mediated by M protein antibodies. Thus, we have shown for the first time that it is possible to raise neutralizing antibodies against one of the most potent bacterial cytolytic toxins known. Our data also provide convincing evidence that the
sagA
gene actually encodes the SLS peptide of GAS. The synthetic peptide may prove to be an important component of vaccines designed to prevent GAS infections.
A Promoter Region Binding Protein and DNA Gyrase Regulate Anaerobic Transcription of
nifLA
in
Enterobacter cloacae
Authors: Hu Biao , Zhu Jiabi , Shen San Chiun , Yu Guan-qiao 
Published: July 2002

ABSTRACT

Our work provides evidence that a sequence characteristic of FNR binding sites, when interacted with by a
trans
-acting factor, activates anaerobic transcription of the
nifLA
operon in
Enterobacter cloacae
. DNA gyrase activity has been found to be important for the anaerobic transcription of the
nifLA
promoter. Our results suggest that anaerobic regulation of the
nifLA
operon is mediated through the control of the promoter region-binding
trans
-acting factor at the transcriptional level, while DNA supercoiling functions in providing a topological requirement for the activation of transcription.
Simultaneous Identification of Two Cyclohexanone Oxidation Genes from an Environmental
Brevibacterium
Isolate Using mRNA Differential Display
Authors: Brzostowicz Patricia C. , Gibson Katharine L. , Thomas Stuart M. , Blasko Mary Sue , Rouvière Pierre E. 
Published: July 2002

ABSTRACT

The technique of mRNA differential display was used to identify simultaneously two metabolic genes involved in the degradation of cyclohexanone in a new halotolerant
Brevibacterium
environmental isolate. In a strategy based only on the knowledge that cyclohexanone oxidation was inducible in this strain, the mRNA population of cells exposed to cyclohexanone was compared to that of control cells using reverse transcription-PCR reactions primed with a collection of 81 arbitrary oligonucleotides. Three DNA fragments encoding segments of flavin monooxygenases were isolated with this technique, leading to the identification of the genes of two distinct cyclohexanone monooxygenases, the enzymes responsible for the oxidation of cyclohexanone. Each monooxygenase was expressed in
Escherichia coli
and characterized. This work validates the application of mRNA differential display for the discovery of new microbial metabolic genes.
Analysis of
tnrA
Alleles Which Result in a Glucose-Resistant Sporulation Phenotype in
Bacillus subtilis
Authors: Shin Byung-Sik , Choi Soo-Keun , Smith Issar , Park Seung-Hwan 
Published: July 2002

ABSTRACT

Bacillus subtilis
cells cannot sporulate in the presence of catabolites such as glucose. During the analysis of Tn
10
-generated mutants, we found that deletion of the C-terminal region of the
tnrA
gene, which encodes a global regulator that positively regulates a number of genes in response to nitrogen limitation, results in a catabolite-resistant sporulation phenotype. Analyses of
nrg-lacZ
and
nasB-lacZ
, which are activated by TnrA under nitrogen limitation, showed that C-terminally truncated TnrA activates nitrogen-regulated genes constitutively. The relief of catabolite repression of sporulation may result from the uncontrolled expression of the TnrA-regulated genes.
Catabolite Repression and Induction of the Mg
2+
-Citrate Transporter CitM of
Bacillus subtilis
Authors: Warner Jessica B. , Krom Bastiaan P. , Magni Christian , Konings Wil N. , Lolkema Juke S. 
Published: July 2002

ABSTRACT

In
Bacillus subtilis
the
citM
gene encodes the Mg
2+
-citrate transporter. A target site for carbon catabolite repression (
cre
site) is located upstream of
citM
. Fusions of the
citM
promoter region, including the
cre
sequence, to the β-galactosidase reporter gene were constructed and integrated into the
amyE
site of
B. subtilis
to study catabolic effects on
citM
expression. In parallel with β-galactosidase activity, the uptake of Ni
2+
-citrate in whole cells was measured to correlate
citM
promoter activity with the enzymatic activity of the CitM protein. In minimal media, CitM was only expressed when citrate was present. The presence of glucose in the medium completely repressed
citM
expression; repression was also observed in media containing glycerol, inositol, or succinate-glutamate. Studies with
B. subtilis
mutants defective in the catabolite repression components HPr, Crh, and CcpA showed that the repression exerted by all these medium components was mediated via the carbon catabolite repression system. During growth on inositol and succinate, the presence of glutamate strongly potentiated the repression of
citM
expression by glucose. A reasonable correlation between
citM
promoter activity and CitM transport activity was observed in this study, indicating that the Mg
2+
-citrate uptake activity of
B. subtilis
is mainly regulated at the transcriptional level.
Involvement of ς
S
in Starvation-Induced Transposition of
Pseudomonas putida
Transposon Tn
4652
Authors: Ilves Heili , Hõrak Rita , Kivisaar Maia 
Published: July 2002

ABSTRACT

Transpositional activity of mobile elements can be induced by different environmental stresses. Here, we present evidence that transposition of Tn
4652
is elevated in stationary-phase
Pseudomonas putida
and suppressed in an isogenic ς
S
-defective strain. We demonstrate that transcription from the Tn
4652
transposase promoter is controlled by the stationary-phase-specific sigma factor ς
S
. To our knowledge, this is the first example of direct stationary-phase-specific regulation of a mobile element transposase. Data presented in this report support the idea that activation of transposition under stressful conditions could be an inducible process.
Ancestral Divergence, Genome Diversification, and Phylogeographic Variation in Subpopulations of Sorbitol-Negative, β-Glucuronidase-Negative Enterohemorrhagic
Escherichia coli
O157
Authors: Kim Jaehyoung , Nietfeldt Joseph , Ju Jingliang , Wise John , Fegan Narelle , Desmarchelier Patricia , Benson Andrew K. 
Published: July 2002

ABSTRACT

The O157:H7 lineage of enterohemorrhagic
Escherichia coli
is a geographically disseminated complex of highly related genotypes that share common ancestry. The common clone that is found worldwide carries several markers of events in its evolution, including markers for acquisition of virulence genes and loss of physiological characteristics, such as sorbitol fermentation ability and β-glucuronidase production. Populations of variants that are distinct with respect to motility and the sorbitol and β-glucuronidase markers appear to have diverged at several points along the inferred evolutionary pathway. In addition to these variants, distinct subpopulations of the contemporary non-sorbitol-fermenting, β-glucuronidase-negative O157:H7 clone were recently detected among bovine and human clinical isolates in the United Stares by using high-resolution genome comparison. In order to determine if these recently described subpopulations were derived from a regional or ancestral divergence event, we used octamer-based genome scanning, marker sorting, and DNA sequence analysis to examine their phylogenetic relationship to populations of non-sorbitol-fermenting, β-glucuronidase negative O157:H7 and O157:H− strains from Australia. The inferred phylogeny is consistent with the hypothesis that subpopulations on each continent resulted from geographic spread of an ancestral divergence event and subsequent expansion of distinct subpopulations. Marker sorting and DNA sequence analyses identified sets of monophyletic markers consistent with the pattern of divergence and demonstrated that phylogeographic variation occurred through emergence of regional subclones and concentration of regional polymorphisms among distinct subpopulations. DNA sequence analysis of representative polyphyletic markers showed that genome diversity accrued through random drift and bacteriophage-mediated events.
Type 1 Capsule Genes of
Staphylococcus aureus
Are Carried in a Staphylococcal Cassette Chromosome Genetic Element
Authors: Luong Thanh T. , Ouyang Shu , Bush Kelly , Lee Chia Y. 
Published: July 2002

ABSTRACT

The
cap1
genes are required for the synthesis of type 1 capsular polysaccharide (CP1) in
Staphylococcus aureus
. We previously showed that the
cap1
locus was associated with a discrete genetic element in
S. aureus
M. In this report, we defined the boundaries of the
cap1
element by comparing its restriction pattern to that of a corresponding region from the CP1-negative strain Becker. The element was located in the
Sma
I-G chromosomal fragment of the standard mapping strain NCTC8325. The sequences of the entire
cap1
element and the flanking regions were determined. We found that there were two additional
cap1
genes not previously identified. The
cap1
operon was located in a staphylococcal cassette chromosome (SCC) element similar to the resistance island SCC
mec
recently described for methicillin resistance in
S. aureus
. Notably, the SCC
cap1
element was located at the same insertion site as all the SCC
mec
elements in the staphylococcal chromosome. The excision of SCC
cap1
could be demonstrated only in the presence of the recombinase genes from an SCC
mec
element, verifying that SCC
cap1
is a genuine SCC element but defective in mobilization. A novel enterotoxin gene, whose transcript was detected by Northern blotting, was found next to the SCC
cap1
locus. We propose that the enterotoxin gene and SCC
cap1
were inserted into this locus at the juxtaposition by independent events. Sequence comparison revealed numerous DNA rearrangements and mutations in SCC
cap1
and the left flanking region, suggesting that the SCC
cap1
had been inserted at the SCC
attC
site a long time ago. In addition, most genes in this region were incomplete, with the exception of the 15
cap1
genes, implying that the
cap1
genes confer a survival advantage on strain M.
Control of Anthrax Toxin Gene Expression by the Transition State Regulator
abrB
Authors: Saile Elke , Koehler Theresa M. 
Published: July 2002

ABSTRACT

Bacillus anthracis
produces the anthrax toxin proteins protective antigen (PA), lethal factor (LF), and edema factor (EF) in a growth phase-dependent manner when cultured in liquid medium. Expression of the toxin genes
pagA
,
lef
, and
cya
peaks in late log phase, and steady-state levels of the toxin proteins are highest during the transition into stationary phase. Here we show that an apparent transition state regulator negatively regulates toxin gene expression. We identified two orthologues of the
B. subtilis
transition state regulator
abrB
in the
B. anthracis
genome: one on the chromosome and one on the 182-kb virulence plasmid pXO1. The orthologue located on the chromosome is predicted to encode a 94-amino-acid protein that is 85% identical to
B. subtilis
AbrB. The hypothetical protein encoded on pXO1 is 41% identical to
B. subtilis
AbrB but missing 27 amino acid residues from the amino terminus compared to the
B. subtilis
protein. Deletion of the pXO1-encoded
abrB
orthologue did not affect toxin gene expression under the conditions tested. However, a
B. anthracis
mutant in which the chromosomal
abrB
gene was deleted expressed
pagA
earlier and at a higher level than the parent strain. Expression of a transcriptional
pagA-lacZ
fusion in the
abrB
mutant was increased up to 20-fold during early exponential growth compared to the parent strain and peaked in mid-exponential rather than late exponential phase. In contrast to the strong effect of
abrB
on
pagA
expression,
lef-lacZ
and
cya-lacZ
expression during early-log-phase growth was increased only two- to threefold in the
abrB
null mutant. Western hybridization analysis showed increased PA, LF, and EF synthesis by the mutant. As is true in
B. subtilis
, the
B. anthracis abrB
gene is negatively regulated by
spo0A
. Our findings tie anthrax toxin gene expression to the complex network of postexponential phase adaptive responses that have been well studied in
B. subtilis
.
Monitoring Resistance to Human Immunodeficiency Virus Type 1 Protease Inhibitors by Pyrosequencing
Authors: O'Meara Deirdre , Wilbe Karin , Leitner Thomas , Hejdeman Bo , Albert Jan , Lundeberg Joakim 
Published: July 2002

ABSTRACTThe emergence of drug-resistant viral variants is the inevitable consequence of incomplete suppression of human immunodeficiency virus type 1 (HIV-1) replication during treatment with antiretroviral drugs. Sequencing to determine the resistance profiles of these variants has become increasingly important in the clinical management of HIV-1 patients, both in the initial design of a therapeutic plan and in selecting a salvage regimen. Here we have developed a pyrosequencing assay for the rapid characterization of resistance to HIV-1 protease inhibitors (PIs). Twelve pyrosequencing primers were designed and were evaluated on the MN strain and on viral DNA from peripheral blood mononuclear cells from eight untreated HIV-1-infected individuals. The method had a limit of detection of 20 to 25% for minor sequence variants. Pattern recognition (i.e., comparing actual sequence data with expected wild-type and mutant sequence patterns) simplified the identification of minor sequence variants. This real-time pyrosequencing method was applied in a longitudinal study monitoring the development of PI resistance in plasma samples obtained from four patients over a 2 1/2-year period. Pyrosequencing identified eight primary PI resistance mutations as well as several secondary mutations. This sequencing approach allows parallel analysis of 96 reactions in 1 h, facilitating the monitoring of drug resistance in eight patients simultaneously and, in combination with viral load analysis, should be a useful tool in the future to monitor HIV-1 during therapy.