bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Proteins from
Plasmodium falciparum
That Are Homologous to Reticulocyte Binding Proteins in
Plasmodium vivax
Authors: Triglia Tony , Thompson Jenny , Caruana Sonia R. , Delorenzi Mauro , Speed Terry , Cowman Alan F. 
Published: July 2002

ABSTRACT

Plasmodium falciparum
infections can be fatal, while
P. vivax
infections usually are not. A possible factor involved in the greater virulence of
P. falciparum
is that this parasite grows in red blood cells (RBCs) of all maturities whereas
P. vivax
is restricted to growth in reticulocytes, which represent only approximately 1% of total RBCs in the periphery. Two proteins, expressed at the apical end of the invasive merozoite stage from
P. vivax
, have been implicated in the targeting of reticulocytes for invasion by this parasite. A search of the
P. falciparum
genome databases has identified genes that are homologous to the
P. vivax rbp-1
and -
2
genes. Two of these genes are virtually identical over a large region of the 5′ end but are highly divergent at the 3′ end. They encode high-molecular-mass proteins of >300 kDa that are expressed in late schizonts and localized to the apical end of the merozoite. To test a potential role in merozoite invasion of RBCs, we analyzed the ability of these proteins to bind to mature RBCs and reticulocytes. No binding to mature RBCs or cell preparations enriched for reticulocytes was detected. We identified a parasite clone that lacks the gene for one of these proteins, showing that the gene is not required for normal in vitro growth. Antibodies to these proteins can inhibit merozoite invasion of RBCs.
Lack of Adherence of Clinical Isolates of
Pseudomonas aeruginosa
to Asialo-GM
1
on Epithelial Cells
Authors: Schroeder Torsten H. , Zaidi Tanweer , Pier Gerald B. 
Published: July 2002

ABSTRACT

Numerous studies have reported that asialo-GM
1
, gangliotetraosylceramide, or moieties serve as epithelial cell receptors for
Pseudomonas aeruginosa
. Usually this interaction is confirmed with antibodies to asialo-GM
1
. However, few, if any, of these reports have evaluated the binding of fresh clinical isolates of
P. aeruginosa
to asialo-GM
1
or the specificity of the antibodies for the asialo-GM
1
antigen. We confirmed that asialo-GM
1
dissolved in dimethyl sulfoxide could be added to the apical membrane of Madin-Darby canine kidney cells growing as a polarized epithelium on Transwell membranes (J. C. Comolli, L. L. Waite, K. E. Mostov, and J. N. Engel, Infect. Immun. 67:3207–3214, 1999) and that such treatment enhanced the binding of
P. aeruginosa
strain PA103. However, no other
P. aeruginosa
strain, including eight different clinical isolates, exhibited enhanced binding to asialo-GM
1
-treated cells. Studies with commercially available antibodies to asialo-GM
1
showed that these preparations had high titers of antibody to
P. aeruginosa
antigens, including whole cells, purified lipopolysaccharide (LPS), and pili. Inhibition studies showed that adsorption of an antiserum to asialo-GM
1
with
P. aeruginosa
cells could remove the reactivity of antibodies to asialo-GM
1
, and adsorption of this serum with asialo-GM
1
removed antibody binding to
P. aeruginosa
LPS. Antibodies in sera raised to asialo-GM
1
were observed to bind to
P. aeruginosa
cells by immunoelectron microscopy. Antibodies to asialo-GM
1
inhibited formation of a biofilm by
P. aeruginosa
in the absence of mammalian cells, indicating a direct inhibition of bacterial cell-cell interactions. These findings demonstrate that asialo-GM
1
is not a major cellular receptor for clinical isolates of
P. aeruginosa
and that commercially available antibodies raised to this antigen contain high titers of antibody to multiple
P. aeruginosa
antigens, which do not interfere with the binding of
P. aeruginosa
to mammalian cells but possibly interfere with the binding of
P. aeruginosa
cells to each other.
Implication of Mitogen-Activated Protein Kinases in T84 Cell Responses to EnteropathogenicEscherichia coliInfection
Authors: Czerucka Dorota , Dahan Stéphanie , Mograbi Baharia , Rossi Bernard , Rampal Patrick 
Published: July 2002

ABSTRACTEnteropathogenicEscherichia coli(EPEC) infection of T84 cells induces a decrease in transepithelial resistance, the formation of attaching and effacing (A/E) lesions, and cytokine production. The purpose of this study was to investigate the ability of EPEC to activate mitogen-activated protein (MAP) kinases in T84 cells and to correlate these signaling pathways with EPEC-induced cell responses. T84 cells were infected with either the wild-type (WT) EPEC strain E2348/69 or two mutants, intimin deletion strain CVD206 (ΔeaeA) and type III secretion apparatus mutant strain CVD452 (ΔescN::aphA). Infection of T84 cells with WT but not mutant EPEC strains induced tyrosine phosphorylation of several proteins in T84 cells, including the p46 and p52 Shc isoforms. Kinetics studies revealed that ERK1/2, p38, and c-Jun N-terminal kinase (JNK) MAP kinases were activated in cells infected with strain E2348/69 but not with the mutant strains. Inhibition of MAP kinases with PD98059 or SB203580 did not affect the EPEC-induced decrease in transepithelial resistance or actin accumulation beneath the WT bacteria, but these two inhibitors significantly decreased interleukin-8 (IL-8) synthesis. We demonstrate that EPEC induces activation of ERK1/2, p38, and JNK cascades, which all depend on bacterial adhesion and expression of the bacterial type III secretion system. ERK1/2 and p38 MAP kinases were equally implicated in IL-8 expression but did not participate in A/E lesion formation or transepithelial resistance modification, indicating that the signaling pathways involved in these events are distinct.
Essential Role for Cellular Phosphoglucomutase in Virulence of Type 3
Streptococcus pneumoniae
Authors: Hardy Gail G. , Magee Ashalla D. , Ventura Christy L. , Caimano Melissa J. , Yother Janet 
Published: July 2002

ABSTRACT

Synthesis of the
Streptococcus pneumoniae
type 3 capsule requires the pathway glucose-6-phosphate (Glc-6-P) → Glc-1-P → UDP-Glc → UDP-glucuronic acid (UDP-GlcUA) → (GlcUA-Glc)

n

. The UDP-Glc dehydrogenase and synthase necessary for the latter two steps, and essential for capsule production, are encoded by genes (
cps3D
and
cps3S
, respectively) located in the type 3 capsule locus. The phosphoglucomutase (PGM) and Glc-1-P uridylyltransferase activities necessary for the first two steps are derived largely through the actions of cellular enzymes. Homologues of these enzymes, encoded by
cps3M
and
cps3U
in the type 3 locus, are not required for capsule production. Here, we show that
cps3M
and
cps3U
also are not required for mouse virulence. In contrast, nonencapsulated isolates containing defined mutations in
cps3D
and
cps3S
were avirulent, as were reduced-capsule isolates containing mutations in
pgm
. Insertion mutants that lacked PGM activity were avirulent in both immunologically normal (BALB/cByJ) and immunodeficient (CBA/N) mice. In contrast, a mutant (JY1060) with reduced PGM activity was avirulent in the former but had only modestly reduced virulence in the latter. The high virulence in CBA/N mice was not due to the lack of antibodies to phosphocholine but reflected a growth environment distinct from that found in BALB/cByJ mice. The reduced PGM activity of JY1060 resulted in enhanced binding of complement and antibodies to surface antigens. However, decomplementation of BALB/cByJ mice did not enhance the virulence of this mutant. Suppressor mutations, only some of which resulted in increased capsule production, increased the virulence of JY1060 in BALB/cByJ mice. The results suggest that PGM plays a critical role in pneumococcal virulence by affecting multiple cellular pathways.
PersistentChlamydia trachomatisInfections Resist Apoptotic Stimuli
Authors: Dean Deborah , Powers Virginia C. 
Published: July 2002

ABSTRACTMicrobial modulation of apoptosis has added a new dimension of understanding to the dynamic interaction between the human host and its microbial invaders. Persistent infection can be a by-product of inhibition of apoptosis and may significantly impact the pathogenesis of diseases caused by organisms such asChlamydia trachomatis. We compared apoptotic responses among HeLa 229 cells acutely and persistently infected and mock infected with serovar A/HAR-13. Persistence was induced by gamma interferon at 0.2 and 2.0 ng/ml. Cells were treated with etoposide or staurosporine at 24-h intervals and assayed for apoptosis by cell count, DNA ladder formation, and cytochromectranslocation. From the 24- to 120-h time points, infected cultures were 87 and 90% viable for etoposide and staurosporine treatment, respectively, and produced no DNA ladder, and cytochromecremained in the mitochondria. In contrast, mock-infected cells were 22 and 37% viable for etoposide (P= 0.0001) and staurosporine (P= 0.01), respectively, and displayed characteristic DNA ladders, and cytochromecwas translocated. We found that resistance to apoptotic stimuli was identical in acute and persistent infections. Since cytochromecwas not translocated from the mitochondrion, caspase-9 activity was likely not involved. The expression of chlamydial hsp60, a known stimulator of inflammation in vivo, was measured in both active and persistent infections by Western blot, with increased production in the latter with or without staurosporine treatment. Chlamydial disregulation of apoptosis and the ensuing persistence of organisms offer an alternative pathogenic mechanism for chlamydial scarring observed in trachoma and infertility populations via sustained inflammation induced by immunoreactive molecules such as hsp60.
Subinhibitory Clindamycin Differentially Inhibits Transcription of Exoprotein Genes in
Staphylococcus aureus
Authors: Herbert Silvia , Barry Peter , Novick Richard P. 
Published: July 2002

ABSTRACT

It has long been known that certain antibiotics, at subinhibitory concentrations, differentially inhibit the synthesis of α-hemolysin and other staphylococcal virulence factors. In this report, we show that subinhibitory clindamycin (SBCL) eliminates production of nearly all exoproteins by
Staphylococcus aureus
but has virtually no effect on cytoplasmic proteins. The effect was abolished by a gene conferring resistance to macrolides-lincosamides-streptogramin B, showing that differential inhibition of protein synthesis is responsible; remarkably, however, subinhibitory clindamycin blocked production of several of the individual exoprotein genes, including
spa
(encoding protein A),
hla
(encoding α-hemolysin), and
spr
(encoding serine protease), at the level of transcription, suggesting that the primary effect must be differential inhibition of the synthesis of one or more regulatory proteins. In contrast to earlier reports, however, we found that subinhibitory clindamycin stimulates synthesis of coagulase and fibronectin binding protein B, also at the level of transcription.
agr
and
sar
expression was minimally affected by subinhibitory clindamycin. These effects varied from strain to strain and do not seem to be responsible for the effects of subinhibitory clindamycin on the overall exoprotein pattern.
Directional Gene Movement from Human-Pathogenic to Commensal-Like Streptococci
Authors: Kalia Awdhesh , Enright Mark C. , Spratt Brian G. , Bessen Debra E. 
Published: July 2002

ABSTRACTGroup A streptococci (GAS) are highly pathogenic for humans, and their closest genetic relatives, group C and G streptococci (GCS and GGS, respectively), are generally regarded as commensals, although they can be found in association with human disease. As part of an effort to better understand the evolution of virulence, the phylogenetic relationships between GAS, GCS, and GGS were examined. The nucleotide sequence was determined for an internal portion of seven housekeeping (neutral) loci among >200 isolates of GAS and 34 isolates of GCS or GGS obtained from human subjects. Genotypic analysis failed to show support for the separation of GCS and GGS into two distinct populations. Unlike GAS, there was poor concordance betweenemmtype and genetic relatedness among GCS and GGS. All housekeeping genes within GAS displayed relatively low levels of sequence diversity. In contrast, individual GCS and GGS strains had mosaic genomes, containing alleles at some loci that were similar or identical to GAS alleles, whereas the alleles at other loci were about 10 to 30% diverged. The data provide evidence for a history of recent interspecies transfer of neutral genes that exhibits a strong net directionality from GAS donors to GCS and GGS recipients. A model for the evolution of GAS and of GCS and GGS is described.
Characterization of an Endoprotease (PrpL) Encoded by a PvdS-Regulated Gene inPseudomonas aeruginosa
Authors: Wilderman Paula J. , Vasil Adriana I. , Johnson Zaiga , Wilson Megan J. , Cunliffe Heather E. , Lamont Iain L. , Vasil Michael L. 
Published: July 2002

ABSTRACTThe expression of many virulence factors inPseudomonas aeruginosais dependent upon environmental conditions, including iron levels, oxygen, temperature, and osmolarity. The virulence ofP. aeruginosaPAO1 is influenced by the iron- and oxygen-regulated gene encoding the alternative sigma factor PvdS, which is regulated through the ferric uptake regulator (Fur). We observed that overexpression of PvdS in strain PAO1 and a ΔpvdS::Gmmutant resulted in increased pyoverdine production and proteolytic activity compared to when PvdS was not overexpressed. To identify additional PvdS-regulated genes, we compared extracellular protein profiles from PAO1 and the ΔpvdS::Gmmutant grown under iron-deficient conditions. A protein present in culture supernatants from PAO1 but not in supernatants from ΔpvdS::Gmwas investigated. Amino acid sequence analysis and examination of the genomic database of PAO1 revealed that the N terminus of this 27-kDa protein is identical to that of protease IV ofP. aeruginosastrain PA103-29 and is homologous to an endoprotease produced byLysobacter enzymogenes.In this study, the gene encoding an endoprotease was cloned from PAO1 and designatedprpL(PvdS-regulated endoprotease, lysyl class). All (n= 41) but one of the strains ofP. aeruginosa, including clinical and environmental isolates, examined carryprpL. Moreover, PrpL production among these strains was highly variable. Analysis of RNase protection assays identified the transcription initiation site ofprpLand confirmed that its transcription is iron dependent. In the ΔpvdS::Gmmutant, the level ofprpLtranscription was iron independent and decreased relative to the level in PAO1. Furthermore, transcription ofprpLwas independent of PtxR, a PvdS-regulated protein. Finally, PrpL cleaves casein, lactoferrin, transferrin, elastin, and decorin and contributes to PAO1's ability to persist in a rat chronic pulmonary infection model.
Development of a Competitive Index Assay To Evaluate the Virulence ofListeria monocytogenes actAMutants during Primary and Secondary Infection of Mice
Authors: Auerbuch Victoria , Lenz Laurel L. , Portnoy Daniel A. 
Published: July 2002

ABSTRACTWe developed a competitive index assay for murine listeriosis that tests the virulence ofListeria monocytogenesstrains in different organs and at various times postinoculation. Studies presented here demonstrate the reproducibility of this assay during primary and secondary infection of inbred and outbred mice. We verified the validity of this assay by performing competitive index analysis of a well-characterized strain ofL. monocytogeneslacking theactAgene. In addition, we found that whileL. monocytogenesstrains unable to recruit vasodilator-stimulated phosphoprotein (VASP) to their surface exhibit a 10-fold virulence attenuation in the livers of naive animals, they display a 50-fold survival defect in the liver during secondary listeriosis.
The Dot/Icm Type IV Secretion System of
Legionella pneumophila
Is Essential for the Induction of Apoptosis in Human Macrophages
Authors: Zink Steven D. , Pedersen Lisa , Cianciotto Nicholas P. , Abu Kwaik Yousef 
Published: July 2002

ABSTRACT

We have previously shown that
Legionella pneumophila
induces caspase 3-dependent apoptosis in mammalian cells during early stages of infection. In this report, we show that nine
L. pneumophila
strains with mutations in the
dotA
,
dotDCB
,
icmT
,
icmGCD,
and
icmJB
loci are completely defective in the induction of apoptosis, in addition to their severe defects in intracellular replication and pore formation-mediated cytotoxicity. Importantly, all nine
dot
/
icm
mutants were complemented for all their defective phenotypes with the respective wild-type loci. We show that the role of the Dot/Icm type IV secretion system in the induction of apoptosis is independent of the RtxA toxin, the
dot
/
icm
-regulated pore-forming toxin, and the type II secretion system. However, the pore-forming toxin, which is triggered upon entry into the postexponential growth phase, enhances the ability of
L. pneumophila
to induce apoptosis. Our data provide the first example of the role of a type IV secretion system of a bacterial pathogen in the induction of apoptosis in the host cell.
The
Neisseria
Lipooligosaccharide-Specific α-2,3-Sialyltransferase Is a Surface-Exposed Outer Membrane Protein
Authors: Shell Dawn M. , Chiles Lisa , Judd Ralph C. , Seal Samar , Rest Richard F. 
Published: July 2002

ABSTRACT

Neisseria gonorrhoeae
and
Neisseria meningitidis
express an ∼43-kDa α-2,3-sialyltransferase (Lst) that sialylates the surface lipooligosaccharide (LOS) by using exogenous (in all
N. gonorrhoeae
strains and some
N. meningitidis
serogroups) or endogenous (in other
N. meningitidis
serogroups) sources of 5′-cytidinemonophospho-
N
-acetylneuraminic acid (CMP-NANA). Sialylation of LOS can protect
N. gonorrhoeae
and
N. meningitidis
from complement-mediated serum killing and from phagocytic killing by neutrophils. The precise subcellular location of Lst has not been determined. We confirm and extend previous studies by demonstrating that Lst is located in the outer membrane and is surface exposed in both
N. gonorrhoeae
and
N. meningitidis
. Western immunoblot analysis of subcellular fractions of
N. gonorrhoeae
strain F62 and
N. meningitidis
strain MC58⊄3 (an acapsulate serogroup B strain) performed with rabbit antiserum raised against recombinant Lst revealed an ∼43-kDa protein exclusively in outer membrane preparations of both pathogens. Inner membrane, periplasmic, cytoplasmic, and culture supernatant fractions were devoid of Lst, as determined by Western blot analysis. Consistent with this finding, outer membrane fractions of
N. gonorrhoeae
were significantly enriched for sialyltransferase enzymatic activity. A trace of enzymatic activity was detected in inner membrane fractions, which may have represented Lst in transit to the outer membrane or may have represented inner membrane contamination of outer membrane preparations. Subcellular preparations of an isogenic
lst
insertion knockout mutant of
N. gonorrhoeae
F62 (strain ST01) expressed neither a 43-kDa immunoreactive protein nor sialyltransferase activity. Anti-Lst rabbit antiserum bound to whole cells of
N. meningitidis
MC58⊄3 and wild-type
N. gonorrhoeae
F62 but not to the Lst mutant ST01, indicating the surface exposure of the enzyme. Although the anti-Lst antiserum avidly bound enzymatically active, recombinant Lst, it inhibited Lst (sialyltransferase) activity by only about 50% at the highest concentration of antibody used. On the contrary, anti-Lst antiserum did not inhibit sialylation of whole
N. gonorrhoeae
cells in the presence of exogenous CMP-NANA, suggesting that the antibody did not bind to or could not access the enzyme active site on the surface of viable
Neisseria
cells. Taken together, these results indicate that Lst is an outer membrane, surface-exposed glycosyltransferase. To our knowledge, this is the first demonstration of the localization of a bacterial glycosyltransferase to the outer membrane of gram-negative bacteria.
The
rel
Gene Is Essential for In Vitro Growth of
Staphylococcus aureus
Authors: Gentry Daniel , Li Tong , Rosenberg Martin , McDevitt Damien 
Published: July 2002

ABSTRACT

The stringent response in
Staphylococcus aureus
is mediated by the nucleotide guanosine pentaphosphate, whose synthesis is catalyzed by the product of the
rel
gene. We report here that the
rel
gene is essential for the in vitro growth of
S. aureus
, distinguishing it from all other bacteria tested for this requirement.
glnE
Is an Essential Gene in
Mycobacterium tuberculosis
Authors: Parish Tanya , Stoker Neil G. 
Published: July 2002

ABSTRACT

Mycobacterium tuberculosis
possesses a homologue of
glnE
, potentially encoding a regulator of glutamine synthetase activity. We attempted to construct
glnE
-disrupted mutants using a two-step strategy, whereby a single-crossover strain was first isolated, followed by
sacB
counterselection to isolate the double-crossover strain. Of 192 sucrose-resistant colonies tested, none were mutants, although the wild-type double crossover could be easily isolated. When a second copy of the wild-type
glnE
was integrated into the chromosome, we could isolate both wild-type and mutant double-crossover strains. Thus, the chromosomal gene could only be replaced with a disrupted copy when another functional copy of the gene was provided, demonstrating that this gene is essential under the conditions tested.
New Virulence-Activated and Virulence-Repressed Genes Identified by Systematic Gene Inactivation and Generation of Transcriptional Fusions in
Bordetella pertussis
Authors: Antoine Rudy , Alonso Sylvie , Raze Dominique , Coutte Loïc , Lesjean Sarah , Willery Eve , Locht Camille , Jacob-Dubuisson Françoise 
Published: July 2002

ABSTRACT

An in silico scan of the partially completed genome sequence of
Bordetella pertussis
and analyses of transcriptional fusions generated with a new integrational vector were used to identify new potential virulence genes. The genes encoding a putative siderophore receptor, adhesins, and an autotransporter protein appeared to be regulated in a manner similar to
Bordetella
virulence genes by the global virulence regulator BvgAS. In contrast, the gene encoding a putative intimin-like protein appeared to be repressed under conditions of virulence.
Development and Dynamics of
Pseudomonas
sp. Biofilms
Authors: Tolker-Nielsen Tim , Brinch Ulla C. , Ragas Paula C. , Andersen Jens Bo , Jacobsen Carsten Suhr , Molin Søren 
Published: July 2002

ABSTRACT

Pseudomonas
sp. strain B13 and
Pseudomonas putida
OUS82 were genetically tagged with the green fluorescent protein and the
Discosoma
sp. red fluorescent protein, and the development and dynamics occurring in flow chamber-grown two-colored monospecies or mixed-species biofilms were investigated by the use of confocal scanning laser microscopy. Separate red or green fluorescent microcolonies were formed initially, suggesting that the initial small microcolonies were formed simply by growth of substratum attached cells and not by cell aggregation. Red fluorescent microcolonies containing a few green fluorescent cells and green fluorescent microcolonies containing a few red fluorescent cells were frequently observed in both monospecies and two-species biofilms, suggesting that the bacteria moved between the microcolonies. Rapid movement of
P. putida
OUS82 bacteria inside microcolonies was observed before a transition from compact microcolonies to loose irregularly shaped protruding structures occurred. Experiments involving a nonflagellated
P. putida
OUS82 mutant suggested that the movements between and inside microcolonies were flagellum driven. The results are discussed in relation to the prevailing hypothesis that biofilm bacteria are in a physiological state different from planktonic bacteria.