bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inhibition of Hydrophobic Protein-MediatedCandida albicansAttachment to Endothelial Cells during Physiologic Shear Flow
Authors: Glee Pati M. , Cutler Jim E. , Benson Evelyn E. , Bargatze Robert F. , Hazen Kevin C. 
Published: July 2002

ABSTRACTAdhesion interactions during hematogenous dissemination ofCandida albicanslikely involve a complex array of host and fungal factors. PossibleC. albicansfactors include changes in cell surface hydrophobicity and exposed antigens that have been shown in static adhesion assays to influence attachment events. We used a novel in vitro shear analysis system to investigate host-pathogen interactions and the role of fungal cell surface hydrophobicity in adhesion events with human endothelial cells under simulated physiologic shear. Endothelial monolayers were grown in capillary tubes and tested with and without interleukin-1β activation in buffered medium containing human serum. Hydrophobic and hydrophilic stationary-phaseC. albicansyeast cells were infused into the system under shear flow and found to adhere with widely varying efficiencies. The average number of adherent foci was determined from multiple fields, sampled via video microscopy, between 8 and 12 min after infusion. HydrophobicC. albicanscells demonstrated significantly more heterotypic binding events (Candida-endothelial cell) and greater homotypic binding events (Candida-Candida) than hydrophilic yeast cells. Cytokine activation of the endothelium significantly increased binding by hydrophobicC. albicanscompared to unactivated host cells. Preincubation of hydrophobic yeast cells with a monoclonal antibody against hydrophobic cell wall proteins significantly blocked adhesion interactions with the endothelial monolayers. Because the antibody also blocksC. albicansbinding to laminin and fibronectin, results suggest that vascular adhesion events with endothelial cells and exposed extracellular matrix may be blocked duringC. albicansdissemination. Future studies will address the protective efficacy of blocking or redirecting blood-borne fungal cells to favor host defense mechanisms.
In Vivo-Expressed Genes ofPasteurella multocida
Authors: Hunt Meredith L. , Boucher David J. , Boyce John D. , Adler Ben 
Published: July 2002

ABSTRACTPasteurella multocidais the causative agent of infectious diseases of economic importance such as fowl cholera, bovine hemorrhagic septicemia, and porcine atrophic rhinitis. However, knowledge of the molecular mechanisms and determinants thatP. multocidarequires for virulence and pathogenicity is still limited. To address this issue, we developed a genetic expression system, based on the in vivo expression technology approach first described by Mahan et al. (Science 259:686–688, 1993), to identify in vivo-expressed genes ofP. multocida. Numerous genes, such as those encoding outer membrane lipoproteins, metabolic and biosynthetic enzymes, and a number of hypothetical proteins, were identified. These may prove to be useful targets for attenuating mutation and/or warrant further investigation for their roles in immunity and/or pathogenesis.
Selection for Urease Activity during
Helicobacter pylori
Infection of Rhesus Macaques (
Macaca mulatta
)
Authors: Hansen Lori M. , Solnick Jay V. 
Published: July 2002

ABSTRACT

Helicobacter pylori
strain J166 recovered from experimentally inoculated rhesus monkeys had up to a 250-fold-increased urease activity over that before inoculation. This was found to result from the selection of urease positive J166 clones from a heterogenous inoculum, which was predominantly urease negative due to a 1-bp insertion in the
ureA
gene. These results confirm the importance of urease for
H. pylori
colonization. Strain J166 is particularly well adapted to the rhesus monkey, since it colonized preferentially despite the fact that less than 0.1% of the inoculum was urease positive.
Major Outer Membrane Protein Omp25 ofBrucella suisIs Involved in Inhibition of Tumor Necrosis Factor Alpha Production during Infection of Human Macrophages
Authors: Jubier-Maurin Véronique , Boigegrain Rose-Anne , Cloeckaert Axel , Gross Antoine , Alvarez-Martinez Maria-Teresa , Terraza Annie , Liautard Janny , Köhler Stephan , Rouot Bruno , Dornand Jacques , Liautard Jean Pierre 
Published: July 2002

ABSTRACTBrucellaspp. can establish themselves and cause disease in humans and animals. The mechanisms by whichBrucellaspp. evade the antibacterial defenses of their host, however, remain largely unknown. We have previously reported that live brucellae failed to induce tumor necrosis factor alpha (TNF-α) production upon human macrophage infection. This inhibition is associated with a nonidentified protein that is released into culture medium. Outer membrane proteins (OMPs) of gram-negative bacteria have been shown to modulate macrophage functions, including cytokine production. Thus, we have analyzed the effects of two major OMPs (Omp25 and Omp31) ofBrucella suis1330 (wild-type [WT]B. suis) on TNF-α production. For this purpose,omp25andomp31null mutants ofB. suis(Δomp25 B. suisand Δomp31 B. suis, respectively) were constructed and analyzed for the ability to activate human macrophages to secrete TNF-α. We showed that, in contrast to WTB. suisor Δomp31 B. suis, Δomp25 B. suisinduced TNF-α production when phagocytosed by human macrophages. The complementation of Δomp25 B. suiswith WTomp25(Δomp25-omp25 B. suismutant) significantly reversed this effect: Δomp25-omp25 B. suis-infected macrophages secreted significantly less TNF-α than did macrophages infected with the Δomp25 B. suismutant. Furthermore, pretreatment of WTB. suiswith an anti-Omp25 monoclonal antibody directed against an epitope exposed at the surface of the bacteria resulted in substancial TNF-α production during macrophage infection. These observations demonstrated that Omp25 ofB. suisis involved in the negative regulation of TNF-α production upon infection of human macrophages.
Identification and Characterization of a Novel Secreted Immunoglobulin Binding Protein from Group A Streptococcus
Authors: Fagan Peter K. , Reinscheid Dieter , Gottschalk Birgit , Chhatwal Gursharan S. 
Published: July 2002

ABSTRACTImmunoglobulin binding proteins are one of several pathogenicity factors which have been associated with invasive disease caused by group A streptococci. The surface-bound M and M-like proteins ofStreptococcus pyogenesare the most characterized of these immunoglobulin binding proteins, and in most cases they bind only a single antibody class. Here we report the identification of a novel non-M-type secreted protein, designated SibA (for secreted immunoglobulin binding protein from group A streptococcus), which binds all immunoglobulin G (IgG) subclasses, the Fc and Fab fragments, and also IgA and IgM. SibA has no significant sequence homology to any M-related proteins, is not found in thevirregulon, and contains none of the characteristic M-protein regions, such as the A or C repeats. Like M proteins, however, SibA does have relatively high levels of alanine, lysine, glutamic acid, leucine, and glycine. SibA and M proteins also share an alpha-helical N-terminal secondary structure which has been previously implicated in immunoglobulin binding in M proteins. Evidence presented here indicates that this is also the case for SibA. SibA also has regions of local similarity with other coiled-coil proteins such asListeria monocytogenesP45 autolysin, human myosin heavy chain, macrogolgin, andSchistoma mansoniparamyosin, some of which are of potential significance since cross-reactive antibodies between myosin proteins and M proteins have been implicated in the development of the autoimmune sequelae of streptococcal disease.
Role of Bcl-2 Family Members in Caspase-Independent Apoptosis duringChlamydiaInfection
Authors: Perfettini Jean-Luc , Reed John C. , Israël Nicole , Martinou Jean-Claude , Dautry-Varsat Alice , Ojcius David M. 
Published: July 2002

ABSTRACTInfection with an obligate intracellular bacterium, theChlamydia trachomatislymphogranuloma venereum (LGV/L2) strain or the guinea pig inclusion conjunctivitis serovar ofChlamydia psittaci, leads to apoptosis of host cells. The apoptosis is not affected by a broad-spectrum caspase inhibitor, and caspase-3 is not activated in infected cells, suggesting that apoptosis mediated by these two strains ofChlamydiais independent of known caspases. Overexpression of the proapoptotic Bcl-2 family member, Bax, was previously shown to induce caspase-independent apoptosis, and we find that Bax is activated and translocates from the cytosol to the mitochondria inC. psittaci-infected cells.C. psittaci-induced apoptosis is inhibited in host cells overexpressing Bax inhibitor-1 and is inhibited through overexpression of Bcl-2, which blocks both caspase-dependent and -independent apoptosis. As Bax and mitochondria are ideally located to sense stress-related metabolic changes emanating from the interior of an infected cell, it is likely that Bax-dependent apoptosis may also be observed in cells infected with other intracellular pathogens.
Physical Mapping of
bchG
,
orf427
, and
orf177
in the Photosynthesis Gene Cluster of
Rhodobacter sphaeroides
: Functional Assignment of the Bacteriochlorophyll Synthetase Gene
Authors: Addlesee Hugh A. , Fiedor Leszek , Hunter C. Neil 
Published: July 2002

ABSTRACT

The purple photosynthetic bacterium
Rhodobacter sphaeroides
has within its genome a cluster of photosynthesis-related genes approximately 41 kb in length. In an attempt to identify genes involved in the terminal esterification stage of bacteriochlorophyll biosynthesis, a previously uncharacterized 5-kb region of this cluster was sequenced. Four open reading frames (ORFs) were identified, and each was analyzed by transposon mutagenesis. The product of one of these ORFs,
bchG
, shows close homologies with (bacterio)chlorophyll synthetases, and mutants in this gene were found to accumulate bacteriopheophorbide, the metal-free derivative of the bacteriochlorophyll precursor bacteriochlorophyllide, suggesting that
bchG
is responsible for the esterification of bacteriochlorophyllide with an alcohol moiety. This assignment of function to
bchG
was verified by the performance of assays demonstrating the ability of BchG protein, heterologously synthesized in
Escherichia coli
, to esterify bacteriochlorophyllide with geranylgeranyl pyrophosphate in vitro, thereby generating bacteriochlorophyll. This step is pivotal to the assembly of a functional photosystem in
R. sphaeroides
, a model organism for the study of structure-function relationships in photosynthesis. A second gene,
orf177
, is a member of a large family of isopentenyl diphosphate isomerases, while sequence homologies suggest that a third gene,
orf427
, may encode an assembly factor for photosynthetic complexes. The function of the remaining ORF,
bchP
, is the subject of a separate paper (H. Addlesee and C. N. Hunter, J. Bacteriol. 181:7248–7255, 1999). An operonal arrangement of the genes is proposed.
Genetic and Phenotypic Analyses of the
rdx
Locus of
Rhodobacter sphaeroides
2.4.1
Authors: Roh Jung Hyeob , Kaplan Samuel 
Published: July 2002

ABSTRACT

Previously, we reported that
rdxB
, encoding a likely membrane-bound two [4Fe-4S]-containing center, is involved in the aerobic regulation of photosystem gene expression in
Rhodobacter sphaeroides
2.4.1. To further investigate the role of
rdxB
as well as other genes of the
rdxBHIS
operon on photosystem gene expression, we constructed a series of nonpolar, in-frame deletion mutations in each of the
rdx
genes. Using both
puc
and
puf
operon
lacZ
fusions to monitor photosystem gene expression, under aerobic conditions, in each of the mutant strains revealed significant increased photosynthesis gene expression. In the case of mutations in either
rdxH
,
rdxI
, or
rdxS
, the aerobic induction of photosystem gene expression is believed to be indirect by virtue of a posttranscriptional effect on
cbb
3
cytochrome oxidase structure and integrity. For RdxB, we suggest that this redox protein has a more direct effect on photosystem gene expression by virtue of its interaction with the
cbb
3
oxidase. An associated phenotype, involving the enhanced conversion of the carotenoid spheroidene to spheroidenone, is also observed in the RdxB, -H, -I, and -S mutant strains. This phenotype is also suggested to be the result of the role of the
rdxBHIS
locus in
cbb
3
oxidase activity and/or structure. RdxI is suggested to be a new class of metal transporter of the CPx-type ATPases.
Genetic and Environmental Factors Affecting T-Pilin Export and T-Pilus Biogenesis in Relation to Flagellation of
Agrobacterium tumefaciens
Authors: Lai Erh-Min , Chesnokova Olga , Banta Lois M. , Kado Clarence I. 
Published: July 2002

ABSTRACT

The T pilus, primarily composed of cyclic T-pilin subunits, is essential for the transmission of the Ti-plasmid T-DNA from
Agrobacterium tumefaciens
to plant cells. Although the
virB2
gene of the 11-gene
virB
operon was previously demonstrated to encode the full-length propilin, and other genes of this operon have been implicated as members of a conserved transmembrane transport apparatus, the role of each
virB
gene in T-pilin synthesis and transport and T-pilus biogenesis remained undefined. In the present study, each
virB
gene was examined and was found to be unessential for T-pilin biosynthesis, except
virB2
, but was determined to be essential for the export of the T-pilin subunits and for T-pilus formation. We also find that the genes of the
virD
operon are neither involved in T-pilin export nor T-pilus formation. Critical analysis of three different
virD4
mutants also showed that they are not involved in T-pilus biogenesis irrespective of the
A. tumefaciens
strains used. With respect to the environmental effects on T-pilus biogenesis, we find that T pili are produced both on agar and in liquid culture and are produced at one end of the
A. tumefaciens
rod-shaped cell in a polar manner. We also report a novel phenomenon whereby flagellum production is shut down under conditions which turn on T-pilus formation. These conditions are the usual induction with acetosyringone at pH 5.5 of Ti-plasmid
vir
genes. A search of the
vir
genes involved in controlling this biphasic reaction in induced
A. tumefaciens
cells revealed that
virA
on the Ti plasmid is involved and that neither
virB
nor
virD
genes are needed for this reaction. The biphasic reaction therefore appears to be mediated through a two-component signal transducing system likely involving an unidentified
vir
gene in
A. tumefaciens
.
Regulation of the
furA
and
catC
Operon, Encoding a Ferric Uptake Regulator Homologue and Catalase-Peroxidase, Respectively, in
Streptomyces coelicolor
A3(2)
Authors: Hahn Ji-Sook , Oh So-Young , Roe Jung-Hye 
Published: July 2002

ABSTRACT

We isolated the
catC
gene, encoding catalase-peroxidase in
Streptomyces coelicolor
, using sequence homology with the
katG
gene from
Escherichia coli
. Upstream of the
catC
gene, an open reading frame (
furA
) encoding a homologue of ferric uptake regulator (Fur) was identified. S1 mapping analysis indicated that the
furA
gene was cotranscribed with the
catC
gene. The transcriptional start site of the
furA-catC
mRNA was mapped to the translation start codon ATG of the
furA
gene. The putative promoter contains consensus −10 and −35 elements similar to those recognized by ς
HrdB
, the major sigma factor of
S. coelicolor
. The transcripts were produced maximally at late-exponential phase and decreased at the stationary phase in liquid culture. The change in the amount of mRNA was consistent with that of CatC protein and enzyme activity. When the
furA
gene was introduced into
S. lividans
on a multicopy plasmid, the increased production of
catC
transcripts and protein product at late growth phase was inhibited, implying a role for FurA as the negative regulator of the
furA-catC
operon. FurA protein bound to its own promoter region between −59 and −39 nucleotides from the transcription start site. The binding affinity of FurA increased under reducing conditions and in the presence of metals such as Ni
2+
, Mn
2+
, Zn
2+
, or Fe
2+
. Addition of these metals to the growth medium decreased the production of CatC protein, consistent with the role of FurA as a metal-dependent repressor.
ς
54
Promoters Control Expression of Genes Encoding the Hook and Basal Body Complex in
Rhodobacter sphaeroides
Authors: Poggio Sebastian , Aguilar Carlos , Osorio Aurora , González-Pedrajo Bertha , Dreyfus Georges , Camarena Laura 
Published: July 2002

ABSTRACT

Gene expression of the flagellar system is tightly controlled by external stimuli or intracellular signals. A general picture of this regulation has been obtained from studies of
Salmonella enterica
serovar Typhimurium. However, these regulatory mechanisms do not apply to all bacterial groups. In this study, we have investigated regulation of the flagellar genetic system in
Rhodobacter sphaeroides
. Deletion analysis, site-directed mutagenesis, and 5′-end mapping were conducted in order to identify the
fliO
promoter. Our results indicate that this promoter is recognized by the factor ς
54
. Additionally, 5′-end mapping of the
flgB
and
fliK
transcripts suggests that these mRNAs are also transcribed from ς
54
promoters. Finally, we showed evidence that suggests that
fliC
transcription is not entirely dependent on the presence of a complete basal body-hook structure. Our results are discussed in the context of a possible regulatory hierarchy controlling flagellar gene expression in
R. sphaeroides
.
Myxococcus xanthus dif
Genes Are Required for Biogenesis of Cell Surface Fibrils Essential for Social Gliding Motility
Authors: Yang Zhaomin , Ma Xiaoyuan , Tong Leming , Kaplan Heidi B. , Shimkets Lawrence J. , Shi Wenyuan 
Published: July 2002

ABSTRACT

Myxococcus xanthus
social (S) gliding motility has been previously reported by us to require the chemotaxis homologues encoded by the
dif
genes. In addition, two cell surface structures, type IV pili and extracellular matrix fibrils, are also critical to
M. xanthus
S motility. We have demonstrated here that
M. xanthus dif
genes are required for the biogenesis of fibrils but not for that of type IV pili. Furthermore, the developmental defects of
dif
mutants can be partially rescued by the addition of isolated fibril materials. Along with the chemotaxis genes of various swarming bacteria and the
pilGHIJ
genes of the twitching bacterium
Pseudomonas aeruginosa
, the
M. xanthus dif
genes belong to a unique class of bacterial chemotaxis genes or homologues implicated in the biogenesis of structures required for bacterial surface locomotion. Genetic studies indicate that the
dif
genes are linked to the
M. xanthus dsp
region, a locus known to be crucial for
M. xanthus
fibril biogenesis and S gliding.
The UspA1 Protein and a Second Type of UspA2 Protein Mediate Adherence of
Moraxella catarrhalis
to Human Epithelial Cells In Vitro
Authors: Lafontaine Eric R. , Cope Leslie D. , Aebi Christoph , Latimer Jo L. , McCracken George H. , Hansen Eric J. 
Published: July 2002

ABSTRACT

The UspA1 and UspA2 proteins of
Moraxella catarrhalis
are structurally related, are exposed on the bacterial cell surface, and migrate as very high-molecular-weight complexes in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Previous analysis of
uspA1
and
uspA2
mutants of
M. catarrhalis
strain 035E indicated that UspA1 was involved in adherence of this organism to Chang conjunctival epithelial cells in vitro and that expression of UspA2 was essential for resistance of this strain to killing by normal human serum (C. Aebi, E. R. Lafontaine, L. D. Cope, J. L. Latimer, S. R. Lumbley, G. H. McCracken, Jr., and E. J. Hansen, Infect. Immun. 66:3113–3119, 1998). In the present study, isogenic
uspA1
,
uspA2
, and
uspA1 uspA2
mutations were constructed in three additional
M. catarrhalis
strains: 012E, TTA37, and 046E. The
uspA1
mutant of strain 012E had a decreased ability to attach to Chang cells. However, inactivation of the
uspA1
gene in both strain TTA37 and strain 046E did not cause a significant decrease in attachment ability. Inactivation of the
uspA2
gene of strain TTA37 did result in a loss of attachment ability. Nucleotide sequence analysis revealed that the predicted protein encoded by the
uspA2
genes of both strains TTA37 and 046E had a N-terminal half that resembled the N-terminal half of UspA1 proteins, whereas the C-terminal half of this protein was nearly identical to those of previously characterized UspA2 proteins. The gene encoding this “hybrid” protein was designated
uspA2H
. PCR-based analysis revealed that approximately 20% of
M. catarrhalis
strains apparently possess a
uspA2H
gene instead of a
uspA2
gene. The
M. catarrhalis uspA1
,
uspA2
, and
uspA2H
genes were cloned and expressed in
Haemophilus influenzae
cells, which were used to prove that both the UspA1 and UspA2H proteins can function as adhesins in vitro.
Cpx Two-Component Signal Transduction in
Escherichia coli
: Excessive CpxR-P Levels Underlie CpxA* Phenotypes
Authors: De Wulf Peter , Lin E. C. C. 
Published: July 2002

ABSTRACT

In
Escherichia coli
, the CpxA-CpxR two-component signal transduction system and the ς
E
and ς
32
response pathways jointly regulate gene expression in adaptation to adverse conditions. These include envelope protein distress, heat shock, oxidative stress, high pH, and entry into stationary phase. Certain mutant versions of the CpxA sensor protein (CpxA* proteins) exhibit an elevated ratio of kinase to phosphatase activity on CpxR, the cognate response regulator. As a result, CpxA* strains display numerous phenotypes, many of which cannot be easily related to currently known functions of the CpxA-CpxR pathway. It is unclear whether CpxA* phenotypes are caused solely by hyperphosphorylation of CpxR. We here report that all of the tested CpxA* phenotypes depend on elevated levels of CpxR-P and not on cross-signalling of CpxA* to noncognate response regulators.
Morphogenetic Proteins SpoVID and SafA Form a Complex during Assembly of the
Bacillus subtilis
Spore Coat
Authors: Ozin Amanda J. , Henriques Adriano O. , Yi Hong , Moran Charles P. 
Published: July 2002

ABSTRACT

During endospore formation in
Bacillus subtilis
, over two dozen polypeptides are assembled into a multilayered structure known as the spore coat, which protects the cortex peptidoglycan (PG) and permits efficient germination. In the initial stages of coat assembly a protein known as CotE forms a ring around the forespore. A second morphogenetic protein, SpoVID, is required for maintenance of the CotE ring during the later stages, when most of proteins are assembled into the coat. Here, we report on a protein that appears to associate with SpoVID during the early stage of coat assembly. This protein, which we call SafA for SpoVID-associated factor A, is encoded by a locus previously known as
yrbA
. We confirmed the results of a previous study that showed
safA
mutant spores have defective coats which are missing several proteins. We have extended these studies with the finding that SafA and SpoVID were coimmunoprecipitated by anti-SafA or anti-SpoVID antiserum from whole-cell extracts 3 and 4 h after the onset of sporulation. Therefore, SafA may associate with SpoVID during the early stage of coat assembly. We used immunogold electron microscopy to localize SafA and found it in the cortex, near the interface with the coat in mature spores. SafA appears to have a modular design. The C-terminal region of SafA is similar to those of several inner spore coat proteins. The N-terminal region contains a sequence that is conserved among proteins that associate with the cell wall. This motif in the N-terminal region may target SafA to the PG-containing regions of the developing spore.