bluuebunny/crossref_metadata_2025_split huggingface dataset:
rpoS
Gene Function Is a Disadvantage for
Escherichia coli
BJ4 during Competitive Colonization of the Mouse Large Intestine
Authors: Krogfelt Karen A. , Hjulgaard Marianne , Sørensen Kristine , Cohen Paul S. , Givskov Michael 
Published: July 2002

ABSTRACT

The ability of
Escherichia coli
to survive stress during growth in different environments is, in large part, dependent on
rpoS
and the genes that comprise the
rpoS
regulon.
E. coli
BJ4 and an isogenic BJ4
rpoS
mutant were used to examine the influence of the
rpoS
gene on
E. coli
colonization of the streptomycin-treated mouse large intestine. Colonization experiments in which the wild-type
E. coli
BJ4 and its
rpoS
mutant were fed individually as well as simultaneously to mice suggested that
E. coli
BJ4 does not face prolonged periods of nutrient starvation in the mouse large intestine and that the
rpoS
regulon is not expressed during long-term colonization after adaptation of the bacteria to the gut environment.
The Lipopolysaccharide Structures ofSalmonella entericaSerovar Typhimurium andNeisseria gonorrhoeaeDetermine the Attachment of Human Mannose-Binding Lectin to Intact Organisms
Authors: Devyatyarova-Johnson Marina , Rees Ian H. , Robertson Brian D. , Turner Malcolm W. , Klein Nigel J. , Jack Dominic L. 
Published: July 2002

ABSTRACTMannose-binding lectin (MBL) is an important component of the innate immune system. It binds to the arrays of sugars commonly presented by microorganisms and activates the complement system independently of antibody. Despite detailed knowledge of the stereochemical basis of MBL binding, relatively little is known about how bacterial surface structures influence binding of the lectin. Using flow cytometry, we have measured the binding of MBL to a range of mutants ofSalmonella entericaserovar Typhimurium andNeisseria gonorrhoeaewhich differ in the structure of expressed lipopolysaccharide (LPS). For both organisms, the possession of core LPS structures led to avid binding of MBL, which was abrogated by the addition of O antigen (Salmonellaserovar Typhimurium) or sialic acid (N. gonorrhoeae). Truncation of the LPS within the core led to lower levels of MBL binding. It was not possible to predict the magnitude of MBL binding from the identity of the LPS terminal sugar alone, indicating that the three-dimensional disposition of LPS molecules is probably also of importance in determining MBL attachment. These results further support the hypothesis that LPS structure is a major determinant of MBL binding.
The Most Abundant Glycoprotein of Amebic Cyst Walls (Jacob) Is a Lectin with Five Cys-Rich, Chitin-Binding Domains
Authors: Frisardi Marta , Ghosh Sudip K. , Field Jessica , Van Dellen Katrina , Rogers Rick , Robbins Phillips , Samuelson John 
Published: July 2002

ABSTRACT

The infectious stage of amebae is the chitin-walled cyst, which is resistant to stomach acids. In this study an extraordinarily abundant, encystation-specific glycoprotein (Jacob) was identified on two-dimensional protein gels of cyst walls purified from
Entamoeba invadens
. Jacob, which was acidic and had an apparent molecular mass of ∼100 kDa, contained sugars that bound to concanavalin A and ricin. The
jacob
gene encoded a 45-kDa protein with a ladder-like series of five Cys-rich domains. These Cys-rich domains were reminiscent of but not homologous to the Cys-rich chitin-binding domains of insect chitinases and peritrophic matrix proteins that surround the food bolus in the insect gut. Jacob bound purified chitin and chitin remaining in sodium dodecyl sulfate-treated cyst walls. Conversely, the
E. histolytica
plasma membrane Gal/GalNAc lectin bound sugars of intact cyst walls and purified Jacob. In the presence of galactose,
E. invadens
formed wall-less cysts, which were quadranucleate and contained Jacob and chitinase (another encystation-specific protein) in secretory vesicles. A galactose lectin was found to be present on the surface of wall-less cysts, which phagocytosed bacteria and mucin-coated beads. These results suggest that the
E. invadens
cyst wall forms when the plasma membrane galactose lectin binds sugars on Jacob, which in turn binds chitin via its five chitin-binding domains.
Adherence ofStaphylococcus aureusto Endothelial Cells: Influence of Capsular Polysaccharide, Global Regulatoragr, and Bacterial Growth Phase
Authors: Pöhlmann-Dietze Petra , Ulrich Martina , Kiser Kevin B. , Döring Gerd , Lee Jean C. , Fournier Jean-Michel , Botzenhart Konrad , Wolz Christiane 
Published: July 2002

ABSTRACTThe adherence ofStaphylococcus aureusto human endothelial cells (EC) is probably an important step in the pathogenesis of systemic staphylococcal infections. We examined the influence of type 5 capsular polysaccharide (CP5) production, the global regulatoragr, and the bacterial growth phase onS. aureusadherence to EC. WhereasS. aureusNewman showed maximal adherence to EC in the logarithmic phase of growth, an isogenicagrmutant showed maximal adherence in the stationary growth phase.S. aureusadherence to EC and CP5 expression were negatively correlated: a mutation in theagrlocus diminished CP5 production and led to increased adherence. Likewise, induction of CP5 expression by addition of NaCl to the growth medium resulted in reduced staphylococcal adherence to EC.S. aureusNewman cells that adhered to EC did not express CP5. A Newmancap5Omutant was acapsular and showed significantly greater adherence to EC than the parental strain did (P< 0.005). Complementation of thecap5Omutation intransrestored CP5 expression and reduced EC adherence to a level similar to that of the parental strain. The enhanced adherence shown by thecap5Omutant was similar in magnitude to that of theagrmutant or thecap5O agrdouble mutant. Cells of thecap5Omutant andcap5O agrdouble mutant harvested from stationary-phase cultures adhered significantly better than did cells harvested in the exponential growth phase. These data are consistent with the postexponential andagr-independent expression byS. aureusof at least one putative EC adhesin, whose binding domain may be masked by CP5.
T-Cell-Independent Responses toBorrelia burgdorferiAre Critical for Protective Immunity and Resolution of Lyme Disease
Authors: McKisic Maureen D. , Barthold Stephen W. 
Published: July 2002

ABSTRACTThe humoral immune response toBorrelia burgdorferiduring persistent infection is critical to both protective and disease-resolving immunity. This study examined the role of B cells in the absence of T cells during these events, using mice with selected immune dysfunctions. At 6 weeks postinfection, an interval at which arthritis resolves in immunocompetent mice, arthritis severity was equivalent among immunocompetent mice, αβ+-T-cell-deficient mice, and mice lacking both αβ+and γδ+T cells. Arthritis severity was worse in SCID mice, which lack T and B lymphocytes. Carditis regressed in immunocompetent mice and those lacking both αβ+and γδ+T cells but remained active in mice lacking only αβ+T cells and in SCID mice. Mice lacking only αβ+T cells and those lacking both αβ+and γδ+T cells generated immunoglobulin M (IgM) and IgG3B. burgdorferi-reactive antibodies. Sera from infected immunocompetent mice, mice lacking only αβ+T cells, and mice lacking both αβ+and γδ+T cells passively protected naive mice against challenge inoculation withB. burgdorferi. However, only sera from infected immunocompetent mice, but not sera from infected T-cell-deficient mice, were able to resolve arthritis when passively transferred to actively infected SCID mice. These data demonstrate that B-cell activation during a T-cell-independent response may be critical for resolution of arthritis and carditis and that protective antibodies are generated during this response.
Identification of a New Iron-Regulated Virulence Gene,
ireA
, in an Extraintestinal Pathogenic Isolate of
Escherichia coli
Authors: Russo Thomas A. , Carlino Ulrike B. , Johnson James R. 
Published: July 2002

ABSTRACT

Our laboratory is studying an extraintestinal pathogenic isolate of
Escherichia coli
(CP9) as a model pathogen. We have been using human urine, ascites, and blood ex vivo to identify genes with increased expression in these media relative to expression in Luria-Bertani (LB) broth. Such genes may represent new or unrecognized virulence traits. In this study, we report the identification of a new gene,
ireA
(iron-responsive element). This gene has an open reading frame of 2,049 nucleotides, and its peptide has a molecular mass of 75.3 kDa on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Its expression is increased a mean of 3.6-fold in human urine, 16.2-fold in human ascites, and 6.6-fold in human blood relative to expression in LB medium, and it is Fe repressible. IreA also exhibits peptide similarities (48 to 56%) to previously identified proteins that function as siderophore receptors, suggesting that IreA is involved in iron acquisition. PCR-based analysis of
ireA
's phylogenetic distribution detected
ireA
in none (0%) of 14 fecal isolates that represented probable commensal strains, but in 13 (26%) of 50 random urine and blood clinical isolates (
P
= 0.05) and in 5 (100%) of 5 representatives of the J96-like, clonal group of which CP9 is a member (
P
< 0.001). In a mouse urinary tract infection model, the presence of
ireA
contributed significantly to CP9's ability to colonize the bladder (
P
< 0.02), evidence that IreA is a urovirulence factor. Taken together, these findings demonstrate that
ireA
encodes a new virulence factor, which is likely involved in Fe acquisition.
Neospora caninum
Microneme Protein NcMIC3: Secretion, Subcellular Localization, and Functional Involvement in Host Cell Interaction
Authors: Naguleswaran Arunasalam , Cannas Angela , Keller Nadine , Vonlaufen Nathalie , Schares Gereon , Conraths Franz J. , Björkman Camilla , Hemphill Andrew 
Published: July 2002

ABSTRACT

In apicomplexan parasites, host cell adhesion and subsequent invasion involve the sequential release of molecules originating from secretory organelles named micronemes, rhoptries, and dense granules. Microneme proteins have been shown to be released at the onset of the initial contact between the parasite and the host cell and thus mediate and establish the physical interaction between the parasite and the host cell surface. This interaction most likely involves adhesive domains found within the polypeptide sequences of most microneme proteins identified to date. NcMIC3 is a microneme-associated protein found in
Neospora caninum
tachyzoites and bradyzoites, and a large portion of this protein is comprised of a stretch of four consecutive epidermal growth factor (EGF)-like domains. We determined the subcellular localization of NcMIC3 prior to and following host cell invasion and found that NcMIC3 was secreted onto the tachyzoite surface immediately following host cell lysis in a temperature-dependent manner. Surface-exposed NcMIC3 could be detected up to 2 to 3 h following host cell invasion, and at later time points the distribution of the protein was again restricted to the micronemes. In vitro secretion assays using purified tachyzoites showed that following secretion onto the surface, NcMIC3 was largely translocated towards the posterior end of the parasite, employing a mechanism which requires a functional actin microfilament system. Following this, the protein remained bound to the parasite surface, since it could not be detected in a soluble form in respective culture supernatants. Secretion of NcMIC3 onto the surface resulted in an outward exposure of the EGF-like domains and coincided with an increased capacity of
N. caninum
tachyzoites to adhere to Vero cell monolayers in vitro, a capacity which could be inhibited by addition of antibodies directed against the EGF-like domains. NcMIC3 is a prominent component of Triton X-100 lysates of tachyzoites, and cosedimentation assays employing prefixed Vero cells showed that the protein binds to the Vero cell surface. In addition, the EGF-like domains, expressed as recombinant proteins in
Escherichia coli
, also interacted with the Vero cell surface, while binding of NcSRS2 and NcSAG1, the major immunodominant surface antigens, was not as efficient. Our data are indicative of a functional role of NcMIC3 in host cell infection.
Infection withMycobacterium aviumDifferentially Regulates the Expression of Iron Transport Protein mRNA in Murine Peritoneal Macrophages
Authors: Zhong Wangjian , Lafuse William P. , Zwilling Bruce S. 
Published: July 2002

ABSTRACTIron is an important element for the growth of microorganisms as well as in the defense of the host by serving as a catalyst for the generation of free radicals via the Fenton/Haber-Weiss reactions. The iron transporter natural resistance-associated macrophage protein 1 (Nramp1) confers resistance to the growth of a variety of intracellular pathogens includingMycobacterium avium. Recently several other proteins that are involved in iron transport, including the highly homologous iron transporter Nramp2 and the transferrin receptor-associated protein HFE (hereditary hemochromatosis protein), have been described. The relationship of these proteins to host defense and to the growth of intracellular pathogens is not known. Here, we report that infection withM. aviumdifferentially regulates mRNA expression of the proteins associated with iron transport in murine peritoneal macrophages. Both Nramp1 and Nramp2 mRNA levels increase following infection, while the expression of transferrin receptor mRNA decreases. The level of expression of HFE mRNA remains unchanged. The difference in the expression of the mRNA of these proteins following infection or cytokine stimulation suggests that they may play an important role in host defense by maintaining a delicate balance between iron availability for host defense and at the same time limiting iron availability for microbial growth.
Identification and Characterization of the Hemophore-Dependent Heme Acquisition System of
Yersinia pestis
Authors: Rossi Maria-Silvia , Fetherston Jacqueline D. , Létoffé Sylvie , Carniel Elisabeth , Perry Robert D. , Ghigo Jean-Marc 
Published: July 2002

ABSTRACT

Yersinia pestis
possesses a heme-protein acquisition system (Hmu) that allows it to utilize heme and heme-protein complexes as the sole sources of iron. Analysis of the
Y. pestis
CO92 genomic sequence revealed a second heme-protein acquisition gene cluster that shares homology with the hemophore-dependent heme acquisition system (Has system) of
Serratia marcescens
. This locus consisted of the
hasR

yp

receptor gene, the
hasA

yp

hemophore gene, and genes encoding components of the HasA
yp
dedicated ABC transporter factor (
hasDE

yp

), as well as a
tonB
homologue (
hasB
yp
). By using a reconstituted secretion system in
Escherichia coli
, we showed that HasA
yp
is a secreted heme-binding protein and that expression of HasA
yp
is iron regulated in
E. coli
. The use of a transcriptional reporter fusion showed that the
hasRADEB
promoter is Fur regulated and has increased activity at 37°C. Hemoglobin utilization via the Has
yp
system was studied with both
E. coli
and
Y. pestis
, for which
has
and
has hmu
mutant strains were used. No contribution of the Has system to heme utilization was observed in either
E. coli
or
Y. pestis
under the conditions we tested. Previously it was shown that a deletion of the Hmu system had no effect on the virulence of
Y. pestis
in a mouse model of bubonic plague. An Hmu
−
Has
−
double mutant also retained full virulence in this model of infection. This report constitutes the first attempt to investigate the contribution of the hemophore-dependent heme acquisition system in bacterial pathogenicity.
Analysis ofBorrelia burgdorferivlsEGene Expression and Recombination in the Tick Vector
Authors: Indest Karl J. , Howell Jerrilyn K. , Jacobs Mary B. , Scholl-Meeker Dorothy , Norris Steven J. , Philipp Mario T. 
Published: July 2002

ABSTRACTExpression and recombination of the antigenic variationvlsEgene of the Lyme disease spirocheteBorrelia burgdorferiwere analyzed in the tick vector. To assessvlsEexpression,Ixodes scapularisnymphs infected with theB. burgdorferistrain B31 were fed on mice for 48 or 96 h or to repletion and then crushed and acetone fixed either immediately thereafter (ticks collected at the two earlier time points) or 4 days after repletion. Unfed nymphs also were examined. At all of the time points investigated, spirochetes were able to bind a rabbit antibody raised against the conserved invariable region 6 of VlsE, as assessed by indirect immunofluorescence, but not preimmune serum from the same rabbit. This same antibody also bound to B31 spirochetes cultivated in vitro. Intensity of fluorescence appeared highest in cultured spirochetes, followed by spirochetes present in unfed ticks. Only a dim fluorescent signal was observed on spirochetes at the 48 and 96 h time points and at day 4 postrepletion. Expression ofvlsEin vitro was affected by a rise in pH from 7.0 to 8.0 at 34°C. Hence,vlsEexpression appears to be sensitive to environmental cues of the type found in theB. burgdorferinatural history. To assessvlsErecombination, nymphs were capillary fed theB. burgdorferiB31 clonal isolate 5A3. Ticks thus infected were either left to rest for 4 weeks (Group I) or fed to repletion on a mouse (Group II). The contents of each tick from both groups were cultured and 10B. burgdorfericlones from the spirochetal isolate of each tick were obtained. ThevlsEcassettes from several of these clones were amplified by PCR and sequenced. Regardless of whether the isolate was derived from Group I or Group II ticks, no changes were observed in thevlsEsequence. In contrast,vlsEcassettes amplified fromB. burgdorfericlones derived from a mouse that was infected with B31-5A3 capillary-fed nymphs showed considerable recombination. It follows thatvlsErecombination does not occur in the tick vector.
Human Macrophage Gamma Interferon Decreases Gene Expression but Not Replication ofMycobacterium tuberculosis: Analysis of the Host-Pathogen Reciprocal Influence on Transcription in a Comparison of Strains H37Rv and CMT97
Authors: Cappelli Giulia , Volpe Pietro , Sanduzzi Alessandro , Sacchi Alessandra , Colizzi Vittorio , Mariani Francesca 
Published: July 2002

ABSTRACTMycobacterium tuberculosisis an intracellular pathogen that readily survives and replicates in human macrophages (MΦ). Host cells have developed different mycobactericidal mechanisms, including the production of inflammatory cytokines. The aim of this study was to compare the MΦ response, in terms of cytokine gene expression, to infection with theM. tuberculosislaboratory strain H37Rv and the clinicalM. tuberculosisisolate CMT97. Both strains induce the production of interleukin-12 (IL-12) and IL-16 at comparable levels. However, the clinical isolate induces a significantly higher and more prolonged MΦ activation, as shown by reverse transcription-PCR analysis of IL-1β, IL-6, IL-10, transforming growth factor beta, tumor necrosis factor alpha, and gamma interferon (IFN-γ) transcripts. Interestingly, when IFN-γ transcription is high, the number ofM. tuberculosisgenes expressed decreases and vice versa, whereas no mycobactericidal effect was observed in terms of bacterial growth. Expression of 11 genes was also studied in the twoM. tuberculosisstrains by infecting resting or activated MΦ and compared to bacterial intracellular survival. In both cases, a peculiar inverse correlation between expression of these genes and multiplication was observed. The number and type of genes expressed by the two strains differed significantly.
Alveolar Macrophage Deactivation in Murine Septic Peritonitis: Role of Interleukin 10
Authors: Reddy Raju C. , Chen Gina H. , Newstead Michael W. , Moore Tom , Zeng Xianying , Tateda Kazuhiro , Standiford Theodore J. 
Published: July 2002

ABSTRACTSepsis predisposes the host to a number of infectious sequelae, particularly the development of nosocomial pneumonia. Mechanisms by which sepsis results in impairment of lung antibacterial host defense have not been well defined. Alveolar macrophages (AM) represent important immune effector cells of the lung airspace. In this study, we examined the effects of cecal ligation and puncture (CLP) on murine AM function ex vivo, including the expression of proinflammatory cytokines and AM phagocytic activity. AM were harvested from mice subjected to a sham operation and CLP 24 h after laparotomy, adherence purified, and challenged with lipopolysaccharide (LPS) or left unstimulated. Both unstimulated and LPS-stimulated AM from mice subjected to CLP (CLP mice) produced significantly smaller amounts of proinflammatory cytokines tumor necrosis factor alpha and interleukin (IL-12) and C-X-C chemokines KC and macrophage inflammatory protein 2 than similarly treated AM from animals subjected to a sham operation. Furthermore, AM isolated from CLP mice displayed a marked impairment in phagocytic activity, as determined by flow cytometry, with this defect persisting to 48 h post-CLP. Induction of peritoneal sepsis syndrome resulted in a time-dependent increase in IL-10 in plasma and peritoneal fluid. Interestingly, the impairment in AM proinflammatory-cytokine production and phagocytic activity observed in AM from CLP mice was partially reversed by the in vivo neutralization of IL-10 prior to AM harvest. These observations suggest that abdominal sepsis syndrome results in significant impairment in AM effector cell function, which is mediated, in part, by sepsis-induced expression of IL-10.
Mycobacterium avium
Invades the Intestinal Mucosa Primarily by Interacting with Enterocytes
Authors: Sangari Felix J. , Goodman Joseph , Petrofsky Mary , Kolonoski Peter , Bermudez Luiz E. 
Published: July 2002

ABSTRACT

Previous studies have demonstrated that
Mycobacterium avium
can invade intestinal epithelial cells both in vitro and in vivo. When given to mice orally,
M. avium
preferentially interacts with the intestinal mucosa at the terminal ileum. We evaluated the mechanism(s) of
M. avium
binding and invasion of the intestinal mucosa using three different systems: (i) electron microscopy following administration of
M. avium
into an intestinal loop in mice, (ii) quantitative comparison of the bacterial load in Peyer's patch areas of the terminal ileum versus areas that do not contain Peyer's patches, and (iii) investigation of the ability of
M. avium
to cause disseminated infection following oral administration using B-cell-deficient mice, lacking Peyer's patches, in comparison with C57BL/6 black mice. By all approaches,
M. avium
was found to invade the intestinal mucosa by interacting primarily with enterocytes and not with M cells.