bluuebunny/crossref_metadata_2025_split huggingface dataset:
TheYersinia pestis caf1M1A1Fimbrial Capsule Operon Promotes Transmission by Flea Bite in a Mouse Model of Bubonic Plague
Authors: Sebbane Florent , Jarrett Clayton , Gardner Donald , Long Daniel , Hinnebusch B. Joseph 
Published: December 2008

ABSTRACTPlague is a zoonosis transmitted by fleas and caused by the gram-negative bacteriumYersinia pestis. During infection, the plasmidiccaf1M1A1operon that encodes theY. pestisF1 protein capsule is highly expressed, and anti-F1 antibodies are protective. Surprisingly, the capsule is not required for virulence after injection of cultured bacteria, even though it is an antiphagocytic factor and capsule-deficientY. pestisstrains are rarely isolated. We found that acaf-negativeY. pestismutant was not impaired in either flea colonization or virulence in mice after intradermal inoculation of cultured bacteria. In contrast, absence of thecafoperon decreased bubonic plague incidence after a flea bite. Successful development of plague in mice infected by flea bite with thecaf-negative mutant required a higher number of infective bites per challenge. In addition, the mutant displayed a highly autoaggregative phenotype in infected liver and spleen. The results suggest that acquisition of thecaflocus via horizontal transfer by an ancestralY. pestisstrain increased transmissibility and the potential for epidemic spread. In addition, our data support a model in which atypicalcaf-negative strains could emerge during climatic conditions that favor a high flea burden. Human infection with such strains would not be diagnosed by the standard clinical tests that detect F1 antibody or antigen, suggesting that more comprehensive surveillance for atypicalY. pestisstrains in plague foci may be necessary. The results also highlight the importance of studyingY. pestispathogenesis in the natural context of arthropod-borne transmission.
Defects in Innate Immunity Predispose C57BL/6J-Leprdb/LeprdbMice to Infection byStaphylococcus aureus
Authors: Park Sunny , Rich Jeremy , Hanses Frank , Lee Jean C. 
Published: December 2008

ABSTRACTFoot and ankle infections are the most common cause of hospitalization among diabetic patients, andStaphylococcus aureusis a major pathogen implicated in these infections. Patients with insulin-resistant (type 2) diabetes are more susceptible to bacterial infections than nondiabetic subjects, but the pathogenesis of these infections is poorly understood. C57BL/6J-Leprdb/Leprdb(hereafter,db/db) mice develop type 2 diabetes due to a recessive, autosomal mutation in the leptin receptor. We established aS. aureushind paw infection in diabeticdb/dband nondiabeticLepr+/+(+/+) mice to investigate host factors that predispose diabetic mice to infection. Nondiabetic +/+ mice resolved theS. aureushind paw infection within 10 days, whereasdb/dbmice with persistent hyperglycemia developed a chronic infection associated with a high bacterial burden. Diabeticdb/dbmice showed a more robust neutrophil infiltration to the infection site and higher levels of chemokines in the infected tissue than +/+ mice. Blood from +/+ mice killedS. aureusin vitro, whereasdb/dbblood was defective in bacterial killing. Compared with peripheral blood neutrophils from +/+ mice,db/dbneutrophils demonstrated a diminished respiratory burst when stimulated withS. aureus. However, bone marrow-derived neutrophils from +/+ anddb/dbmice showed comparable phagocytosis and bactericidal activity. Our results indicate that diabeticdb/dbmice are more susceptible to staphylococcal infection than their nondiabetic littermates and that persistent hyperglycemia modulates innate immunity in the diabetic host.
GbdR Regulates
Pseudomonas aeruginosa plcH
and
pchP
Transcription in Response to Choline Catabolites
Authors: Wargo Matthew J. , Ho Tiffany C. , Gross Maegan J. , Whittaker Laurie A. , Hogan Deborah A. 
Published: December 2008

ABSTRACT

Pseudomonas aeruginosa
hemolytic phospholipase C, PlcH, can degrade phosphatidylcholine (PC) and sphingomyelin in eukaryotic cell membranes and extracellular PC in lung surfactant. Numerous studies implicate PlcH in
P. aeruginosa
virulence. The phosphorylcholine released by PlcH activity on phospholipids is hydrolyzed by a periplasmic phosphorylcholine phosphatase, PchP. Both
plcH
gene expression and PchP enzyme activity are positively regulated by phosphorylcholine degradation products, including glycine betaine. Here we report that the induction of
plcH
and
pchP
transcription by glycine betaine is mediated by GbdR, an AraC family transcription factor. Mutants that lack
gbdR
are unable to induce
plcH
and
pchP
in media containing glycine betaine or choline and in phosphatidylcholine-rich environments, such as lung surfactant or mouse lung lavage fluid. In T broth containing choline, the
gbdR
mutant exhibited a 95% reduction in PlcH activity. In electrophoretic mobility shift assays, a GbdR-maltose binding protein fusion bound specifically to both the
plcH
and
pchP
promoters. Promoter mapping, alignment of GbdR-regulated promoter sequences, and analysis of targeted promoter mutants that lack GbdR-dependent induction of transcription were used to identify a region necessary for GbdR-dependent transcriptional activation. GbdR also plays a significant role in
plcH
and
pchP
regulation within the mouse lung. Our studies suggest that GbdR is the primary regulator of
plcH
and
pchP
expression in PC-rich environments, such as the lung, and that
pchP
and other genes involved in phosphorylcholine catabolism are necessary to stimulate the GbdR-mediated positive feedback induction of
plcH
.
Role of Neutrophils in Response toBordetella pertussisInfection in Mice
Authors: Andreasen Charlotte , Carbonetti Nicholas H. 
Published: December 2008

ABSTRACTPertussis is an acute respiratory disease caused by the bacteriumBordetella pertussis, for which humans are the only known reservoir. During infection,B. pertussisreleases several toxins, including pertussis toxin (PT) and adenylate cyclase toxin (ACT), which have both been shown to play roles in promoting bacterial growth during early infection in a mouse model. Furthermore, in vitro and in vivo studies suggest that PT and ACT affect neutrophil chemotaxis and/or function, thereby altering the innate immune response. In this study we depleted animals of neutrophils to investigate whether neutrophils play a protective role duringB. pertussisinfection in mice. In addition, by infection with toxin-deficient strains, we investigated whether neutrophils are the main targets for PT and/or ACT activity in promoting bacterial growth. Surprisingly, we found no role for neutrophils duringB. pertussisinfection in naïve mice. However, in previously infected (immune) mice or in mice receiving immune serum, we observed a significant role for neutrophils during infection. Furthermore, in this immune mouse model our evidence indicates that neutrophils appear to be the main target cells for ACT, but not for PT.
Proinflammatory Response of Human Osteoblastic Cell Lines and Osteoblast-Monocyte Interaction upon Infection withBrucellaspp
Authors: Delpino M. Victoria , Fossati Carlos A. , Baldi Pablo C. 
Published: December 2008

ABSTRACTThe ability ofBrucellaspp. to infect human osteoblasts and the cytokine response of these cells to infection were investigated in vitro.Brucella abortus, B. suis, B. melitensis, andB. caniswere able to infect the SaOS-2 and MG-63 osteoblastic cell lines, and the first three species exhibited intracellular replication.B. abortusinternalization was not significantly affected by pretreatment of cells with cytochalasin D but was inhibited up to 92% by colchicine. AvirB10mutant ofB. abortuscould infect but not replicate within osteoblasts, suggesting a role for the type IV secretion system in intracellular survival. Infected osteoblasts produced low levels of chemokines (interleukin-8 [IL-8] and macrophage chemoattractant protein 1 [MCP-1]) and did not produce proinflammatory cytokines (IL-1β, IL-6, and tumor necrosis factor alpha [TNF-α]). However, osteoblasts stimulated with culture supernatants fromBrucella-infected human monocytes (THP-1 cell line) produced chemokines at levels 12-fold (MCP-1) to 17-fold (IL-8) higher than those of infected osteoblasts and also produced IL-6. In the inverse experiment, culture supernatants fromBrucella-infected osteoblasts induced the production of IL-8, IL-1β, IL-6, and TNF-α by THP-1 cells. The induction of TNF-α and IL-1β was largely due to granulocyte-macrophage colony-stimulating factor produced by infected osteoblasts, as demonstrated by inhibition with a specific neutralizing antibody. This study shows thatBrucellacan invade and replicate within human osteoblastic cell lines, which can directly and indirectly mount a proinflammatory response. Both phenomena may have a role in the chronic inflammation and bone and joint destruction observed in osteoarticular brucellosis.
Retentive Memory of Bacteria: Long-Term Regulation of Dehalorespiration in
Sulfurospirillum multivorans
Authors: John Markus , Rubick Raffael , Schmitz Roland P. H. , Rakoczy Jana , Schubert Torsten , Diekert Gabriele 
Published: December 2008

ABSTRACT

The gram-negative, strictly anaerobic epsilonproteobacterium
Sulfurospirillum multivorans
is able to gain energy from dehalorespiration with tetrachloroethene (perchloroethylene [PCE]) as a terminal electron acceptor. The organism can also utilize fumarate as an electron acceptor. Prolonged subcultivation of
S. multivorans
in the absence of PCE with pyruvate as an electron donor and fumarate as an electron acceptor resulted in a decrease of PCE dehalogenase (PceA) activity. Concomitantly, the
pceA
transcript level equally decreased as shown by reverse transcriptase PCR. After 35 subcultivations (approximately 105 generations), a
pceA
transcript was not detectable and the PceA protein and activity were completely absent. In such long-term subcultivated
S. multivorans
cells, the biosynthesis of catalytically active PceA was restored to the initial level within about 50 h (approximately three generations) by the addition of PCE or trichloroethene. Single colonies obtained from PceA-depleted cultures were able to induce PCE dechlorination, indicating that long-term subcultured cells still contained the functional
pceA
gene. The results point to a novel type of long-term regulation of PCE dehalogenase gene expression in
S. multivorans
.
Allosteric Coupling between the Lid and Interdomain Linker in DnaK Revealed by Inhibitor Binding Studies
Authors: Liebscher Markus , Roujeinikova Anna 
Published: December 2008

ABSTRACTThe molecular chaperone DnaK assists protein folding and refolding, translocation across membranes, and regulation of the heat shock response. InEscherichia coli, the protein is a target for insect-derived antimicrobial peptides, pyrrhocoricins. We present here the X-ray crystallographic analysis of theE. coliDnaK substrate-binding domain in complex with pyrrhocoricin-derived peptide inhibitors. The structures show that pyrrhocoricins act as site-specific, dual-mode (competitive and allosteric) inhibitors, occupying the substrate-binding tunnel and disrupting the latch between the lid and the β-sandwich. Our structural analysis revealed an allosteric coupling between the movements of the lid and the interdomain linker, identifying a previously unknown mechanism of the lid-mediated regulation of the chaperone cycle.
Bacteriocin Activity of
Streptococcus pneumoniae
Is Controlled by the Serine Protease HtrA via Posttranscriptional Regulation
Authors: Dawid Suzanne , Sebert Michael E. , Weiser Jeffrey N. 
Published: December 2008

ABSTRACT

The
blp
locus of a type 6A strain of
Streptococcus pneumoniae
encodes a two-peptide bacteriocin, pneumocin MN, which mediates intraspecies competition during mouse nasopharyngeal colonization. This locus is regulated by a quorum-sensing mechanism consisting of a dedicated two-component regulatory system and a peptide pheromone. Like most clinical isolates, this type 6A strain can be separated into opaque and transparent colony variants, each playing a different role during pneumococcal infection. In this study, we show that the
blp
locus is differentially regulated at the posttranscriptional level in pneumococcal opacity variants. Transparent and opaque variants produce equivalent amounts of
blpMNPO
transcript when stimulated with a synthetic pheromone, but transparent variants have no pneumocin MN-mediated inhibitory activity while opaque variants produce large zones of inhibitory activity. The differential regulation in opacity variants is driven by the two-component regulatory system CiaRH via its regulation of the serine protease HtrA. Transparent mutants deficient in CiaH or HtrA show increased pneumocin MN-mediated inhibition. In addition, these mutants demonstrate alterations in their dose response to a synthetic peptide pheromone, suggesting that HtrA activity impacts pneumocin MN production at the level of signaling. This, in addition to its known effects on competence, suggests that HtrA is a pleiotropic regulator whose protease activity affects several important bacterial pathways. The complex regulation of pneumocins may allow the pneumococcus to reserve the secretion of active peptides for situations where the benefit of their inhibitory activity outweighs the cost of their production.
Identification of a Divided Genome for VSH-1, the Prophage-Like Gene Transfer Agent of
Brachyspira hyodysenteriae
Authors: Stanton Thaddeus B. , Humphrey Samuel B. , Bayles Darrell O. , Zuerner Richard L. 
Published: December 2008

ABSTRACT

The
Brachyspira hyodysenteriae
B204 genome sequence revealed three VSH-1 tail genes,
hvp31
,
hvp60
, and
hvp37
, in a 3.6-kb cluster. The location and transcription direction of these genes relative to those of the previously described VSH-1 16.3-kb gene operon indicate that the gene transfer agent VSH-1 has a noncontiguous, divided genome.
A
Campylobacter jejuni znuA
Orthologue Is Essential for Growth in Low-Zinc Environments and Chick Colonization
Authors: Davis Lindsay M. , Kakuda Tsutomu , DiRita Victor J. 
Published: December 2008

ABSTRACT

Campylobacter jejuni
infection is a leading cause of bacterial gastroenteritis in the United States and is acquired primarily through the ingestion of contaminated poultry products. Here, we describe the
C. jejuni
orthologue of ZnuA in other gram-negative bacteria. ZnuA (Cj0143c) is the periplasmic component of a putative zinc ABC transport system and is encoded on a zinc-dependent operon with Cj0142c and Cj0141c, which encode the other two likely components of the transport system of
C. jejuni
. Transcription of these genes is zinc dependent. A mutant lacking Cj0143c is growth deficient in zinc-limiting media, as well as in the chick gastrointestinal tract. The protein is glycosylated at asparagine 28, but this modification is dispensable for zinc-limited growth and chick colonization. Affinity-purified FLAG-tagged Cj0143c binds zinc in vitro. Based on our findings and on its homology to
E. coli
ZnuA, we conclude that Cj0143c encodes the
C. jejuni
orthologue of ZnuA.
Hypomodification of the Wobble Base in tRNA
Glu
, tRNA
Lys
, and tRNA
Gln
Suppresses the Temperature-Sensitive Phenotype Caused by Mutant Release Factor 1
Authors: Isak Georgina , Rydén-Aulin Monica 
Published: December 2008

ABSTRACT

In
Escherichia coli
, release factor 1 (RF1) is one of two RFs that mediate termination; it specifically recognizes UAA and UAG stop codons. A mutant allele,
prfA1
, coding for an RF1 that causes temperature-sensitive (Ts) growth at 42°C, was used to select for temperature-resistant (Ts
+
) suppressors. This study describes one such suppressor that is the result of an IS
10
insertion into the
cysB
gene, giving a Cys
−
phenotype. CysB is a transcription factor regulating the
cys
regulon, mainly as an activator, which explains the Cys
−
phenotype. We have found that suppression is a consequence of the lost ability to donate sulfur to enzymes involved in the synthesis of thiolated nucleosides. From genetic analyses we conclude that it is the lack of the 5-methylaminomethyl-2-thiouridine (mnm
5
s
2
U) modification of the wobble base of tRNA
Glu
, tRNA
Lys
, and/or tRNA
Gln
that causes the suppressor phenotype.
Comparative Proteomic Analysis of the
Haemophilus ducreyi
Porin-Deficient Mutant 35000HP::P2AB
Authors: Davie Jeremiah J. , Campagnari Anthony A. 
Published: December 2008

ABSTRACT

Haemophilus ducreyi
is an obligate human pathogen and the causative agent of the sexually transmitted, genital ulcerative disease chancroid. The genome of strain 35000HP contains two known porin proteins, OmpP2A and OmpP2B. Loss of OmpP2A and OmpP2B expression in the mutant 35000HP::P2AB resulted in no obvious growth defect or phenotype. Comparison of outer membrane profiles indicated increased expression of the 58.5-kDa chaperone, GroEL, in the porin-deficient mutant. A proteomics-based comparison resulted in the identification of 231 proteins present in membrane-associated protein samples, of which a subset of 56 proteins was differentially expressed at a level of 1.5-fold or greater in the porin-deficient strain 35000HP::P2AB relative to that in 35000HP. Twenty of the differentially expressed proteins were selected for real-time PCR, resulting in the validation of 90% of the selected subgroup. Proteins identified in these studies suggested a decreased membrane stability phenotype, which was verified by disk diffusion assay. Loss of OmpP2A and OmpP2B resulted in global protein expression changes which appear to compensate for the absence of porin expression in 35000HP::P2AB.
sarZ
, a
sarA
Family Gene, Is Transcriptionally Activated by MgrA and Is Involved in the Regulation of Genes Encoding Exoproteins in
Staphylococcus aureus
Authors: Ballal Anand , Ray Binata , Manna Adhar C. 
Published: December 2008

ABSTRACT

The expression of genes involved in the pathogenesis of
Staphylococcus aureus
is controlled by global regulatory loci, including two-component regulatory systems and transcriptional regulators (e.g.,
sar
family genes). Most members of the SarA family have been partially characterized and shown to regulate a large numbers of target genes. Here, we describe the characterization of
sarZ
, a
sarA
paralog from
S. aureus
, and its regulatory relationship with other members of its family. Expression of
sarZ
was growth phase dependent with maximal expression in the early exponential phase of growth. Transcription of
sarZ
was reduced in an
mgrA
mutant and returned to a normal level in a complemented
mgrA
mutant strain, which suggests that
mgrA
acts as an activator of
sarZ
transcription. Purified MgrA protein bound to the
sarZ
promoter region, as determined by gel shift assays. Among the
sarA
family of genes analyzed, inactivation of
sarZ
increased
sarS
transcription, while it decreased
agr
transcription. The expression of potential target genes involved in virulence was evaluated in single and double mutants of
sarZ
with
mgrA
,
sarX
, and
agr
. Northern and zymogram analyses indicated that the
sarZ
gene product played a role in regulating several virulence genes, particularly those encoding exoproteins. Gel shift assays demonstrated nonspecific binding of purified SarZ protein to the promoter regions of the
sarZ
-regulated target genes. These results demonstrate the important role played by SarZ in controlling regulatory and virulence gene expression in
S. aureus
.
Conditional Essentiality of thecsrAGene inEscherichia coli
Authors: Timmermans Johan , Van Melderen Laurence 
Published: December 2008

ABSTRACTCsrA is a global posttranscriptional regulator of numerous physiological processes, such as glycogenesis and glycolysis. Here, we show that thecsrAgene ofEscherichia coliis essential for growth on LB and on synthetic medium containing glycolytic carbon sources. However,csrAis not necessary for growth on synthetic medium containing pyruvate, showing that the Krebs cycle is functional in thecsrA::catdeletion mutant. Deletion of theglgCAPoperon in thecsrA::catmutant restored the ability to grow on LB and on synthetic medium containing glycolytic carbon sources, showing that growth inhibition is due to an excess of glycogen synthesis.
The relationship between local clean indoor air policies and smoking behaviours in Minnesota youth
Authors: Klein E G , Forster J L , Erickson D J , Lytle L A , Schillo B 
Published: December 2008

Background:While clean indoor air (CIA) policies are intended to reduce exposure to second-hand smoke in the workplace, restrictions in public workplaces have the potential to discourage youth smoking. There is growing evidence from cross-sectional and ecological studies, but limited evidence from longitudinal studies that this is so.Objective:To evaluate the association between local CIA policies and smoking behaviours among Minnesota youth over time.Design, setting and subjects:A cohort of 4233 Minnesota youths, ages 11 to 16 at baseline, was interviewed via telephone for 6 years (2000–2006). Individual, family and community level variables were collected from participants every 6 months. A generalised estimating equation (GEE) logistic regression was used to assess the relationship between CIA policies and past-month smoking in youth over time. The analysis was controlled for potential confounders at individual and community levels.Results:There was not significant association between CIA policies and youth smoking behaviours in the multivariate analyses. At the individual level, parental smoking significantly increased the odds of smoking nearly 40% and close friend smoking increased the odds of past-month smoking by nearly 100% for each close friend. Banning smoking in the home was significantly associated with a 12% reduction in the odds of past-month smoking.Conclusion:After accounting for other community and individual level factors known to be associated with youth smoking, there was no significant association between CIA policies and past-month smoking for youth over time.
Sound and complete relevance assessment for XML retrieval
Authors: Piwowarski Benjamin , Trotman Andrew , Lalmas Mounia 
Published: December 2008

In information retrieval research, comparing retrieval approaches requires test collections consisting of documents, user requests and relevance assessments. Obtaining relevance assessments that are as sound and complete as possible is crucial for the comparison of retrieval approaches. In XML retrieval, the problem of obtaining sound and complete relevance assessments is further complicated by the structural relationships between retrieval results.
A major difference between XML retrieval and flat document retrieval is that the relevance of elements (the retrievable units) is not independent of that of related elements. This has major consequences for the gathering of relevance assessments. This article describes investigations into the creation of sound and complete relevance assessments for the evaluation of content-oriented XML retrieval as carried out at INEX, the evaluation campaign for XML retrieval. The campaign, now in its seventh year, has had three substantially different approaches to gather assessments and has finally settled on a highlighting method for marking relevant passages within documents—even though the objective is to collect assessments at element level. The different methods of gathering assessments at INEX are discussed and contrasted. The highlighting method is shown to be the most reliable of the methods.