bluuebunny/crossref_metadata_2025_split huggingface dataset:
Upper and Lower Respiratory Tract Infection byStreptococcus pneumoniaeIs Affected by Pneumolysin Deficiency and Differences in Capsule Type
Authors: Kadioglu Aras , Taylor Sally , Iannelli Francesco , Pozzi Gianni , Mitchell Tim J. , Andrew Peter W. 
Published: July 2002

ABSTRACTPneumococci frequently colonize the upper respiratory tract, and these pneumococci are believed to act as a reservoir for infection of the lower respiratory tract and bacteremia. We investigated how the pneumococcal toxin pneumolysin affects the capacity of pneumococci to infect the upper and lower respiratory tract of the mouse. Wild-typeStreptococcus pneumoniaeserotype 2 and 3 strains, a serotype 2 pneumolysin-deficient mutant, and a serotype 2 mutant with the pneumolysin gene reinserted were used to study differences in colonization and disease. In addition, we also examined a pneumococcal chimeric mutant (capsule type switched from serotype 2 to serotype 3) to gain further insight into the role that capsule plays in nasopharyngeal infection. Absence of pneumolysin was found to be associated with significantly lower numbers of pneumococci in the nasopharynx, trachea, and lungs. Differences in pneumococcal capsule type were found to have significant effects on pneumococcal infection of the nasopharynx, trachea, and lungs. However, it was the combination of capsule type and genetic background that was important, and the influence of this combination varied with the site of infection. For example, in the nasopharynx the wild-type serotype 3 strain and the capsule-switched mutant behaved similarly, whereas in the lungs the mutant that was switched to serotype 3 survived less well than the wild-type serotype 3 strain. The combination of capsule type and genetic background also determined virulence. Thus, the wild-type serotype 3 strain was virulent, whereas the capsule-switched mutant was avirulent.
β-Defensin 1 Contributes to Pulmonary Innate Immunity in Mice
Authors: Moser Christian , Weiner Daniel J. , Lysenko Elena , Bals Robert , Weiser Jeffrey N. , Wilson James M. 
Published: July 2002

ABSTRACTInnate immunity serves as a first line defense in vertebrate organisms by providing an initial barrier to microorganisms and triggering antigen-specific responses. Antimicrobial peptides are thought to be effectors of innate immunity through their antibiotic activity and direct killing of microorganisms. Evidence to support this hypothesis in vertebrates is indirect, based on expression profiles and in vitro assays using purified peptides. Here we investigated the function of antimicrobial peptides in vivo using mice deficient in an antimicrobial peptide, mouse β-defensin-1 (mBD-1). We find that loss of mBD-1 results in delayed clearance ofHaemophilus influenzaefrom lung. These data demonstrate directly that antimicrobial peptides of vertebrates provide an initial block to bacteria at epithelial surfaces.
Phylogenetic Analysis and Prevalence of Urosepsis Strains of
Escherichia coli
Bearing Pathogenicity Island-Like Domains
Authors: Bingen-Bidois Martine , Clermont Olivier , Bonacorsi Stéphane , Terki Mustapha , Brahimi Naïma , Loukil Chawki , Barraud Dominique , Bingen Edouard 
Published: July 2002

ABSTRACT

We characterized 100
Escherichia coli
urosepsis isolates from adult patients according to host compromise status by means of ribotyping, PCR phylogenetic grouping, and PCR detection of
papG
alleles and the virulence-related genes
sfa/foc, fyuA
,
irp
-
2
,
aer
,
hly, cnf
-
1
and
hra
. We also tested these strains for copies of
pap
and
hly
and their direct physical linkage with other virulence genes in an attempt to look for pathogenicity islands (PAIs) described for the archetypal uropathogenic strains J96, CFT073, and 536. Most of the isolates belonged to
E. coli
phylogenetic groups B2 and D and bore
papG
allele II,
aer
, and
fyuA
/
irp
-
2. papG
allele II-bearing strains were more common in noncompromised patients, while
papG
allele-negative strains were significantly more frequent in compromised patients. Fifteen ribotypes were identified. The three archetypal strains harbored different ribotypes, and only one-third of our urosepsis strains were genetically related to one of the archetypal strains. Three and 18 strains harbored three and two copies of
pap
, respectively, and 5 strains harbored two copies of
hly. papGIII
was physically linked to
hly, cnf
-
1
, and
hra
(reported to be PAI II
J96
-like genetic elements) in 14% of the strains. The PAI II
J96
-like domain was inserted within
pheR
tRNA in 11 strains and near
leuX
tRNA in 3 strains. Moreover, the colocalized genes
cnf
-
1
,
hra
, and
hly
were physically linked to
papGII
in four strains and to no
pap
gene in three strains.
papGII
and
hly
(reported to be PAI I
CFT073
-like genetic elements) were physically linked in 16 strains, pointing to a PAI I
CFT073
-like domain. Three strains contained both a PAI II
J96
-like domain and a PAI I
CFTO73
-like domain. Forty-two strains harbored
papGII
but not
hly
, in keeping with the presence of a PAI II
CFT073
-like domain. Only one strain harbored a PAI I
536
-like domain (
hly
only), and none harbored a PAI I
J96
-like domain (
papGI
plus
hly
) or a PAI II
536
-like domain (
papGIII
plus
hly
). This study provides new data on the prevalence and variability of physical genetic linkage between
pap
and certain virulence-associated genes that are consistent with their colocalization on archetypal PAIs.
Proteome Analysis of Secreted Proteins of the Gastric Pathogen
Helicobacter pylori
Authors: Bumann Dirk , Aksu Sevil , Wendland Meike , Janek Katharina , Zimny-Arndt Uschi , Sabarth Nicolas , Meyer Thomas F. , Jungblut Peter R. 
Published: July 2002

ABSTRACT

Secreted proteins (the secretome) of the human pathogen
Helicobacter pylori
may mediate important pathogen-host interactions, but such proteins are technically difficult to analyze. Here, we report on a comprehensive secretome analysis that uses protein-free culture conditions to minimize autolysis, an efficient recovery method for extracellular proteins, and two-dimensional gel electrophoresis followed by peptide mass fingerprinting for protein resolution and identification. Twenty-six of the 33 separated secreted proteins were identified. Among them were six putative oxidoreductases that may be involved in the modification of protein-disulfide bonds, three flagellar proteins, three defined fragments of the vacuolating toxin VacA, the serine protease HtrA, and eight proteins of unknown function. A cleavage site for the amino-terminal passenger domain of VacA between amino acids 991 and 992 was determined by collision-induced dissociation mass spectrometry. Several of the secreted proteins are interesting targets for antimicrobial chemotherapy and vaccine development.
Candida albicans
Hyphal Formation and the Expression of the Efg1-Regulated Proteinases Sap4 to Sap6 Are Required for the Invasion of Parenchymal Organs
Authors: Felk Angelika , Kretschmar Marianne , Albrecht Antje , Schaller Martin , Beinhauer Sabine , Nichterlein Thomas , Sanglard Dominique , Korting Hans C. , Schäfer Wilhelm , Hube Bernhard 
Published: July 2002

ABSTRACT

The ability to change between yeast and hyphal cells (dimorphism) is known to be a virulence property of the human pathogen
Candida albicans
. The pathogenesis of disseminated candidosis involves adhesion and penetration of hyphal cells from a colonized mucosal site to internal organs. Parenchymal organs, such as the liver and pancreas, are invaded by
C. albicans
wild-type hyphal cells between 4 and 24 h after intraperitoneal (i.p.) infection of mice. In contrast, a hypha-deficient mutant lacking the transcription factor Efg1 was not able to invade or damage these organs. To investigate whether this was due to the inability to undergo the dimorphic transition or due to the lack of hypha-associated factors, we investigated the role of secreted aspartic proteinases during tissue invasion and their association with the different morphologies of
C. albicans
. Wild-type cells expressed a distinct pattern of
SAP
genes during i.p. infections. Within the first 72 h after infection,
SAP1
,
SAP2
,
SAP4
,
SAP5
,
SAP6
, and
SAP9
were the most commonly expressed proteinase genes. Sap1 to Sap3 antigens were found on yeast and hyphal cells, while Sap4 to Sap6 antigens were predominantly found on hyphal cells in close contact with host cells, in particular, eosinophilic leukocytes. Mutants lacking
EFG1
had either noticeably reduced or higher expressed levels of
SAP4
to
SAP6
transcripts in vitro depending on the culture conditions. During infection,
efg1
mutants had a strongly reduced ability to produce hyphae, which was associated with reduced levels of
SAP4
to
SAP6
transcripts. Mutants lacking
SAP1
to
SAP3
had invasive properties indistinguishable from those of wild-type cells. In contrast, a triple mutant lacking
SAP4
to
SAP6
showed strongly reduced invasiveness but still produced hyphal cells. When the tissue damage of liver and pancreas caused by single
sap4
,
sap5
, and
sap6
and double
sap4
and -
6
,
sap5
and -
6
, and
sap4
and -
5
double mutants was compared to the damage caused by wild-type cells, all mutants which lacked functional
SAP6
showed significantly reduced tissue damage. These data demonstrate that strains which produce hyphal cells but lack hypha-associated proteinases, particularly that encoded by
SAP6
, are less invasive. In addition, it can be concluded that the reduced virulence of hypha-deficient mutants is not only due to the inability to form hyphae but also due to modified expression of the
SAP
genes normally associated with the hyphal morphology.
A Common Step for Changing Cell Shape in Fruiting Body and Starvation-Independent Sporulation of
Myxococcus xanthus
Authors: Licking E. , Gorski L. , Kaiser D. 
Published: July 2002

ABSTRACT

Myxococcus xanthus
can sporulate in either of two ways: at the end of the program of fruiting body development or after exposure of growing cells to certain reagents such as concentrated glycerol. Fruiting body sporulation requires starvation, while glycerol sporulation requires rapid growth, and since the two types of spores are structurally somewhat different, it has generally been assumed that the two processes are different. However, a Tn
5
Lac insertion mutation, Ω7536, has been isolated which simultaneously blocks the development of fruiting body spores as well as glycerol-induced spores. Both sporulation pathways are blocked in the mutant within the process that converts a rod-shaped cell into a spherical spore. The Ω7536 locus is expressed at the time of cell shape change appropriate to each process, early after glycerol induction and late after starvation induction. On the C-signal response pathway, it is possible to identify positions for the normal function of the Ω7536 locus and for the inducing stimulus from glycerol that are unique and consistent with the observations. Although the two sporulation pathways differ in certain respects, it is shown that they share at least one step for changing a rod-shaped cell into a spherical spore.
Elo1p-Dependent Carboxy-Terminal Elongation of C14:1Δ
9
to C16:1Δ
11
Fatty Acids in
Saccharomyces cerevisiae
Authors: Schneiter Roger , Tatzer Verena , Gogg Gabriela , Leitner Erich , Kohlwein Sepp Dieter 
Published: July 2002

ABSTRACT

Saccharomyces cerevisiae
medium-chain acyl elongase (
ELO1
) mutants have previously been isolated in screens for fatty acid synthetase (FAS) mutants that fail to grow on myristic acid (C14:0)-supplemented media. Here we report that wild-type cells cultivated in myristoleic acid (C14:1Δ
9
)-supplemented media synthesized a novel unsaturated fatty acid that was identified as C16:1Δ
11
fatty acid by gas chromatography-mass spectroscopy. Synthesis of C16:1Δ
11
was dependent on a functional
ELO1
gene, indicating that Elo1p catalyzes carboxy-terminal elongation of unsaturated fatty acids (α-elongation). In wild-type cells, the C16:1Δ
11
elongation product accounted for approximately 12% of the total fatty acids. This increased to 18% in cells that lacked a functional acyl chain desaturase (
ole1
Δ mutants) and hence were fully dependent on uptake and elongation of C14:1. The observation that
ole1
Δ mutant cells grew almost like wild type on medium supplemented with C14:1 indicated that uptake and elongation of unsaturated fatty acids were efficient. Interestingly, wild-type cells supplemented with either C14:1 or C16:1 fatty acids displayed dramatic alterations in their phospholipid composition, suggesting that the availability of acyl chains is a dominant determinant of the phospholipid class composition of cellular membranes. In particular, the relative content of the two major phospholipid classes, phosphatidylethanolamine and phosphatidylcholine, was strongly dependent on the chain length of the supplemented fatty acid. Moreover, analysis of the acyl chain composition of individual phospholipid classes in cells supplemented with C14:1 revealed that the relative degree of acyl chain saturation characteristic for each phospholipid class appeared to be conserved, despite the gross alteration in the cellular acyl chain pool. Comparison of the distribution of fatty acids that were taken up and elongated (C16:1Δ
11
) to those that were endogenously synthesized by fatty acid synthetase and then desaturated by Ole1p (C16:1Δ
9
) in individual phospholipid classes finally suggested the presence of two different pools of diacylglycerol species. These results will be discussed in terms of biosynthesis of different phospholipid classes via either the de novo or the Kennedy pathway.
The Membrane-Bound H
+
-ATPase Complex Is Essential for Growth of
Lactococcus lactis
Authors: Koebmann Brian J. , Nilsson Dan , Kuipers Oscar P. , Jensen Peter R. 
Published: July 2002

ABSTRACT

The eight genes which encode the (F
1
F
o
) H
+
-ATPase in
Lactococcus lactis
subsp.
cremoris
MG1363 were cloned and sequenced. The genes were organized in an operon with the gene order
atpEBFHAGDC
; i.e., the order of
atpE
and
atpB
is reversed with respect to the more typical bacterial organization. The deduced amino acid sequences of the corresponding H
+
-ATPase subunits showed significant homology with the subunits from other organisms. Results of Northern blot analysis showed a transcript at approximately 7 kb, which corresponds to the size of the
atp
operon. The transcription initiation site was mapped by primer extension and coincided with a standard promoter sequence. In order to analyze the importance of the H
+
-ATPase for
L. lactis
physiology, a mutant strain was constructed in which the original
atp
promoter on the chromosome was replaced with an inducible nisin promoter. When grown on GM17 plates the resulting strain was completely dependent on the presence of nisin for growth. These data demonstrate that the H
+
-ATPase is essential for growth of
L. lactis
under these conditions.
Substrate Ambiguity of 3-Deoxy-
d
-
manno
-Octulosonate 8-Phosphate Synthase from
Neisseria gonorrhoeae
Revisited
Authors: Sheflyan Galina Ya , Sundaram Appavu K. , Taylor William P. , Woodard Ronald W. 
Published: July 2002

ABSTRACT

Homogeneous, recombinant 3-deoxy-
d
-
manno
-octulosonate 8-phosphate synthase from
Neisseria gonorrhoeae
is shown to catalyze the formation of 3-deoxy-
d
-
manno
-octulosonate 8-phosphate from phosphoenolpyruvate and
d
-arabinose 5-phosphate as determined from
1
H-nuclear magnetic resonance analysis of the product. This enzyme does not catalyze the condensation of
d
-erythrose 4-phosphate and phosphoenolpyruvate to form 3-deoxy-
d
-
ribo
-heptulosonate 7-phosphate, as was previously reported (P. S. Subramaniam, G. Xie, T. Xia, and R. A. Jensen, J. Bacteriol. 180:119–127, 1998).
A Truncated Soluble
Bacillus
Signal Peptidase Produced in
Escherichia coli
Is Subject to Self-Cleavage at Its Active Site
Authors: van Roosmalen M. L. , Jongbloed J. D. H. , Kuipers A. , Venema G. , Bron S. , van Dijl J. M. 
Published: July 2002

ABSTRACT

Soluble forms of
Bacillus
signal peptidases which lack their unique amino-terminal membrane anchor are prone to degradation, which precludes their high-level production in the cytoplasm of
Escherichia coli.
Here, we show that the degradation of soluble forms of the
Bacillus
signal peptidase SipS is largely due to self-cleavage. First, catalytically inactive soluble forms of this signal peptidase were not prone to degradation; in fact, these mutant proteins were produced at very high levels in
E. coli.
Second, the purified active soluble form of SipS displayed self-cleavage
in vitro
. Third, as determined by N-terminal sequencing, at least one of the sites of self-cleavage (between Ser15 and Met16 of the truncated enzyme) strongly resembles a typical signal peptidase cleavage site. Self-cleavage at the latter position results in complete inactivation of the enzyme, as Ser15 forms a catalytic dyad with Lys55. Ironically, self-cleavage between Ser15 and Met16 cannot be prevented by mutagenesis of Gly13 and Ser15, which conform to the −1, −3 rule for signal peptidase recognition, because these residues are critical for signal peptidase activity.
Characterization of the Hydrogen-Deuterium Exchange Activities of the Energy-Transducing HupSL Hydrogenase and H
2
-Signaling HupUV Hydrogenase in
Rhodobacter capsulatus
Authors: Vignais Paulette M. , Dimon Bernard , Zorin Nikolay A. , Tomiyama Masamitsu , Colbeau Annette 
Published: July 2002

ABSTRACT

Rhodobacter capsulatus
synthesizes two homologous protein complexes capable of activating molecular H
2
, a membrane-bound [NiFe] hydrogenase (HupSL) linked to the respiratory chain, and an H
2
sensor encoded by the
hupUV
genes. The activities of hydrogen-deuterium (H-D) exchange catalyzed by the
hupSL
-encoded and the
hupUV
-encoded enzymes in the presence of D
2
and H
2
O were studied comparatively. Whereas HupSL is in the membranes, HupUV activity was localized in the soluble cytoplasmic fraction. Since the hydrogenase gene cluster of
R. capsulatus
contains a gene homologous to
hoxH
, which encodes the large subunit of NAD-linked tetrameric soluble hydrogenases, the chromosomal
hoxH
gene was inactivated and
hoxH
mutants were used to demonstrate the H-D exchange activity of the cytoplasmic HupUV protein complex. The H-D exchange reaction catalyzed by HupSL hydrogenase was maximal at pH 4.5 and inhibited by acetylene and oxygen, whereas the H-D exchange catalyzed by the HupUV protein complex was insensitive to acetylene and oxygen and did not vary significantly between pH 4 and pH 11. Based on these properties, the product of the accessory
hypD
gene was shown to be necessary for the synthesis of active HupUV enzyme. The kinetics of HD and H
2
formed in exchange with D
2
by HupUV point to a restricted access of protons and gasses to the active site. Measurement of concentration changes in D
2
, HD, and H
2
by mass spectrometry showed that, besides the H-D exchange reaction, HupUV oxidized H
2
with benzyl viologen, produced H
2
with reduced methyl viologen, and demonstrated true hydrogenase activity. Therefore, not only with respect to its H
2
signaling function in the cell, but also to its catalytic properties, the HupUV enzyme represents a distinct class of hydrogenases.
The Large Resolvase TndX Is Required and Sufficient for Integration and Excision of Derivatives of the Novel Conjugative Transposon Tn
5397
Authors: Wang Hongmei , Mullany Peter 
Published: July 2002

ABSTRACT

Tn
5397
is a novel conjugative transposon, originally isolated from
Clostridium difficile
. This element can transfer between
C. difficile
strains and to and from
Bacillus subtilis
. It encodes a conjugation system that is very similar to that of Tn
916
. However, insertion and excision of Tn
5397
appears to be dependent on the product of the element encoded gene
tndX
, a member of the large resolvase family of site-specific recombinases. To test the role of
tndX
, the gene was cloned and the protein was expressed in
Escherichia coli
. The ability of TndX to catalyze the insertion and excision of derivatives (minitransposons) of Tn
5397
representing the putative circular and integrated forms, respectively, was investigated. TndX was required for both insertion and excision. Mutagenesis studies showed that some of the highly conserved amino acids at the N-terminal resolvase domain and the C-terminal nonconserved region of TndX are essential for activity. Analysis of the target site choices showed that the cloned Tn
5397
targets from
C. difficile
and
B. subtilis
were still hot spots for the minitransposon insertion in
E. coli
.
Effects of Major Spore-Specific DNA Binding Proteins on
Bacillus subtilis
Sporulation and Spore Properties
Authors: Setlow Barbara , McGinnis Kelly A. , Ragkousi Katerina , Setlow Peter 
Published: July 2002

ABSTRACT

Sporulation of a
Bacillus subtilis
strain (termed α
−
β
−
) lacking the majority of the α/β-type small, acid-soluble spore proteins (SASP) that are synthesized in the developing forespore and saturate spore DNA exhibited a number of differences from that of the wild-type strain, including delayed forespore accumulation of dipicolinic acid, overexpression of forespore-specific genes, and delayed expression of at least one mother cell-specific gene turned on late in sporulation, although genes turned on earlier in the mother cell were expressed normally in α
−
β
−
strains. The sporulation defects in α
−
β
−
strains were corrected by synthesis of chromosome-saturating levels of either of two wild-type, α/β-type SASP but not by a mutant SASP that binds DNA poorly. Spores from α
−
β
−
strains also exhibited less glutaraldehyde resistance and slower outgrowth than did wild-type spores, but at least some of these defects in α
−
β
−
spores were abolished by the synthesis of normal levels of α/β-type SASP. These results indicate that α/β-type SASP may well have global effects on gene expression during sporulation and spore outgrowth.