bluuebunny/crossref_metadata_2025_split huggingface dataset:
Transcutaneous Immunization Using Colonization Factor and Heat-Labile Enterotoxin Induces Correlates of Protective Immunity for EnterotoxigenicEscherichia coli
Authors: Yu Jianmei , Cassels Frederick , Scharton-Kersten Tanya , Hammond Scott A. , Hartman Antoinette , Angov Evelina , Corthésy Blaise , Alving Carl , Glenn Gregory 
Published: July 2002

ABSTRACTEnterotoxigenicEscherichia coli(ETEC) diarrheal disease is a worldwide problem that may be addressed by transcutaneous delivery of a vaccine. In several human settings, protective immunity has been associated with immune responses toE. colicolonization factors and to the heat-labile toxin that induces the diarrhea. In this set of animal studies, transcutaneous immunization (TCI) using recombinant colonization factor CS6 and cholera toxin (CT) or heat-labile enterotoxin (LT) as the adjuvant induced immunoglobulin G (IgG) and IgA anti-CS6 responses in sera and stools and antibody responses that recognized CS6 antigen in its native configuration. The antitoxin immunity induced by TCI was also shown to protect against enteric toxin challenge. Although immunization with LT via the skin induced mucosal secretory IgA responses to LT, protection could also be achieved by intravenous injection of the immune sera. Finally, a malaria vaccine antigen, merzoite surface protein 142administered with CT as the adjuvant, induced both merzoite surface protein antibodies and T-cell responses while conferring protective antitoxin immunity, suggesting that both antiparasitic activity and antidiarrheal activity can be obtained with a single vaccine formulation. Overall, our results demonstrate that relevant colonization factor and antitoxin immunity can be induced by TCI and suggest that an ETEC traveler's diarrhea vaccine could be delivered by using a patch.
Human Gingival Fibroblasts Rescue Butyric Acid-Induced T-Cell Apoptosis
Authors: Kurita-Ochiai Tomoko , Ochiai Kuniyasu , Suzuki Naoto , Otsuka Kichibee , Fukushima Kazuo 
Published: July 2002

ABSTRACTWe previously demonstrated that butyric acid, an extracellular metabolite from periodontopathic bacteria, induces cytotoxicity and apoptosis in murine thymocytes, splenic T cells, and human Jurkat T cells. In this study, we used a cell-to-cell interaction system to examine the contribution of gingival fibroblasts to the regulation of T-cell death induced by butyric acid. Butyric acid slightly suppressed fibroblast viability in a concentration-dependent fashion. However, DNA fragmentation assays indicated that butyric acid did not induce apoptosis for up to 21 h in human gingival fibroblasts (Gin 1, F41-G, and H. pulp cells). The culture supernatants were assayed for interleukin 1α (IL-1α), IL-1β, IL-6, IL-8, IL-11, tumor necrosis factor alpha, and transforming growth factor β, but only the IL-6, IL-8, and IL-11 levels were significantly increased by addition of butyric acid. Butyric acid- or Fas-induced Jurkat-cell apoptosis was attenuated when Jurkat cells were cocultured with either F41-G or Gin 1 cells that had been preincubated for 6 h with butyric acid. IL-8 slightly stimulated butyric acid- or Fas-induced Jurkat-cell apoptosis in a dose-dependent manner, although a low dose of IL-8 had a mildly inhibitory effect on apoptosis. In contrast, IL-6 and IL-11 significantly suppressed butyric acid- or Fas-induced apoptosis in a dose-dependent fashion. Furthermore, the addition of monoclonal antibodies against human IL-6 and IL-11 to cocultures of gingival fibroblasts and Jurkat cells partially eliminated T-cell recovery. These results suggest that the proinflammatory cytokines such as IL-6 and IL-11, produced in fibroblasts stimulated with butyric acid, are involved in the attenuation of T-cell apoptosis by gingival fibroblasts.
Autonomous Expression of the
slo
Gene of the Bicistronic
nga
-
slo
Operon of
Streptococcus pyogenes
Authors: Savic Dragutin J. , McShan William M. , Ferretti Joseph J. 
Published: July 2002

ABSTRACT

A recent model for cytolysin-mediated translocation in
Streptococcus pyogenes
proposes that NAD-glycohydrolase is translocated through streptolysin O-generated pores into a host cell (J. Madden, N. Ruiz, and M. Caparon, Cell 104:143-152, 2001). This model also assumes that the NAD-glycohydrolase (
nga
) and streptolysin O (
slo
) genes that code for these products are organized in an operon-like structure expressed from a single promoter only (
nga
). We expand this model by showing that
slo
possesses its own autonomous promoter, which is located 155 bp upstream of the
slo
gene. Under experimental conditions in which
S. pyogenes
is grown in THY medium, the strength of the
slo
promoter, as measured by the activity of a
lacZ
reporter gene, resulted in low but highly reproducible values. Finally, we demonstrated that
sloR
, a
S. pyogenes
gene that closely resembles the
Clostridium perfringens pfoR
gene, exerts a negative effect on the expression of the
slo
gene.
Purification and Characterization of the R64 Shufflon-Specific Recombinase
Authors: Gyohda Atsuko , Komano Teruya 
Published: July 2002

ABSTRACT

The shufflon, a multiple DNA inversion system in plasmid R64, consists of four invertible DNA segments which are separated and flanked by seven 19-bp repeat sequences. The product of a site-specific recombinase gene,
rci
, promotes site-specific recombination between any two of the inverted 19-bp repeat sequences of the shufflon. To analyze the molecular mechanism of this recombination reaction, Rci protein was overproduced and purified. The purified Rci protein promoted the in vitro recombination reaction between the inverted 19-bp repeats of supercoiled DNA of a plasmid carrying segment A of the R64 shufflon. The recombination reaction was enhanced by the bacterial host factor HU. Gel electrophoretic analysis indicated that the Rci protein specifically binds to the DNA segments carrying the 19-bp sequences. The binding affinity of the Rci protein to the four shufflon segments as well as four synthetic 19-bp sequences differed greatly: among the four 19-bp repeat sequences, the repeat-a and -d sequences displayed higher affinity to Rci protein. These results suggest that the differences in the affinity of Rci protein for the 19-bp repeat sequences determine the inversion frequencies of the four segments.
Altered Stationary-Phase Response in a
Borrelia burgdorferi rpoS
Mutant
Authors: Elias Abdallah F. , Bono James L. , Carroll James A. , Stewart Philip , Tilly Kit , Rosa Patricia 
Published: July 2002

ABSTRACT

The homolog of the chromosomally encoded stationary-phase sigma factor
RpoS
in
Borrelia burgdorferi
was inactivated using

gyrB
r

as a selectable marker. Two-dimensional nonequilibrium pH gradient electrophoresis of stationary-phase cell lysates identified at least 11 differences between the protein profiles of the
rpoS
mutant and wild-type organisms. Wild-type
B. burgdorferi
had a growth phase-dependent resistance to 1 N NaCl, similar to the stationary-phase response reported for other bacteria. The
B. burgdorferi rpoS
mutant strain was less resistant to osmotic stress in stationary phase than the isogenic
rpoS
wild-type organism. The results indicate that the
B. burgdorferi rpoS
homolog influences protein composition and participates in stationary-phase-dependent osmotic resistance. This
rpoS
mutant will be useful for studying regulation of gene expression in response to changing environmental conditions.
Interaction of the FimB Integrase with the
fimS
Invertible DNA Element in
Escherichia coli
In Vivo and In Vitro
Authors: Burns Lesley S. , Smith Stephen G. J. , Dorman Charles J. 
Published: July 2002

ABSTRACT

The FimB protein is a site-specific recombinase that inverts the
fimS
genetic switch in
Escherichia coli
. Based on amino acid sequence analysis alone, FimB has been assigned to the integrase family of tyrosine recombinases. We show that amino acid substitutions at positions R47, H141, R144, and Y176, corresponding to highly conserved members of the catalytic motif of integrase proteins, render FimB incapable of inverting the
fimS
element in vivo. The arginine substitutions reduced the ability of FimB to bind to
fimS
in vivo or in vitro, while the substitution R144Q resulted in a protein unable to bind independently to the half sites located at the left end of
fimS
in phase-on bacteria. These data confirm that FimB is an integrase and suggest that residue R144 has a role in binding to a specific component of the
fim
switch.
Interacting Regulatory Circuits Involved in Orderly Control of Photosynthesis Gene Expression in
Rhodobacter sphaeroides
2.4.1
Authors: Oh Jeong-Il , Eraso Jesus M. , Kaplan Samuel 
Published: July 2002

ABSTRACT

FnrL, the homolog of the global anaerobic regulator Fnr, is required for the induction of the photosynthetic apparatus in
Rhodobacter sphaeroides
2.4.1. Thus, the precise role of FnrL in photosynthesis (PS) gene expression and its interaction(s) with other regulators of PS gene expression are of considerable importance to our understanding of the regulatory circuitry governing spectral complex formation. Using a CcoP and FnrL double mutant strain, we obtained results which suggested that FnrL is not involved in the transduction of the inhibitory signal, by which PS gene expression is “silenced,” emanating from the
cbb
3
oxidase encoded by the
ccoNOQP
operon under aerobic conditions. The dominant effect of the
ccoP
mutation in the FnrL mutant strain with respect to spectral complex formation under aerobic conditions and restoration of a PS-positive phenotype suggested that inactivation of the
cbb
3
oxidase to some extent bypasses the requirement for FnrL in the formation of spectral complexes. Additional analyses revealed that anaerobic induction of the
bchE
,
hemN
, and
hemZ
genes, which are involved in the tetrapyrrole biosynthetic pathways, requires FnrL. Thus, FnrL appears to be involved at multiple loci involved in the regulation of PS gene expression. Additionally,
bchE
was also shown to be regulated by the PrrBA two-component system, in conjunction with
hemN
and
hemZ
. These and other results to be discussed permit us to more accurately describe the role of FnrL as well as the interactions between the FnrL, PrrBA, and other regulatory circuits in the regulation of PS gene expression.
Phosphorelay as the Sole Physiological Route of Signal Transmission by the Arc Two-Component System of
Escherichia coli
Authors: Kwon Ohsuk , Georgellis Dimitris , Lin E. C. C. 
Published: July 2002

ABSTRACT

The Arc two-component system, comprising a tripartite sensor kinase (ArcB) and a response regulator (ArcA), modulates the expression of numerous genes involved in respiratory functions. In this study, the steps of phosphoryl group transfer from phosphorylated ArcB to ArcA were examined in vivo by using single copies of wild-type and mutant
arcB
alleles. The results indicate that the signal transmission occurs solely by His-Asp-His-Asp phosphorelay.
All Major Regions of FtsK Are Required for Resolution of Chromosome Dimers
Authors: Boyle David S. , Grant Dawn , Draper G. Craig , Donachie William D. 
Published: July 2002

ABSTRACT

Resolution of chromosome dimers, by site-specific recombination between
dif
sites, is carried out in
Escherichia coli
by XerCD recombinase in association with the FtsK protein. We show here that a variety of altered FtsK polypeptides, consisting of the N-terminal (cell division) domain alone or with deletions in the proline-glutamine-rich part of the protein, or polypeptides consisting of the C-terminal domain alone are all unable to carry out
dif
recombination. Alteration of the putative nucleotide-binding site also abolishes the ability of FtsK to carry out recombination between
dif
sites.
Cross-Linked Complex between Oligomeric Periplasmic Lipoprotein AcrA and the Inner-Membrane-Associated Multidrug Efflux Pump AcrB from
Escherichia coli
Authors: Zgurskaya Helen I. , Nikaido Hiroshi 
Published: July 2002

ABSTRACT

In
Escherichia coli
, the intrinsic levels of resistance to multiple antimicrobial agents are produced through expression of the three-component multidrug efflux system AcrAB-TolC. AcrB is a proton-motive-force-dependent transporter located in the inner membrane, and AcrA and TolC are accessory proteins located in the periplasm and the outer membrane, respectively. In this study, these three proteins were expressed separately, and the interactions between them were analyzed by chemical cross-linking in intact cells. We show that AcrA protein forms oligomers, most probably trimers. In this oligomeric form, AcrA interacts specifically with AcrB transporter independently of substrate and TolC.
Identification, Evolution, and Essentiality of the Mevalonate Pathway for Isopentenyl Diphosphate Biosynthesis in Gram-Positive Cocci
Authors: Wilding E. Imogen , Brown James R. , Bryant Alexander P. , Chalker Alison F. , Holmes David J. , Ingraham Karen A. , Iordanescu Serban , So Chi Y. , Rosenberg Martin , Gwynn Michael N. 
Published: July 2002

ABSTRACT

The mevalonate pathway and the glyceraldehyde 3-phosphate (GAP)–pyruvate pathway are alternative routes for the biosynthesis of the central isoprenoid precursor, isopentenyl diphosphate. Genomic analysis revealed that the staphylococci, streptococci, and enterococci possess genes predicted to encode all of the enzymes of the mevalonate pathway and not the GAP-pyruvate pathway, unlike
Bacillus subtilis
and most gram-negative bacteria studied, which possess only components of the latter pathway. Phylogenetic and comparative genome analyses suggest that the genes for mevalonate biosynthesis in gram-positive cocci, which are highly divergent from those of mammals, were horizontally transferred from a primitive eukaryotic cell. Enterococci uniquely encode a bifunctional protein predicted to possess both 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase and acetyl-CoA acetyltransferase activities. Genetic disruption experiments have shown that five genes encoding proteins involved in this pathway (HMG-CoA synthase, HMG-CoA reductase, mevalonate kinase, phosphomevalonate kinase, and mevalonate diphosphate decarboxylase) are essential for the in vitro growth of
Streptococcus pneumoniae
under standard conditions. Allelic replacement of the HMG-CoA synthase gene rendered the organism auxotrophic for mevalonate and severely attenuated in a murine respiratory tract infection model. The mevalonate pathway thus represents a potential antibacterial target in the low-G+C gram-positive cocci.
A Protease-Resistant Catalase, KatA, Released upon Cell Lysis during Stationary Phase Is Essential for Aerobic Survival of a
Pseudomonas aeruginosa oxyR
Mutant at Low Cell Densities
Authors: Hassett Daniel J. , Alsabbagh Eyad , Parvatiyar Kislay , Howell Michael L. , Wilmott Robert W. , Ochsner Urs A. 
Published: July 2002

ABSTRACT

A
Pseudomonas aeruginosa oxyR
mutant was dramatically sensitive to H
2
O
2
, despite possessing wild-type catalase activity. Oxygen-dependent
oxyR
phenotypes also included an inability to survive aerobic serial dilution in Luria broth and to resist aminoglycosides. Plating the
oxyR
mutant after serial dilution in its own spent culture supernatant, which contained the major catalase KatA, or under anaerobic conditions allowed for survival. KatA was resistant to sodium dodecyl sulfate, proteinase K, pepsin, trypsin, chymotrypsin and the neutrophil protease cathepsin G. When provided in
trans
and expressed constitutively, the OxyR-regulated genes
katB
,
ahpB
, and
ahpCF
could not restore both the serial dilution defect and H
2
O
2
resistance; only
oxyR
itself could do so. The aerobic dilution defect could be complemented, in part, by only
ahpB
and
ahpCF
, suggesting that the latter gene products could possess a catalase-like activity. Aerobic Luria broth was found to generate ∼1.2 μM H
2
O
2
min
−1
via autoxidation, a level sufficient to kill serially diluted
oxyR
and
oxyR katA
bacteria and explain the molecular mechanism behind the aerobic serial dilution defect. Taken together, our results indicate that inactivation of OxyR renders
P. aeruginosa
exquisitely sensitive to both H
2
O
2
and aminoglycosides, which are clinically and environmentally important antimicrobials.
Chitin Synthesis in a
gas1
Mutant of
Saccharomyces cerevisiae
Authors: Valdivieso M-Henar , Ferrario Laura , Vai Marina , Duran Angel , Popolo Laura 
Published: July 2002

ABSTRACT

The existence of a compensatory mechanism in response to cell wall damage has been proposed in yeast cells. The increase of chitin accumulation is part of this response. In order to study the mechanism of the stress-related chitin synthesis, we tested chitin synthase I (CSI), CSII, and CSIII in vitro activities in the cell-wall-defective mutant
gas1
Δ. CSI activity increased twofold with respect to the control, a finding in agreement with an increase in the expression of the
CHS1
gene. However, deletion of the
CHS1
gene did not affect the phenotype of the
gas1
Δ mutant and only slightly reduced the chitin content. Interestingly, in
chs1 gas1
double mutants the lysed-bud phenotype, typical of
chs1
null mutant, was suppressed, although in
gas1
cells there was no reduction in chitinase activity.
CHS3
expression was not affected in the
gas1
mutant. Deletion of the
CHS3
gene severely compromised the phenotype of
gas1
cells, despite the fact that CSIII activity, assayed in membrane fractions, did not change. Furthermore, in
chs3 gas1
cells the chitin level was about 10% that of
gas1
cells. Thus, CSIII is the enzyme responsible for the hyperaccumulation of chitin in response to cell wall stress. However, the level of enzyme or the in vitro CSIII activity does not change. This result suggests that an interaction with a regulatory molecule or a posttranslational modification, which is not preserved during membrane fractionation, could be essential in vivo for the stress-induced synthesis of chitin.
Lantibiotic Biosynthesis: Interactions between Prelacticin 481 and Its Putative Modification Enzyme, LctM
Authors: Uguen Patricia , Le Pennec Jean-Paul , Dufour Alain 
Published: July 2002

ABSTRACT
Class AII and AIII lantibiotics and mersacidin are antibacterial peptides containing unusual residues obtained by posttranslational modifications of prepeptides, presumably catalyzed by LanM. LctM, the LanM for lacticin 481, is essential for the production of this class AII lantibiotic. Using the yeast two-hybrid system, we showed direct contact between the prelacticin 481 and LctM, supporting the proposed LctM function. Sixteen domains are conserved between the 10 known LanM proteins, whereas three additional domains were found only in class AII LanM proteins and in MrsM, the LanM for mersacidin. All the truncated LctM proteins that we tested presented impaired LctA-binding activity.
Identification in
Listeria monocytogenes
of MecA, a Homologue of the
Bacillus subtilis
Competence Regulatory Protein
Authors: Borezee Elise , Msadek Tarek , Durant Lionel , Berche Patrick 
Published: July 2002

ABSTRACT

We identified in
Listeria monocytogenes
a gene encoding a protein homologous to MecA, a regulatory protein acting with ClpC and ComK in the competence pathway of
Bacillus subtilis
. In
L. monocytogenes
, MecA is involved, along with ClpC and ClpP, in the downregulation of a 64-kDa secreted protein. In
B. subtilis
, the MecA protein of
L. monocytogenes
behaves as a regulatory protein, controlling the transcription of
comK
and
comG
. Complete or disrupted ComK homologues were also found in
L. monocytogenes
. However, we failed to detect competence in various strains of
L. monocytogenes
, including those with intact ComK. Our results suggest that the functions of MecA in the saprophytes
L. monocytogenes
and
B. subtilis
have presumably diverged in response to their respective ecological niches.
Regulation of Ferritin-Mediated Cytoplasmic Iron Storage by the Ferric Uptake Regulator Homolog (Fur) of
Helicobacter pylori
Authors: Bereswill Stefan , Greiner Stefan , van Vliet Arnoud H. M. , Waidner Barbara , Fassbinder Frank , Schiltz Emile , Kusters Johannes G. , Kist Manfred 
Published: July 2002

ABSTRACT

Homologs of the ferric uptake regulator Fur and the iron storage protein ferritin play a central role in maintaining iron homeostasis in bacteria. The gastric pathogen
Helicobacter pylori
contains an iron-induced prokaryotic ferritin (Pfr) which has been shown to be involved in protection against metal toxicity and a Fur homolog which has not been functionally characterized in
H. pylori
. Analysis of an isogenic
fur
-negative mutant revealed that
H. pylori
Fur is required for metal-dependent regulation of ferritin. Iron starvation, as well as medium supplementation with nickel, zinc, copper, and manganese at nontoxic concentrations, repressed synthesis of ferritin in the wild-type strain but not in the
H. pylori fur
mutant. Fur-mediated regulation of ferritin synthesis occurs at the mRNA level. With respect to the regulation of ferritin expression, Fur behaves like a global metal-dependent repressor which is activated under iron-restricted conditions but also responds to different metals. Downregulation of ferritin expression by Fur might secure the availability of free iron in the cytoplasm, especially if iron is scarce or titrated out by other metals.
The Bulged Nucleotide in the
Escherichia coli
Minimal Selenocysteine Insertion Sequence Participates in Interaction with SelB: a Genetic Approach
Authors: Li Chuang , Reches Myriam , Engelberg-Kulka Hanna 
Published: July 2002

ABSTRACT

The UGA codon, which usually acts as a stop codon, can also direct the incorporation into a protein of the amino acid selenocysteine. This UGA decoding process requires a
cis
-acting mRNA element called the selenocysteine insertion sequence (SECIS), which can form a stem-loop structure. In
Escherichia coli
, selenocysteine incorporation requires only the 17-nucleotide-long upper stem-loop structure of the
fdhF
SECIS. This structure carries a bulged nucleotide U at position 17. Here we asked whether the single bulged nucleotide located in the upper stem-loop structure of the
E. coli fdhF
SECIS is involved in the in vivo interaction with SelB. We used a genetic approach, generating and characterizing
selB
mutations that suppress mutations of the bulged nucleotide in the SECIS. All the
selB
suppressor mutations isolated were clustered in a region corresponding to 28 amino acids in the SelB C-terminal subdomain 4b. These
selB
suppressor mutations were also found to suppress mutations in either the loop or the upper stem of the
E. coli
SECIS. Thus, the
E. coli
SECIS upper stem-loop structure can be considered a “single suppressible unit,” suggesting that there is some flexibility to the nature of the interaction between this element and SelB.