bluuebunny/crossref_metadata_2025_split huggingface dataset:
Interleukin-4 Is Essential for the Control of Microfilariae in Murine Infection with the FilariaLitomosoides sigmodontis
Authors: Volkmann Lars , Saeftel Michael , Bain Odile , Fischer Kerstin , Fleischer Bernhard , Hoerauf Achim 
Published: July 2002

ABSTRACTLitomosoides sigmodontisis the only filaria which develops from infective larvae into microfilaria-producing adults in immunocompetent laboratory mice. In this study we report that interleukin-4 knockout (IL-4 KO) mice have an up to 100-fold-higher and a significantly prolonged microfilaremia compared to wild-type BALB/c mice, as well as 20 times more microfilariae in the thoracic cavity, the site of infection. While worm development and adult worm persistence were equivalent in IL-4 KO and wild-type mice, the fertility and length of adult female worms in IL-4 KO mice was clearly enhanced. The high susceptibility to microfilariae in IL-4 KO mice required the presence of adult worms in a full infection cycle since microfilariae loads did not differ much between IL-4 KO and wild-type mice when purified microfilariae were injected into mice. In addition, we found that eosinophilia was diminished and immunoglobulin E (IgE) was absent in IL-4 KO mice. IgE, however, does not seem to be the essential factor for microfilarial containment since microfilaremia was not elevated in B-cell KO mice. In conclusion, IL-4 is shown for the first time to be essential for the control of microfilarial loads but not of adult worm loads in a fully permissive murine filarial infection. IL-4 dependent effector pathways seem to operate on adult worms rather than directly on microfilariae.
Gram-Positive and Gram-Negative Bacteria Do Not Trigger Monocytic Cytokine Production through Similar Intracellular Pathways
Authors: Rabehi Lila , Irinopoulou Théano , Cholley Béatrice , Haeffner-Cavaillon Nicole , Carreno Marie-Paule 
Published: July 2002

ABSTRACTToll-like receptors (TLRs) are involved in human monocyte activation by lipopolysaccharide (LPS) andStaphylococcus aureusCowan (SAC), suggesting that gram-positive and gram-negative bacteria may trigger similar intracellular events. Treatment with specific kinase inhibitors prior to cell stimulation dramatically decreased LPS-induced cytokine production. Blocking of the p38 pathway prior to LPS stimulation decreased interleukin-1α (IL-1α), IL-1ra, and tumor necrosis factor alpha (TNF-α) production, whereas blocking of the ERK1/2 pathways inhibited IL-1α, IL-1β, and IL-1ra but not TNF-α production. When cells were stimulated by SAC, inhibition of the p38 pathway did not affect cytokine production, whereas only IL-1α production was decreased in the presence of ERK kinase inhibitor. We also demonstrated that although LPS and SAC have been shown to bind to CD14 before transmitting signals to TLR4 and TLR2, respectively, internalization of CD14 occurred only in monocytes triggered by LPS. Pretreatment of the cells with SB203580, U0126, or a mixture of both inhibitors did not affect internalization of CD14. Altogether, these results suggest that TLR2 signaling does not involve p38 mitogen-activated protein kinase signaling pathways, indicating that divergent pathways are triggered by gram-positive and gram-negative bacteria, thereby inducing cytokine production.
Rgg Influences the Expression of Multiple Regulatory Loci To Coregulate Virulence Factor Expression in
Streptococcus pyogenes
Authors: Chaussee Michael S. , Sylva Gail L. , Sturdevant Daniel E. , Smoot Laura M. , Graham Morag R. , Watson Robert O. , Musser James M. 
Published: July 2002

ABSTRACT

The human pathogen
Streptococcus pyogenes
secretes many proteins to the cell wall and extracellular environment that contribute to virulence. Rgg regulates the expression of several exoproteins including a cysteine protease (SPE B), a nuclease (MF-1), a putative nuclease (MF-3), and autolysin. The functional heterogeneity of Rgg-regulated exoproteins and the lack of a conserved regulatory motif in the promoter regions of the genes suggested that Rgg interacts with additional regulatory networks to influence gene expression. DNA microarrays were used to test this hypothesis by comparing genomewide transcript profiles of
S. pyogenes
NZ131 and isogenic derivative NZ131
rgg
during the exponential phase of growth. Transcripts of known and putative virulence-associated genes were more abundant in the
rgg
mutant, including
emm
,
scpA
,
orfX
,
scl1
,
hasAB
,
slo
,
sagA
,
ska
,
speH
,
grab
,
mac
,
mf-1
, and
mf-3
. Increased transcription of
emm
,
scpA
, and
orfX
in the
rgg
mutant was associated with increased production of the corresponding proteins. Differences in the expression of virulence-associated genes were associated with changes in the expression of several regulatory genes, including
mga
,
sagA
,
csrRS
, and
fasBCA
. The results show that Rgg influences the expression of multiple regulatory networks to coregulate virulence factor expression in
S. pyogenes
.
Binding Component of
Clostridium perfringens
Iota-Toxin Induces Endocytosis in Vero Cells
Authors: Nagahama Masahiro , Nagayasu Koichi , Kobayashi Keiko , Sakurai Jun 
Published: July 2002

ABSTRACT

Clostridium perfringens
iota-toxin is a binary toxin consisting of two individual proteins, the binding component (Ib) and the enzyme component (Ia). Wild-type Ib bound to Vero cells at 4 and 37°C and formed oligomers at 37°C but not at 4°C. The Ib-induced K
+
release from the cells was dependent on the oligomer formation of Ib in the cells, but the oligomer formation did not induce rounding activity or cytotoxicity. After incubation of the cells with recombinant Ib (rIb) at 37°C, the Ib oligomer in the cell became resistant to pronase treatment with time, but the Ib monomer was sensitive to the treatment. Furthermore, treatment of Vero cells with rIb in the presence of bafilomycin, methylamine, or ethylamine resulted in accumulation of the oligomer in the cells but had no effect on K
+
release. Moreover, incubation with Ib plus Ia in the presence of these agents caused no rounding in the cells. These observations suggest that Ib binds to Vero cells, itself oligomerizing to form ion-permeable channels and that the formation of oligomer then induces endocytosis.
Intimin Facilitates Colonization byEscherichia coliO157:H7 in Adult Ruminants
Authors: Cornick Nancy A. , Booher Sheridan L. , Moon Harley W. 
Published: July 2002

ABSTRACTWe compared the magnitude and duration of fecal shedding of wild-typeEscherichia coliO157:H7 to that of an isogenic intimin mutant in young adult cattle and sheep. In both ruminant species, wild-typeE. coliO157:H7 was shed in greater numbers and for a longer duration than was the intimin mutant.
Essential Role for Cyclic AMP and Its Receptor Protein in
Yersinia enterocolitica
Virulence
Authors: Petersen Shane , Young Glenn M. 
Published: July 2002

ABSTRACT

Insertion mutations were isolated in
cya
and
crp
of
Yersinia enterocolitica
, which encode adenylate cyclase and the cyclic AMP (cAMP) receptor protein (CRP). The
cya
and
crp
mutants were affected for the production of proteins exported by the Ysc, Ysa, and flagellar type III secretion systems (TTSS). Protein production by each TTSS was restored when the respective mutation was complemented by a plasmid-encoded copy of the wild-type gene. Both
cya
and
crp
mutants exhibited reduced virulence for orally infected BALB/c mice in a 50% lethal dose analysis. Examination of bacterial survival in host tissues showed that
cya
and
crp
mutants colonized Peyer's patches and, to a lesser extent, mesenteric lymph nodes. However, the mutants did not appear to disseminate to the liver and spleen of infected mice. An initial examination of the effectiveness of
Y. enterocolitica cya
and
crp
mutants to stimulate protective immunity against subsequent challenge with virulent bacteria in mice was promising. The results indicate that the cAMP-CRP regulatory system is required for
Y. enterocolitica
virulence.
Molecular Cloning of a Vaccine Antigen against Infection with the Larval Stage of
Echinococcus multilocularis
Authors: Gauci Charles , Merli Michael , Muller Volker , Chow Conan , Yagi Kinpei , Mackenstedt Ute , Lightowlers Marshall W. 
Published: July 2002

ABSTRACT

Alveolar and cystic hydatidosis are caused by infection with the larval stages of
Echinococcus multilocularis
and
Echinococcus granulosus
, respectively. A host-protective antigen has been identified in
E. granulosus
. Here we identify the presence of a closely related protein
in E. multilocularis
, characterize and express a cDNA encoding the antigen (designated EM95), determine the structure of the
em
95 gene, and demonstrate that the EM95 recombinant protein can be used to induce significant levels of protection against challenge infection with
E. multilocularis
eggs in mice.
Regulation of Acetyl Coenzyme A Synthetase in
Escherichia coli
Authors: Kumari Suman , Beatty Christine M. , Browning Douglas F. , Busby Stephen J. W. , Simel Erica J. , Hovel-Miner Galadriel , Wolfe Alan J. 
Published: July 2002

ABSTRACT

Cells of
Escherichia coli
growing on sugars that result in catabolite repression or amino acids that feed into glycolysis undergo a metabolic switch associated with the production and utilization of acetate. As they divide exponentially, these cells excrete acetate via the phosphotransacetylase-acetate kinase pathway. As they begin the transition to stationary phase, they instead resorb acetate, activate it to acetyl coenzyme A (acetyl-CoA) by means of the enzyme acetyl-CoA synthetase (Acs) and utilize it to generate energy and biosynthetic components via the tricarboxylic acid cycle and the glyoxylate shunt, respectively. Here, we present evidence that this switch occurs primarily through the induction of
acs
and that the timing and magnitude of this induction depend, in part, on the direct action of the carbon regulator cyclic AMP receptor protein (CRP) and the oxygen regulator FNR. It also depends, probably indirectly, upon the glyoxylate shunt repressor IclR, its activator FadR, and many enzymes involved in acetate metabolism. On the basis of these results, we propose that cells induce
acs
, and thus their ability to assimilate acetate, in response to rising cyclic AMP levels, falling oxygen partial pressure, and the flux of carbon through acetate-associated pathways.
Role of FliJ in Flagellar Protein Export in
Salmonella
Authors: Minamino Tohru , Chu Ryan , Yamaguchi Shigeru , Macnab Robert M. 
Published: July 2002

ABSTRACT

We isolated and characterized spontaneous mutants with defects in the 147-amino-acid
Salmonella
protein FliJ, which is a cytoplasmic component of the type III flagellar export apparatus. These mutants, including ones with null mutations, have the ability to form swarms on motility agar plates after prolonged incubation at 30°C; i.e., they display a leaky motile phenotype. One mutant, SJW277, which formed significantly bigger swarms than the others, encoded only the N-terminal 73 amino acids of FliJ, one-half of the protein. At 30°C, overproduction of this mutant protein improved, to wild-type levels, both motility and the ability to export both rod/hook-type (FlgD; hook capping protein) and filament-type (FliC; flagellin) substrates. At 42°C, however, export was inhibited, indicating that the mutant FliJ protein was temperature sensitive. Taking advantage of this, we performed temperature upshift experiments, which demonstrated that FliJ is directly required for the export of FliC. Co-overproduction of FliJ and either of two export substrates, FliE or FlgG, hindered their aggregation in the cytoplasm. We conclude that FliJ is a general component of the flagellar export apparatus and has a chaperone-like activity for both rod/hook-type and filament-type substrates.
Developmental Control of Stress Stimulons in
Streptomyces coelicolor
Revealed by Statistical Analyses of Global Gene Expression Patterns
Authors: Vohradsky J. , Li X.-M. , Dale G. , Folcher M. , Nguyen L. , Viollier P. H. , Thompson C. J. 
Published: July 2002

ABSTRACT

Stress-induced regulatory networks coordinated with a procaryotic developmental program were revealed by two-dimensional gel analyses of global gene expression. Four developmental stages were identified by their distinctive protein synthesis patterns using principal component analysis. Statistical analyses focused on five stress stimulons (induced by heat, cold, salt, ethanol, or antibiotic shock) and their synthesis during development. Unlike other bacteria, for which various stresses induce expression of similar sets of protein spots, in
Streptomyces coelicolor
heat, salt, and ethanol stimulons were composed of independent sets of proteins. This suggested independent control by different physiological stress signals and their corresponding regulatory systems. These stress proteins were also under developmental control. Cluster analysis of stress protein synthesis profiles identified 10 different developmental patterns or “synexpression groups.” Proteins induced by cold, heat, or salt shock were enriched in three developmental synexpression groups. In addition, certain proteins belonging to the heat and salt shock stimulons were coregulated during development. Thus, stress regulatory systems controlling these stimulons were implicated as integral parts of the developmental program. This correlation suggested that thermal shock and salt shock stress response regulatory systems either allow the cell to adapt to stresses associated with development or directly control the developmental program.
Multiprobe RNase Protection Assay Analysis of mRNA Levels for the
Escherichia coli
Oxidative DNA Glycosylase Genes under Conditions of Oxidative Stress
Authors: Gifford Christine M. , Blaisdell Jeffrey O. , Wallace Susan S. 
Published: July 2002

ABSTRACT

Escherichia coli
formamidopyrimidine DNA glycosylase (Fpg), MutY DNA glycosylase, endonuclease VIII, and endonuclease III are oxidative base excision repair DNA glycosylases that remove oxidized bases from DNA, or an incorrect base paired with an oxidized base in the case of MutY. Since genes encoding other base excision repair proteins have been shown to be part of adaptive responses in
E. coli
, we wanted to determine whether the oxidative DNA glycosylase genes are induced in response to conditions that cause the type of damage their encoded proteins remove. The genes
fpg
,
mutY
,
nei
, and
nth
encode Fpg, MutY, endonuclease VIII, and endonuclease III, respectively. Multiprobe RNase protection assays were used to examine the transcript levels of these genes under conditions that induce the SoxRS, OxyR, and SOS regulons after a shift from anaerobic to aerobic growth and at different stages along the growth curve. Transcript levels for all four genes decreased as cells progressed from log-phase growth to stationary phase and increased after cells were shifted from anaerobic to aerobic growth. None of the genes were induced by hydrogen peroxide, paraquat, X rays, or conditions that induce the SOS response.
Mutational Analysis of a Role for Salicylic Acid in Iron Metabolism of
Mycobacterium smegmatis
Authors: Adilakshmi Tadepalli , Ayling Peter D. , Ratledge Colin 
Published: July 2002

ABSTRACT

The role of salicylic acid in iron metabolism was examined in two wild-type strains (mc
2
155 and NCIMB 8548) and three mutant strains (mc
2
1292 [lacking exochelin], SM3 [lacking iron-dependent repressor protein IdeR] and S99 [a salicylate-requiring auxotroph derived in this study]) of
Mycobacterium smegmatis
. Synthesis of salicylate in SM3 was derepressed even in the presence of iron, as was synthesis of the siderophores exochelin, mycobactin, and carboxymycobactin. S99 was dependent on salicylate for growth and failed to grow with the three ferrisiderophores, suggesting that salicylate fulfills an additional function(s) other than being a precursor of mycobactin and carboxymycobactin. Salicylic acid at 100 μg/ml repressed the formation of a 29-kDa cell envelope protein (putative exochelin receptor protein) in S99 grown both iron deficiently and iron sufficiently. In contrast, synthesis of this protein was affected only under iron-limited conditions in the parent strain, mc
2
155, and remained unaltered in SM3, suggesting an interaction between the IdeR protein and salicylate. Thus, salicylate may also function as a signal molecule for recognition of cellular iron status. Growth of all strains and mutants with
p
-aminosalicylate (PAS) at 100 μg/ml increased salicylate accumulation between three- and eightfold under both iron-limited and iron-sufficient growth conditions and decreased mycobactin accumulation by 40 to 80% but increased carboxymycobactin accumulation by 50 to 55%. Thus, although PAS inhibited salicylate conversion to mycobactin, presumptively by blocking salicylate AMP kinase, PAS also interferes with the additional functions of salicylate, as its effect was heightened in S99 when the salicylate concentration was minimal.
ssgA
Is Essential for Sporulation of
Streptomyces coelicolor
A3(2) and Affects Hyphal Development by Stimulating Septum Formation
Authors: van Wezel Gilles P. , van der Meulen Jannes , Kawamoto Shinichi , Luiten Ruud G. M. , Koerten Henk K. , Kraal Barend 
Published: July 2002

ABSTRACT

The role of
ssgA
in cell division and development of streptomycetes was analyzed. An
ssgA
null mutant of
Streptomyces coelicolor
produced aerial hyphae but failed to sporulate, and
ssgA
can therefore be regarded as a novel
whi
gene. In addition to the morphological changes, antibiotic production was also disturbed, with strongly reduced actinorhodin production. These defects could be complemented by plasmid-borne
ssgA
. In the wild-type strain, transcription of
ssgA
was induced by nutritional shift-down and was shown to be linked to that of the upstream-located gene
ssgR
, which belongs to the family of
iclR
-type transcriptional regulator genes. Analysis of mycelium harvested from liquid-grown cultures by transmission electron microscopy showed that septum formation had strongly increased in
ssgA
-overexpressing strains in comparison to wild-type
S. coelicolor
and that spore-like compartments were produced at high frequency. Furthermore, the hyphae were significantly wider and contained irregular and often extremely thick septa. These data underline the important role for
ssgA
in
Streptomyces
cell division.
Null Mutation of thedamorseqAGene Suppresses Temperature-Sensitive Lethality but Not Hypersensitivity to Novobiocin ofmukNull Mutants
Authors: Onogi Toshinari , Yamazoe Mitsuyoshi , Ichinose Chiyome , Niki Hironori , Hiraga Sota 
Published: July 2002

ABSTRACTEscherichia coli mukF, mukE, andmukBnull mutants have common phenotypes such as temperature-dependent colony formation, anucleate cell production, chromosome cutting by septum closure, and abnormal localization of SeqA-DNA clusters. We show here that the associatedmuknull mutations cause hypersensitivity to novobiocin. Null mutation of eitherdamorseqAsuppressed partially the temperature-sensitive lethality but failed to suppress the anucleate cell production and the hypersensitivity to novobiocin caused bymuknull mutations.
Identification by Genetic Suppression of
Escherichia coli
TolB Residues Important for TolB-Pal Interaction
Authors: Ray Marie-Céline , Germon Pierre , Vianney Anne , Portalier Raymond , Lazzaroni Jean Claude 
Published: July 2002

ABSTRACT

The Tol-Pal system of
Escherichia coli
is involved in maintaining outer membrane stability. Mutations in
tolQ
,
tolR
,
tolA
,
tolB
, or
pal
genes result in sensitivity to bile salts and the leakage of periplasmic proteins. Moreover, some of the
tol
genes are necessary for the entry of group A colicins and the DNA of filamentous bacteriophages. TolQ, TolR, and TolA are located in the cytoplasmic membrane where they interact with each other via their transmembrane domains. TolB and Pal form a periplasmic complex near the outer membrane. We used suppressor genetics to identify the regions important for the interaction between TolB and Pal. Intragenic suppressor mutations were characterized in a domain of Pal that was shown to be involved in interactions with TolB and peptidoglycan. Extragenic suppressor mutations were located in
tolB
gene. The C-terminal region of TolB predicted to adopt a β-propeller structure was shown to be responsible for the interaction of the protein with Pal. Unexpectedly, none of the suppressor mutations was able to restore a correct association between Pal and peptidoglycan, suggesting that interactions between Pal and other components such as TolB may also be important for outer membrane stability.
Fragmentation of 23S rRNA in Strains of
Proteus
and
Providencia
Results from Intervening Sequences in the
rrn
(rRNA) Genes
Authors: Miller Wayne L. , Pabbaraju Kanti , Sanderson Kenneth E. 
Published: July 2002

ABSTRACT

Intervening sequences (IVSs) were originally identified in the
rrl
genes for 23S rRNA (
rrl
genes, for large ribosomal subunit, part of
rrn
operon encoding rRNA) of
Salmonella enterica
serovars Typhimurium LT2 and Arizonae. These sequences are transcribed but later removed during RNase III processing of the rRNA, resulting in fragmentation of the 23S species; IVSs are uncommon, but have been reported in at least 10 bacterial genera. Through PCR amplification of IVS-containing regions of the
rrl
genes we showed that most
Proteus
and
Providencia
strains contain IVSs similar to those of serovar Typhimurium in distribution and location in
rrl
genes. By extraction and Northern blotting of rRNA, we also found that these IVSs result in rRNA fragmentation. We report the first finding of two very different sizes of IVS (113 bp and 183 to 187 bp) in different
rrl
genes in the same strain, in helix 25 of
Proteus
and
Providencia
spp.; IVSs from helix 45 are 113 to 123 bp in size. Analysis of IVS sequence and postulated secondary structure reveals striking similarities of
Proteus
and
Providencia
IVSs to those of serovar Typhimurium, with the stems of the smaller IVSs from helix 25 being similar to those of
Salmonella
helix 25 IVSs and with both the stem and the central loop domain of helix 45 IVSs being similar. Thus, IVSs of related sequences are widely distributed throughout the
Enterobacteriaceae
, in
Salmonella
,
Yersinia
,
Proteus
, and
Providencia
spp., but we did not find them in
Escherichia coli
,
Citrobacter
,
Enterobacter
,
Klebsiella
, or
Morganella
spp.; the sporadic distribution of IVSs of related sequence indicates that lateral genetic transfer has occurred.
Respiration of 2,4,6-Trinitrotoluene by
Pseudomonas
sp. Strain JLR11
Authors: Esteve-Nuñez Abraham , Lucchesi Gloria , Philipp Bodo , Schink Bernhard , Ramos Juan L. 
Published: July 2002

ABSTRACT

Under anoxic conditions
Pseudomonas
sp. strain JLR11 can use 2,4,6-trinitrotoluene (TNT) as the sole N source, releasing nitrite from the aromatic ring and subsequently reducing it to ammonium and incorporating it into C skeletons. This study shows that TNT can also be used as a terminal electron acceptor in respiratory chains under anoxic conditions by
Pseudomonas
sp. strain JLR11. TNT-dependent proton translocation coupled to the reduction of TNT to aminonitrotoluenes has been observed in TNT-grown cells. This extrusion did not occur in nitrate-grown cells or in anaerobic TNT-grown cells treated with cyanide, a respiratory chain inhibitor. We have shown that in a membrane fraction prepared from
Pseudomonas
sp. strain JLR11 grown on TNT under anaerobic conditions, the synthesis of ATP was coupled to the oxidation of molecular hydrogen and to the reduction of TNT. This phosphorylation was uncoupled by gramicidin. Respiration by
Pseudomonas
sp. strain JLR11 is potentially useful for the biotreatment of TNT in polluted waters and soils, particularly in phytorhizoremediation, in which bacterial cells are transported to the deepest root zones, which are poor in oxygen.