bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Genes in an Extraintestinal Isolate of
Escherichia coli
with Increased Expression after Exposure to Human Urine
Authors: Russo Thomas A. , Carlino Ulrike B. , Mong Andrew , Jodush Stephen T. 
Published: December 2019

ABSTRACT

The identification of genes with increased expression in vivo may lead to the identification of novel or unrecognized virulence traits and/or recognition of environmental signals involved in modulating gene expression. Our laboratory is studying an extraintestinal isolate of
Escherichia coli
as a model pathogen. We had previously used human urine ex vivo to identify the unrecognized urovirulence genes
guaA
and
argC
and to establish that arginine and guanine (or derivatives) were limiting in this body fluid (T. A. Russo et al., Mol. Microbiol. 22:217–229, 1996). In this study, we have continued with this approach and identified three additional genes that have increased expression in human urine relative to Luria-Bertani (LB) medium. Expression of
ure1
(urine-responsive element) is increased a mean of 47.6-fold in urine but completely suppressed by exogenous glucose. This finding suggests that
ure1
is regulated by catabolite repression and that limiting glucose in urine is a regulatory signal.
ure1
is present in the
E. coli
K-12 genome, but its function is unknown. Although disruption of
ure1
results in diminished growth in human urine, limiting concentrations of amino acids, nucleosides, or iron (Fe), or changes in osmolarity or pH do not affect the expression of
ure1
. Therefore, Ure1 appears to have a role independent of the synthesis or uptake of these nutrients and does not appear to be involved in osmoprotection.
iroN

E. coli

is a novel
E. coli
gene with 77% DNA homology to a catecholate siderophore receptor gene recently identified in
Salmonella
. Its expression is increased a mean of 27.2-fold in urine and is repressed by exogenous Fe and a urinary pH of 5.0. This finding supports the contention that Fe is a limiting element in urine and that alteration of pH can affect gene expression. It is linked to the P-pilus (
prs
) and F1C fimbrial (
foc
) gene clusters on a pathogenicity island and appears to have been acquired by IS
1230
-mediated horizontal transmission. The homologous

iroN
E. coli

sequence is significantly more prevalent in urinary tract and blood isolates of
E. coli
compared to fecal isolates. Last, the expression of ArtJ, an arginine periplasmic binding protein, is increased a mean of 16.6-fold in urine. This finding implicates arginine concentrations as limited in urine and, in combination with previous data demonstrating that
argC
is important for urovirulence, suggests that the ability of
E. coli
to synthesize or acquire arginine is important for urovirulence.
ure1
,

iroN
E. coli

, and
artJ
all have increased expression in human blood and ascites relative to LB medium as well. The identification of these genes increases our understanding of regulatory signals present in human urine, blood, and ascites. Ure1, IroN

E. coli

, and ArtJ also warrant further evaluation as virulence traits both within and outside the urinary tract.
Phase Variation in
Helicobacter pylori
Lipopolysaccharide due to Changes in the Lengths of Poly(C) Tracts in α3-Fucosyltransferase Genes
Authors: Appelmelk Ben J. , Martin Steve L. , Monteiro Mario A. , Clayton Chris A. , McColm Andrew A. , Zheng Pengyuan , Verboom Theo , Maaskant Janneke J. , van den Eijnden Dirk H. , Hokke Cornelis H. , Perry Malcolm B. , Vandenbroucke-Grauls Christina M. J. E. , Kusters Johannes G. 
Published: December 2019

ABSTRACT

The lipopolysaccharide (LPS) of
Helicobacter pylori
expresses the Lewis x (Le
x
) and/or Le
y
antigen. We have shown previously that
H. pylori
LPS displays phase variation whereby an Le
x
-positive strain yields variants with different LPS serotypes, for example, Le
x
plus Le
y
or nonfucosylated polylactosamine.
H. pylori
has two α3-fucosyltransferase genes that both contain poly(C) tracts. We now demonstrate that these tracts can shorten or lengthen randomly, which results in reversible frameshifting and inactivation of the gene products. We provide genetic and serological evidence that this mechanism causes
H. pylori
LPS phase variation and demonstrate that the on or off status of α3-fucosyltransferase genes determines the LPS serotypes of phase variants and clinical isolates. The role of the α3-fucosyltransferase gene products in determining the LPS serotype was confirmed by structural-chemical analysis of α3-fucosyltransferase knockout mutants. The data also show that the two α3-fucosyltransferase genes code for enzymes with different fine specificities, and we propose the names
futA
and
futB
to designate the orthologs of the
H. pylori
26695 α3-fucosyltransferase genes HP0379 and HP0651, respectively. The data also show that the α3-fucosylation in
H. pylori
precedes α3-fucosyltransferase, an order of events opposite to that which prevails in mammals. Finally, the data provide an understanding at the molecular level of the mechanisms underlying LPS diversity in
H. pylori
, which may play an important role in adaptation to the host.
Redox Imbalance Differentially Inhibits Lipopolysaccharide-Induced Macrophage Activation in the Mouse Liver
Authors: Wang Fuan , Wang Luke Y. , Wright Douglas , Parmely Michael J. 
Published: December 2019

ABSTRACTEndotoxemia is accompanied by significant changes in the reductive-oxidative (redox) balance of critical target organs. Redox stress has been shown to regulate the expression of proinflammatory genes that are induced by endotoxic lipopolysaccharide (LPS) in vitro; however, much less is known about the effects of redox imbalance on LPS-induced gene expression in vivo. To assess the effects of redox stress on inflammatory responses in endotoxemia, mice were treated with either diethyl maleate (DEM), a glutathione-depleting agent, or buthionine sulfoximine (BSO), an inhibitor of glutathione synthesis, and challenged with LPS. While serum tumor necrosis alpha (TNF-α) responses and the appearance of TNF-α-positive Kupffer cells in the liver were virtually eliminated by DEM or BSO treatment, the expression of both CD14 and inducible NO synthase (iNOS) by Kupffer cells was unaffected by glutathione depletion. By contrast, LPS-induced hepatocyte and hepatic sinusoidal endothelial cell iNOS expression was significantly inhibited in DEM-treated mice. Hepatocyte iNOS induced by recombinant mouse TNF-α was also inhibited by DEM treatment. These results indicate that the effects of oxidative stress in this organ are cell type specific and suggest that both the production and the action of TNF-α are substantially influenced by the redox state of the liver during endotoxemia.
The Intercellular Adhesion (
ica
) Locus Is Present in
Staphylococcus aureus
and Is Required for Biofilm Formation
Authors: Cramton Sarah E. , Gerke Christiane , Schnell Norbert F. , Nichols Wright W. , Götz Friedrich 
Published: December 2019

ABSTRACT

Nosocomial infections that result in the formation of biofilms on the surfaces of biomedical implants are a leading cause of sepsis and are often associated with colonization of the implants by
Staphylococcus epidermidis
. Biofilm formation is thought to require two sequential steps: adhesion of cells to a solid substrate followed by cell-cell adhesion, creating multiple layers of cells. Intercellular adhesion requires the polysaccharide intercellular adhesin (PIA), which is composed of linear β-1,6-linked glucosaminylglycans and can be synthesized in vitro from UDP-
N
-acetylglucosamine by products of the intercellular adhesion (
ica
) locus. We have investigated a variety of
Staphylococcus aureus
strains and find that all strains tested contain the
ica
locus and that several can form biofilms in vitro. Sequence comparison with the
S. epidermidis ica
genes revealed 59 to 78% amino acid identity. Deletion of the
ica
locus results in a loss of the ability to form biofilms, produce PIA, or mediate
N
-acetylglucosaminyltransferase activity in vitro. Cross-species hybridization experiments revealed the presence of
icaA
in several other
Staphylococcus
species, suggesting that cell-cell adhesion and the potential to form biofilms is conserved within this genus.
Characterization of Pic, a Secreted Protease of
Shigella flexneri
and Enteroaggregative
Escherichia coli
Authors: Henderson Ian R. , Czeczulin John , Eslava Carlos , Noriega Fernando , Nataro James P. 
Published: December 2019

ABSTRACT

We have identified and characterized a secreted protein, designated Pic, which is encoded on the chromosomes of enteroaggregative
Escherichia coli
(EAEC) 042 and
Shigella flexneri
2457T. The product of the
pic
gene is synthesized as a 146.5-kDa precursor molecule which is processed at the N and C termini during secretion, allowing the release of a mature protein (109.8 kDa) into the culture supernatant. The deduced amino acid sequence of Pic shows high homology to autotransporter proteins, particularly a subgroup termed the SPATEs (serine protease autotransporters of the
Enterobacteriaceae
). Present in all members of this subgroup is a motif similar to the active sites of certain serine proteases. Pic catalyzes gelatin degradation, which can be abolished by disruption of the predicted proteolytic active site. Functional analysis of the Pic protein implicates this factor in mucinase activity, serum resistance, and hemagglutination. Our data suggest that Pic may be a multifunctional protein involved in enteric pathogenesis.
Experimental Gonococcal Genital Tract Infection and Opacity Protein Expression in Estradiol-Treated Mice
Authors: Jerse Ann E. 
Published: December 2019

ABSTRACT

The development of effective prophylactic agents against gonorrhea and the study of adaptation by
Neisseria gonorrhoeae
to the urogenital mucosa are hindered by the lack of a well-established animal model of gonococcal genital tract infection. Here, a murine model of long-term gonococcal genital tract infection is described. Female BALB/c mice were treated with 17-β-estradiol and inoculated intravaginally with wild-type gonococcal strain FA1090 or MS11.
N. gonorrhoeae
was recovered from vaginal swabs for an average of 12 to 13 days following inoculation with 10
6
CFU of either strain. Inflammation occurred in over 80% of infected mice, and diplococci were associated with epithelial cells and neutrophils in stained vaginal smears. Ascended infection occurred in 17 to 20% of mice inoculated with strain FA1090. An outbred mouse strain (SLC:ddY) previously reported to be naturally susceptible to
N. gonorrhoeae
was also tested; however, as with BALB/c mice, estradiol was required for prolonged infection. Although piliation was not maintained during experimental murine infection, 46 to 100% of vaginal isolates from four of eight BALB/c mice and three of four SLC:ddY mice expressed one or more opacity (Opa) proteins within 4 days after inoculation with an Opa-negative variant of strain FA1090. The observed selection for and/or induction of gonococcal Opa protein expression during murine infection appears to parallel events that occur during experimental urethritis in volunteers.
Outer Membrane Protein A-Promoted Actin Condensation of Brain Microvascular Endothelial Cells Is Required for
Escherichia coli
Invasion
Authors: Prasadarao Nemani V. , Wass Carol A. , Stins Monique F. , Shimada Hiroyuki , Kim Kwang Sik 
Published: December 2019

ABSTRACT

Escherichia coli
is the most common gram-negative bacterium that causes meningitis during the neonatal period. We have previously shown that the entry of circulating
E. coli
organisms into the central nervous system is due to their ability to invade the blood-brain barrier, which is composed of a layer of brain microvascular endothelial cells (BMEC). In this report, we show by transmission electron microscopy that
E. coli
transmigrates through BMEC in an enclosed vacuole without intracellular multiplication. The microfilament-disrupting agents cytochalasin D and latrunculin A completely blocked
E. coli
invasion of BMEC. Cells treated with the microtubule inhibitors nocodazole, colchicine, vincristin, and vinblastine and the microtubule-stabilizing agent taxol also exhibited 50 to 60% inhibition of
E. coli
invasion. Confocal laser scanning fluorescence microscopy showed F-actin condensation associated with the invasive
E. coli
but no alterations in microtubule distribution. These results suggest that
E. coli
uses a microfilament-dependent phagocytosis-like endocytic mechanism for invasion of BMEC. Previously we showed that OmpA expression significantly enhances the
E. coli
invasion of BMEC. We therefore examined whether OmpA expression is related to the recruitment of F-actin. OmpA
+
E. coli
induced the accumulation of actin in BMEC to a level similar to that induced by the parental strain, whereas OmpA
−
E. coli
did not. Despite the presence of OmpA, a noninvasive
E. coli
isolate, however, did not show F-actin condensation. OmpA
+
-
E. coli
-associated condensation of F-actin was blocked by synthetic peptides corresponding to the N-terminal extracellular domains of OmpA as well as BMEC receptor analogues for OmpA, chitooligomers (GlcNAcβ1-4GlcNAc oligomers). These findings suggest that OmpA interaction is critical for the expression or modulation of other bacterial proteins that will subsequently cause actin accumulation for the uptake of bacteria.
Plasmodium falciparum
Field Isolates Commonly Use Erythrocyte Invasion Pathways That Are Independent of Sialic Acid Residues of Glycophorin A
Authors: Okoyeh Jude Nnaemeka , Pillai C. R. , Chitnis Chetan E. 
Published: December 2019

ABSTRACT

Erythrocyte invasion by malaria parasites is mediated by specific molecular interactions. Sialic acid residues of glycophorin A are used as invasion receptors by
Plasmodium falciparum
. In vitro invasion studies have demonstrated that some cloned
P. falciparum
lines can use alternate receptors independent of sialic acid residues of glycophorin A. It is not known if invasion by alternate pathways occurs commonly in the field. In this study, we used in vitro growth assays and erythrocyte invasion assays to determine the invasion phenotypes of 15
P. falciparum
field isolates. Of the 15 field isolates tested, 5 multiply in both neuraminidase and trypsin-treated erythrocytes, 3 multiply in neuraminidase-treated but not trypsin-treated erythrocytes, and 4 multiply in trypsin-treated but not neuraminidase-treated erythrocytes; 12 of the 15 field isolates tested use alternate invasion pathways that are not dependent on sialic acid residues of glycophorin A. Alternate invasion pathways are thus commonly used by
P. falciparum
field isolates. Typing based on two polymorphic markers, MSP-1 and MSP-2, and two microsatellite markers suggests that only 1 of the 15 field isolates tested contains multiple parasite genotypes. Individual
P. falciparum
lines can thus use multiple invasion pathways in the field. These observations have important implications for malaria vaccine development efforts based on EBA-175, the
P. falciparum
protein that binds sialic acid residues of glycophorin A during invasion. It may be necessary to target parasite ligands responsible for the alternate invasion pathways in addition to EBA-175 to effectively block erythrocyte invasion by
P. falciparum
.
Invasion of Human Coronary Artery Cells by Periodontal Pathogens
Authors: Dorn Brian R. , Dunn William A. , Progulske-Fox Ann 
Published: December 2019

ABSTRACT

There is an emerging paradigm shift from coronary heart disease having a purely hereditary and nutritional causation to possibly having an infectious etiology. Recent epidemiological studies have shown a correlation between periodontal disease and coronary heart disease. However, to date, there is minimal information as to the possible disease mechanisms of this association. It is our hypothesis that invasion of the coronary artery cells by oral bacteria may start and/or exacerbate the inflammatory response in atherosclerosis. Since a few periodontal pathogens have been reported to invade oral epithelial tissues, we tested the ability of three putative periodontal pathogens—
Eikenella corrodens
,
Porphyromonas gingivalis
, and
Prevotella intermedia
—to invade human coronary artery endothelial cells and coronary artery smooth muscle cells. In this study we demonstrate by an antibiotic protection assay and electron microscopy that specific species and strains invade coronary artery cells at a significant level. Actin polymerization and eukaryotic protein synthesis in metabolically active cells were required since the corresponding inhibitors nearly abrogated invasion. Many intracellular
P. gingivalis
organisms were seen to be present in multimembranous vacuoles resembling autophagosomes by morphological analysis. This is the first report of oral microorganisms invading human primary cell cultures of the vasculature.
Consequence of
Nramp1
Deletion to
Mycobacterium tuberculosis
Infection in Mice
Authors: North Robert J. , LaCourse Ronald , Ryan Lynn , Gros Philippe 
Published: December 2019

ABSTRACT

129sv mice functionally deleted of the antimicrobial resistance gene,
Nramp1
, were found to be as resistant as wild-type mice to infection with the virulent H37Rv strain of
Mycobacterium tuberculosis
, as determined by monitoring bacterial growth in major organs and recording host survival times. Death of infected mice of both types was associated with extensive infection-induced pathology in the lungs but not in other major organs. These findings are in keeping with the view that
Nramp1
is of limited importance in resistance to tuberculosis in mice.
Local Production of Chemokines during Experimental Vaginal Candidiasis
Authors: Saavedra Michael , Taylor Brad , Lukacs Nicholas , Fidel Paul L. 
Published: December 2019

ABSTRACTRecurrent vulvovaginal candidiasis, caused byCandida albicans, is a significant problem in women of childbearing age. Although cell-mediated immunity (CMI) due to T cells and cytokines is the predominant host defense mechanism againstC. albicansat mucosal tissue sites, host defense mechanisms againstC. albicansat the vaginal mucosa are poorly understood. Based on an estrogen-dependent murine model of vaginal candidiasis, our data suggest that systemic CMI is ineffective againstC. albicansvaginal infections. Thus, we have postulated that local immune mechanisms are critical for protection against infection. In the present study, the kinetic production of chemokines normally associated with the chemotaxis of T cells, macrophages (RANTES, MIP-1α, MCP-1), and polymorphonuclear neutrophils (MIP-2) was examined following intravaginal inoculation ofC. albicansin estrogen-treated or untreated mice. Results showed significant increases in MCP-1 protein and mRNA in vaginal tissue of infected mice as early as 2 and 4 days postinoculation, respectively, that continued through a 21-day observation period, irrespective of estrogen status. No significant changes were observed with RANTES, MIP-1α, or MIP-2, although relatively high constitutive levels of RANTES mRNA and MIP-2 protein were observed. Furthermore, intravaginal immunoneutralization of MCP-1 with anti-MCP-1 antibodies resulted in a significant increase in vaginal fungal burden early during infection, suggesting that MCP-1 plays some role in reducing the fungal burden during vaginal infection. However, the lack of changes in leukocyte profiles in vaginal lavage fluids collected from infected versus uninfected mice suggests that MCP-1 functions to control vaginalC. albicanstiters in a manner independent of cellular chemotactic activity.
Contribution of Quorum Sensing to the Virulence of
Pseudomonas aeruginosa
in Burn Wound Infections
Authors: Rumbaugh Kendra P. , Griswold John A. , Iglewski Barbara H. , Hamood Abdul N. 
Published: December 2019

ABSTRACT

The
Pseudomonas aeruginosa
quorum-sensing systems,
las
and
rhl
, control the production of numerous virulence factors. In this study, we have used the burned-mouse model to examine the contribution of quorum-sensing systems to the pathogenesis of
P. aeruginosa
infections in burn wounds. Different quorum-sensing mutants of
P. aeruginosa
PAO1 that were defective in the
lasR
,
lasI
, or
rhlI
gene or both the
lasI
and
rhlI
genes were utilized. The following parameters of the
P. aeruginosa
infection were examined: (i) lethality to the burned mouse, (ii) dissemination of the
P. aeruginosa
strain within the body of the infected mouse (by determining the numbers of CFU of
P. aeruginosa
within the liver and spleen), and (iii) spread of the
P. aeruginosa
strain within the burned skin (by determining the numbers of CFU of
P. aeruginosa
at the inoculation site and at a site about 15 mm from the inoculation site [distant site]). In comparison with that of PAO1, the in vivo virulence of
lasI
,
lasR
, and
rhlI
mutants was significantly reduced. However, the most significant reduction in in vivo virulence was seen with the
lasI rhlI
mutant. The numbers of CFU that were recovered from the livers, spleens, and skin of mice infected with different mutants were significantly lower than those of PAO1. At 8 and 16 h post burn infection, comparable numbers of CFU of PAO1 and
lasI
and
rhlI
mutants were obtained from both the inoculation and distant sites of the burned skin of infected mice. In contrast, CFU of the
lasR
mutant and the
lasI rhlI
double mutant were recovered only from the inoculation site of infected mice at 8 and 16 h post burn infection. The ability of a plasmid carrying either the
lasI
or
rhlI
gene or the
lasI
and
rhlI
genes to complement the defect of the
lasI rhlI
double mutant was also examined. The presence of any of these plasmids within the
lasI rhlI
double mutant significantly enhanced its in vivo virulence, as well as its ability to spread within the burned skin. These results suggest that the quorum-sensing systems play an important role in the horizontal spread of
P. aeruginosa
within burned skin and in the dissemination of
P. aeruginosa
within the bodies of burned-and-infected mice and contributed to the overall virulence of
P. aeruginosa
in this animal model.