bluuebunny/crossref_metadata_2025_split huggingface dataset:
Screening and Quantification of the Expression of Antibiotic Resistance Genes in
Acinetobacter baumannii
with a Microarray
Authors: Coyne Sébastien , Guigon Ghislaine , Courvalin Patrice , Périchon Bruno 
Published: November 2009

ABSTRACT

An oligonucleotide-based DNA microarray was developed to evaluate expression of genes for efflux pumps in
Acinetobacter baumannii
and to detect acquired antibiotic resistance determinants. The microarray contained probes for 205 genes, including those for 47 efflux systems, 55 resistance determinants, and 35 housekeeping genes. The microarray was validated by comparative analysis of mutants overexpressing or deficient in the pumps relative to the parental strain. The performance of the microarray was also evaluated using in vitro single-step mutants obtained on various antibiotics. Overexpression, confirmed by quantitative reverse transcriptase PCR, of RND efflux pumps AdeABC, due to a G30D substitution in AdeS in a multidrug-resistant (MDR) strain obtained on gentamicin, and AdeIJK, in two mutants obtained on cefotaxime or tetracycline, was detected. A new efflux pump, AdeFGH, was found to be overexpressed in a mutant obtained on chloramphenicol. Study of MDR clinical isolates, including the AYE strain, whose entire sequence has been determined, indicated overexpression of AdeABC and of the chromosomally encoded cephalosporinase as well as the presence of several acquired resistance genes. The overexpressed and acquired determinants detected by the microarray could account for nearly the entire MDR phenotype of the isolates. The microarray is potentially useful for detection of resistance in
A. baumannii
and should allow detection of new efflux systems associated with antibiotic resistance.
An A643T Mutation in the Transcription Factor Upc2p Causes Constitutive
ERG11
Upregulation and Increased Fluconazole Resistance in
Candida albicans
Authors: Heilmann Clemens J. , Schneider Sabrina , Barker Katherine S. , Rogers P. David , Morschhäuser Joachim 
Published: November 2009

ABSTRACT

The zinc cluster transcription factor Upc2p mediates upregulation of ergosterol biosynthesis genes in response to ergosterol depletion in the fungal pathogen
Candida albicans
. One mechanism of acquired resistance to the antifungal drug fluconazole, which inhibits ergosterol biosynthesis, is constitutively increased expression of the
ERG11
gene encoding the drug target enzyme. A G648D mutation in Upc2p has recently been shown to cause hyperactivity of the transcription factor, resulting in overexpression of ergosterol biosynthesis genes and increased fluconazole resistance. In order to investigate if gain-of-function mutations in Upc2p are a common mechanism of
ERG11
upregulation and fluconazole resistance, we sequenced the
UPC2
alleles of four
ERG11
-overexpressing, fluconazole-resistant
C. albicans
isolates and matched susceptible isolates from the same patients. In three of the isolate pairs, no differences in the
UPC2
alleles were found, suggesting that mechanisms other than Upc2p mutations can cause
ERG11
overexpression. One resistant isolate had become homozygous for a
UPC2
allele containing a G1927A substitution that caused an alanine-to-threonine exchange at amino acid position 643 of Upc2p. Replacement of one of the endogenous
UPC2
alleles in a fluconazole-susceptible strain by the
UPC2
A643T
allele resulted in
ERG11
overexpression and increased fluconazole resistance, which was further elevated when the A643T mutation was also introduced into the second
UPC2
allele. These results further establish gain-of-function mutations in
UPC2
, which can be followed by loss of heterozygosity for the mutated allele, as a mechanism of
ERG11
overexpression and increased fluconazole resistance in
C. albicans
, but other mechanisms of
ERG11
upregulation also exist.
Biologic Activities of the TolC-Like Protein of
Neisseria meningitidis
as Assessed by Functional Complementation in
Escherichia coli
Authors: Kamal Nazia , Shafer William M. 
Published: November 2009

ABSTRACT

Neisseria meningitidis
can produce a TolC-like protein needed for secretion of FrpC but not efflux of antimicrobials. We now report that expression of the meningococcal
tolC
gene in a TolC-deficient strain of
Escherichia coli
can restore properties of α-hemolysis and antimicrobial resistance known to involve efflux pumps.
Increased Glucose Utilization in
Corynebacterium glutamicum
by Use of Maltose, and Its Application for the Improvement of
l
-Valine Productivity
Authors: Krause Felix S. , Henrich Alexander , Blombach Bastian , Krämer Reinhard , Eikmanns Bernhard J. , Seibold Gerd M. 
Published: October 2009

ABSTRACT

Corynebacterium glutamicum
efficiently utilizes maltose as a substrate. We show here that the presence of maltose increases glucose utilization by raising the expression of
ptsG
, which encodes the glucose-specific EII permease of the phosphotransferase system. Consequently, the
l
-valine productivity of a pyruvate dehydrogenase complex-deficient
C. glutamicum
strain was improved by the presence of maltose.
Examination of
Xenorhabdus nematophila
Lipases in Pathogenic and Mutualistic Host Interactions Reveals a Role for
xlpA
in Nematode Progeny Production
Authors: Richards Gregory R. , Goodrich-Blair Heidi 
Published: October 2009

ABSTRACT

Xenorhabdus nematophila
is a gammaproteobacterium and broad-host-range insect pathogen. It is also a symbiont of
Steinernema carpocapsae
, the nematode vector that transports the bacterium between insect hosts.
X. nematophila
produces several secreted enzymes, including hemolysins, lipases, and proteases, which are thought to contribute to virulence or nutrient acquisition for the bacterium and its nematode host in vivo.
X. nematophila
has two lipase activities with distinct in vitro specificities for Tween and lecithin. The gene encoding the Tween-specific lipase,
xlpA
, has been identified and is not required for
X. nematophila
virulence in one insect host, the tobacco hornworm
Manduca sexta
. However, the gene encoding the lecithin-specific lipase activity is not currently known. Here, we identify
X. nematophila estA
, a gene encoding a putative lecithinase, and show that an
estA
mutant lacks in vitro lipase activity against lecithin but has wild-type virulence in
Manduca sexta. X. nematophila
secondary-form phenotypic variants have higher in vitro lecithinase activity and
estA
transcript levels than do primary-form variants, and
estA
transcription is negatively regulated by NilR, a repressor of nematode colonization factors. We establish a role for
xlpA
, but not
estA
, in supporting production of nematode progeny during growth in
Galleria mellonella
insects. Future research is aimed at characterizing the biological roles of
estA
and
xlpA
in other insect hosts.
Diverse Genetic Markers Concordantly Identify Bovine OriginEscherichia coliO157 Genotypes Underrepresented in Human Disease
Authors: Whitworth Joshua , Zhang Yubei , Bono James , Pleydell Eve , French Nigel , Besser Thomas 
Published: October 2009

ABSTRACTGenetic markers previously reported to occur at significantly different frequencies in isolates ofEscherichia coliO157:H7 obtained from cattle and from clinically affected humans concordantly delineate at least five genetic groups. Isolates in three of these groups consistently carry one or more markers rarely found among clinical isolates.
Low-Density Macroarray Targeting Non-Locus of Enterocyte Effacement Effectors (
nle
Genes) and Major Virulence Factors of Shiga Toxin-Producing
Escherichia coli
(STEC): a New Approach for Molecular Risk Assessment of STEC Isolates
Authors: Bugarel Marie , Beutin Lothar , Fach Patrick 
Published: October 2009

ABSTRACT

Rapid and specific detection of Shiga toxin-producing
Escherichia coli
(STEC) strains with a high level of virulence for humans has become a priority for public health authorities. This study reports on the development of a low-density macroarray for simultaneously testing the genes
stx
1
,
stx
2
,
eae
, and
ehxA
and six different
nle
genes issued from genomic islands OI-122 (
ent
,
nleB
, and
nleE
) and OI-71 (
nleF
,
nleH1
-
2
, and
nleA
). Various strains of
E. coli
isolated from the environment, food, animals, and healthy children have been compared with clinical isolates of various seropathotypes. The
eae
gene was detected in all enteropathogenic
E. coli
(EPEC) strains as well as in enterohemorrhagic
E. coli
(EHEC) strains, except in EHEC O91:H21 and EHEC O113:H21. The gene
ehxA
was more prevalent in EHEC (90%) than in STEC (42.66%) strains, in which it was unequally distributed. The
nle
genes were detected only in some EPEC and EHEC strains but with various distributions, showing that
nle
genes are strain and/or serotype specific, probably reflecting adaptation of the strains to different hosts or environmental niches. One characteristic
nle
gene distribution in EHEC O157:[H7], O111:[H8], O26:[H11], O103:H25, O118:[H16], O121:[H19], O5:H−, O55:H7, O123:H11, O172:H25, and O165:H25 was
ent/espL2
,
nleB
,
nleE
,
nleF
,
nleH1
-
2
,
nleA
. (Brackets indicate genotyping of the
flic
or
rfb
genes.) A second
nle
pattern (
ent/espL2
,
nleB
,
nleE
,
nleH1
-
2
) was characteristic of EHEC O103:H2, O145:[H28], O45:H2, and O15:H2. The presence of
eae
,
ent/espL2
,
nleB
,
nleE
, and
nleH1
-
2
genes is a clear signature of STEC strains with high virulence for humans.
Copper Stress Induces a Global Stress Response in
Staphylococcus aureus
and Represses
sae
and
agr
Expression and Biofilm Formation
Authors: Baker Jonathan , Sitthisak Sutthirat , Sengupta Mrittika , Johnson Miranda , Jayaswal R. K. , Morrissey Julie A. 
Published: October 2009

ABSTRACT

Copper is an important cofactor for many enzymes; however, high levels of copper are toxic. Therefore, bacteria must ensure there is sufficient copper for use as a cofactor but, more importantly, must limit free intracellular levels to prevent toxicity. In this study, we have used DNA microarray to identify
Staphylococcus aureus
copper-responsive genes. Transcriptional profiling of
S. aureus
SH1000 grown in excess copper identified a number of genes which fall into four groups, suggesting that
S. aureus
has four main mechanisms for adapting to high levels of environmental copper, as follows: (i) induction of direct copper homeostasis mechanisms; (ii) increased oxidative stress resistance; (iii) expression of the misfolded protein response; and (iv) repression of a number of transporters and global regulators such as Agr and Sae. Our experimental data confirm that resistance to oxidative stress and particularly to H
2
O
2
scavenging is an important
S. aureus
copper resistance mechanism. Our previous studies have demonstrated that Eap and Emp proteins, which are positively regulated by Agr and Sae, are required for biofilm formation under low-iron growth conditions. Our transcriptional analysis has confirmed that
sae
,
agr
, and
eap
are repressed under high-copper conditions and that biofilm formation is indeed repressed under high-copper conditions. Therefore, our results may provide an explanation for how copper films can prevent biofilm formation on catheters.
Role of Mitogen-Activated Protein Kinase Sty1 in Regulation of Eukaryotic Initiation Factor 2α Kinases in Response to Environmental Stress in
Schizosaccharomyces pombe
Authors: Berlanga Juan José , Rivero Damariz , Martín Ruth , Herrero Saturnino , Moreno Sergio , de Haro César 
Published: October 2009

ABSTRACT

The mitogen-activated protein kinase (MAPK) Sty1 is essential for the regulation of transcriptional responses that promote cell survival in response to different types of environmental stimuli in
Schizosaccharomyces pombe
. In fission yeast, three distinct eukaryotic initiation factor 2α (eIF2α) kinases, two mammalian HRI-related protein kinases (Hri1 and Hri2) and the Gcn2 ortholog, regulate protein synthesis in response to cellular stress conditions. In this study, we demonstrate that both Hri1 and Hri2 exhibited an autokinase activity, specifically phosphorylated eIF2α, and functionally replaced the endogenous
Saccharomyces cerevisiae
Gcn2. We further show that Gcn2, but not Hri1 or Hri2, is activated early after exposure to hydrogen peroxide and methyl methanesulfonate (MMS). Cells lacking Gcn2 exhibit a later activation of Hri2. The activated MAPK Sty1 negatively regulates Gcn2 and Hri2 activities under oxidative stress but not in response to MMS. In contrast, Hri2 is the primary activated eIF2α kinase in response to heat shock. In this case, the activation of Sty1 appears to be transitory and does not contribute to the modulation of the eIF2α kinase stress pathway. In strains lacking Hri2, a type 2A protein phosphatase is activated soon after heat shock to reduce eIF2α phosphorylation. Finally, the MAPK Sty1, but not the eIF2α kinases, is essential for survival upon oxidative stress or heat shock, but not upon MMS treatment. These findings point to a regulatory coordination between the Sty1 MAPK and eIF2α kinase pathways for a particular range of stress responses.
Algal Lipid Bodies: Stress Induction, Purification, and Biochemical Characterization in Wild-Type and StarchlessChlamydomonas reinhardtii
Authors: Wang Zi Teng , Ullrich Nico , Joo Sunjoo , Waffenschmidt Sabine , Goodenough Ursula 
Published: October 2009

ABSTRACTWhen the unicellular green soil algaChlamydomonas reinhardtiiis deprived of nitrogen after entering stationary phase in liquid culture, the cells produce abundant cytoplasmic lipid bodies (LBs), as well as abundant starch, via a pathway that accompanies a regulated autophagy program. After 48 h of N starvation in the presence of acetate, the wild-type LB content has increased 15-fold. When starch biosynthesis is blocked in thesta6mutant, the LB content increases 30-fold, demonstrating that genetic manipulation can enhance LB production. The use of cell wall-less strains permitted development of a rapid “popped-cell” microscopic assay to quantitate the LB content per cell and permitted gentle cell breakage and LB isolation. The highly purified LBs contain 90% triacylglycerol (TAG) and 10% free fatty acids (FFA). The fatty acids associated with the TAGs are ∼50% saturated (C16and C18) fatty acids and ∼50% unsaturated fatty acids, half of which are in the form of oleic acid (C18:1). The FFA are ∼50% C16and ∼50% C18. The LB-derived TAG yield from a liter ofsta6cells at 107cells/ml after starvation for 48 h is calculated to approach 400 mg. The LB fraction also contains low levels of charged glycerolipids, with the same profile as whole-cell charged glycerolipids, that presumably form LB membranes; chloroplast-specific neutral glycerolipids (galactolipids) are absent. Very low levels of protein are also present, but all matrix-assisted laser desorption ionization-identified species are apparent contaminants. Nitrogen stress-induced LB production inC. reinhardtiihas the hallmarks of a discrete pathway that should be amenable to additional genetic and culture condition manipulation.
Virulence, Inflammatory Potential, and Adaptive Immunity Induced by
Shigella flexneri msbB
Mutants
Authors: Ranallo Ryan T. , Kaminski Robert W. , George Tonia , Kordis Alexis A. , Chen Qing , Szabo Kathleen , Venkatesan Malabi M. 
Published: November 2009

ABSTRACT

The ability of genetically detoxified lipopolysaccharide (LPS) to stimulate adaptive immune responses is an ongoing area of investigation with significant consequences for the development of safe and effective bacterial vaccines and adjuvants. One approach to genetic detoxification is the deletion of genes whose products modify LPS. The
msbB1
and
msbB2
genes, which encode late acyltransferases, were deleted in the
Shigella flexneri
2a human challenge strain 2457T to evaluate the virulence, inflammatory potential, and acquired immunity induced by strains producing underacylated lipid A. Consistent with a reduced endotoxic potential,
S. flexneri
2a
msbB
mutants were attenuated in an acute mouse pulmonary challenge model. Attenuation correlated with decreases in the production of proinflammatory cytokines and in chemokine release without significant changes in lung histopathology. The levels of specific proinflammatory cytokines (interleukin-1β [IL-1β], macrophage inflammatory protein 1α [MIP-1α], and tumor necrosis factor alpha [TNF-α]) were also significantly reduced after infection of mouse macrophages with either single or double
msbB
mutants. Surprisingly, the
msbB
double mutant displayed defects in the ability to invade, replicate, and spread within epithelial cells. Complementation restored these phenotypes, but the exact nature of the defects was not determined. Acquired immunity and protective efficacy were also assayed in the mouse lung model, using a vaccination-challenge study. Both humoral and cellular responses were generally robust in
msbB
-immunized mice and afforded significant protection from lethal challenge. These data suggest that the loss of either
msbB
gene reduces the endotoxicity of
Shigella
LPS but does not coincide with a reduction in protective immune responses.
The Effects of PspC on Complement-Mediated Immunity to
Streptococcus pneumoniae
Vary with Strain Background and Capsular Serotype
Authors: Yuste Jose , Khandavilli Suneeta , Ansari Naadir , Muttardi Kairya , Ismail Laura , Hyams C. , Weiser Jeffrey , Mitchell Timothy , Brown Jeremy S. 
Published: November 2009

ABSTRACT

Streptococcus pneumoniae
may evade complement activity by binding of factor H (FH), a negative regulator of the alternative pathway, to the surface protein PspC. However, existing data on the effects of FH binding to PspC on complement activity are conflicting, and there is also considerable allelic variation in PspC structure between
S. pneumoniae
strains that may influence PspC-dependent effects on complement. We have investigated interactions with complement for several
S. pneumoniae
strains in which the gene encoding PspC has been deleted. The degree of FH binding varied between strains and was entirely dependent on PspC for seven strains. Data obtained with TIGR4 strains expressing different capsular serotypes suggest that FH binding is affected by capsular serotype. Results of immunoblot analysis for C3 degradation products and iC3b deposition assays suggested that FH bound to PspC retained functional activity, but loss of PspC had strikingly varied effects on C3b/iC3b deposition on
S. pneumoniae
, with large increases on serotype 4, 6A, 6B, and 9V strains but only small increases or even decreases on serotype 2, 3, 17, and 23F strains. Repeating C3b/iC3b assays with TIGR4 strains expressing different capsular serotypes suggested that differences in the effect of PspC on C3b/iC3b deposition were largely independent of capsular serotype and depend on strain background. However, data obtained from infection in complement-deficient mice demonstrated that differences between strains in the effects of PspC on complement surprisingly did not influence the development of septicemia.
Salmonella enterica
Serovar Typhimurium
trxA
Mutants Are Protective against Virulent Challenge and Induce Less Inflammation than the Live-Attenuated Vaccine Strain SL3261
Authors: Peters S. E. , Paterson G. K. , Bandularatne E. S. D. , Northen H. C. , Pleasance S. , Willers C. , Wang J. , Foote A. K. , Constantino-Casas F. , Scase T. J. , Blacklaws B. A. , Bryant C. E. , Mastroeni P. , Charles I. G. , Maskell D. J. 
Published: November 2009

ABSTRACT

In
Salmonella enterica
serovar Typhimurium,
trxA
encodes thioredoxin 1, a small, soluble protein with disulfide reductase activity, which catalyzes thiol disulfide redox reactions in a variety of substrate proteins. Thioredoxins are involved as antioxidants in defense against oxidative stresses, such as exposure to hydrogen peroxide and hydroxyl radicals. We have made a defined, complete deletion of
trxA
in the mouse-virulent
S.
Typhimurium strain SL1344 (SL1344
trxA
), replacing the gene with a kanamycin resistance gene cassette. SL1344
trxA
was attenuated for virulence in BALB/c mice by the oral and intravenous routes and when used in immunization experiments provided protection against challenge with the virulent parent strain. SL1344
trxA
induced less inflammation in murine spleens and livers than SL3261, the
aroA
mutant, live attenuated vaccine strain. The reduced splenomegaly observed following infection with SL1344
trxA
was partially attributed to a reduction in the number of both CD4
+
and CD8
+
T cells and B lymphocytes in the spleen and reduced infiltration by CD11b
+
cells into the spleen compared with spleens from mice infected with SL3261. This less severe pathological response indicates that a
trxA
mutation might be used to reduce reactogenicity of live attenuated vaccine strains. We tested this by deleting
trxA
in SL3261. SL3261
trxA
was also less inflammatory than SL3261 but was slightly less effective as a vaccine strain than either the SL3261 parent strain or SL1344
trxA
.
A Novel Functional Variant in the Stem Cell Growth Factor Promoter Protects against Severe Malarial Anemia
Authors: Ouma Collins , Keller Christopher C. , Davenport Gregory C. , Were Tom , Konah Stephen , Otieno Michael F. , Hittner James B. , Vulule John M. , Martinson Jeremy , Ong'echa John M. , Ferrell Robert E. , Perkins Douglas J. 
Published: November 2009

ABSTRACTPlasmodium falciparummalaria is a leading global cause of infectious disease burden. In areas in whichP. falciparumtransmission is holoendemic, such as western Kenya, severe malarial anemia (SMA) results in high rates of pediatric morbidity and mortality. Although the pathophysiological basis of SMA is multifactorial, we recently discovered that suppression of unexplored hematopoietic growth factors that promote erythroid and myeloid colony development, such as stem cell growth factor (SCGF) (C-type lectin domain family member 11A [CLEC11A]), was associated with enhanced development of SMA and reduced erythropoietic responses. To extend these investigations, the relationships between a novel SCGF promoter variant (−539C/T, rs7246355), SMA (hemoglobin [Hb] < 6.0 g/dl), and reduced erythropoietic responses (reticulocyte production index [RPI], <2.0) were investigated with Kenyan children (n= 486) with falciparum malaria from western Kenya. Circulating SCGF was positively correlated with hemoglobin levels (r= 0.251;P= 0.022) and the reticulocyte production index (RPI) (r= 0.268;P= 0.025). Children with SMA also had lower SCGF levels than those in the non-SMA group (P= 0.005). Multivariate logistic regression analyses controlling for covariates demonstrated that individuals with the homologous T allele were protected against SMA (odds ratio, 0.57; 95% confidence interval [95% CI] 0.34 to 0.94;P= 0.027) relative to CC (wild-type) carriers. Carriers of the TT genotype also had higher SCGF levels in circulation (P= 0.018) and in peripheral blood mononuclear cell culture supernatants (P= 0.041), as well as an elevated RPI (P= 0.005) relative to individuals with the CC genotype. The results presented here demonstrate that homozygous T at −539 in the SCGF promoter is associated with elevated SCGF production, enhanced erythropoiesis, and protection against the development of SMA in children with falciparum malaria.