bluuebunny/crossref_metadata_2025_split huggingface dataset:
Isolation ofRickettsia parkeriand Identification of a Novel Spotted Fever GroupRickettsiasp. from Gulf Coast Ticks (Amblyomma maculatum) in the United States
Authors: Paddock Christopher D. , Fournier Pierre-Edouard , Sumner John W. , Goddard Jerome , Elshenawy Yasmin , Metcalfe Maureen G. , Loftis Amanda D. , Varela-Stokes Andrea 
Published: March 2010

ABSTRACTUntil recently,Amblyomma maculatum(the Gulf Coast tick) had garnered little attention compared to other species of human-biting ticks in the United States.A. maculatumis now recognized as the principal vector ofRickettsia parkeri, a pathogenic spotted fever group rickettsia (SFGR) that causes an eschar-associated illness in humans that resembles Rocky Mountain spotted fever. A novel SFGR, distinct from other recognizedRickettsiaspp., has also been detected recently inA. maculatumspecimens collected in several regions of the southeastern United States. In this study, 198 questing adult Gulf Coast ticks were collected at 4 locations in Florida and Mississippi; 28% of these ticks were infected withR. parkeri, and 2% of these were infected with a novel SFGR. Seventeen isolates ofR. parkerifrom individual specimens ofA. maculatumwere cultivated in Vero E6 cells; however, all attempts to isolate the novel SFGR were unsuccessful. Partial genetic characterization of the novel SFGR revealed identity with several recently described, incompletely characterized, and noncultivated SFGR, including “CandidatusRickettsia andeanae” andRickettsiasp. Argentina detected in several species of Neotropical ticks from Argentina and Peru. These findings suggest that each of these “novel” rickettsiae represent the same species. This study considerably expanded the number of low-passage,A. maculatum-derived isolates ofR. parkeriand characterized a second, sympatricRickettsiasp. found in Gulf Coast ticks.
Heterologous Expression of the Oxytetracycline Biosynthetic Pathway in
Myxococcus xanthus
Authors: Stevens D. Cole , Henry Michael R. , Murphy Kimberly A. , Boddy Christopher N. 
Published: March 2010

ABSTRACT

New natural products for drug discovery may be accessed by heterologous expression of bacterial biosynthetic pathways in metagenomic DNA libraries. However, a “universal” host is needed for this experiment. Herein, we show that
Myxococcus xanthus
is a potential “universal” host for heterologous expression of polyketide biosynthetic gene clusters.
Impact of Siderophore Production by
Pseudomonas syringae
pv. syringae 22d/93 on Epiphytic Fitness and Biocontrol Activity against
Pseudomonas syringae
pv. glycinea 1a/96
Authors: Wensing Annette , Braun Sascha D. , Büttner Petra , Expert Dominique , Völksch Beate , Ullrich Matthias S. , Weingart Helge 
Published: March 2010

ABSTRACT

The use of naturally occurring microbial antagonists to suppress plant diseases offers a favorable alternative to classical methods of plant protection. The soybean epiphyte
Pseudomonas syringae
pv. syringae strain 22d/93 shows great potential for controlling
P. syringae
pv. glycinea, the causal agent of bacterial blight of soybean. Its activity against
P. syringae
pv. glycinea is highly reproducible even in field trials, and the suppression mechanisms involved are of special interest. In this work we demonstrated that
P
.
syringae
pv. syringae 22d/93 produced a significantly larger amount of siderophores than the pathogen
P. syringae
pv. glycinea produced. While
P
.
syringae
pv. syringae 22d/93 and
P. syringae
pv. glycinea produce the same siderophores, achromobactin and pyoverdin, the regulation of siderophore biosynthesis in the former organism is very different from that in the latter organism. The epiphytic fitness of
P
.
syringae
pv. syringae 22d/93 mutants defective in siderophore biosynthesis was determined following spray inoculation of soybean leaves. The population size of the siderophore-negative mutant
P
.
syringae
pv. syringae strain 22d/93ΔSid was 2 orders of magnitude lower than that of the wild type 10 days after inoculation. The growth deficiency was compensated for when wound inoculation was used, indicating the availability of iron in the presence of small lesions on the leaves. Our results suggest that siderophore production has an indirect effect on the biocontrol activity of
P
.
syringae
pv. syringae 22d/93. Although siderophore-defective mutants of
P
.
syringae
pv. syringae 22d/93 still suppressed development of bacterial blight caused by
P. syringae
pv. glycinea, siderophore production enhanced the epiphytic fitness and thus the competitiveness of the antagonist.
Nuclear Dynamics, Mitosis, and the Cytoskeleton during the Early Stages of Colony Initiation in Neurospora crassa
Authors: Roca M. Gabriela , Kuo Hsiao-Che , Lichius Alexander , Freitag Michael , Read Nick D. 
Published: March 2010

ABSTRACT

Neurospora crassa
macroconidia form germ tubes that are involved in colony establishment and conidial anastomosis tubes (CATs) that fuse to form interconnected networks of conidial germlings. Nuclear and cytoskeletal behaviors were analyzed in macroconidia, germ tubes, and CATs in strains that expressed fluorescently labeled proteins. Heterokaryons formed by CAT fusion provided a rapid method for the imaging of multiple labeled fusion proteins and minimized the potential risk of overexpression artifacts. Mitosis occurred more slowly in nongerminated macroconidia (1.0 to 1.5 h) than in germ tubes (16 to 20 min). The nucleoporin SON-1 was not released from the nuclear envelope during mitosis, which suggests that
N. crassa
exhibits a form of “closed mitosis.” During CAT homing, nuclei did not enter CATs, and mitosis was arrested. Benomyl treatment showed that CAT induction, homing, fusion, as well as nuclear migration through fused CATs do not require microtubules or mitosis. Three
ropy
mutants (
ro-1
,
ro-3
, and
ro-11
) defective in the dynein/dynactin microtubule motor were impaired in nuclear positioning, but nuclei still migrated through fused CATs. Latrunculin B treatment, imaging of F-actin in living cells using Lifeact-red fluorescent protein (RFP), and analysis of mutants defective in the Arp2/3 complex demonstrated that actin plays important roles in CAT fusion.
Mitochondrial DNA Heteroplasmy in Candida glabrata after Mitochondrial Transformation
Authors: Zhou Jingwen , Liu Liming , Chen Jian 
Published: March 2010

ABSTRACT

Genetic manipulation of mitochondrial DNA (mtDNA) is the most direct method for investigating mtDNA, but until now, this has been achieved only in the diploid yeast
Saccharomyces cerevisiae
. In this study, the
ATP6
gene on mtDNA of the haploid yeast
Candida glabrata
(
Torulopsis glabrata
) was deleted by biolistic transformation of DNA fragments with a recoded
ARG8

m

mitochondrial genetic marker, flanked by homologous arms to the
ATP6
gene. Transformants were identified by arginine prototrophy. However, in the transformants, the original mtDNA was not lost spontaneously, even under arginine selective pressure. Moreover, the mtDNA transformants selectively lost the transformed mtDNA under aerobic conditions. The mtDNA heteroplasmy in the transformants was characterized by PCR, quantitative PCR, and Southern blotting, showing that the heteroplasmy was relatively stable in the absence of arginine. Aerobic conditions facilitated the loss of the original mtDNA, and anaerobic conditions favored loss of the transformed mtDNA. Moreover, detailed investigations showed that increases in reactive oxygen species in mitochondria lacking
ATP6
, along with their equal cell division, played important roles in determining the dynamics of heteroplasmy. Based on our analysis of mtDNA heteroplasmy in
C. glabrata
, we were able to generate homoplasmic Δ
atp6
mtDNA strains.
High-Quality Draft Genome Sequences of 28
Enterococcus
sp. Isolates
Authors: Palmer Kelli L. , Carniol Karen , Manson Janet M. , Heiman David , Shea Terry , Young Sarah , Zeng Qiandong , Gevers Dirk , Feldgarden Michael , Birren Bruce , Gilmore Michael S. 
Published: March 2010

ABSTRACT

The enterococci are low-GC Gram-positive bacteria that have emerged as leading causes of hospital-acquired infection. They are also commensals of the gastrointestinal tract of healthy humans and most other animals with gastrointestinal flora and are important for food fermentations. Here we report the availability of draft genome sequences for 28 enterococcal strains of diverse origin, including the species
Enterococcus faecalis
,
E. faecium
,
E. casseliflavus
, and
E. gallinarum
.
Crystal Structure of Activated CheY1 from
Helicobacter pylori
Authors: Lam Kwok Ho , Ling Thomas Kin Wah , Au Shannon Wing Ngor 
Published: March 2010

ABSTRACT

Chemotaxis is an important virulence factor for
Helicobacter pylori
colonization and infection. The chemotactic system of
H. pylori
is marked by the presence of multiple response regulators: CheY1, one CheY-like-containing CheA protein (CheAY2), and three CheV proteins. Recent studies have demonstrated that these molecules play unique roles in the chemotactic signal transduction mechanisms of
H. pylori
. Here we report the crystal structures of BeF

3
−

-activated CheY1 from
H. pylori
resolved to 2.4 Å. Structural comparison of CheY1 with active-site residues of BeF

3
−

-bound CheY from
Escherichia coli
and fluorescence quenching experiments revealed the importance of Thr84 in the phosphotransfer reaction. Complementation assays using various nonchemotactic
E. coli
mutants and pull-down experiments demonstrated that CheY1 displays differential association with the flagellar motor in
E. coli
. The structural rearrangement of helix 5 and the C-terminal loop in CheY1 provide a different interaction surface for FliM. On the other hand, interaction of the CheA-P2 domain with CheY1, but not with CheY2/CheV proteins, underlines the preferential recognition of CheY1 by CheA in the phosphotransfer reaction. Our results provide the first structural insight into the features of the
H. pylori
chemotactic system as a model for
Epsilonproteobacteria
.
Characterization of the
Klebsiella aerogenes
Urease Accessory Protein UreD in Fusion with the Maltose Binding Protein
Authors: Carter Eric L. , Hausinger Robert P. 
Published: March 2010

ABSTRACT

Assembly of the
Klebsiella aerogenes
urease metallocenter requires four accessory proteins, UreD, UreE, UreF, and UreG, to effectively deliver and incorporate two Ni
2+
ions into the nascent active site of the urease apoprotein (UreABC). Each accessory protein has been purified and characterized with the exception of UreD due to its insolubility when it is overproduced in recombinant cells. In this study, a translational fusion was made between the maltose binding protein (MBP) and UreD, with the resulting MBP-UreD found to be soluble in
Escherichia coli
cell extracts and able to complement a Δ
ureD
-urease cluster in this host microorganism. MBP-UreD was purified as a large multimer (>670 kDa) that bound approximately 2.5 Ni
2+
ions (

K
d

of ∼50 μM, where

K
d

is the dissociation constant) per UreD protomer according to equilibrium dialysis measurements. Zn
2+
directly competes with 10-fold higher affinity (∼4 Zn
2+
ions per protomer;

K
d

of 5 μM) for the Ni
2+
binding sites. MBP pulldown experiments demonstrated that the UreD domain of MBP-UreD formed
in vivo
complexes with UreF, UreG, UreF plus UreG, or UreABC when these proteins were overproduced in the same
E. coli
cells. In addition, a UreABC-(MBP-UreD)-UreFG complex was observed in cells producing all urease components. Comparative
in vitro
binding experiments with purified proteins demonstrated an approximate 1:1 binding ratio between the UreD domain of MBP-UreD and the UreF domain of the UreEF fusion, only weak or transient interaction between MBP-UreD and UreG, and no binding with UreABC. These studies are the first to describe the properties of purified UreD, and they extend our understanding of its binding partners both
in vitro
and in the cell.
Advantage of Upregulation of Succinate Dehydrogenase in
Staphylococcus aureus
Biofilms
Authors: Gaupp Rosmarie , Schlag Steffen , Liebeke Manuel , Lalk Michael , Götz Friedrich 
Published: March 2010

ABSTRACT

Previous studies have demonstrated that various tricarboxylic acid (TCA) cycle genes, particularly the succinate dehydrogenase genes (
sdhCAB
), are upregulated in
Staphylococcus aureus
biofilms. To better study the role of this enzyme complex, an
sdhCAB
deletion mutant (Δ
sdh
) was constructed. Compared to the wild type (wt) the mutant was impaired in planktonic growth under aerobic conditions, excreted acetic acid could not be reused and accumulated continuously, succinate was excreted and found in the culture supernatant, and metabolome analysis with cells grown in chemically defined medium revealed reduced uptake/metabolism of some amino acids from the growth medium. Moreover, the mutant was able to counteract the steadily decreasing extracellular pH by increased urease activity. The addition of fumarate to the growth medium restored the wt phenotype. The mutant showed a small-colony variant (SCV)-like phenotype, a slight increase in resistance to various aminoglycoside antibiotics, and decreased pigmentation. The decreased growth under aerobic conditions is due to the interruption of the TCA cycle (indicated by the accumulation of succinate and acetic acid) with the consequence that many fewer reduction equivalents (NADH and FADH
2
) can fuel the respiratory chain. The results indicate that the TCA cycle is required for acetate and amino acid catabolism; its upregulation under biofilm conditions is advantageous under such nutrient- and oxygen-limited conditions.
Regulation of
pga
Operon Expression and Biofilm Formation in
Actinobacillus pleuropneumoniae
by σ
E
and H-NS
Authors: Bossé Janine T. , Sinha Sunita , Li Ming-Shi , O'Dwyer Clíona A. , Nash John H. E. , Rycroft Andrew N. , Kroll J. Simon , Langford Paul R. 
Published: March 2010

ABSTRACT

Clinical isolates of the porcine pathogen
Actinobacillus pleuropneumoniae
often form adherent colonies on agar plates due to expression of an operon,
pgaABCD
, encoding a poly-β-1,6-
N
-acetyl-
d
-glucosamine (PGA) extracellular matrix. The adherent colony phenotype, which correlates with the ability to form biofilms on the surfaces of polystyrene plates, is lost following serial passage in broth culture, and repeated passage of the nonadherent variants on solid media does not result in reversion to the adherent colony phenotype. In order to investigate the regulation of PGA expression and biofilm formation in
A. pleuropneumoniae
, we screened a bank of transposon mutants of the nonadherent serovar 1 strain S4074
T
and identified mutations in two genes,
rseA
and
hns
, which resulted in the formation of the adherent colony phenotype. In other bacteria, including the
Enterobacteriaceae
, H-NS acts as a global gene regulator, and RseA is a negative regulator of the extracytoplasmic stress response sigma factor σ
E
. Transcription profiling of
A. pleuropneumoniae rseA
and
hns
mutants revealed that both σ
E
and H-NS independently regulate expression of the
pga
operon. Transcription of the
pga
operon is initiated from a σ
E
promoter site in the absence of H-NS, and upregulation of σ
E
is sufficient to displace H-NS, allowing transcription to proceed. In
A. pleuropneumoniae
, H-NS does not act as a global gene regulator but rather specifically regulates biofilm formation via repression of the
pga
operon. Positive regulation of the
pga
operon by σ
E
indicates that biofilm formation is part of the extracytoplasmic stress response in
A. pleuropneumoniae
.
Physiological and Transcriptional Response ofLactobacillus caseiATCC 334 to Acid Stress
Authors: Broadbent Jeff R. , Larsen Rebecca L. , Deibel Virginia , Steele James L. 
Published: March 2010

ABSTRACTThis study investigated features of the acid tolerance response (ATR) inLactobacillus caseiATCC 334. To optimize ATR induction, cells were acid adapted for 10 or 20 min at different pH values (range, 3.0 to 5.0) and then acid challenged at pH 2.0. Adaptation over a broad range of pHs improved acid tolerance, but the highest survival was noted in cells acid adapted for 10 or 20 min at pH 4.5. Analysis of cytoplasmic membrane fatty acids (CMFAs) in acid-adapted cells showed that they had significantly (P< 0.05) higher total percentages of saturated and cyclopropane fatty acids than did control cells. Specifically, large increases in the percentages of C14:0, C16:1n(9), C16:0, and C19:0(11c)were noted in the CMFAs of acid-adapted and acid-adapted, acid-challenged cells, while C18:1n(9)and C18:1n(11)showed the greatest decrease. Comparison of the transcriptome from control cells (grown at pH 6.0) against that from cells acid adapted for 20 min at pH 4.5 indicated that acid adaption invoked a stringent-type response that was accompanied by other functions which likely helped these cells resist acid damage, including malolactic fermentation and intracellular accumulation of His. Validation of microarray data was provided by experiments that showed thatL. caseisurvival at pH 2.5 was improved at least 100-fold by chemical induction of the stringent response or by the addition of 30 mM malate or 30 mM histidine to the acid challenge medium. To our knowledge, this is the first report that intracellular histidine accumulation may be involved in bacterial acid resistance.
Mechanical thrombectomy with the penumbra system for treatment of venous sinus thrombosis
Authors: Choulakian Armen , Alexander Michael J 
Published: March 2010

ObjectiveVenous sinus thrombosis can be a fatal condition. When systemic anticoagulation therapy fails or is high risk, endovascular chemical thrombolysis or mechanical thrombectomy may be necessary. We report our experience using the Penumbra system (PS; Penumbra, Alameda, California, USA) in a series of four patients with venous sinus thrombosis.MethodsFour patients were treated with mechanical thrombectomy using the PS for venous sinus thrombosis. Three of these patients also underwent balloon angioplasty following the PS device. Utility of this technique was evaluated by procedural success, improvement in neurological condition, avoidance of complications and follow-up imaging.ResultsTechnical success was achieved in all four patients with restoration of flow in the occluded sinuses without the use of chemical thrombolysis. No complications were encountered during the procedure and no postprocedural complications were attributable to the thrombectomy. One patient with glioblastoma died 6 weeks after the procedure. No new intracerebral hemorrhages were caused and there was no exacerbation of pretreatment intracerebral hemorrhages. Follow-up imaging was available in all but one patient to documented continued sinus patency. Neurologic improvement was seen in all patients after thrombectomy. Two patients have returned for outpatient follow-up and both are doing well.ConclusionEndovascular treatment for venous sinus thrombosis with the PS is a safe and efficacious alternative to the other forms of mechanical thrombectomy reported in the literature. Good clinical and radiographic results can be obtained without the need for chemical thrombolysis.
A critical reappraisal of “preconsolidation pressure” interpretations using the oedometer test
Authors: Boone Storer J. 
Published: March 2010

Over the past 70 years, a number of methods have been proposed for the interpretation of the characteristic vertical effective yield stress, or “preconsolidation pressure,” of compressible soils as defined using the standard oedometer test. The concept of the “preconsolidation pressure” has been extraordinarily useful in geotechnical engineering for analysing and predicting settlement behaviour and for normalizing other engineering parameters for comparative purposes. Defining this characteristic stress, however, is often problematic and relies heavily on graphical techniques that are subject to some uncertainty, particularly when using semi-log plots for this purpose. This paper illustrates fundamental difficulties with the interpretation of oedometer test and presents an alternative technique for defining unambiguous values of the vertical effective yield stress.
Hepatic Metabolism and Transporter Gene Variants Enhance Response to Rosuvastatin in Patients With Acute Myocardial Infarction
Authors: Bailey Kristian M. , Romaine Simon P.R. , Jackson Beryl M. , Farrin Amanda J. , Efthymiou Maria , Barth Julian H. , Copeland Joanne , McCormack Terry , Whitehead Andrew , Flather Marcus D. , Samani Nilesh J. , Nixon Jane , Hall Alistair S. , Balmforth Anthony J. ,   on behalf of the SPACE ROCKET Trial Group
Published: March 2010

Background—
Pharmacogenetics aims to maximize benefits and minimize risks of drug treatment. Our objectives were to examine the influence of common variants of hepatic metabolism and transporter genes on the lipid-lowering response to statin therapy.

Methods and Results—

The Genetic Effects On STATins (GEOSTAT-1) Study was a genetic substudy of Secondary Prevention of Acute Coronary Events—Reduction of Cholesterol to Key European Targets (SPACE ROCKET) (a randomized, controlled trial comparing 40 mg of simvastatin and 10 mg of rosuvastatin) that recruited 601 patients after myocardial infarction. We genotyped the following functional single nucleotide polymorphisms in the genes coding for the cytochrome P450 (CYP) metabolic enzymes, CYP2C9*2 (430C>T), CYP2C9*3 (1075A>C), CYP2C19*2 (681G>A), CYP3A5*1 (6986A>G), and hepatic influx and efflux transporters SLCO1B1 (521T>C) and breast cancer resistance protein (BCRP; 421C>A). We assessed 3-month LDL cholesterol levels and the proportion of patients reaching the current LDL cholesterol target of <70 mg/dL (<1.81 mmol/L). An enhanced response to rosuvastatin was seen for patients with variant genotypes of either CYP3A5 (
P
=0.006) or BCRP (
P
=0.010). Furthermore, multivariate logistic-regression analysis revealed that patients with at least 1 variant CYP3A5 and/or BCRP allele (n=186) were more likely to achieve the LDL cholesterol target (odds ratio: 2.289; 95% CI: 1.157, 4.527;
P
=0.017; rosuvastatin 54.0% to target vs simvastatin 33.7%). There were no differences for patients with variants of CYP2C9, CYP2C19, or SLCO1B1 in comparison with their respective wild types, nor were differential effects on statin response seen for patients with the most common genotypes for CYP3A5 and BCRP (n=415; odds ratio: 1.207; 95% CI: 0.768, 1.899;
P
=0.415).

Conclusion—
The LDL cholesterol target was achieved more frequently for the 1 in 3 patients with CYP3A5 and/or BCRP variant genotypes when prescribed rosuvastatin 10 mg, compared with simvastatin 40 mg.

Clinical Trial Registration—

URL:
http://isrctn.org
. Unique identifier: ISRCTN 89508434.