bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Type VI Secretion System Plays a Role in Type 1 Fimbria Expression and Pathogenesis of an Avian Pathogenic
Escherichia coli
Strain
Authors: de Pace Fernanda , Nakazato Gerson , Pacheco Alline , Boldrin de Paiva Jacqueline , Sperandio Vanessa , Dias da Silveira Wanderley 
Published: September 2010

ABSTRACT

Avian pathogenic
Escherichia coli
(APEC) strains frequently cause extraintestinal infections and are responsible for significant economic losses in the poultry industry worldwide. APEC isolates are closely related to human extraintestinal pathogenic
E. coli
(ExPEC) strains and may also act as pathogens for humans. Known APEC virulence factors include adhesins such as type 1 fimbriae and curli, iron acquisition systems, and cytotoxins. Here we show that APEC strain SEPT362, isolated from a septicemic hen, expresses a type VI secretion system (T6SS); causes cytoskeleton rearrangements; and invades epithelial cells, replicates within macrophages, and causes lethal disease in chicks. To assess the contribution of the T6SS to SEPT362 pathogenesis, we generated two mutants,
hcp
(which encodes a protein suggested to be both secreted and a structural component of the T6SS) and
clpV
(encoding the T6SS ATPase). Both mutants showed decreased adherence and actin rearrangement on epithelial cells. However, only the
hcp
mutant presented a mild decrease in its ability to invade epithelial cells, and none of these mutants were defective for intramacrophage replication. Transcriptome studies showed that the level of expression of type 1 fimbriae was decreased in these mutants, which may account for the diminished adhesion and invasion of epithelial cells. The T6SS seems to be important for the disease process, given that both mutants were attenuated for infection in chicks. These results suggest that the T6SS influences the expression of type 1 fimbriae and contributes to APEC pathogenesis.
Znu Is the Predominant Zinc Importer in
Yersinia pestis
during
In Vitro
Growth but Is Not Essential for Virulence
Authors: Desrosiers Daniel C. , Bearden Scott W. , Mier Ildefonso , Abney Jennifer , Paulley James T. , Fetherston Jacqueline D. , Salazar Juan C. , Radolf Justin D. , Perry Robert D. 
Published: September 2010

ABSTRACT

Little is known about Zn homeostasis in
Yersinia pestis
, the plague bacillus. The Znu ABC transporter is essential for zinc (Zn) uptake and virulence in a number of bacterial pathogens. Bioinformatics analysis identified ZnuABC as the only apparent high-affinity Zn uptake system in
Y. pestis
. Mutation of
znuACB
caused a growth defect in Chelex-100-treated PMH2 growth medium, which was alleviated by supplementation with submicromolar concentrations of Zn. Use of transcriptional reporters confirmed that Zur mediated Zn-dependent repression and that it can repress gene expression in response to Zn even in the absence of Znu. Virulence testing in mouse models of bubonic and pneumonic plague found only a modest increase in survival in low-dose infections by the
znuACB
mutant. Previous studies of cluster 9 (C9) transporters suggested that Yfe, a well-characterized C9 importer for manganese (Mn) and iron in
Y. pestis
, might function as a second, high-affinity Zn uptake system. Isothermal titration calorimetry revealed that YfeA, the solute-binding protein component of Yfe, binds Mn and Zn with comparably high affinities (dissociation constants of 17.8 ± 4.4 nM and 6.6 ± 1.2 nM, respectively), although the complete Yfe transporter could not compensate for the loss of Znu in
in vitro
growth studies. Unexpectedly, overexpression of Yfe interfered with the
znu
mutant's ability to grow in low concentrations of Zn, while excess Zn interfered with the ability of Yfe to import iron at low concentrations; these results suggest that YfeA can bind Zn in the bacterial cell but that Yfe is incompetent for transport of the metal. In addition to Yfe, we have now eliminated MntH, FetMP, Efe, Feo, a substrate-binding protein, and a putative nickel transporter as the unidentified, secondary Zn transporter in
Y. pestis.
Unlike other bacterial pathogens,
Y. pestis
does not require Znu for high-level infectivity and virulence; instead, it appears to possess a novel class of transporter, which can satisfy the bacterium's Zn requirements under
in vivo
metal-limiting conditions. Our studies also underscore the need for bacterial cells to balance binding and transporter specificities within the periplasm in order to maintain transition metal homeostasis.
Serotype-Related Variation in Susceptibility to Complement Deposition and Opsonophagocytosis among Clinical Isolates of
Streptococcus pneumoniae
Authors: Melin Merit , Trzciński Krzysztof , Antonio Martin , Meri Seppo , Adegbola Richard , Kaijalainen Tarja , Käyhty Helena , Väkeväinen Merja 
Published: September 2010

ABSTRACT

The polysaccharide capsule is a major virulence factor of
Streptococcus pneumoniae
; it affects complement resistance and shields the bacterium from phagocytes. Certain capsular serotypes appear to be better able to cause invasive disease than others. Serotypes 1 and 5 are common causes of invasive disease but are rarely isolated from healthy carriers, whereas serotypes 6B and 23F are more frequently isolated from carriage than invasive disease. We have recently shown that serotypes 6B and 19F differ in resistance to complement C3 deposition and opsonophagocytic killing. In this study we assessed the complement resistance and susceptibility to opsonophagocytosis of several other serotypes targeted by the pneumococcal conjugate vaccines. Clinical isolates of serotypes 1, 4, 5, 14, 18C, and 23F were tested along reference strains of corresponding capsular types. The concentration of anticapsular antibodies required for opsonophagocytic killing correlated inversely with C3 deposition on the serotype. Serotype 1 was the most resistant of the clinical isolates to C3 deposition and, along with serotypes 5 and 19F, required the highest concentration of capsule antibodies for opsonophagocytic killing, whereas serotype 23F was the most sensitive to opsonophagocytosis. Sensitivity to C3 deposition and opsonophagocytosis was associated with serotype-specific mortality of invasive pneumococcal disease, suggesting that the primary pathogens, such as serotypes 1 and 5, are more resistant to complement and require a higher concentration of capsule antibodies for opsonophagocytic killing than the opportunistic serotypes such as 6B and 23F, which are associated with a more severe disease outcome.
Characterization of an Archaeal Medium-Chain Acyl Coenzyme A Synthetase fromMethanosarcina acetivorans
Authors: Meng Yu , Ingram-Smith Cheryl , Cooper Leroy L. , Smith Kerry S. 
Published: September 2010

ABSTRACTShort- and medium-chain acyl coenzyme A (acyl-CoA) synthetases catalyze the formation of acyl-CoA from an acyl substrate, ATP, and CoA. These enzymes catalyze mechanistically similar two-step reactions that proceed through an enzyme-bound acyl-AMP intermediate. Here we describe the characterization of a member of this enzyme family from the methane-producing archaeonMethanosarcina acetivorans. This enzyme, a medium-chain acyl-CoA synthetase designated MacsMa, utilizes 2-methylbutyrate as its preferred substrate for acyl-CoA synthesis but cannot utilize acetate and thus cannot catalyze the first step of acetoclastic methanogenesis inM. acetivorans. When propionate or other less favorable acyl substrates, such as butyrate, 2-methylpropionate, or 2-methylvalerate, were utilized, the acyl-CoA was not produced or was produced at reduced levels. Instead, acyl-AMP and PPiwere released in the absence of CoA, whereas in the presence of CoA, the intermediate was broken down into AMP and the acyl substrate, which were released along with PPi. These results suggest that although acyl-CoA synthetases may have the ability to utilize a broad range of substrates for the acyl-adenylate-forming first step of the reaction, the intermediate may not be suitable for the thioester-forming second step. The MacsMastructure has revealed the putative acyl substrate- and CoA-binding pockets. Six residues proposed to form the acyl substrate-binding pocket, Lys256, Cys298, Gly351, Trp259, Trp237, and Trp254, were targeted for alteration. Characterization of the enzyme variants indicates that these six residues are critical in acyl substrate binding and catalysis, and even conservative alterations significantly reduced the catalytic ability of the enzyme.
Calcium and Iron Regulate Swarming and Type III Secretion inVibrio parahaemolyticus
Authors: Gode-Potratz Cindy J. , Chodur Daniel M. , McCarter Linda L. 
Published: September 2010

ABSTRACTHere, we probe the response to calcium during growth on a surface and show that calcium influences the transcriptome and stimulates motility and virulence ofVibrio parahaemolyticus.Swarming (but not swimming) gene expression and motility were enhanced by calcium. Calcium also elevated transcription of one of the organism's two type III secretion systems (T3SS1 but not T3SS2) and heightened cytotoxicity toward host cells in coculture. Calcium stimulation of T3SS gene expression has not been reported before, although low calcium is an inducing signal for the T3SS of many organisms. EGTA was also found to increase T3SS1 gene expression and virulence; however, this was demonstrated to be the consequence of iron rather than calcium chelation. Ectopic expression ofexsA, encoding the T3SS1 AraC-type regulator, was used to define the extent of the T3SS1 regulon and verify its coincident induction by calcium and EGTA. To begin to understand the regulatory mechanisms modulating the calcium response, a calcium-repressed, LysR-type transcription factor named CalR was identified and shown to repress swarming and T3SS1 gene expression. Swarming and T3SS1 gene expression were also demonstrated to be linked by LafK, a σ54-dependent regulator of swarming, and additionally connected by a negative-feedback loop on the swarming regulon propagated by ExsA. Thus, calcium and iron, two ions pertinent for a marine organism and pathogen, play a signaling role with global consequences on the regulation of gene sets that are relevant for surface colonization and infection.
A
Rhodobacter capsulatus
Member of a Universal Permease Family Imports Molybdate and Other Oxyanions
Authors: Gisin Jonathan , Müller Alexandra , Pfänder Yvonne , Leimkühler Silke , Narberhaus Franz , Masepohl Bernd 
Published: September 2010

ABSTRACT

Molybdenum (Mo) is an important trace element that is toxic at high concentrations. To resolve the mechanisms underlying Mo toxicity,
Rhodobacter capsulatus
mutants tolerant to high Mo concentrations were isolated by random transposon Tn
5
mutagenesis. The insertion sites of six independent isolates mapped within the same gene predicted to code for a permease of unknown function located in the cytoplasmic membrane. During growth under Mo-replete conditions, the wild-type strain accumulated considerably more Mo than the permease mutant. For mutants defective for the permease, the high-affinity molybdate importer ModABC, or both transporters,
in vivo
Mo-dependent nitrogenase (Mo-nitrogenase) activities at different Mo concentrations suggested that ModABC and the permease import molybdate in nanomolar and micromolar ranges, respectively. Like the permease mutants, a mutant defective for ATP sulfurylase tolerated high Mo concentrations, suggesting that ATP sulfurylase is the main target of Mo inhibition in
R. capsulatus
. Sulfate-dependent growth of a double mutant defective for the permease and the high-affinity sulfate importer CysTWA was reduced compared to those of the single mutants, implying that the permease plays an important role in sulfate uptake. In addition, permease mutants tolerated higher tungstate and vanadate concentrations than the wild type, suggesting that the permease acts as a general oxyanion importer. We propose to call this permease PerO (for oxyanion permease). It is the first reported bacterial molybdate transporter outside the ABC transporter family.
The Methanogen-Specific Transcription Factor MsvR Regulates the
fpaA-rlp-rub
Oxidative Stress Operon Adjacent to
msvR
in
Methanothermobacter thermautotrophicus
Authors: Karr Elizabeth A. 
Published: September 2010

ABSTRACT

Methanogens represent some of the most oxygen-sensitive organisms in laboratory culture. Recent studies indicate that they have developed mechanisms to deal with brief oxygen exposure. MsvR is a transcriptional regulator that has a domain architecture unique to a select group of methanogens. Here, runoff
in vitro
transcription assays were used to demonstrate that MsvR regulates transcription of the divergently transcribed
fpaA-rlp-rub
operon in
Methanothermobacter thermautotrophicus
in addition to transcription from its own promoter. The protein products of the
fpaA-rlp-rub
operon have previously been implicated in oxidative stress responses in
M. thermautotrophicus
. Additionally, electrophoretic mobility shift assays (EMSAs) and DNase I footprinting were used to confirm a binding site inferred by bioinformatic analysis. Sequence mutations within these binding sites did not significantly alter EMSA shifting patterns on longer templates but did on shorter 50-bp fragments encompassing only the region containing the binding sites. Footprinting confirmed that the regions protected for the longer mutant templates are at different positions within the intergenic region compared to those seen in the intact intergenic region. Oxidized and reduced preparations of MsvR demonstrated different EMSA binding patterns and regions of protection on the intergenic sequence, suggesting that MsvR may play a role in detecting the redox state of the cell.
Characterization of Pgp3, aChlamydia trachomatisPlasmid-Encoded Immunodominant Antigen
Authors: Chen Ding , Lei Lei , Lu Chunxue , Galaleldeen Ahmad , Hart P. John , Zhong Guangming 
Published: September 2010

ABSTRACTHuman antibody recognition ofChlamydia trachomatisplasmid-encoded Pgp3 protein is dependent on the native conformation of Pgp3. The structural basis for the conformation dependence and the function of Pgp3 remain unknown. Here, we report that Pgp3 trimerization is required for the recognition of Pgp3 by human antibodies. In a native polyacrylamide gel, Pgp3 purified from a bacterial expression system migrated as stable trimers that were dissociated into monomers only by treatment with urea or sodium dodecyl sulfate (SDS) but not nonionic detergents. Human antibodies recognized trimeric but not monomeric Pgp3, suggesting that Pgp3 is presented to the human immune system as trimers duringC. trachomatisinfection. The endogenous Pgp3 secreted into the chlamydial outer membrane complex or host cell cytosol is always trimerized. Intact Pgp3 trimers were eluted from the outer membrane complex by a combination of nonionic detergents with reducing agents but not by the presence of either alone. These observations have provided important information for further understanding the role of Pgp3 in chlamydial pathogenesis and potentially optimizing Pgp3 as a subunit vaccine candidate antigen.
Complete Genome Sequence of the Cellulolytic Thermophile
Caldicellulosiruptor obsidiansis
OB47
T
Authors: Elkins James G. , Lochner Adriane , Hamilton-Brehm Scott D. , Davenport Karen Walston , Podar Mircea , Brown Steven D. , Land Miriam L. , Hauser Loren J. , Klingeman Dawn M. , Raman Babu , Goodwin Lynne A. , Tapia Roxanne , Meincke Linda J. , Detter J. Chris , Bruce David C. , Han Cliff S. , Palumbo Anthony V. , Cottingham Robert W. , Keller Martin , Graham David E. 
Published: September 2010

ABSTRACT

Caldicellulosiruptor obsidiansis
OB47
T
(ATCC BAA-2073, JCM 16842) is an extremely thermophilic, anaerobic bacterium capable of hydrolyzing plant-derived polymers through the expression of multidomain/multifunctional hydrolases. The complete genome sequence reveals a diverse set of carbohydrate-active enzymes and provides further insight into lignocellulosic biomass hydrolysis at high temperatures.
Genome Sequence of the Polymyxin-Producing Plant-Probiotic Rhizobacterium
Paenibacillus polymyxa
E681
Authors: Kim Jihyun F. , Jeong Haeyoung , Park Soo-Young , Kim Seong-Bin , Park Yon Kyoung , Choi Soo-Keun , Ryu Choong-Min , Hur Cheol-Goo , Ghim Sa-Youl , Oh Tae Kwang , Kim Jae Jong , Park Chang Seuk , Park Seung-Hwan 
Published: September 2010

ABSTRACT

Paenibacillus polymyxa
E681, a spore-forming, low-G+C, Gram-positive bacterium isolated from the rhizosphere of winter barley grown in South Korea, has great potential for agricultural applications due to its ability to promote plant growth and suppress plant diseases. Here we present the complete genome sequence of
P. polymyxa
E681. Its 5.4-Mb genome encodes functions specialized to the plant-associated lifestyle and characteristics that are beneficial to plants, such as the production of a plant growth hormone, antibiotics, and hydrolytic enzymes.
The geochemistry and petrography of the Coastal Batholith of Peru, Lima segment
Authors: Mccourt W.J. 
Published: September 2010

Abstract:
SUMMARY: The Coastal Batholith of Peru, Lima segment, is a composite batholith made up of at least 8 time-separated magmatic events. The evolution of the batholith is such that the amount of granitic magma apparently increases with decreasing age, which is reflected in an overall basic to acid sequence of intrusion. High-level differentiation, involving plagioclase and hornblende as the major precipitating phases, is the prime cause of the chemical variation within each suite of rocks, all of which are distinguished by strong calc-alkaline character. The geochemical and petrographical evidence suggests that the batholith magmas were undersaturated with respect to water throughout most of their crystallization histories. Preliminary isotopic studies indicate that the parent magmas to individual super-units originated by partial melting, either in the mantle or in a crustal underplate zone.
Overexpression of High-Mobility Group Box 2 Is Associated with Tumor Aggressiveness and Prognosis of Hepatocellular Carcinoma
Authors: Kwon Jung-Hee , Kim Jongmin , Park Jin Young , Hong Sun Mi , Park Chang Wook , Hong Seok Joo , Park Sun Young , Choi Yoon Jung , Do In-Gu , Joh Jae-Won , Kim Dae Shick , Choi Kwan Yong 
Published: September 2010

Abstract
Purpose: We investigated the expression of high-mobility group box 2 (HMGB2) in patients with hepatocellular carcinoma (HCC) and its clinical effects with underlying mechanisms.
Experimental Design: HMGB2 mRNA levels were measured in 334 HCC patients by real-time reverse transcription-PCR and HMGB2 protein levels in 173 HCC patients by immunohistochemical studies. The HMGB2 expression level was measured by Western blotting for three HCC cell lines. To clarify the precise role of HMGB2 on cell proliferation, we did in vitro analysis with expression vectors and small interfering RNAs.
Results: HMGB2 mRNA and protein expression were significantly higher in HCC than in noncancerous surrounding tissues (P &lt; 0.0001) and showed a positive correlation (ρ = 0.35, P &lt; 0.001). HMGB2 overexpression was significantly correlated with shorter overall survival time, both at mRNA (P = 0.0054) and protein level (P = 0.023). Moreover, HMGB2 mRNA level was an independent prognostic factor for overall survival in a multivariate analysis (P = 0.0037). HMGB2 knockdown by small interfering RNAs decreased cell proliferation, and overexpression of HMGB2 by expression vectors diminished cisplatin- and etoposide-induced cell death.
Conclusions: Our clinical and in vitro data suggest that HMGB2 plays a significant role in tumor development and prognosis of HCC. These results can partly be explained by altered cell proliferations by HMGB2 associated with the antiapoptotic pathway. Clin Cancer Res; 16(22); 5511–21. ©2010 AACR.
Curcumin Inhibits Carcinogen and Nicotine-Induced Mammalian Target of Rapamycin Pathway Activation in Head and Neck Squamous Cell Carcinoma
Authors: Clark Cheryl A. , McEachern Matthew D. , Shah Shivang H. , Rong Youhua , Rong Xiaohua , Smelley Christopher L. , Caldito Gloria C. , Abreo Fleurette W. , Nathan C.O. 
Published: September 2010

Abstract
Curcumin appears to be a safe, bioactive food compound that is a potential chemopreventive for patients at a high risk for head and neck squamous cell carcinoma (HNSCC). Identification and validation of intermediate endpoints is an important step in evaluating chemopreventive agents. AKT/MTOR pathway biomarkers are intrinsic to the carcinogenic process as well as the mechanism of intervention with curcumin. Antiproliferative effects of curcumin were assayed in 9 HNSCC and a keratinocyte cell line. Nicotine, a genotoxic alkaloid involved in tobacco addiction, forms DNA adducts and has been implicated in upper aerodigestive tract cancer promotion. The antiproliferative effects of curcumin were associated with inhibition of the AKT/MTOR pathway in presence and absence of nicotine, which also induced this pathway. Curcumin was highly effective at suppressing growth of SCC40 xenografts and its activity is associated with modulation of MTOR's downstream target pS6. Curcumin at 15 mg significantly increased survival (286 ± 37 vs. 350 days) in the 4NQO carcinogenic model survival study. A major cause of lethal progression of HNSCC is local regional migration and invasion of malignant cells, and curcumin significantly inhibited cancer cell migration and invasion in vitro and in vivo where downregulation of pS6 was associated with a significant decrease in MMP-9. This is the first study to demonstrate that curcumin inhibits the adverse effects of nicotine by blocking nicotine-induced activation of the AKT/MTOR pathway in HNSCC, which retards cell migration. These studies indicate that inhibiting the AKT/MTOR pathway with curcumin may be useful as an oral chemopreventive agent. Cancer Prev Res; 3(12); 1586–95. ©2010 AACR.
Idiopathic Ventricular Arrhythmias Originating From the Left Ventricular Summit
Authors: Yamada Takumi , McElderry H. Thomas , Doppalapudi Harish , Okada Taro , Murakami Yoshimasa , Yoshida Yukihiko , Yoshida Naoki , Inden Yasuya , Murohara Toyoaki , Plumb Vance J. , Kay G. Neal 
Published: September 2010

Background—
The summit of the left ventricle (LV) is the most superior portion of the epicardial LV bounded by an arc from the left anterior descending coronary artery, superior to the first septal perforating branch to the left circumflex coronary artery. Ventricular arrhythmias (VAs) originating from this region may present challenges for catheter ablation.

Methods and Results—

We studied 27 consecutive patients with VAs originating from the LV summit. The great cardiac vein (GCV) divides this region between an inferior area accessible to ablation and a superior, inaccessible area. Successful ablation was achieved within the GCV in 14 patients and on the epicardial surface in 4. Ventricular prepotentials were recorded at the successful ablation site in 80% of these patients. In 5 patients, ablation was abandoned because of inaccessibility of the catheter to the myocardium or high impedance with radiofrequency application within the GCV. In the remaining 4 patients, epicardial mapping suggested VA origins in a region of low voltage that was located superior to the GCV (inaccessible area), and ablation was abandoned because of close proximity to the coronary arteries or high impedance. A right bundle-branch block, transition zone, R-wave amplitude ratio in leads III to II, Q-wave amplitude ratio in leads aVL to aVR, and S waves in lead V
6
accurately predicted the site of origin.

Conclusions—
LV summit VAs may be ablated within the GCV or inferior to the GCV on the epicardial surface, though sites superior to the GCV are usually inaccessible to ablation.