bluuebunny/crossref_metadata_2025_split huggingface dataset:
CytochromedBut Not CytochromeoRescues the Toluidine Blue Growth Sensitivity ofarcMutants ofEscherichia coli
Authors: Alvarez Adrian F. , Malpica Roxana , Contreras Martha , Escamilla Edgardo , Georgellis Dimitris 
Published: November 2009

ABSTRACTThe Arc (anoxic redox control) two-component signal transduction system, consisting of the ArcB sensor kinase and the ArcA response regulator, allows adaptive responses ofEscherichia colito changes of O2availability. ThearcAgene was previously known as thedyegene because null mutants were growth sensitive to the photosensitizer redox dyes toluidine blue and methylene blue, a phenotype whose molecular basis still remains elusive. In this study we report that the toluidine blue O (TBO) effect on thearcmutants is light independent and observed only during aerobic growth conditions. Moreover, 16 suppressor mutants with restored growth were generated and analyzed. Thirteen of those possessed insertion elements upstream of thecydABoperon, rendering its expression ArcA independent. Also, it was found that, in contrast to cythocromed, cythocromeowas not able to confer toluidine blue resistance toarcmutants, thereby representing an intriguing difference between the two terminal oxidases. Finally, a mechanism for TBO sensitivity and resistance is discussed.
Polar Localization of the CckA Histidine Kinase and Cell Cycle Periodicity of the Essential Master Regulator CtrA in
Caulobacter crescentus
Authors: Angelastro Peter S. , Sliusarenko Oleksii , Jacobs-Wagner Christine 
Published: November 2009

ABSTRACT

The phosphorylated form of the response regulator CtrA represses DNA replication initiation and regulates the transcription of about 100 cell cycle-regulated genes in
Caulobacter crescentus
. CtrA activity fluctuates during the cell cycle, and its periodicity is a key element of the engine that drives cell cycle progression. The histidine kinase CckA controls the phosphorylation not only of CtrA but also of CpdR, whose unphosphorylated form promotes CtrA proteolysis. Thus, CckA has a central role in establishing the cell cycle periodicity of CtrA activity by controlling both its phosphorylation and stability. Evidence suggests that the polar localization of CckA during the cell cycle plays a role in CckA function. However, the exact pattern of CckA localization remains controversial. Here, we describe a thorough, quantitative analysis of the spatiotemporal distribution of a functional and chromosomally produced CckA-monomeric green fluorescent protein fusion that affects current models of cell cycle regulation. We also identify two
cis
-acting regions in CckA that are important for its proper localization and function. The disruption of a PAS-like motif in the sensor domain affects the stability of CckA accumulation at the poles. This is accompanied by a partial loss in CckA function. Shortening an extended linker between β-sheets within the CckA catalysis-assisting ATP-binding domain has a more severe effect on CckA polar localization and function. This mutant strain exhibits a dramatic cell-to-cell variability in CpdR levels and CtrA cell cycle periodicity, suggesting that the cell cycle-coordinated polar localization of CckA may be important for the robustness of signal transduction and cell cycle progression.
The Aromatic Ring of Phenylalanine 334 Is Essential for Oligomerization ofVibrio vulnificusHemolysin
Authors: Kashimoto Takashige , Ueno Shunji , Koga Takeshi , Fukudome Shinji , Ehara Hayato , Komai Mayumi , Sugiyama Hiroyuki , Susa Nobuyuki 
Published: November 2009

ABSTRACTVibrio vulnificushemolysin (VVH) is thought to be a member of the cholesterol-dependent cytolysin (CDC) family of pore-forming toxins. To date, the structure-function relationships of CDCs produced by Gram-negative bacteria remain largely unknown. We show here that the aromatic ring of phenylalanine residue conserved inVibrionaceaehemolysins is essential for oligomerization of VVH. We generated the VVH mutants; substituted Phe 334 for Ile (F334I), Ala (F334A), Tyr (F334Y), or Trp (F334W); and tested their binding and oligomerizing activity on Chinese hamster ovary cells. Binding in all mutants fell by approximately 50% compared with that in the wild type. Oligomerizing activities were completely eliminated in F334I and F334A mutants, whereas this ability was partially retained in F334Y and F334W mutants. These findings indicate that both hydrophobicity and an aromatic ring residue at the 334th position were needed for full binding activity and that the oligomerizing activity of this toxin was dependent on the existence of an aromatic ring residue at the 334th position. Our findings might help further understanding of the structure-and-function relationships inVibrionaceaehemolysins.
Genomic and Biological Analysis of Phage Xfas53 and Related Prophages of
Xylella fastidiosa
Authors: Summer Elizabeth J. , Enderle Christopher J. , Ahern Stephen J. , Gill Jason J. , Torres Cruz P. , Appel David N. , Black Mark C. , Young Ry , Gonzalez Carlos F. 
Published: November 2009

ABSTRACT

We report the plaque propagation and genomic analysis of Xfas53, a temperate phage of
Xylella fastidiosa
. Xfas53 was isolated from supernatants of
X. fastidiosa
strain 53 and forms plaques on the sequenced strain Temecula. Xfas53 forms short-tailed virions, morphologically similar to podophage P22. The 36.7-kb genome is predicted to encode 45 proteins. The Xfas53 terminase and structural genes are related at a protein and gene order level to P22. The left arm of the Xfas53 genome has over 90% nucleotide identity to multiple prophage elements of the sequenced
X. fastidiosa
strains. This arm encodes proteins involved in DNA metabolism, integration, and lysogenic control. In contrast to Xfas53, each of these prophages encodes head and DNA packaging proteins related to the siphophage lambda and tail morphogenesis proteins related to those of myophage P2. Therefore, it appears that Xfas53 was formed by recombination between a widespread family of
X. fastidiosa
P2-related prophage elements and a podophage distantly related to phage P22. The lysis cassette of Xfas53 is predicted to encode a pinholin, a signal anchor and release (SAR) endolysin, and Rz and Rz1 equivalents. The holin gene encodes a pinholin and appears to be subject to an unprecedented degree of negative regulation at both the level of expression, with rho-independent transcriptional termination and RNA structure-dependent translational repression, and the level of holin function, with two upstream translational starts predicted to encode antiholin products. A notable feature of Xfas53 and related prophages is the presence of 220- to 390-nucleotide degenerate tandem direct repeats encoding putative DNA binding proteins. Additionally, each phage encodes at least two BroN domain-containing proteins possibly involved in lysogenic control. Xfas53 exhibits unusually slow adsorption kinetics, possibly an adaptation to the confined niche of its slow-growing host.
FolX and FolM Are Essential for Tetrahydromonapterin Synthesis in
Escherichia coli
and
Pseudomonas aeruginosa
Authors: Pribat Anne , Blaby Ian K. , Lara-Núñez Aurora , Gregory Jesse F. , de Crécy-Lagard Valérie , Hanson Andrew D. 
Published: November 2009

ABSTRACT

Tetrahydromonapterin is a major pterin in
Escherichia coli
and is hypothesized to be the cofactor for phenylalanine hydroxylase (PhhA) in
Pseudomonas aeruginosa
, but neither its biosynthetic origin nor its cofactor role has been clearly demonstrated. A comparative genomics analysis implicated the enigmatic
folX
and
folM
genes in tetrahydromonapterin synthesis via their phyletic distribution and chromosomal clustering patterns.
folX
encodes dihydroneopterin triphosphate epimerase, which interconverts dihydroneopterin triphosphate and dihydromonapterin triphosphate.
folM
encodes an unusual short-chain dehydrogenase/reductase known to have dihydrofolate and dihydrobiopterin reductase activity. The roles of FolX and FolM were tested experimentally first in
E. coli
, which lacks PhhA and in which the expression of
P. aeruginosa
PhhA plus the recycling enzyme pterin 4a-carbinolamine dehydratase, PhhB, rescues tyrosine auxotrophy. This rescue was abrogated by deleting
folX
or
folM
and restored by expressing the deleted gene from a plasmid. The
folX
deletion selectively eliminated tetrahydromonapterin production, which far exceeded folate production. Purified FolM showed high, NADPH-dependent dihydromonapterin reductase activity. These results were substantiated in
P. aeruginosa
by deleting
tyrA
(making PhhA the sole source of tyrosine) and
folX
. The Δ
tyrA
strain was, as expected, prototrophic for tyrosine, whereas the Δ
tyrA
Δ
folX
strain was auxotrophic. As in
E. coli
, the
folX
deletant lacked tetrahydromonapterin. Collectively, these data establish that tetrahydromonapterin formation requires both FolX and FolM, that tetrahydromonapterin is the physiological cofactor for PhhA, and that tetrahydromonapterin can outrank folate as an end product of pterin biosynthesis.
Promoter and Riboswitch Control of the Mg
2+
Transporter MgtA from
Salmonella enterica
Authors: Cromie Michael J. , Groisman Eduardo A. 
Published: November 2009

ABSTRACT

The MgtA protein from
Salmonella enterica
serovar Typhimurium mediates Mg
2+
uptake from the periplasm into the cytoplasm. Here we report that the PhoP/PhoQ two-component regulatory system, which responds to periplasmic Mg
2+
, governs
mgtA
transcription initiation at all investigated Mg
2+
concentrations and that the Mg
2+
-sensing 5′ leader region of the
mgtA
gene controls transcription elongation into the
mgtA
coding region when
Salmonella
is grown in media with <50 μM Mg
2+
. Overexpression of the Mg
2+
transporter CorA, which is believed to increase cytoplasmic Mg
2+
levels, decreased
mgtA
transcription in a manner dependent on a functional
mgtA
5′ leader.
P1 Plasmid Segregation: Accurate Redistribution by Dynamic Plasmid Pairing and Separation
Authors: Sengupta Manjistha , Nielsen Henrik Jorck , Youngren Brenda , Austin Stuart 
Published: November 2009

ABSTRACTLow-copy-number plasmids, such as P1 and F, encode a type Ia partition system (P1paror Fsop) for active segregation of copies to daughter cells. Typical descriptions show a single central plasmid focus dividing and the products moving to the cell quarter regions, ensuring segregation. However, using improved optical and analytical tools and large cell populations, we show that P1 plasmid foci are very broadly distributed. Moreover, under most growth conditions, more than two foci are frequently present. Each focus contains either one or two plasmid copies. Replication and focus splitting occur at almost any position in the cell. The products then move rapidly apart for approximately 40% of the cell length. They then tend to maintain their relative positions. The segregating foci often pass close to or come to rest close to other foci in the cell. Foci frequently appear to fuse during these encounters. Such events occur several times in each cell and cell generation on average. We argue that foci pair with their neighbors and then actively separate again. The net result is an approximately even distribution of foci along the long cell axis on average. We show mathematically thattrans-pairing and active separation could greatly increase the accuracy of segregation and would produce the distributions of foci that we observe. Plasmid pairing and separation may constitute a novel fine-tuning mechanism that takes the basic pattern created when plasmids separate after replication and converts it to a roughly even pattern that greatly improves the fidelity of plasmid segregation.
Research, Participation, and the Teaching of Politics
Authors: Matthews Donald R. 
Published: November 2009

The director of the Political Studies Program at the University of North Carolina discusses the program's outstanding features. Both graduate and under-graduate courses in American government and politics have accompanying laboratory sessions that permit student observation and participation in politics in a research-oriented situation. Begun in 1957, the program has already had excellent results. The following article discusses another aspect of social science research at North Carolina.
Changes in Vacation Travel in Response to Motor Fuel Shortages and Higher Prices
Authors: Corsi Thomas M. , Harvey Milton E. 
Published: November 2009

This study presents findings from a survey administered in November 1975 among a sample of households in southeastern Wisconsin to determine, among other things, the shifts in travel vacations that occurred in response to the higher fuel prices that developed between 1973 and 1975 and that might occur in response to the alternative futures of still higher fuel prices and restricted fuel availability. Specific socioeconomic variables significantly distinguished between households that changed vacation plans and those that did not make changes between 1973 and 1975. We found that the following variables significantly influenced vacation travel: occupation of the household head, household income, education level of the household head, age of the household head, number of children in the household aged 15 and under, and geographic location of the household. Under futuristic alternatives of either higher prices or restructed fuel availability households were willing to experiment with various vacation adjustment strategies. This indicates a lack of clear preference among households for any one strategy.
An Assessment of the Image of Mexico as a Vacation Destination and the Influence of Geographical Location Upon That Image
Authors: Crompton John L. 
Published: November 2009

A sample of 617 student respondents was drawn from 12 universities, in different parts of the United States. Semantic differential instruments were used to measure respondents' descriptive and importance dimensions of thei.- image of Mexico. The analysis indicated major differences between the two image dimensions. Those image attributes which respondents considered to be important when considering a vacation in Mexico were related primarily to sanitation and safety. The most positive attributes respondents reported about Mexico related to climate and low costs. Measurement of respondents' descriptive image of Mexico indicated that the farther away respondents resided from Mexico, the more favorable was their image of that country as a vacation destination. Analysis indicated that the regional differences were not significant. However, significant differences were found on 12 of the 30 individual attributes which were used to measure image.
Pyrolysis of Polymers
Authors: Wall Leo A. 
Published: November 2009

The nature of their pyrolysis products, monomer, oligomers and carbonaceous residues enables one to group polymers into three classes, those that decompose by net main chain scission; by stripping of the main chain, for example the thermal dehydrochlorination of polyvinyl chloride; and by crosslinking of the main chain followed by some production of volatiles. Highly unsaturated or aromatic chains tend to follow the latter course. At the present time a theoretical framework exists which permits, provided adequate experiments are performed, the elucidation of the decompositions of the first type. For most of the well-known polymers in this class, this framework of knowledge gives very acceptable mechanistic explanations or interpretations of the decomposition process based on observations of rate of weight loss, of molecular weight changes and composition of volatile products. Knowledge of the decomposition of the second class of polymers is at an intermediate state development. However, an important practical research objective would be the acquisition of methods for converting the mechanisms of decomposition of class one substances to that for class two type. For the third class of materials, knowledge of their pyrolysis mechanisms is nonexistent. This is largely due to the fact that methods for quantitatively following solid-phase processes of decomposition are relatively difficult and unsatisfactory.
Nylon 6/Graphite Fiber Composites by in Situ Polymerization
Authors: Litt Morton H. , Brinkmann Allan W. 
Published: November 2009

The in situ polymerization of caprolactam to Nylon 6 was investigated as a method for making graphite fiber composites. It was necessary to find a co-catalyst (using sodium caprolactam as catalyst) which could be mixed at about 100°C and where the final mixture had a long enough pot life to allow for mixing and application to the fibers. The temperature could then be raised to 200°C to initiate rapid polymerization. Co-catalysts tested were all esters as these had earlier been shown to have appropriate lifetimes. They were phenyl acetate, benzyl acetate, benzyl benzoate, t-butyl acetate and ∈-caprolactone. Benzyl derivatives gave brittle polymerizates, while the others gave tough materials. Phenyl was excluded as potentially reacting too rapidly. t-Butyl gave good polymers at 190°C but expanded into a foam when heated to 210° due to volatilization of the t-butanol. ∈-Caprolactone initiated well and produced no residues, so it was chosen as the major co-catalyst. Jigs were designed on which graphitic fiber could be wound at various tensions. These were put in tubes containing precatalyzed monomer at 100°C. The whole was degassed several times and then heated to 200°C for polymerization. Several samples of composites were made with fiber densities of 25 to 40 volume % using Thornel 50 S and 75 S fibers. The samples still had some voids due to lack of complete penetration of monomer. The samples varied widely in their tensile strengths and moduli due mainly to variations in fiber density, but also to some voids. The best samples achieved about 70% transfer of properties. This is a respectable figure when one considers that these are the first samples made at these fiber densities. Scanning electron microscope photographs show the best samples had excellent adhesion of matrix to fiber. This resulted in essentially no pull-out, and the areas examined showed multiple fracture of fibers at the fracture surface with extensive deformation of the matrix. Such composites should have high impact strength.
1984 Macromarketing Seminar Abstracts
Authors: Klein Thomas A. 
Published: November 2009

The 1984 Macromarketing Seminar was hosted jointly by the University of British Columbia and Simon Fraser University at Vancouver, British Columbia, Canada, August 16-19. Nearly 50 participants met to discuss macromarketing research and theory. The Call for Papers included a special request for work on the role of marketing in economic development. Abstracts of papers formally presented at the seminar follow. Readers wishing complete copies of these papers may request them directly from authors. The Tenth Macromarketing Seminar will be held in Washington, D.C., following the American Marketing Association Educators Conference, in August 1985.
Pentachlorophenol degradation in landfill drainage models
Authors: Kostova Irina , Todorova Ivanka 
Published: November 2009

The paper describes a laboratory experiment on the biological activity of bacterial populations derived from landfill waste and established on granular materials under conditions similar to those in a landfill drainage system. Two perspex laboratory columns were used to model the landfill drainage system. Artificially formulated leachate was recycled through the columns and the composition of the leachate and the gas produced was measured. The objectives of the research are to show that the landfill drainage system model can act as a fixed bed anaerobic reactor producing gas and to investigate the effect of a hazardous chemical, pentachlorophenol in particular, on microbial activity and the potential for its degradation by bacteria. The results have shown that bacteria derived from landfill waste and established once on landfill drainage aggregates have the ability to survive at low levels of activity and rapidly revive after the addition of nutrients in the form of recirculating leachates.
Recognition and Treatment of Acute Aortic Regurgitation
Authors: O'Rourke Robert A. , Walsh Richard A. 
Published: November 2009

Acute aortic regurgitation usually results from infective endocarditis, but is also caused by aortic dissection and trauma to the heart. Most of the left ventricular stroke volume is regurgitated back into the left ventricle; thus, the forward stroke volume to the body and the cardiac output may be severely compromised. An acute increase in left ventricular end-diastolic volume results in a marked increase in left ventricular end-diastolic pressure, and the mitral valve usually closes prematurely. Compensatory tachycardia is the rule and helps to shorten diastole; thus, the time available for aortic regurgitation to occur is reduced, and the cardiac output is often maintained. On physical examination, there is tachycardia; the peripheral arterial pulse shows a rapid rise, but the systolic pressure is normal; the diastolic pressure is normal or even reduced; and the pulse pressure is often normal. The electrocardiogram (ECG) may be normal except for sinus tachycardia and often for nonspecific ST-T changes. The chest roentgenogram usually shows signs of pulmonary venous hypertension or even pulmonary edema. Echocardiography may show vegetations on the aortic valve, prolapse of an aortic leaflet into the left ventricle, and premature mitral valve closure. Doppler echocardiography is useful in detecting the presence of aortic regurgitation. In cases of infective endocarditis, the appropriate antibiotic therapy must be given. Aortic regurgitation due to dissection of the aorta is usually an indication for surgery. In patients with severe aortic regurgitation, available medical therapy includes digitalis, diuretics, and vasodilators. When patients respond dramatically to the use of digitalis, diuretics, and arterial dilators, surgical therapy can be delayed until heart failure and infection are controlled and the patient is more stable. If the patient does not respond immediately and dramatically to therapy, then valve replacement should not be delayed, even if the infection is uncontrolled or the patient has had little antibiotic therapy.
Outcome of Intensive Care in Patients with the Acquired Immunodeficiency Syndrome
Authors: Rosen Mark J. , Cucco Robert A. , Teirstein Alvin S. 
Published: November 2009

The prognosis of patients who become critically ill due to complications of the acquired immunodeficiency syndrome (AIDS) is generally believed to be poor, but no detailed studies have substantiated this impression. We performed a retrospective analysis of patients with AIDS admitted to the Medical Special Care Unit (MSCU) at Mount Sinai Medical Center in New York over a 42-month period. Of 910 patients admitted to the MSCU, 35 (4% ) had AIDS. An additional patient admitted to the pediatric intensive care unit was included in the analysis. Respiratory failure occurred in 31 patients (86% ) and was the most common problem necessitating admission. Twenty-five of these patients (69% ) had Pneumocystis carinii pneumonia. All 31 patients with respiratory failure required endotracheal intubation and mechanical ventilation, and 27 (87%) died during the same hospitalization. Pneumothorax requiring tube thoracostomy occurred in 6 of 31 patients receiving mechanical ventilatory support. Among the 4 mechanically ventilated survivors, only 2 patients remain alive. Intensive care unit intervention in patients with AIDS and respiratory failure is associated with a poor outcome and probably does not alter the ultimate course in most cases.