bluuebunny/crossref_metadata_2025_split huggingface dataset:
Characterization of PPT
Ns
, a Cyanobacterial Phosphopantetheinyl Transferase from
Nodularia spumigena
NSOR10
Authors: Copp J. N. , Roberts A. A. , Marahiel M. A. , Neilan B. A. 
Published: February 2007

ABSTRACT

The phosphopantetheinyl transferases (PPTs) are a superfamily of essential enzymes required for the synthesis of a wide range of compounds, including fatty acids, polyketides, and nonribosomal peptide metabolites. These enzymes activate carrier proteins in specific biosynthetic pathways by transfer of a phosphopantetheinyl moiety. The diverse PPT superfamily can be divided into two families based on specificity and conserved sequence motifs. The first family is typified by the
Escherichia coli
acyl carrier protein synthase (AcpS), which is involved in fatty acid synthesis. The prototype of the second family is the broad-substrate-range PPT Sfp, which is required for surfactin biosynthesis in
Bacillus subtilis
. Most cyanobacteria do not encode an AcpS-like PPT, and furthermore, some of their Sfp-like PPTs belong to a unique phylogenetic subgroup defined by the PPTs involved in heterocyst differentiation. Here, we describe the first functional characterization of a cyanobacterial PPT based on a structural analysis and subsequent functional analysis of the
Nodularia spumigena
NSOR10 PPT. Southern hybridizations suggested that this enzyme may be the only PPT encoded in the
N. spumigena
NSOR10 genome. Expression and enzyme characterization showed that this PPT was capable of modifying carrier proteins resulting from both heterocyst glycoplipid synthesis and nodularin toxin synthesis. Cyanobacteria are a unique and vast source of bioactive metabolites; therefore, an understanding of cyanobacterial PPTs is important in order to harness the biotechnological potential of cyanobacterial natural products.
Effect of Salt Shock on Stability of λ

imm434

Lysogens
Authors: Shkilnyj Paul , Koudelka Gerald B. 
Published: February 2007

ABSTRACT

The affinities of the bacteriophage 434 repressor for its various binding sites depend on the type and/or concentration of monovalent cations. The ability of bacteriophage 434 repressor to govern the lysis-lysogeny decision depends on the DNA binding activities of the phage's
c
I repressor protein. We wished to determine whether changes in the intracellular ionic environment influence the lysis-lysogeny decision of the bacteriophage λ

imm434

. Our findings show that the ionic composition within bacterial cells varies with the cation concentration in the growth media. When λ

imm434

lysogens were grown to mid-log or stationary phase and subsequently incubated in media with increasing monovalent salt concentrations, we observed a salt concentration-dependent increase in the frequency of bacteriophage spontaneous induction. We also found that the frequency of spontaneous induction varied with the type of monovalent cation in the medium. The salt-dependent increase in phage production was unaffected by a
recA
mutation. These findings indicate that the salt-dependent increase in phage production is not caused by activation of the SOS pathway. Instead, our evidence suggests that salt stress induces this lysogenic bacteriophage by interfering with 434 repressor-DNA interactions. We speculate that the salt-dependent increase in spontaneous induction is due to a direct effect on the repressor's affinity for DNA. Regardless of the precise mechanism, our findings demonstrate that salt stress can regulate the phage lysis-lysogeny switch.
The SXT/R391 Family of Integrative Conjugative Elements Is Composed of Two Exclusion Groups
Authors: Marrero Joeli , Waldor Matthew K. 
Published: February 2007

ABSTRACT
Conjugative elements often encode entry exclusion systems that convert host cells into poor recipients for identical or similar elements. The diversity of exclusion systems within families of conjugative elements has received little attention. We report here the most comprehensive study to date of the diversity of exclusion determinants within a single family of conjugative elements. Unexpectedly, our analyses indicate that there are only two exclusion groups among the diverse members of the SXT/R391 family of integrative conjugative elements.
Transposon Mutagenesis Identifies Sites Upstream of the
Neisseria gonorrhoeae pilE
Gene That Modulate Pilin Antigenic Variation
Authors: Kline Kimberly A. , Criss Alison K. , Wallace Anne , Seifert H. Steven 
Published: February 2007

ABSTRACT

Gene conversion mediates the variation of virulence-associated surface structures on pathogenic microorganisms, which prevents host humoral immune responses from being effective. One of the best-studied gene conversion systems is antigenic variation (Av) of the pilin subunit of the
Neisseria gonorrhoeae
type IV pilus. To identify
cis-
acting DNA sequences that facilitate Av, the 700-bp region upstream of the pilin gene
pilE
was targeted for transposon mutagenesis. Four classes of transposon-associated mutations were isolated, distinguishable by their pilus-associated phenotypes: (i) insertions that did not alter Av or piliation, (ii) insertions that blocked Av, (iii) insertions that interfered with Av, and (iv) insertions that interfered with pilus expression and Av. Mutagenesis of the
pilE
promoter did not affect the frequency of Av, directly demonstrating that pilin Av is independent of
pilE
transcription. Two stretches of sequence upstream of
pilE
were devoid of transposon insertions, and some deletions in these regions were not recoverable, suggesting that they are essential for gonococcal viability. Insertions that blocked pilin Av were located downstream of the RS1 repeat sequence, and deletion of the region surrounding these insertions completely abrogated pilin Av, confirming that specific sequences 5′ to
pilE
are essential for the recombination events underlying pilin Av.
YycH and YycI Interact To Regulate the Essential YycFG Two-Component System in
Bacillus subtilis
Authors: Szurmant Hendrik , Mohan Michael A. , Imus P. Michael , Hoch James A. 
Published: February 2007

ABSTRACT

The YycFG two-component system is the only signal transduction system in
Bacillus subtilis
known to be essential for cell viability. This system is highly conserved in low-G+C gram-positive bacteria, regulating important processes such as cell wall homeostasis, cell membrane integrity, and cell division. Four other genes,
yycHIJK
, are organized within the same operon with
yycF
and
yycG
in
B. subtilis
. Recently, it was shown that the product of one of these genes, the YycH protein, regulated the activity of this signal transduction system, whereas no function could be assigned to the other genes. Results presented here show that YycI and YycH proteins interact to control the activity of the YycG kinase. Strains carrying individual in-frame deletion of the
yycI
and
yycH
coding sequences were constructed and showed identical phenotypes, namely a 10-fold-elevated expression of the YycF-dependent gene
yocH
, growth defects, as well as a cell wall defect. Cell wall and growth defects were a direct result of overregulation of the YycF regulon, since a strain overexpressing YycF showed phenotypes similar to those of
yycH
and
yycI
deletion strains. Both YycI and YycH proteins are localized outside the cytoplasm and attached to the membrane by an N-terminal transmembrane sequence. Bacterial two-hybrid data showed that the YycH, YycI, and the kinase YycG form a ternary complex. The data suggest that YycH and YycI control the activity of YycG in the periplasm and that this control is crucial in regulating important cellular processes.
The Crystal Structure of
Bacillus subtilis
YycI Reveals a Common Fold for Two Members of an Unusual Class of Sensor Histidine Kinase Regulatory Proteins
Authors: Santelli Eugenio , Liddington Robert C. , Mohan Michael A. , Hoch James A. , Szurmant Hendrik 
Published: February 2007

ABSTRACT

YycI and YycH are two membrane-anchored periplasmic proteins that regulate the essential
Bacillus subtilis
YycG histidine kinase through direct interaction. Here we present the crystal structure of YycI at a 2.9-Å resolution. YycI forms a dimer, and remarkably the structure resembles that of the two C-terminal domains of YycH despite nearly undetectable sequence homology (10%) between the two proteins.
Escherichia coli abg
Genes Enable Uptake and Cleavage of the Folate Catabolite
p
-Aminobenzoyl-Glutamate
Authors: Carter Eric L. , Jager Lindsey , Gardner Lars , Hall Christel C. , Willis Stacey , Green Jacalyn M. 
Published: February 2007

ABSTRACT

Escherichia coli
AbgT was first identified as a structural protein enabling the growth of
p
-aminobenzoate auxotrophs on exogenous
p
-aminobenzoyl-glutamate (M. J. Hussein, J. M. Green, and B. P. Nichols, J. Bacteriol. 180:6260-6268, 1998). The
abg
region includes
abgA
,
abgB
,
abgT
, and
ogt
; these genes may be regulated by AbgR, a divergently transcribed LysR-type protein. Wild-type cells transformed with a high-copy-number plasmid encoding
abgT
demonstrate saturable uptake of
p
-aminobenzoyl-glutamate (

K
T

= 123 μM); control cells expressing vector demonstrate negligible uptake. The addition of metabolic poisons inhibited uptake of
p
-aminobenzoyl-glutamate, consistent with this process requiring energy.
p-
Aminobenzoyl-glutamate taken in by cells expressing large amounts of AbgT alone is not rapidly metabolized to a form that is trapped in the cell, as the addition of nonradioactive
p-
aminobenzoyl-glutamate to these cells results in a rapid loss of intracellular label. The addition of nonradioactive
p
-aminobenzoate has no effect. The
abgA
,
abgB
, and
abgAB
genes were cloned into the medium-copy-number plasmid pACYC184;
p
-aminobenzoate auxotrophs transformed with the clone encoding
abgAB
demonstrated enhanced ability to grow on low levels of
p
-aminobenzoyl-glutamate. When transformed with complementary plasmids encoding high-copy levels of
abgT
and medium-copy levels of
abgAB
,
p
-aminobenzoate auxotrophs grew on 50 nM
p
-aminobenzoyl-glutamate. Our data are consistent with a model of
p
-aminobenzoyl-glutamate utilization in which AbgT catalyzes transport of
p
-aminobenzoyl-glutamate, followed by cleavage to
p
-aminobenzoate by a protein composed of subunits encoded by
abgA
and
abgB.
While endogenous expression of these genes is very low under the conditions in which we performed our experiments, these genes may be induced by AbgR bound to an unknown molecule. The true physiological role of this region may be related to some molecule similar to
p
-aminobenzoyl-glutamate, such as a dipeptide.
Cytosolic Proteins Contribute to Surface Plasminogen Recruitment ofNeisseria meningitidis
Authors: Knaust Andreas , Weber Martin V. R. , Hammerschmidt Sven , Bergmann Simone , Frosch Matthias , Kurzai Oliver 
Published: February 2007

ABSTRACTPlasminogen recruitment is a common strategy of pathogenic bacteria and results in a broad-spectrum surface-associated protease activity.Neisseria meningitidishas previously been shown to bind plasminogen. In this study, we show by several complementary approaches that endolase, DnaK, and peroxiredoxin, which are usually intracellular proteins, can also be located in the outer membrane and act as plasminogen receptors. Internal binding motifs, rather than C-terminal lysine residues, are responsible for plasminogen binding of theN. meningitidisreceptors. Recombinant receptor proteins inhibit plasminogen association withN. meningitidisin a concentration-dependent manner. Besides binding purified plasminogen,N. meningitidiscan also acquire plasminogen from human serum. Activation ofN. meningitidis-associated plasminogen by urokinase results in functional activity and allows the bacteria to degrade fibrinogen. Furthermore, plasmin bound toN. meningitidisis protected against inactivation by α2-antiplasmin.
Delayed cord clamping in preterm infants delivered at 34–36 weeks’ gestation: a randomised controlled trial
Authors: Ultee C A , van der Deure J , Swart J , Lasham C , van Baar A L 
Published: February 2007

Background:Even mild iron deficiency and anaemia in infancy may be associated with cognitive deficits. A delay in clamping the cord improves haematocrit levels and results in greater vascular stability and less need for packed cell transfusions for anaemia in the first period after birth. Follow-up data on haemoglobin levels after the neonatal period were not available.Objective:To provide neonatal and follow-up data for the effects of early or delayed clamping of the cord.Methods:37 premature infants (gestational age 34 weeks, 0 days–36 weeks, 6 days) were randomly assigned to one of two groups in the first hour after birth, and at 10 weeks of age. In one group the umbilical cord was clamped within 30 seconds (mean (SD) 13.4 (5.6)) and in the other, it was clamped at 3 minutes after delivery. In the neonatal period blood glucose and haemoglobin levels were determined. At 10 weeks of age haemoglobin and ferritin levels were determined.Results:The late cord-clamped group showed consistently higher haemoglobin levels than the early cord-clamped group, both at the age of 1 hour (mean (SD) 13.4 (1.9) mmol/l vs 11.1 (1.7) mmol/l), and at 10 weeks (6.7 (0.75) mmol/l vs 6.0 (0.65) mmol/l). No relationship between delayed clamping of the umbilical cord and pathological jaundice or polycythaemia was found.Conclusion:Immediate clamping of the umbilical cord should be discouraged.
Continuing education for pathology laboratory technologists: a needs analysis in a Singapore teaching hospital
Authors: Tan Kong-Bing , Thamboo Thomas Paulraj , Lim Yaw-Chyn 
Published: February 2007

Background/Aims:Continuing education is important to laboratory technologists. It helps them keep pace with the advances in medicine and pathology and thus to provide quality service. A survey was conducted to assess the attitudes of pathology laboratory technologists towards different educational activities.Methods:Relevant continuing education activities include lectures, case discussions, journal clubs, short courses, scientific conferences and higher educational courses. Technologists were asked for their views on these various activities, scoring each item 1–5 out of 5.Results:The response rate was 66% (19/29); respondents’ work experience ranged from <3 years to >20 years. Short courses was rated the most highly; 89% of respondents considered them good/excellent. General medical knowledge and the methods and rationale of key histopathology procedures were the preferred lecture topics. Most respondents (58%) were interested (4–5/5) to have their own journal club. 84% of respondents were fairly keen/keen (4–5/5) to participate in conferences. 74% responded that they were fairly keen/keen to consider pursuing higher education. 84% were fairly keen/keen to upgrade themselves and to assume higher responsibilities.Discussion:The results indicate a positive outlook of technologists towards continuing education. The planning of future lecture topics has taken into account their preferences, and talks on the pursuit of higher education have been organised. It is hoped that these measures and others, will help boost the usefulness of continuing education and enhance the work environment.
Creative Work
Authors: Lavery David 
Published: March 2007

This article is an introduction to and systematic exposition of the key insights of cognitive psychologist Howard Gruber (Teachers College, Columbia University), whose "deeply phenomenological" case study approach, emphasizing the development of a "theory of the individual" for creative figures of great stature, has led to important discoveries about the nature-the how and not the whyof creative work. In his explorations of the world, the individual finds out what needs doing. In his attempts to do some of it, he finds out what he can do and what he cannot. He also comes to see what he need not do. From the intersection of these possibilities there emerges a new imperative, his sense of what he must do. How "it needs" and "I can" give birth to "I must" remains enigmatic. -Howard E. Gruber Darwin on Man (with P. H. Barrett) To live a creative life is one of the intentions of a creative person. -Doris B. Wallace Creative People at Work
Clinical Consequences of Posttraumatic Bone Bruise in the Knee
Authors: Boks Simone S. , Vroegindeweij Dammis , Koes Bart W. , Bernsen Roos M. D. , Myriam Hunink M.G. , Bierma-Zeinstra Sita M. A. 
Published: February 2007

Background Bone bruise is often seen in posttraumatic knees, but the clinical relevance is unclear. Hypothesis The presence of bone bruise is associated with increased pain severity in patients with sustained knee trauma. Study Design Cohort study; Level of evidence, 2. Methods We collected prospective data of 132 patients visiting their general practitioner after sustained knee trauma. Patients with bone bruise underwent a magnetic resonance imaging follow-up study that was discontinued when the bone bruise could no longer be discerned or after 1 year of follow-up. Bone bruise was assessed on magnetic resonance imaging, and pain severity was scored on a numeric rating scale (0-10) at baseline, and at 3, 6, and 12 months after trauma. The presence of bone bruise and pain severity (over time) were compared using linear regression analyses for repeated measurements. Adjustment was made for possible confounders: presence of meniscal tears, cruciate or collateral ligament ruptures, severe effusion, osteoarthritis, obesity, age, gender, work load, and sports load. Results At baseline as well as during follow-up, bone bruise was associated with a slightly higher pain score. The differences, however, were very small (adjusted difference in pain severity 0.34 or less) and not statistically significant nor clinically relevant. Conclusion There is no statistically significant relationship, nor a clinically relevant relationship, between the presence of bone bruise and pain severity in patients with sustained knee injury in general practice.
Knee and Hip Loading Patterns at Different Phases in the Menstrual Cycle
Authors: Chaudhari Ajit M. W. , Lindenfeld Thomas N. , Andriacchi Thomas P. , Hewett Timothy E. , Riccobene Jennifer , Myer Gregory D. , Noyes Frank R. 
Published: February 2007

Background Menstrual cycle phase has been correlated with risk of noncontact anterior cruciate ligament injury in women. The mechanism by which hormonal cycling may affect injury rate is unknown. Hypotheses Jumping and landing activities performed during different phases of the menstrual cycle lead to differences in foot strike knee flexion, as well as peak knee and hip loads, in women not taking an oral contraceptive but not in women taking an oral contraceptive. Women will experience greater normalized joint loads than men during these activities. Study Design Controlled laboratory study. Methods Twenty-five women (13 using oral contraceptives) and 12 men performed repeated trials of a horizontal jump, vertical jump, and drop from a 30-cm box on the left leg. Lower limb kinematics (foot strike knee flexion) and peak externally applied moments were calculated (hip adduction moment, hip internal rotation moment, knee flexion moment, knee abduction moment). Men were tested once. Women were tested twice for each phase of the menstrual cycle (follicular, luteal, ovulatory), as determined from serum analysis. An analysis of variance was used to examine differences between phases of the menstrual cycle and between groups (α = .05). Results No significant differences in moments or knee angle were observed between phases in either female group or between the 2 female groups or between either female group and the male controls. Conclusions Variations of the menstrual cycle and the use of an oral contraceptive do not affect knee or hip joint loading during jumping and landing tasks. Clinical Relevance Because knee and hip joint loading is unaffected by cyclic variations in hormone levels, the observed difference in injury rates is more likely attributable to persistent differences in strength, neuromuscular coordination, or ligament properties.
Femoral Fixation of Hamstring Grafts in Posterior Cruciate Ligament Reconstruction: Biomechanical Evaluation of Different Fixation Techniques
Authors: Niedzwietzki Patricia , Zantop Thore , Weimann Andre , Herbort Mirco , Raschke Michael J. , Petersen Wolf 
Published: February 2007

Background The literature provides little biomechanical data about femoral fixation of hamstring grafts in posterior cruciate ligament reconstruction. Hypothesis A hybrid fixation technique with use of an undersized screw has sufficient strength to provide secure fixation of posterior cruciate ligament grafts. Additional aperture fixation with a biodegradable interference screw can prevent graft damage that might be caused by an acute angle on the edge of the femoral tunnel. Study Design Controlled laboratory study. Methods In part 1, extracortical fixation of posterior cruciate ligament reconstructions with quadrupled porcine flexor digitorum grafts to simulate human hamstring grafts was compared with hybrid fixation methods using 6-, 7-, and 8-mm screws. Groups were tested in cycling loading with the load applied in line with the bone tunnel. In part 2, extracortical fixation was compared with hybrid fixation using a 1-mm undersized screw anterior and posterior to the graft. Structural properties and graft abrasion were evaluated after cyclic loading with the load applied at 90° to the tunnel. In each group, 8 porcine knees were tested. Results In part 1, stiffness, maximum load, and yield load were significantly higher for hybrid fixation than for extracortical fixation. Hybrid fixation with an 8-mm screw resulted in higher yield load than with a 7-mm screw. In part 2, graft laceration was more pronounced in specimens with extracortical fixation than with hybrid fixation. Posterior screw placement was superior to the anterior position. Conclusion For all parameters, hybrid fixation with an interference screw provided superior structural results. No relevant disadvantages of undersized screws could be found. Graft damage due to abrasion at the edge of the femoral bone tunnel was reduced by use of an interference screw. The posterior screw placement seems favorable. Clinical Relevance Hybrid fixation of hamstring grafts in posterior cruciate ligament reconstruction is superior to extracortical fixation alone with no relevant disadvantages of undersized screws. The results raise the suspicion of an acute angle effect of the femoral bone tunnel.