bluuebunny/crossref_metadata_2025_split huggingface dataset:
Identification of Siderophore Biosynthesis Genes Essential for Growth of
Aeromonas salmonicida
under Iron Limitation Conditions
Authors: Najimi Mohsen , Lemos Manuel L. , Osorio Carlos R. 
Published: February 2008

ABSTRACT

Aeromonas salmonicida
subsp.
salmonicida
, the etiological agent of furunculosis in fish, produces a catechol-type siderophore under iron-limiting conditions. In this study, the Fur titration assay (FURTA) was used to identify a cluster of six genes,
asbG, asbF, asbD, asbC, asbB
, and
asbI
, encoding proteins similar to components of the siderophore biosynthetic machinery in other bacteria. Reverse transcriptase PCR analyses showed that this cluster consists of four iron-regulated transcriptional units. Mutants with deletions in either
asbD
(encoding a multidomain nonribosomal peptide synthetase),
asbG
(encoding a histidine decarboxylase), or
asbC
(encoding a predicted histamine monooxygenase) did not grow under iron-limiting conditions and did not produce siderophores. Growth of the Δ
asbG
strain under iron starvation conditions was restored by addition of histamine, suggesting that the siderophore in this species could contain a histamine-derived moiety. None of the mutants could grow in the presence of transferrin, indicating that
A. salmonicida
uses the catechol-type siderophore for removal of iron from transferrin rather than relying on a receptor for this iron-binding protein. All 18
A. salmonicida
strains analyzed by DNA probe hybridization were positive in tests for the presence of the
asbD
gene, and all of them promoted the growth of
asbD, asbG
, and
asbC
mutants, suggesting that this siderophore-mediated iron uptake system is conserved among
A. salmonicida
isolates. This study provides the first description of siderophore biosynthesis genes in this fish pathogen, and the results demonstrate that the
asbD, asbG
, and
asbC
genes are necessary for the production of a catecholate siderophore that is essential for the growth of
A. salmonicida
under iron limitation conditions.
Phenotype of a Mechanosensitive Channel Mutant,
mid
-
1
, in a Filamentous Fungus,
Neurospora crassa
Authors: Lew Roger R. , Abbas Zohaib , Anderca Marinela I. , Free Stephen J. 
Published: February 2008

ABSTRACT

In the yeast
Saccharomyces cerevisiae
, the
MID1
(
m
ating-
i
nduced
d
eath) gene encodes a stretch-activated channel which is required for successful mating; the mutant phenotype is rescued by elevated extracellular calcium. Homologs of the
MID1
gene are found in fungi that are morphologically complex compared to yeast, both
Basidiomycetes
and
Ascomycetes
. We explored the phenotype of a
mid
-
1
knockout mutant in the filamentous ascomycete
Neurospora crassa
. The mutant exhibits lower growth vigor than the wild type (which is not rescued by replete calcium) and mates successfully. Thus, the role of the MID-1 protein differs from that of the homologous gene product in yeast. Hyphal cytology, growth on diverse carbon sources, turgor regulation, and circadian rhythms of the
mid-1
mutant are all similar to those of the wild type. However, basal turgor is lower than wild type, as is the activity of the plasma membrane H
+
-ATPase (measured by cyanide [CN
−
]-induced depolarization of the energy-dependent component of the membrane potential). In addition, the mutant is unable to grow at low extracellular Ca
2+
levels or when cytoplasmic Ca
2+
is elevated with the Ca
2+
ionophore A23187. We conclude that the MID-1 protein plays a role in regulation of ion transport via Ca
2+
homeostasis and signaling. In the absence of normal ion transport activity, the mutant exhibits poorer growth.
Cell Cycle Synchrony in
Giardia intestinalis
Cultures Achieved by Using Nocodazole and Aphidicolin
Authors: Poxleitner Marianne K. , Dawson Scott C. , Cande W. Zacheus 
Published: February 2008

ABSTRACT

Giardia intestinalis
is a ubiquitous intestinal protozoan parasite and has been proposed to represent the earliest diverging lineage of extant eukaryotes. Despite the importance of
Giardia
as a model organism, research on
Giardia
has been hampered by an inability to achieve cell cycle synchrony for in vitro cultures. This report details successful methods for attaining cell cycle synchrony in
Giardia
cultures. The research presented here demonstrates reversible cell cycle arrest in G
1
/S and G
2
/M with aphidicolin and nocodazole, respectively. Following synchronization, cells were able to recover completely from drug treatment and remained viable and maintained synchronous growth for 6 h. These techniques were used to synchronize
Giardia
cultures to increase the percentages of mitotic spindles in the cultures. This method of synchronization will enhance our ability to study cell cycle-dependent processes in
G. intestinalis
.
Complete Genome Sequence of the Mosquitocidal Bacterium
Bacillus sphaericus
C3-41 and Comparison with Those of Closely Related Bacillus Species
Authors: Hu Xiaomin , Fan Wei , Han Bei , Liu Haizhou , Zheng Dasheng , Li Qibin , Dong Wei , Yan Jianping , Gao Meiying , Berry Colin , Yuan Zhiming 
Published: February 2008

ABSTRACT

Bacillus sphaericus
strain C3-41 is an aerobic, mesophilic, spore-forming bacterium that has been used with great success in mosquito control programs worldwide. Genome sequencing revealed that the complete genome of this entomopathogenic bacterium is composed of a chromosomal replicon of 4,639,821 bp and a plasmid replicon of 177,642 bp, containing 4,786 and 186 potential protein-coding sequences, respectively. Comparison of the genome with other published sequences indicated that the
B. sphaericus
C3-41 chromosome is most similar to that of
Bacillus
sp. strain NRRL B-14905, a marine species that, like
B. sphaericus
, is unable to metabolize polysaccharides. The lack of key enzymes and sugar transport systems in the two bacteria appears to be the main reason for this inability, and the abundance of proteolytic enzymes and transport systems may endow these bacteria with exclusive metabolic pathways for a wide variety of organic compounds and amino acids. The genes shared between
B. sphaericus
C3-41 and
Bacillus
sp. strain NRRL B-14905, including mobile genetic elements, membrane-associated proteins, and transport systems, demonstrated that these two species are a biologically and phylogenetically divergent group. Knowledge of the genome sequence of
B. sphaericus
C3-41 thus increases our understanding of the bacilli and may also offer prospects for future genetic improvement of this important biological control agent.
Hjm/Hel308A DNA Helicase fromSulfolobus tokodaiiPromotes Replication Fork Regression and Interacts with Hjc Endonuclease In Vitro
Authors: Li Zhuo , Lu Shuhong , Hou Guihua , Ma Xiaoqing , Sheng Duohong , Ni Jinfeng , Shen Yulong 
Published: February 2008

ABSTRACTHjm and Hel308a are novel, RecQ-like DNA helicases recently identified in the euryarchaeotesPyrococcus furiosusandMethanothermobacter thermautotrophicus, respectively. In this study, an Hjm/Hel308 homologue (designated StoHjm) fromSulfolobus tokodaii, a hyperthermophilic archaeon belonging to theCrenarchaeotasubdomain of archaea, was cloned, purified, and characterized. Unlike Hjm and Hel308a, which unwind DNA in a 3′-to-5′ direction, StoHjm unwound DNA in both 3′-to-5′ and 5′-to-3′ directions. Remarkably, StoHjm exhibited structure-specific single-stranded-DNA-annealing and fork regression activities in vitro. In addition, gel filtration, affinity pulldown, and yeast two-hybrid analyses revealed that StoHjm physically interacted with StoHjc, the Holliday junction-specific endonuclease fromS. tokodaii. This interaction may have functional significance, because the unwinding activity of StoHjm was inhibited by StoHjc in vitro. These results may suggest that the Hjm/Hel308 family helicases, in association with Hjc endonucleases, are involved in processing of stalled replication forks.
YjgF Is Required for Isoleucine Biosynthesis whenSalmonella entericaIs Grown on Pyruvate Medium
Authors: Christopherson Melissa R. , Schmitz G. E. , Downs Diana M. 
Published: February 2008

ABSTRACTThe YjgF/YER057c/UK114 family of proteins is conserved across the three domains of life, yet no biochemical function has been clearly defined for any member of this family. InSalmonella enterica, a deletion ofyjgFresults in a requirement for isoleucine when the mutant strain is grown in glucose-serine or pyruvate medium. Feedback inhibition of IlvA is required for the curative effect of isoleucine on glucose-serine medium. On pyruvate medium,yjgFmutants are unable to synthesize enough isoleucine for growth. From this study, we conclude that the isoleucine requirement of ayjgFmutant on pyruvate is a consequence of the decreased transaminase B (IlvE) activity that has previously been characterized in these mutants.
Nitrate Enhances the Survival of
Mycobacterium tuberculosis
during Inhibition of Respiration
Authors: Sohaskey Charles D. 
Published: February 2008

ABSTRACT

When oxygen is slowly depleted from growing cultures of
Mycobacterium tuberculosis
, they enter a state of nonreplicating persistence that resembles the dormant state seen with latent tuberculosis. In this hypoxic state, nitrate reductase activity is strongly induced. Nitrate in the medium had no effect on long-term persistence during gradual oxygen depletion (Wayne model) for up to 46 days, but significantly enhanced survival during sudden anaerobiosis. This enhancement required a functional nitrate reductase. Thioridazine is a member of the class of phenothiazines that act, in part, by inhibiting respiration. Thioridazine was toxic to both actively growing and nonreplicating cultures of
M. tuberculosis
. At a sublethal concentration of thioridazine, nitrate in the medium improved the growth. At lethal concentrations of thioridazine, nitrate increased survival during aerobic incubation as well as in microaerobic cultures that had just entered nonreplicating persistence (NRP-1). In contrast, the survival of anaerobic persistent (NRP-2) cultures exposed to thioridazine was not increased by the addition of nitrate. Nitrate reduction is proposed to play a role during the sudden interruption of aerobic respiration due to causes such as hypoxia, thioridazine, or nitric oxide.
Transposable Modules Generated by a Single Copy of Insertion Sequence IS
Pme1
and Their Influence on Structure and Evolution of Natural Plasmids of
Paracoccus methylutens
DM12
Authors: Bartosik Dariusz , Putyrski Mateusz , Dziewit Lukasz , Malewska Edyta , Szymanik Michal , Jagiello Ewa , Lukasik Jacek , Baj Jadwiga 
Published: February 2008

ABSTRACT

We demonstrated that a single copy of insertion sequence IS
Pme1
can mobilize adjacent segments of genomic DNA of
Paracoccus methylutens
DM12, which leads to the generation of diverse transposable elements of various size and DNA contents. All elements (named transposable modules [TMos]) contain IS
Pme1
(placed at the 5′ ends of the elements) and have variable 3′-end regions of between 0.5 and 5 kb. IS
Pme1
was shown to encode an outwardly oriented promoter, which may activate the transcription of genes transposed within TMos in evolutionarily distinct hosts. TMos may therefore be considered to be natural systems enabling gene capture, expression, and spread. However, unless these elements have been inserted into a highly conserved genetic context to enable a precise definition of their termini, it is extremely difficult or even impossible to identify them in bacterial genomes by in silico sequence analysis. We showed that TMos are present in the chromosome and plasmids of strain DM12. Sequence analysis of plasmid pMTH1 (32 kb) revealed that four TMos, previously identified with a trap vector, pMEC1, comprise 87% of its genome. Repeated TMos within pMTH1 may stimulate other structural rearrangements resulting from homologous recombination between long repeat sequences. This illustrates that TMos may play a significant role in shaping the structure of natural plasmids, which consequently may have a great impact on the evolution of plasmid genomes.
Regulation of the Synthesis of the Angucyclinone Antibiotic Alpomycin inStreptomyces ambofaciensby the Autoregulator Receptor AlpZ and Its Specific Ligand
Authors: Bunet Robert , Mendes Marta V. , Rouhier Nicolas , Pang Xiuhua , Hotel Laurence , Leblond Pierre , Aigle Bertrand 
Published: February 2008

ABSTRACTStreptomyces ambofaciensproduces an orange pigment and the antibiotic alpomycin, both of which are products of a type II polyketide synthase gene cluster identified in each of the terminal inverted repeats of the linear chromosome. Five regulatory genes encodingStreptomycesantibiotic regulatory proteins (alpV, previously shown to be an essential activator gene;alpT; andalpU) and TetR family receptors (alpZandalpW) were detected in this cluster. Here, we demonstrate that AlpZ, which shows high similarity to γ-butyrolactone receptors, is at the top of a pathway-specific regulatory hierarchy that prevents synthesis of thealppolyketide products. Deletion of the two copies ofalpZresulted in the precocious production of both alpomycin and the orange pigment, suggesting a repressor role for AlpZ. Consistent with this, expression of the fivealp-located regulatory genes and of two representative biosynthetic structural genes (alpAandalpR) was induced earlier in thealpZdeletion strain. Furthermore, recombinant AlpZ was shown to bind to specific DNA sequences within the promoter regions ofalpZ,alpV, andalpXW, suggesting direct transcriptional control of these genes by AlpZ. Analysis of solvent extracts ofS. ambofacienscultures identified the existence of a factor which induces precocious production of alpomycin and pigment in the wild-type strain and which can disrupt the binding of AlpZ to its DNA targets. This activity is reminiscent of γ-butyrolactone-type molecules. However, the AlpZ-interacting molecule(s) was shown to be resistant to an alkali treatment capable of inactivating γ-butyrolactones, suggesting that the AlpZ ligand(s) does not possess a lactone functional group.
Translation Inhibitor Pdcd4 Is Targeted for Degradation during Tumor Promotion
Authors: Schmid Tobias , Jansen Aaron P. , Baker Alyson R. , Hegamyer Glenn , Hagan John P. , Colburn Nancy H. 
Published: February 2008

Abstract
Inactivation of tumor suppressors is among the rate-limiting steps in carcinogenesis that occur during the tumor promotion stage. The translation inhibitor programmed cell death 4 (Pdcd4) suppresses tumorigenesis and invasion. Although Pdcd4 is not mutationally inactivated in human cancer, the mechanisms controlling Pdcd4 inactivation during tumorigenesis remain elusive. We report that tumor promoter 12-O-tetradecanoylphorbol-13-acetate exposure decreases protein levels of Pdcd4 in mouse skin papillomas and keratinocytes as well as in human HEK293 cells. This decrease is attributable to increased proteasomal degradation of Pdcd4 and is mediated by protein kinase C–dependent activation of phosphatidylinositol 3-kinase–Akt–mammalian target of rapamycin–p70S6K and mitogen-activated protein/extracellular signal-regulated kinase (ERK) kinase (MEK)–ERK signaling. Both Akt and p70S6K phosphorylate Pdcd4, allowing for binding of the E3-ubiquitin ligase β-TrCP and consequently ubiquitylation. MEK-ERK signaling on the other hand facilitates the subsequent proteasomal degradation. We further show that Pdcd4 protein levels in vivo are limiting for tumor formation, establishing Pdcd4 as a haploinsufficient tumor suppressor in Pdcd4-deficient mice. Thus, because endogenous Pdcd4 levels are limiting for tumorigenesis, inhibiting signaling to Pdcd4 degradation may prove a valid strategy for cancer prevention and intervention. [Cancer Res 2008;68(5):1254–60]
Medical Liability and Liability of Health Institutions in Turkish Law
Authors: Özsunay Ergun 
Published: February 2008

AbstractThis article deals with medical liability of doctors and health institutions under Turkish law. Medical liability is based usually on a medical treatment agreement. This agreement is qualified as "mandate" (Auftrag). Under this agreement doctors are obliged to carry out medical intervention and treatment in accordance with professional standards. Informed consent is a prerequisite for all medical interventions. Treatment without patient's informed consent is a ground of liability. As regards treatment in hospitals medical treatment agreement is concluded between patient and hospital management. Doctors and other health care personnel employed by private hospitals are auxiliaries in medical treatment. Liability for treatment in State or municipality hospitals is based on administrative law. In case of malpractice, liability of physicians and health institutions covers all bodily injuries and material damages as well as immaterial damages. A draft law on liability for malpractice in medical services is being discussed by relevant circles in Turkey.
Constitutional Review of the Slovenian Health Law
Authors: Ivanc Blaž 
Published: February 2008

AbstractThe development of the modern Slovenian Health Law was first urged by the adoption of a new Constitution in the year 1991. Since then the Jurisprudence of the Constitutional Court has played a noticeable role by assuring the effective protection of Human Rights in the field of Health Law Legislation, which includes about thirty statutes. In several cases the Constitutional Court had to annul some parts of Health Legislation because they were not in accordance with the Constitution. The constitutional review of the Constitutional Court has been a very important factor in building and improving the Slovenian Health Law. Its jurisprudence can be regarded as one of the main causes for a comprehensive Health Law Reform which started in the year 2006.
Patellofemoral Contact Area and Pressure after Medial Patellofemoral Ligament Reconstruction
Authors: Melegari Todd M. , Parks Brent G. , Matthews Leslie S. 
Published: February 2008

Background It is not known whether nonisometric femoral graft attachment diminishes the effectiveness of medial patellofemoral ligament reconstruction. Purpose To determine whether a nonisometric femoral attachment point is associated with differences in contact area and pressure in the patellofemoral joint as compared with an isometric attachment point. Study Design Controlled laboratory study. Methods Eleven cadaveric knees were amputated and secured in a loading fixture. The quadriceps tendon was clamped 5 cm above the proximal pole of the patella and fixed to a plate. Colinear compressive forces were applied. Forces were set to achieve isometric quadriceps moments at 30°, 45°, 60°, and 90° of knee flexion. Contact areas and pressures were measured using a sensor system. Initially, isometric reconstruction was done using the known isometric femoral attachment point of the posterior medial epicondyle. The attachment was then revised in each specimen to the known nonisometric femoral attachment of the adductor tubercle. Results Before medial patellofemoral ligament reconstruction, average facet patellofemoral contact area and pressure generally increased with angle of knee flexion. With few exceptions, initial versus postprocedure data and isometric versus nonisometric contact area and pressure data did not differ significantly at any angle tested. Percentage contact area and contact pressure in the medial facet did not differ significantly from the initial percentage for either attachment, and no difference was found in the percentage medial contact area or pressure for isometric versus nonisometric attachment at the angles tested. Conclusion Use of the nonisometric attachment point of the adductor tubercle in medial patellofemoral ligament reconstruction did not appear to alter knee contact area or contact pressures as compared with isometric femoral attachment at the posterior medial epicondyle. Clinical Relevance In medial patellofemoral ligament reconstruction, patellofemoral contact area and pressure may not be adversely affected by use of the nonisometric femoral attachment point used in this study.
Anatomical and Nonanatomical Double-Bundle Anterior Cruciate Ligament Reconstruction
Authors: Zantop Thore , Diermann Nadine , Schumacher Tobias , Schanz Steffen , Fu Freddie H. , Petersen Wolf 
Published: February 2008

Background Studies have suggested that double-bundle anterior cruciate ligament reconstruction may restore intact knee kinematics better than single-bundle anterior cruciate ligament reconstruction. Although the tunnel position of the femoral anteromedial bundle is well established, the effects of different posterolateral bundle positions on knee kinematics are unknown. Hypothesis Double-bundle anterior cruciate ligament reconstruction with an anatomical (shallow) femoral posterolateral bundle tunnel placement will restore knee kinematics more closely than will a nonanatomical (deep) femoral posterolateral bundle tunnel position. Study Design Controlled laboratory study. Methods In 12 human cadaveric knees, the kinematics of the intact knee, anterior cruciate ligament-deficient knee, and double-bundle anterior cruciate ligament-reconstructed knees with nonanatomical femoral posterolateral tunnel placement and anatomical posterolateral bundle placement were determined in response to a 134-N anterior tibial load and a combined rotatory load of 10 Nm valgus and 4 Nm internal tibial rotation using a robotic/universal force moment sensor testing system. Statistical analyses were performed using a 2-way analysis of variance test. Results Double-bundle anterior cruciate ligament reconstruction with nonanatomical posterolateral bundle placement showed significantly higher anterior tibial translation under anterior tibial and combined rotatory load than did the intact knee at 0° and 30° of knee flexion ( P < .05). Reconstruction with an anatomical posterolateral tunnel placement restored the intact knee kinematics and showed significantly lower anterior tibial translation under anterior tibial and combined rotatory load when compared with reconstruction with nonanatomical posterolateral placement ( P < .05). Conclusion Double-bundle anterior cruciate ligament reconstruction using the anatomical posterolateral bundle tunnel position restores the intact knee kinematics. A nonanatomical posterolateral bundle position results in rotatory instability. Clinical Relevance Double-bundle anterior cruciate ligament reconstruction should be performed using anatomical tunnel placement of the anteromedial and posterolateral bundles. Nonanatomical double-bundle reconstruction may fail to show any clinical superiority to single-bundle reconstruction and should be avoided.