Mfd Dynamically Regulates Transcription via a Release and Catch-Up Mechanism

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Estimation of Membrane Potential Δψ in Reconstituted Plasma Membrane Vesicles Using a Numerical Model of Oxonol VI Distribution

A model of membrane potential-dependent distribution of oxonol VI to estimate the electrical potential difference across Schizosaccharomyces pombe plasma membrane vesicles (PMV) has been developed. was generated by the H⁺-ATPase reconstituted in the PMV. The model treatment was necessary since the usual calibration of the dye fluorescence changes by diffusion potentials (K⁺ + valinomycin) failed. The model allows for fitting of fluorescence changes at different vesicle and dye concentrations, yielding in ATP-energized PMV of 80 mV. The described model treatment to estimate may be applicable for other reconstituted membrane systems.     

The Macrocyclic Peptide Antibiotic Micrococcin P1 Is Secreted by the Food-Borne Bacterium Staphylococcus equorum WS 2733 and Inhibits Listeria monocytogenes on Soft Cheese

Staphylococcus equorum WS 2733 was found to produce a substance exhibiting a bacteriostatic effect on a variety of gram-positive bacteria. The metabolite was purified to homogeneity by ammonium sulfate precipitation and semipreparative reversed-phase high-performance liquid chromatography. Electrospray mass spectrometry confirmed the high purity of the compound and revealed a molecular mass of 1,143 Da. By two-dimensional nuclear magnetic resonance spectroscopy the substance was identified as micrococcin P₁ which is a macrocyclic peptide antibiotic that has not yet been reported for the genus Staphylococcus. A total of 95 out of 95 Listeria strains and 130 out of 135 other gram-positive bacteria were inhibited by this substance, while none of 37 gram-negative bacteria were affected. The antilisterial potential of this food-grade strain as a protective starter culture was evaluated by its in situ application in cheese-ripening experiments under laboratory conditions. A remarkable growth reduction of Listeria monocytogenes could be achieved compared to control cheese ripened with a nonbacteriocinogenic type strain of Staphylococcus equorum. In order to prove that inhibition was due to micrococcin P₁, a micrococcin-deficient mutant was constructed which did not inhibit L. monocytogenes in cheese-ripening experiments.     

Oxidation of propionate to pyruvate in Escherichia coli. Involvement of methylcitrate dehydratase and aconitase.

The pathway of the oxidation of propionate to pyruvate in Escherichia coli involves five enzymes, only two of which, methylcitrate synthase and 2-methylisocitrate lyase, have been thoroughly characterized. Here we report that the isomerization of (2S,3S)-methylcitrate to (2R,3S)-2-methylisocitrate requires a novel enzyme, methylcitrate dehydratase (PrpD), and the well-known enzyme, aconitase (AcnB), of the tricarboxylic acid cycle. AcnB was purified as 2-methylaconitate hydratase from E. coli cells grown on propionate and identified by its N-terminus. The enzyme has an apparent Km of 210 micro m for (2R,3S)-2-methylisocitrate but shows no activity with (2S,3S)-methylcitrate. On the other hand, PrpD is specific for (2S,3S)-methylcitrate (Km = 440 micro m) and catalyses in addition only the hydration of cis-aconitate at a rate that is five times lower. The product of the dehydration of enzymatically synthesized (2S,3S)-methylcitrate was designated cis-2-methylaconitate because of its ability to form a cyclic anhydride at low pH. Hence, PrpD catalyses an unusual syn elimination, whereas the addition of water to cis-2-methylaconitate occurs in the usual anti manner. The different stereochemistries of the elimination and addition of water may be the reason for the requirement for the novel methylcitrate dehydratase (PrpD), the sequence of which seems not to be related to any other enzyme of known function. Northern-blot experiments showed expression of acnB under all conditions tested, whereas the RNA of enzymes of the prp operon (PrpE, a propionyl-CoA synthetase, and PrpD) was exclusively present during growth on propionate. 2D gel electrophoresis showed the production of all proteins encoded by the prp operon during growth on propionate as sole carbon and energy source, except PrpE, which seems to be replaced by acetyl-CoA synthetase. This is in good agreement with investigations on Salmonella enterica LT2, in which disruption of the prpE gene showed no visible phenotype.     

Population recognition of infant isolation peeps in the squirrel monkey

Infants from three populations of squirel monkeys with different pelage, behaviour patterns and physiological patterns emitted two forms of isolation peeps. Offspring from Peruvian and Bolivian stock produced isolation peeps previously described as belonging to ‘Roman Arch’ monkeys, whereas the Guyanese population produced isolation peeps previously described as belonging to ‘Gothic Arch’ monkeys. Playbacks of isolation peeps from, infants of each population to groups of adult monkeys revealed a population specificity in the response to infant calls. Peruvian, and Bolivian adults responded with increased activity, decreased huddling and increased approach to the speaker only when isolation peeps of Peruvian and Bolivian infants were broadcast. Guyanese adult monkeys showed similar responses to the isolation peeps of Guyanese infants. These are the first reported data indicating that the long-recognized vocal differences in squirrel monkey populations are responded to differentially. The results also support a major taxonomic division between the Gothic Arch and Roman Arch populations with the other morphological and physiological differences within these populations reflecting secondary divisions.     

An Efficient Method of Selectable Marker Gene Excision by Xer Recombination for Gene Replacement in Bacterial Chromosomes

A simple, effective method of unlabeled, stable gene insertion into bacterial chromosomes has been developed. This utilizes an insertion cassette consisting of an antibiotic resistance gene flanked by dif sites and regions homologous to the chromosomal target locus. dif is the recognition sequence for the native Xer site-specific recombinases responsible for chromosome and plasmid dimer resolution: XerC/XerD in Escherichia coli and RipX/CodV in Bacillus subtilis. Following integration of the insertion cassette into the chromosomal target locus by homologous recombination, these recombinases act to resolve the two directly repeated dif sites to a single site, thus excising the antibiotic resistance gene. Previous approaches have required the inclusion of exogenous site-specific recombinases or transposases in trans; our strategy demonstrates that this is unnecessary, since an effective recombination system is already present in bacteria. The high recombination frequency makes the inclusion of a counter-selectable marker gene unnecessary.     

Significant dreams: Repositioning the self narrative.

In this article the authors argue that the study of the ongoing significance of significant dreams necessarily goes beyond quantitative methods for analyzing dream content to a qualitative study of how the dream experience influences the dreamer's meaning-making processes. A set of concepts from narrative psychology is introduced as being potentially valuable in this regard. A case study is presented to illustrate how the significant dream may serve as a catalyst for repositioning the dreamer's self narrative relative to a cultural master narrative. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

A high risk phenotype of hypertrophic cardiomyopathy associated with a compound genotype of two mutated β-myosin heavy chain genes

Hypertrophic cardiomyopathy (HCM) is a genetically and clinically heterogeneous myocardial disease that is in most cases familial and transmitted in a dominant fashion. The most frequently affected gene codes for the cardiac (ventricular) β-myosin heavy chain. We have investigated the genetic cause of an isolated case of HCM, which was marked by an extremely severe phenotype and a very early age of onset. HCM is normally not a disease of small children. The proband was a boy who had suffered cardiac arrest at the age of 6.5years (resuscitation by cardioconversion). Upon screening of the β-myosin heavy chain gene as a candidate, two missense mutations, one in exon19 (Arg719Trp) and a second in exon12 (Met349Thr), were identified. The Arg719Trp mutation was de novo, as it was not found in the parents. In contrast, the Met349Thr mutation was inherited through the maternal grandmother. Six family members were carriers of this mutation but only the proband was clinically affected. Segregation and molecular analysis allowed us to assign the Met349Thr mutation to the maternal and the Arg719Trp de novo mutation to the paternal β-myosin allele. Thus, the patient has no normal myosin. We interpret these findings in terms of compound heterozygosity of a dominant (Arg719Trp) and a recessive (Met349Thr) mutation. Whereas a single mutated Arg719Trp allele would be sufficient to cause HCM, the concurrent Met349Thr mutation alone does not apparently induce the disease. Nevertheless, it conceivably contributes to the particularly severe phenotype. Received: 15 September 1997 / Accepted: 26 November 1997     

The cytogenetic effect of thermal neutrons inLens esculenta (Moench)

The first information concerning the cytogenetic efficiency of thermal neutrons in lentil are presented in this paper. The range of cytologically effective dosages of thermal neutrons in lentil was determined. This determination enables us to compare the efficiency with the mutagenic effect of thermal neutrons and with their effect on the growth and development of plants of M₁ generation. These effects were already evaluated in previous communications. Thermal neutron irradiation significantly affected all the characters studied. A linear dependence of the effect on the dose of the neutron radiation was found for most of the analyzed characters. From a sample of scored cells, whose nuclei were in the anaphase or early telophase, 9.0 to 72.0% of them had chromosomal bridges and fragments after irradiation with dosages from 3.3×10¹¹ n cm^?2 to 4.5×10¹² n cm^?2. The highest number of rearrangements per one cell reached 2.16 after irradiation with 4.25×10¹² n cm^?2 while the lowest dosage used, 3.3×10¹¹ n cm^?2, induced 0.17 of chromosomal rearrangements per one cell. Irradiation with thermal neutrons is capable of inducing a large number of very complicated chromosome rearragements.