bluuebunny/crossref_metadata_2025 huggingface dataset:
EFFECTS OF EVENING ACTIVITY ON EARLY NIGHT SLEEP
Authors: Hauri Peter
Published: February 2007

This study was designed to determine the effects of presleep activity on a variety of physiological variables during 3½ hrs of subsequent sleep. Three presleep conditions were investigated for each of 15 Ss:6 hrs of strenuous physical exercise, 6 hrs of concentrated studying, and 6 hrs of relaxation, i.e. watching TV, listening to records, and reading magazines. The following variables were recorded during a 3½ hr sleep period: EEG, EOG, body movements, heart rate, respiratory rate, peripheral pulse voltime, phasic vasoconstrictions, rectal temperature, and rapid variations in skin potential.

None of the experimental presleep activities influenced the EEG cycle during the 3½ hrs of sleep. In particular, there were no significant differences in the following measurements as a result of presleep condition: amount of REMP time, time to first REMP, amount of delta sleep, time to first delta sleep, amount of stage 2 sleep, or number of sleep stage changes. These findings indicate a surprising stability of the sleep stage cycle vis a vis the markedly different evening activities.

Physiological arousal after exercise decreased rapidly until it was no longer distinguishable from the base levels following studying or relaxation. A tendency to approach these base levels was observed even in heart rate, a variable which remained elevated after exercise throughout the 3½ hrs of sleep. For none of the physiological variables was the level of physiological arousal during sleep inversely related to the level of physiological arousal during wakefulness.

Relating EEG sleep stages to the other variables of this study, it was observed that on nights when respiratory rate was high there was more delta sleep and less stage 2 sleep. Also, respiratory minima were most often found during stage 2 sleep immediately following a REMP, and respiratory maxima during NREM sleep were significantly associated with delta sleep. These results support Bülow's (1963) proposal that a close coupling exists between respiratory centers and those neural structures that regulate EEG arousal.
Cumulative Effects of Sleep Restriction on Daytime Sleepiness
Authors: Carskadon Mary A. , Dement William C.
Published: February 2007

Sleep and daytime sleepiness were evaluated in 10 young adult subjects to determine whether restricting nocturnal step by a constant amount produces cumulative impairment. Subjects were studied for 12 consecutive days, including 3 baseline days with a 10‐hr time in bed, 7 days with sleep restricted to 5 hrs, and 2 recovery days. In 5 subjects, recovery included a 10‐hr time in bed; in the remaining subject, recovery induced a 5‐hr time in bed with a 1‐hr daytime nap. Sleepiness was measured using two self‐rating scales and the multiple sleep latency test. During sleep restriction, nocturnal stage 2 and REM sleep were reduced and slow wave sleep was unaffected. Stanford Sleepiness Scales showed an immediate increase in daytime sleepiness that reached a plateau after 4 days. An analog sleepiness rating scale showed increased sleepiness after 2 restricted nights and leveled off after the fourth restricted night. The multiple sleep latency tests showed no effect of sleep restriction until the second day, followed by a progressive increase in sleepiness that persisted through the seventh sleep restriction day. During the recovery period, daytime sleepiness returned to basal values on all three measures following one full night of sleep; with a daytime nap, no further cumulative effects of sleep restriction were seen.
Hemispheric Asymmetry and Human Electrodermal Conditioning: The Dichotic Extinction Paradigm
Authors: Hugdahl Kenneth , Brobeck Claes‐Goran
Published: February 2007

It was hypothesized that classically conditioned responses to an auditory verbal CS initially presented only to the left cerebral hemisphere would be greater than when the same CS was presented to the right hemisphere. The experiment consisted of three different phases in a dichotic extinction paradigm. During the habituation phase the CS+ and CS− were presented binaurally, and separated. All subjects were treated alike. During the acquisition phase the conditioning subjects had the CS+ but not the CS− followed by the UCS. The CS+ and CS− were presented binaurally and separated. The control subjects received no UCS presentations. During the dichotic extinction phase, half of the conditioned subjects had the CS+ presented in the right ear (i.e., with initial left hemisphere input), with the CS− simultaneously presented in the left ear (i.e., with initial right hemisphere input). The other half had the earphones reversed. The control group was similar to the two conditioning groups. During the acquisition phase, significantly larger electrodermal responses were observed to the CS+ compared to the CS− in the conditioning groups, but not in the control group. During the dichotic extinction phase, significantly more resistance to extinction was observed in the CS+ Right‐Ear group compared to the CS+ Left‐Ear group, with the control group revealing virtually no responding at all. It was concluded that the present results have demonstrated effects of cerebral asymmetry on rate of extinction of the classically conditioned response.
Permissive Role of Calcium in α1‐Adrenergic Stimulation of Pineal Phosphatidylinositol Phosphodiesterase (Phospholipase C) Activity
Authors: Ho Anthony K. , Chik Constance L. , Klein David C.
Published: February 2007

Activation of α1‐adrenergic receptors increases [Ca+2]i and phosphatidylinositol phosphodiesterase (phospholipase C) activity in the pinealocyte. In this report the receptor involved in the stimulation of phospholipase C activity was further characterized, and the role of Ca2+ in this effect was investigated in some detail. Phospholipase C activity was estimated by measuring the production of [3H]inositol phosphates by [3H]inositol‐labelled dispersed pinealocytes in suspension culture. Norepinephrine stimulated [3H]inositol monophosphate production severalfold; this was blocked by α1‐adrenergic antagonists, including prazosin, WB 4101, and phenoxybenzamine, but by neither an α2‐ nor a β‐adrenergic antagonist, confirming that an α1‐adrenoceptor is involved in the regulation of phosphatidylinositol hydrolysis. Treatment with the Ca2+ chelator, EGTA, or with inorganic Ca2+ blockers, including Co2+, Mn2+, and La3+, reduced the norepinephrine‐stimulated response, suggesting that the α1‐adrenergic stimulation of phospholipase C activity is Ca2+ dependent. However, phospholipase C activity was not increased by elevating intracellular Ca2+ with either the Ca2+ ionophore A23187 or with depolarizing concentrations of K+. These results indicate that although Ca2+ is necessary for α1‐adrenergic stimulation of phospholipase C activity, an increase in [Ca2+]i alone is not sufficient to stimulate the activity of this enzyme, and that effects which A23187 and depolarizing concentrations of K+ have on pineal function probably do not involve stimulation of phospholipase C activity.
Characteristics of 2‐[125I]iodomelatonin binding sites in the pigeon spleen and modulation of binding by guanine nucleotides
Authors: Poon A.M.S. , Wang X.L. , Pang S.F.
Published: February 2007

Abstract: 2‐[125]Iodomelatonin binding sites in membrane preparations of pigeon spleen have been characterized. The binding was stable, saturable, reversible, and of high affinity. Rosenthal and Hill analyses showed that the radioligand‐receptor interaction involved a single class of binding sites. Analysis of the binding results of spleens collected during mid‐light revealed an equilibrium dissociation constant (Kd) of 36.6 ± 4.8 pmol/1 (mean ± sem, n = 10) and a maximum density (Bmax) of 2.3 ± 0.2 fmol/mg protein. There was no significant difference in the Kd (46.9 ± 5.0 pmol/1) or the Bmax values (2.4 ± 0.3 fmol/mg protein) for spleens collected during mid‐dark (n = 9), although the mid‐dark serum and pineal melatonin levels were significantly higher (P < 0.05) than the corresponding mid‐light values. Kinetic analysis showed a Kd of 8.6 ± 2.0 pmol/1 (n ± 4), in agreement with that derived from the saturation studies. Except for inhibition by 2‐iodomelatonin, melatonin, 6‐chloromelatonin, 6‐hydroxymelatonin and N‐acetylserotonin, the other indoles or neurotransmitters tested have little inhibition on the binding. In addition, guanosine 5′‐O‐(3‐thiophosphate) (GTPγS), a nonhydrolysable analog of GTP, was found to inhibit the binding in a dose‐dependent manner. Saturation studies revealed that this is due to a decrease in both the affinity and density of the binding sites. These data suggest that a single type of melatonin receptor is found in the pigeon spleen and that the site is coupled to a guinine nucleotide binding protein (G‐protein). Our findings support a direct pineal melatonin action on the immune system.
EFFECT OF HEN EGG PRODUCTION AND PROTEIN COMPOSITION ON TEXTURAL PROPERTIES OF EGG ALBUMEN GELS
Authors: HAMMERSHØJ MARIANNE , LARSEN LOTTE B. , IPSEN RICHARD H. , QVIST KARSTEN B.
Published: February 2007

The effect of hen age, strain and dietary amino acid intake on the egg albumen gel textural properties was studied in two experiments by textural profile analysis (TPA) and uniaxial compression (UC) tests. In experiment 1, eggs from 4 different hen flocks were heat processed industrially. Egg rejection due to poor albumen gelling was correlated to hen age (r = 0.502), albumen dry matter (r =−0.632), gel hardness of 1st compression (r =−0.765), and gel work of 1st compression (r =−0.740) in TPA. In experiment 2 two hen strains, representing two levels of egg production, were fed diets with supplementation of L‐lysine, methionine or both amino acids compared to a control diet. The lysine intake ranged from 818–1272 mg/hen/day and methionine intake from 377–575 mg/hen/day among hen groups, but without significant effect on the albumen gel texture parameters. The hen strains differed significantly in egg production (P<0.001), physical (P<0.001), chemical (P<0.05) and gel textural parameters of egg albumen (P<0.01). Hen age was essential, and correlated to the industrial egg rejection (r = 0.729), albumen dry matter (r =−0.902) and gel stress at fracture (r =−0.884). Albumen gels with high fracture stress values were found to contain a modified form of ovofransferrin.
A Study on Fluid Excitation Forces Acting on a Rotated Square Tube Bundle of T∕D=3.1 in Cross-Flow
Authors: Inada Fumio , Yoneda Kimitoshi , Yasuo Akira , Nishihara Takashi
Published: February 2007

The local fluid excitation force acting on a rotated square tube bundle having transverse pitch-to-diameter ratio of T∕D=3.1, in a single-phase cross-flow was measured, and the normalized power spectral density (NPSD) and correlation length in the axial direction of a tube were examined. The fluid excitation force acting on the interior tube was from three to ten times larger than that acting on the upstream tube. The fluid force was almost fully developed after the third row. NPSD of the fluid excitation force could be almost plotted on a single universal curve. Regarding the lift direction, there was a peak in NPSD at fD∕u∼0.3 caused by vortex shedding. Regarding the drag direction, there could be another peak in NPSD around twice the vortex shedding frequency. In the region of fD∕u>0.5, where the effect of the vortex shedding was assumed to be small in the lift direction, the correlation length of the lift direction was ∼1.1D. NPSD was a little larger than previous results for tube bundles of relatively small pitch to diameter ratios summarized by Axisa, Antunes, and Villard (1990, J. Fluid Struct., 4, pp. 321–341).
Identification of Prebiotic Fructooligosaccharide Metabolism in
Lactobacillus plantarum
WCFS1 through Microarrays
Authors: Saulnier Delphine M. A. , Molenaar Douwe , de Vos Willem M. , Gibson Glenn R. , Kolida Sofia
Published: January 2007

Short-chain fructooligosaccharides (scFOS) and other prebiotics are used to selectively stimulate the growth and activity of lactobacilli and bifidobacteria in the colon. However, there is little information on the mechanisms whereby prebiotics exert their specific effects upon such microorganisms. To study the genomic basis of scFOS metabolism in
Lactobacillus plantarum
WCFS1, two-color microarrays were used to screen for differentially expressed genes when grown on scFOS compared to glucose (control). A significant up-regulation (8- to 60-fold) was observed with a set of only five genes located in a single locus and predicted to encode a sucrose phosphoenolpyruvate transport system (PTS), a β-fructofuranosidase, a fructokinase, an α-glucosidase, and a sucrose operon repressor. Several other genes were slightly overexpressed, including pyruvate dehydrogenase. For the latter, no detectable activity in
L. plantarum
under various growth conditions has been previously reported. A mannose-PTS likely to encode glucose uptake was 50-fold down-regulated as well as, to a lower extent, other PTSs. Chemical analysis of the different moieties of scFOS that were depleted in the growth medium revealed that the trisaccharide 1-kestose present in scFOS was preferentially utilized, in comparison with the tetrasaccharide nystose and the pentasaccharide fructofuranosylnystose. The main end products of scFOS fermentation were lactate and acetate. This is the first example in lactobacilli of the association of a sucrose PTS and a β-fructofuranosidase that could be used for scFOS degradation.
Use of Transposon Promoter-Probe Vectors in the Metabolic Engineering of the Obligate Methanotroph
Methylomonas
sp. Strain 16a for Enhanced C
40
Carotenoid Synthesis
Authors: Sharpe Pamela L. , DiCosimo Deana , Bosak Melissa D. , Knoke Kyle , Tao Luan , Cheng Qiong , Ye Rick W.
Published: January 2007

The recent expansion of genetic and genomic tools for metabolic engineering has accelerated the development of microorganisms for the industrial production of desired compounds. We have used transposable elements to identify chromosomal locations in the obligate methanotroph
Methylomonas
sp. strain 16a that support high-level expression of genes involved in the synthesis of the C
40
carotenoids canthaxanthin and astaxanthin. with three promoterless carotenoid transposons, five chromosomal locations—the
fliCS
,
hsdM
,
ccp-3
,
cysH
, and
nirS
regions—were identified. Total carotenoid synthesis increased 10- to 20-fold when the carotenoid gene clusters were inserted at these chromosomal locations compared to when the same carotenoid gene clusters were integrated at neutral locations under the control of the promoter for the gene conferring resistance to chloramphenicol. A chromosomal integration system based on sucrose lethality was used to make targeted gene deletions or site-specific integration of the carotenoid gene cluster into the
Methylomonas
genome without leaving genetic scars in the chromosome from the antibiotic resistance genes that are present on the integration vector. The genetic approaches described in this work demonstrate how metabolic engineering of microorganisms, including the less-studied environmental isolates, can be greatly enhanced by identifying integration sites within the chromosome of the host that permit optimal expression of the target genes.
Phylogenetic Diversity of Archaea and Bacteria in the Anoxic Zone of a Meromictic Lake (Lake Pavin, France)
Authors: Lehours Anne-Catherine , Evans Paul , Bardot Corinne , Joblin Keith , Gérard Fonty
Published: January 2007

The compositions of archaeal and bacterial populations at different depths (60 m [mixolimnion-chemocline interface], 70 m [chemocline-subchemocline interface], 90 m, and 92 m [the water-sediment interface]) in the anoxic zone of the water column in Lake Pavin, a freshwater permanently stratified mountain lake in France, were determined. Phylogenetic trees were constructed from sequences to assess archaeal and bacterial diversity at the four sites.
Improved Experimental and Computational Methodology for Determining the Kinetic Equation and the Extant Kinetic Constants of Fe(II) Oxidation byAcidithiobacillus ferrooxidans
Authors: Molchanov Sharon , Gendel Yuri , Ioslvich Ilya , Lahav Ori
Published: January 2007

The variety of kinetics expressions encountered in the literature and the unreasonably broad range of values reported for the kinetics constants ofAcidithiobacillus ferrooxidansunderscore the need for a unifying experimental procedure and for the development of a reliable kinetics equation. Following an extensive and critical review of reported experimental techniques, a method based on batch pH-controlled kinetics experiments lasting less than one doubling time was developed for the determination of extant kinetics constants. The Fe(II) concentration in the experiments was measured by a method insensitive to Fe(III) interference. Kinetics parameters were determined by nonlinear fitting of the integrated form of the Monod equation to yield aKSof 31 ± 4 mg Fe2+liter−1(mean ± standard deviation), aKPof 139 ± 20 mg Fe3+liter−1, and a μmaxof 0.082 ± 0.002 h−1. The corresponding kinetics equation was as follows:\batchmode \documentclass[fleqn,10pt,legalpaper]{article} \usepackage{amssymb} \usepackage{amsfonts} \usepackage{amsmath} \pagestyle{empty} \begin{document} \[\frac{dS}{dt}{=}\left({-}\frac{0.082}{2.3{\cdot}10^{7}}\right)\frac{S{\cdot}X}{31(1{+}\frac{P_{0}{+}S_{0}{-}S}{139}){+}S}\] \end{document}whereSrepresents the Fe(II) concentration in mg liter−1,P0represents the initial Fe(III) concentration in mg liter−1,Xrepresents the suspended bacterial cell concentration in cells ml−1, andtrepresents time in hours. The measured data fit this equation exceptionally well, with anR2of >0.99. Fe(III) inhibition was found to be of a competitive nature. Contrary to previous reports, the results show that the concentration ofAcidithiobacillus ferrooxidanscells has no affect on the kinetics constants. The kinetics equation can be considered applicable only toA. ferrooxidanscells grown under environmental conditions similar to those of the inoculum tested in the study. In contrast, the experimental and computational procedure is completely general and can be applied toA. ferrooxidansirrespective of the culture history.
A Five-Strain Probiotic Combination Reduces Pathogen Shedding and Alleviates Disease Signs in Pigs Challenged with
Salmonella enterica
Serovar Typhimurium
Authors: Casey Pat G. , Gardiner Gillian E. , Casey Garrett , Bradshaw Bernard , Lawlor Peadar G. , Lynch P. Brendan , Leonard Finola C. , Stanton Catherine , Ross R. Paul , Fitzgerald Gerald F. , Hill Colin
Published: January 2007

Salmonella
spp. infection is a major cause of gastroenteritis, with many thousands of cases reported in the European Union every year. The use of probiotics offers the potential to improve this situation. Here, we investigate the effects of oral treatment of pigs with a defined lactic acid bacteria culture mixture on both clinical and microbiological signs of
Salmonella enterica
serovar Typhimurium infection. Fifteen weaned pigs blocked by sex and weight were administered control milk or a mixture of five probiotic strains as either a milk fermentate or milk suspension for a total of 30 days. The mixture consisted of two strains of
Lactobacillus murinus
and one strain each of
Lactobacillus salivarius
subsp.
salivarius
,
Lactobacillus pentosus
, and
Pediococcus pentosaceous
. Following probiotic administration for 6 days, animals were challenged orally with serovar Typhimurium; the health of the animals and the microbiological composition of their feces were monitored for 23 days postinfection. Animals treated with probiotic showed reduced incidence, severity, and duration of diarrhea. These animals also gained weight at a greater rate than control pigs administered skim milk. Mean fecal numbers of
Salmonella
were significantly reduced in probiotic-treated animals at 15 days postinfection (
P
= 0.01). The administered probiotic bacteria improved both the clinical and microbiological outcome of
Salmonella
infection. These strains offer significant benefit for use in the food industry and may have potential in human applications.
Development of Genomic Array Footprinting for Identification of Conditionally Essential Genes inStreptococcus pneumoniae
Authors: Bijlsma Jetta J. E. , Burghout Peter , Kloosterman Tomas G. , Bootsma Hester J. , de Jong Anne , Hermans Peter W. M. , Kuipers Oscar P.
Published: January 2007

Streptococcus pneumoniaeis a major cause of serious infections such as pneumonia and meningitis in both children and adults worldwide. Here, we describe the development of a high-throughput, genome-wide technique, genomic array footprinting (GAF), for the identification of genes essential for this bacterium at various stages during infection. GAF enables negative screens by means of a combination of transposon mutagenesis and microarray technology for the detection of transposon insertion sites. We tested several methods for the identification of transposon insertion sites and found that amplification of DNA adjacent to the insertion site by PCR resulted in nonreproducible results, even when combined with an adapter. However, restriction of genomic DNA followed directly by in vitro transcription circumvented these problems. Analysis of parallel reactions generated with this method on a largemarinertransposon library showed that it was highly reproducible and correctly identified essential genes. Comparison of amarinerlibrary to one generated with the in vivo transposition plasmid pGh:ISS1showed that both have an equal degree of saturation but that 9% of the genome is preferentially mutated by either one. The usefulness of GAF was demonstrated in a screen for genes essential for surviving zinc stress. This identified a gene encoding a putative cation efflux transporter, and its deletion resulted in an inability to grow under high-zinc conditions. In conclusion, we developed a fast, versatile, specific, and high-throughput method for the identification of conditionally essential genes inS. pneumoniae.
Erythromycin Resistance-Conferring Plasmid pRSB105, Isolated from a Sewage Treatment Plant, Harbors a New Macrolide Resistance Determinant, an Integron-Containing Tn
402
-Like Element, and a Large Region of Unknown Function
Authors: Schlüter A. , Szczepanowski R. , Kurz N. , Schneiker S. , Krahn I. , Pühler A.
Published: January 2007

The erythromycin resistance plasmid pRSB105 was previously isolated from an activated sludge bacterial community of a municipal wastewater treatment plant. Compilation of the complete pRSB105 nucleotide sequence revealed that the plasmid is 57,137 bp in size and has a mean G+C content of 56.66 mol%. The pRSB105 backbone is composed of two different replication and/or partitioning modules and a functional mobilization region encoding the mobilization genes
mobCDE
and
mobBA
. The first replicon (Rep1) is nearly identical to the corresponding replication module of the multiresistance plasmid pRSB101 isolated from an unknown activated sludge bacterium. Accordingly, pRSB101 and pRSB105 are sister plasmids belonging to a new plasmid family. The second replicon (Rep2) of pRSB105 was classified as a member of the IncP-6 group. While Rep1 confers replication ability only in γ-proteobacteria, Rep2 extents the host range of the plasmid since it is also functional in the β-proteobacterium
Ralstonia eutropha
. Plasmid pRSB105 harbors the macrolide resistance genes
mel
and
mph
, encoding, respectively, a predicted ABC-type efflux permease and a macrolide-2′-phosphotransferase. Erythromycin resistance is mainly attributed to
mel
, whereas
mph
contributes to erythromycin resistance to a lesser extent. The second resistance region, represented by an integron-containing Tn
402
-like element, includes a β-lactam (
oxa10
) and a trimethoprim (
dfrB2
) resistance gene cassette. In addition to antibiotic resistance modules, pRSB105 encodes a functional restriction/modification system and two nonresistance regions of unknown function. The presence of different mobile genetic elements that flank resistance and nonresistance modules on pRSB105 indicates that these elements were involved in acquisition of accessory plasmid modules. Comparative genomics of pRSB105 and related plasmids elucidated that pRSB105 evolved by integration of distinct modules from different plasmid sources, including
Pseudomonas aeruginosa
plasmids, and thus represents a mosaic plasmid.
Methane Oxidation in Termite Hindguts: Absence of Evidence and Evidence of Absence
Authors: Pester Michael , Tholen Anne , Friedrich Michael W. , Brune Andreas
Published: January 2007

A steep oxygen gradient and the presence of methane render the hindgut internal periphery of termites a potential habitat for aerobic methane-oxidizing bacteria. However, methane emissions of various termites increased, if at all, only slightly when termites were exposed to an anoxic (nitrogen) atmosphere, and
14
CH
4
added to the air headspace over live termites was not converted to
14
CO
2
. Evidence for the absence of methane oxidation in living termites was corroborated by the failure to detect
pmoA
, the marker gene for particulate methane monooxygenase, in hindgut DNA extracts of all termites investigated. This adds robustness to our concept of the degradation network in the termite hindgut and eliminates the gut itself as a potential sink of this important greenhouse gas.
Risk Factors for Contamination of Hotel Water Distribution Systems by
Legionella
Species
Authors: Mouchtouri Varvara , Velonakis Emmanuel , Tsakalof Andreas , Kapoula Christina , Goutziana Georgia , Vatopoulos Alkiviadis , Kremastinou Jenny , Hadjichristodoulou Christos
Published: January 2007

The
Legionella
colonization frequency at 385 Greek hotel hot and cold water distribution systems was 20.8%.
Legionella
contamination was associated with the presence of an oil heater (odds ratio [OR] = 2.04, 95% confidence interval [CI] = 1.12 to 3.70), with the sample temperature (OR = 0.26, 95% CI = 0.1 to 0.5), with seasonal operation (OR = 3.23, 95% CI = 1.52 to 6.87), and with the presence of an independent disinfection system (OR = 0.30, 95% CI = 0.15 to 0.62). The same water temperatures, free-chlorine levels, and pHs differently affect the survival of various
Legionella
spp.
Does the Antibacterial Activity of Silver Nanoparticles Depend on the Shape of the Nanoparticle? A Study of the Gram-Negative Bacterium
Escherichia coli
Authors: Pal Sukdeb , Tak Yu Kyung , Song Joon Myong
Published: January 2007

In this work we investigated the antibacterial properties of differently shaped silver nanoparticles against the gram-negative bacterium
Escherichia coli
, both in liquid systems and on agar plates. Energy-filtering transmission electron microscopy images revealed considerable changes in the cell membranes upon treatment, resulting in cell death. Truncated triangular silver nanoplates with a {111} lattice plane as the basal plane displayed the strongest biocidal action, compared with spherical and rod-shaped nanoparticles and with Ag
+
(in the form of AgNO
3
). It is proposed that nanoscale size and the presence of a {111} plane combine to promote this biocidal property. To our knowledge, this is the first comparative study on the bactericidal properties of silver nanoparticles of different shapes, and our results demonstrate that silver nanoparticles undergo a shape-dependent interaction with the gram-negative organism
E. coli
.
High-Level Production of the Low-Calorie Sugar Sorbitol by
Lactobacillus plantarum
through Metabolic Engineering
Authors: Ladero Victor , Ramos Ana , Wiersma Anne , Goffin Philippe , Schanck André , Kleerebezem Michiel , Hugenholtz Jeroen , Smid Eddy J. , Hols Pascal
Published: January 2007

Sorbitol is a low-calorie sugar alcohol that is largely used as an ingredient in the food industry, based on its sweetness and its high solubility. Here, we investigated the capacity of
Lactobacillus plantarum
, a lactic acid bacterium found in many fermented food products and in the gastrointestinal tract of mammals, to produce sorbitol from fructose-6-phosphate by reverting the sorbitol catabolic pathway in a mutant strain deficient for both
l
- and
d
-lactate dehydrogenase activities. The two sorbitol-6-phosphate dehydrogenase (Stl6PDH) genes (
srlD1
and
srlD2
) identified in the genome sequence were constitutively expressed at a high level in this mutant strain. Both Stl6PDH enzymes were shown to be active, and high specific activity could be detected in the overexpressing strains. Using resting cells under pH control with glucose as a substrate, both Stl6PDHs were capable of rerouting the glycolytic flux from fructose-6-phosphate toward sorbitol production with a remarkably high efficiency (61 to 65% glucose conversion), which is close to the maximal theoretical value of 67%. Mannitol production was also detected, albeit at a lower level than the control strain (9 to 13% glucose conversion), indicating competition for fructose-6-phosphate rerouting by natively expressed mannitol-
1
-phosphate dehydrogenase. By analogy, low levels of this enzyme were detected in both the wild-type and the lactate dehydrogenase-deficient strain backgrounds. After optimization, 25% of sugar conversion into sorbitol was achieved with cells grown under pH control. The role of intracellular NADH pools in the determination of the maximal sorbitol production is discussed.
Production of Dehydroamino Acid-Containing Peptides by
Lactococcus lactis
Authors: Rink Rick , Wierenga Jenny , Kuipers Anneke , Kluskens Leon D. , Driessen Arnold J. M. , Kuipers Oscar P. , Moll Gert N.
Published: January 2007

Nisin is a pentacyclic peptide antibiotic produced by some
Lactococcus lactis
strains. Nisin contains dehydroresidues and thioether rings that are posttranslationally introduced by a membrane-associated enzyme complex, composed of a serine and threonine dehydratase NisB and the cyclase NisC. In addition, the transporter NisT is necessary for export of the modified peptide. We studied the potential of
L. lactis
expressing NisB and NisT to produce peptides whose serines and threonines are dehydrated.
L. lactis
containing the
nisBT
genes and a plasmid coding for a specific leader peptide fusion construct efficiently produced peptides with a series of non-naturally occurring multiple flanking dehydrobutyrines. We demonstrated NisB-mediated dehydration of serines and threonines in a C-terminal nisin(1-14) extension of nisin, which implies that also residues more distant from the leader peptide than those occurring in prenisin or any other lantibiotic can be modified. Furthermore, the feasibility and efficiency of generating a library of peptides containing dehydroresidues were demonstrated. In view of the particular shape and reactivity of dehydroamino acids, such a library provides a novel source for screening for peptides with desired biological and physicochemical properties.
Adaptation of
Pseudomonas
sp. Strain 7-6 to Quaternary Ammonium Compounds and Their Degradation via Dual Pathways
Authors: Takenaka Shinji , Tonoki Takashi , Taira Kazuya , Murakami Shuichiro , Aoki Kenji
Published: January 2007

Pseudomonas
sp. strain 7-6, isolated from active sludge obtained from a wastewater facility, utilized a quaternary ammonium surfactant,
n
-dodecyltrimethylammonium chloride (DTAC), as its sole carbon, nitrogen, and energy source. When initially grown in the presence of 10 mM DTAC medium, the isolate was unable to degrade DTAC. The strain was cultivated in gradually increasing concentrations of the surfactant until continuous exposure led to high tolerance and biodegradation of the compound. Based on the identification of five metabolites by gas chromatography-mass spectrometry analysis, two possible pathways for DTAC metabolism were proposed. In pathway 1, DTAC is converted to lauric acid via
n
-dodecanal with the release of trimethylamine; in pathway 2, DTAC is converted to lauric acid via
n
-dodecyldimethylamine and then
n
-dodecanal with the release of dimethylamine. Among the identified metabolites, the strain precultivated on DTAC medium could utilize
n
-dodecanal and lauric acid as sole carbon sources and trimethylamine and dimethylamine as sole nitrogen sources, but it could not efficiently utilize
n
-dodecyldimethylamine. These results indicated pathway 1 is the main pathway for the degradation of DTAC.
Genetic Relatedness of
Escherichia coli
Isolates in Interstitial Water from a Lake Huron (Canada) Beach
Authors: Kon Tatiana , Weir Susan C. , Howell E. Todd , Lee Hung , Trevors Jack T.
Published: January 2007

Research was undertaken to characterize
Escherichia coli
isolates in interstitial water samples of a sandy beach on the southeastern shore of Lake Huron, Ontario, Canada. A survey of the beach area revealed the highest abundance of
E. coli
in interstitial water of the foreshore beach sand next to the swash zone. Higher concentrations of
E. coli
(up to 1.6 × 10
6
CFU/100 ml of water) were observed in the interstitial water from the sampling holes on the beach itself compared to lake water and sediment. Repetitive extragenic palindromic PCR (REP-PCR) was used to characterize the genetic diversity of
E. coli
isolates from interstitial water samples on the beach.
E. coli
isolates from the same sampling location frequently exhibited the same REP-PCR pattern or were highly similar to each other. In contrast,
E. coli
isolates from different sampling locations represented populations distinct from each other. This study has identified a unique ecological niche within the foreshore area of the beach where
E. coli
may survive and possibly multiply outside of host organisms. The results are of interest as increasing concentrations of
E. coli
in recreational waters are often considered to be an indication of recent fecal pollution.
Biofilm Formation by and Antifungal Susceptibility of
Candida
Isolates from Urine
Authors: Jain N. , Kohli R. , Cook E. , Gialanella P. , Chang T. , Fries B. C.
Published: January 2007

Biofilm formation (BF) in the setting of candiduria has not been well studied. We determined BF and MIC to antifungals in
Candida
spp. isolates grown from urine samples of patients and performed a retrospective chart review to examine the correlation with risk factors. A total of 67
Candida
spp. isolates were grown from urine samples from 55 patients. The species distribution was
C. albicans
(54%),
C. glabrata
(36%), and
C. tropicalis
(10%). BF varied greatly among individual
Candida
isolates but was stable in sequential isolates during chronic infection. BF also depended on the growth medium and especially in
C. albicans
was significantly enhanced in artificial urine (AU) compared to RPMI medium. In nine of the
C. albicans
strains BF was 4- to 10-fold higher in AU, whereas in three of the
C. albicans
strains and two of the
C. glabrata
strains higher BF was measured in RPMI medium than in AU. Determination of the MICs showed that planktonic cells of all strains were susceptible to amphotericin B (AMB) and caspofungin (CASPO) and that three of the
C. glabrata
strains and two of the
C. albicans
strains were resistant to fluconazole (FLU). In contrast, all biofilm-associated adherent cells were resistant to CASPO and FLU. The biofilms of 14 strains (28%) were sensitive to AMB (MIC
50
of <1 μg/ml). Correlation between degree of BF and MIC of AMB was not seen in RPMI grown biofilms but was present when grown in AU. A retrospective chart review demonstrated no correlation of known risk factors of candiduria with BF in AU or RPMI. We conclude that BF is a stable characteristic of
Candida
strains that varies greatly among clinical strains and is dependent on the growth medium. Resistance to AMB is associated with higher BF in AU, which may represent the more physiologic medium to test BF. Future studies should address whether in vitro BF can predict treatment failure in vivo.
Simple Method for Repurification of Endotoxins for Biological Use
Authors: Tirsoaga Alina , Novikov Alexey , Adib-Conquy Minou , Werts Catherine , Fitting Catherine , Cavaillon Jean-Marc , Caroff Martine
Published: January 2007

A method for obtaining highly purified endotoxin (lipopolysaccharide [LPS]) in a few hours by repurification of commercial or laboratory preparations was devised. It avoids the use of phenol, which is not suitable for phenol-soluble lipopolysaccharides nor for some industrial purposes. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis and matrix-assisted laser desorption ionization mass spectrometry analysis confirmed the integrity of the purified LPSs. The purified products did not activate Toll-like receptor 2 (TLR2), nuclear oligomerization domain 1 (NOD1), or NOD2 but did activate TLR4. Applied to different lipopolysaccharides, the method also improved their mass spectra, thus facilitating their structural analysis.
Biochemical Characterization of an
l
-Xylulose Reductase from
Neurospora crassa
Authors: Nair Nikhil , Zhao Huimin
Published: January 2007

An
l
-xylulose reductase identified from the genome sequence of the filamentous fungus
Neurospora crassa
was heterologously expressed in
Escherichia coli
as a His
6
tag fusion protein, purified, and characterized. The enzyme may be used in the production of xylitol from the major pentose components of hemicellulosic waste,
d
-xylose and
l
-arabinose.
Se(VI) Reduction and the Precipitation of Se(0) by the Facultative Bacterium
Enterobacter cloacae
SLD1a-1 Are Regulated by FNR
Authors: Yee N. , Ma J. , Dalia A. , Boonfueng T. , Kobayashi D. Y.
Published: January 2007

The fate of selenium in the environment is controlled, in part, by microbial selenium oxyanion reduction and Se(0) precipitation. In this study, we identified a genetic regulator that controls selenate reductase activity in the Se-reducing bacterium
Enterobacter cloacae
SLD1a-1. Heterologous expression of the global anaerobic regulatory gene
fnr
(fumarate nitrate reduction regulator) from
E. cloacae
in the non-Se-reducing strain
Escherichia coli
S17-1 activated the ability to reduce Se(VI) and precipitate insoluble Se(0) particles. Se(VI) reduction by
E. coli
S17-1 containing the
fnr
gene occurred at rates similar to those for
E. cloacae
, with first-order reaction constants of
k
= 2.07 × 10
−2
h
−1
and
k
= 3.36 × 10
−2
h
−1
, respectively, and produced elemental selenium particles with identical morphologies and short-range atomic orders. Mutation of the
fnr
gene in
E. cloacae
SLD1a-1 resulted in derivative strains that were deficient in selenate reductase activity and unable to precipitate elemental selenium. Complementation by the wild-type
fnr
sequence restored the ability of mutant strains to reduce Se(VI). Our findings suggest that Se(VI) reduction and the precipitation of Se(0) by facultative anaerobes are regulated by oxygen-sensing transcription factors and occur under suboxic conditions.
Melanin Biosynthesis in the Maize PathogenCochliobolus heterostrophusDepends on Two Mitogen-Activated Protein Kinases, Chk1 and Mps1, and the Transcription Factor Cmr1
Authors: Eliahu Noa , Igbaria Aeid , Rose Mark S. , Horwitz Benjamin A. , Lev Sophie
Published: January 2007

The maize pathogenCochliobolus heterostrophusrequires two mitogen-activated protein kinases (MAPKs), Chk1 and Mps1, to produce normal pigmentation. Young colonies ofmps1andchk1deletion mutants have a white and autolytic appearance, which was partially rescued by a hyperosmotic environment. We isolated the transcription factor Cmr1, an ortholog ofColletotrichum lagenariumCmr1 andMagnaporthe griseaPig1, which regulates melanin biosynthesis inC. heterostrophus. Deletion ofCMR1inC. heterostrophusresulted in mutants that lacked dark pigmentation and acquired an orange-pink color. Incmr1deletion strains the expression of putative scytalone dehydratase (SCD1) and hydroxynaphthalene reductase (BRN1andBRN2) genes involved in melanin biosynthesis was undetectable, whereas expression ofPKS18, encoding a polyketide synthase, was only moderately reduced. Inchk1andmps1mutants expression ofPKS18,SCD1,BRN1,BRN2, and the transcription factorCMR1itself was very low in young colonies, slightly up-regulated in aging colonies, and significantly induced in hyperosmotic conditions, compared to invariably high expression in the wild type. These findings indicate that two MAPKs, Chk1 and Mps1, affect Cmr1 at the transcriptional level and this influence is partially overridden in stress conditions including aging culture and hyperosmotic environment. Surprisingly, we found that theCMR1gene was transcribed in both sense and antisense directions, apparently producing mRNA as well as a long noncoding RNA transcript. Expression of the antisenseCMR1was also Chk1 and Mps1 dependent. Analysis of chromosomal location of the melanin biosynthesis genes inC. heterostrophusresulted in identification of a small gene cluster comprisingBRN1,CMR1, andPKS18. Since expression of all three genes depends on Chk1 and Mps1 MAPKs, we suggest their possible epigenetic regulation.
Aspergillus nidulans
Dis1/XMAP215 Protein AlpA Localizes to Spindle Pole Bodies and Microtubule Plus Ends and Contributes to Growth Directionality
Authors: Enke Cathrin , Zekert Nadine , Veith Daniel , Schaaf Carolin , Konzack Sven , Fischer Reinhard
Published: January 2007

The dynamics of cytoplasmic microtubules (MTs) is largely controlled by a protein complex at the MT plus end. In
Schizosaccharomyces pombe
and in filamentous fungi, MT plus end-associated proteins also determine growth directionality. We have characterized the Dis1/XMAP215 family protein AlpA from
Aspergillus nidulans
and show that it determines MT dynamics as well as hyphal morphology. Green fluorescent protein-tagged AlpA localized to MT-organizing centers (centrosomes) and to MT plus ends. The latter accumulation occurred independently of conventional kinesin or the Kip2-familiy kinesin KipA.
alpA
deletion strains were viable and only slightly temperature sensitive. Mitosis, nuclear migration, and nuclear positioning were not affected, but hyphae grew in curves rather than straight, which appeared to be an effect of reduced MT growth and dynamics.
Dictyostelium
Myb Transcription Factors Function at Culmination as Activators of Ancillary Stalk Differentiation
Authors: Tsujioka Masatsune , Zhukovskaya Natasha , Yamada Yoko , Fukuzawa Masashi , Ross Susan , Williams Jeffrey G.
Published: January 2007

ecmB
and
mrrA
are expressed in the cups that cradle
Dictyostelium
spore heads, and MybE is necessary for their expression in lower but not upper cup cells. A Myb site within the
mrrA
promoter is necessary for expression in both cups. Thus, multiple Myb proteins are required for ancillary stalk differentiation.
Aeromonas salmonicidaToxin AexT Has a Rho Family GTPase-Activating Protein Domain
Authors: Litvak Yael , Selinger Zvi
Published: January 2007

The N terminus of theAeromonas salmonicidaADP-ribosylating toxin AexT displays in vitro GTPase-activating protein (GAP) activity for Rac1, CDC42, and RhoA. HeLa cells transfected with the AexT N terminus exhibit rounding and actin disordering. We propose that theAeromonas salmonicidaAexT toxin is a novel member of the growing family of bacterial RhoGAPs.
A Novel Ferredoxin-Dependent Glutamate Synthase from the Hydrogen-Oxidizing Chemoautotrophic BacteriumHydrogenobacter thermophilusTK-6
Authors: Kameya Masafumi , Ikeda Takeshi , Nakamura Miyuki , Arai Hiroyuki , Ishii Masaharu , Igarashi Yasuo
Published: January 2007

Glutamate synthases are classified according to their specificities for electron donors. Ferredoxin-dependent glutamate synthases had been found only in plants and cyanobacteria, whereas many bacteria have NADPH-dependent glutamate synthases. In this study,Hydrogenobacter thermophilus, a hydrogen-oxidizing chemoautotrophic bacterium, was shown to possess a ferredoxin-dependent glutamate synthase like those of phototrophs. This is the first observation, to our knowledge, of a ferredoxin-dependent glutamate synthase in a nonphotosynthetic organism. The purified enzyme fromH. thermophiluswas shown to be a monomer of a 168-kDa polypeptide homologous to ferredoxin-dependent glutamate synthases from phototrophs. In contrast to known ferredoxin-dependent glutamate synthases, theH. thermophilusglutamate synthase exhibited glutaminase activity. Furthermore, this glutamate synthase did not react with a plant-type ferredoxin (Fd3 from this bacterium) containing a [2Fe-2S] cluster but did react with bacterial ferredoxins (Fd1 and Fd2 from this bacterium) containing [4Fe-4S] clusters. Interestingly, theH. thermophilusglutamate synthase was activated by some of the organic acids in the reductive tricarboxylic acid cycle, the central carbon metabolic pathway of this organism. This type of activation has not been reported for any other glutamate synthases, and this property may enable the control of nitrogen assimilation by carbon metabolism.
Purification and Characterization of 1-Naphthol-2-Hydroxylase from Carbaryl-Degrading
Pseudomonas
Strain C4
Authors: Swetha Vandana P. , Basu Aditya , Phale Prashant S.
Published: January 2007

Pseudomonas
sp. strain C4 metabolizes carbaryl (1-naphthyl-
N
-methylcarbamate) as the sole source of carbon and energy via 1-naphthol, 1,2-dihydroxynaphthalene, and gentisate. 1-Naphthol-2-hydroxylase (1-NH) was purified 9.1-fold to homogeneity from
Pseudomonas
sp. strain C4. Gel filtration and sodium dodecyl sulfate-polyacrylamide gel electrophoresis showed that the enzyme is a homodimer with a native molecular mass of 130 kDa and a subunit molecular mass of 66 kDa. The enzyme was yellow, with absorption maxima at 274, 375, and 445 nm, indicating a flavoprotein. High-performance liquid chromatography analysis of the flavin moiety extracted from 1-NH suggested the presence of flavin adenine dinucleotide (FAD). Based on the spectral properties and the molar extinction coefficient, it was determined that the enzyme contained 1.07 mol of FAD per mol of enzyme. Although the enzyme accepts electrons from NADH, it showed maximum activity with NADPH and had a pH optimum of 8.0. The kinetic constants

K
m

and
V
max
for 1-naphthol and NADPH were determined to be 9.6 and 34.2 μM and 9.5 and 5.1 μmol min
−1
mg
−1
, respectively. At a higher concentration of 1-naphthol, the enzyme showed less activity, indicating substrate inhibition. The

K
i

for 1-naphthol was determined to be 79.8 μM. The enzyme showed maximum activity with 1-naphthol compared to 4-chloro-1-naphthol (62%) and 5-amino-1-naphthol (54%). However, it failed to act on 2-naphthol, substituted naphthalenes, and phenol derivatives. The enzyme utilized one mole of oxygen per mole of NADPH. Thin-layer chromatographic analysis showed the conversion of 1-naphthol to 1,2-dihydroxynaphthalene under aerobic conditions, but under anaerobic conditions, the enzyme failed to hydroxylate 1-naphthol. These results suggest that 1-NH belongs to the FAD-containing external flavin mono-oxygenase group of the oxidoreductase class of proteins.
Precise Excision and Self-Integration of a Composite Transposon as a Model for Spontaneous Large-Scale Chromosome Inversion/Deletion of the
Staphylococcus haemolyticus
Clinical Strain JCSC1435
Authors: Watanabe Shinya , Ito Teruyo , Morimoto Yuh , Takeuchi Fumihiko , Hiramatsu Keiichi
Published: January 2007

Large-scale chromosomal inversions (455 to 535 kbp) or deletions (266 to 320 kbp) were found to accompany spontaneous loss of beta-lactam resistance during drug-free passage of the multiresistant
Staphylococcus haemolyticus
clinical strain JCSC1435. Identification and sequencing of the rearranged chromosomal loci revealed that ISSha
1
of
S. haemolyticus
is responsible for the chromosome rearrangements.