bluuebunny/crossref_metadata_2025 huggingface dataset:
Qualitative and quantitative changes of melatonin levels in physiological and pathological aging and in centenarians
Authors: Magri Flavia , Sarra Serena , Cinchetti Wilma , Guazzoni Valeria , Fioravanti Marisa , Cravello Luca , Ferrari Ettore
Published: April 2004

Abstract:  Melatonin secretion is an endogenous synchronizer, and it may possess some anti‐aging properties. Thus we examined melatonin levels in physiological aging, in extreme senescence and in senile dementia. In healthy old (age 66–94 yr) and young subjects (age 23–39 yr) and in demented patients (age 68–91 yr) plasma melatonin was measured by radioimmunoassay in eight serial blood samples. In centenarians (age 100–107 yr) melatonin levels were estimated by assaying urinary 6‐hydroxymelatonin sulfate (aMT6s) in two different urine samples collected from 08:00 to 20:00 hours and from 20:00 to 08:00 hours. These data were compared with the aMT6s excretion of old and young controls. Elderly subjects, demented or not, exhibited a flattened circadian profile of plasma melatonin, because of the suppression of the nocturnal peak. An age‐related decline of the circadian amplitude of the melatonin rhythm occurred in old subjects, especially in demented individuals. Furthermore, the melatonin nocturnal peak was significantly correlated with the severity of the cognitive impairment. aMT6s urinary excretion also declined with age. However, as in young controls, in centenarians the aMT6s excretion was significantly higher at night than during the day. In conclusion, pineal melatonin secretion is affected by age and by the degree of cognitive impairment. In centenarians the maintenance of the circadian organization of melatonin secretion may suggest that the amplitude of the nocturnal peak and/or the persistence of a prevalent nocturnal secretion may be an important marker of biological age and of health status.
Blood pressure‐lowering effect of melatonin in type 1 diabetes
Authors: Cavallo Anita , Daniels Stephen R. , Dolan Lawrence M. , Bean Judy A. , Khoury Jane C.
Published: April 2004

Abstract:  Our long‐term goal is to determine the utility of melatonin in prevention of hypertension in type 1 diabetes. We recently reported that 5 mg melatonin taken at bedtime increases the nocturnal drop of diastolic blood pressure (BP) in adolescents with type 1 diabetes. The present study tested the hypothesis that a higher dose of melatonin, 10 mg, lowers both systolic and diastolic BP in these patients. The design was an open‐label trial of 10 mg melatonin taken at bedtime daily for 7 days. Nine normotensive adolescents with type 1 diabetes, 16.2 ± 0.3 yr old, and eight healthy controls, 16.6 ± 0.6 yr old participated. BP was measured every 20 min by ambulatory monitoring device for 24 hr before treatment onset and on the last treatment day; sleep was monitored by diary and wrist actigraphy. Outcome measures were BP during wake, sleep and over a 24‐hr period. Sleep duration and number of awakenings were used as covariates. Significance for this pilot study was set at P < 0.10. In patients with diabetes the mean BP during sleep was lower on melatonin than before treatment: systolic 104.0 ± 2.4 and 108.4 ± 2.4 mmHg (P = 0.085) and diastolic, 57.1 ± 1.9 and 59.3 ± 1.9 mmHg (P = 0.079), respectively. In controls there was no significant effect of melatonin on BP. There was no significant effect of sleep duration or number of awakenings on the BP responses. We conclude that the present results justify phase III therapeutic trials to determine the utility of melatonin in prevention of hypertension and cardiovascular complications in type 1 diabetes.
Effects of some synthetic kynurenines on brain amino acids and nitric oxide after pentylenetetrazole administration to rats
Authors: Bikjdaouene Leila , Escames Germaine , Camacho Encarnación , León Josefa , Ferrer José M. R. , Espinosa Antonio , Gallo Miguel A. , De Dios Luna Juan , Acuña‐Castroviejo Darío
Published: April 2004

Abstract:  We have previously proven that some synthetic kynurenines behave as antagonists of the N‐methyl‐d‐aspartate receptor inhibiting neuronal subtype of nitric oxide synthase activity. We now investigate the anticonvulsant activity of four of these kynurenines in pentylenetetrazole (PTZ)‐treated rats. The rats were treated with each kynurenine (10–160 mg/kg, s.c.) 30 min before PTZ administration (100 mg/kg, s.c.). Then, latency, duration and intensity of the first seizure and the percent animal survival were noted. PTZ‐induced death was counteracted by high doses of kynurenines. Latency of the first seizure was significantly increased and its intensity reduced at the same doses, whereas the duration of the first seizure significantly decreased with doses of 20 mg/kg in most of the kynurenines tested. Three hours after PTZ administration, the surviving animals were sacrificed and the levels of brain amino acids and nitrite were measured. PTZ administration increased glutamate, glutamine, serine and taurine levels in different brain areas. High doses of kynurenines generally counteracted the effects of PTZ on excitatory amino acids, but they also reduced inhibitory aminoacids. However, the most consistent effect of kynurenines was the dose‐dependent reduction of brain nitrite levels induced by PTZ. These results reveal a new family of anticonvulsant drugs that affect mainly to nitric oxide production in the brain.
A pilot trial of BIS monitoring for procedural sedation in the emergency department
Authors: Fatovich Daniel M , Gope Monica , Paech Michael J
Published: April 2004

Objective:  Procedural sedation is common in the ED. However, there is no objective physiologic parameter available to monitor a patient's conscious state. The Bispectral Index (BIS) monitor has been validated as an objective measure of depth of anaesthesia. We studied the BIS monitor for this role in procedural sedation.

Methods:  A prospective, observational study with convenience sampling of adult patients in ED who underwent procedural sedation. Patients were treated according to standard practice and sedated as determined by the treating physician. Treating physicians were blinded to the BIS value. BIS values were recorded and compared to the Observer's Assessment of Alertness/Sedation Scale (OAAS). Upon recovery, patients were asked about recall of events while they were sedated.

Results:  Twelve patients were enrolled and 110 paired readings from 11 patients (7 male) were obtained. It was not possible to obtain readings from one patient. The mean age was 58 years (range 20–94). The Spearman correlation between BIS and OAAS was 0.027 (95% CI −0.582−0.617). For the three patients who received propofol, the correlation was 1.0. There were no episodes of explicit recall of events during the period of sedation.

Conclusions:  BIS monitoring is feasible in the ED. Our small study suggests that there is a poor correlation between BIS values and the OAAS scale. Larger studies are required to further explore this relationship. Further developments in brain monitoring technology are also needed before this form of monitoring becomes clinically useful for procedural sedation.
Practicality of performing medical procedures in chemical protective ensembles
Authors: Garner Alan , Laurence Helen , Lee Anna
Published: April 2004

Objective:  To determine whether certain life saving medical procedures can be successfully performed while wearing different levels of personal protective equipment (PPE), and whether these procedures can be performed in a clinically useful time frame.

Methods:  We assessed the capability of eight medical personnel to perform airway maintenance and antidote administration procedures on manikins, in all four described levels of PPE. The levels are: Level A — a fully encapsulated chemically resistant suit; Level B — a chemically resistant suit, gloves and boots with a full‐faced positive pressure supplied air respirator; Level C — a chemically resistant splash suit, boots and gloves with an air‐purifying positive or negative pressure respirator; Level D — a work uniform. Time in seconds to inflate the lungs of the manikin with bag‐valve‐mask, laryngeal mask airway (LMA) and endotracheal tube (ETT) were determined, as was the time to secure LMAs and ETTs with either tape or linen ties. Time to insert a cannula in a manikin was also determined.

Results:  There was a significant difference in time taken to perform procedures in differing levels of personal protective equipment (F21,72 = 1.75, P = 0.04). Significant differences were found in: time to lung inflation using an endotracheal tube (A vs. C mean difference and standard error 75.6 ± 23.9 s, P = 0.03; A vs. D mean difference and standard error 78.6 ± 23.9 s, P = 0.03); time to insert a cannula (A vs. D mean difference and standard error 63.6 ± 11.1 s, P < 0.001; C vs. D mean difference and standard error 40.0 ± 11.1 s, P = 0.01).

Conclusions:  A significantly greater time to complete procedures was documented in Level A PPE (fully encapsulated suits) compared with Levels C and D. There was however, no significant difference in times between Level B and Level C. The common practice of equipping hospital and medical staff with only Level C protection should be re‐evaluated.
Can serum mast cell tryptase help diagnose anaphylaxis?
Authors: Brown Simon GA , Blackman Konrad E , Heddle Robert J
Published: April 2004

Objective:  We aimed to determine the utility of serum mast cell tryptase to diagnose anaphylaxis.

Methods:  As part of a venom immunotherapy trial, we performed 64 sting challenges. Blood samples were taken before the sting (baseline), and 15 min and 60 min after the sting. Tryptase was measured in baseline, 15 minute and 60 minute serum samples. Histamine was measured in baseline and 15 minute plasma samples. Eleven people had undisputed severe anaphylactic reactions; tryptase and histamine levels were assessed against this clinical gold standard diagnosis.

Results:  Excluding mild reactions from the analysis, peak tryptase readings had sensitivity of 0.36 and specificity of 0.93 using the recommended cut‐off range (< 12.0 µg/L). Receiver‐operator curve analysis found a cut‐off of 9.0 µg/L would improve diagnostic performance (sensitivity 0.55, specificity 0.93). Serial tryptase measurement was significantly more discriminatory; an increase in tryptase of 2.0 µg/L or greater had a sensitivity of 0.73 and specificity of 0.98. The addition of histamine measurements, defining a positive result by either a rise in tryptase or a rise in histamine, appeared to further increase sensitivity (0.90).

Conclusions:  Clinicians should use caution when using serum tryptase to refute or support a diagnosis of anaphylaxis. Serial tryptase measurement increases sensitivity and specificity. Further studies using serial tryptase determinations in general emergency department practice, perhaps supplemented by histamine determinations, are warranted.
Management of septic shock in childhood
Authors: Sparrow Annie , Willis Frank
Published: April 2004

Objective: The object of this review is to discuss the recognition and treatment of septic shock in children based on principles of resuscitation, antibiotic use and recent therapeutic advances.

Methods: A comprehensive literature search combining these methods: on‐line searches of Ovid, PubMed, and Medline; hand searches of 25 international journals; a trawl of 26 textbooks; searches of reference lists of pertinent articles; and scans of abstracts of recent international meetings. Various national and international units were contacted with regard to current research therapeutic strategies, both published and unpublished.

Conclusions: Septic shock remains a leading cause of morbidity and mortality in children. Early administration of empirical antibiotic therapy reduces mortality. The keystone of resuscitation is aggressive volume replacement. Adjunctive therapies to modulate the inflammatory response may further enhance outcome, but do not replace principles of resuscitation.
Where to now with carbon monoxide poisoning?
Authors: Scheinkestel Carlos D , Jones Kerry , Myles Paul S , Cooper D Jamie , Millar Ian L , Tuxen David V
Published: April 2004

The controversy regarding the role of hyperbaric oxygen (HBO) in the treatment of carbon monoxide (CO) poisoning has been re‐ignited following the publication of a further randomized controlled trial by Weaver et al., the results of which appear to conflict with our findings. Comparative analysis suggests that the apparent outcome differences may be secondary to the design, analysis and interpretation of the results of the two studies. Following careful analysis of these two papers and further results from a study by Raphael et al on 385 CO‐poisoned patients, we can still find no convincing evidence favouring HBO therapy. Pending further research to determine optimal oxygen therapy for CO‐poisoning, current therapy should involve stratifying patients for risk of a poor outcome.

This stratification may be aided by the evolving availability of biochemical markers of brain injury and the finding that patients with transient loss of consciousness and poor performance on neuropsychological tests of the supervisory attention system are at higher risk of neuropsychological sequelae. We propose that those patients most at risk be admitted and receive more prolonged normobaric oxygen therapy whilst those with more minor CO‐poisoning should be provided with normobaric oxygen of no less than 6 h duration and certainly until sign and symptom free.
Developing a decision tree algorithm for the diagnosis of suspected spider bites
Authors: Isbister Geoffrey K , Sibbritt David
Published: April 2004

Objective:  To develop a diagnostic algorithm (decision tree) to improve the ability to identify or predict medically important spider bites (funnel‐web and redback spiders) from information about the circumstances and initial clinical effects of spider bites.

Methods:  A dataset of definite spider bites with expert identification of all spiders was used from a previous Australia‐wide prospective study. Spider bites were categorized as: big black spider (BBS), redback spider (RED) and other spider (OTH). Big black spider included funnel‐web spiders (most medically significant), but also other spiders of similar appearance. Fifteen predictor variables were based on univariate analysis from previous studies and clinical experience. They included information about the circumstances and early clinical effects of bites. The data were analyzed using CART® (Classification and Regression Trees), a ‘decision tree’ algorithm used to create a tree‐like structure to describe a data set.

Results:  Of 789 spider bites there were 49 (6.2%) bites by BBS, 68 (8.6%) bites by RED and 672 (85.2%) bites by OTH. A decision tree was developed that included six predictor variables (fang marks/bleeding; state/territory; local diaphoresis; month; time of day; and proximal or distal bite region). The decision tree accurately classified 47 out of the 49 (96%) BBS, and no funnel‐web spiders were incorrectly classified (100% sensitivity). Two hundred and forty‐four of 789 were classified as OTH and included no BBS.

Conclusions:  A decision tree based on a small amount of information about the circumstances and early clinical effects of spider bites safely predicted all funnel‐web spider bites. Application of this algorithm would allow the early institution of appropriate treatment for funnel‐web spider bites and the immediate discharge of 31% as other spider bites (reassurance only).
Prolonged pre‐procedure fasting time is unnecessary when using titrated intravenous ketamine for paediatric procedural sedation
Authors: Treston Greg
Published: April 2004

Background: Paediatric procedural sedation (PPS) is a common procedure in most general EDs. Many departmental guidelines suggest mandatory fasting times for children undergoing PPS, in an attempt to decrease the incidence of postoperative vomiting and (theoretically) aspiration pneumonitis, despite there being little or no evidence in the literature to support these mandatory fasting times.

Objectives: To prospectively address the relationship between preprocedure fasting time and intraprocedure or postprocedure vomiting in children aged 1–12 years undergoing procedural sedation with intravenous ketamine in the ED.

Methods: From January 1999 to May 2000 all children presenting to the Royal Darwin Hospital Emergency Department with a condition requiring ketamine PPS were enrolled for data collection after parental consent was obtained. Titrated intravenous ketamine was administered via protocol. Prospective ED procedural sedation data collection forms of 272 consecutive cases of titrated intravenous ketamine sedation were reviewed.

Results: Fasting time was accurately recorded on 257 (95%) data collection forms. There was no intraprocedure vomiting. Overall rate of postprocedure vomiting was 13.9%. No statistically significant association between decreased fasting time and increased incidence of vomiting was found. In fact, there was a trend towards increased incidence of vomiting with increased fasting time (P = 0.08). The rate of vomiting of those children fasted 3 h or greater preprocedure (20/127 or 15.8%) was over twice the rate of those fasted less than 1 hour (2/30 or 6.6%). Incidence of vomiting was significantly associated with increasing age (P = 0.0007). No clinically evident aspiration pneumonitis occurred.

Conclusion: Prolonged preprocedure fasting time did not reduce the incidence of postprocedure vomiting in this case series; to the contrary there was a increased incidence of vomiting with longer fasting times (P = 0.08). There was an increase in postprocedure vomiting with increasing age of the patients.
Study of the Ecology of Fresh Sausages and Characterization of Populations of Lactic Acid Bacteria by Molecular Methods
Authors: Cocolin Luca , Rantsiou Kalliopi , Iacumin Lucilla , Urso Rosalinda , Cantoni Carlo , Comi Giuseppe
Published: April 2004

In this study, a polyphasic approach was used to study the ecology of fresh sausages and to characterize populations of lactic acid bacteria (LAB). The microbial profile of fresh sausages was monitored from the production day to the 10th day of storage at 4°C. Samples were collected on days 0, 3, 6, and 10, and culture-dependent and -independent methods of detection and identification were applied. Traditional plating and isolation of LAB strains, which were subsequently identified by molecular methods, and the application of PCR-denaturing gradient gel electrophoresis (DGGE) to DNA and RNA extracted directly from the fresh sausage samples allowed the study in detail of the changes in the bacterial and yeast populations during storage.
Brochothrix thermosphacta
and
Lactobacillus sakei
were the main populations present. In particular,
B. thermosphacta
was present throughout the process, as determined by both DNA and RNA analysis. Other bacterial species, mainly
Staphylococcus xylosus
,
Leuconostoc mesenteroides
, and
L. curvatus
, were detected by DGGE. Moreover, an uncultured bacterium and an uncultured
Staphylococcus
sp. were present, too. LAB strains isolated at day 0 were identified as
Lactococcus lactis
subsp.
lactis
,
L. casei
, and
Enterococcus casseliflavus
, and on day 3 a strain of
Leuconostoc mesenteroides
was identified. The remaining strains isolated belonged to
L. sakei
. Concerning the yeast ecology, only
Debaryomyces hansenii
was established in the fresh sausages.
Capronia mansonii
was initially present, but it was not detected after the first 3 days. At last,
L. sakei
isolates were characterized by randomly amplified polymorphic DNA PCR and repetitive DNA element PCR. The results obtained underlined how different populations took over at different steps of the process. This is believed to be the result of the selection of the particular population, possibly due to the low storage temperature employed.
Exposure ofSaccharomyces cerevisiaeto Acetaldehyde Induces Sulfur Amino Acid Metabolism and Polyamine Transporter Genes, Which Depend on Met4p and Haa1p Transcription Factors, Respectively
Authors: Aranda Agustín , del Olmo Marcel-lí
Published: April 2004

Acetaldehyde is a toxic compound produced bySaccharomyces cerevisiaecells under several growth conditions. The adverse effects of this molecule are important, as significant amounts accumulate inside the cells. By means of global gene expression analyses, we have detected the effects of acetaldehyde addition in the expression of about 400 genes. Repressed genes include many genes involved in cell cycle control, cell polarity, and the mitochondrial protein biosynthesis machinery. Increased expression is displayed in many stress response genes, as well as other families of genes, such as those encoding vitamin B1 biosynthesis machinery and proteins for aryl alcohol metabolism. The induction of genes involved in sulfur metabolism is dependent on Met4p and other well-known factors involved in the transcription ofMETgenes under nonrepressing conditions of sulfur metabolism. Moreover, the deletion ofMET4leads to increased acetaldehyde sensitivity.TPOgenes encoding polyamine transporters are also induced by acetaldehyde; in this case, the regulation is dependent on the Haa1p transcription factor. In this paper, we discuss the connections between acetaldehyde and the processes affected by this compound in yeast cells with reference to the microarray data.
Short Fractions of Oligofructose Are Preferentially Metabolized by
Bifidobacterium animalis
DN-173 010
Authors: Van der Meulen Roel , Avonts Lazlo , De Vuyst Luc
Published: April 2004

The growth of
Bifidobacterium animalis
DN-173 010 on different energy sources was studied through small- and large-scale fermentations. Growth on both more common energy sources (glucose, fructose, galactose, lactose, and sucrose) and inulin-type fructans was examined. High-performance liquid chromatography analysis was used to investigate the kinetics. Gas chromatography was used to determine the fructan degradation during the fermentation process.
B. animalis
DN-173 010 was unable to grow on a medium containing glucose as the sole energy source. In general, monosaccharides were poor growth substrates for the
B. animalis
strain. The fermentations with the inulin-type fructans resulted in changes in both growth and metabolite production due to the preferential metabolism of certain fructans, especially the short-chain oligomers. Only after depletion of the shorter chains were the larger fractions also metabolized, although to a lesser extent. Acetic acid was the major metabolite produced during all fermentation experiments. At the beginning of the fermentation, high levels of lactic acid were produced, which were partially replaced by formic acid at later stages. This suggests a shift in sugar metabolism to gain additional ATP that is necessary for growth on oligofructose, which is metabolized more slowly.
The
htrA
(
degP
) Gene of
Listeria monocytogenes
10403S Is Essential for Optimal Growth under Stress Conditions
Authors: Wonderling Laura D. , Wilkinson Brian J. , Bayles Darrell O.
Published: April 2004

This report describes a mutant of
Listeria monocytogenes
strain 10403S (serotype 1/2a) with a defective response to conditions of high osmolarity, an environment that
L. monocytogenes
encounters in some ready-to-eat foods. A library of
L. monocytogenes
clones mutagenized with Tn
917
was generated and scored for sensitivity to 4% NaCl in order to identify genes responsible for growth or survival in elevated-NaCl environments. One of the
L. monocytogenes
Tn
917
mutants, designated strain OSM1, was selected, and the gene interrupted by the transposon was sequenced. A BLAST search with the putative translated amino acid sequence indicated that the interrupted gene product was a homolog of
htrA
(
degP
), a gene coding for a serine protease identified as a stress response protein in several gram-positive and gram-negative bacteria. An
htrA
deletion strain, strain LDW1, was constructed, and the salt-sensitive phenotype of this strain was complemented by introduction of a plasmid carrying the wild-type
htrA
gene, demonstrating that
htrA
is necessary for optimal growth under conditions of osmotic stress. Additionally, strain LDW1 was tested for its response to temperature and H
2
O
2
stresses. The results of these growth assays indicated that strain LDW1 grew at a lower rate than the wild-type strain at 44°C but at a rate similar to that of the wild-type strain when incubated at 4°C. In addition, strain LDW1 was significantly more sensitive to a 52°C heat shock than the wild-type strain. Strain LDW1 was also defective in its response to H
2
O
2
challenge at 37°C, since 100 or 150 μg of H
2
O
2
was more inhibitory for the growth of strain LDW1 than for that of the parent strain. The stress response phenotype observed for strain LDW1 is similar to that observed for other HtrA
−
organisms, which suggests that
L. monocytogenes
HtrA may play a role in degrading misfolded proteins that accumulate under stress conditions.
Prolonged Maltose-Limited Cultivation of
Saccharomyces cerevisiae
Selects for Cells with Improved Maltose Affinity and Hypersensitivity
Authors: Jansen Mickel L. A. , Daran-Lapujade Pascale , de Winde Johannes H. , Piper Matthew D. W. , Pronk Jack T.
Published: April 2004

Prolonged cultivation (>25 generations) of
Saccharomyces cerevisiae
in aerobic, maltose-limited chemostat cultures led to profound physiological changes. Maltose hypersensitivity was observed when cells from prolonged cultivations were suddenly exposed to excess maltose. This substrate hypersensitivity was evident from massive cell lysis and loss of viability. During prolonged cultivation at a fixed specific growth rate, the affinity for the growth-limiting nutrient (i.e., maltose) increased, as evident from a decreasing residual maltose concentration. Furthermore, the capacity of maltose-dependent proton uptake increased up to 2.5-fold during prolonged cultivation. Genome-wide transcriptome analysis showed that the increased maltose transport capacity was not primarily due to increased transcript levels of maltose-permease genes upon prolonged cultivation. We propose that selection for improved substrate affinity (ratio of maximum substrate consumption rate and substrate saturation constant) in maltose-limited cultures leads to selection for cells with an increased capacity for maltose uptake. At the same time, the accumulative nature of maltose-proton symport in
S. cerevisiae
leads to unrestricted uptake when maltose-adapted cells are exposed to a substrate excess. These changes were retained after isolation of individual cell lines from the chemostat cultures and nonselective cultivation, indicating that mutations were involved. The observed trade-off between substrate affinity and substrate tolerance may be relevant for metabolic engineering and strain selection for utilization of substrates that are taken up by proton symport.
Stratification of Activity and Bacterial Community Structure in Biofilms Grown on Membranes Transferring Oxygen
Authors: Cole Alina C. , Semmens Michael J. , LaPara Timothy M.
Published: April 2004

Previous studies have shown that membrane-aerated biofilm (MAB) reactors can simultaneously remove carbonaceous and nitrogenous pollutants from wastewater in a single reactor. Oxygen is provided to MABs through gas-permeable membranes such that the region nearest the membrane is rich in oxygen but low in organic carbon, whereas the outer region of the biofilm is void of oxygen but rich in organic carbon. In this study, MABs were grown under similar conditions but at two different fluid velocities (2 and 14 cm s
−1
) across the biofilm. MABs were analyzed for changes in biomass density, respiratory activity, and bacterial community structure as functions of biofilm depth. Biomass density was generally highest near the membrane and declined with distance from the membrane. Respiratory activity exhibited a hump-shaped profile, with the highest activity occurring in the middle of the biofilm. Community analysis by PCR cloning and PCR-denaturing gradient gel electrophoresis of 16S rRNA genes demonstrated substantial stratification of the community structure across the biofilm. Population profiles were also generated by competitive quantitative PCR of gene fragments specific for ammonia-oxidizing bacteria (AOB) (
amoA
) and denitrifying bacteria (
nirK
and
nirS
). At a flow velocity of 14 cm s
−1
, AOB were found only near the membrane, whereas denitrifying bacteria proliferated in the anoxic outer regions of the biofilm. In contrast, at a flow velocity of 2 cm s
−1
, AOB were either not detected or detected at a concentration near the detection limit. This study suggests that, under the appropriate conditions, both AOB and denitrifying bacteria can coexist within an MAB.
Cross Talk between 2,4-Diacetylphloroglucinol-Producing Biocontrol Pseudomonads on Wheat Roots
Authors: Maurhofer Monika , Baehler Eric , Notz Regina , Martinez Vicente , Keel Christoph
Published: April 2004

The performance of
Pseudomonas
biocontrol agents may be improved by applying mixtures of strains which are complementary in their capacity to suppress plant diseases. Here, we have chosen the combination of
Pseudomonas fluorescens
CHA0 with another well-characterized biocontrol agent,
P. fluorescens
Q2-87, as a model to study how these strains affect each other's expression of a biocontrol trait. In both strains, production of the antimicrobial compound 2,4-diacetylphloroglucinol (DAPG) is a crucial factor contributing to the suppression of root diseases. DAPG acts as a signaling compound inducing the expression of its own biosynthetic genes. Experimental setups were developed to investigate whether, when combining strains CHA0 and Q2-87, DAPG excreted by one strain may influence expression of DAPG-biosynthetic genes in the other strain in vitro and on the roots of wheat. DAPG production was monitored by observing the expression of
lacZ
fused to the biosynthetic gene
phlA
of the respective strain. Dual-culture assays in which the two strains were grown in liquid medium physically separated by a membrane revealed that Q2-87 but not its DAPG-negative mutant Q2-87::Tn
5
-1 strongly induced
phlA
expression in a Δ
phlA
mutant of strain CHA0. In the same way,
phlA
expression in a Q2-87 background was induced by DAPG produced by CHA0. When coinoculated onto the roots of wheat seedlings grown under gnotobiotic conditions, strains Q2-87 and CHA0, but not their respective DAPG-negative mutants, were able to enhance
phlA
expression in each other. In summary, we have established that two nonrelated pseudomonads may stimulate each other in the expression of an antimicrobial compound important for biocontrol. This interpopulation communication occurs in the rhizosphere, i.e., at the site of pathogen inhibition, and is mediated by the antimicrobial compound itself acting as a signal exchanged between the two pseudomonads.
Evolution of the Core Genome of
Pseudomonassyringae
, a Highly Clonal, Endemic PlantPathogen
Authors: Sarkar Sara F. , Guttman David S.
Published: April 2004

Pseudomonas
syringae
is a common foliar bacterium responsible for many
important plant diseases. We studied the population structure and
dynamics of the core genome of
P. syringae
via multilocus
sequencing typing (MLST) of 60 strains, representing 21 pathovars and 2
nonpathogens, isolated from a variety of plant hosts. Seven
housekeeping genes, dispersed around the
P. syringae
genome,
were sequenced to obtain 400 to 500 nucleotides per gene. Forty unique
sequence types were identified, with most strains falling into one of
four major clades. Phylogenetic and maximum-likelihood analyses
revealed a remarkable degree of congruence among the seven genes,
indicating a common evolutionary history for the seven loci. MLST and
population genetic analyses also found a very low level of
recombination. Overall, mutation was found to be approximately four
times more likely than recombination to change any single nucleotide. A
skyline plot was used to study the demographic history of
P.
syringae
. The species was found to have maintained a constant
population size over time. Strains were also found to remain
genetically homogeneous over many years, and when isolated from sites
as widespread as the United States and Japan. An analysis of molecular
variance found that host association explains only a small proportion
of the total genetic variation in the sample. These analyses reveal
that with respect to the core genome,
P. syringae
is a highly
clonal and stable species that is endemic within plant populations, yet
the genetic variation seen in these genes only weakly predicts host
association.
Size and UV Germicidal Irradiation Susceptibility of
Serratia marcescens
when Aerosolized from Different Suspending Media
Authors: Lai Ka M. , Burge Harriet A. , First Melvin W.
Published: April 2004

Experimental systems have been built in laboratories worldwide to investigate the influence of various environmental parameters on the efficacy of UV germicidal irradiation (UVGI) for deactivating airborne microorganisms. It is generally recognized that data from different laboratories might vary significantly due to differences in systems and experimental conditions. In this study we looked at the effect of the composition of the suspending medium on the size and UVGI susceptibility of
Serratia marcescens
in an experimental system built in our laboratory.
S. marcescens
was suspended in (i) distilled water, (ii) phosphate buffer, (iii) 10% fetal calf serum, (iv) phosphate-buffered saline (saline, 0.8% sodium chloride), and (v) synthetic saliva (phosphate-buffered saline with 10% fetal calf serum). At low humidity (36%),
S. marcescens
suspended in water-only medium was the most susceptible to UVGI, followed by those in serum-only medium. The count median diameters (CMDs) for culturable particles from water-only and serum-only media were 0.88 and 0.95 μm, respectively, with the measurements based on their aerodynamic behavior. The bacteria suspended in phosphate buffer, synthetic saliva, and phosphate-buffered saline had similar UVGI susceptibility and CMD at 1.0, 1.4, and 1.5 μm, respectively. At high humidity (68%) the CMD of the particles increased by 6 to 16%, and at the same time UVGI susceptibility decreased, with the magnitude of decrease related to the type of suspending medium. In conclusion, the choice of suspending medium influenced both size and UVGI susceptibility of
S. marcescens
. These data are valuable for making comparisons and deciding on the use of an appropriate medium for various applications.
Characterization of Protistan Assemblages in the Ross Sea, Antarctica, by Denaturing Gradient Gel Electrophoresis
Authors: Gast Rebecca J. , Dennett Mark R. , Caron David A.
Published: April 2004

The diversity of protistan assemblages has traditionally been studied using microscopy and morphological characterization, but these methods are often inadequate for ecological studies of these communities because most small protists inherently lack adequate taxonomic characters to facilitate their identification at the species level and many protistan species also do not preserve well. We have therefore used a culture-independent approach (denaturing gradient gel electrophoresis [DGGE]) to obtain an assessment of the genetic composition and distribution of protists within different microhabitats (seawater, meltwater or slush on sea-ice floes, and ice) of the Ross Sea, Antarctica. Samples of the same type (e.g., water) shared more of the same bands than samples of different types (e.g., ice versus water), despite being collected from different sites. These findings imply that samples from the same environment have a similar protistan species composition and that the type of microenvironment significantly influences the protistan species composition of these Antarctic assemblages. It should be noted that a large number of bands among the samples within each microhabitat were distinct, indicating the potential presence of significant genetic diversity within each microenvironment. Sequence analysis of selected DGGE bands revealed sequences that represent diatoms, dinoflagellates, ciliates, flagellates, and several unidentified eukaryotes.
Stationary-Phase Quorum-Sensing Signals Affect Autoinducer-2 and Gene Expression in
Escherichia coli
Authors: Ren Dacheng , Bedzyk Laura A. , Ye Rick W. , Thomas Stuart M. , Wood Thomas K.
Published: April 2004

Quorum sensing via autoinducer-2 (AI-2) has been identified in different strains, including those from
Escherichia
,
Vibrio
,
Streptococcus
, and
Bacillus
species, and previous studies have suggested the existence of additional quorum-sensing signals working in the stationary phase of
Escherichia coli
cultures. To investigate the presence and global effect of these possible quorum-sensing signals other than AI-2, DNA microarrays were used to study the effect of stationary-phase signals on the gene expression of early exponential-phase cells of the AI-2-deficient strain
E. coli
DH5α. For statistically significant differential gene expression (
P
< 0.05), 14 genes were induced by supernatants from a stationary culture and 6 genes were repressed, suggesting the involvement of indole (induction of
tnaA
and
tnaL
) and phosphate (repression of
phoA
,
phoB
, and
phoU
). To study the stability of the signals, the stationary-phase supernatant was autoclaved and was used to study its effect on
E. coli
gene expression. Three genes were induced by autoclaved stationary-phase supernatant, and 34 genes were repressed. In total, three genes (
ompC
,
ptsA
, and
btuB
) were induced and five genes (
nupC
,
phoB
,
phoU
,
argT
, and
ompF
) were repressed by both fresh and autoclaved stationary-phase supernatants. Furthermore, supernatant from
E. coli
DH5α stationary culture was found to repress
E. coli
K-12 AI-2 concentrations by 4.8-fold ± 0.4-fold, suggesting that an additional quorum-sensing system in
E. coli
exists and that gene expression is controlled as a network with different signals working at different growth stages.
Identification of the Bacterial Community of Maple Sap by Using Amplified Ribosomal DNA (rDNA) Restriction Analysis and rDNA Sequencing
Authors: Lagacé L. , Pitre M. , Jacques M. , Roy D.
Published: April 2004

The bacterial community of maple sap was characterized by analysis of samples obtained at the taphole of maple trees for the 2001 and 2002 seasons. Among the 190 bacterial isolates, 32 groups were formed according to the similarity of the banding patterns obtained by amplified ribosomal DNA restriction analysis (ARDRA). A subset of representative isolates for each ARDRA group was identified by 16S rRNA gene fragment sequencing. Results showed a wide variety of organisms, with 22 different genera encountered.
Pseudomonas
and
Ralstonia
, of the γ
-
and β
-Proteobacteria,
respectively, were the most frequently encountered genera. Gram-positive bacteria were also observed, and
Staphylococcus
,
Plantibacter
, and
Bacillus
were the most highly represented genera. The sampling period corresponding to 50% of the cumulative sap flow percentage presented the greatest bacterial diversity according to its Shannon diversity index value (1.1). γ
-Proteobacteria
were found to be dominant almost from the beginning of the season to the end. These results are providing interesting insights on maple sap microflora that will be useful for further investigation related to microbial contamination and quality of maple products and also for guiding new strategies on taphole contamination control.
Receptor Binding Domain ofEscherichia coliF18 Fimbrial Adhesin FedF Can Be both Efficiently Secreted and Surface Displayed in a Functional Form inLactococcus lactis
Authors: Lindholm Agneta , Smeds Andreas , Palva Airi
Published: April 2004

Adherence of F18 fimbrialEscherichia colito porcine intestinal epithelial cells is mediated by the adhesin (FedF) of F18 fimbriae. In a previous study, we demonstrated the specificity of the amino acid residues between 60 and 109 as the receptor binding domain of FedF. In this study, different expression, secretion, and anchoring systems for the receptor binding domain of the FedF adhesin inLactococcus lactiswere evaluated. Two partially overlapping receptor binding domains (42 and 62 amino acid residues) were expressed as fusions withL. lactissubsp.cremorisprotein PrtP for evaluation of secretion efficiency. To evaluate the cell surface display of these FedF-PrtP fusions, they were further combined with different lengths of PrtP spacers fused with either theL. lactisAcmA anchor or the PrtP cell wall binding domain. An HtrA-defectiveL. lactisNZ9000 mutant was constructed to determine its effect on the level of secreted or anchored fusion proteins. RecombinantL. lactisclones secreting the receptor binding domain of F18 fimbriae as a fusion with the H domains ofL. lactisprotein PrtP were first constructed by using two different signal peptides. FedF-PrtP fusions, directed by the signal sequence ofL. brevisSlpA, were throughout found to be secreted at significantly higher quantities than corresponding fusions with the signal peptide ofL. lactisUsp45. In the surface display systems tested, theL. lactisAcmA anchor performed significantly better, particularly in theL. lactisNZ9000ΔhtrAstrain, compared to theL. lactisPrtP anchor region. Of the cell surface display constructs with the AcmA anchor, only those with the longest PrtP spacer regions resulted in efficient binding of recombinantL. lactiscells to porcine intestinal epithelial cells. These results confirmed that it is possible to efficiently produce the receptor binding domain of the F18 adhesin in a functionally active form inL. lactis.
Effect of Trophic Status on the Culturability and Activity of Bacteria from a Range of Lakes in the English Lake District
Authors: Porter Jonathan , Morris Samantha A. , Pickup Roger W.
Published: April 2004

The bacterioplankton from a number of lakes that differed in nutrient status in the English Lake District was examined with a number of techniques for enumeration and activity assessment. Natural water samples showed a clear correlation between total counts and trophic status. Esterase activity measurements with Chemchrome B were able to distinguish high- and low-nutrient-status lakes, whereas tetrazolium salt (5-cyano-2,3-ditoyltetrazolium chloride) reduction, the direct viable count-cell elongation assay, and culturability measurements could not. Tetrazolium salt reduction and esterase activity measurements labeled a significant number of cells from water of all nutrient levels, whereas the direct viable count-cell elongation method was of use only in oligotrophic waters. Size fractionation of samples showed that the culturable cells were retained by the larger filters, especially in nutrient-rich waters. Esterase activity measurements also favored the larger cells. The differences observed between assays using water that differed in trophic status raise questions about the use of these tests as a definitive measure of viability.
Characterization ofFerroplasmaIsolates andFerroplasma acidarmanussp. nov., Extreme Acidophiles from Acid Mine Drainage and Industrial Bioleaching Environments
Authors: Dopson Mark , Baker-Austin Craig , Hind Andrew , Bowman John P. , Bond Philip L.
Published: April 2004

Three recently isolated extremely acidophilic archaeal strains have been shown to be phylogenetically similar toFerroplasma acidiphilumYTby 16S rRNA gene sequencing. All fourFerroplasmaisolates were capable of growing chemoorganotrophically on yeast extract or a range of sugars and chemomixotrophically on ferrous iron and yeast extract or sugars, and isolate “Ferroplasma acidarmanus” Fer1Trequired much higher levels of organic carbon. All four isolates were facultative anaerobes, coupling chemoorganotrophic growth on yeast extract to the reduction of ferric iron. The temperature optima for the four isolates were between 35 and 42°C and the pH optima were 1.0 to 1.7, and “F. acidarmanus” Fer1Twas capable of growing at pH 0. The optimum yeast extract concentration for “F. acidarmanus” Fer1Twas higher than that for the other three isolates. Phenotypic results suggested that isolate “F. acidarmanus” Fer1Tis of a different species than the other three strains, and 16S rRNA sequence data, DNA-DNA similarity values, and two-dimensional polyacrylamide gel electrophoresis protein profiles clearly showed that strains DR1, MT17, and YTgroup as a single species. “F. acidarmanus” Fer1Tgroups separately, and we propose the new species “F. acidarmanus” Fer1Tsp. nov.
Influence of Environmental Factors and Human Activity on the Presence of
Salmonella
Serovars in a Marine Environment
Authors: Martinez-Urtaza Jaime , Saco Montserrat , de Novoa Jacobo , Perez-Piñeiro Pelayo , Peiteado Jesus , Lozano-Leon Antonio , Garcia-Martin Oscar
Published: April 2004

The temporal and spatial distribution of
Salmonella
contamination in the coastal waters of Galicia (northwestern Spain) relative to contamination events with different environmental factors (temperature, wind, hours of sunlight, rainfall, and river flow) were investigated over a 4-year period. Salmonellae were isolated from 127 of 5,384 samples of molluscs and seawater (2.4%), and no significant differences (
P
< 0.05) between isolates obtained in different years were observed. The incidence of salmonellae was significantly higher in water column samples (2.9%) than in those taken from the marine benthos (0.7%). Of the 127 strains of
Salmonella
isolated, 20 different serovars were identified.
Salmonella enterica
serovar Senftenberg was the predominant serovar, being represented by 54 isolates (42.5%), followed by serovar Typhimurium (19 isolates [15%]) and serovar Agona (12 isolates [9.4%]). Serovar Senftenberg was detected at specific points on the coast and could not be related to any of the environmental parameters analyzed. All serovars except
Salmonella
serovar Senftenberg were found principally in the southern coastal areas close to the mouths of rivers, and their incidence was associated with high southwestern wind and rainfall. Using multiple logistic regression analysis models, the prevalence of salmonellae was best explained by environmental parameters on the day prior to sampling. Understanding this relationship may be useful for the control of molluscan shellfish harvests, with wind and rainfall serving as triggers for closure.
Immunodetection of the Bacteriocin Lacticin RM: Analysis of the Influence of Temperature and Tween 80 on Its Expression and Activity
Authors: Keren Tomer , Yarmus Merav , Halevy Galia , Shapira Roni
Published: April 2004

Immunoassays with specific antibodies offer higher sensitivity than do bioassays with indicator strains in the detection and quantification of several bacteriocins. Here we present the purification of lacticin RM and the production of specific polyclonal antibodies to a synthetic peptide resembling an internal fragment of the mature bacteriocin. The specificity and sensitivity of the generated polyclonal antibodies were evaluated in various immunoassays. The detection limits of lacticin RM were found to be 1.9, 0.16, and 0.18 μg ml
−1
for Western blot, immuno-dot blot, and noncompetitive indirect enzyme-linked immunosorbent assays, respectively. Immunoassay sensitivities were 12.5-fold higher than that of the agar diffusion test (ADT). The production of lacticin RM showed temperature dependency, with 3, 4.2, 12.7, 28.9, 37.8, and 12 μg ml
−1
at 37, 30, 20, 15, 10, and 4°C, respectively. Temperature-stability analysis demonstrated that lacticin RM is sensitive to mild temperature, but the loss of activity does not seem to result from protein degradation. Tween 80 increased the concentration of lacticin RM eightfold and probably affected the results of the ADT either by enhancing the activity of lacticin RM or by increasing the sensitivity of the indicator strain. The use of antibodies for the specific detection and quantification of lacticin RM can expand our knowledge of its production and stability, with important implications for further investigation and future application.