bluuebunny/crossref_metadata_2025_split huggingface dataset:
Phenotypic and Genotypic Characteristics and Epidemiological Significance ofctx+Strains ofVibrio choleraeIsolated from Seafood in Malaysia
Authors: Chen Chien-Hsien , Shimada Toshio , Elhadi Nasreldin , Radu Son , Nishibuchi Mitsuaki 
Published: April 2004

ABSTRACTOf 97 strains ofVibrio choleraeisolated from various seafoods in Malaysia in 1998 and 1999, 20 strains carried thectxgene and produced cholera toxin. Fourteen, one, and five of these toxigenic strains belonged to the O139, O1 Ogawa, and rough serotypes, respectively. The rough strains had therfbgene of the O1 serotype. The toxigenic strains varied in their biochemical characteristics, the amount of cholera toxin produced, their antibiograms, and the presence or absence of the pTLC plasmid sequence. DNA fingerprinting analysis by arbitrarily primed PCR, ribotyping, and a pulsed-field gel electrophoresis method classified the toxigenic strains into 3, 7, and 10 types, respectively. The relatedness of these toxigenic strains to clinical strains isolated in other countries and from international travelers was examined by using a dendrogram constructed from the pulsed-field gel electrophoresis profiles. The results of the examination of the antibiogram and the possession of the toxin-linked cryptic plasmid were consistent with the dendrogram-based relatedness: the O139 strains isolated from Malaysian seafoods could be separated into two groups that appear to have been introduced from the Bengal area independently. The rough strains of Malaysian seafood origin formed one group and belonged to a cluster unique to the Thailand-Malaysia-Laos region, and this group may have persisted in this area for a long period. The single O1 Ogawa strain detected in Malaysian seafood appears to have an origin and route of introduction different from those of the O139 and the rough strains.
Mycobacteria in Water and Loose Deposits of Drinking Water Distribution Systems in Finland
Authors: Torvinen Eila , Suomalainen Sini , Lehtola Markku J. , Miettinen Ilkka T. , Zacheus Outi , Paulin Lars , Katila Marja-Leena , Martikainen Pertti J. 
Published: April 2004

ABSTRACT

Drinking water distribution systems were analyzed for viable counts of mycobacteria by sampling water from waterworks and in different parts of the systems. In addition, loose deposits collected during mechanical cleaning of the main pipelines were similarly analyzed. The study covered 16 systems at eight localities in Finland. In an experimental study, mycobacterial colonization of biofilms on polyvinyl chloride tubes in a system was studied. The isolation frequency of mycobacteria increased from 35% at the waterworks to 80% in the system, and the number of mycobacteria in the positive samples increased from 15 to 140 CFU/liter, respectively. Mycobacteria were isolated from all 11 deposits with an accumulation time of tens of years and from all 4 deposits which had accumulated during a 1-year follow-up time. The numbers of mycobacteria were high in both old and young deposits (medians, 1.8 × 10
5
and 3.9 × 10
5
CFU/g [dry weight], respectively). Both water and deposit samples yielded the highest numbers of mycobacteria in the systems using surface water and applying ozonation as an intermediate treatment or posttreatment. The number and growth of mycobacteria in system waters correlated strongly with the concentration of assimilable organic carbon in the water leaving the waterworks. The densities of mycobacteria in the developing biofilms were highest at the distal sites of the systems. Over 90% of the mycobacteria isolated from water and deposits belonged to
Mycobacterium lentiflavum
,
M. tusciae
,
M. gordonae
, and a previously unclassified group of mycobacteria. Our results indicate that drinking water systems may be a source for recently discovered new mycobacterial species.
Protective Effect of Sucrose and Sodium Chloride for
Lactococcus lactis
during Sublethal and Lethal High-Pressure Treatments
Authors: Molina-Höppner Adriana , Doster Wolfgang , Vogel Rudi F. , Gänzle Michael G. 
Published: April 2004

ABSTRACT

The bactericidal effect of hydrostatic pressure is reduced when bacteria are suspended in media with high osmolarity. To elucidate mechanisms responsible for the baroprotective effect of ionic and nonionic solutes,
Lactococcus lactis
was treated with pressures ranging from 200 to 600 MPa in a low-osmolarity buffer or with buffer containing 0.5 M sucrose or 4 M NaCl. Pressure-treated cells were characterized in order to determine viability, the transmembrane difference in pH (ΔpH), and multiple-drug-resistance (MDR) transport activity. Furthermore, pressure effects on the intracellular pH and the fluidity of the membrane were determined during pressure treatment. In the presence of external sucrose and NaCl, high intracellular levels of sucrose and lactose, respectively, were accumulated by
L. lactis
; 4 M NaCl and, to a lesser extent, 0.5 M sucrose provided protection against pressure-induced cell death. The transmembrane ΔpH was reversibly dissipated during pressure treatment in any buffer system. Sucrose but not NaCl prevented the irreversible inactivation of enzymes involved in pH homeostasis and MDR transport activity. In the presence 0.5 M sucrose or 4 M NaCl, the fluidity of the cytoplasmic membrane was maintained even at low temperatures and high pressure. These results indicate that disaccharides protect microorganisms against pressure-induced inactivation of vital cellular components. The protective effect of ionic solutes relies on the intracellular accumulation of compatible solutes as a response to the osmotic stress. Thus, ionic solutes provide only asymmetric protection, and baroprotection with ionic solutes requires higher concentrations of the osmolytes than of disaccharides.
Tri1
in
Fusarium graminearum
Encodes a P450 Oxygenase
Authors: McCormick S. P. , Harris L. J. , Alexander N. J. , Ouellet T. , Saparno A. , Allard S. , Desjardins A. E. 
Published: April 2004

ABSTRACT

Gibberella zeae
(asexual state
Fusarium graminearum
) is a major causal agent of wheat head blight and maize ear rot in North America and is responsible for contamination of grain with deoxynivalenol and related trichothecene mycotoxins. To identify additional trichothecene biosynthetic genes, cDNA libraries were prepared from fungal cultures under trichothecene-inducing conditions in culture and in planta. A gene designated
LH1
that was highly expressed under these conditions exhibited only moderate (59%) similarity to known trichothecene biosynthetic cytochrome P450s. To determine the function of
LH1
, gene disruptants were produced and assessed for trichothecene production. Gene disruptants no longer produced 15-acetyldeoxynivalenol, which is oxygenated at carbon 7 (C-7) and C-8, but rather accumulated calonectrin and 3-deacetylcalonectrin, which are not oxygenated at either C-7 or C-8. These results indicate that gene
LH1
encodes a cytochrome P450 responsible for oxygenation at one or both of these positions. Despite the relatively low level of DNA and amino acid sequence similarity between the two genes,
LH1
from
G. zeae
is the probable homologue of
Tri1
, which encodes a cytochrome P450 required for C-8 oxygenation in
F. sporotrichioides
.
Use of Whole Cells ofPseudomonas aeruginosafor Synthesis of the Antioxidant Hydroxytyrosol via Conversion of Tyrosol
Authors: Allouche N. , Damak M. , Ellouz R. , Sayadi S. 
Published: April 2004

ABSTRACTFor the first time, a soil bacterium, designatedPseudomonas aeruginosa, was isolated based on its ability to grow on tyrosol as a sole source of carbon and energy. During growth on tyrosol, this strain was capable of promoting the formation of a significant amount of hydroxytyrosol and trace quantities of parahydroxyphenyl acetic acid and 3,4-dihydroxyphenyl acetic acid. The products were confirmed by high-performance liquid chromatography and gas chromatography-mass spectrometry analyses. Using an optimized tyrosol concentration of 2 g liter−1, the maximal hydroxytyrosol yield (80%) was achieved after a 7-h reaction in a growth experiment. To enhance the formation of hydroxytyrosol and prevent its degradation, a resting-cell method usingP. aeruginosawas performed. The growth state of the culture utilized for biomass production, the carbon source on which the biomass was grown, the concentration of the biomass, and the amount of tyrosol that was treated were optimized. The optimal yield of hydroxytyrosol (96%) was obtained after a 7-h reaction using 4 g of tyrosol liter−1and 5 g of cells liter−1pregrown on tyrosol and harvested at the end of the exponential phase. This proposed procedure is an alternative approach to obtain hydroxytyrosol in an environmentally friendly way. In addition, the reaction is easy to perform and can be adapted to a bioreactor for industrial purposes.
Determination of Nitrogen-Fixing Phylotypes in
Lyngbya
sp. and
Microcoleus
chthonoplastes
Cyanobacterial Mats from Guerrero Negro, Baja California, Mexico
Authors: Omoregie Enoma O. , Crumbliss Lori L. , Bebout Brad M. , Zehr Jonathan P. 
Published: April 2004

ABSTRACT

In many environments, biological nitrogen fixation can alleviate nitrogen limitation. The high rates of N
2
fixation often observed in cyanobacterial mats suggest that N
2
fixation may be an important source of N. In this study, organisms expressing
nifH
were identified in a
Lyngbya
sp.- and two
Microcoleus chthonoplastes
-dominated cyanobacterial mats. The pattern of nitrogenase activity was determined for the
Lyngbya
sp. mat and a
Microcoleus chthonoplastes
mat sampled directly in Guerrero Negro, Mexico. Their maximum rates were 23 and 15 μmol of C
2
H
4
m
−2
h
−1
, respectively. The second
Microcoleus
mat, which was maintained in a greenhouse facility, had a maximum rate of 40 μmol of C
2
H
4
m
−2
h
−1
. The overall diel pattern of nitrogenase activity in the three mats was similar, with the highest rates of activity occurring during the dark period. Analysis of
nifH
transcripts by reverse transcription-PCR revealed that several different organisms were expressing
nifH
during the dark period.
nifH
phylotypes recovered from these mats were similar to sequences from the unicellular cyanobacterial genera
Halothece
,
Myxosarcina
, and
Synechocystis,
the filamentous cyanobacterial genera
Plectonema
and
Phormidium
, and several bacterial
nifH
groups. The results of this study indicate that several different organisms, some of which were not previously known to fix nitrogen, are likely to be responsible for the observed dark-period nitrogenase activity in these cyanobacterial mats.
Impact of Consumption of Oligosaccharide-Containing Biscuits on the Fecal Microbiota of Humans
Authors: Tannock Gerald W. , Munro Karen , Bibiloni Rodrigo , Simon Mary A. , Hargreaves Patrick , Gopal Pramod , Harmsen Hermie , Welling Gjalt 
Published: April 2004

ABSTRACT

Human subjects consumed biscuits containing either galacto-oligosaccharides or fructo-oligosaccharides in a double-blinded, crossover study. The impact of supplementing the diet with three biscuits per day on the fecal microbiota was evaluated by selective culture of particular bacterial groups, measurement of β-galactosidase activity, and nucleic acid-based analytical methods (PCR-denaturing gradient gel electrophoresis [PCR-DGGE] and fluorescent in situ hybridization). The composition of the bifidobacterial populations was monitored at the level of species (PCR-DGGE) and strains (pulsed-field gel electrophoresis of DNA digests), and representative cultures were tested quantitatively for their ability to use galacto-oligosaccharides. Technical improvements to DGGE analysis of the microbiota were made by the use of an internal standard that allowed valid comparisons of fragment staining intensities to be made between profiles, the use of S1 nuclease digestion to remove single-stranded DNA to facilitate cloning of DNA sequences cut from gels, and the extraction of RNA to be used as the template in reverse transcription-PCR-DGGE. RNA-DGGE profiles were markedly different (Dice's similarity coefficient, 58.5%) from those generated by DNA-DGGE. Neither the sizes of the bacterial populations nor the DNA-DGGE profiles of the microbiota were altered by the consumption of the biscuits, but the RNA-DGGE profiles were altered by the detection or increased staining intensity of 16S rRNA gene sequences originating from
Bifidobacterium adolescentis
and/or
Colinsella aerofaciens
in the feces of 11 of 15 subjects. β-Galactosidase activity was elevated in the feces of some subjects as a result of biscuit consumption. Subjects differed in the ability of the bifidobacterial strains harbored in their feces to use galacto-oligosaccharides. Our observations suggest that a phylogenetic approach to analysis of the gut ecosystem may not always be optimal and that a more physiological (biochemical) method might be more informative.
Fiber-Degrading Systems of Different Strains of the Genus
Fibrobacter
Authors: Béra-Maillet Christel , Ribot Yves , Forano Evelyne 
Published: April 2004

ABSTRACT

The S85 type strain of
Fibrobacter succinogenes
, a major ruminal fibrolytic species, was isolated 49 years ago from a bovine rumen and has been used since then as a model for extensive studies. To assess the validity of this model, we compared the cellulase- and xylanase-degrading activities of several other
F. succinogenes
strains originating from different ruminants, including recently isolated strains, and looked for the presence of 10 glycoside hydrolase genes previously identified in S85. The NR9
F. intestinalis
type strain, representative of the second species of the genus, was also included in this study. DNA-DNA hybridization and 16S rRNA gene sequencing first classified the strains and provided the phylogenetic positions of isolates of both species. Cellulase and xylanase activity analyses revealed similar activity profiles for all
F. succinogenes
strains. However, the F
E
strain, phylogenetically close to S85, presented a poor xylanolytic system and weak specific activities. Furthermore, the HM2 strain, genetically distant from the other
F. succinogenes
isolates, displayed a larger cellulolytic profile on zymograms and higher cellulolytic specific activity.
F. intestinalis
NR9 presented a higher cellulolytic specific activity and a stronger extracellular xylanolytic activity. Almost all glycoside hydrolase genes studied were found in the
F. succinogenes
isolates by PCR, except in the HM2 strain, and few of them were detected in
F. intestinalis
NR9. As expected, the fibrolytic genes of strains of the genus
Fibrobacter
as well as the cellulase and xylanase activities are better conserved in closely related phylogenetic isolates.
Use of PCR-Restriction Fragment Length Polymorphism of
inlA
for Rapid Screening of
Listeria monocytogenes
Strains Deficient in the Ability To Invade Caco-2 Cells
Authors: Rousseaux S. , Olier M. , Lemaître J. P. , Piveteau P. , Guzzo J. 
Published: April 2004

ABSTRACT

A PCR-restriction fragment length polymorphism (RFLP) method was developed in order to screen a large number of strains for impaired adhesion to epithelial cells due to expression of truncated InlA.
inlA
polymorphism was analyzed by PCR-RFLP in order to correlate
inlA
PCR-RFLP profiles and production of truncated InlA. Thirty-seven
Listeria monocytogenes
strains isolated from various sources, including five noninvasive and two invasive reference strains, were screened. Two endonucleases (AluI and Tsp509I) were used, and they generated five composite profiles. Thirteen
L. monocytogenes
isolates were characterized by two specific PCR-RFLP profiles similar to PCR-RFLP profiles of noninvasive reference strains previously described as strains that produce truncated InlA. Ten of the 13 isolates showed low abilities to invade human epithelial Caco-2 cells. However, 4 of the 13 isolates were able to invade Caco-2 cells like reference strains containing complete InlA. Sequencing of
inlA
and Western blot analysis confirmed that truncated InlA was expressed in the 10
L. monocytogenes
strains which were isolated from food. This PCR-RFLP method allowed us to identify 10 new strains expressing a truncated internalin. Based on the results obtained in this study, the PCR-RFLP method seems to be an interesting method for rapidly screening
L. monocytogenes
strains deficient in the ability to invade Caco-2 cells when a sizeable number of strains are studied.
Spatial and Temporal Distribution of Two Diazotrophic Bacteria in the Chesapeake Bay
Authors: Short Steven M. , Jenkins Bethany D. , Zehr Jonathan P. 
Published: April 2004

ABSTRACT

The aim of this study was to initiate autecological studies on uncultivated natural populations of diazotrophic bacteria by examining the distribution of specific diazotrophs in the Chesapeake Bay. By use of quantitative PCR, the abundance of two
nifH
sequences (907h22 and 912h4) was quantified in water samples collected along a transect from the head to the mouth of the Chesapeake Bay during cruises in April and October 2001 and 2002. Standard curves for the quantitative PCR assays demonstrated that the relationship between gene copies and cycle threshold was linear and highly reproducible from 1 to 10
7
gene copies. The maximum number of 907h22 gene copies detected was approximately 140 ml
−1
and the maximum number of 912h4 gene copies detected was approximately 340 ml
−1
. Sequence 912h4 was most abundant at the mouth of the Chesapeake Bay, and in general, its abundance increased with increasing salinity, with the highest abundances observed in April 2002. Overall, the 907h22 phylotype was most abundant at the mid-bay station. Additionally, 907h22 was most abundant in the April samples from the mid-bay and mouth of the Chesapeake Bay. Despite the fact that the Chesapeake Bay is rarely nitrogen limited, our results show that individual nitrogen-fixing bacteria have distinct nonrandom spatial and seasonal distributions in the Chesapeake Bay and are either distributed by specific physical processes or adapted to different environmental niches.
Ethanol-Mediated Variations in Cellular Fatty Acid Composition and Protein Profiles of Two Genotypically Different Strains of
Escherichia coli
O157:H7
Authors: Chiou R. Y.-Y. , Phillips R. D. , Zhao P. , Doyle M. P. , Beuchat L. R. 
Published: April 2004

ABSTRACT

Two strains of
Escherichia coli
O157:H7 were grown in tryptic soy broth (TSB, pH 7.1) supplemented with 0, 2.5, 5.0, 7.5, and 10% ethanol at 30°C for up to 54 h. Growth rates in TSB supplemented with 0, 2.5, and 5.0% ethanol decreased with an increase in ethanol concentration. Growth was not observed in TSB supplemented with 7.5 or 10% ethanol. The pH of TSB containing 5.0% ethanol decreased to 5.8 within 12 h and then increased to 7.0 at 54 h. The ethanol content in TSB supplemented with 2.5 or 5.0% ethanol did not change substantially during the first 36 h of incubation but decreased slightly thereafter, indicating utilization or degradation of ethanol by both strains. Glucose was depleted in TSB supplemented with 0, 2.5, or 5.0% ethanol within 12 h. Cells grown under ethanol stress contained a higher amount of fatty acids. With the exceptions of
cis
-oleic acid and nonadecanoic acid, larger amounts of fatty acid were present in stationary-phase cells of the two strains grown in TSB supplemented with 5.0% ethanol for 30 h than in cells grown in TSB without ethanol for 22 h. The
trans
-oleic acid content was 10-fold higher in the cells grown in TSB with 5.0% ethanol than those grown in TSB without ethanol. In contrast,
cis
-oleic acid was not detected in ethanol-stressed cells but was present at concentrations of 0.32 and 0.36 mg/g of cells of the two strains grown in TSB without ethanol. Protein content was higher in ethanol-stressed cells than in nonstressed cells. Sodium dodecyl sulfate-polyacrylamide gel electrophoresis protein profiles varied qualitatively as affected by the strain and the presence of ethanol in TSB. An ethanol-mediated protein (28 kDa) was observed in the ethanol-stressed cells but not in control cells. It is concluded that the two test strains of
E. coli
O157:H7 underwent phenotypic modifications in cellular fatty acid composition and protein profiles in response to ethanol stress. The potential for cross protection against subsequent stresses applied in food preservation technologies as a result of these changes is under investigation.
Phenol Hydroxylase and Toluene/
o
-Xylene Monooxygenase from
Pseudomonas stutzeri
OX1: Interplay between Two Enzymes
Authors: Cafaro Valeria , Izzo Viviana , Scognamiglio Roberta , Notomista Eugenio , Capasso Paola , Casbarra Annarita , Pucci Piero , Di Donato Alberto 
Published: April 2004

ABSTRACT

Degradation of aromatic hydrocarbons by aerobic bacteria is generally divided into an upper pathway, which produces dihydroxylated aromatic intermediates by the action of monooxygenases, and a lower pathway, which processes these intermediates down to molecules that enter the citric acid cycle. Bacterial multicomponent monooxygenases (BMMs) are a family of enzymes divided into six distinct groups. Most bacterial genomes code for only one BMM, but a few cases (3 out of 31) of genomes coding for more than a single monooxygenase have been found. One such case is the genome of
Pseudomonas stutzeri
OX1, in which two different monooxygenases have been found, phenol hydroxylase (PH) and toluene/
o
-xylene monooxygenase (ToMO). We have already demonstrated that ToMO is an oligomeric protein whose subunits transfer electrons from NADH to oxygen, which is eventually incorporated into the aromatic substrate. However, no molecular data are available on the structure and on the mechanism of action of PH. To understand the metabolic significance of the association of two similar enzymatic activities in the same microorganism, we expressed and characterized this novel phenol hydroxylase. Our data indicate that the PH P component of PH transfers electrons from NADH to a subcomplex endowed with hydroxylase activity. Moreover, a regulatory function can be suggested for subunit PH M. Data on the specificity and the kinetic constants of ToMO and PH strongly support the hypothesis that coupling between the two enzymatic systems optimizes the use of nonhydroxylated aromatic molecules by the draining effect of PH on the product(s) of oxidation catalyzed by ToMO, thus avoiding phenol accumulation.