bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Associated Bacteria on the Growth and Toxicity of
Alexandrium catenella
Authors: Uribe Paulina , Espejo Romilio T. 
Published: January 2003

ABSTRACT

Saprophytic bacteria in cultures of the marine dinoflagellate
Alexandrium catenella
were removed to assess their effect on growth and paralytic shellfish poisoning toxin production of this dinoflagellate. The actual axenic status was demonstrated by the lack of observable bacteria both immediately after treatment and following extended incubation in the absence of antibiotics. Bacteria were measured by counting CFU and also by epifluorescence microscopy and PCR amplification of bacterial 16S-23S spacer ribosomal DNA to detect noncultivable bacteria. Removal of bacteria did not have any effect on the growth of the dinoflagellate except for the inhibition of
A. catenella
disintegration after reaching the stationary phase. Toxicity was determined in dinoflagellate cell extracts by different methods: high-performance liquid chromatography (HPLC); an electrophysiological test called the Electrotest, which measures the inhibition of saxitoxin-sensitive Na
+
channels expressed in a cell line; and a mouse bioassay, which measures the toxic effect on the whole mammal neuromuscular system. A lower toxicity of the dinoflagellates in axenic culture was observed by these three methods, though the difference was significant only by the mouse bioassay and HPLC methods. Altogether the results indicate that axenic cultures of
A. catenella
are able to produce toxin, though the total toxicity is probably diminished to about one-fifth of that in nonaxenic cultures.
Enzymatic Conversion of Averufin to Hydroxyversicolorone and Elucidation of a Novel Metabolic Grid Involved in Aflatoxin Biosynthesis
Authors: Yabe Kimiko , Chihaya Naomi , Hamamatsu Shioka , Sakuno Emi , Hamasaki Takashi , Nakajima Hiromitsu , Bennett J. W. 
Published: January 2003

ABSTRACT

The pathway from averufin (AVR) to versiconal hemiacetal acetate (VHA) in aflatoxin biosynthesis was investigated by using cell-free enzyme systems prepared from
Aspergillus parasiticus
. When (1′
S
,5′
S
)-AVR was incubated with a cell extract of this fungus in the presence of NADPH, versicolorin A and versicolorin B (VB), as well as other aflatoxin pathway intermediates, were formed. When the same substrate was incubated with the microsome fraction and NADPH, hydroxyversicolorone (HVN) and VHA were formed. However, (1′
R
,5′
R
)-AVR did not serve as the substrate. In cell-free experiments performed with the cytosol fraction and NADPH, VHA, versicolorone (VONE), and versiconol acetate (VOAc) were transiently produced from HVN in the early phase, and then VB and versiconol (VOH) accumulated later. Addition of dichlorvos (dimethyl 2,2-dichlorovinylphosphate) to the same reaction mixture caused transient formation of VHA and VONE, followed by accumulation of VOAc, but neither VB nor VOH was formed. When VONE was incubated with the cytosol fraction in the presence of NADPH, VOAc and VOH were newly formed, whereas the conversion of VOAc to VOH was inhibited by dichlorvos. The purified VHA reductase, which was previously reported to catalyze the reaction from VHA to VOAc, also catalyzed conversion of HVN to VONE. Separate feeding experiments performed with
A. parasiticus
NIAH-26 along with HVN, VONE, and versicolorol (VOROL) demonstrated that each of these substances could serve as a precursor of aflatoxins. Remarkably, we found that VONE and VOROL had ring-opened structures. Their molecular masses were 386 and 388 Da, respectively, which were 18 Da greater than the molecular masses previously reported. These data demonstrated that two kinds of reactions are involved in the pathway from AVR to VHA in aflatoxin biosynthesis: (i) a reaction from (1′
S
,5′
S
)-AVR to HVN, catalyzed by the microsomal enzyme, and (ii) a new metabolic grid, catalyzed by a new cytosol monooxygenase enzyme and the previously reported VHA reductase enzyme, composed of HVN, VONE, VOAc, and VHA. A novel hydrogenation-dehydrogenation reaction between VONE and VOROL was also discovered.
A Colonization Factor (Production of Lateral Flagella) of Mesophilic
Aeromonas
spp. Is Inactive in
Aeromonas salmonicida
Strains
Authors: Merino Susana , Gavín Rosalina , Vilches Silvia , Shaw Jonathan G. , Tomás Juan M. 
Published: January 2003

ABSTRACT

The nine
laf
(lateral flagellum) genes of mesophilic aeromonads are in the
Aeromonas salmonicida
genome. The
laf
genes are functional, except for
lafA
(flagellin gene), which was inactivated by transposase 8 (IS
3
family). A pathogenic characteristic of mesophilic aeromonads (lateral flagella) is abolished in this specialized pathogen with a narrow host range.
Inactivation of
Salmonella enterica
Serovar Enteritidis by Ultrasonic Waves under Pressure at Different Water Activities
Authors: Álvarez I. , Mañas P. , Sala F. J. , Condón S. 
Published: January 2003

ABSTRACT

The inactivation of
Salmonella enterica
serovar Enteritidis by ultrasonic waves (20 kHz; 117-μm wavelength) under pressure (175 kPa) at nonlethal temperatures (manosonication [MS]) and lethal temperatures (manothermosonication [MTS]) in media of different water activities has been investigated. Heat decimal reduction time values increased 30 times when the water activity was decreased from nearly 1 to 0.96, but the MS resistance was increased only twofold. The inactivation of
Salmonella
serovar Enteritidis by ultrasound under pressure at low water activities was a phenomenon of the “all-or-nothing” type. A synergistic lethal effect was observed between heat and ultrasound in media with reduced water activity; the lower the water activity, the greater the synergistic effect. This work could be useful for improving sanitation and preservation treatments of foods, especially those which are sensitive to temperature and those in which components protect microorganisms to heat. It also contributes to our knowledge of microbial inactivation mechanisms by MS and MTS treatments.
Degradation and Transformability of DNA from Transgenic Leaves
Authors: Ceccherini MariaTeresa , Poté John , Kay Elisabeth , Van Van Tran , Maréchal Joëlle , Pietramellara Giacomo , Nannipieri Paolo , Vogel Timothy M. , Simonet Pascal 
Published: January 2003

ABSTRACT

The fate of transplastomic (chloroplast genome contains the transgene) tobacco plant DNA in planta was studied when the plant leaves were subjected to decay conditions simulating those encountered naturally, including grinding, incubation with cellulase or enzymes produced by
Erwinia chrysanthemi
, and attack by the plant pathogen
Ralstonia solanacearum
. Direct visualization of DNA on agarose gels, gene extraction yield (the number of amplifiable
aadA
sequences in extracted plant DNA), and the frequency that recipient bacteria can be transformed by plant DNA were used to evaluate the quality and quantity of plant DNA and the transgene. These measurements were used to monitor the physical and biological degradation of DNA inside decaying plant tissues. Our results indicate that while most of the DNA will be degraded inside plant cells, sufficient DNA persists to be released into the soil.
Molecular Characterization of Natural
Erwinia pyrifoliae
Strains Deficient in Hypersensitive Response
Authors: Jock Susanne , Kim Won-Sik , Barny Marie-Anne , Geider Klaus 
Published: January 2003

ABSTRACT

From necrotic tissue of a Nashi pear tree, 24
Erwinia pyrifoliae
strains, found to be identical by pulsed-field gel electrophoresis analysis, were isolated. Thirteen strains were not virulent on immature pears and did not induce a hypersensitive response in tobacco leaves. The defective gene
hrpL
was complemented with intact genes from
E. pyrifoliae
and
Erwinia amylovora
.
Comparison of UV Inactivation of Spores of Three
Encephalitozoon
Species with That of Spores of Two DNA Repair-Deficient
Bacillus subtilis
Biodosimetry Strains
Authors: Marshall Marilyn M. , Hayes Samuel , Moffett Jackie , Sterling Charles R. , Nicholson Wayne L. 
Published: January 2003

ABSTRACT

When exposed to 254-nm UV, spores of
Encephalitozoon intestinalis
,
Encephalitozoon cuniculi
, and
Encephalitozoon hellem
exhibited 3.2-log reductions in viability at UV fluences of 60, 140, and 190 J/m
2
, respectively, and demonstrated UV inactivation kinetics similar to those observed for endospores of DNA repair-defective mutant
Bacillus subtilis
strains used as biodosimetry surrogates. The results indicate that spores of
Encephalitozoon
spp. are readily inactivated at low UV fluences and that spores of UV-sensitive
B. subtilis
strains can be useful surrogates in evaluating UV reactor performance.
Effect of Stress on the Ability of a
phlA
-Based Quantitative Competitive PCR Assay To Monitor Biocontrol Strain
Pseudomonas fluorescens
CHA0
Authors: Rezzonico Fabio , Moënne-Loccoz Yvan , Défago Geneviève 
Published: January 2003

ABSTRACT

A quantitative competitive PCR (QC-PCR) assay targeting the
phlA
gene of
Pseudomonas fluorescens
CHA0 was developed and tested in vitro. Statistically significant, positive correlations were found between QC-PCR and both CFU and total cell number when studying cells in log or stationary phase. The correlations disappeared when considering stressed cells.
Characteristics of a Novel Type of Bovine
Cryptosporidium andersoni
Authors: Satoh Masaaki , Hikosaka Kenji , Sasaki Takako , Suyama Yoshihisa , Yanai Tokuma , Ohta Minoru , Nakai Yutaka 
Published: January 2003

ABSTRACT

We isolated oocysts that resemble
Cryptosporidium andersoni
from cattle grazing on a farm in Japan. The partial sequences of genes from the isolate were coincident with published sequences of genes of
C. andersoni
. Since the isolate was able to infect SCID mice, the isolate appears to be a novel type of
C. andersoni
.
Formyltetrahydrofolate Synthetase Sequences from Salt Marsh Plant Roots Reveal a Diversity of Acetogenic Bacteria and Other Bacterial Functional Groups
Authors: Leaphart A. B. , Friez M. J. , Lovell C. R. 
Published: January 2003

ABSTRACT

Sixty-two partial formyltetrahydrofolate synthetase (FTHFS) structural gene sequences were recovered from roots of salt marsh plants, including
Spartina alterniflora
,
Salicornia virginica
, and
Juncus roemerianus
. Only
S. alterniflora
roots yielded sequences grouping with FTHFS sequences from known acetogens. Most other FTHFS or FTHFS-like sequences grouped with those from sulfate-reducing bacteria. Several sequences that grouped with
Sphingomonas paucimobilis ligH
were also recovered.
Molecular Typing of
Aeromonas
Isolates in Natural Mineral Waters
Authors: Villari P. , Crispino M. , Montuori P. , Boccia S. 
Published: January 2003

ABSTRACT

A total of 103 isolates of
Aeromonas
spp. were obtained over a 3-year period from a natural mineral water and from surface streams located within the boundaries of the watershed of the natural mineral water wells and were typed by macrorestriction analysis of genomic DNA with
Xba
I and by pulsed-field gel electrophoresis. All
Aeromonas caviae
isolates from the natural mineral water belonged to the same clone, and an analogous clonal identity was found among
Aeromonas hydrophila
isolates. These two clones expressed no hemolytic or cytotoxic activities.
Aeromonas
isolates from surface waters showed high molecular heterogeneity and were not related to the clones found in the natural mineral water. The presence of aeromonads chronically found in the natural mineral water was a likely consequence of a localized development of a biofilm, with no exogenous contamination of the aquifer. Molecular fingerprinting of drinking water isolates is a useful tool in explaining possible reasons for bacterial occurrences.
A Food-Grade Approach for Functional Analysis and Modification of Native Plasmids in
Lactococcus lactis
Authors: Cotter Paul D. , Hill Colin , Ross R. Paul 
Published: January 2003

ABSTRACT

While plasmids from lactic acid bacteria possess many traits that are of industrial value, their exploitation is often frustrated by an inability to conduct food-grade engineering of native plasmids or to readily screen for their transfer. Here we describe a system that uses a RepA
+
temperature-sensitive helper plasmid and a RepA
−
cloning vector to overcome these problems while maintaining the food-grade status of the native plasmid. This strategy was used to precisely delete
ltnA1
alone, or in conjunction with
ltnA2
(encoding the structural proteins of the lantibiotic lacticin 3147), from the native 60.2-kb plasmid pMRC01 and to select for the transfer of pMRC01 between
Lactococcus lactis
strains.
Glutathione
S
-Transferase Isoenzymes from
Streptomyces griseus
Authors: Dhar Kajari , Dhar Alok , Rosazza John P. N. 
Published: January 2003

ABSTRACT

An inducible, cytosolic glutathione
S
-transferase (GST) was purified from
Streptomyces griseus
. GST isoenzymes with pI values of 6.8 and 7.9 used standard GST substrates including 1-chloro-2,4-dinitrobenzene. GST had subunit and native
M
r
s of 24 and 48, respectively, and the N-terminal sequence SMILXYWDIIRGLPAH.
Survival and Resuscitation of Ten Strains of
Campylobacter jejuni
and
Campylobacter coli
under Acid Conditions
Authors: Chaveerach P. , ter Huurne A. A. H. M. , Lipman L. J. A. , van Knapen F. 
Published: January 2003

ABSTRACT

The culturability of 10 strains of
Campylobacter jejuni
and
Campylobacter coli
was studied after the bacteria were exposed to acid conditions for various periods of time.
Campylobacter
cells could not survive 2 h under acid conditions (formic acid at pH 4). The 10
Campylobacter
strains could not be recovered, even when enrichment media were used. Viable cells, however, could be detected by a double-staining (5-cyano-2,3-ditolyl tetrazolium chloride [CTC]-4′,6′-diamidino-2-phenylindole [DAPI]) technique, demonstrating that the treated bacteria changed into a viable but nonculturable (VBNC) form; the number of VBNC forms decreased over time. Moreover, some VBNC forms of
Campylobacter
could be successfully resuscitated in specific-free-pathogen fertilized eggs via two routes, amniotic and yolk sac injecting.
Disruption of the
CAR1
Gene Encoding Arginase Enhances Freeze Tolerance of the Commercial Baker's Yeast
Saccharomyces cerevisiae
Authors: Shima Jun , Sakata-Tsuda Yuko , Suzuki Yasuo , Nakajima Ryouichi , Watanabe Hajime , Kawamoto Shinichi , Takano Hiroyuki 
Published: January 2003

ABSTRACT

The effect of intracellular charged amino acids on freeze tolerance in doughs was determined by constructing homozygous diploid arginase-deficient mutants of commercial baker's yeast. An arginase mutant accumulated higher levels of arginine and/or glutamate and showed increased leavening ability during the frozen-dough baking process, suggesting that disruption of the
CAR1
gene enhances freeze tolerance.
Hydrogenotrophic Methanogenesis by Moderately Acid-Tolerant Methanogens of a Methane-Emitting Acidic Peat
Authors: Horn Marcus A. , Matthies Carola , Küsel Kirsten , Schramm Andreas , Drake Harold L. 
Published: January 2003

ABSTRACT

The emission of methane (1.3 mmol of CH
4
m
−2
day
−1
), precursors of methanogenesis, and the methanogenic microorganisms of acidic bog peat (pH 4.4) from a moderately reduced forest site were investigated by in situ measurements, microcosm incubations, and cultivation methods, respectively. Bog peat produced CH
4
(0.4 to 1.7 μmol g [dry wt] of soil
−1
day
−1
) under anoxic conditions. At in situ pH, supplemental H
2
-CO
2
, ethanol, and 1-propanol all increased CH
4
production rates while formate, acetate, propionate, and butyrate inhibited the production of CH
4
; methanol had no effect. H
2
-dependent acetogenesis occurred in H
2
-CO
2
-supplemented bog peat only after extended incubation periods. Nonsupplemented bog peat initially produced small amounts of H
2
that were subsequently consumed. The accumulation of H
2
was stimulated by ethanol and 1-propanol or by inhibiting methanogenesis with bromoethanesulfonate, and the consumption of ethanol was inhibited by large amounts of H
2
; these results collectively indicated that ethanol- or 1-propanol-utilizing bacteria were trophically associated with H
2
-utilizing methanogens. A total of 10
9
anaerobes and 10
7
hydrogenotrophic methanogens per g (dry weight) of bog peat were enumerated by cultivation techniques. A stable methanogenic enrichment was obtained with an acidic, H
2
-CO
2
-supplemented, fatty acid-enriched defined medium. CH
4
production rates by the enrichment were similar at pH 4.5 and 6.5, and acetate inhibited methanogenesis at pH 4.5 but not at pH 6.5. A total of 27 different archaeal 16S rRNA gene sequences indicative of
Methanobacteriaceae
,
Methanomicrobiales
, and
Methanosarcinaceae
were retrieved from the highest CH
4
-positive serial dilutions of bog peat and methanogenic enrichments. A total of 10 bacterial 16S rRNA gene sequences were also retrieved from the same dilutions and enrichments and were indicative of bacteria that might be responsible for the production of H
2
that could be used by hydrogenotrophic methanogens. These results indicated that in this acidic bog peat, (i) H
2
is an important substrate for acid-tolerant methanogens, (ii) interspecies hydrogen transfer is involved in the degradation of organic carbon, (iii) the accumulation of protonated volatile fatty acids inhibits methanogenesis, and (iv) methanogenesis might be due to the activities of methanogens that are phylogenetic members of the
Methanobacteriaceae
,
Methanomicrobiales
, and
Methanosarcinaceae
.
Intergeneric Conjugation in
Streptomyces peucetius
and
Streptomyces
sp
.
Strain C5: Chromosomal Integration and Expression of Recombinant Plasmids Carrying the
chiC
Gene
Authors: Paranthaman Senthamaraikannan , Dharmalingam Kuppamuthu 
Published: January 2003

ABSTRACT

Intergeneric conjugal transfer of plasmid DNA from
Escherichia coli
to S
treptomyces
circumvents problems such as host-controlled restriction and instability of foreign DNA during the transformation of
Streptomyces
protoplasts. The anthracycline antibiotic-producing strains
Streptomyces peucetius
and
Streptomyces
sp. strain C5 were transformed using
E. coli
ET12567(pUZ8002) as a conjugal donor. When this donor species, carrying pSET152, was mated with
Streptomyces
strains, the resident plasmid was mobilized to the recipient and the transferred DNA was also integrated into the recipient chromosome. Analysis of the exconjugants showed stable integration of the plasmid at a single chromosomal site (
attB
) of the
Streptomyces
genome. The DNA sequence of the chromosomal integration site was determined and shown to be conserved. However, the core sequence, where the crossover presumably occurred in C5 and
S. peucetius
, is TTC. These results also showed that the φC31 integrative recombination is active and the phage
attP
site is functional in
S. peucetius
as well as in C5. The efficiency and specificity of φC31-mediated site-specific integration of the plasmid in the presence of a 3.7-kb homologous DNA sequence indicates that integrative recombination is preferred under these conditions. The integration of plasmid DNA did not affect antibiotic biosynthesis or biosynthesis of essential amino acids. Integration of a single copy of a mutant
chiC
into the wild-type
S. peucetius
chromosome led to the production of 30-fold more chitinase.
Enterococci as Indicators of Lake Michigan Recreational Water Quality: Comparison of Two Methodologies and Their Impacts on Public Health Regulatory Events
Authors: Kinzelman Julie , Ng Clement , Jackson Emma , Gradus Stephen , Bagley Robert 
Published: January 2003

ABSTRACT

The frequency of poor-water-quality advisories issued in Milwaukee and Racine, Wisconsin, in the absence of identifiable sources of contamination brought into question the reliability of the present indicator organism,
Escherichia coli
. Enteroccoci have been suggested as an alternative to
E. coli
for freshwater monitoring due to their direct correlation to swimmer-associated gastroenteritis. The purpose of this research was threefold: (i) to explore enterococci as an alternative to
E. coli
for monitoring freshwater Lake Michigan beaches, (ii) to evaluate the impact of the two indicators on regulatory decisions, and (iii) to compare membrane filtration m-enterococcus agar with indoxyl-β-
d
-glucoside to a chemical substrate technique (Enterolert) for the recovery of enterococci. Recreational water samples from Milwaukee (
n
= 305) and Racine (
n
= 153) were analyzed for the enumeration of
E. coli
and enterococci using IDEXX Colilert-18 and Enterolert. Correlation between the indicators was low (
R
2
= 0.60 and 0.69). Based on U.S. Environmental Protection Agency bacterial indicator threshold levels of risk for full body immersion, using enterococci would have resulted in 56 additional unsafe-recreational-water-quality advisories compared to the total from using
E. coli
and the substrate-based methods. A comparison of the two enterococcal methods (
n
= 124) yielded similar results (
R
2
= 0.62). This was further confounded by the frequent inability to verify enterococci from those wells producing fluorescence by the defined substrate test using conventional microbiological methods. These results suggest that further research is necessary regarding the use of defined substrate technology interchangeably with the U.S. Environmental Protection Agency-approved membrane filtration test for the detection of enterococci from fresh surface water.
Improved Understanding of the Bacterial Vaginal Microbiota of Women before and after Probiotic Instillation
Authors: Burton Jeremy P. , Cadieux Peter A. , Reid Gregor 
Published: January 2003

ABSTRACT

The vaginal bacterial microbiota of 19 premenopausal women was examined by PCR-denaturing gradient gel electrophoresis (DGGE) and sequencing of the V2-V3 region of the 16S rRNA gene. Ten of the women were studied further to investigate the effect and persistence of vaginally inserted capsules containing viable lactobacilli. PCR-DGGE indicated that most subjects had a microbiota represented by one to three dominant DNA fragments. Analysis of these fragments revealed that 79% of the women possessed sequences with high levels of similarity to
Lactobacillus
species sequences. Sequences homologous to
Lactobacillus iners
sequences were the most common and were detected in 42% of the women tested. Alteration of the vaginal microbiota could be detected by PCR-DGGE in several women after the instillation of lactobacilli. Additionally, randomly amplified polymorphic DNA analysis of lactobacilli isolated from selective media demonstrated that the exogenous strains could be detected for up to 21 days in some subjects. This study demonstrates that non-culture-based techniques, such as PCR-DGGE, are useful adjuncts for studies of the vaginal microbiota.
Comparison of Serological Assays for Detection of
Chlamydia trachomatis
Antibodies in Different Groups of Obstetrical and Gynecological Patients
Authors: Bax C. J. , Mutsaers J. A. E. M. , Jansen C. L. , Trimbos J. B. , Dörr P. J. , Oostvogel P. M. 
Published: January 2003

ABSTRACT

New serological enzyme immunoassays (EIAs) were compared with microimmunofluorescence (MIF) as a “gold standard” to detect
Chlamydia trachomatis
antibodies in different groups of obstetrical, gynecological, and subfertile patients. There were no significant differences in seroprevalence rates, except for the group of
C. trachomatis
-positive patients (
P
< 0.01). Test characteristics were calculated for Chlamydia-EIA (Biologische Analysensystem GmbH, Lich, Germany) and pELISA (Medac, Wedel, Germany). pELISA seems to be a good alternative to MIF. It has high specificity and is easier to perform.