bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Precipitation and Soil on Transport of Fecal Enterococci in Fractured Limestone Aquifers
Authors: Celico Fulvio , Varcamonti Mario , Guida Marco , Naclerio Gino 
Published: May 2004

ABSTRACT

Limestone aquifers provide the main drinking water resources of southern Italy. The groundwater is often contaminated by fecal bacteria because of the interaction between rocks having high permeability and microbial pollutants introduced into the environment by grazing and/or manure spreading. The microbial contamination of springwater in picnic areas located in high mountains can cause gastrointestinal illness. This study was carried out in order to analyze the interaction between
Enterococcus faecalis
and the soil of a limestone aquifer and to verify the influence of this interaction on the time dependence of groundwater contamination.
E. faecalis
was chosen because, in the study area involved, it represents a better indicator than
Escherichia coli
. The research was carried out through field (springwater monitoring) and laboratory experiments (column tests with intact soil blocks). The transport of bacterial cells through soil samples was analyzed by simulating an infiltration event that was monitored in the study area. Comparison of laboratory results with data acquired in the field showed that discontinuous precipitation caused an intermittent migration of microorganisms through the soil and produced, together with dispersion in the fractured medium (unsaturated and saturated zones), an articulated breakthrough at the spring. The short distances of bacterial transport in the study area produced a significant daily variability of bacterial contamination at the field scale.
Use of Aqueous Silver To Enhance Inactivation of Coliphage MS-2 by UV Disinfection
Authors: Butkus Michael A. , Labare Michael P. , Starke Jeffrey A. , Moon King , Talbot Mark 
Published: May 2004

ABSTRACTA synergistic effect between silver and UV radiation has been observed that can appreciably enhance the effectiveness of UV radiation for inactivation of viruses. At a fluence of ca. 40 mJ/cm2, the synergistic effect between silver and UV was observed at silver concentrations as low as 10 μg/liter (P< 0.0615). At the same fluence, an MS-2 inactivation of ca. 3.5 logs (99.97%) was achieved at a silver concentration of 0.1 mg/liter, a significant improvement (P< 0.0001) over the ca. 1.8-log (98.42%) inactivation of MS-2 at ca. 40 mJ/cm2in the absence of silver. Modified Chick-Watson kinetics were used to model the synergistic effect of silver and UV radiation. For an MS-2 inactivation of 4 logs (99.99%), the coefficient of dilution (n) was determined to be 0.31, which suggests that changes in fluence have a greater influence on inactivation than does a proportionate change in silver concentration.
Nitrite Elimination and Hydrolytic Ring Cleavage in 2,4,6-Trinitrophenol (Picric Acid) Degradation
Authors: Hofmann Klaus W. , Knackmuss Hans-Joachim , Heiss Gesche 
Published: May 2004

ABSTRACT

Two hydrogenation reactions in the initial steps of degradation of 2,4,6-trinitrophenol produce the dihydride Meisenheimer complex of 2,4,6-trinitrophenol. The
npdH
gene (contained in the
npd
gene cluster of the 2,4,6-trinitrophenol-degrading strain
Rhodococcus opacus
HL PM-1) was shown here to encode a tautomerase, catalyzing a proton shift between the
aci
-nitro and the nitro forms of the dihydride Meisenheimer complex of 2,4,6-trinitrophenol. An enzyme (which eliminated nitrite from the
aci
-nitro form but not the nitro form of the dihydride complex of 2,4,6-trinitrophenol) was purified from the 2,4,6-trinitrophenol-degrading strain
Nocardioides simplex
FJ2-1A. The product of nitrite release was the hydride Meisenheimer complex of 2,4-dinitrophenol, which was hydrogenated to the dihydride Meisenheimer complex of 2,4-dinitrophenol by the hydride transferase I and the NADPH-dependent F
420
reductase from strain HL PM-1. At pH 7.5, the dihydride complex of 2,4-dinitrophenol is protonated to 2,4-dinitrocyclohexanone. A hydrolase was purified from strain FJ2-1A and shown to cleave 2,4-dinitrocyclohexanone hydrolytically to 4,6-dinitrohexanoate.
Heterologous Expression of Lactose- and Galactose-Utilizing Pathways from Lactic Acid Bacteria in
Corynebacterium glutamicum
for Production of Lysine in Whey
Authors: Barrett Eoin , Stanton Catherine , Zelder Oskar , Fitzgerald Gerald , Ross R. Paul 
Published: May 2004

ABSTRACT

The genetic determinants for lactose utilization from
Lactobacillus delbrueckii
subsp.
bulgaricus
ATCC 11842 and galactose utilization from
Lactococcus lactis
subsp.
cremoris
MG 1363 were heterologously expressed in the lysine-overproducing strain
Corynebacterium glutamicum
ATCC 21253. The
C. glutamicum
strains expressing the lactose permease and β-galactosidase genes of
L. delbrueckii
subsp.
bulgaricus
exhibited β-galactosidase activity in excess of 1,000 Miller units/ml of cells and were able to grow in medium in which lactose was the sole carbon source. Similarly,
C. glutamicum
strains containing the lactococcal aldose-1-epimerase, galactokinase, UDP-glucose-1-P-uridylyltransferase, and UDP-galactose-4-epimerase genes in association with the lactose permease and β-galactosidase genes exhibited β-galactosidase levels in excess of 730 Miller units/ml of cells and were able to grow in medium in which galactose was the sole carbon source. When grown in whey-based medium, the engineered
C. glutamicum
strain produced lysine at concentrations of up to 2 mg/ml, which represented a 10-fold increase over the results obtained with the lactose- and galactose-negative control,
C. glutamicum
21253. Despite their increased catabolic flexibility, however, the modified corynebacteria exhibited slower growth rates and plasmid instability.
Seasonal Changes in an Alpine Soil Bacterial Community in the Colorado Rocky Mountains
Authors: Lipson David A. , Schmidt Steven K. 
Published: May 2004

ABSTRACTThe period when the snowpack melts in late spring is a dynamic time for alpine ecosystems. The large winter microbial community begins to turn over rapidly, releasing nutrients to plants. Past studies have shown that the soil microbial community in alpine dry meadows of the Colorado Rocky Mountains changes in biomass, function, broad-level structure, and fungal diversity between winter and early summer. However, little specific information exists on the diversity of the alpine bacterial community or how it changes during this ecologically important period. We constructed clone libraries of 16S ribosomal DNA from alpine soil collected in winter, spring, and summer. We also cultivated bacteria from the alpine soil and measured the seasonal abundance of selected cultured isolates in hybridization experiments. The uncultured bacterial communities changed between seasons in diversity and abundance within taxa. TheAcidobacteriumdivision was most abundant in the spring. The winter community had the highest proportion ofActinobacteriaand members of theCytophaga/Flexibacter/Bacteroides(CFB) division. The summer community had the highest proportion of theVerrucomicrobiumdivision and of β-Proteobacteria. As a whole,α -Proteobacteriawere equally abundant in all seasons, although seasonal changes may have occurred within this group. A number of sequences from currently uncultivated divisions were found, including two novel candidate divisions. The cultured isolates belonged to the α-, β-, and γ-Proteobacteria, theActinobacteria, and the CFB groups. The only uncultured sequences that were closely related to the isolates were from winter and spring libraries. Hybridization experiments showed that actinobacterial and β-proteobacterial isolates were most abundant during winter, while the α- andγ -proteobacterial isolates tested did not vary significantly. While the cultures and clone libraries produced generally distinct groups of organisms, the two approaches gave consistent accounts of seasonal changes in microbial diversity.
Assembly of G Protein-Coupled Receptors onto Nanosized Bacterial Magnetic Particles Using Mms16 as an Anchor Molecule
Authors: Yoshino Tomoko , Takahashi Masayoshi , Takeyama Haruko , Okamura Yoshiko , Kato Fukuichi , Matsunaga Tadashi 
Published: May 2004

ABSTRACT

G protein-coupled receptors (GPCRs) play a central role in a wide range of biological processes and are prime targets for drug discovery. GPCRs have large hydrophobic domains, and therefore purification of GPCRs from cells is frequently time-consuming and typically results in loss of native conformation. In this work, GPCRs have been successfully assembled into the lipid membrane of nanosized bacterial magnetic particles (BMPs) produced by the magnetic bacterium
Magnetospirillum magneticum
AMB-1. A BMP-specific protein, Mms16, was used as an anchor molecule, and localization of heterologous Mms16 on BMPs was confirmed by luciferase fusion studies. Stable luminescence was obtained from BMPs bearing Mms16 fused with luciferase at the C-terminal region. D1 dopamine receptor (D1R), a GPCR, was also efficiently assembled onto BMPs by using Mms16 as an anchor molecule. D1R-BMP complexes were simply extracted by magnetic separation from ruptured AMB-1 transformants. After washing, the complexes were ready to use for analysis. This system conveniently refines the native conformation of GPCRs without the need for detergent solubilization, purification, and reconstitution after cell disruption.
New Method of Denitrification Analysis of
Bradyrhizobium
Field Isolates by Gas Chromatographic Determination of
15
N-Labeled N
2
Authors: Sameshima-Saito Reiko , Chiba Kaori , Minamisawa Kiwamu 
Published: May 2004

ABSTRACT

To evaluate the denitrification abilities of many
Bradyrhizobium
field isolates, we developed a new
15
N-labeled N
2
detection methodology, which is free from interference from atmospheric N
2
contamination.
30
N
2
(
15
N
15
N) and
29
N
2
(
15
N
14
N) were detected as an apparent peak by a gas chromatograph equipped with a thermal conductivity detector with N
2
gas having natural abundance of
15
N (0.366 atom%) as a carrier gas. The detection limit was 0.04%
30
N
2
, and the linearity extended at least to 40%
30
N
2
. When
Bradyrhizobium japonicum
USDA110 was grown in cultures anaerobically with
15
NO
3
−
, denitrification product (
30
N
2
) was detected stoichiometrically. A total of 65 isolates of soybean bradyrhizobia from two field sites in Japan were assayed by this method. The denitrification abilities were partly correlated with filed sites,
Bradyrhizobium
species, and the
hup
genotype.
Metabolic Engineering of a Phosphoketolase Pathway for Pentose Catabolism in
Saccharomyces cerevisiae
Authors: Sonderegger Marco , Schümperli Michael , Sauer Uwe 
Published: May 2004

ABSTRACT

Low ethanol yields on xylose hamper economically viable ethanol production from hemicellulose-rich plant material with
Saccharomyces cerevisiae
. A major obstacle is the limited capacity of yeast for anaerobic reoxidation of NADH. Net reoxidation of NADH could potentially be achieved by channeling carbon fluxes through a recombinant phosphoketolase pathway. By heterologous expression of phosphotransacetylase and acetaldehyde dehydrogenase in combination with the native phosphoketolase, we installed a functional phosphoketolase pathway in the xylose-fermenting
Saccharomyces cerevisiae
strain TMB3001c. Consequently the ethanol yield was increased by 25% because less of the by-product xylitol was formed. The flux through the recombinant phosphoketolase pathway was about 30% of the optimum flux that would be required to completely eliminate xylitol and glycerol accumulation. Further overexpression of phosphoketolase, however, increased acetate accumulation and reduced the fermentation rate. By combining the phosphoketolase pathway with the
ald6
mutation, which reduced acetate formation, a strain with an ethanol yield 20% higher and a xylose fermentation rate 40% higher than those of its parent was engineered.
Homofermentative Lactate Production Cannot Sustain Anaerobic Growth of Engineered
Saccharomyces cerevisiae
: Possible Consequence of Energy-Dependent Lactate Export
Authors: van Maris Antonius J. A. , Winkler Aaron A. , Porro Danilo , van Dijken Johannes P. , Pronk Jack T. 
Published: May 2004

ABSTRACT

Due to a growing market for the biodegradable and renewable polymer polylactic acid, the world demand for lactic acid is rapidly increasing. The tolerance of yeasts to low pH can benefit the process economy of lactic acid production by minimizing the need for neutralizing agents.
Saccharomyces cerevisiae
(CEN.PK background) was engineered to a homofermentative lactate-producing yeast via deletion of the three genes encoding pyruvate decarboxylase and the introduction of a heterologous lactate dehydrogenase (EC 1.1.1.27). Like all pyruvate decarboxylase-negative
S. cerevisiae
strains, the engineered strain required small amounts of acetate for the synthesis of cytosolic acetyl-coenzyme A. Exposure of aerobic glucose-limited chemostat cultures to excess glucose resulted in the immediate appearance of lactate as the major fermentation product. Ethanol formation was absent. However, the engineered strain could not grow anaerobically, and lactate production was strongly stimulated by oxygen. In addition, under all conditions examined, lactate production by the engineered strain was slower than alcoholic fermentation by the wild type. Despite the equivalence of alcoholic fermentation and lactate fermentation with respect to redox balance and ATP generation, studies on oxygen-limited chemostat cultures showed that lactate production does not contribute to the ATP economy of the engineered yeast. This absence of net ATP production is probably due to a metabolic energy requirement (directly or indirectly in the form of ATP) for lactate export.
Structural and Functional Differences in Two Cyclic Bacteriocins with the Same Sequences Produced by Lactobacilli
Authors: Kawai Yasushi , Ishii Yasuyuki , Arakawa Kensuke , Uemura Koichiro , Saitoh Boku , Nishimura Junko , Kitazawa Haruki , Yamazaki Yukiko , Tateno Yoshio , Itoh Takatoshi , Saito Tadao 
Published: May 2004

ABSTRACT

Lactobacillus gasseri
LA39 and
L. reuteri
LA6 isolated from feces of the same human infant were found to produce similar cyclic bacteriocins (named gassericin A and reutericin 6, respectively) that cannot be distinguished by molecular weights or primary amino acid sequences. However, reutericin 6 has a narrower spectrum than gassericin A. In this study, gassericin A inhibited the growth of
L. reuteri
LA6, but reutericin 6 did not inhibit the growth of
L. gasseri
LA39. Both bacteriocins caused potassium ion efflux from indicator cells and liposomes, but the amounts of efflux and patterns of action were different. Although circular dichroism spectra of purified bacteriocins revealed that both antibacterial peptides are composed mainly of α-helices, the spectra of the bacteriocins did not coincide. The results of
d
- and
l
-amino acid composition analysis showed that two residues and one residue of
d
-Ala were detected among 18 Ala residues of gassericin A and reutericin 6, respectively. These findings suggest that the different
d
-alanine contents of the bacteriocins may cause the differences in modes of action, amounts of potassium ion efflux, and secondary structures. This is the first report that characteristics of native bacteriocins produced by wild lactobacillus strains having the same structural genes are influenced by a difference in
d
-amino acid contents in the molecules.
Molecular and Physiological Analysis of the Role of Osmolyte Transporters BetL, Gbu, and OpuC in Growth of
Listeria monocytogenes
at Low Temperatures
Authors: Wemekamp-Kamphuis Henrike H. , Sleator Roy D. , Wouters Jeroen A. , Hill Colin , Abee Tjakko 
Published: May 2004

ABSTRACT

Listeria monocytogenes
is a ubiquitous food-borne pathogen found widely distributed in nature as well as an undesirable contaminant in a variety of fresh and processed foods. This ubiquity can be at least partly explained by the ability of the organism to grow at high osmolarity and reduced temperatures, a consequence of its ability to accumulate osmo- and cryoprotective compounds termed osmolytes. Single and multiple deletions of the known osmolyte transporters BetL, Gbu, and OpuC significantly reduce growth at low temperatures. During growth in brain heart infusion broth at 7°C, Gbu and OpuC had a more pronounced role in cryoprotection than did BetL. However, upon the addition of betaine to defined medium, the hierarchy of transporter importance shifted to Gbu > BetL > OpuC. Upon the addition of carnitine, only OpuC appeared to play a role in cryoprotection. Measurements of the accumulated osmolytes showed that betaine is preferred over carnitine, while in the absence of a functional Gbu, carnitine was accumulated to higher levels than betaine was at 7°C. Transcriptional analysis of the genes encoding BetL, Gbu, and OpuC revealed that each transporter is induced to different degrees upon cold shock of
L. monocytogenes
LO28. Additionally, despite being transcriptionally up-regulated upon cold shock, a putative fourth osmolyte transporter, OpuB (identified by bioinformatic analysis and encoded by
lmo1421
and
lmo1422
), showed no significant contribution to listerial chill tolerance. Growth of the quadruple mutant LO28ΔBCGB (Δ
betL
Δ
opuC
Δ
gbu
Δ
opuB
) was comparable to the that of the triple mutant LO28ΔBCGsoe (Δ
betL
Δ
opuC
Δ
gbu
) at low temperatures. Here, we conclude that betaine and carnitine transport upon low-temperature exposure is mediated via three osmolyte transporters, BetL, Gbu, and OpuC.
Relative Neurotoxin Gene Expression inClostridium botulinumType B, Determined Using Quantitative Reverse Transcription-PCR
Authors: Lövenklev Maria , Holst Elisabet , Borch Elisabeth , Rådström Peter 
Published: May 2004

ABSTRACTA quantitative reverse transcription-PCR (qRT-PCR) method was developed to monitor the relative expression of the type B botulinum neurotoxin (BoNT/B) gene (cntB) inClostridium botulinum. The levels ofcntBmRNA in five type B strains were accurately monitored by using primers specific forcntBand for the reference gene encoding the 16S rRNA. The patterns and relative expression ofcntBwere different in the different strains. Except for one of the strains investigated, an increase incntBexpression was observed when the bacteria entered the early stationary growth phase. In the proteolytic strainC. botulinumATCC 7949, the level ofcntBmRNA was four- to fivefold higher than the corresponding levels in the other strains. This was confirmed when we quantified the production of extracellular BoNT/B by an enzyme-linked immunosorbent assay and measured the toxicity of BoNT/B by a mouse bioassay. When the effect of exposure to air oncntBexpression was investigated, no decline in the relative expression was observed in spite of an 83% reduction in the viable count based on the initial cell number. Instead, the level ofcntBmRNA remained the same. When there was an increase in the sodium nitrite concentration, the bacteria needed a longer adjustment time in the medium before exponential growth occurred. In addition, there was a reduction in the expression ofcntBcompared to the expression of the 16S rRNA gene at higher sodium nitrite concentrations. This was most obvious in the late exponential growth phase, but at the highest sodium nitrite concentration investigated, 45 ppm, a one- to threefold decline in thecntBmRNA level was observed in all growth phases.
Quantitative Interaction Effects of Carbon Dioxide, Sodium Chloride, and Sodium Nitrite on Neurotoxin Gene Expression in Nonproteolytic
Clostridium botulinum
Type B
Authors: Lövenklev Maria , Artin Ingrid , Hagberg Oskar , Borch Elisabeth , Holst Elisabet , Rådström Peter 
Published: May 2004

ABSTRACT

The effects of carbon dioxide, sodium chloride, and sodium nitrite on type B botulinum neurotoxin (BoNT/B) gene (
cntB
) expression in nonproteolytic
Clostridium botulinum
were investigated in a tryptone-peptone-yeast extract (TPY) medium. Various concentrations of these selected food preservatives were studied by using a complete factorial design in order to quantitatively study interaction effects, as well as main effects, on the following responses: lag phase duration (LPD), growth rate, relative
cntB
expression, and extracellular BoNT/B production. Multiple linear regression was used to set up six statistical models to quantify and predict these responses. All combinations of NaCl and NaNO
2
in the growth medium resulted in a prolonged lag phase duration and in a reduction in the specific growth rate. In contrast, the relative BoNT/B gene expression was unchanged, as determined by the
cntB
-specific quantitative reverse transcription-PCR method. This was confirmed when we measured the extracellular BoNT/B concentration by an enzyme-linked immunosorbent assay. CO
2
was found to have a major effect on gene expression when the
cntB
mRNA levels were monitored in the mid-exponential, late exponential, and late stationary growth phases. The expression of
cntB
relative to the expression of the 16S rRNA gene was stimulated by an elevated CO
2
concentration; the
cntB
mRNA level was fivefold greater in a 70% CO
2
atmosphere than in a 10% CO
2
atmosphere. These findings were also confirmed when we analyzed the extracellular BoNT/B concentration; we found that the concentrations were 27 ng · ml
−1
· unit of optical density
−1
in the 10% CO
2
atmosphere and 126 ng · ml
−1
· unit of optical density
−1
in the 70% CO
2
atmosphere.
Stable Isotope Fractionation Caused by Glycyl Radical Enzymes during Bacterial Degradation of Aromatic Compounds
Authors: Morasch Barbara , Richnow Hans H. , Vieth Andrea , Schink Bernhard , Meckenstock Rainer U. 
Published: May 2004

ABSTRACT

Stable isotope fractionation was studied during the degradation of
m
-xylene,
o
-xylene,
m
-cresol, and
p
-cresol with two pure cultures of sulfate-reducing bacteria. Degradation of all four compounds is initiated by a fumarate addition reaction by a glycyl radical enzyme, analogous to the well-studied benzylsuccinate synthase reaction in toluene degradation. The extent of stable carbon isotope fractionation caused by these radical-type reactions was between enrichment factors (ε) of −1.5 and −3.9

, which is in the same order of magnitude as data provided before for anaerobic toluene degradation. Based on our results, an analysis of isotope fractionation should be applicable for the evaluation of in situ bioremediation of all contaminants degraded by glycyl radical enzyme mechanisms that are smaller than 14 carbon atoms. In order to compare carbon isotope fractionations upon the degradation of various substrates whose numbers of carbon atoms differ, intrinsic ε (ε
intrinsic
) were calculated. A comparison of ε
intrinsic
at the single carbon atoms of the molecule where the benzylsuccinate synthase reaction took place with compound-specific ε elucidated that both varied on average to the same extent. Despite variations during the degradation of different substrates, the range of ε found for glycyl radical reactions was reasonably narrow to propose that rough estimates of biodegradation in situ might be given by using an average ε if no fractionation factor is available for single compounds.