bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polyphasic Study of the Spatial Distribution of Microorganisms in Mexican Pozol, a Fermented Maize Dough, Demonstrates the Need for Cultivation-Independent Methods To Investigate Traditional Fermentations
Authors: Ampe Frédéric , ben Omar Nabil , Moizan Claire , Wacher Carmen , Guyot Jean-Pierre 
Published: December 2019

ABSTRACT

The distribution of microorganisms in pozol balls, a fermented maize dough, was investigated by a polyphasic approach in which we used both culture-dependent and culture-independent methods, including microbial enumeration, fermentation product analysis, quantification of microbial taxa with 16S rRNA-targeted oligonucleotide probes, determination of microbial fingerprints by denaturing gradient gel electrophoresis (DGGE), and 16S ribosomal DNA gene sequencing. Our results demonstrate that DGGE fingerprinting and rRNA quantification should allow workers to precisely and rapidly characterize the microbial assemblage in a spontaneous lactic acid fermented food. Lactic acid bacteria (LAB) accounted for 90 to 97% of the total active microflora; no streptococci were isolated, although members of the genus
Streptococcus
accounted for 25 to 50% of the microflora.
Lactobacillus plantarum
and
Lactobacillus fermentum
, together with members of the genera
Leuconostoc
and
Weissella
, were the other dominant organisms. The overall activity was more important at the periphery of a ball, where eucaryotes, enterobacteria, and bacterial exopolysacharide producers developed. Our results also showed that the metabolism of heterofermentative LAB was influenced in situ by the distribution of the LAB in the pozol ball, whereas homolactic fermentation was controlled primarily by sugar limitation. We propose that starch is first degraded by amylases from LAB and that the resulting sugars, together with the lactate produced, allow a secondary flora to develop in the presence of oxygen. Our results strongly suggest that cultivation-independent methods should be used to study traditional fermented foods.
Escherichia coli
Resistance to Chlorine and Glutathione Synthesis in Response to Oxygenation and Starvation
Authors: Saby Sébastien , Leroy Pierre , Block Jean-Claude 
Published: December 2019

ABSTRACT

Reduced glutathione (GSH) levels and resistance to chlorine were measured for two isogenic
Escherichia coli
strains stressed by oxygenation and/or starvation. The
E. coli
mutant deficient in GSH was not more sensitive to the oxidant than its parent strain when the bacteria were cultured with a low oxygenation rate. Starvation or oxygenation increased the resistance of the parent strain to chlorine, while the resistance of the deficient strain remained unchanged.
Comparative Survival of Free Shiga Toxin 2-Encoding Phages and
Escherichia coli
Strains outside the Gut
Authors: Muniesa Maite , Lucena Francisco , Jofre Juan 
Published: December 2019

ABSTRACT

The behavior outside the gut of seeded
Escherichia coli
O157:H7, naturally occurring
E. coli
, somatic coliphages, bacteriophages infecting O157:H7, and Shiga toxin 2 (Stx2)-encoding bacteriophages was studied to determine whether the last persist in the environment more successfully than their host bacteria. The ratios between the numbers of
E. coli
and those of the different bacteriophages were clearly lower in river water than in sewage of the area, whereas the ratios between the numbers of the different phages were similar. In addition, the numbers of bacteria decreased between 2 and 3 log units in in situ survival experiments performed in river water, whereas the numbers of phages decreased between 1 and 2 log units. Chlorination and pasteurization treatments that reduced by approximately 4 log units the numbers of bacteria reduced by less than 1 log unit the numbers of bacteriophages. Thus, it can be concluded that Stx2-encoding phages persist longer than their host bacteria in the water environment and are more resistant than their host bacteria to chlorination and heat treatment.
Molecular Detection of Norwalk-Like Caliciviruses in Sewage
Authors: Lodder W. J. , Vinjé J. , van de Heide R. , de Roda Husman A. M. , Leenen E. J. T. M. , Koopmans M. P. G. 
Published: December 2019

ABSTRACT

In this study, Norwalk-like virus (NLV) RNA was detected by reverse transcriptase PCR (RT-PCR) in sewage water concentrates. Sequence analysis of the RT-PCR products revealed identical sequences in stools of patients and related sewage samples. In 6 of 11 outbreak-unrelated follow-up samples, multiple NLV genotypes were present. Levels as high as 10
7
RNA-containing particles per liter were found. These data show that high loads of NLVs may be present in sewage and warrant further studies addressing the efficacy of NLV removal by sewage water treatment processes.
Characterization of a Bacteriocin-Like Substance Produced by a Vaginal
Lactobacillus salivarius
Strain
Authors: Ocaña Virginia S. , Pesce de Ruiz Holgado Aída A. , Nader-Macías María Elena 
Published: December 2019

ABSTRACT

A novel bacteriocin-like substance produced by vaginal
Lactobacillus salivarius
subsp.
salivarius
CRL 1328 with activity against
Enterococcus faecalis
,
Enterococcus faecium
, and
Neisseria gonorrhoeae
was characterized. The highest level of production of this heat-resistant peptide or protein occurred during the late exponential phase. Its mode of action was shown to be bactericidal.
L. salivarius
subsp.
salivarius
CRL 1328 could be used for the design of a probiotic to prevent urogenital infections.
Toxicity, Binding, and Permeability Analyses of Four
Bacillus thuringiensis
Cry1 δ-Endotoxins Using Brush Border Membrane Vesicles of
Spodoptera exigua
and
Spodoptera frugiperda
Authors: Luo Ke , Banks David , Adang Michael J. 
Published: December 2019

ABSTRACT

The binding and pore formation properties of four
Bacillus thuringiensis
Cry1 toxins were analyzed by using brush border membrane vesicles from
Spodoptera exigua
and
Spodoptera frugiperda
, and the results were compared to the results of toxicity bioassays. Cry1Fa was highly toxic and Cry1Ac was nontoxic to
S. exigua
and
S. frugiperda
larvae, while Cry1Ca was highly toxic to
S. exigua
and weakly toxic to
S. frugiperda
. In contrast, Cry1Bb was active against
S. frugiperda
but only marginally active against
S. exigua
. Bioassays performed with iodinated Cry1Bb, Cry1Fa, and Cry1Ca showed that the effects of iodination on toxin activity were different. The toxicities of I-labeled Cry1Bb and Cry1Fa against
Spodoptera
species were significantly less than the toxicities of the unlabeled toxins, while Cry1Ca retained its insecticidal activity when it was labeled with
125
I. Binding assays showed that iodination prevented Cry1Fa from binding to
Spodoptera
brush border membrane vesicles.
125
I-labeled Cry1Ac, Cry1Bb, and Cry1Ca bound with high-affinities to brush border membrane vesicles from
S. exigua
and
S. frugiperda
. Competition binding experiments performed with heterologous toxins revealed two major binding sites. Cry1Ac and Cry1Fa have a common binding site, and Cry1Bb, Cry1C, and Cry1Fa have a second common binding site. No obvious relationship between dissociation of bound toxins from brush border membrane vesicles and toxicity was detected. Cry1 toxins were also tested for the ability to alter the permeability of membrane vesicles, as measured by a light scattering assay. Cry1 proteins toxic to
Spodoptera
larvae permeabilized brush border membrane vesicles, but the extent of permeabilization did not necessarily correlate with in vivo toxicity.
Anaerobic Benzene Biodegradation Linked to Nitrate Reduction
Authors: Burland Siobhan M. , Edwards Elizabeth A. 
Published: December 2019

ABSTRACT

Benzene oxidation to carbon dioxide linked to nitrate reduction was observed in enrichment cultures developed from soil and groundwater microcosms. Benzene biodegradation occurred concurrently with nitrate reduction at a constant ratio of 10 mol of nitrate consumed per mol of benzene degraded. Benzene biodegradation linked to nitrate reduction was associated with cell growth; however, the yield, 8.8 g (dry weight) of cells per mol of benzene, was less than 15% of the predicted yield for benzene biodegradation linked to nitrate reduction. In experiments performed with [
14
C]benzene, approximately 92 to 95% of the label was recovered in
14
CO
2
, while the remaining 5 to 8% was incorporated into the nonvolatile fraction (presumably biomass), which is consistent with the low measured yield. In benzene-degrading cultures, nitrite accumulated stoichiometrically as nitrate was reduced and then was slowly reduced to nitrogen gas. When nitrate was depleted and only nitrite remained, the rate of benzene degradation decreased to almost zero. Based on electron balances, benzene biodegradation appears to be coupled more tightly to nitrate reduction to nitrite than to further reduction of nitrite to nitrogen gas.
High-Affinity Transport of Choline-
O
-Sulfate and Its Use as a Compatible Solute in
Bacillus subtilis
Authors: Nau-Wagner Gabriele , Boch Jens , Le Good J. Ann , Bremer Erhard 
Published: December 2019

ABSTRACT

We report here that the naturally occurring choline ester choline-
O
-sulfate serves as an effective compatible solute for
Bacillus subtilis
, and we have identified a high-affinity ATP-binding cassette (ABC) transport system responsible for its uptake. The osmoprotective effect of this trimethylammonium compound closely matches that of the potent and widely employed osmoprotectant glycine betaine. Growth experiments with a set of
B. subtilis
strains carrying defined mutations in the glycine betaine uptake systems OpuA, OpuC, and OpuD and in the high-affinity choline transporter OpuB revealed that choline-
O
-sulfate was specifically acquired from the environment via OpuC. Competition experiments demonstrated that choline-
O
-sulfate functioned as an effective competitive inhibitor for OpuC-mediated glycine betaine uptake, with a

K
i

of approximately 4 μM. Uptake studies with [1,2-
dimethyl
-
14
C]choline-
O
-sulfate showed that its transport was stimulated by high osmolality, and kinetic analysis revealed that OpuC has high affinity for choline-
O
-sulfate, with a

K
m

value of 4 ± 1 μM and a maximum rate of transport (
V
max
) of 54 ± 3 nmol/min · mg of protein in cells grown in minimal medium with 0.4 M NaCl. Growth studies utilizing a
B. subtilis
mutant defective in the choline to glycine betaine synthesis pathway and natural abundance
13
C nuclear magnetic resonance spectroscopy of whole-cell extracts from the wild-type strain demonstrated that choline-
O
-sulfate was accumulated in the cytoplasm and was not hydrolyzed to choline by
B. subtilis
. In contrast, the osmoprotective effect of acetylcholine for
B. subtilis
is dependent on its biotransformation into glycine betaine. Choline-
O
-sulfate was not used as the sole carbon, nitrogen, or sulfur source, and our findings thus characterize this choline ester as an effective compatible solute and metabolically inert stress compound for
B. subtilis
. OpuC mediates the efficient transport not only of glycine betaine and choline-
O
-sulfate but also of carnitine, crotonobetaine, and γ-butyrobetaine (R. Kappes and E. Bremer, Microbiology 144:83–90, 1998). Thus, our data underscore its crucial role in the acquisition of a variety of osmoprotectants from the environment by
B. subtilis
.
Inactivation of Toluene 2-Monooxygenase in
Burkholderia cepacia
G4 by Alkynes
Authors: Yeager Chris M. , Bottomley Peter J. , Arp Daniel J. , Hyman Michael R. 
Published: December 2019

ABSTRACT

High concentrations of acetylene (10 to 50% [vol/vol] gas phase) were required to inhibit the growth of
Burkholderia cepacia
G4 on toluene, while 1% (vol/vol) (gas phase) propyne or 1-butyne completely inhibited growth. Low concentrations of longer-chain alkynes (C
5
to C
10
) were also effective inhibitors of toluene-dependent growth, and 2- and 3-alkynes were more potent inhibitors than their 1-alkyne counterparts. Exposure of toluene-grown
B. cepacia
G4 to alkynes resulted in the irreversible loss of toluene- and
o
-cresol-dependent O
2
uptake activities, while acetate- and 3-methylcatechol-dependent O
2
uptake activities were unaffected. Toluene-dependent O
2
uptake decreased upon the addition of 1-butyne in a concentration- and time-dependent manner. The loss of activity followed first-order kinetics, with apparent rate constants ranging from 0.25 min
−1
to 2.45 min
−1
. Increasing concentrations of toluene afforded protection from the inhibitory effects of 1-butyne. Furthermore, oxygen, supplied as H
2
O
2
, was required for inhibition by 1-butyne. These results suggest that alkynes are specific, mechanism-based inactivators of toluene 2-monooxygenase in
B. cepacia
G4, although the simplest alkyne, acetylene, was relatively ineffective compared to longer alkynes. Alkene analogs of acetylene and propyne—ethylene and propylene—were not inactivators of toluene 2-monooxygenase activity in
B. cepacia
G4 but were oxidized to their respective epoxides, with apparent

K
s

and
V
max
values of 39.7 μM and 112.3 nmol min
−1
mg of protein
−1
for ethylene and 32.3 μM and 89.2 nmol min
−1
mg of protein
−1
for propylene.
A Mutation That Improves Soluble Recombinant Hemoglobin Accumulation in
Escherichia coli
in Heme Excess
Authors: Weickert Michael J. , Pagratis Maria , Glascock Christopher B. , Blackmore Richard 
Published: December 2019

ABSTRACT

High-level expression of soluble recombinant human hemoglobin (rHb) in
Escherichia coli
was obtained with several hemoglobin variants. Under identical conditions, two rHbs containing the Presbyterian mutation (Asn-108→Lys) in β-globin accumulated to approximately twofold less soluble globin than rHbs containing the corresponding wild-type β-globin subunit accumulated. The β-globin Providence
(asp)
mutation (Lys-82→Asp) significantly improved soluble rHb accumulation compared to the wild-type β-globin subunit and restored soluble accumulation of rHbs containing the Presbyterian mutation to wild-type levels. The Providence
asp
substitution introduced a negatively charged residue into the normally cationic 2,3-bisphosphoglycerate binding pocket, potentially reducing the electrostatic repulsion in the absence of the polyanion. The average soluble globin accumulation when there was coexpression of di-α-globin and β-Lys-82→Asp-globin (rHb9.1) and heme was present in at least a threefold molar excess was 36% ± 3% of the soluble cell protein in
E. coli
. The average total accumulation (soluble globin plus insoluble globin) was 56% ± 7% of the soluble cell protein. Fermentations yielded 6.0 ± 0.3 g of soluble rHb9.1 per liter 16 h after induction and 6.4 ± 0.2 g/liter 24 h after induction. The average total globin yield was 9.4 g/liter 16 h after induction. High-level accumulation of soluble rHb in
E. coli
depends on culture conditions, the protein sequence, and the molar ratio of the heme cofactor added.
Influence of Carbohydrate Starvation and Arginine on Culturability and Amino Acid Utilization of
Lactococcus lactis
subsp.
lactis
Authors: Stuart Mark R. , Chou Lan Szu , Weimer Bart C. 
Published: December 2019

ABSTRACT

Two strains of
Lactococcus lactis
subsp.
lactis
were used to determine the influence of lactose and arginine on viability and amino acid use during carbohydrate starvation. Lactose provided energy for logarithmic-phase growth, and amino acids such as arginine provided energy after carbohydrate exhaustion. Survival time, cell numbers, and ATP concentrations increased with the addition of arginine to the basal medium. By the onset of lactose exhaustion, the concentrations of glycine-valine and glutamate had decreased by as much as 67% in
L. lactis
ML3, whereas the serine concentration increased by 97% during the same period. When no lactose was added, the concentrations of these amino acids remained constant. Similar trends were observed for
L. lactis
11454. Without lactose or arginine,
L. lactis
ML3 was nonculturable on agar but was viable after 2 days, as measured by fluorescent viability stains and intracellular ATP levels. However,
L. lactis
11454 without lactose or arginine remained culturable for at least 14 days. These data suggest that lactococci become viable but nonculturable in response to carbohydrate depletion. Additionally, these data indicate that amino acids other than arginine facilitate the survival of
L. lactis
during carbohydrate starvation.
Purification and Characterization of a Novel 5-Oxoprolinase (without ATP-Hydrolyzing Activity) from
Alcaligenes faecalis
N-38A
Authors: Nishimura Atsuhisa , Ozaki Yasunori , Oyama Hiroshi , Shin Takashi , Murao Sawao 
Published: December 2019

ABSTRACT

A novel type of 5-oxoprolinase was found in a cell extract of strain N-38A, which was later identified as
Alcaligenes faecalis
. The enzyme in the cell extract was purified to a homogeneous state with a yield of 16.6%. The molecular weight of the purified enzyme was estimated to be 47,000 by both sodium dodecyl sulfate-polyacrylamide gel electrophoresis and gel filtration, suggesting that the enzyme is a monomeric protein. The enzyme specifically catalyzed a decyclization of
l
-pyroglutamate without hydrolyzing ATP and also without any requirements for metal ions such as Mg
2+
and K
+
. The optimal pH for the decyclization was 7.4. The reaction was reversible. The equilibrium constant of the reaction,
K
eq
= [
l
-glutamate]/[
l
-pyroglutamate], was evaluated to be approximately 0.035, which indicates that the reaction tends to form
l
-pyroglutamate. The amino-terminal amino acid sequence of the enzyme was H-Glu-Pro-Arg-Leu-Asp-Thr-Ser-Gln-Leu-Tyr-Ala-Asp-Val-His-Phe-. No protein with a similar sequence was found in the DNASIS database. Based on these data, it was strongly suggested that the enzyme described here is a novel type of 5-oxoprolinase.
Role of Microcystins in Poisoning and Food Ingestion Inhibition of
Daphnia galeata
Caused by the Cyanobacterium
Microcystis aeruginosa
Authors: Rohrlack Thomas , Dittmann Elke , Henning Manfred , Börner Thomas , Kohl Johannes-Günter 
Published: December 2019

ABSTRACT

The effects of microcystins on
Daphnia galeata
, a typical filter-feeding grazer in eutrophic lakes, were investigated. To do this, the microcystin-producing wild-type strain
Microcystis aeruginosa
PCC7806 was compared with a mcy
−
PCC7806 mutant, which could not synthesize any variant of microcystin due to mutation of a microcystin synthetase gene. The wild-type strain was found to be poisonous to
D. galeata
, whereas the mcy
−
mutant did not have any lethal effect on the animals. Both variants of PCC7806 were able to reduce the
Daphnia
ingestion rate. Our results suggest that microcystins are the most likely cause of the daphnid poisoning observed when wild-type strain PCC7806 is fed to the animals, but these toxins are not responsible for inhibition of the ingestion process.
Control of Flavor Development in Wine during and after Malolactic Fermentation byOenococcus oeni
Authors: Nielsen Jan Clair , Richelieu Marianne 
Published: December 2019

ABSTRACTDuring malolactic fermentation in wine byOenococcus oeni, the degradation of citric acid was delayed compared to the degradation of malic acid. The maximum concentration of diacetyl, an intermediary compound in the citric acid metabolism with a buttery or nutty flavor, coincided with the exhaustion of malic acid in the wine. The maximum concentration of diacetyl obtained during malolactic fermentation was strongly dependent on the oxygen concentration and the redox potential of the wine and, to a lesser extent, on the initial citric acid concentration. The final diacetyl concentration in the wine was also dependent on the concentration of SO2. Diacetyl combines rather strongly with SO2(Kf= 7.2 × 103M−1in 0.1 M malate buffer [pH 3.5] at 30°C). The reaction is exothermic and reversible. If the concentration of SO2decreases during storage of the wine, the diacetyl concentration increases again.
Isolation of a Bacterial Strain Able To Degrade Branched Nonylphenol
Authors: Tanghe Tom , Dhooge Willem , Verstraete Willy 
Published: December 2019

ABSTRACT

Conventional enrichment of microorganisms on branched nonylphenol (NP) as only carbon and energy source yielded mixed cultures able to grow on the organic compound. However, plating yielded no single colonies capable, alone or in combination with other isolates, of degrading the NP in liquid culture. Therefore, a special approach was used, referred to as “serial dilution-plate resuspension,” to reduce culture complexity. In this way, one isolate, TTNP3, tentatively identified as a
Sphingomonas
sp., was found to be able to grow on NP in liquid culture. Remarkably, this isolate was able to be filtered through a 0.45-μm-pore-diameter filter. Moreover, isolate TTNP3 did not form visible colonies on mineral medium with NP, and it formed visible colonies on R
2
A agar only after a prolonged incubation of 1 week. High-performance liquid chromatography and gas chromatography-mass spectroscopy analysis of the culture media indicated that the strain starts the degradation of NP with a fission of the phenol ring and preferably uses the
para
isomer of NP and not the
ortho
isomer. No distinct accumulation of an intermediary product could be observed.
Regulatory Factors Associated with Synthesis of the Osmolyte Glycine Betaine in the Halophilic Methanoarchaeon
Methanohalophilus portucalensis
Authors: Lai Mei-Chin , Yang Daw-Renn , Chuang Ming-Jen 
Published: December 2019

ABSTRACT

The halophilic methanoarchaeon
Methanohalophilus portucalensis
can synthesize de novo and accumulate β-glutamine,
N
ɛ
-acetyl-β-lysine, and glycine betaine (betaine) as compatible solutes (osmolytes) when grown at elevated salt concentrations. Both in vivo and in vitro betaine formation assays in this study confirmed previous nuclear magnetic resonance
13
C-labelling studies showing that the de novo synthesis of betaine proceeded from glycine, sarcosine, and dimethylglycine to form betaine through threefold methylation. Exogenous sarcosine (1 mM) effectively suppressed the intracellular accumulation of betaine, and a higher level of sarcosine accumulation was accompanied by a lower level of betaine synthesis. Exogenous dimethylglycine has an effect similar to that of betaine addition, which increased the intracellular pool of betaine and suppressed the levels of
N
ɛ
-acetyl-β-lysine and β-glutamine. Both in vivo and in vitro betaine formation assays with glycine as the substrate showed only sarcosine and betaine, but no dimethylglycine. Dimethylglycine was detected only when it was added as a substrate in in vitro assays. A high level of potassium (400 mM and above) was necessary for betaine formation in vitro. Interestingly, no methylamines were detected without the addition of KCl. Also, high levels of NaCl and LiCl (800 mM) favored sarcosine accumulation, while a lower level (400 mM) favored betaine synthesis. The above observations indicate that a high sarcosine level suppressed multiple methylation while dimethylglycine was rapidly converted to betaine. Also, high levels of potassium led to greater amounts of betaine, while lower levels of potassium led to greater amounts of sarcosine. This finding suggests that the intracellular levels of both sarcosine and potassium are associated with the regulation of betaine synthesis in
M. portucalensis
.