bluuebunny/crossref_metadata_2025_split huggingface dataset:
Effect of Trichloroethylene on the Competitive Behavior of Toluene-Degrading Bacteria
Authors: Mars Astrid E. , Prins Gjalt T. , Wietzes Pieter , de Koning Wim , Janssen Dick B. 
Published: December 2019

ABSTRACT

The influence of trichloroethylene (TCE) on a mixed culture of four different toluene-degrading bacterial strains (
Pseudomonas putida
mt-2,
P. putida
F1,
P. putida
GJ31, and
Burkholderia cepacia
G4) was studied with a fed-batch culture. The strains were competing for toluene, which was added at a very low rate (31 nmol mg of cells [dry weight]
−1
h
−1
). All four strains were maintained in the mixed culture at comparable numbers when TCE was absent. After the start of the addition of TCE, the viabilities of
B. cepacia
G4 and
P. putida
F1 and GJ31 decreased 50- to 1,000-fold in 1 month. These bacteria can degrade TCE, although at considerably different rates.
P. putida
mt-2, which did not degrade TCE, became the dominant organism. Kinetic analysis showed that the presence of TCE caused up to a ninefold reduction in the affinity for toluene of the three disappearing strains, indicating that inhibition of toluene degradation by TCE occurred. While
P. putida
mt-2 took over the culture, mutants of this strain which could no longer grow on
p
-xylene arose. Most of them had less or no
meta
-cleavage activity and were able to grow on toluene with a higher growth rate. The results indicate that cometabolic degradation of TCE has a negative effect on the maintenance and competitive behavior of toluene-utilizing organisms that transform TCE.
Isolation of Aerobic Anoxygenic Photosynthetic Bacteria from Black Smoker Plume Waters of the Juan de Fuca Ridge in the Pacific Ocean
Authors: Yurkov Vladimir , Beatty J. Thomas 
Published: December 2019

ABSTRACT

A strain of the aerobic anoxygenic photosynthetic bacteria was isolated from a deep-ocean hydrothermal vent plume environment. The in vivo absorption spectra of cells indicate the presence of bacteriochlorophyll
a
incorporated into light-harvesting complex I and a reaction center. The general morphological and physiological characteristics of this new isolate are described.
Functional Display of a Heterologous Protein on the Surface of
Lactococcus lactis
by Means of the Cell Wall Anchor of
Staphylococcus aureus
Protein A
Authors: Steidler Lothar , Viaene Jasmine , Fiers Walter , Remaut Erik 
Published: December 2019

ABSTRACT

In this study, we showed that the cell wall anchor of protein A from
Staphylococcus aureus
is functional in the food-grade organism
Lactococcus lactis
. A fusion protein composed of the lactococcal Usp45 secretion signal peptide, streptavidin monomer, and the
S. aureus
protein A anchor became covalently attached to the peptidoglycan when expressed in
L. lactis
. The streptavidin moiety of the fusion protein was functionally exposed at the cellular surface.
L. lactis
cells expressing the anchored fusion polypeptide could be specifically immobilized on a biotinylated alkaline phosphatase-coated polystyrene support.
Phages InfectingVibrio vulnificusAre Abundant and Diverse in Oysters (Crassostrea virginica) Collected from the Gulf of Mexico
Authors: DePaola Angelo , Motes Miles L. , Chan Amy M. , Suttle Curtis A. 
Published: December 2019

ABSTRACTPhages infectingVibrio vulnificuswere abundant (>104phages g of oyster tissue−1) throughout the year in oysters (Crassostrea virginica) collected from estuaries adjacent to the Gulf of Mexico (Apalachicola Bay, Fla.; Mobile Bay, Ala.; and Black Bay, La.). Estimates of abundance ranged from 101to 105phages g of oyster tissue−1and were dependent on the bacterial strain used to assay the sample.V. vulnificuswas near or below detection limits (<0.3 cell g−1) from January through March and was most abundant (103to 104cells g−1) during the summer and fall, when phage abundances also tended to be greatest. The phages isolated were specific to strains ofV. vulnificus, except for one isolate that caused lysis in a few strains ofV. parahaemolyticus. Based on morphological evidence obtained by transmission electron microscopy, the isolates belonged to thePodoviridae,Styloviridae, andMyoviridae, three families of double-stranded DNA phages. One newly described morphotype belonging to thePodoviridaeappears to be ubiquitous in Gulf Coast oysters. Isolates of this morphotype have an elongated capsid (mean, 258 nm; standard deviation, 4 nm;n= 35), with some isolates having a relatively broad host range among strains ofV. vulnificus. Results from this study indicate that a morphologically diverse group of phages which infectV. vulnificusis abundant and widely distributed in oysters from estuaries bordering the northeastern Gulf of Mexico.
Effects of pH and Oxygen and Ammonium Concentrations on the Community Structure of Nitrifying Bacteria from Wastewater
Authors: Prinčič Alenka , Mahne Ivan , Megušar France , Paul Eldor A. , Tiedje James M. 
Published: December 2019

ABSTRACT

Shifts in nitrifying community structure and function in response to different ammonium concentrations (50, 500, 1,000, and 3,000 mg of N liter
−1
), pH values (pH 6.0, 7.0, and 8.2), and oxygen concentrations (1, 7, and 21%) were studied in experimental reactors inoculated with nitrifying bacteria from a wastewater treatment plant. The abilities of the communities selected for these conditions to regain their original structures after conditions were returned to the original conditions were also determined. Changes in nitrifying community structure were determined by performing an amplified ribosomal DNA (rDNA) restriction analysis of PCR products obtained with ammonia oxidizer-specific rDNA primers, by phylogenetic probing, by small-subunit (SSU) rDNA sequencing, and by performing a cellular fatty acid analysis. Digestion of ammonia-oxidizer SSU rDNA with five restriction enzymes showed that a high ammonium level resulted in a great community structure change that was reversible once the ammonium concentration was returned to its original level. The smaller changes in community structure brought about by the two pH extremes, however, were irreversible. Sequence analysis revealed that the highest ammonium environment stimulated growth of a nitrifier strain that exhibited 92.6% similarity in a partial SSU rRNA sequence to its nearest relative,
Nitrosomonas eutropha
C-91, although the PCR product did not hybridize with a general phylogenetic probe for ammonia oxidizers belonging to the β subgroup of the class
Proteobacteria
. A principal-component analysis of fatty acid methyl ester data detected changes from the starter culture in all communities under the new selective conditions, but after the standard conditions were restored, all communities produced the original fatty acid profiles.
Intracellular Changes in Ions and Organic Solutes in Halotolerant
Brevibacterium
sp. Strain JCM 6894 after Exposure to Hyperosmotic Shock
Authors: Nagata Shinichi , Adachi Kyoko , Sano Hiroshi 
Published: December 2019

ABSTRACT

In the present study we aimed to observe the intracellular responses when there was a hyperosmotic shock with a large shift in ionic strength in nutrient-rich and nutrient-poor external environments in order to clarify the availability of substrates. To do this, we used the halotolerant organism
Brevibacterium
sp. strain JCM 6894, which is able to grow in the presence of a wide range of salt concentrations. Hyperosmotic shock was induced by transferring cells in the late exponential phase of growth in a complex medium containing 0.5 M NaCl into either old or fresh culture medium containing 2 M NaCl. Changes in the growth rate, in the pH of the medium, and in the internal cation or organic solute concentrations in the cytosol after an upshock were analyzed as a function of incubation time. The cells exhibited very different responses to upshocks in fresh culture medium and in old culture medium; in fresh culture medium, growth was stimulated and the medium became more acidic, whereas the old culture medium repressed growth and the medium became more alkaline. The intracellular free Na
+
concentrations remained low (80 nmol mg of protein
−1
) after an upshock in fresh culture medium, although they quickly increased twofold in the old culture medium. In contrast, K
+
ions immediately accumulated in the cells in fresh culture medium, whereas K
+
ions were taken up quite slowly in old culture medium. Furthermore, the cells placed in fresh culture medium transiently accumulated alanine and glutamine in response to the upshock, but the cells placed in old culture medium did not. Growth of the
Brevibacterium
strain at higher levels of salinity was supported by ectoine synthesis but was not observed after the shift to high-osmolarity conditions in the old culture. In the fresh culture, however, ectoine was vigorously synthesized in cells for more than 5 h after the upshock; the concentration of ectoine in cells was more than 3,500 nmol mg of protein
−1
at 10 h, which corresponded to a ninefold increase compared to the concentration before the shock. These findings are consistent with the results of an analysis of the extracellular medium composition before and after the upshock.
Vibrio cholerae
O1 Strain TSI-4 Produces the Exopolysaccharide Materials That Determine Colony Morphology, Stress Resistance, and Biofilm Formation
Authors: Wai Sun Nyunt , Mizunoe Yoshimitsu , Takade Akemi , Kawabata Shun-Ichiro , Yoshida Shin-Ichi 
Published: December 2019

ABSTRACT

Vibrio cholerae
O1 strain TSI-4 (El Tor, Ogawa) can shift to a rugose colony morphology from its normal translucent colony morphology in response to nutrient starvation. We have investigated differences between the rugose and translucent forms of
V. cholerae
O1 strain TSI-4. Electron microscopic examination of the rugose form of TSI-4 (TSI-4/R) revealed thick, electron-dense exopolysaccharide materials surrounding polycationic ferritin-stained cells, while the ferritin-stained material was absent around the translucent form of TSI-4 (TSI-4/T). The exopolysaccharide produced by
V. cholerae
TSI-4/R was found to have a composition of
N
-acetyl-
d
-glucosamine,
d
-mannose, 6-deoxy-
d
-galactose, and
d
-galactose (7.4:10.2:2.4:3.0). The expression of an amorphous exopolysaccharide promotes biofilm development under static culture conditions. Biofilm formation by the rugose strain was determined by scanning electron microscopy, and most of the surface of the film was colonized by actively dividing rod cells. The corresponding rugose and translucent strains were compared for stress resistance. By having exopolysaccharide materials, the rugose strains acquired resistance to osmotic and oxidative stress. Our data indicated that an exopolysaccharide material on the surface of the rugose strain promoted biofilm formation and resistance to the effects of two stressing agents.
A Bioluminescence Assay Using
Nitrosomonas europaea
for Rapid and Sensitive Detection of Nitrification Inhibitors
Authors: Iizumi Taro , Mizumoto Masahiro , Nakamura Kanji 
Published: December 2019

ABSTRACT

An expression vector for the
luxAB
genes, derived from
Vibrio harveyi
, was introduced into
Nitrosomonas europaea
. Although the recombinant strain produced bioluminescence due to the expression of the
luxAB
genes under normal growing conditions, the intensity of the light emission decreased immediately, in a time-and dose-dependent manner, with the addition of ammonia monooxygenase inhibitors, such as allylthiourea, phenol, and nitrapyrin. When whole cells were challenged with several nitrification inhibitors and toxic compounds, a close relationship was found between the change in the intensity of the light emission and the level of ammonia-oxidizing activity. The response of bioluminescence to the addition of allylthiourea was considerably faster than the change in the ammonia-oxidizing rate, measured as both the O
2
uptake and NO
2
−
production rates. The bioluminescence of cells inactivated by ammonia monooxygenase inhibitor was recovered rapidly by the addition of certain substrates for hydroxylamine oxidoreductase. These results suggested that the inhibition of bioluminescence was caused by the immediate decrease of reducing power in the cell due to the inactivation of ammonia monooxygenase, as well as by the destruction of other cellular metabolic pathways. We conclude that the assay system using luminous
Nitrosomonas
can be applied as a rapid and sensitive detection test for nitrification inhibitors, and it will be used to monitor the nitrification process in wastewater treatment plants.
Estimation of the Relative Abundance of Different
Bacteroides
and
Prevotella
Ribotypes in Gut Samples by Restriction Enzyme Profiling of PCR-Amplified 16S rRNA Gene Sequences
Authors: Wood Jacqueline , Scott Karen P. , Avguštin Gorazd , Newbold C. James , Flint Harry J. 
Published: December 2019

ABSTRACT

We describe an approach for determining the genetic composition of
Bacteroides
and
Prevotella
populations in gut contents based on selective amplification of 16S rRNA gene sequences (rDNA) followed by cleavage of the amplified material with restriction enzymes. The relative contributions of different ribotypes to total
Bacteroides
and
Prevotella
16S rDNA are estimated after end labelling of one of the PCR primers, and the contribution of
Bacteroides
and
Prevotella
sequences to total eubacterial 16S rDNA is estimated by measuring the binding of oligonucleotide probes to amplified DNA.
Bacteroides
and
Prevotella
16S rDNA accounted for between 12 and 62% of total eubacterial 16S rDNA in samples of ruminal contents from six sheep and a cow. Ribotypes 4, 5, 6, and 7, which include most cultivated rumen
Prevotella
strains, together accounted for between 20 and 86% of the total amplified
Bacteroides
and
Prevotella
rDNA in these samples. The most abundant
Bacteroides
or
Prevotella
ribotype in four animals, however, was ribotype 8, for which there is only one known cultured isolate, while ribotypes 1 and 2, which include many colonic
Bacteroides
spp., were the most abundant in two animals. This indicates that some abundant
Bacteroides
and
Prevotella
groups in the rumen are underrepresented among cultured rumen
Prevotella
isolates. The approach described here provides a rapid, convenient, and widely applicable method for comparing the genotypic composition of bacterial populations in gut samples.
Toxic Effects of Modified Fenton Reactions on
Xanthobacter flavus
FB71
Authors: Büyüksönmez Fatïh , Hess Thomas F. , Crawford Ronald L. , Watts Richard J. 
Published: December 2019

ABSTRACT

The toxic effects of modified Fenton reactions on
Xanthobacter flavus
FB71, measured as microbial survival rates, were determined as part of an investigation of simultaneous abiotic and biotic oxidations of xenobiotic chemicals. A central composite, rotatable experimental design was developed to study the survival rates of
X. flavus
under various concentrations of hydrogen peroxide and iron(II) and at different initial cell populations. A model based on the experimental results, relating microorganism survival to the variables of peroxide, iron, and cellular concentrations was formulated and fit the data reasonably well, with a coefficient of determination of 0.76. The results of this study indicate that the use of simultaneous abiotic and biotic processes for the treatment of xenobiotic compounds may be possible.
Improvement of Nitrogen Assimilation and Fermentation Kinetics under Enological Conditions by Derepression of Alternative Nitrogen-Assimilatory Pathways in an IndustrialSaccharomyces cerevisiaeStrain
Authors: Salmon Jean-Michel , Barre Pierre 
Published: December 2019

ABSTRACTMetabolism of nitrogen compounds by yeasts affects the efficiency of wine fermentation. Ammonium ions, normally present in grape musts, reduce catabolic enzyme levels and transport activities for nonpreferred nitrogen sources. This nitrogen catabolite repression severely impairs the utilization of proline and arginine, both common nitrogen sources in grape juice that require the proline utilization pathway for their assimilation. We attempted to improve fermentation performance by genetic alteration of the regulation of nitrogen-assimilatory pathways inSaccharomyces cerevisiae. One mutant carrying a recessive allele ofure2was isolated from an industrialS. cerevisiaestrain. This mutation strongly deregulated the proline utilization pathway. Fermentation kinetics of this mutant were studied under enological conditions on simulated standard grape juices with various nitrogen levels. Mutant strains produced more biomass and exhibited a higher maximum CO2production rate than the wild type. These differences were primarily due to the derepression of amino acid utilization pathways. When low amounts of dissolved oxygen were added, the mutants could assimilate proline. Biomass yield and fermentation rate were consequently increased, and the duration of the fermentation was substantially shortened.S. cerevisiaestrains lacking URE2 function could improve alcoholic fermentation of natural media where proline and other poorly assimilated amino acids are the major potential nitrogen source, as is the case for most fruit juices and grape musts.
Acid-Sensitive Enteric Pathogens Are Protected from Killing under Extremely Acidic Conditions of pH 2.5 when They Are Inoculated onto Certain Solid Food Sources
Authors: Waterman Scott R. , Small P. L. C. 
Published: December 2019

ABSTRACT

Gastric acidity is recognized as the first line of defense against food-borne pathogens, and the ability of pathogens to resist this pH corresponds to their oral infective dose (ID). Naturally occurring and genetically engineered acid-sensitive enteric pathogens were examined for their ability to survive under acidic conditions of pH 2.5 for 2 h at 37°C when inoculated onto ground beef. Each of the strains displayed significantly high survival rates under these normally lethal conditions. The acid-sensitive pathogens
Campylobacter jejuni
and
Vibrio cholerae
, which were protected at lower levels from acid-induced killing by ground beef under these conditions, were sensitive to killing in acidified media at pH 5.0 but survived at pH 6.0.
Salmonella
inoculated onto the surface of preacidified ground beef could not survive if the pH on the surface of the beef was 2.61 or lower but was viable if the surface pH was 3.27. This implies that the pH of the microenvironment occupied by the bacteria on the surface of the food source is critical for their survival.
Salmonella
was also shown to be protected from killing when inoculated onto boiled egg white, a food source high in protein and low in fat. These results may explain why
Salmonella
species have a higher oral ID of approximately 10
5
cells when administered under defined conditions but have been observed to cause disease at doses as low as 50 to 100 organisms when consumed as part of a contaminated food source. They may also help explain why some pathogens are associated primarily with food-borne modes of transmission rather than fecal-oral transmission.
Optimization of Cry3A Yields in
Bacillus thuringiensis
by Use of Sporulation-Dependent Promoters in Combination with the STAB-SD mRNA Sequence
Authors: Park Hyun-Woo , Ge Baoxue , Bauer Leah S. , Federici Brian A. 
Published: December 2019

ABSTRACT

The insecticidal activity of
Bacillus thuringiensis
strains toxic to coleopterous insects is due to Cry3 proteins assembled into small rectangular crystals. Toxin synthesis in these strains is dependent primarily upon a promoter that is active in the stationary phase and a STAB-SD sequence that stabilizes the
cry3
transcript-ribosome complex. Here we show that significantly higher yields of Cry3A can be obtained by using dual sporulation-dependent
cyt1Aa
promoters to drive the expression of
cry3Aa
when the STAB-SD sequence is included in the construct. The Cry3A yield per unit of culture medium obtained with this expression system was 12.7-fold greater than that produced by DSM 2803, the wild-type strain of
B. thuringiensis
from which Cry3Aa was originally described, and 1.4-fold greater than that produced by NB176, a mutant of the same strain containing two or three copies of
cry3Aa
, which is the active ingredient of the commercial product Novodor, used for control of beetle pests. The toxicities of Cry3A produced with this construct or the wild-type strain were similar when assayed against larvae of the cottonwood leaf beetle,
Chrysomela scripta
. The volume of Cry3A crystals produced with
cyt1Aa
promoters and the STAB-SD sequence was 1.3-fold that of typical bipyramidal Cry1 crystals toxic to lepidopterous insects. The dual-promoter/STAB-SD system offers an additional method for potentially improving the efficacy of insecticides based on
B. thuringiensis
.
Closely Related Plasmid Replicons Coexisting in the PhytopathogenPseudomonas syringaeShow a Mosaic Organization of the Replication Region and Altered Incompatibility Behavior
Authors: Sesma Ane , Sundin George W. , Murillo Jesús 
Published: December 2019

ABSTRACTManyPseudomonas syringaestrains contain native plasmids that are important for host-pathogen interactions, and most of them contain several coexisting plasmids (pPT23A-like plasmids) that cross-hybridize to replication sequences from pPT23A, which also carries a gene cluster coding for the phytotoxin coronatine inP. syringaepv. tomato PT23. In this study, three functional pPT23A-like replicons were cloned fromP. syringaepv. glycinea race 6, suggesting that the compatibility of highly related replicons is a common feature ofP. syringaestrains. Hybridization experiments using three separate incompatibility determinants previously identified from pPT23A and therulAB(UV radiation tolerance) genes showed that the organization of the replication region among pPT23A-like plasmids from severalP. syringaepathovars is poorly conserved. The putativerepAgene from four pPT23A-like replicons fromP. syringaepv. glycinea race 6 was amplified by using specific primers. The restriction profiles of the resulting PCR products for the race 6 plasmids were more similar to each other than they were to that of pPT23A. These data, together with the existence of other cross-hybridizing DNA regions around the replicon among the race 6 pPT23A-like plasmids, suggest that some of these plasmids may have originated from duplication events. Our results also imply that modifications of therepAsequences and the poor conservation of putative maintenance determinants contribute to the suppression of incompatibility among members of the pPT23A-like family, thus enhancing the genomic plasticity ofP. syringae.