bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dissimilar Properties of Two Recombinant Lactobacillus acidophilus Strains Displaying Salmonella FliC with Different Anchoring Motifs
Authors: Kajikawa Akinobu , Nordone Shila K. , Zhang Lin , Stoeker Laura L. , LaVoy Alora S. , Klaenhammer Todd R. , Dean Gregg A. 
Published: July 2011

ABSTRACT

Display of heterologous antigens on the cell surface is considered a useful technique for vaccine delivery by recombinant lactobacilli. In this study, two recombinant
Lactobacillus acidophilus
derivatives displaying
Salmonella
flagellin (FliC) were constructed using different anchor motifs. In one instance, the FliC protein was fused to the C-terminal region of a cell envelope proteinase (PrtP) and was bound to the cell wall by electrostatic bonds. In the other case, the same antigen was conjugated to the anchor region of mucus binding protein (Mub) and was covalently associated with the cell wall by an LPXTG motif. These two recombinant
L. acidophilus
cell surface displays resulted in dissimilar maturation and cytokine production by human myeloid dendritic cells. The surface-associated antigen was highly sensitive to simulated gastric and small intestinal juices. By supplementation with bicarbonate buffer and soybean trypsin inhibitor, the cell surface antigen was protected from proteolytic enzymes during gastric challenge
in vitro
. The protective reagents also increased the viability of the
L. acidophilus
cells upon challenge with simulated digestive juices. These results demonstrate the importance of protecting cells and their surface-associated antigens during oral immunization.
Persistent, Toxin-Antitoxin System-Independent, Tetracycline Resistance-Encoding Plasmid from a Dairy Enterococcus faecium Isolate
Authors: Li Xinhui , Alvarez Valente , Harper Willis James , Wang Hua H. 
Published: July 2011

ABSTRACT

A tetracycline-resistant (Tet
r
) dairy
Enterococcus faecium
isolate designated M7M2 was found to carry both
tet
(M) and
tet
(L) genes on a 19.6-kb plasmid. After consecutive transfer in the absence of tetracycline, the resistance-encoding plasmid persisted in 99% of the progenies. DNA sequence analysis revealed that the 19.6-kb plasmid contained 28 open reading frames (ORFs), including a
tet
(M)-
tet
(L)-
mob
gene cluster, as well as a 10.6-kb backbone highly homologous (99.9%) to the reported plasmid pRE25, but without an identified toxin-antitoxin (TA) plasmid stabilization system. The derived backbone plasmid without the Tet
r
determinants exhibited a 100% retention rate in the presence of acridine orange, suggesting the presence of a TA-independent plasmid stabilization mechanism, with its impact on the persistence of a broad spectrum of resistance-encoding traits still to be elucidated. The
tet
(M)-
tet
(L) gene cluster from M7M2 was functional and transmissible and led to acquired resistance in
Enterococcus faecalis
OG1RF by electroporation and in
Streptococcus mutans
UA159 by natural transformation. Southern hybridization showed that both the
tet
(M) and
tet
(L) genes were integrated into the chromosome of
S. mutans
UA159, while the whole plasmid was transferred to and retained in
E. faecalis
OG1RF. Quantitative real-time reverse transcription-PCR (RT-PCR) indicated tetracycline-induced transcription of both the
tet
(M) and
tet
(L) genes of pM7M2. The results indicated that multiple mechanisms might have contributed to the persistence of antibiotic resistance-encoding genes and that the plasmids pM7M2, pIP816, and pRE25 are likely correlated evolutionarily.
Spoilage-Related Activity of Carnobacterium maltaromaticum Strains in Air-Stored and Vacuum-Packed Meat
Authors: Casaburi Annalisa , Nasi Antonella , Ferrocino Ilario , Di Monaco Rossella , Mauriello Gianluigi , Villani Francesco , Ercolini Danilo 
Published: July 2011

ABSTRACT

One hundred three isolates of
Carnobacterium
spp. from raw meat were analyzed by random amplification of polymorphic DNA (RAPD) and PCR and were identified by 16S rRNA gene sequencing. Forty-five strains of
Carnobacterium maltaromaticum
were characterized for their growth capabilities at different temperatures, NaCl concentrations, and pH values and for
in vitro
lipolytic and proteolytic activities. Moreover, their spoilage potential in meat was investigated by analyzing the release of volatile organic compounds (VOCs) in meat stored in air or vacuum packs. Almost all the strains were able to grow at 4, 10, and 20°C, at pH values of 6 to 9, and in the presence of 2.5% NaCl. The release of VOCs by each strain in beef stored at 4°C in air and vacuum packs was evaluated by headspace solid-phase microextraction (HS-SPME)-gas chromatography-mass spectrometry (GC-MS) analysis. All the meat samples inoculated and stored in air showed higher numbers of VOCs than the vacuum-packed meat samples. Acetoin, 1-octen-3-ol, and butanoic acid were the compounds most frequently found under both storage conditions. The contaminated meat samples were evaluated by a sensory panel; the results indicated that for all sensory odors, no effect of strain was significant (
P
> 0.05). The storage conditions significantly affected (
P
< 0.05) the perception of dairy, spoiled-meat, and mozzarella cheese odors, which were more intense in meat stored in air than in vacuum packs but were never very intense. In conclusion, different strains of
C. maltaromaticum
can grow efficiently in meat stored at low temperatures both in air and in vacuum packs, producing volatile molecules with low sensory impacts, with a negligible contribution to meat spoilage overall.
Genetic Exchange in an Arbuscular Mycorrhizal Fungus Results in Increased Rice Growth and Altered Mycorrhiza-Specific Gene Transcription
Authors: Colard Alexandre , Angelard Caroline , Sanders Ian R. 
Published: July 2011

ABSTRACT

Arbuscular mycorrhizal fungi (AMF) are obligate symbionts with most terrestrial plants. They improve plant nutrition, particularly phosphate acquisition, and thus are able to improve plant growth. In exchange, the fungi obtain photosynthetically fixed carbon. AMF are coenocytic, meaning that many nuclei coexist in a common cytoplasm. Genetic exchange recently has been demonstrated in the AMF
Glomus intraradices
, allowing nuclei of different
Glomus intraradices
strains to mix. Such genetic exchange was shown previously to have negative effects on plant growth and to alter fungal colonization. However, no attempt was made to detect whether genetic exchange in AMF can alter plant gene expression and if this effect was time dependent. Here, we show that genetic exchange in AMF also can be beneficial for rice growth, and that symbiosis-specific gene transcription is altered by genetic exchange. Moreover, our results show that genetic exchange can change the dynamics of the colonization of the fungus in the plant. Our results demonstrate that the simple manipulation of the genetics of AMF can have important consequences for their symbiotic effects on plants such as rice, which is considered the most important crop in the world. Exploiting natural AMF genetic variation by generating novel AMF genotypes through genetic exchange is a potentially useful tool in the development of AMF inocula that are more beneficial for crop growth.
Spatial Distribution and Diffusive Motion of RNA Polymerase in Live Escherichia coli
Authors: Bratton Benjamin P. , Mooney Rachel A. , Weisshaar James C. 
Published: July 2011

ABSTRACT

By labeling the β′ subunit of RNA polymerase (RNAP), we used fluorescence microscopy to study the spatial distribution and diffusive motion of RNAP in live
Escherichia coli
cells for the first time. With a 40-ms time resolution, the spatial distribution exhibits two or three narrow peaks of 300- to 600-nm full width at half-maximum that maintain their positions within 60 nm over 1 s. The intensity in these features is 20 to 30% of the total. Fluorescence recovery after photobleaching (FRAP) measures the diffusive motion of RNAP on the 1-μm length scale. Averaged over many cells, 53% ± 19% of the RNAP molecules were mobile on the 3-s timescale, with a mean apparent diffusion constant 〈
D
RNAP
〉 of 0.22 ± 0.16 μm
2
-s
−1
. The remaining 47% were immobile even on the 30-s timescale. We interpret the immobile fraction as arising from RNAP specifically bound to DNA, either actively transcribing or not. The diffusive motion of the mobile fraction (
f
mobile
) probably involves both one-dimensional sliding during nonspecific binding to DNA and three-dimensional hopping between DNA strands. There is significant cell-to-cell heterogeneity in both
D
RNAP
and
f
mobile
.
Role of Leucine Zipper Motifs in Association of the Escherichia coli Cell Division Proteins FtsL and FtsB
Authors: Robichon Carine , Karimova Gouzel , Beckwith Jon , Ladant Daniel 
Published: July 2011

ABSTRACT

FtsL and FtsB are two inner-membrane proteins that are essential constituents of the cell division apparatus of
Escherichia coli
. In this study, we demonstrate that the leucine zipper-like (LZ) motifs, located in the periplasmic domain of FtsL and FtsB, are required for an optimal interaction between these two essential proteins.
Characterization of the Fur Regulon in Pseudomonas syringae pv. tomato DC3000
Authors: Butcher Bronwyn G. , Bronstein Philip A. , Myers Christopher R. , Stodghill Paul V. , Bolton James J. , Markel Eric J. , Filiatrault Melanie J. , Swingle Bryan , Gaballa Ahmed , Helmann John D. , Schneider David J. , Cartinhour Samuel W. 
Published: July 2011

ABSTRACT

The plant pathogen
Pseudomonas syringae
pv. tomato DC3000 (DC3000) is found in a wide variety of environments and must monitor and respond to various environmental signals such as the availability of iron, an essential element for bacterial growth. An important regulator of iron homeostasis is Fur (ferric uptake regulator), and here we present the first study of the Fur regulon in DC3000. Using chromatin immunoprecipitation followed by massively parallel sequencing (ChIP-seq), 312 chromosomal regions were highly enriched by coimmunoprecipitation with a C-terminally tagged Fur protein. Integration of these data with previous microarray and global transcriptome analyses allowed us to expand the putative DC3000 Fur regulon to include genes both repressed and activated in the presence of bioavailable iron. Using nonradioactive DNase I footprinting, we confirmed Fur binding in 41 regions, including upstream of 11 iron-repressed genes and the iron-activated genes encoding two bacterioferritins (PSPTO_0653 and PSPTO_4160), a ParA protein (PSPTO_0855), and a two-component system (TCS) (PSPTO_3382 to PSPTO_3380).
A Molecular Basis for Tungstate Selectivity in Prokaryotic ABC Transport Systems
Authors: Bevers Loes E. , Schwarz Guenter , Hagen Wilfred R. 
Published: July 2011

ABSTRACT
The essential trace compounds tungstate and molybdate are taken up by cells via ABC transporters. Despite their similar ionic radii and chemical properties, the WtpA protein selectively binds tungstate in the presence of molybdate. Using site-directed mutagenesis of conserved binding pocket residues, we established a molecular basis for tungstate selectivity.
TroA of Streptococcus suis Is Required for Manganese Acquisition and Full Virulence
Authors: Schreur Paul J. Wichgers , Rebel Johanna M. J. , Smits Mari A. , van Putten Jos P. M. , Smith Hilde E. 
Published: July 2011

ABSTRACT

Streptococcus suis
causes infections in pigs and occasionally in humans, resulting in manifestations as meningitis, sepsis, arthritis, and septic shock. For survival within the host,
S. suis
requires numerous nutrients including trace metals. Little is known about the specific proteins involved in metal scavenging in
S. suis
. In this study we evaluated the role of the putative high-affinity metal binding lipoprotein TroA in metal acquisition and virulence. A mutant strain deficient in the expression of TroA (Δ
troA
mutant) was constructed. Growth of the Δ
troA
mutant in Todd-Hewitt broth was similar to wild-type growth; however, growth of the Δ
troA
mutant in cation-deprived Todd-Hewitt broth and in porcine serum was strongly reduced compared to growth of wild-type bacteria. Supplementing the medium with extra manganese but not with magnesium, zinc, copper, nickel, or iron restored growth to wild-type levels, indicating that TroA is specifically required for growth in environments low in manganese. The Δ
troA
mutant also showed increased susceptibility to H
2
O
2
, suggesting that TroA is involved in counteracting oxidative stress. Furthermore, the expression of the
troA
gene was subject to environmental regulation at the transcript level. In a murine
S. suis
infection model, the Δ
troA
mutant displayed a nonvirulent phenotype. These data indicate that
S. suis
TroA is involved in manganese acquisition and is required for full virulence in mice.
SpoIIE Is Necessary for Asymmetric Division, Sporulation, and Expression of σ
F
, σ
E
, and σ
G
but Does Not Control Solvent Production in Clostridium acetobutylicum ATCC 824
Authors: Bi Changhao , Jones Shawn W. , Hess Daniel R. , Tracy Bryan P. , Papoutsakis Eleftherios T. 
Published: July 2011

ABSTRACT

In order to better characterize the initial stages of sporulation past Spo0A activation and the associated solventogenesis in the important industrial and model organism
Clostridium acetobutylicum
, the
spoIIE
gene was successfully disrupted and its expression was silenced. By silencing
spoIIE
, sporulation was blocked prior to asymmetric division, and no mature spores or any distinguishable morphogenetic changes developed. Upon plasmid-based complementation of
spoIIE
, sporulation was restored, although the number of spores formed was below that of the plasmid control strain. To investigate the impact of silencing
spoIIE
on the regulation of sporulation, transcript levels of
sigF
,
sigE
, and
sigG
were examined by semiquantitative reverse transcription-PCR, and the corresponding σ
F
, σ
E
, and σ
G
protein levels were determined by Western analysis. Expression of
sigF
was significantly reduced in the inactivation strain, and this resulted in very low σ
F
protein levels. Expression of
sigE
was barely detected, and no
sigG
transcript was detected at all; consequently, no σ
E
or σ
G
proteins were detected. These data suggest an autostimulatory role for σ
F
in
C. acetobutylicum
, in contrast to the model organism for endospore formation,
Bacillus subtilis
, and confirm that high-level expression of σ
F
is required for expression of σ
E
and σ
G
. Unlike the σ
F
and σ
E
inactivation strains, the SpoIIE inactivation strain did not exhibit inoculum-dependent solvent formation and produced good levels of solvents from both exponential- and stationary-phase inocula. Thus, we concluded that SpoIIE does not control solvent formation.
Mutations in Flavobacterium johnsoniae
sprE
Result in Defects in Gliding Motility and Protein Secretion
Authors: Rhodes Ryan G. , Samarasam Mudiarasan Napoleon , Van Groll Eric J. , McBride Mark J. 
Published: July 2011

ABSTRACT

Cells of the gliding bacterium
Flavobacterium johnsoniae
move rapidly over surfaces. Transposon mutagenesis was used to identify
sprE
, which is involved in gliding. Mutations in
sprE
resulted in the formation of nonspreading colonies on agar.
sprE
mutant cells in wet mounts were almost completely deficient in attachment to and movement on glass, but a small percentage of cells exhibited slight movements, indicating that the motility machinery was not completely disrupted. SprE is a predicted lipoprotein with a tetratricopeptide repeat domain. SprE is similar in sequence to
Porphyromonas gingivalis
PorW, which is required for secretion of gingipain protease virulence factors. Disruption of
F. johnsoniae
sprE
resulted in decreased extracellular chitinase activity and decreased secretion of the cell surface motility protein SprB. Reduced secretion of cell surface components of the gliding machinery, such as SprB, may account for the defects in gliding. Orthologs of
sprE
are found in many gliding and nongliding members of the phylum
Bacteroidetes
, suggesting that similar protein secretion systems are common among members of this large and diverse group of bacteria.
Riparian canopy type, management history, and successional stage control fluxes of plant litter to streams
Authors: Hoover Trent M. , Pinto Xavier , Richardson John S. 
Published: July 2011

The food webs of forest stream ecosystems are based primarily on cross-boundary flows of terrestrial plant litter (PL). As such, changes in the composition of riparian forest canopies can alter flows of PL, affecting the ecosystem functioning of adjacent streams. We measured seasonal changes in PL fluxes to 20 small streams flowing through temperate rain forests in southwestern British Columbia to determine how riparian forest type and riparian management history influence resource availability in these systems. Differences in PL fluxes among the four riparian forest types studied were most pronounced in the summer, when PL fluxes from clearcuts < riparian reserve strips and coniferous forests, and PL fluxes from deciduous-dominated forests < riparian reserve strips. PL fluxes also varied among seasons (spring < summer < autumn). Fluxes were similar in riparian reserve strips and coniferous forests of similar age, indicating that reserve strips maintain this crucial ecosystem process. Clearcutting of riparian forests dramatically increased light availability while reducing leaf litter inputs; these effects, however, lasted only a few years. As riparian forest stand age increased, inputs shifted from broadleaf to coniferous inputs, indicating a possible long-term decrease in the lability of the leaf litter resources available to stream consumers.
Activation of Tumor-Promoting Type 2 Macrophages by EGFR-Targeting Antibody Cetuximab
Authors: Pander Jan , Heusinkveld Moniek , van der Straaten Tahar , Jordanova Ekaterina S. , Baak-Pablo Renée , Gelderblom Hans , Morreau Hans , van der Burg Sjoerd H. , Guchelaar Henk-Jan , van Hall Thorbald 
Published: July 2011

AbstractPurpose: In a recent randomized phase III clinical trial in metastatic colorectal cancer patients, the addition of the anti-epidermal growth factor receptor (EGFR) monoclonal antibody (mAb) cetuximab to bevacizumab and chemotherapy resulted in decreased progression-free survival, in particular for patients with the high-affinity FcγRIIIA.Experimental Design: The presence of natural killer (NK) cells and type 2 (M2) macrophages in colorectal cancer was determined by immunohistochemistry, using antibodies to lineage-specific markers NKp46 and CD68 with CD163, respectively. Influence of tumor-bound cetuximab on M2 macrophages was carried out in vitro with EGFR-expressing tumor cells and short-term differentiated monocytes from blood donors, who were typed for the FcγRIIIA polymorphism (CD16).Results: Antibody-dependent cellular cytotoxicity by NK cells is generally proposed as one of the antitumor mechanisms of mAbs. We found that CD163-positive M2 macrophages are much more abundant in colorectal carcinomas. In vitro analysis of M2 macrophages revealed high levels of Fc-gamma receptors (FcγR) and PD-L1 and production of IL-10 and VEGF but not IL-12. These anti-inflammatory and tumor-promoting mediators were released upon coculture with EGFR-positive tumor cells loaded with low concentrations of cetuximab. Macrophage activation depended on EGFR expression on the tumor cells, FcγRs, target specificity of the mAb and mobility of antibody complexes. Cetuximab-induced macrophage responses were more pronounced for FCGR3A 158-Val (high-affinity) carriers.Conclusion: These results suggest that tumor-promoting M2 macrophages are activated by the therapeutic mAb cetuximab in the local tumor microenvironment and argue that this immune mechanism should be taken into account for the application of therapeutic antibodies. Clin Cancer Res; 17(17); 5668–73. ©2011 AACR.
Coronary Artery Wall Shear Stress Is Associated With Progression and Transformation of Atherosclerotic Plaque and Arterial Remodeling in Patients With Coronary Artery Disease
Authors: Samady Habib , Eshtehardi Parham , McDaniel Michael C. , Suo Jin , Dhawan Saurabh S. , Maynard Charles , Timmins Lucas H. , Quyyumi Arshed A. , Giddens Don P. 
Published: July 2011

Background
Experimental studies suggest that low wall shear stress (WSS) promotes plaque development and high WSS is associated with plaque destabilization. We hypothesized that low-WSS segments in patients with coronary artery disease develop plaque progression and high-WSS segments develop necrotic core progression with fibrous tissue regression.

Methods and Results

Twenty patients with coronary artery disease underwent baseline and 6-month radiofrequency intravascular ultrasound (virtual histology intravascular ultrasound) and computational fluid dynamics modeling for WSS calculation. For each virtual histology intravascular ultrasound segment (n=2249), changes in plaque area, virtual histology intravascular ultrasound–derived plaque composition, and remodeling were compared in low-, intermediate-, and high-WSS categories. Compared with intermediate-WSS segments, low-WSS segments developed progression of plaque area (
P
=0.027) and necrotic core (
P
<0.001), whereas high-WSS segments had progression of necrotic core (
P
<0.001) and dense calcium (
P
<0.001) and regression of fibrous (
P
<0.001) and fibrofatty (
P
<0.001) tissue. Compared with intermediate-WSS segments, low-WSS segments demonstrated greater reduction in vessel (
P
<0.001) and lumen area (
P
<0.001), and high-WSS segments demonstrated an increase in vessel (
P
<0.001) and lumen (
P
<0.001) area. These changes resulted in a trend toward more constrictive remodeling in low- compared with high-WSS segments (73% versus 30%;
P
=0.06) and more excessive expansive remodeling in high- compared with low-WSS segments (42% versus 15%;
P
=0.16).

Conclusions
Compared with intermediate-WSS coronary segments, low-WSS segments develop greater plaque and necrotic core progression and constrictive remodeling, and high-WSS segments develop greater necrotic core and calcium progression, regression of fibrous and fibrofatty tissue, and excessive expansive remodeling, suggestive of transformation to a more vulnerable phenotype.

Clinical Trial Registration

URL:
http://www.clinicaltrials.gov
. Unique identifier: NCT00576576.