bluuebunny/crossref_metadata_2025 huggingface dataset:
Glutathione Protects
Lactobacillus sanfranciscensis
against Freeze-Thawing, Freeze-Drying, and Cold Treatment
Authors: Zhang Juan , Du Guo-Cheng , Zhang Yanping , Liao Xian-Yan , Wang Miao , Li Yin , Chen Jian
Published: March 2010

Lactobacillus sanfranciscensis
DSM20451 cells containing glutathione (GSH) displayed significantly higher resistance against cold stress induced by freeze-drying, freeze-thawing, and 4°C cold treatment than those without GSH. Cells containing GSH were capable of maintaining their membrane structure intact when exposed to freeze-thawing. In addition, cells containing GSH showed a higher proportion of unsaturated fatty acids in cell membranes upon long-term cold treatment. Subsequent studies revealed that the protective role of GSH against cryodamage of the cell membrane is partly due to preventing peroxidation of membrane fatty acids and protecting Na
+
,K
+
-ATPase. Intracellular accumulation of GSH enhanced the survival and the biotechnological performance of
L. sanfranciscensis
, suggesting that the robustness of starters for sourdough fermentation can be improved by selecting GSH-accumulating strains. Moreover, the results of this study may represent a further example of mechanisms for stress responses in lactic acid bacteria.
Characterization of Immunostimulatory CpG-Rich Sequences from DifferentBifidobacteriumSpecies
Authors: Ménard Odile , Gafa Valérie , Kapel Nathalie , Rodriguez Bertrand , Butel Marie-José , Waligora-Dupriet Anne-Judith
Published: March 2010

The beneficial effects ofBifidobacteriumare partly due to its immunostimulatory properties. These immunostimulatory properties may be linked to the presence of unmethylated CpG motifs specific to bacterial DNA, which may induce a TH1 response by activating Toll-like receptors (TLR). Usingin silicoanalyses, PCR amplification, and dot blotting, we characterized the CpG content of various bifidobacterial strains and evaluated the immunostimulatory properties and genomic heterogeneity of these motifs in the genus. Ourin silicostudy, based on entire genome sequences from five bifidobacterial strains, showed thatBifidobacteriumgenomes contain numerous CpG motifs, including 5′-purine-purine-CG-pyrimidine-pyrimidine-3′ and 5′-purine-TCG-pyrimidine-pyrimidine-3′ motifs, and biologically active sequences previously identified in lactic acid bacteria. We identified four CpG-rich sequences withBifidobacterium longumNCC2705. Two sequences with a percent G+C of about 68% included 14 and 16 CpG motifs. Two sequences with a percent G+C of about 60% included 16 and 6 CpG motifs. These sequences induce the production of monocyte chemoattractant protein 1 (MCP-1) and tumor necrosis factor alpha (TNF-α) through a pattern of TLR9 stimulation on RAW 264.7 macrophages. No link could be established between their immunostimulatory properties, the number of CpG motifs, and percent G+C. We investigated inter- and intraspecies heterogeneity in 71 strains of various origins. These sequences were highly conserved in the genus. No link was found between the presence of the CpG-rich sequence and the origin of the strains (healthy, allergic, or preterm infants). The high frequency of CpG motifs in the DNA ofBifidobacteriummay play an important role in the immunostimulatory properties of commensal or probiotic bifidobacterial strains.
Cyclic GMP as a Second Messenger in the Nitric Oxide-Mediated Conidiation of the MycoparasiteConiothyrium minitans
Authors: Li Bo , Fu Yanping , Jiang Daohong , Xie Jiatao , Cheng Jiasen , Li Guoqing , Hamid Mahammad Imran , Yi Xianhong
Published: March 2010

Understanding signaling pathways that modulate conidiation of mitosporic fungi is of both practical and theoretical importance. The enzymatic origin of nitric oxide (NO) and its roles in conidiation by the sclerotial parasiteConiothyrium minitanswere investigated. The activity of a nitric oxide synthase-like (NOS-like) enzyme was detected inC. minitansas evidenced by the conversion ofl-arginine tol-citrulline. Guanylate cyclase (GC) activity was also detected indirectly inC. minitanswith the GC-specific inhibitor 1H-[1,2,4]oxadiazolo[4,3-a]quinoxalin-1-one (ODQ), which significantly reduced production of cyclic GMP (cGMP). The dynamics of NOS activity were closely mirrored by the cGMP levels during pycnidial development, with the highest levels of both occurring at the pycnidial initiation stage ofC. minitans. Furthermore, the NO donor, sodium nitroprusside (SNP), stimulated the accumulation of cGMP almost instantly in mycelium during the hyphal growth stage. When the activity of NOS or GC was inhibited withNω-nitro-l-arginine or ODQ, conidial production ofC. minitanswas suppressed or completely eliminated; however, the suppression of conidiation by ODQ could be reversed by exogenous cGMP. The results also showed that conidiation of anl-arginine auxotroph could be restored by the NO donor SNP, but not by cGMP. Thus, NO-mediated conidiation has more than one signal pathway, including the cGMP signal pathway and another yet-unknown pathway, and both are essential for conidiation inC. minitans.
Analysis of
Lactobacillus sakei
Mutants Selected after Adaptation to the Gastrointestinal Tracts of Axenic Mice
Authors: Chiaramonte Fabrizio , Anglade Patricia , Baraige Fabienne , Gratadoux Jean-Jacques , Langella Philippe , Champomier-Vergès Marie-Christine , Zagorec Monique
Published: March 2010

We recently showed that
Lactobacillus sakei
, a natural meat-borne lactic acid bacterium, can colonize the gastrointestinal tracts (GIT) of axenic mice but that this colonization in the intestinal environment selects
L. sakei
mutants showing modified colony morphology (small and rough) and cell shape, most probably resulting from the accumulation of various mutations that confer a selective advantage for persistence in the GIT. In the present study, we analyzed such clones, issued from three different
L. sakei
strains, in order to determine which functions were modified in the mutants. In the elongated filamentous cells of the rough clones, transmission electron microscopy (TEM) analysis showed a septation defect and dotted and slanted black bands, suggesting the presence of a helical structure around the cells. Comparison of the cytoplasmic and cell wall/membrane proteomes of the meat isolate
L. sakei
23K and of one of its rough derivatives revealed a modified expression for 38 spots. The expression of six oxidoreductases, several stress proteins, and four ABC transporters was strongly reduced in the GIT-adapted strain, while the actin-like MreB protein responsible for cell shaping was upregulated. In addition, the expression of several enzymes involved in carbohydrate metabolism was modified, which may correlate with the observation of modified growth of mutants on various carbon sources. These results suggest that the modifications leading to a better adaptation to the GIT are pleiotropic and are characterized in a rough mutant by a different stress status, a cell wall modification, and modified use of energy sources, leading to an improved fitness for the colonization of the GIT.
Prevalence and Diversity of Toxigenic
Clostridium perfringens
and
Clostridium difficile
among Swine Herds in the Midwest
Authors: Baker Ashley A. , Davis Ellen , Rehberger Thomas , Rosener Daniel
Published: March 2010

Clostridium perfringens
and
Clostridium difficile
are associated with scours in the neonatal piglet and are an economic concern in swine production. The objective of this study was to characterize the prevalence and diversity of
C. perfringens
and
C. difficile
isolates obtained from scouring neonatal piglets in a large integrated production system, as well as in smaller independently owned regional farms. Rectal swabs were collected from 333 pigs at 11 sites in an integrated swine production system and from an additional 180 pigs at 16 regional farms located throughout the Midwest.
C. perfringens
was isolated from 89.8% of the pigs swabbed at the integrated sites, and
C. difficile
was isolated from 57.7% of these pigs. Of the pigs from the regional farms sampled, 95.6% were positive for isolation of
C. perfringens
and 27.2% were positive for
C. difficile
. Toxigenic isolates were typed using random amplified polymorphic DNA (RAPD) PCR, and were placed in four dendrograms for
C. perfringens
and
C. difficile
populations isolated from the integrated sites and regional farms. Diversity indices showed that there was greater diversity in
C. difficile
populations and in populations isolated from the regional farms. A subset of isolates from the
C. difficile
dendrograms were further toxinotyped by amplification of the pathogenicity locus and subsequent digestion by HincII, AccI, and EcoRI. Of the 45 isolates typed, 44 were determined to be toxinotype V. The results of this study illustrate the diversity of
C. perfringens
and
C. difficile
isolates and the prevalence of these pathogens in swine production sites.
Raman Spectroscopy-Compatible Inactivation Method for Pathogenic Endospores
Authors: Stöckel S. , Schumacher W. , Meisel S. , Elschner M. , Rösch P. , Popp J.
Published: March 2010

Micro-Raman spectroscopy is a fast and sensitive tool for the detection, classification, and identification of biological organisms. The vibrational spectrum inherently serves as a fingerprint of the biochemical composition of each bacterium and thus makes identification at the species level, or even the subspecies level, possible. Therefore, microorganisms in areas susceptible to bacterial contamination, e.g., clinical environments or food-processing technology, can be sensed. Within the scope of point-of-care-testing also, detection of intentionally released biosafety level 3 (BSL-3) agents, such as
Bacillus anthracis
endospores, or their products is attainable. However, no Raman spectroscopy-compatible inactivation method for the notoriously resistant
Bacillus
endospores has been elaborated so far. In this work we present an inactivation protocol for endospores that permits, on the one hand, sufficient microbial inactivation and, on the other hand, the recording of Raman spectroscopic signatures of single endospores, making species-specific identification by means of highly sophisticated chemometrical methods possible. Several physical and chemical inactivation methods were assessed, and eventually treatment with 20% formaldehyde proved to be superior to the other methods in terms of sporicidal capacity and information conservation in the Raman spectra. The latter fact has been verified by successfully using self-learning machines (such as support vector machines or artificial neural networks) to identify inactivated
B. anthracis
-related endospores with adequate accuracies within the range of the limited model database employed.
Influence of Refuse Sites on the Prevalence of
Campylobacter
spp. and
Salmonella
Serovars in Seagulls
Authors: Ramos Raül , Cerdà-Cuéllar Marta , Ramírez Francisco , Jover Lluís , Ruiz Xavier
Published: March 2010

Wild animals are well-known reservoirs of
Campylobacter
and
Salmonella
. We investigated the influence of insalubrious diets on the prevalence of both enterobacteria in seagulls.
Campylobacter
occurrence in gull chicks sampled along the northeastern Iberian coast was directly related to the degree of refuse consumption. High
Salmonella
values from the sampling sites did not reflect any dietary relationship.
Production and Characterization of a Novel Bioflocculant from
Bacillus licheniformis
Authors: Xiong Yuyan , Wang Yuanpeng , Yu Yi , Li Qingbiao , Wang Haitao , Chen Ronghui , He Ning
Published: March 2010

A bacterium producing an extracellular bioflocculant was isolated from contaminated LB medium and identified as
Bacillus licheniformis
by 16S rRNA gene sequencing and its biochemical/physiological characteristics. The optimum culture conditions for flocculant production were an initial medium pH of 7.2 and an inoculum size of 4% (vol/vol). The maximum flocculating activity (700 U/ml) was obtained after cultivation at 37°C for 48 h. Chemical analyses of the purified bioflocculant revealed that it was a proteoglycan composed of 89% carbohydrate and 11% protein (wt/wt). The mass ratio of neutral sugar, amino sugar, and uronic acid was measured at 7.9:4:1. Infrared spectrometry further indicated the presence of carboxyl, hydroxyl, and amino groups, typical of heteropolysaccharide. The average mass of the bioflocculant was calculated to be 1.76 × 10
6
Da. Scanning electron microscopy (SEM) images of the bioflocculant showed an irregular structure with netted texture. Its efficient flocculation capabilities suggest potential applications in industry.
Modeling the Lag Period and Exponential Growth of
Listeria monocytogenes
under Conditions of Fluctuating Temperature and Water Activity Values
Authors: Muñoz-Cuevas Marina , Fernández Pablo S. , George Susan , Pin Carmen
Published: March 2010

The dynamic model for the growth of a bacterial population described by Baranyi and Roberts (J. Baranyi and T. A. Roberts, Int. J. Food Microbiol.
23:
277-294, 1994) was applied to model the lag period and exponential growth of
L
isteria monocytogenes
under conditions of fluctuating temperature and water activity (a
w
) values. To model the duration of the lag phase, the dependence of the parameter
h
0
, which quantifies the amount of work done during the lag period, on the previous and current environmental conditions was determined experimentally. This parameter depended not only on the magnitude of the change between the previous and current environmental conditions but also on the current growth conditions. In an exponentially growing population, any change in the environment requiring a certain amount of work to adapt to the new conditions initiated a lag period that lasted until that work was finished. Observations for several scenarios in which exponential growth was halted by a sudden change in the temperature and/or a
w
were in good agreement with predictions. When a population already in a lag period was subjected to environmental fluctuations, the system was reset with a new lag phase. The work to be done during the new lag phase was estimated to be the workload due to the environmental change plus the unfinished workload from the uncompleted previous lag phase.
Revelation by Single-Nucleotide Polymorphism Genotyping That Mutations Leading to a Premature Stop Codon in
inlA
Are Common among
Listeria monocytogenes
Isolates from Ready-To-Eat Foods but Not Human Listeriosis Cases
Authors: Van Stelten A. , Simpson J. M. , Ward T. J. , Nightingale K. K.
Published: March 2010

Listeria monocytogenes
utilizes internalin A (InlA; encoded by
inlA
) to cross the intestinal barrier to establish a systemic infection. Multiple naturally occurring mutations leading to a premature stop codon (PMSC) in
inlA
have been reported worldwide, and these mutations are causally associated with attenuated virulence. Five
inlA
PMSC mutations recently discovered among isolates from France and the United States were included as additional markers in our previously described
inlA
single-nucleotide polymorphism (SNP) genotyping assay. This assay was used to screen >1,000
L. monocytogenes
isolates from ready-to-eat (RTE) foods (
n
= 502) and human listeriosis cases (
n
= 507) for 18
inlA
PMSC mutations. A significantly (
P
< 0.0001) greater proportion of RTE food isolates (45.0%) carried a PMSC mutation in
inlA
compared to human clinical isolates (5.1%). The proportion of
L. monocytogenes
with or without PMSC mutations in
inlA
was similar among isolates from different RTE food categories except for deli meats, which included a marginally higher proportion (
P
= 0.12) of isolates carrying a PMSC in
inlA
. We also analyzed the distribution of epidemic clone (EC) strains, which have been linked to the majority of listeriosis outbreaks worldwide and are overrepresented among sporadic cases in the United States. We observed a significant (
P
< 0.05) overrepresentation of EC strains in deli and seafood salads and a significant (
P
< 0.05) underrepresentation of EC strains in smoked seafood. These results provide important data to predict the human health risk of exposure to
L. monocytogenes
strains that differ in pathogenic potential through consumption of contaminated RTE foods.
Isolation ofRickettsia parkeriand Identification of a Novel Spotted Fever GroupRickettsiasp. from Gulf Coast Ticks (Amblyomma maculatum) in the United States
Authors: Paddock Christopher D. , Fournier Pierre-Edouard , Sumner John W. , Goddard Jerome , Elshenawy Yasmin , Metcalfe Maureen G. , Loftis Amanda D. , Varela-Stokes Andrea
Published: March 2010

Until recently,Amblyomma maculatum(the Gulf Coast tick) had garnered little attention compared to other species of human-biting ticks in the United States.A. maculatumis now recognized as the principal vector ofRickettsia parkeri, a pathogenic spotted fever group rickettsia (SFGR) that causes an eschar-associated illness in humans that resembles Rocky Mountain spotted fever. A novel SFGR, distinct from other recognizedRickettsiaspp., has also been detected recently inA. maculatumspecimens collected in several regions of the southeastern United States. In this study, 198 questing adult Gulf Coast ticks were collected at 4 locations in Florida and Mississippi; 28% of these ticks were infected withR. parkeri, and 2% of these were infected with a novel SFGR. Seventeen isolates ofR. parkerifrom individual specimens ofA. maculatumwere cultivated in Vero E6 cells; however, all attempts to isolate the novel SFGR were unsuccessful. Partial genetic characterization of the novel SFGR revealed identity with several recently described, incompletely characterized, and noncultivated SFGR, including “CandidatusRickettsia andeanae” andRickettsiasp. Argentina detected in several species of Neotropical ticks from Argentina and Peru. These findings suggest that each of these “novel” rickettsiae represent the same species. This study considerably expanded the number of low-passage,A. maculatum-derived isolates ofR. parkeriand characterized a second, sympatricRickettsiasp. found in Gulf Coast ticks.
Heterologous Expression of the Oxytetracycline Biosynthetic Pathway in
Myxococcus xanthus
Authors: Stevens D. Cole , Henry Michael R. , Murphy Kimberly A. , Boddy Christopher N.
Published: March 2010

New natural products for drug discovery may be accessed by heterologous expression of bacterial biosynthetic pathways in metagenomic DNA libraries. However, a “universal” host is needed for this experiment. Herein, we show that
Myxococcus xanthus
is a potential “universal” host for heterologous expression of polyketide biosynthetic gene clusters.
Impact of Siderophore Production by
Pseudomonas syringae
pv. syringae 22d/93 on Epiphytic Fitness and Biocontrol Activity against
Pseudomonas syringae
pv. glycinea 1a/96
Authors: Wensing Annette , Braun Sascha D. , Büttner Petra , Expert Dominique , Völksch Beate , Ullrich Matthias S. , Weingart Helge
Published: March 2010

The use of naturally occurring microbial antagonists to suppress plant diseases offers a favorable alternative to classical methods of plant protection. The soybean epiphyte
Pseudomonas syringae
pv. syringae strain 22d/93 shows great potential for controlling
P. syringae
pv. glycinea, the causal agent of bacterial blight of soybean. Its activity against
P. syringae
pv. glycinea is highly reproducible even in field trials, and the suppression mechanisms involved are of special interest. In this work we demonstrated that
P
.
syringae
pv. syringae 22d/93 produced a significantly larger amount of siderophores than the pathogen
P. syringae
pv. glycinea produced. While
P
.
syringae
pv. syringae 22d/93 and
P. syringae
pv. glycinea produce the same siderophores, achromobactin and pyoverdin, the regulation of siderophore biosynthesis in the former organism is very different from that in the latter organism. The epiphytic fitness of
P
.
syringae
pv. syringae 22d/93 mutants defective in siderophore biosynthesis was determined following spray inoculation of soybean leaves. The population size of the siderophore-negative mutant
P
.
syringae
pv. syringae strain 22d/93ΔSid was 2 orders of magnitude lower than that of the wild type 10 days after inoculation. The growth deficiency was compensated for when wound inoculation was used, indicating the availability of iron in the presence of small lesions on the leaves. Our results suggest that siderophore production has an indirect effect on the biocontrol activity of
P
.
syringae
pv. syringae 22d/93. Although siderophore-defective mutants of
P
.
syringae
pv. syringae 22d/93 still suppressed development of bacterial blight caused by
P. syringae
pv. glycinea, siderophore production enhanced the epiphytic fitness and thus the competitiveness of the antagonist.
Nuclear Dynamics, Mitosis, and the Cytoskeleton during the Early Stages of Colony Initiation in Neurospora crassa
Authors: Roca M. Gabriela , Kuo Hsiao-Che , Lichius Alexander , Freitag Michael , Read Nick D.
Published: March 2010

Neurospora crassa
macroconidia form germ tubes that are involved in colony establishment and conidial anastomosis tubes (CATs) that fuse to form interconnected networks of conidial germlings. Nuclear and cytoskeletal behaviors were analyzed in macroconidia, germ tubes, and CATs in strains that expressed fluorescently labeled proteins. Heterokaryons formed by CAT fusion provided a rapid method for the imaging of multiple labeled fusion proteins and minimized the potential risk of overexpression artifacts. Mitosis occurred more slowly in nongerminated macroconidia (1.0 to 1.5 h) than in germ tubes (16 to 20 min). The nucleoporin SON-1 was not released from the nuclear envelope during mitosis, which suggests that
N. crassa
exhibits a form of “closed mitosis.” During CAT homing, nuclei did not enter CATs, and mitosis was arrested. Benomyl treatment showed that CAT induction, homing, fusion, as well as nuclear migration through fused CATs do not require microtubules or mitosis. Three
ropy
mutants (
ro-1
,
ro-3
, and
ro-11
) defective in the dynein/dynactin microtubule motor were impaired in nuclear positioning, but nuclei still migrated through fused CATs. Latrunculin B treatment, imaging of F-actin in living cells using Lifeact-red fluorescent protein (RFP), and analysis of mutants defective in the Arp2/3 complex demonstrated that actin plays important roles in CAT fusion.
Mitochondrial DNA Heteroplasmy in Candida glabrata after Mitochondrial Transformation
Authors: Zhou Jingwen , Liu Liming , Chen Jian
Published: March 2010

Genetic manipulation of mitochondrial DNA (mtDNA) is the most direct method for investigating mtDNA, but until now, this has been achieved only in the diploid yeast
Saccharomyces cerevisiae
. In this study, the
ATP6
gene on mtDNA of the haploid yeast
Candida glabrata
(
Torulopsis glabrata
) was deleted by biolistic transformation of DNA fragments with a recoded
ARG8

m

mitochondrial genetic marker, flanked by homologous arms to the
ATP6
gene. Transformants were identified by arginine prototrophy. However, in the transformants, the original mtDNA was not lost spontaneously, even under arginine selective pressure. Moreover, the mtDNA transformants selectively lost the transformed mtDNA under aerobic conditions. The mtDNA heteroplasmy in the transformants was characterized by PCR, quantitative PCR, and Southern blotting, showing that the heteroplasmy was relatively stable in the absence of arginine. Aerobic conditions facilitated the loss of the original mtDNA, and anaerobic conditions favored loss of the transformed mtDNA. Moreover, detailed investigations showed that increases in reactive oxygen species in mitochondria lacking
ATP6
, along with their equal cell division, played important roles in determining the dynamics of heteroplasmy. Based on our analysis of mtDNA heteroplasmy in
C. glabrata
, we were able to generate homoplasmic Δ
atp6
mtDNA strains.
High-Quality Draft Genome Sequences of 28
Enterococcus
sp. Isolates
Authors: Palmer Kelli L. , Carniol Karen , Manson Janet M. , Heiman David , Shea Terry , Young Sarah , Zeng Qiandong , Gevers Dirk , Feldgarden Michael , Birren Bruce , Gilmore Michael S.
Published: March 2010

The enterococci are low-GC Gram-positive bacteria that have emerged as leading causes of hospital-acquired infection. They are also commensals of the gastrointestinal tract of healthy humans and most other animals with gastrointestinal flora and are important for food fermentations. Here we report the availability of draft genome sequences for 28 enterococcal strains of diverse origin, including the species
Enterococcus faecalis
,
E. faecium
,
E. casseliflavus
, and
E. gallinarum
.
Crystal Structure of Activated CheY1 from
Helicobacter pylori
Authors: Lam Kwok Ho , Ling Thomas Kin Wah , Au Shannon Wing Ngor
Published: March 2010

Chemotaxis is an important virulence factor for
Helicobacter pylori
colonization and infection. The chemotactic system of
H. pylori
is marked by the presence of multiple response regulators: CheY1, one CheY-like-containing CheA protein (CheAY2), and three CheV proteins. Recent studies have demonstrated that these molecules play unique roles in the chemotactic signal transduction mechanisms of
H. pylori
. Here we report the crystal structures of BeF

3
−

-activated CheY1 from
H. pylori
resolved to 2.4 Å. Structural comparison of CheY1 with active-site residues of BeF

3
−

-bound CheY from
Escherichia coli
and fluorescence quenching experiments revealed the importance of Thr84 in the phosphotransfer reaction. Complementation assays using various nonchemotactic
E. coli
mutants and pull-down experiments demonstrated that CheY1 displays differential association with the flagellar motor in
E. coli
. The structural rearrangement of helix 5 and the C-terminal loop in CheY1 provide a different interaction surface for FliM. On the other hand, interaction of the CheA-P2 domain with CheY1, but not with CheY2/CheV proteins, underlines the preferential recognition of CheY1 by CheA in the phosphotransfer reaction. Our results provide the first structural insight into the features of the
H. pylori
chemotactic system as a model for
Epsilonproteobacteria
.
Characterization of the
Klebsiella aerogenes
Urease Accessory Protein UreD in Fusion with the Maltose Binding Protein
Authors: Carter Eric L. , Hausinger Robert P.
Published: March 2010

Assembly of the
Klebsiella aerogenes
urease metallocenter requires four accessory proteins, UreD, UreE, UreF, and UreG, to effectively deliver and incorporate two Ni
2+
ions into the nascent active site of the urease apoprotein (UreABC). Each accessory protein has been purified and characterized with the exception of UreD due to its insolubility when it is overproduced in recombinant cells. In this study, a translational fusion was made between the maltose binding protein (MBP) and UreD, with the resulting MBP-UreD found to be soluble in
Escherichia coli
cell extracts and able to complement a Δ
ureD
-urease cluster in this host microorganism. MBP-UreD was purified as a large multimer (>670 kDa) that bound approximately 2.5 Ni
2+
ions (

K
d

of ∼50 μM, where

K
d

is the dissociation constant) per UreD protomer according to equilibrium dialysis measurements. Zn
2+
directly competes with 10-fold higher affinity (∼4 Zn
2+
ions per protomer;

K
d

of 5 μM) for the Ni
2+
binding sites. MBP pulldown experiments demonstrated that the UreD domain of MBP-UreD formed
in vivo
complexes with UreF, UreG, UreF plus UreG, or UreABC when these proteins were overproduced in the same
E. coli
cells. In addition, a UreABC-(MBP-UreD)-UreFG complex was observed in cells producing all urease components. Comparative
in vitro
binding experiments with purified proteins demonstrated an approximate 1:1 binding ratio between the UreD domain of MBP-UreD and the UreF domain of the UreEF fusion, only weak or transient interaction between MBP-UreD and UreG, and no binding with UreABC. These studies are the first to describe the properties of purified UreD, and they extend our understanding of its binding partners both
in vitro
and in the cell.
Advantage of Upregulation of Succinate Dehydrogenase in
Staphylococcus aureus
Biofilms
Authors: Gaupp Rosmarie , Schlag Steffen , Liebeke Manuel , Lalk Michael , Götz Friedrich
Published: March 2010

Previous studies have demonstrated that various tricarboxylic acid (TCA) cycle genes, particularly the succinate dehydrogenase genes (
sdhCAB
), are upregulated in
Staphylococcus aureus
biofilms. To better study the role of this enzyme complex, an
sdhCAB
deletion mutant (Δ
sdh
) was constructed. Compared to the wild type (wt) the mutant was impaired in planktonic growth under aerobic conditions, excreted acetic acid could not be reused and accumulated continuously, succinate was excreted and found in the culture supernatant, and metabolome analysis with cells grown in chemically defined medium revealed reduced uptake/metabolism of some amino acids from the growth medium. Moreover, the mutant was able to counteract the steadily decreasing extracellular pH by increased urease activity. The addition of fumarate to the growth medium restored the wt phenotype. The mutant showed a small-colony variant (SCV)-like phenotype, a slight increase in resistance to various aminoglycoside antibiotics, and decreased pigmentation. The decreased growth under aerobic conditions is due to the interruption of the TCA cycle (indicated by the accumulation of succinate and acetic acid) with the consequence that many fewer reduction equivalents (NADH and FADH
2
) can fuel the respiratory chain. The results indicate that the TCA cycle is required for acetate and amino acid catabolism; its upregulation under biofilm conditions is advantageous under such nutrient- and oxygen-limited conditions.
Regulation of
pga
Operon Expression and Biofilm Formation in
Actinobacillus pleuropneumoniae
by σ
E
and H-NS
Authors: Bossé Janine T. , Sinha Sunita , Li Ming-Shi , O'Dwyer Clíona A. , Nash John H. E. , Rycroft Andrew N. , Kroll J. Simon , Langford Paul R.
Published: March 2010

Clinical isolates of the porcine pathogen
Actinobacillus pleuropneumoniae
often form adherent colonies on agar plates due to expression of an operon,
pgaABCD
, encoding a poly-β-1,6-
N
-acetyl-
d
-glucosamine (PGA) extracellular matrix. The adherent colony phenotype, which correlates with the ability to form biofilms on the surfaces of polystyrene plates, is lost following serial passage in broth culture, and repeated passage of the nonadherent variants on solid media does not result in reversion to the adherent colony phenotype. In order to investigate the regulation of PGA expression and biofilm formation in
A. pleuropneumoniae
, we screened a bank of transposon mutants of the nonadherent serovar 1 strain S4074
T
and identified mutations in two genes,
rseA
and
hns
, which resulted in the formation of the adherent colony phenotype. In other bacteria, including the
Enterobacteriaceae
, H-NS acts as a global gene regulator, and RseA is a negative regulator of the extracytoplasmic stress response sigma factor σ
E
. Transcription profiling of
A. pleuropneumoniae rseA
and
hns
mutants revealed that both σ
E
and H-NS independently regulate expression of the
pga
operon. Transcription of the
pga
operon is initiated from a σ
E
promoter site in the absence of H-NS, and upregulation of σ
E
is sufficient to displace H-NS, allowing transcription to proceed. In
A. pleuropneumoniae
, H-NS does not act as a global gene regulator but rather specifically regulates biofilm formation via repression of the
pga
operon. Positive regulation of the
pga
operon by σ
E
indicates that biofilm formation is part of the extracytoplasmic stress response in
A. pleuropneumoniae
.
Physiological and Transcriptional Response ofLactobacillus caseiATCC 334 to Acid Stress
Authors: Broadbent Jeff R. , Larsen Rebecca L. , Deibel Virginia , Steele James L.
Published: March 2010

This study investigated features of the acid tolerance response (ATR) inLactobacillus caseiATCC 334. To optimize ATR induction, cells were acid adapted for 10 or 20 min at different pH values (range, 3.0 to 5.0) and then acid challenged at pH 2.0. Adaptation over a broad range of pHs improved acid tolerance, but the highest survival was noted in cells acid adapted for 10 or 20 min at pH 4.5. Analysis of cytoplasmic membrane fatty acids (CMFAs) in acid-adapted cells showed that they had significantly (P< 0.05) higher total percentages of saturated and cyclopropane fatty acids than did control cells. Specifically, large increases in the percentages of C14:0, C16:1n(9), C16:0, and C19:0(11c)were noted in the CMFAs of acid-adapted and acid-adapted, acid-challenged cells, while C18:1n(9)and C18:1n(11)showed the greatest decrease. Comparison of the transcriptome from control cells (grown at pH 6.0) against that from cells acid adapted for 20 min at pH 4.5 indicated that acid adaption invoked a stringent-type response that was accompanied by other functions which likely helped these cells resist acid damage, including malolactic fermentation and intracellular accumulation of His. Validation of microarray data was provided by experiments that showed thatL. caseisurvival at pH 2.5 was improved at least 100-fold by chemical induction of the stringent response or by the addition of 30 mM malate or 30 mM histidine to the acid challenge medium. To our knowledge, this is the first report that intracellular histidine accumulation may be involved in bacterial acid resistance.
Sex rights for the disabled?
Authors: Appel Jacob M
Published: March 2010

The public discourse surrounding sex and severe disability over the past 40 years has largely focused on protecting vulnerable populations from abuse. However, health professionals and activists are increasingly recognising the inherent sexuality of disabled persons and attempting to find ways to accommodate their intimacy needs. This essay explores several ethical issues arising from such efforts.
Peripheral ophthalmic artery aneurysm associated with multiple intracranial aneurysms: a case report
Authors: Pandey Paritosh , Rayes Mahmoud , Guthikonda Murali , Xavier Andrew
Published: March 2010

Peripheral intraorbital ophthalmic artery aneurysms are rare. We here present a case of intraorbital ophthalmic artery aneurysm, associated with multiple anterior circulation aneurysms. The asymptomatic ophthalmic artery aneurysm was not treated. However, the symptomatic ones were embolized.
Transvenous embolization of a ruptured cerebral arteriovenous malformation with en-passage arterial supply: initial case report
Authors: Nguyen Thanh N , Chin Lawrence S , Souza Rosemary , Norbash Alexander M
Published: March 2010

A patient with a ruptured left sylvian fissure arteriovenous malformation (AVM) treated with primary transvenous Onyx embolization, and angiographically cured, is reported. The patient presented with a large intraparenchymal subopercular hematoma and there was angiographic demonstration of a pseudoaneurysm and single draining vein. Trans-arterial approaches were unsuccessful because of the en-passage nature of feeding arteries and hence a transvenous approach was used to embolize the pseudoaneurysm with Onyx. Follow-up angiography at 1 month revealed durable angiographic cure of the AVM. Our case illustrates that in patients with ruptured AVM secondary to pseudoaneurysm and single draining vein, transvenous treatment can be utilized to achieve occlusion of the pseudoaneurysm resulting in AVM cure. To our knowledge, this is the first description of a transvenous approach for endovascular therapy of AVM.
Mechanical thrombectomy with the penumbra system for treatment of venous sinus thrombosis
Authors: Choulakian Armen , Alexander Michael J
Published: March 2010

Objective

Venous sinus thrombosis can be a fatal condition. When systemic anticoagulation therapy fails or is high risk, endovascular chemical thrombolysis or mechanical thrombectomy may be necessary. We report our experience using the Penumbra system (PS; Penumbra, Alameda, California, USA) in a series of four patients with venous sinus thrombosis.

Methods

Four patients were treated with mechanical thrombectomy using the PS for venous sinus thrombosis. Three of these patients also underwent balloon angioplasty following the PS device. Utility of this technique was evaluated by procedural success, improvement in neurological condition, avoidance of complications and follow-up imaging.

Results

Technical success was achieved in all four patients with restoration of flow in the occluded sinuses without the use of chemical thrombolysis. No complications were encountered during the procedure and no postprocedural complications were attributable to the thrombectomy. One patient with glioblastoma died 6 weeks after the procedure. No new intracerebral hemorrhages were caused and there was no exacerbation of pretreatment intracerebral hemorrhages. Follow-up imaging was available in all but one patient to documented continued sinus patency. Neurologic improvement was seen in all patients after thrombectomy. Two patients have returned for outpatient follow-up and both are doing well.

Conclusion

Endovascular treatment for venous sinus thrombosis with the PS is a safe and efficacious alternative to the other forms of mechanical thrombectomy reported in the literature. Good clinical and radiographic results can be obtained without the need for chemical thrombolysis.
Congenital absence of the common carotid artery in a patient with a ruptured anterior communicating artery aneurysm
Authors: Drazin Doniel , Choulakian Armen , Alexander Michael J
Published: March 2010

In a 41-year-old woman with a ruptured anterior communicating artery aneurysm, cerebral angiography incidentally showed an absence of the right common carotid artery. The right internal and external carotid artery originated from the ipsilateral inominate artery. The absence of the common carotid artery is extremely rare and association with a ruptured cerebral aneurysm is even less common. A description of the case and review of the literature are reported.
A critical reappraisal of “preconsolidation pressure” interpretations using the oedometer test
Authors: Boone Storer J.
Published: March 2010

Over the past 70 years, a number of methods have been proposed for the interpretation of the characteristic vertical effective yield stress, or “preconsolidation pressure,” of compressible soils as defined using the standard oedometer test. The concept of the “preconsolidation pressure” has been extraordinarily useful in geotechnical engineering for analysing and predicting settlement behaviour and for normalizing other engineering parameters for comparative purposes. Defining this characteristic stress, however, is often problematic and relies heavily on graphical techniques that are subject to some uncertainty, particularly when using semi-log plots for this purpose. This paper illustrates fundamental difficulties with the interpretation of oedometer test and presents an alternative technique for defining unambiguous values of the vertical effective yield stress.
Arching effect in fine sand due to base yielding
Authors: Sadrekarimi Jamshid , Abbasnejad Alireza
Published: March 2010

This paper presents results of an experimental work on the arching effect in loose and dense sand. The apparatus comprises concentric circular trapdoors with different diameters that can yield downward while stresses and deformations are recorded simultaneously. As the trapdoor starts to yield, the whole mass of soil deforms elastically. However, after a specified displacement that depends on the trapdoor diameter and soil relative density, the soil mass behaves plastically. This behavior, which is due to flow phenomenon, continues until the stress applied onto the trapdoor decreases to a minimum value. Then the stress carried by the trapdoor shows an ascending trend. This indicates the gradual separation of the yielding mass from the whole soil body. Finally, the flow process creates a stable arch of sand. This process is called the arching mechanism. Depending on the trapdoor diameter, there is a critical relative density at and beyond which the test leads to the formation of a stable arch. The results are also compared with Terzaghi’s theory and the assumption of an upper boundary solution is discussed.
SUPERCONDUCTING PROPERTIES OF Y1-xTbxBa2Cu3O7-δ AND Y1-xTbxSr2Cu2.7Mo0.3O7-δ
Authors: MIRSHAMSI S. , FALLAHI S. , AKHAVAN M.
Published: March 2010

We have investigated the effect of Tb substitution for Y in both YBa 2 Cu 3 O 7-δ and the more stabilized YSr 2 Cu 2.7 Mo 0.3 O 7-δ systems. Adding Mo has been shown to stabilize the Tb -doped systems. The samples of Y 1-x Tb x Ba 2 Cu 3 O 7-δ with x=0.0, 0.1, 0.15, 0.2, 0.3, 0.35, 0.4, 0.5, 0.55, and 0.6, and of Y 1-x Tb x Sr 2 Cu 2.7 Mo 0.3 O 7-δ with x=0.0, 0.2, 0.4, 0.6, and 0.8 have been prepared by the standard solid-state reaction technique. The superconducting transition occurs only with x=0–0.5 for the Ba -based samples, and with x=0–0.8 for the Sr -based samples. The structural parameter identification and phase determination of the samples have been carried out by the Rietveld analysis of the X-ray diffraction patterns, which indicates that Tb does not enter in the structure of the Ba -based 123 phase, while in the Sr -based 123 structure Tb enters in the structure and substitutes for Y . In the Y 1-x Tb x Ba 2 Cu 3 O 7-δ samples, a new secondary TbBaO 3 phase forms; and by increasing the amount of Tb , the secondary phase increases as the Y 123 phase decreases. But, for the Y 1-x Tb x Sr 2 Cu 2.7 Mo 0.3 O 7-δ samples, by increasing the amount of Tb doping, no impurity phase is detected in the XRD patterns. For both groups of samples, by increasing the amount of Tb , the normal resistivity increases, and the metallic behavior of the resistivity changes to semiconducting behavior. The magnetoresistance of Y 1-x Tb x Ba 2 Cu 3 O 7-δ was measured in different magnetic fields. The width of transition for the same values of magnetic field increases with the increase of Tb doping, indicating that with the increase of Tb , grains link weaker due to the increase in the amount of the secondary TbBaO 3 phase. The pinning energy has also been evaluated based on the thermally activated phase creep model.
CONTROLLED AND REMOTE IMPLEMENTATION OF A SPLIT QUANTUM ROTATION AND SENDER-ENCODED SECRET SHARING
Authors: CHEN LIBING , LIU YUHUA , LU HONG
Published: March 2010

A quantum rotation can be divided into M pieces and teleported from a sender onto M distant receivers via the control of N agents in a quantum network. We utilize the entanglement property of a (2M + N + 1)-qubit Einstein–Podolsky–Rosen (EPR) — Greenberger–Horne–Zeilinger (GHZ) state to design a theoretical scheme for implementing these rotations remotely with unit fidelity and unit probability. The feature of the scheme is that, apart from a sender and M receivers, N agents are included in the process as controllers. Should any one of the N agents not cooperate, the receivers could not gain the original rotations. This scheme can be used to sender-encoded quantum secret sharing. It definitely has the strong security.
ELECTRICAL-MAGNETIC TRANSPORT AND MAGNETORESISTANCE IN La0.7Ca0.3MnO3/Bi2O3 COMPOSITES
Authors: ZHU Y. D. , LI X. A. , LIAO H. H. , SUN L. J. , XIONG C. S. , XIONG Y. H.
Published: March 2010

The structure and electrical-magnetic transport properties of ( La 0.7 Ca 0.3 MnO 3)1-x/( Bi 2 O 3)x has been investigated systematically by conventional solid-state reaction method. The composite samples were obtained by pure La 0.7 Ca 0.3 MnO 3 (LCMO) and Bi 2 O 3 powders and sintered at different temperature (Ts) 800°C and 1300°C for 2 h. For Ts=800°C samples, the results of X-ray diffraction (XRD) and scanning electronic microscopy (SEM) indicate that Bi 2 O 3 and LCMO coexist in the composites and Bi 2 O 3 mainly segregates at the grain boundaries or grain surface of LCMO, and double peaks related to the metal-to-insulator (M–I) transition have been observed. Corresponding to the two M–I transition peaks, the curves of magnetoresistance (MR) against temperature also showed two peaks for all composites. But for Ts = 1300°C samples, Bi 3+ ions mainly enter into the lattice of LCMO to form reaction products layer La 0.7-x Bi x Ca 0.3 MnO 3, only one peak occurs around the M–I transition temperature and the MR around T P has been enhanced. The results also indicate that the added Bi 2 O 3 has an important effect on the LFMR. These phenomena can be explained by the double exchange (DE) mechanism, the grain boundary effect and the intrinsic transport properties together. And the grain surface state of the particles is a key factor influencing the magnetoresistance effects.
PRE-STABILIZATION AND CRYSTALLIZATION OF AMORPHOUS SiCN MATRIX OF C/SiCN COMPOSITE UNDER VACUUM AND TENSILE CREEP STRESS
Authors: XIA YI , QIAO SHENG-RU , WANG QIANG-QIANG , ZHANG CHENG-YU
Published: March 2010

Crystallization of amorphous SiCN matrix of carbon fiber reinforced SiCN matrix composite ( C / SiCN ) under vacuum and tensile creep stress was investigated. The phase and microstructure evolution of amorphous SiCN matrix were examined by X-ray diffraction and transmission electron microscopy, respectively. The crystallization behavior of the as-received and 1900°C-annealed C / SiCN during tensile creep test conducted at 1500°C was analyzed. The results indicate that crystallization takes place after annealing at 1900°C for 0.5 h, and the phases formed are β- SiC and α- SiC . Decomposition of amorphous SiCN produces gaseous species such as SiO and CO , and vapor reaction between them and carbon induces SiC nucleation. Local atomic ( Si -, C -, N -) rearrangement due to SiCN degradation also yields a large number of Si - C -enriched regions which gradually induces SiC nucleation. The annealing treatment of C / SiCN shows stabilization effect to some extent on the SiCN matrix, but is not sufficient to get a thorough stable phase.
THE EFFECT OF DIFFERENT DZYALOSHINSKII–MORIYA INTERACTIONS ON TELEPORTATION VIA A TWO-QUBIT HEISENBERG CHAIN
Authors: CHEN TAO , SHAN CHUAN-JIA , HUANG YAN-XIA , LIU TANG-KUN , LI JIN-XING
Published: March 2010

Thermal entanglement of a two-qubit Heisenberg XXZ chain in the presence of different Dzyaloshinskii–Moriya (DM) anisotropic antisymmetric interactions and entanglement teleportation using two independent Heisenberg chains as quantum channel are investigated. It is found that the anisotropic coupling coefficient Jz (z-component exchange constant) and DM interactions can excite the entanglement, and x-component DM interaction Dx has a more remarkable influence than the z-axis DM interaction Dz for exchange constant J > 0 (antiferromagnetic) case, which is contrary to coupling coefficient J < 0 (ferromagnetic) case. The output entanglement and fidelity increase with increasing z-axis coupling parameter Jz for both the antiferromagnetic J > 0 case and ferromagnetic J < 0 case. By introducing the different DM interactions, it is superior to teleportate initial state by using the Dz interaction in the model for J > 0 case. But for J < 0 case, the Dx interaction is better, and the output concurrence and fidelity can reach the maximum value 1 with suitable Dx.
ENHANCED PHOTOLUMINESCENCE OF Sm3+/Bi3+ CO-DOPED La2O3 NANOPHOSPHORS BY COMBUSTION SYNTHESIS
Authors: ZHANG YING , WU MUYING , ZHANG W. F.
Published: March 2010

Nanosized La 2 O 3: Sm 3+ and La 2 O 3: Sm 3+, Bi 3+ phosphor powders were prepared via combustion synthesis. The structures and morphology were examined using powder X-ray diffraction and transmission electron microscope, respectively. The photoluminescence spectra were investigated at different doping concentrations of Sm 3+ and Bi 3+ ions. The results indicate that La 2 O 3: Sm 3+ ( Bi 3+) exhibited good crystallinity and spherical-like particles. All phosphors give emission bands centered at 564, 608 and 650 nm corresponding to 4 G 5/2→6 H J ( J =5/2, 7/2 and 9/2) transitions of Sm 3+ ions, respectively. Interestingly, the emission intensity of Sm 3+ ions is significantly enhanced with the addition of Bi 3+ ions to La 2 O 3: Sm 3+ and the maximum occurs at a Bi 3+ concentration of 0.8 mol%. The La 2 O 3: Sm 3+, Bi 3+ phosphor with highly enhanced luminescence is very encouraging for applications in display and tunable solid lasers.