bluuebunny/crossref_metadata_2025_split huggingface dataset:
Inactivation and UV Disinfection of Murine Norovirus with TiO
2
under Various Environmental Conditions
Authors: Lee JungEun , Zoh KyungDuk , Ko GwangPyo 
Published: February 2008

ABSTRACT

We studied inactivation and UV disinfection of murine norovirus (MNV) as a surrogate for human norovirus. We investigated the effects of different surface characteristics, temperatures, and NaCl concentrations on MNV survival using both a plaque assay and a real-time TaqMan reverse transcription (RT)-PCR assay. MNV survived more than 40 days on diaper material, on gauze, and in a stool suspension. Compared to inactivation at lower temperatures (−20 and 4°C), inactivation of MNV was greater at higher temperatures (18 and 30°C). On the surface of both gauze and diaper material, there was a <2-log
10
reduction in the amount of infectious MNV in 40 days after incubation at both −20 and 4°C, compared to a >5-log
10
reduction after incubation at 30°C in 24 days. MNV survived better in a stool suspension than on the surface of gauze or diaper material. A higher salt concentration increased the rate of inactivation of MNV. In 72 h, <0.3-, 1.5-, and 2.5-log
10
reductions in the amount of infectious MNV occurred in distilled water and 0.5 and 1 M NaCl, respectively. We observed only minor reductions in the numbers of viral RNA copies as quantified by real-time TaqMan RT-PCR regardless of the temperature, the salt concentration, or the suspending medium. We also evaluated UV disinfection of infectious MNV with and without TiO
2
. The amount of MNV was significantly reduced by 254-nm UV with and without TiO
2
. When 25 mJ/cm
2
UV was used, 3.3- and 3.6-log
10
reductions in the amounts of infectious MNV occurred with and without TiO
2
, respectively. Our results demonstrate that MNV can persist in various environmental conditions and can be efficiently controlled by UV disinfection.
Use of In Vivo
13
C Nuclear Magnetic Resonance Spectroscopy To Elucidate
l
-Arabinose Metabolism in Yeasts
Authors: Fonseca César , Neves Ana Rute , Antunes Alexandra M. M. , Noronha João Paulo , Hahn-Hägerdal Bärbel , Santos Helena , Spencer-Martins Isabel 
Published: February 2008

ABSTRACT

Candida arabinofermentans
PYCC 5603
T
and
Pichia guilliermondii
PYCC 3012 were shown to grow well on
l
-arabinose, albeit exhibiting distinct features that justify an in-depth comparative study of their respective pentose catabolism. Carbon-13 labeling experiments coupled with in vivo nuclear magnetic resonance (NMR) spectroscopy were used to investigate
l
-arabinose metabolism in these yeasts, thereby complementing recently reported physiological and enzymatic data. The label supplied in
l
-[2-
13
C]arabinose to nongrowing cells, under aerobic conditions, was found on C-1 and C-2 of arabitol and ribitol, on C-2 of xylitol, and on C-1, C-2, and C-3 of trehalose. The detection of labeled arabitol and xylitol constitutes additional evidence for the operation in yeast of the redox catabolic pathway, which is widespread among filamentous fungi. Furthermore, labeling at position C-1 of trehalose and arabitol demonstrates that glucose-6-phosphate is recycled through the oxidative pentose phosphate pathway (PPP). This result was interpreted as a metabolic strategy to regenerate NADPH, the cofactor essential for sustaining
l
-arabinose catabolism at the level of
l
-arabinose reductase and
l
-xylulose reductase. Moreover, the observed synthesis of
d
-arabitol and ribitol provides a route with which to supply NAD
+
under oxygen-limiting conditions. In
P. guilliermondii
PYCC 3012, the strong accumulation of
l
-arabitol (intracellular concentration of up to 0.4 M) during aerobic
l
-arabinose metabolism indicates the existence of a bottleneck at the level of
l
-arabitol 4-dehydrogenase. This report provides the first experimental evidence for a link between
l
-arabinose metabolism in fungi and the oxidative branch of the PPP and suggests rational guidelines for the design of strategies for the production of new and efficient
l
-arabinose-fermenting yeasts.
Cinnamic Acid, an Autoinducer of Its Own Biosynthesis, Is Processed via Hca Enzymes in
Photorhabdus luminescens
Authors: Chalabaev Sabina , Turlin Evelyne , Bay Sylvie , Ganneau Christelle , Brito-Fravallo Emma , Charles Jean-François , Danchin Antoine , Biville Francis 
Published: February 2008

ABSTRACT

Photorhabdus luminescens
, an entomopathogenic bacterium and nematode symbiont, has homologues of the Hca and Mhp enzymes. In
Escherichia coli
, these enzymes catalyze the degradation of the aromatic compounds 3-phenylpropionate (3PP) and cinnamic acid (CA) and allow the use of 3PP as sole carbon source.
P. luminescens
is not able to use 3PP and CA as sole carbon sources but can degrade them. Hca dioxygenase is involved in this degradation pathway.
P. luminescens
synthesizes CA from phenylalanine via a phenylalanine ammonia-lyase (PAL) and degrades it via the not-yet-characterized biosynthetic pathway of 3,5-dihydroxy-4-isopropylstilbene (ST) antibiotic. CA induces its own synthesis by enhancing the expression of the
stlA
gene that codes for PAL.
P. luminescens
bacteria release endogenous CA into the medium at the end of exponential growth and then consume it. Hca dioxygenase is involved in the consumption of endogenous CA but is not required for ST production. This suggests that CA is consumed via at least two separate pathways in
P. luminescens
: the biosynthesis of ST and a pathway involving the Hca and Mhp enzymes.
Molecular Analysis of Shiga Toxin-Producing
Escherichia coli
Strains Isolated from Hemolytic-Uremic Syndrome Patients and Dairy Samples in France
Authors: Pradel Nathalie , Bertin Yolande , Martin Christine , Livrelli Valérie 
Published: February 2008

ABSTRACT

Shiga toxin-producing
Escherichia coli
(STEC) has been associated with food-borne diseases ranging from uncomplicated diarrhea to hemolytic-uremic syndrome (HUS). While most outbreaks are associated with
E. coli
O157:H7, about half of the sporadic cases may be due to non-O157:H7 serotypes. To assess the pathogenicity of STEC isolated from dairy foods in France, 40 strains isolated from 1,130 raw-milk and cheese samples were compared with 15 STEC strains isolated from patients suffering from severe disease. The presence of genes encoding Shiga toxins (
stx
1
,
stx
2
, and variants), intimin (
eae
and variants), adhesins (
bfp
,
efa1
), enterohemolysin (
ehxA
), serine protease (
espP
), and catalase-peroxidase (
katP
) was determined by PCR and/or hybridization. Plasmid profiling, ribotyping, and pulsed-field gel electrophoresis (PFGE) were used to further compare the strains at the molecular level. A new
stx
2
variant,
stx
2-CH013
, associated with an O91:H10 clinical isolate was identified. The presence of the
stx
2
,
eae
, and
katP
genes, together with a combination of several
stx
2
variants, was clearly associated with human-pathogenic strains. In contrast, dairy food STEC strains were characterized by a predominance of
stx
1
, with a minority of isolates harboring
eae
,
espP
, and/or
katP
. These associations may help to differentiate less virulent STEC strains from those more likely to cause disease in humans. Only one dairy O5 isolate had a virulence gene panel identical to that of an HUS-associated strain. However, the ribotype and PFGE profiles were not identical. In conclusion, most STEC strains isolated from dairy products in France showed characteristics different from those of strains isolated from patients.
Human
Salmonella
Clinical Isolates Distinct from Those of Animal Origin
Authors: Heithoff Douglas M. , Shimp William R. , Lau Patrick W. , Badie Golnaz , Enioutina Elena Y. , Daynes Raymond A. , Byrne Barbara A. , House John K. , Mahan Michael J. 
Published: February 2008

ABSTRACT

The global trend toward intensive livestock production has led to significant public health risks and industry-associated losses due to an increased incidence of disease and contamination of livestock-derived food products. A potential factor contributing to these health concerns is the prospect that selective pressure within a particular host may give rise to bacterial strain variants that exhibit enhanced fitness in the present host relative to that in the parental host from which the strain was derived. Here, we assessed 184
Salmonella enterica
human and animal clinical isolates for their virulence capacities in mice and for the presence of the
Salmonella
virulence plasmid encoding the SpvB actin cytotoxin required for systemic survival and Pef fimbriae, implicated in adherence to the murine intestinal epithelium. All (21 of 21) serovar Typhimurium clinical isolates derived from animals were virulent in mice, whereas many (16 of 41) serovar Typhimurium isolates derived from human salmonellosis patients lacked this capacity. Additionally, many (10 of 29) serovar Typhimurium isolates derived from gastroenteritis patients did not possess the
Salmonella
virulence plasmid, in contrast to all animal and human bacteremia isolates tested. Lastly, among serovar Typhimurium isolates that harbored the
Salmonella
virulence plasmid, 6 of 31 derived from human salmonellosis patients were avirulent in mice, which is in contrast to the virulent phenotype exhibited by all the animal isolates examined. These studies suggest that
Salmonella
isolates derived from human salmonellosis patients are distinct from those of animal origin. The characterization of these bacterial strain variants may provide insight into their relative pathogenicities as well as into the development of treatment and prophylactic strategies for salmonellosis.
Bot1p Is Required for Mitochondrial Translation, Respiratory Function, and Normal Cell Morphology in the Fission Yeast
Schizosaccharomyces pombe
Authors: Wiley David J. , Catanuto Paola , Fontanesi Flavia , Rios Carmen , Sanchez Natalie , Barrientos Antoni , Verde Fulvia 
Published: February 2008

ABSTRACT

Maintenance of cell morphology is essential for normal cell function. For eukaryotic cells, a growing body of recent evidence highlights a close interdependence between mitochondrial function, the cytoskeleton, and cell cycle control mechanisms; however, the molecular details of this interconnection are still not completely understood. We have identified a novel protein, Bot1p, in the fission yeast
Schizosaccharomyces pomb
e. The
bot1
gene is essential for cell viability.
bot1Δ
mutant cells expressing lower levels of Bot1p display altered cell size and cell morphology and a disrupted actin cytoskeleton. Bot1p localizes to the mitochondria in live cells and cofractionates with purified mitochondrial ribosomes. Reduced levels of Bot1p lead to mitochondrial fragmentation, decreased mitochondrial protein translation, and a corresponding decrease in cell respiration. Overexpression of Bot1p results in cell cycle delay, with increased cell size and cell length and enhanced cell respiration rate. Our results show that Bot1p has a novel function in the control of cell respiration by acting on the mitochondrial protein synthesis machinery. Our observations also indicate that in fission yeast, alterations of mitochondrial function are linked to changes in cell cycle and cell morphology control mechanisms.
Investigation of Regulation of FtsZ Assembly by SulA and Development of a Model for FtsZ Polymerization
Authors: Dajkovic Alex , Mukherjee Amit , Lutkenhaus Joe 
Published: February 2008

ABSTRACTInEscherichia coliFtsZ organizes into a cytoskeletal ring structure, the Z ring, which effects cell division. FtsZ is a GTPase, but the free energy of GTP hydrolysis does not appear to be used for generation of the constriction force, leaving open the question of the function of the GTPase activity of FtsZ. Here we study the mechanism by which SulA, an inhibitor of FtsZ induced during the SOS response, inhibits FtsZ function. We studied the effects of SulA on the in vitro activities of FtsZ, on Z rings in vivo, and on a kinetic model for FtsZ polymerization in silico. We found that the binding of SulA to FtsZ is necessary but not sufficient for inhibition of polymerization, since the assembly of FtsZ polymers in the absence of the GTPase activity was not inhibited by SulA. We developed a new model for FtsZ polymerization that accounts for the cooperativity of FtsZ and could account for cooperativity observed in other linear polymers. When SulA was included in the kinetic scheme, simulations revealed that SulA with strong affinity for FtsZ delayed, but did not prevent, the assembly of polymers when they were not hydrolyzing GTP. Furthermore, the simulations indicated that SulA controls the assembly of FtsZ by binding to a polymerization-competent form of the FtsZ molecule and preventing it from participating in assembly. In vivo stoichiometry of the disruption of Z rings by SulA suggests that FtsZ may undergo two cooperative transitions in forming the Z ring.
Swarming ofPseudomonas aeruginosaIs a Complex Adaptation Leading to Increased Production of Virulence Factors and Antibiotic Resistance
Authors: Overhage Joerg , Bains Manjeet , Brazas Michelle D. , Hancock Robert E. W. 
Published: February 2008

ABSTRACTIn addition to exhibiting swimming and twitching motility,Pseudomonas aeruginosais able to swarm on semisolid (viscous) surfaces. Recent studies have indicated that swarming is a more complex type of motility influenced by a large number of different genes. To investigate the adaptation process involved in swarming motility, gene expression profiles were analyzed by performing microarrays on bacteria from the leading edge of a swarm zone compared to bacteria growing in identical medium under swimming conditions. Major shifts in gene expression patterns were observed under swarming conditions, including, among others, the overexpression of a large number of virulence-related genes such as those encoding the type III secretion system and its effectors, those encoding extracellular proteases, and those associated with iron transport. In addition, swarming cells exhibited adaptive antibiotic resistance against polymyxin B, gentamicin, and ciprofloxacin compared to what was seen for their planktonic (swimming) counterparts. By analyzing a large subset of up-regulated genes, we were able to show that two virulence genes,lasBandpvdQ, were required for swarming motility. These results clearly favored the conclusion that swarming ofP. aeruginosais a complex adaptation process in response to a viscous environment resulting in a substantial change in virulence gene expression and antibiotic resistance.
Mycobacterium aviumsubsp.paratuberculosisandM. aviumsubsp.aviumAre Independently Evolved Pathogenic Clones of a Much Broader Group ofM. aviumOrganisms
Authors: Turenne Christine Y. , Collins Desmond M. , Alexander David C. , Behr Marcel A. 
Published: February 2008

ABSTRACTMycobacterium aviumcomprises organisms that share the same species designation despite considerable genomic and phenotypic variability. To determine the degree and nature of variability between subspecies and strains ofM. avium, we used multilocus sequencing analysis, studying 56 genetically diverse strains ofM. aviumthat included all described subspecies. In total, 8,064 bp of sequence from 10 gene loci were studied, with 205 (2.5%) representing variable positions. The majority (149/205) of these variations were found amongM. aviumsubsp.hominissuisorganisms. Recombination was also evident in this subspecies. In contrast, there was comparatively little variability and no evidence of recombination within the pathogenic subspecies,M. aviumsubsp.paratuberculosis,M. aviumsubsp.avium, andM. aviumsubsp.silvaticum.Phylogenetic analysis showed thatM. aviumsubsp.aviumandM. aviumsubsp.silvaticumstrains clustered together on one branch, while a distinct branch definedM. aviumsubsp.paratuberculosisorganisms. Despite the independent origin of these pathogenic subspecies, an analysis of their rates of nonsynonymous (dN) to synonymous (dS) substitutions showed increased dN/dS ratios for both: 0.67 forM. aviumsubsp.paratuberculosisand 0.50 forM. aviumsubsp.avium/M. aviumsubsp.silvaticum, while the value was 0.08 forM. aviumsubsp.hominissuisorganisms. In conclusion,M. aviumsubsp.hominissuisrepresents a diverse group of organisms from which two pathogenic clones (M. aviumsubsp.paratuberculosisandM. aviumsubsp.avium/M. aviumsubsp.silvaticum) have evolved independently.
A Set of Activators and Repressors Control Peripheral Glucose Pathways in
Pseudomonas putida
To Yield a Common Central Intermediate
Authors: del Castillo Teresa , Duque Estrella , Ramos Juan L. 
Published: February 2008

ABSTRACT

Pseudomonas putida
KT2440 channels glucose to the central Entner-Doudoroff intermediate 6-phosphogluconate through three convergent pathways. The genes for these convergent pathways are clustered in three independent regions on the host chromosome. A number of monocistronic units and operons coexist within each of these clusters, favoring coexpression of catabolic enzymes and transport systems. Expression of the three pathways is mediated by three transcriptional repressors, HexR, GnuR, and PtxS, and by a positive transcriptional regulator, GltR-2. In this study, we generated mutants in each of the regulators and carried out transcriptional assays using microarrays and transcriptional fusions. These studies revealed that HexR controls the genes that encode glucokinase/glucose 6-phosphate dehydrogenase that yield 6-phosphogluconate; the genes for the Entner-Doudoroff enzymes that yield glyceraldehyde-3-phosphate and pyruvate; and
gap-1
, which encodes glyceraldehyde-3-phosphate dehydrogenase. GltR-2 is the transcriptional regulator that controls specific porins for the entry of glucose into the periplasmic space, as well as the
gtsABCD
operon for glucose transport through the inner membrane. GnuR is the repressor of gluconate transport and gluconokinase responsible for the conversion of gluconate into 6-phosphogluconate. PtxS, however, controls the enzymes for oxidation of gluconate to 2-ketogluconate, its transport and metabolism, and a set of genes unrelated to glucose metabolism.
Bile Salts and Glycine as Cogerminants for
Clostridium difficile
Spores
Authors: Sorg Joseph A. , Sonenshein Abraham L. 
Published: February 2008

ABSTRACT

Spore formation by
Clostridium difficile
is a significant obstacle to overcoming hospital-acquired
C. difficile
-associated disease. Spores are resistant to heat, radiation, chemicals, and antibiotics, making a contaminated environment difficult to clean. To cause disease, however, spores must germinate and grow out as vegetative cells. The germination of
C. difficile
spores has not been examined in detail. In an effort to understand the germination of
C. difficile
spores, we characterized the response of
C. difficile
spores to bile. We found that cholate derivatives and the amino acid glycine act as cogerminants. Deoxycholate, a metabolite of cholate produced by the normal intestinal flora, also induced germination of
C. difficile
spores but prevented the growth of vegetative
C. difficile
. A model of resistance to
C. difficile
colonization mediated by the normal bacterial flora is proposed.
A New Model of Pneumococcal Lipoteichoic Acid Structure Resolves Biochemical, Biosynthetic, and Serologic Inconsistencies of the Current Model
Authors: Seo Ho Seong , Cartee Robert T. , Pritchard David G. , Nahm Moon H. 
Published: February 2008

ABSTRACT

Lipoteichoic acid (LTA) is an essential bacterial membrane polysaccharide (cell wall component) that is attached to the membrane via a lipid anchor. According to the currently accepted structure of pneumococcal LTA, the polysaccharide is comprised of several repeating units, each of which starts with glucose and ends with ribitol, with the lipid anchor predicted to be Glc(β1→3)AATGal(β1→3)Glc(α1→3)-acyl
2
Gro, where AATGal is 2-acetamido-4-amino-2,4,6-trideoxy-
d
-galactose. However, this lipid anchor has not been detected in pneumococcal membranes. Furthermore, the currently accepted structure does not explain the Forssman antigen properties of LTA and predicts a molecular weight for LTA that is larger than its actual observed molecular weight. To resolve these problems, we used mass spectrometry to analyze the structure of LTA isolated from several pneumococcal strains. Our study found that the R36A pneumococcal strain produces LTA that is more representative of pneumococci than that previously characterized from the R6 strain. Analysis of LTA fragments obtained after hydrofluoric acid and nitrous treatments showed that the fragments were consistent with an LTA nonreducing terminus consisting of GalNAc(α1→3)GalNAc(β1→, which is the minimal structure for the Forssman antigen. Based on these data, we propose a revised model of LTA structure: its polysaccharide repeating unit begins with GalNAc and ends with AATGal, and its lipid anchor is Glc(α1→3)-acyl
2
Gro, a common lipid anchor found in pneumococcal membranes. This new model accurately predicts the observed molecular weights. The revised model should facilitate investigation of the relationship between LTA's structure and its function.
Elucidation of an Alternate Isoleucine Biosynthesis Pathway in
Geobacter sulfurreducens
Authors: Risso Carla , Van Dien Stephen J. , Orloff Amber , Lovley Derek R. , Coppi Maddalena V. 
Published: February 2008

ABSTRACT

The central metabolic model for
Geobacter sulfurreducens
included a single pathway for the biosynthesis of isoleucine that was analogous to that of
Escherichia coli
, in which the isoleucine precursor 2-oxobutanoate is generated from threonine.
13
C labeling studies performed in
G. sulfurreducens
indicated that this pathway accounted for a minor fraction of isoleucine biosynthesis and that the majority of isoleucine was instead derived from acetyl-coenzyme A and pyruvate, possibly via the citramalate pathway. Genes encoding citramalate synthase (GSU1798), which catalyzes the first dedicated step in the citramalate pathway, and threonine ammonia-lyase (GSU0486), which catalyzes the conversion of threonine to 2-oxobutanoate, were identified and knocked out. Mutants lacking both of these enzymes were auxotrophs for isoleucine, whereas single mutants were capable of growth in the absence of isoleucine. Biochemical characterization of the single mutants revealed deficiencies in citramalate synthase and threonine ammonia-lyase activity. Thus, in
G. sulfurreducens
, 2-oxobutanoate can be synthesized either from citramalate or threonine, with the former being the main pathway for isoleucine biosynthesis. The citramalate synthase of
G. sulfurreducens
constitutes the first characterized member of a phylogenetically distinct clade of citramalate synthases, which contains representatives from a wide variety of microorganisms.