bluuebunny/crossref_metadata_2025_split huggingface dataset:
Xanthomonas perforans Colonization Influences Salmonella enterica in the Tomato Phyllosphere
Authors: Potnis Neha , Soto-Arias José Pablo , Cowles Kimberly N. , van Bruggen Ariena H. C. , Jones Jeffrey B. , Barak Jeri D. 
Published: March 2014

ABSTRACT

Salmonella enterica
rarely grows on healthy, undamaged plants, but its persistence is influenced by bacterial plant pathogens. The interactions between
S. enterica
,
Xanthomonas perforans
(a tomato bacterial spot pathogen), and tomato were characterized. We observed that virulent
X. perforans
, which establishes disease by suppressing pathogen-associated molecular pattern (PAMP)-triggered immunity that leads to effector-triggered susceptibility, created a conducive environment for persistence of
S. enterica
in the tomato phyllosphere, while activation of effector-triggered immunity by avirulent
X. perforans
resulted in a dramatic reduction in
S. enterica
populations.
S. enterica
populations persisted at ∼10 times higher levels in leaves coinoculated with virulent
X. perforans
than in those where
S. enterica
was applied alone. In contrast,
S. enterica
populations were ∼5 times smaller in leaves coinoculated with avirulent
X. perforans
than in leaves inoculated with
S. enterica
alone. Coinoculation with virulent
X. perforans
increased
S. enterica
aggregate formation; however,
S. enterica
was not found in mixed aggregates with
X. perforans
. Increased aggregate formation by
S. enterica
may serve as the mechanism of persistence on leaves cocolonized by virulent
X. perforans
.
S. enterica
association with stomata was altered by
X. perforans
; however, it did not result in appreciable populations of
S. enterica
in the apoplast even in the presence of large virulent
X. perforans
populations. Gene-for-gene resistance against
X. perforans
successively restricted
S. enterica
populations. Given the effect of this interaction, breeding for disease-resistant cultivars may be an effective strategy to limit both plant disease and
S. enterica
populations and, consequently, human illness.
Determination of Thermal Inactivation Kinetics of Hepatitis A Virus in Blue Mussel (Mytilus edulis) Homogenate
Authors: Bozkurt Hayriye , D'Souza Doris H. , Davidson P. Michael 
Published: March 2014

ABSTRACT

Hepatitis A virus (HAV) is a food-borne enteric virus responsible for outbreaks of hepatitis associated with shellfish consumption. The objectives of this study were to determine the thermal inactivation behavior of HAV in blue mussels, to compare the first-order and Weibull models to describe the data, to calculate Arrhenius activation energy for each model, and to evaluate model efficiency by using selected statistical criteria. The times required to reduce the population by 1 log cycle (D-values) calculated from the first-order model (50 to 72°C) ranged from 1.07 to 54.17 min for HAV. Using the Weibull model, the times required to destroy 1 log unit (

t
D

= 1
) of HAV at the same temperatures were 1.57 to 37.91 min. At 72°C, the treatment times required to achieve a 6-log reduction were 7.49 min for the first-order model and 8.47 min for the Weibull model. The z-values (changes in temperature required for a 90% change in the log D-values) calculated for HAV were 15.88 ± 3.97°C (
R
2
, 0.94) with the Weibull model and 12.97 ± 0.59°C (
R
2
, 0.93) with the first-order model. The calculated activation energies for the first-order model and the Weibull model were 165 and 153 kJ/mol, respectively. The results revealed that the Weibull model was more appropriate for representing the thermal inactivation behavior of HAV in blue mussels. Correct understanding of the thermal inactivation behavior of HAV could allow precise determination of the thermal process conditions to prevent food-borne viral outbreaks associated with the consumption of contaminated mussels.
Bacillus thuringiensis DB27 Produces Two Novel Protoxins, Cry21Fa1 and Cry21Ha1, Which Act Synergistically against Nematodes
Authors: Iatsenko Igor , Boichenko Iuliia , Sommer Ralf J. 
Published: March 2014

ABSTRACT

Bacillus thuringiensis
has been widely used as a biopesticide, primarily for the control of insect pests, but some
B. thuringiensis
strains specifically target nematodes. However, nematicidal virulence factors of
B. thuringiensis
are poorly investigated. Here, we describe virulence factors of nematicidal
B. thuringiensis
DB27 using
Caenorhabditis elegans
as a model. We show that
B. thuringiensis
DB27 kills a number of free-living and animal-parasitic nematodes via intestinal damage. Its virulence factors are plasmid-encoded Cry protoxins, since plasmid-cured derivatives do not produce Cry proteins and are not toxic to nematodes. Whole-genome sequencing of
B. thuringiensis
DB27 revealed multiple potential nematicidal factors, including several Cry-like proteins encoded by different plasmids. Two of these proteins appear to be novel and show high similarity to Cry21Ba1. Named Cry21Fa1 and Cry21Ha1, they were expressed in
Escherichia coli
and fed to
C. elegans
, resulting in intoxication, intestinal damage, and death of nematodes. Interestingly, the effects of the two protoxins on
C. elegans
are synergistic (synergism factor, 1.8 to 2.5). Using purified proteins, we determined the 50% lethal concentrations (LC
50
s) for Cry21Fa1 and Cry21Ha1 to be 13.6 μg/ml and 23.9 μg/ml, respectively, which are comparable to the LC
50
of nematicidal Cry5B. Finally, we found that signaling pathways which protect
C. elegans
against Cry5B toxin are also required for protection against Cry21Fa1. Thus,
B. thuringiensis
DB27 produces novel nematicidal protoxins Cry21Fa1 and Cry21Ha1 with synergistic action, which highlights the importance of naturally isolated strains as a source of novel toxins.
An Uncultivated Nitrate-Reducing Member of the Genus Herminiimonas Degrades Toluene
Authors: Kim So-Jeong , Park Soo-Je , Jung Man-Young , Kim Jong-Geol , Madsen Eugene L. , Rhee Sung-Keun 
Published: March 2014

ABSTRACT

Stable isotope probing (SIP) is a cultivation-free methodology that provides information about the identity of microorganisms participating in assimilatory processes in complex communities. In this study, a
Herminiimonas
-related bacterium was identified as the dominant member of a denitrifying microcosm fed [
13
C]toluene. The genome of the uncultivated toluene-degrading bacterium was obtained by applying pyrosequencing to the heavy DNA fraction. The draft genome comprised ∼3.8 Mb, in 131 assembled contigs. Metabolic reconstruction of aromatic hydrocarbon (toluene, benzoate,
p
-cresol, 4-hydroxybenzoate, phenylacetate, and cyclohexane carboxylate) degradation indicated that the bacterium might specialize in anaerobic hydrocarbon degradation. This characteristic is novel for the order
Burkholderiales
within the class
Betaproteobacteria
. Under aerobic conditions, the benzoate oxidation gene cluster (BOX) system is likely involved in the degradation of benzoate via benzoyl coenzyme A. Many putative genes for aromatic hydrocarbon degradation were closely related to those in the
Rhodocyclaceae
(particularly
Aromatoleum aromaticum
EbN1) with respect to organization and sequence similarity. Putative mobile genetic elements associated with these catabolic genes were highly abundant, suggesting gene acquisition by
Herminiimonas
via horizontal gene transfer.
Identification of Biomarker Genes To Predict Biodegradation of 1,4-Dioxane
Authors: Gedalanga Phillip B. , Pornwongthong Peerapong , Mora Rebecca , Chiang Sheau-Yun Dora , Baldwin Brett , Ogles Dora , Mahendra Shaily 
Published: March 2014

ABSTRACT

Bacterial multicomponent monooxygenase gene targets in
Pseudonocardia dioxanivorans
CB1190 were evaluated for their use as biomarkers to identify the potential for 1,4-dioxane biodegradation in pure cultures and environmental samples. Our studies using laboratory pure cultures and industrial activated sludge samples suggest that the presence of genes associated with dioxane monooxygenase, propane monooxygenase, alcohol dehydrogenase, and aldehyde dehydrogenase are promising indicators of 1,4-dioxane biotransformation; however, gene abundance was insufficient to predict actual biodegradation. A time course gene expression analysis of dioxane and propane monooxygenases in
Pseudonocardia dioxanivorans
CB1190 and mixed communities in wastewater samples revealed important associations with the rates of 1,4-dioxane removal. In addition, transcripts of alcohol dehydrogenase and aldehyde dehydrogenase genes were upregulated during biodegradation, although only the aldehyde dehydrogenase was significantly correlated with 1,4-dioxane concentrations. Expression of the propane monooxygenase demonstrated a time-dependent relationship with 1,4-dioxane biodegradation in
P. dioxanivorans
CB1190, with increased expression occurring after over 50% of the 1,4-dioxane had been removed. While the fraction of
P. dioxanivorans
CB1190-like bacteria among the total bacterial population significantly increased with decrease in 1,4-dioxane concentrations in wastewater treatment samples undergoing active biodegradation, the abundance and expression of monooxygenase-based biomarkers were better predictors of 1,4-dioxane degradation than taxonomic 16S rRNA genes. This study illustrates that specific bacterial monooxygenase and dehydrogenase gene targets together can serve as effective biomarkers for 1,4-dioxane biodegradation in the environment.
Detection of Streptococcus suis in Bioaerosols of Swine Confinement Buildings
Authors: Bonifait Laetitia , Veillette Marc , Létourneau Valérie , Grenier Daniel , Duchaine Caroline 
Published: March 2014

ABSTRACTStreptococcus suisis an important swine pathogen that can cause septicemia, meningitis, and pneumonia. Also recognized as an emerging zoonotic agent, it is responsible for outbreaks of human infections in Asian countries. Serotype 2 is the predominant isolate from diseased animals and humans. The aerosolization ofS. suisin the air of swine confinement buildings (SCB) was studied. The presence ofS. suisin bioaerosols was monitored in SCB where cases of infection had been reported and in healthy SCB without reported infections. Using a quantitative-PCR (qPCR) method, we determined the total number of bacteria (1 × 108to 2 × 108airborne/m3), total number ofS. suisbacteria (4 × 105to 10 × 105airborne/m3), and number ofS. suisserotype 2 and 1/2 bacteria (1 × 103to 30 × 103airborne/m3) present in the air.S. suisserotypes 2 and 1/2 were detected in the air of all growing/finishing SCB that had documented cases ofS. suisinfection and in 50% of healthy SCB. The total number of bacteria and total numbers ofS. suisandS. suisserotype 2 and 1/2 bacteria were monitored in one positive SCB during a 5-week period, and it was shown that the aerosolizedS. suisserotypes 2 and 1/2 remain airborne for a prolonged period. When the effect of aerosolization onS. suiswas observed, the percentage of intactS. suisbacteria (showing cell membrane integrity) in the air might have been up to 13%. FinallyS. suiswas found in nasal swabs from 14 out of 21 healthy finishing-SCB workers, suggesting significant exposure to the pathogen. This report provides a better understanding of the aerosolization, prevalence, and persistence ofS. suisin SCB.
Sulfur Species as Redox Partners and Electron Shuttles for Ferrihydrite Reduction by Sulfurospirillum deleyianum
Authors: Lohmayer Regina , Kappler Andreas , Lösekann-Behrens Tina , Planer-Friedrich Britta 
Published: March 2014

ABSTRACT

Iron(III) (oxyhydr)oxides can represent the dominant microbial electron acceptors under anoxic conditions in many aquatic environments, which makes understanding the mechanisms and processes regulating their dissolution and transformation particularly important. In a previous laboratory-based study, it has been shown that 0.05 mM thiosulfate can reduce 6 mM ferrihydrite indirectly via enzymatic reduction of thiosulfate to sulfide by the sulfur-reducing bacterium
Sulfurospirillum deleyianum
, followed by abiotic reduction of ferrihydrite coupled to reoxidation of sulfide. Thiosulfate, elemental sulfur, and polysulfides were proposed as reoxidized sulfur species functioning as electron shuttles. However, the exact electron transfer pathway remained unknown. Here, we present a detailed analysis of the sulfur species involved. Apart from thiosulfate, substoichiometric amounts of sulfite, tetrathionate, sulfide, or polysulfides also initiated ferrihydrite reduction. The portion of thiosulfate produced during abiotic ferrihydrite-dependent reoxidation of sulfide was about 10% of the total sulfur at maximum. The main abiotic oxidation product was elemental sulfur attached to the iron mineral surface, which indicates that direct contact between microorganisms and ferrihydrite is necessary to maintain the iron reduction process. Polysulfides were not detected in the liquid phase. Minor amounts were found associated either with microorganisms or the mineral phase. The abiotic oxidation of sulfide in the reaction with ferrihydrite was identified as rate determining. Cysteine, added as a sulfur source and a reducing agent, also led to abiotic ferrihydrite reduction and therefore should be eliminated when sulfur redox reactions are investigated. Overall, we could demonstrate the large impact of intermediate sulfur species on biogeochemical iron transformations.
Requirements for Hirano Body Formation
Authors: Griffin Paul , Furukawa Ruth , Piggott Cleveland , Maselli Andrew , Fechheimer Marcus 
Published: March 2014

ABSTRACT

Hirano bodies are paracrystalline F-actin-rich structures associated with diverse conditions, including neurodegeneration and aging. Generation of model Hirano bodies using altered forms of
Dictyostelium
34-kDa actin-bundling protein allows studies of their physiological function and mechanism of formation. We describe a novel 34-kDa protein mutant, E60K, with a point mutation within the inhibitory domain of the 34-kDa protein. Expression of E60K in
Dictyostelium
induces the formation of model Hirano bodies. The E60K protein has activated actin binding and is calcium regulated, unlike other forms of the 34-kDa protein that induce Hirano bodies and that have activated actin binding but lack calcium regulation. Actin filaments in the presence of E60K
in vitro
show enhanced resistance to disassembly induced by latrunculin B. Actin filaments in model Hirano bodies are also protected from latrunculin-induced depolymerization. We used nocodazole and blebbistatin to probe the role of the microtubules and myosin II, respectively, in the formation of model Hirano bodies. In the presence of these inhibitors, model Hirano bodies can form but are smaller than controls at early times of formation. The ultrastructure of model Hirano bodies did not reveal any major difference in structure and organization in the presence of inhibitors. In summary, these results support the conclusion that formation of model Hirano bodies is promoted by gain-of-function actin filament bundling, which enhances actin filament stabilization. Microtubules and myosin II contribute to but are not required for formation of model Hirano bodies.
Sex-Specific Posttranslational Regulation of the Gamete Fusogen GCS1 in the Isogamous Volvocine Alga Gonium pectorale
Authors: Kawai-Toyooka Hiroko , Mori Toshiyuki , Hamaji Takashi , Suzuki Masahiro , Olson Bradley J. S. C. , Uemura Tomohiro , Ueda Takashi , Nakano Akihiko , Toyoda Atsushi , Fujiyama Asao , Nozaki Hisayoshi 
Published: March 2014

ABSTRACT

Male and female, generally defined based on differences in gamete size and motility, likely have multiple independent origins, appearing to have evolved from isogamous organisms in various eukaryotic lineages. Recent studies of the gamete fusogen GCS1/HAP2 indicate that this protein is deeply conserved across eukaryotes, and its exclusive and/or functional expression generally resides in males or in male homologues. However, little is known regarding the conserved or primitive molecular traits of males and females within eukaryotes. Here, using morphologically indistinguishable isogametes of the colonial volvocine
Gonium pectorale
, we demonstrated that GCS1 is differently regulated between the sexes.
G. pectorale
GCS1 molecules in one sex (homologous to male) are transported from the gamete cytoplasm to the protruded fusion site, whereas those of the other sex (females) are quickly degraded within the cytoplasm upon gamete activation. This molecular trait difference might be conserved across various eukaryotic lineages and may represent male and female prototypes originating from a common eukaryotic ancestor.
The Precarious Prokaryotic Chromosome
Authors: Kuzminov Andrei 
Published: March 2014

ABSTRACT
Evolutionary selection for optimal genome preservation, replication, and expression should yield similar chromosome organizations in any type of cells. And yet, the chromosome organization is surprisingly different between eukaryotes and prokaryotes. The nuclear versus cytoplasmic accommodation of genetic material accounts for the distinct eukaryotic and prokaryotic modes of genome evolution, but it falls short of explaining the differences in the chromosome organization. I propose that the two distinct ways to organize chromosomes are driven by the differences between the global-consecutive chromosome cycle of eukaryotes and the local-concurrent chromosome cycle of prokaryotes. Specifically, progressive chromosome segregation in prokaryotes demands a single duplicon per chromosome, while other “precarious” features of the prokaryotic chromosomes can be viewed as compensations for this severe restriction.
Functional Dissection of Intersubunit Interactions in the EspR Virulence Regulator of Mycobacterium tuberculosis
Authors: Blasco Benjamin , Japaridze Aleksandre , Stenta Marco , Wicky Basile I. M. , Dietler Giovanni , Dal Peraro Matteo , Pojer Florence , Cole Stewart T. 
Published: March 2014

ABSTRACT

The nucleoid-associated protein EspR, a chromosome organizer, has pleiotropic effects on expression of genes associated with cell wall function and pathogenesis in
Mycobacterium tuberculosis
. In particular, EspR binds to several sites upstream of the
espACD
locus to promote its expression, thereby ensuring full function of the ESX-1 secretion system, a major virulence determinant. The N terminus of EspR contains the helix-turn-helix DNA-binding domain, whereas the C-terminal dimerization domain harbors residues involved in intersubunit interactions. While direct binding to DNA appears to be mediated by an EspR dimer-of-dimers, where two helix-turn-helix motifs remain free for long-range interactions, the mechanism of EspR higher-order organization and its impact on chromosome structure and gene expression are not understood. To investigate these processes, we identified seven amino acid residues using molecular dynamics and replaced them with Ala in order to probe interactions at either the dimer or the dimer-of-dimers interfaces. Arg70, Lys72, and Arg101 were important for protein stability and optimal DNA-binding activity. Moreover, the Arg70 mutant showed decreased dimerization in a mycobacterial two-hybrid system. To correlate these defects with higher-order organization and transcriptional activity, we used atomic force microscopy to observe different EspR mutant proteins in complex with the
espACD
promoter region. In addition, complementation of an
M. tuberculosis
espR
knockout mutant was performed to measure their impact on EspA expression. Our results pinpoint key residues required for EspR function at the dimer (Arg70) and the dimer-of-dimers (Lys72) interface and demonstrate that EspR dimerization and higher-order oligomerization modulate
espACD
transcriptional activity and hence pathogenesis.
Outer Membrane Protein OmpW Participates with Small Multidrug Resistance Protein Member EmrE in Quaternary Cationic Compound Efflux
Authors: Beketskaia Maria S. , Bay Denice C. , Turner Raymond J. 
Published: March 2014

ABSTRACT

In
Escherichia coli
, the small multidrug resistance (SMR) transporter protein EmrE confers host resistance to a broad range of toxic quaternary cation compounds (QCC) via proton motive force in the plasma membrane. Biologically produced QCC also act as EmrE osmoprotectant substrates within the cell and participate in host pH regulation and osmotic tolerance. Although
E. coli
EmrE is one of the most well-characterized SMR members, it is unclear how the substrates it transports into the periplasm escape across the outer membrane (OM) in Gram-negative bacteria. We tested the hypothesis that
E. coli
EmrE relies on an unidentified OM protein (OMP) to complete the extracellular release of its QCC. Eleven OMP candidates were screened using an alkaline phenotypic growth assay to identify OMP involvement in EmrE-mediated QCC efflux.
E. coli
single-gene deletion strains were transformed with plasmid-carried copies of
emrE
to detect reduced-growth and rescued-growth phenotypes under alkaline conditions. Among the 11 candidates, only the Δ
ompW
strain showed rescued alkaline growth tolerance when transformed with pEmrE, supporting the corresponding protein's involvement in EmrE osmoprotectant efflux. Coexpression of plasmids carrying the
ompW
and
emrE
genes transformed into the
E. coli
Δ
ompW
and Δ
emrE
strains demonstrated a functional complementation restoring the original alkaline loss-of-growth phenotype. Methyl viologen drug resistance assays of pEmrE and pOmpW plasmid-complemented
E. coli
Δ
ompW
and wild-type strains found higher host drug resistance than with other plasmid combinations. This study confirms our hypothesis that the porin OmpW participates in the efflux of EmrE-specific substrates across the OM.
Biochemical Characterization of a Nitrogen-Type Phosphotransferase System Reveals that Enzyme EI
Ntr
Integrates Carbon and Nitrogen Signaling in Sinorhizobium meliloti
Authors: Goodwin Reed A. , Gage Daniel J. 
Published: March 2014

ABSTRACT

In
Sinorhizobium meliloti
, catabolite repression is influenced by a noncanonical nitrogen-type phosphotransferase system (PTS
Ntr
). In this PTS
Ntr
, the protein HPr is phosphorylated on histidine-22 by the enzyme EI
Ntr
and the flux of phosphate through this residue onto downstream proteins leads to an increase in succinate-mediated catabolite repression (SMCR). In order to explore the molecular determinants of HPr phosphorylation by EI
Ntr
, both proteins were purified and the activity of EI
Ntr
was measured. Experimentally determined kinetic parameters of EI
Ntr
activity were significantly slower than those determined for the carbohydrate-type EI in
Escherichia coli
. Enzymatic assays showed that glutamine, a signal of nitrogen availability in many Gram-negative bacteria, strongly inhibits EI
Ntr
. Binding experiments using the isolated GAF domain of EI
Ntr
(EI
GAF
) showed that it is the domain responsible for detection of glutamine. EI
Ntr
activity was not affected by α-ketoglutarate, and no binding between the EI
GAF
and α-ketoglutarate could be detected. These data suggest that in
S. melilloti
, EI
Ntr
phosphorylation of HPr is regulated by signals from both carbon metabolism (phosphoenolpyruvate) and nitrogen metabolism (glutamine).