bluuebunny/crossref_metadata_2025 huggingface dataset:
One‐Step Reconstruction with a Novel Suspended, Modular, and 3D‐Printed Total Sacral Implant Resection of Sacral Giant Cell Tumor with Preservation of Bilateral S1–3 Nerve Roots via a Posterior‐Only Approach
Authors: Lv Zhao‐rui , Li Zhen‐feng , Yang Zhi‐ping , Li Xin , Yang Qiang , Li Ka , Li Jianmin
Published: December 2019

Objective

To investigate the efficacy and safety of spinopelvic reconstruction based on a novel suspended, modular, and 3D‐printed total sacral implant after total piecemeal resection of a sacral giant cell tumor (SGCT) with the preservation of bilateral S1–3 nerve roots via a posterior‐only approach.

Methods

Five patients who had undergone total piecemeal resection of SGCT involving upper sacral segments (S1 and S2) and the midline with the preservation of bilateral S1–3 nerve roots via a posterior‐only approach between September 2017 and July 2018 were retrospectively reviewed. A novel suspended, modular, and 3D‐printed total sacral implant had been used for reconstruction. This series included two female and three male patients, with a mean age of 42.2 years (range, 31–53 years). Surgical time, blood loss, complications, preoperative and postoperative neurological function, instrumentation failure, and local control were presented and analyzed.

Results

All patients underwent the operation without death or serious complications. The implant was installed on the defect, connecting the ilium and lumbar vertebrae, and fixed with a screw–rod system up to the level of L3–4 or L4–5. The mean operative time was 502 min (range, 360–640 min) and the mean operative blood loss 4400 mL (range, 3000–7000 mL). The mean follow‐up was 15 months. After the operation, pain was significantly relieved, and the patients resumed walking as early as 2 weeks later. The patients showed no neurogenic bladder dysfunction and no fecal incontinence or gait disturbance. Wound healing was poor in one patient. Patients recovered well without evidence of local recurrence. No implant failures or related clinical symptoms were detected during follow up. Satisfactory bone ingrowth and osseointegration at the bone‐implant junctions was found in follow‐up CT.

Conclusion

Although technically challenging, it is feasible and safe to use a suspended, modular, and 3D‐printed implant for reconstruction after total piecemeal resection with the preservation of bilateral S1–3 nerve roots in patients with SGCT. We believe that this implant can be applied to sacral reconstruction in a wide variety of diseases.
Pulmonary vein antral isolation causes depolarization of vein sleeves: Implications for the assessment of isolation
Authors: Saluja Deepak , Pagan Eric , Maglione Theodore , Kassotis John , Kostis William J. , Coromilas James
Published: December 2019

Purpose

Pulmonary vein isolation (PVI) for atrial fibrillation has been shown to result in inexcitability of a large fraction of pulmonary veins (PVs), but the mechanism is unknown. We investigated the mechanism of PV inexcitability by assessing the effects of PVI on the electrophysiology of PV sleeves.

Methods

Patients undergoing first‐time radiofrequency PVI were studied. Capture threshold, effective refractory period (ERP), and excitability were measured in PVs and the left atrial appendage (LAA) before and after ablation. Adenosine was used to assess both transient reconnection and transient venous re‐excitability.

Results

We assessed 248 veins among 67 patients. Mean PV ERP (249.7 ± 54.0 ms) and capture threshold (1.4 ± 1.6 mA) increased to 300.5 ± 67.1 and 5.7 ± 5.6 mA, respectively (P < .0001 for both) in the 26.9% PVs that remained excitable, but no change was noted in either measure in the LAA. In 16.3% of the 73.1% inexcitable veins, transient PV re‐excitability (as opposed to reconnection) was seen with adenosine administration.

Conclusions

Antral PVI causes inexcitability in a majority of the PVs, which can transiently be restored in some with adenosine. Among PVs that remain excitable, ERP and capture threshold increase significantly. These data imply resting membrane potential depolarization of the of PV myocardial sleeves. As PV inexcitability hampers the assessment of entrance and exit block, demonstrating transient PV re‐excitability during adenosine administration helps ensure true isolation.
Cavotricuspid isthmus is constantly a zone of slow conduction: Data from ultra‐high‐resolution mapping
Authors: Bun Sok‐Sithikun , Lațcu Decebal Gabriel , Wedn Ahmed Mostfa , Squara Fabien , Scarlatti Didier , Theodore Guillaume , Al Amoura Alaa , Benaïch Fatima Azzahrae , Hasni Karim , Saoudi Nadir , Ferrari Emile
Published: December 2019

Background

Whether cavotricuspid isthmus (CTI) is a region of conduction slowing during typical flutter has been discussed with conflicting results in the literature.

We aimed to evaluate conduction velocity (CV) along the different portions of the typical flutter circuit with a recently proposed method by means of ultra‐high‐resolution (UHR) mapping.

Methods

Consecutive patients referred for typical atrial flutter (AFL) ablation underwent UHR mapping (Rhythmia, Boston Scientific). CVs were measured in the CTI as well as laterally and septally, respectively, from its lateral and septal borders.

Results

A total of 33 patients (mean age: 65 ± 13 years; right atrial volume: 134 ± 57 mL) were mapped either during ongoing counterclockwise (n = 25), or clockwise (n = 3) AFL (mean cycle length: 264 ± 38 ms), or during coronary sinus pacing at 400 ms (n = 1), 500 ms (n = 1), or 600 ms (n = 3). A total of 13 671 ± 7264 electrograms were acquired in 14 ± 9 min. CTI CV was significantly lower (0.56  ± 0.18 m/s) in comparison with the lateral CV (1.31 ± 0.29 m/s; P < .0001) and the septal border CV of the CTI (1.29 ± 0.31 m/s; P < .0001).

Conclusion

UHR mapping confirmed that CTI CV was systematically twice lower than atrial conduction velocities outside the CTI.
Oligodendroglioma showing pleomorphic xanthoastrocytoma‐like perivascular microlesion: With IDH1, TERT promoter mutation and 1p/19q codeletion detected in both components
Authors: Murakami Chiaki , Ikota Hayato , Nobusawa Sumihito , Nakata Satoshi , Yamazaki Tatsuya , Hashiba Yasuhiro , Hirato Junko , Yokoo Hideaki
Published: December 2019

We report a histological and genetic study of concurrent oligodendroglioma and a microscopic pleomorphic xanthoastrocytoma (PXA)‐like lesion in a 48‐year‐old male. He presented with generalized seizure, and magnetic resonance imaging revealed a nonenhanced left frontal lobe mass suggesting low‐grade glioma. The patient underwent craniotomy and tumor resection. Histopathological examination of the surgical specimen showed an oligodendroglioma with a PXA‐like element; the latter measured 0.9 mm and occupied a Virchow‐Robin space of the superficial cortex. The whole tumor had no elevated mitotic activity, microvascular proliferation or necrosis. Each component was immunohistochemically isocitrate dehydrogenase (IDH1)‐R132H positive, p53 negative and ATRX positive. Genetic analyses clarified identical IDH1 G395A mutation, promoter C228T mutation and 1p/19q codeletion in both elements. Careful integration of histology and telomerase reverse transcriptase (TERT) molecular parameters revealed that this case was an oligodendroglioma showing PXA‐like features, rather than a collision tumor. This case provides further insights into the gliomagenesis.
Hepatitis B virus reactivation in kidney transplant patients with resolved hepatitis B virus infection: Risk factors and the safety and efficacy of preemptive therapy
Authors: Mei Takanori , Noguchi Hiroshi , Hisadome Yu , Kaku Keizo , Nishiki Takehiro , Okabe Yasuhiro , Nakamura Masafumi
Published: December 2019

Background

Hepatitis B virus (HBV) reactivation is associated with complications and adverse outcomes in patients with clinically resolved HBV infection who are seronegative for hepatitis B surface antigen (HBs Ag), and seropositive for hepatitis B core antibody (HBc Ab) and/or hepatitis B surface antibody (HBs Ab) before kidney transplantation (KT).

Methods

We retrospectively analyzed 52 patients with resolved HBV infection who were HBV‐DNA negative. HBV‐DNA after KT was evaluated, and the occurrence of HBV reactivation and outcomes were monitored. We defined HBV reactivation as seropositivity for HBV‐DNA at or above the minimal detection level of 1.0 log IU/mL and treated preemptively (using entecavir) when the HBV‐DNA level was at or above 1.3 log IU/mL, in accordance with the Japanese Guidelines for HBV treatment.

Results

Among the 52 patients, the mean age was 57.2 ± 10.8 years. The median HBc Ab titer was 12.8 (interquartile range, 4.6‐42.6) cutoff index, and five (9.6%) cases of HBV reactivation occurred. No patients developed graft loss and died due to HBV reactivation. Statistical analysis showed that age and HBc Ab titer were significant risk factors for HBV reactivation (P = .037 and P = .042, respectively). No significant differences were found between graft survival and the presence or absence of HBV reactivation.

Conclusion

These results suggest that HBc Ab titer and age could be significant risk factors for HBV reactivation. Resolution of HBV infection did not appear to be associated with patient or graft survival, regardless of whether HBV reactivation occurred, when following our preemptive strategy.
Efectos de la implementación de la Norma Internacional de Información Financiera en una pequeña empresa registrada en la ciudad de Guayaquil, Ecuador
Authors: Encalada Encarnación Vicente René , Castillo Coto Ana Lilia , Ruíz Quesada Sonia Caridad , Encarnación Merchán Otilia Máximina
Published: December 2019

Este artículo examina los efectos de la implementación de la Norma Internacional de Información Financiera –NIIF– para las Pymes en el caso de una empresa registrada en el directorio de la SC de la ciudad de Guayaquil-Ecuador (2017-2018). En el trabajo se elabora un modelo empírico, se aplica el método materialista para determinar los elementos comunes y las limitaciones de los fenómenos en consideración, y se exploran los resultados de la resolución emitida por la Superintendencia de Compañías del Ecuador con respecto a la NIIF. El principal resultado es que se obtiene una contabilidad confiable pues se logra que la información financiera presentada en los libros contables revele con fidelidad las operaciones, como se proponen las políticas contables establecidas. Se puede concluir que la adopción de la NIIF en la Pyme permite tomar mejores decisiones económicas, financieras y sociales.
On the Unsteady Wake of a Rigid Plate Under Constant Acceleration and Deceleration
Authors: Mao Zhongyu , Jin Yaqing , Wang Zhengwei , Chamorro Leonardo P.
Published: December 2019

Laboratory experiments are performed to explore distinct features of the unsteady wake induced by a rigid plate undergoing a series of accelerated and decelerated phases in a quiescent water tank. Each plate motion pattern is defined by a constant acceleration from the rest followed by the same magnitude deceleration until rest; i.e., both of them lasting the same time interval. Flow statistics are obtained for various plate acceleration/deceleration motions in a plane normal to the plate span using particle image velocimetry. Results revealed that the relative near-wake bulk flow underwent acceleration during 75% of the plate cycle; the associated maximum velocity was reached approximately at the middle of the deceleration phase in all the cases. Transversal velocity profiles in the near wake were significantly modulated by the magnitude and sign of the plate acceleration. The dynamics of the large-scale coherent motions shed by the plate was also dependent on plate acceleration pattern. However, the near-wake nondimensional circulation strength reached a plateau roughly at the end of the acceleration phase and was approximately conserved despite the modulation of the deceleration phase. In the early stage of the plate motion, the Lagrangian flow acceleration was dominant; however, the local acceleration dominated at the end of the cycle.
Role of template layers for heteroepitaxial growth of lanthanum oxide on GaN(0001) via atomic layer deposition
Authors: Chen Pei-Yu , Hadamek Tobias , Kwon Sunah , Al-Quaiti Fatima , Posadas Agham B. , Kim Moon J. , Demkov Alexander A. , Ekerdt John G.
Published: December 2019

La2O3 has been reported as a good gate dielectric for GaN-based high electron mobility transistor and metal-oxide-semiconductor field effect transistor applications. In this study, atomic layer deposition (ALD) was selected as the deposition technique, and the growth behavior and structure of La2O3 films on GaN(0001) were investigated. Unlike La2O3 deposited by molecular beam epitaxy (MBE) at 450 °C that can form a two-dimensional film directly on GaN(0001), island growth mode was observed when a La2O3 film was deposited directly on GaN(0001) at 250 °C by ALD using tris(N,N′-diisopropylformamidinato)-lanthanum as the precursor and H2O as the coreactant. Only with the use of a template layer, a 2 nm-thick hexagonal La2O3 film deposited by MBE or a 3 nm-thick cubic Er2O3 film deposited by ALD, can a two-dimensional crystalline ALD-La2O3 thin film be formed on GaN(0001). Reflection high-energy electron diffraction, x-ray diffraction, and scanning transmission electron microscopy were conducted to verify the films’ crystalline nature and structure. The ALD-La2O3 film retains a cubic structure on ALD-Er2O3 templated-GaN(0001), while it transforms from the cubic phase to a mix of cubic and hexagonal phases on MBE-La2O3 templated-GaN(0001) when the film is thicker than 15 nm. The stabilization of a thin cubic La2O3 phase could be related to a difference in the surface energy and the ALD growth temperature.
Superposition method for modelling boundaries between media in viscoelastic finite difference time domain simulations
Authors: Drainville Robert Andrew , Curiel Laura , Pichardo Samuel
Published: December 2019

Finite-difference time domain (FDTD) techniques are widely used to model the propagation of viscoelastic waves through complex and heterogeneous structures. However, in the specific case of media mixing liquid and solid, attempts to model continuous media onto a Cartesian grid produces errors when the liquid-solid interface between different media do not align precisely with the Cartesian grid. The increase in spatial resolution required to eliminate this grid staircasing effect can be computationally prohibitive. Here, a modification to the Virieux staggered-grid FDTD scheme called the superposition method is presented. This method is intended to reduce this staircasing effect while keeping a manageable computational time. The method was validated by comparing low-spatial-resolution simulations against simulations with sufficiently high resolution to provide reasonably accurate results at any incident angle. The comparison of the root-mean-square of the stress amplitude maps showed that the amplitude of artifactual waves could be reduced by several orders of magnitude when compared to the Virieux staggered-grid FDTD method and that the superposition method helped to significantly reduce the staircasing effect in FDTD simulations.
Examining the Impact of Body Satisfaction and Physical Activity Change on Postpartum Depressive Symptoms
Authors: Schlaff Rebecca A. , Baruth Meghan , LaFramboise Faith C. , Deere Samantha J.
Published: December 2019

Background: Relationships among moderate to vigorous physical activity (MVPA), body satisfaction, and postpartum depressive symptoms are not well understood. The purpose of this study is to examine the (1) impact of postpartum body satisfaction and changes in MVPA on postpartum depressive symptoms and (2) moderating effect of changes in MVPA over time on the relationship between postpartum body satisfaction and depressive symptoms. Methods: Participants (N = 269) self-reported body satisfaction, MVPA (prepregnancy through postpartum), and postpartum depressive symptoms. Differences in MVPA at 3 time points (prepregnancy, third trimester, and postpartum) were calculated to create change scores. Main effects and interactions (body satisfaction × MVPA change) were examined using multiple regression. Results: A majority of the sample did not meet MVPA recommendations at all time points. All body satisfaction measures were inversely related to postpartum depressive symptoms (P = .01 to <.001). MVPA change did not predict postpartum depressive symptoms (P = .43–.90) or moderate the relationship between body satisfaction and postpartum depressive symptoms (P = .14–.94). Conclusions: Given the relationship between postpartum body satisfaction and depressive symptoms, intervention research should include strategies that promote positive postpartum body image; clinicians should consider screening for body dissatisfaction. Although not a predictor or moderator, pregnancy and postpartum MVPA promotion should continue, as it has numerous other benefits.
The politics of zero-sum thinking: The relationship between political ideology and the belief that life is a zero-sum game
Authors: Davidai Shai , Ongis Martino
Published: December 2019

We find that both liberals and conservatives preserve the integrity of their ideological beliefs by viewing life as zero sum.
Degradation of Morpholine by an Environmental
Mycobacterium
Strain Involves a Cytochrome P-450
Authors: Poupin P. , Truffaut N. , Combourieu B. , Besse P. , Sancelme M. , Veschambre H. , Delort A. M.
Published: December 2019

A
Mycobacterium
strain (RP1) was isolated from a contaminated activated sludge collected in a wastewater treatment unit of a chemical plant. It was capable of utilizing morpholine and other heterocyclic compounds, such as pyrrolidine and piperidine, as the sole source of carbon, nitrogen, and energy. The use of in situ
1
H nuclear magnetic resonance (
1
H NMR) spectroscopy allowed the determination of two intermediates in the biodegradative pathway, 2-(2-aminoethoxy)acetate and glycolate. The inhibitory effects of metyrapone on the degradative abilities of strain RP1 indicated the involvement of a cytochrome P-450 in the biodegradation of morpholine. This observation was confirmed by spectrophotometric analysis and
1
H NMR. Reduced cell extracts from morpholine-grown cultures, but not succinate-grown cultures, gave rise to a carbon monoxide difference spectrum with a peak near 450 nm, which indicated the presence of a soluble cytochrome P-450.
1
H NMR allowed the direct analysis of the incubation medium containing metyrapone, a specific inhibitor of cytochrome P-450. The inhibition of morpholine degradation was dependent on the morpholine/metyrapone ratio. The heme-containing monooxygenase was also detected in pyrrolidine- and piperidine-grown cultures. The abilities of different compounds to support strain growth or the induction of a soluble cytochrome P-450 were assayed. The results suggest that this enzyme catalyzes the cleavage of the C—N bond of the morpholine ring.
Purification and Characterization of a Novel Thermostable α-
l
-Arabinofuranosidase from a Color-Variant Strain of
Aureobasidium pullulans
Authors: Saha Badal C. , Bothast Rodney J.
Published: December 2019

A color-variant strain of
Aureobasidium pullulans
(NRRL Y-12974) produced α-
l
-arabinofuranosidase (α-
l
-AFase) when grown in liquid culture on oat spelt xylan. An extracellular α-
l
-AFase was purified 215-fold to homogeneity from the culture supernatant by ammonium sulfate treatment, DEAE Bio-Gel A agarose column chromatography, gel filtration on a Bio-Gel A-0.5m column, arabinan-Sepharose 6B affinity chromatography, and SP-Sephadex C-50 column chromatography. The purified enzyme had a native molecular weight of 210,000 and was composed of two equal subunits. It had a half-life of 8 h at 75°C, displayed optimal activity at 75°C and pH 4.0 to 4.5, and had a specific activity of 21.48 μmol · min
−1
· mg
−1
of protein against
p
-nitrophenyl-α-
l
-arabinofuranoside (pNPαAF). The purified α-
l
-AFase readily hydrolyzed arabinan and debranched arabinan and released arabinose from arabinoxylans but was inactive against arabinogalactan. The

K
m

values of the enzyme for the hydrolysis of pNPαAF, arabinan, and debranched arabinan at 75°C and pH 4.5 were 0.26 mM, 2.14 mg/ml, and 3.25 mg/ml, respectively. The α-
l
-AFase activity was not inhibited at all by
l
-arabinose (1.2 M). The enzyme did not require a metal ion for activity, and its activity was not affected by
p
-chloromercuribenzoate (0.2 mM), EDTA (10 mM), or dithiothreitol (10 mM).
Impact of Inoculation Protocols, Salinity, and pH on the Degradation of Polycyclic Aromatic Hydrocarbons (PAHs) and Survival of PAH-Degrading Bacteria Introduced into Soil
Authors: Kästner Matthias , Breuer-Jammali Maren , Mahro Bernd
Published: December 2019

Degradation of polycyclic aromatic hydrocarbons (PAHs) and survival of bacteria in soil was investigated by applying different inoculation protocols. The soil was inoculated with
Sphingomonas paucimobilis
BA 2 and strain BP 9, which are able to degrade anthracene and pyrene, respectively. CFU of soil bacteria and of the introduced bacteria were monitored in native and sterilized soil at different pHs. Introduction with mineral medium inhibited PAH degradation by the autochthonous microflora and by the strains tested. After introduction with water (without increase of the pore water salinity), no inhibition of the autochthonous microflora was observed and both strains exhibited PAH degradation.
Survival in Soil of Different Toluene-Degrading
Pseudomonas
Strains after Solvent Shock
Authors: Huertas María-José , Duque Estrella , Marqués Silvia , Ramos Juan L.
Published: December 2019

We assayed the tolerance to solvents of three toluene-degrading
Pseudomonas putida
strains and
Pseudomonas mendocina
KR1 in liquid and soil systems.
P. putida
DOT-T1 tolerated concentrations of heptane, propylbenzene, octanol, and toluene of at least 10% (vol/vol), while
P. putida
F1 and EEZ15 grew well in the presence of 1% (vol/vol) propylbenzene or 10% (vol/vol) heptane, but not in the presence of similar concentrations of octanol or toluene.
P. mendocina
KR1 grew only in the presence of heptane. All three
P. putida
strains were able to become established in a fluvisol soil from the Granada, Spain, area, whereas
P. mendocina
KR1 did not survive in this soil. The tolerance to organic solvents of all three
P. putida
strains was therefore assayed in soil. The addition to soil of 10% (vol/wt) heptane or 10% (vol/wt) propylbenzene did not affect the survival of the three
P. putida
strains. However, the addition of 10% (vol/wt) toluene led to an immediate decrease of several log units in the number of CFU per gram of soil for all of the strains, although
P. putida
F1 and DOT-T1 subsequently recovered. This recovery was influenced by the humidity of the soil and the incubation temperature.
P. putida
DOT-T1 recovered from the shock faster than
P. putida
F1; this allowed the former strain to become established at higher densities in polluted sites into which both strains had been introduced.
The Sequence of Spacers between the Consensus Sequences Modulates the Strength of Prokaryotic Promoters
Authors: Jensen Peter Ruhdal , Hammer Karin
Published: December 2019

We constructed a library of synthetic promoters for
Lactococcus lactis
in which the known consensus sequences were kept constant while the sequences of the separating spacers were randomized. The library consists of 38 promoters which differ in strength from 0.3 up to more than 2,000 relative units, the latter among the strongest promoters known for this organism. The ranking of the promoter activities was somewhat different when assayed in
Escherichia coli
, but the promoters are efficient for modulating gene expression in this bacterium as well. DNA sequencing revealed that the weaker promoters (which had activities below 5 relative units) all had changes either in the consensus sequences or in the length of the spacer between the −35 and −10 sequences. The promoters in which those features were conserved had activities from 5 to 2,050 U, which shows that by randomizing the spacers, at least a 400-fold change in activity can be obtained. Interestingly, the entire range of promoter activities is covered in small steps of activity increase, which makes these promoters very suitable for quantitative physiological studies and for fine-tuning of gene expression in industrial bioreactors and cell factories.
Cloning and Characterization of Two Pyruvate Decarboxylase Genes from
Pichia stipitis
CBS 6054
Authors: Lu Ping , Davis Brian P. , Jeffries Thomas W.
Published: December 2019

In
Pichia stipitis
, fermentative and pyruvate decarboxylase (PDC) activities increase with diminished oxygen rather than in response to fermentable sugars. To better characterize
PDC
expression and regulation, two genes for PDC (
PsPDC1
and
PsPDC2
) were cloned and sequenced from
P. stipitis
CBS 6054. Aside from
Saccharomyces cerevisiae
, from which three PDC genes have been characterized,
P. stipitis
is the only organism from which multiple genes for PDC have been identified and characterized.
PsPDC1
and
PsPDC2
have diverged almost as far from one another as they have from the next most closely related known yeast gene.
PsPDC1
contains an open reading frame of 1,791 nucleotides encoding 597 amino acids.
PsPDC2
contains a reading frame of 1,710 nucleotides encoding 570 amino acids. An 81-nucleotide segment in the middle of the β domain of
PsPDC1
codes for a unique segment of 27 amino acids, which may play a role in allosteric regulation. The 5′ regions of both
P. stipitis
genes include two putative TATA elements that make them similar to the PDC genes from
S. cerevisiae
,
Kluyveromyces marxianus
, and
Hanseniaspora uvarum.
Secondary Metabolite- and Endochitinase-Dependent Antagonism toward Plant-Pathogenic Microfungi of
Pseudomonas fluorescens
Isolates from Sugar Beet Rhizosphere
Authors: Nielsen Mette Neiendam , Sørensen Jan , Fels Johannes , Pedersen Hans Christian
Published: December 2019

Forty-seven isolates representing all biovars of
Pseudomonas fluorescens
(biovars I to VI) were collected from the rhizosphere of field-grown sugar beet plants to select candidate strains for biological control of preemergence damping-off disease. The isolates were tested for in vitro antagonism toward the plant-pathogenic microfungi
Pythium ultimum
and
Rhizoctonia solani
in three different plate test media. Mechanisms of fungal inhibition were elucidated by tracing secondary-metabolite production and cell wall-degrading enzyme activity in the same media. Most biovars expressed a specific mechanism of antagonism, as represented by a unique antibiotic or enzyme production in the media. A lipopeptide antibiotic, viscosinamide, was produced independently of medium composition by
P. fluorescens
bv. I, whereas the antibiotic 2,4-diacetylphloroglucinol was observed only in glucose-rich medium and only in
P. fluorescens
bv. II/IV. Both pathogens were inhibited by the two antibiotics. Finally, in low-glucose medium, a cell wall-degrading endochitinase activity in
P. fluorescens
bv. I, III, and VI was the apparent mechanism of antagonism toward
R. solani
. The viscosinamide-producing DR54 isolate (bv. I) was shown to be an effective candidate for biological control, as tested in a pot experiment with sugar beet seedlings infested with
Pythium ultimum
. The assignment of different patterns of fungal antagonism to the biovars of
P. fluorescens
is discussed in relation to an improved selection protocol for candidate strains to be used in biological control.
Two Intracellular Symbiotic Bacteria from the Mulberry Psyllid
Anomoneura mori
(Insecta, Homoptera)
Authors: Fukatsu Takema , Nikoh Naruo
Published: December 2019

We characterized the intracellular symbiotic bacteria of the mulberry psyllid
Anomoneura mori
by performing a molecular phylogenetic analysis combined with in situ hybridization. In its abdomen, the psyllid has a large, yellow, bilobed mycetome (or bacteriome) which consists of many round uninucleated mycetocytes (or bacteriocytes) enclosing syncytial tissue. The mycetocytes and syncytium harbor specific intracellular bacteria, the X-symbionts and Y-symbionts, respectively. Almost the entire length of the bacterial 16S ribosomal DNA (rDNA) was amplified and cloned from the whole DNA of
A. mori
, and two clones, the A-type and B-type clones, were identified by restriction fragment length polymorphism analysis. In situ hybridization with specific oligonucleotide probes demonstrated that the A-type and B-type 16S rDNAs were derived from the X-symbionts and Y-symbionts, respectively. Molecular phylogenetic analyses of the 16S rDNA sequences showed that these symbionts belong to distinct lineages in the γ subdivision of the
Proteobacteria
. No 16S rDNA sequences in the databases were closely related to the 16S rDNA sequences of the X- and Y-symbionts. However, the sequences that were relatively closely related to them were the sequences of endosymbionts of other insects. The nucleotide compositions of the 16S rDNAs of the X- and Y-symbionts were highly AT biased, and the sequence of the X-symbiont was the most AT-rich bacterial 16S rDNA sequence reported so far.
Plasmids Responsible for Horizontal Transfer of Naphthalene Catabolism Genes between Bacteria at a Coal Tar-Contaminated Site Are Homologous to pDTG1 from
Pseudomonas putida
NCIB 9816-4
Authors: Stuart-Keil K. G. , Hohnstock A. M. , Drees K. P. , Herrick J. B. , Madsen E. L.
Published: December 2019

The presence of a highly conserved
nahAc
allele among phylogenetically diverse bacteria carrying naphthalene-catabolic plasmids provided evidence for in situ horizontal gene transfer at a coal tar-contaminated site (J. B. Herrick, K. G. Stuart-Keil, W. C. Ghiorse, and E. L. Madsen, Appl. Environ. Microbiol. 63:2330–2337, 1997). The objective of the present study was to identify and characterize the different-sized naphthalene-catabolic plasmids in order to determine the probable mechanism of horizontal transfer of the
nahAc
gene in situ. Filter matings between naphthalene-degrading bacterial isolates and their cured progeny revealed that the naphthalene-catabolic plasmids were self-transmissible. Limited interstrain transfer was also found. Analysis of the restriction fragment length polymorphism (RFLP) patterns indicated that catabolic plasmids from 12 site-derived isolates were closely related to each other and to the naphthalene-catabolic plasmid (pDTG1) of
Pseudomonas putida
NCIB 9816-4, which was isolated decades ago in Bangor, Wales. The similarity among all site-derived naphthalene-catabolic plasmids and pDTG1 was confirmed by using the entire pDTG1 plasmid as a probe in Southern hybridizations. Two distinct but similar naphthalene-catabolic plasmids were retrieved directly from the microbial community indigenous to the contaminated site in a filter mating by using a cured, rifampin-resistant site-derived isolate as the recipient. RFLP patterns and Southern hybridization showed that both of these newly retrieved plasmids, like the isolate-derived plasmids, were closely related to pDTG1. These data indicate that a pDTG1-like plasmid is the mobile genetic element responsible for transferring naphthalene-catabolic genes among bacteria in situ. The pervasiveness and persistence of this naphthalene-catabolic plasmid suggest that it may have played a role in the adaptation of this microbial community to the coal tar contamination at our study site.
A Plant Growth-Promoting Bacterium That Decreases Nickel Toxicity in Seedlings
Authors: Burd Genrich I. , Dixon D. George , Glick Bernard R.
Published: December 2019

A plant growth-promoting bacterium,Kluyvera ascorbataSUD165, that contained high levels of heavy metals was isolated from soil collected near Sudbury, Ontario, Canada. The bacterium was resistant to the toxic effects of Ni2+, Pb2+, Zn2+, and CrO4−, produced a siderophore(s), and displayed 1-aminocyclopropane-1-carboxylic acid deaminase activity. Canola seeds inoculated with this bacterium and then grown under gnotobiotic conditions in the presence of high concentrations of nickel chloride were partially protected against nickel toxicity. In addition, protection by the bacterium against nickel toxicity was evident in pot experiments with canola and tomato seeds. The presence ofK. ascorbataSUD165 had no measurable influence on the amount of nickel accumulated per milligram (dry weight) of either roots or shoots of canola plants. Therefore, the bacterial plant growth-promoting effect in the presence of nickel was probably not attributable to the reduction of nickel uptake by seedlings. Rather, it may reflect the ability of the bacterium to lower the level of stress ethylene induced by the nickel.
Characterization of
aflJ
, a Gene Required for Conversion of Pathway Intermediates to Aflatoxin
Authors: Meyers D. M. , Obrian G. , Du W. L. , Bhatnagar D. , Payne G. A.
Published: December 2019

The genes encoding the aflatoxin biosynthetic pathway enzymes have been localized as a cluster to a 75-kb DNA fragment. The enzymatic functions of the products of most of the genes in the cluster are known, but there are a few genes that have not yet been characterized. We report here the characterization of one of these genes, a gene designated
aflJ
. This gene resides in the cluster adjacent to the pathway regulatory gene,
aflR
, and the two genes are divergently transcribed. Disruption of
aflJ
in
Aspergillus flavus
results in a failure to produce aflatoxins and a failure to convert exogenously added pathway intermediates norsolorinic acid, sterigmatocystin, and
O
-methylsterigmatocystin to aflatoxin. The disrupted strain does, however, accumulate
pksA
,
nor-1
,
ver-1
, and
omtA
transcripts under conditions conducive to aflatoxin biosynthesis. Therefore, disruption of
aflJ
does not affect transcription of these genes, and
aflJ
does not appear to have a regulatory function similar to that of
aflR
. Sequence analysis of
aflJ
and its putative peptide, AflJ, did not reveal any enzymatic domains or significant similarities to proteins of known function. The putative peptide does contain three regions predicted to be membrane-spanning domains and a microbodies C-terminal targeting signal.
Distribution and Life Strategies of Two Bacterial Populations in a Eutrophic Lake
Authors: Weinbauer Markus G. , Höfle Manfred G.
Published: December 2019

Monoclonal antibodies and epifluorescence microscopy were used to determine the depth distribution of two indigenous bacterial populations in the stratified Lake Plußsee and characterize their life strategies. Populations of
Comamonas acidovorans
PX54 showed a depth distribution with maximum abundances in the oxic epilimnion, whereas
Aeromonas hydrophila
PU7718 showed a depth distribution with maximum abundances in the anoxic thermocline layer (metalimnion), i.e., in the water layer with the highest microbial activity. Resistance of PX54 to protist grazing and high metabolic versatility and growth rate of PU7718 were the most important life strategy traits for explaining the depth distribution of the two bacterial populations. Maximum abundance of PX54 was 16,000 cells per ml, and maximum abundance of PU7718 was 20,000 cells per ml. Determination of bacterial productivity in dilution cultures with different-size fractions of dissolved organic matter (DOM) from lake water indicates that low-molecular-weight (LMW) DOM is less bioreactive than total DOM (TDOM). The abundance and growth rate of PU7718 were highest in the TDOM fractions, whereas those of PX54 were highest in the LMW DOM fraction, demonstrating that PX54 can grow well on the less bioreactive DOM fraction. We estimated that 13 to 24% of the entire bacterial community and 14% of PU7718 were removed by viral lysis, whereas no significant effect of viral lysis on PX54 could be detected. Growth rates of PX54 (0.11 to 0.13 h
−1
) were higher than those of the entire bacterial community (0.04 to 0.08 h
−1
) but lower than those of PU7718 (0.26 to 0.31 h
−1
). In undiluted cultures, the growth rates were significantly lower, pointing to density effects such as resource limitation or antibiosis, and the effects were stronger for PU7718 and the entire bacterial community than for PX54. Life strategy characterizations based on data from literature and this study revealed that the fast-growing and metabolically versatile
A. hydrophila
PU7718 is an
r
-strategist or opportunistic population in Lake Plußsee, whereas the grazing-resistant
C. acidovorans
PX54 is rather a
K
-strategist or equilibrium population.
Degradation of 1,2,3,4-Tetrachlorobenzene by
Pseudomonas chlororaphis
RW71
Authors: Potrawfke Thomas , Timmis Kenneth Nigel , Wittich Rolf-Michael
Published: December 2019

Pseudomonas chlororaphis
RW71 mineralized 1,2,3,4-tetrachlorobenzene, a highly recalcitrant pollutant hitherto not known to be degraded by pure cultures, as a sole source of carbon and energy, thereby releasing stoichiometric amounts of chloride. The transient excretion of tetrachlorocatechol in the early growth phase suggests an initial attack by a dioxygenase to form the corresponding dihydrodiol which rearomatizes to the catechol. The activity of chlorocatechol 1,2-dioxygenase in crude cell extracts was found to be extraordinarily high towards 3-chlorocatechol (ratio of 2.6 compared to catechol) and other chlorocatechols, including tetrachlorocatechol, which was transformed at a low but significant rate. Further identification of tetrachloromuconic acid, 2,3,5-trichlorodienelactone, 2,3,5-trichloromaleyl acetic acid, and 2,4-dichloro-3-oxoadipic acid as their methyl esters, together with high specific enzyme activities for chlorinated substrates, implicated a functioning chlorocatechol pathway to be induced during growth.
New Hybrids betweenSaccharomycesSensu Stricto Yeast Species Found among Wine and Cider Production Strains
Authors: Masneuf Isabelle , Hansen Jørgen , Groth Casper , Piskur Jure , Dubourdieu Denis
Published: December 2019

Two yeast isolates, a wine-making yeast first identified as a Mel+strain (ex.S. uvarum) and a cider-making yeast, were characterized for their nuclear and mitochondrial genomes. Electrophoretic karyotyping analyses, restriction fragment length polymorphism maps of PCR-amplifiedMET2gene fragments, and the sequence analysis of a part of the twoMET2gene alleles found support the notion that these two strains constitute hybrids betweenSaccharomyces cerevisiaeandSaccharomyces bayanus. The two hybrid strains had completely different restriction patterns of mitochondrial DNA as well as different sequences of theOLI1gene. The sequence of theOLI1gene from the wine hybrid strain appeared to be the same as that of theS. cerevisiaegene, whereas theOLI1gene of the cider hybrid strain is equally divergent from both putative parents,S. bayanusandS. cerevisiae. Some fermentative properties were also examined, and one phenotype was found to reflect the hybrid nature of these two strains. The origin and nature of such hybridization events are discussed.
Effects of Visible Light and UV Radiation on Photosynthesis in a Population of a Hot Spring Cyanobacterium, a
Synechococcus
sp., Subjected to High-Temperature Stress
Authors: Miller Scott R. , Wingard Christopher E. , Castenholz Richard W.
Published: December 2019

Assays of photosynthesis were conducted with a biofilm population of a cyanobacterium, a
Synechococcus
sp., growing at ∼70°C in a Yellowstone National Park hot spring to test whether cells growing near the upper temperature limit of photosynthetic life are optimally adapted to their mean environmental temperature. Cell suspensions were assayed at 70, 65, and 55°C while being simultaneously exposed to modified solar environments, including reduction of total irradiance and exclusion of UV radiation. Carbon fixation was greatest at 65°C, while 70 and 55°C were always supraoptimal and suboptimal for photosynthesis, respectively. The degree of temperature stress was dependent upon light intensity, and this light-dependent temperature effect may involve both reduced quantum efficiency at subsaturating irradiances and a lower saturating irradiance at both supraoptimal and suboptimal temperatures. The
Synechococcus
sp. was also more susceptible to UV inhibition of photosynthesis at nonoptimal temperatures. These results suggest that this population is persisting at a nearly lethal temperature and is consequently subject to greater damage by both visible and UV radiation, but it is speculated that these cells may be avoiding competition with other photoautotrophs under these nonoptimal conditions. In separate experiments monitoring diurnal patterns of photosynthesis, cells exhibited peak productivity during the morning, followed by an afternoon decline. No recovery of photosynthesis was observed during the remaining daytime, and carbon fixation was always UV inhibited under conditions of photosynthetically saturating light.
Determination of the Biomasses of Small Bacteria at Low Concentrations in a Mixture of Species with Forward Light Scatter Measurements by Flow Cytometry
Authors: Robertson B. R. , Button D. K. , Koch A. L.
Published: December 2019

The forward light scatter intensity of bacteria analyzed by flow cytometry varied with their dry mass, in accordance with theory. A standard curve was formulated with Rayleigh-Gans theory to accommodate cell shape and alignment. It was calibrated with an extinction-culture isolate of the small marine organism
Cycloclasticus oligotrophus
, for which dry weight was determined by CHN analysis and
14
C-acetate incorporation. Increased light scatter intensity due to formaldehyde accumulation in preserved cells was included in the standard curve. When differences in the refractive indices of culture media and interspecies differences in the effects of preservation were taken into account, there was agreement between cell mass obtained by flow cytometry for various bacterial species and cell mass computed from Coulter Counter volume and buoyant density. This agreement validated the standard curve and supported the assumption that cells were aligned in the flow stream. Several subpopulations were resolved in a mixture of three species analyzed according to forward light scatter and DNA-bound DAPI (4′,6-diamidino-2-phenylindole) fluorescence intensity. The total biomass of the mixture was 340 μg/liter. The lowest value for mean dry mass, 0.027 ± 0.008 pg/cell, was for the subpopulation of
C. oligotrophus
containing cells with a single chromosome. Calculations from measurements of dry mass, Coulter Counter volume, and buoyant density revealed that the dry weight of the isolate was 14 to 18% of its wet weight, compared to 30% for
Escherichia coli
. The method is suitable for cells with 0.005 to about 1.2 pg of dry weight at concentrations of as low as 10
3
cells/ml and offers a unique capability for determining biomass distributions in mixed bacterial populations.
Bacterial Stress Responses to 1-Megahertz Pulsed Ultrasound in the Presence of Microbubbles
Authors: Vollmer Amy C. , Kwakye Sylvia , Halpern Matthew , Everbach E. Carr
Published: December 2019

Members of a panel of stress-responsive biosensors have been used to study the effect of megahertz frequency ultrasound on
Escherichia coli
. Insonification causes acoustic cavitation, the collapse of oscillating microbubbles in solution, which can damage bacterial cells. A focused 1-MHz ultrasound transducer, capable of generating a spatial peak pulse average intensity of 500 W/cm
2
, was used to treat liquid bacterial cultures. Stress-responsive promoters fused to
luxCDABE
allowed the continuous measurement of light produced as a result of protein damage, DNA damage, oxidative stress, and membrane perturbation. A promoter responsive to ammonia limitation was not transcriptionally activated under test conditions. In contrast to bacteria in exponentially growing cultures, those in stationary-phase cultures were more resistant to the effects of ultrasound treatment. Quantification of the degree of acoustic cavitation due to symmetric bubble collapse was measured by a 20-MHz passive transducer, the output of which appears to be only partially correlated with cellular damage and survival. The methods and results summarized here provide the basis for further investigation into applications, including the purification of water samples.
PCR-Based Detection of the Causal Agent of Watermark Disease in Willows (
Salix
spp.)
Authors: Hauben L. , Steenackers M. , Swings J.
Published: December 2019

The watermark disease, caused by
Brenneria salicis
(formerly
Erwinia salicis
), is of significant concern wherever tree-forming willows are grown or occur naturally. The movement of infected, asymptomatic cuttings is a major cause of pathogen dispersal. A reliable and sensitive diagnostic procedure is necessary for the safe movement of willow planting material. We derived primers from the nucleotide sequence of the 16S rRNA gene of
B. salicis
for the development of a PCR to detect this pathogen. One set of primers, Es1a-Es4b, directed the amplification of a 553-bp fragment from
B. salicis
genomic DNA as well as
B. salicis
cells. PCR products were not observed when genomic DNA was tested for 27 strains of other, related plant-associated bacteria. Genomic fingerprinting by amplification fragment length polymorphism of
B. salicis
strains, originating from four different countries, and related
Brenneria
,
Pectobacterium
, and
Erwinia
strains revealed a very high similarity among the
B. salicis
genomes, indicating that the spread of the pathogen is mainly due to the transportation of infected cuttings. The PCR had to be preceded by a DNA extraction in order to detect the pathogen in the vascular fluid of willows. The minimum number of cells that could be detected from vascular fluid was 20 CFU/ml. The PCR assays proved to be very sensitive and reliable in detecting
B. salicis
in willow plant material.
Sequence and Secondary Structure of the Mitochondrial Small-Subunit rRNA V4, V6, and V9 Domains Reveal Highly Species-Specific Variations within the Genus
Agrocybe
Authors: Gonzalez Patrice , Labarère Jacques
Published: December 2019

A comparative study of variable domains V4, V6, and V9 of the mitochondrial small-subunit (SSU) rRNA was carried out with the genus
Agrocybe
by PCR amplification of 42 wild isolates belonging to 10 species,
Agrocybe aegerita
,
Agrocybe dura
,
Agrocybe chaxingu
,
Agrocybe erebia
,
Agrocybe firma
,
Agrocybe praecox
,
Agrocybe paludosa
,
Agrocybe pediades
,
Agrocybe alnetorum
, and
Agrocybe vervacti
. Sequencing of the PCR products showed that the three domains in the isolates belonging to the same species were the same length and had the same sequence, while variations were found among the 10 species. Alignment of the sequences showed that nucleotide motifs encountered in the smallest sequence of each variable domain were also found in the largest sequence, indicating that the sequences evolved by insertion-deletion events. Determination of the secondary structure of each domain revealed that the insertion-deletion events commonly occurred in regions not directly involved in the secondary structure (i.e., the loops). Moreover, conserved sequences ranging from 4 to 25 nucleotides long were found at the beginning and end of each domain and could constitute genus-specific sequences. Comparisons of the V4, V6, and V9 secondary structures resulted in identification of the following four groups: (i) group I, which was characterized by the presence of additional P23-1 and P23-3 helices in the V4 domain and the lack of the P49-1 helix in V9 and included
A. aegerita
,
A. chaxingu
, and
A. erebia
; (ii) group II, which had the P23-3 helix in V4 and the P49-1 helix in V9 and included
A. pediades
; (iii) group III, which did not have additional helices in V4, had the P49-1 helix in V9 and included
A. paludosa
,
A. firma
,
A. alnetorum
, and
A. praecox
; and (iv) group IV, which lacked both the V4 additional helices and the P49-1 helix in V9 and included
A. vervacti
and
A. dura
. This grouping of species was supported by the structure of a consensus tree based on the variable domain sequences. The conservation of the sequences of the V4, V6, and V9 domains of the mitochondrial SSU rRNA within species and the high degree of interspecific variation found in the
Agrocybe
species studied open the way for these sequences to be used as specific molecular markers of the Basidiomycota.