A novel Rap-Phr system in Bacillus velezensis NAU-B3 regulates surfactin production and sporulation via interaction with ComA.

Several quorum sensing systems occurring in Bacillus subtilis, e.g. Rap-Phr systems, were reported to interact with major regulatory proteins, such as ComA, DegU, and Spo0A, in order to regulate competence, sporulation, and synthesis of secondary metabolites. In this study, we characterized a novel Rap-Phr system, RapA4-PhrA4, in Bacillus velezensis NAU-B3. We found that the rapA4 and phrA4 genes were co-transcribed in NAU-B3. When rapA4 was expressed in the heterologous host Bacillus subtilis OKB105, surfactin production and sporulation were severely inhibited. However, when the phrA4 was co-expressed, the RapA4 activity was inhibited. The transcription of the surfactin synthetase srfA gene and sporulation-related genes were also regulated by the RapA4-PhrA4 system. In vitro results obtained from electrophoretic mobility shift assay (EMSA) proved that RapA4 inhibits ComA binding to the promoter of the srfA operon, and the PhrA4 pentapeptide acts as anti-activator of RapA4. We also found that the F24 residue plays a key role in RapA4 function. This study indicated that the novel RapA4-PhrA4 system regulates the surfactin synthesis and sporulation via interaction with ComA, thereby supporting the bacterium to compete and to survive in a hostile environment. KEY POINTS: •Bacillus velezensis NAU-B3 has a novel Rap-Phr quorum sensing system, which does not occur in model strains Bacillus subtilis 168 and B. velezensis FZB42. •RapA4-PhrA4 regulates surfactin production and sporulation. •RapA4-PhrA4 interacts with the ComA protein from ComP/ComA two-component system.

Effects of ANP on pulmonary vein electrophysiology, Ca2+ homeostasis and adrenergic arrhythmogenesis via PKA.

Atrial fibrillation (AF) is the most common form of arrhythmia and increases the risk of stroke and heart failure (HF). Pulmonary veins (PVs) are important sources of triggers that generate AF, and calcium (Ca2+ ) overload participates in PV arrhythmogenesis. Neurohormonal activation is an important cause of AF. Higher atrial natriuretic peptide (ANP) level predicts paroxysmal AF occurrence in HF patients. However, it is not clear if ANP directly modulates electrophysiological characteristics and Ca2+ homeostasis in the PVs. Conventional microelectrodes, whole-cell patch-clamp, and the Fluo-3 fluorimetric ratio technique were performed using isolated rabbit PV preparations or single isolated PV cardiomyocytes before and after ANP administration. We found that ANP (1, 10, and 100 nmol/L) concentration-dependently decreased spontaneous activity in PV preparations. ANP (100 nmol/L) decreased isoproterenol (1 µmol/L)-induced PV spontaneous activity and burst firing. AP811 (100 nmol/L, NPR-C agonist), H89 (1µmol/L, PKA inhibitor) decreased isoproterenol-induced PV spontaneous activity or burst firing, but successive administration of ANP had no further effect on PV activity. KT5823 (1 µmol/L, PKG inhibitor) decreased isoproterenol-induced PV spontaneous activity but did not change isoproterenol-induced PV burst firing, whereas successive administration of ANP did not change isoproterenol-induced PV burst firing. ANP decreased intracellular Ca2+ transient and sarcoplasmic reticulum Ca2+ content in single PV cardiomyocytes. ANP decreased the late sodium current, L-type Ca2+ current, but did not change nickel-sensitive Na+ -Ca2+ exchanger current in single PV cardiomyocytes. In conclusion, ANP directly regulates PV electrophysiological characteristics and Ca2+ homeostasis and attenuates isoproterenol-induced arrhythmogenesis through NPR-C/cAMP/PKA signal pathway.

Ultrathin Planar Cavity Metasurfaces.

An ultrathin planar cavity metasurface is proposed based on ultrathin film interference and its practicability for light manipulation in visible region is experimentally demonstrated. Phase of reflected light is modulated by finely adjusting the thickness of amorphous silicon (a-Si) by a few nanometers on an aluminum (Al) substrate via nontrivial phase shifts at the interfaces and interference of multireflections generated from the planar cavity. A phase shift of π, the basic requirement for two-level phase metasurface systems, can be accomplished with an 8 nm thick difference. For proof of concept, gradient metasurfaces for beam deflection, Fresnel zone plate metalens for light focusing, and metaholograms for image reconstruction are presented, demonstrating polarization-independent and broadband characteristics. This novel mechanism for phase modulation with ultrathin planar cavity provides diverse routes to construct advanced flat optical devices with versatile applications.

Preparation of Nanofibrous Silver/Poly(vinylidene fluoride) Composite Membrane with Enhanced Infrared Extinction and Controllable Wetting Property.

Nanofibrous silver (Ag)/poly(vinylidene fluoride) (PVDF) composite membranes were obtained from a two-step preparation method. In the first step, the electrospun silver nitrate (AgNO3)/PVDF membranes were prepared and the influence of the AgNO3 content on the electrospinning process was studied. According to scanning electron microscopy (SEM) results, when the electrospinning solution contained AgNO3 in the range between 3 to 7 wt.%, the nanofiber morphologies can be obtained. In the second step, the electrospun AgNO3/PVDF membranes were reduced by sodium borohydride to form the nanofibrous Ag/PVDF composite membranes. The resultant composite membranes were characterized by SEM, X-ray diffraction (XRD), energy-dispersive spectroscopy (EDS), differential scanning calorimetry, X-ray photoelectron spectroscopy (XPS), and Fourier-transform infrared. The XRD, XPS, and EDS characterizations proved the existence of Ag in the nanofibrous Ag/PVDF composite membranes. The crystallinity degree of PVDF for composite membranes declined with the increase in Ag content. More importantly, the nanofibrous Ag/PVDF composite membranes had obviously higher Rosseland extinction coefficients and lower thermal radiative conductivities in comparison with electrospun PVDF membrane, which demonstrates that such composite membranes with high porosity, low density, and good water vapor permeability are promising thermal insulating materials to block the heat transfer resulting from thermal radiation. In addition, three different methods for surface modification have been used to successfully improve the hydrophobicity of nanofibrous Ag/PVDF composite membranes.

A plasmid-born Rap-Phr system regulates surfactin production, sporulation and genetic competence in the heterologous host, Bacillus subtilis OKB105.

According to the change of environment, soil-dwelling Bacillus species differentiate into distinct subpopulations, such as spores and competent cells. Rap-Phr systems have been found to be involved in this differentiation circuit by interacting with major regulatory proteins, such as Spo0A, ComA, and DegU. In this study, we report that the plasmid-born RapQ-PhrQ system found in Bacillus amyloliquefaciens B3 affects three regulatory pathways in the heterologous host Bacillus subtilis. Expression of rapQ in B. subtilis OKB105 strongly suppressed its sporulation efficiency, transformation efficiency, and surfactin production. Co-expression of phrQ or addition of synthesized PhrQ pentapeptide in vitro could compensate for the suppressive effects caused by rapQ. We also found that expression of rapQ decreased the transcriptional level of the sporulation-related gene spoIIE and surfactin synthesis-related gene srfA; meanwhile, the transcriptional levels of these genes could be rescued by co-expression of phrQ and in vitro addition of PhrQ pentapeptide. Electrophoretic mobility shift (EMSA) result also showed that RapQ could bind to ComA without interacting with ComA binding to DNA, and PhrQ pentapeptide antagonized RapQ activity in vitro. These results indicate that this new plasmid-born RapQ-PhrQ system controls sporulation, competent cell formation, and surfactin production in B. subtilis OKB105.

Plant growth promotion by spermidine-producing Bacillus subtilis OKB105.

The interaction between plants and plant-growth-promoting rhizobacteria (PGPR) is a complex, reciprocal process. On the one hand, plant compounds such as carbohydrates and amino acids serve as energy sources for PGPR. On the other hand, PGPR promote plant growth by synthesizing plant hormones and increasing mineral availability in the soil. Here, we evaluated the growth-promoting activity of Bacillus subtilis OKB105 and identified genes associated with this activity. The genes yecA (encoding a putative amino acid/polyamine permease) and speB (encoding agmatinase) are involved in the secretion or synthesis of polyamine in B. subtilis OKB105. Disruption of either gene abolished the growth-promoting activity of the bacterium, which was restored when polyamine synthesis was complemented. Moreover, high-performance liquid chromatography analysis of culture filtrates of OKB105 and its derivatives demonstrated that spermidine, a common polyamine, is the pivotal plant-growth-promoting compound. In addition, real-time polymerase chain reaction analysis revealed that treatment with B. subtilis OKB105 induced expansin gene (Nt-EXPA1 and Nt-EXPA2) expression and inhibited the expression of the ethylene biosynthesis gene ACO1. Furthermore, enzyme-linked immunosorbent assay analysis showed that the ethylene content in plant root cells decreased in response to spermidine produced by OKB105. Therefore, during plant interactions, OKB105 may produce and secrete spermidine, which induces expansin production and lowers ethylene levels.

Functional transient receptor potential canonical type 1 channels in human atrial myocytes.

Transient receptor potential (TRP) channels are not well understood in human atrium, and the present study was therefore designed to investigate whether TRPC channels would mediate the nonselective cation current reported previously and are involved in the formation of store-operated Ca(2+) entry (SOCE) channels in human atrial myocytes using approaches of whole-cell patch voltage-clamp, RT-PCR, Western blotting, co-immunoprecipitation, and confocal scanning approaches, etc. We found that a nonselective cation current was recorded under K(+)-free conditions in human atrial myocytes, and the current was inhibited by the TRP channel blocker La(3+). Thapsigargin enhanced the current, and its effect was suppressed by La(3+) and prevented by pipette inclusion of anti-TRPC1 antibody. Endothlin-1 and angiotensin II enhanced the current that could be inhibited by La(3+). Gene and protein expression of TRPC1 channels were abundant in human atria. In addition, mRNA and protein of STIM1 and Orai1, components of SOCE channels, were abundantly expressed in human atria. Co-immunoprecipitation analysis demonstrated an interaction of TRPC1 with STIM1 and/or Orai1. Ca(2+) signaling mediated by SOCE channels was detected by a confocal microscopy technique. These results demonstrate the novel evidence that TRPC1 channels not only mediate the nonselective cation current, but also form SOCE channels in human atria as a component. TRPC1 channels can be activated by endothelin-1 or angiotensin II, which may be involved in the atrial electrical remodeling in patients with atrial fibrillation.

Metagenomic analysis reveals specific BTEX degrading microorganisms of a bacterial consortium.

Petroleum hydrocarbon contamination is of environmental and public health concerns due to its toxic components. Bioremediation utilizes microbial organisms to metabolism and remove these contaminants. The aim of this study was to enrich a microbial community and examine its potential to degrade petroleum hydrocarbon. Through successive enrichment, we obtained a bacterial consortium using crude oil as sole carbon source. The 16 S rRNA gene analysis illustrated the structural characteristics of this community. Metagenomic analysis revealed the specific microbial organisms involved in the degradation of cyclohexane and all the six BTEX components, with a demonstration of the versatile metabolic pathways involved in these reactions. Results showed that our consortium contained the full range of CDSs that could potentially degrade cyclohexane, benzene, toluene, and (o-, m-, p-) xylene completely. Interestingly, a single taxon that possessed all the genes involved in either the activation or the central intermediates degrading pathway was not detected, except for the Novosphingobium which contained all the genes involved in the upper degradation pathway of benzene, indicating the synergistic interactions between different bacterial genera during the hydrocarbon degradation.

Acacetin causes a frequency- and use-dependent blockade of hKv1.5 channels by binding to the S6 domain.

We have demonstrated that the natural flavone acacetin selectively inhibits ultra-rapid delayed rectifier potassium current (I(Kur)) in human atria. However, molecular determinants of this ion channel blocker are unknown. The present study was designed to investigate the molecular determinants underlying the ability of acacetin to block hKv1.5 channels (coding I(Kur)) in human atrial myocytes using the whole-cell patch voltage-clamp technique to record membrane current in HEK 293 cells stably expressing the hKv1.5 gene or transiently expressing mutant hKv1.5 genes generated by site-directed mutagenesis. It was found that acacetin blocked hKv1.5 channels by binding to both closed and open channels. The blockade of hKv1.5 channels by acacetin was use- and frequency-dependent, and the IC(50) of acacetin for inhibiting hKv1.5 was 3.5, 3.1, 2.9, 2.1, and 1.7µM, respectively, at 0.2, 0.5, 1, 3, and 4Hz. The mutagenesis study showed that the hKv1.5 mutants V505A, I508A, and V512A in the S6-segment remarkably reduced the channel blocking properties by acacetin (IC(50), 29.5µM for V505A, 19.1µM for I508A, and 6.9µM for V512A). These results demonstrate the novel information that acacetin mainly blocks open hKv1.5 channels by binding to their S6 domain. The use- and rate-dependent blocking of hKv1.5 by acacetin is beneficial for anti-atrial fibrillation.

Functional analysis and application of the cryptic plasmid pBSG3 harboring the RapQ-PhrQ system in Bacillus amyloliquefaciens B3.

This work sequenced and characterized a cryptic plasmid called pBSG3 from wild-type Bacillus amyloliquefaciens B3--a powerful agent for suppression of plant pathogenic organisms. It is an 8439 bp circular molecule, with G+C content of 40.3%. We provide evidence that pBSG3 replicates via the rolling-circle (RC) mechanism and, sequence comparisons place it in the pC194 family of rolling-circle-replicons. The plasmid contains seven putative open reading frames (ORFs), including genes repB3, mobB3, rapQ, phrQ, pgsR, and two unknown ORFs (orf1c and orf2). Our observations reveal that the RapQ-PhrQ (response regulator aspartate phosphatase-phosphatase regulator) system is involved in sporulation and RapQ can delay the onset of sporulation. Two Escherichia coli and Bacillus potential shuttle vectors, pTRD (containing the minimal replicon) and pTRDS (containing the minimal replicon and the single-strand origin) were developed from pBSG3 and tested the stability. Moreover, HpaG(xooc) protein, which can induce disease and insect resistance in plants, was tried to express with the stable vector pTRDS in Bacillus subtilis. In summary, the pBSG3 plasmid containing various genes is not only a candidate tool for vector development in Bacillus genus research but also a potential vehicle for the exchange of genetic elements among Bacillus populations that contributes to the survival of bacilli in natural environments.

[Evolution of Material Metabolism in China's Pulp and Paper Industry].

The pulp and paper industry is an important industry that is closely related to national socioeconomic development. To understand the historical trends of resource consumption and environmental pollution, we conducted an economy-wide material flow analysis and quantitatively evaluated the dynamic characteristics of input-output balances, material metabolism intensity, and resource recycling rate of China's pulp and paper industry, from 2005 to 2017. The results indicate downward trends in the material inputs and outputs of China's pulp and paper industry from 2005 to 2017, with water contributing over 90% of the totals. In recent years, with the continuous optimization of the raw material structure of the paper industry, the proportion of non-wood pulping has dropped from 42% to 13% and has been replaced by mainly waste paper pulping and wood pulping. Resource consumption can still be greatly reduced. In 2017, the amount of direct material input per ton of paper and paperboard had decreased by 67% from 2005 to 26 t. The consumption of fresh water per ton of paper and paperboard dropped by approximately 69% over the study period, whereas the water recycling rate increased significantly, reaching 77% in 2017. At present, the production of paper and paperboard is increasingly dependent on the input of domestic waste paper and imported wood, the proportions of which have increased from 21% and 9% in 2005 to 60% and 31% in 2017, respectively. However, the rate of domestic waste paper recycling is relatively low, and measures such as strengthening the construction of the recycling system and educating the residents about recycling are needed to alleviate the shortage of raw materials caused by restrictions on waste paper imports.

[Concentrations and pollution assessment of mercury in farmland soil of Xinqiao Mining Area of Tongling, Anhui, China.] / é“œé™µæ–°æ¡¥çŸ¿åŒºå‘¨è¾¹å†œç”°åœŸå£¤æ±žå«é‡åˆ†å¸ƒç‰¹å¾åŠå ¶æ±¡æŸ“è¯„ä»·.

To investigate the effects of mining activities on mercury (Hg) enrichment in farmland soil, soil samples were collected from four villages (Xinjian Village, Yehu Village, Xinhu Village and Hucheng Village) in the vicinity of Xinqiao Mining Area, Tongling. Hg concentration was measured by atomic fluorescence spectrophotometer. The geo-accumulation index was used to evaluate the Hg pollution level of the soils. The results showed that average concentration of total Hg in farmland soil was (0.137±0.078) mg·kg-1, which exceeded the background value of soil Hg in Tongling area. The average concentration of Hg in four villages followed the order of Xinjian Village (0.221 mg·kg-1)>Xinhu Village (0.118 mg·kg-1)>Yehu Village(0.115 mg·kg-1)>Hucheng Village (0.096 mg·kg-1). Moreover, the average Hg concentration of different forms in Xinjian Village followed the order of residue (0.036 mg·kg-1) > alkali soluble (0.031 mg·kg-1) > hydrogen peroxide soluble (0.022 mg·kg-1)> acid soluble (0.020 mg·kg-1)> water soluble (0.012 mg·kg-1). The distance from the mining area was the main factor affecting the distribution of soil Hg concentration in farmlands. The contaminated Xinqiao River, to some degree, had exa-cerbated soil Hg pollution. Soil organic matter affected the accumulation and transformation of total Hg and hydrogen peroxide Hg in the farmlands. The order of the geo-accumulation index followed as Xinjian Village(1.559) >Xinhu Village(0.654) >Yehu Village(0.616) >Hucheng Village(0.356). The pollution level of farmland soil in Xinjian Village belonged to middle level of Hg pollution,which deserved more attention.

The effectiveness and safety of dual antiplatelet therapy in ischemic cerebrovascular disease with intracranial and extracranial arteriostenosis in Chinese patients: A randomized and controlled trail.

BACKGROUND: There are limited data on the effect of dual antiplatelet treatment with clopidogrel plus aspirin in patients with ischemic cerebrovascular disease and intracranial and extracranial arteriostenosis. The aim of our study was to evaluate the efficacy and safety of aspirin plus clopidogrel in the treatment of ischemic cerebrovascular disease with intracranial and extracranial arteriostenosis. METHODS: Patients with clinically evident acute cerebral infarction or transient ischemic attack combined with intracranial and extracranial arteriostenosis (greater than 50%) who were unsuitable or reluctance to perform stent implantation were enrolled in this study. We randomly assigned these patients to receive clopidogrel (75 or 50 mg) plus aspirin (100 mg) or aspirin (100 mg) once daily through 90 days, and followed them for 90 days. We examined the main endpoints including the recurrence of stroke, death from cardiovascular causes, and bleeding events. RESULTS: In all, 200 patients were recruited and followed for 90 days. Ischemic stroke occurred in 6 patients (9.1%) treated with 50 mg clopidogrel and aspirin, 6 patients (9.1%) receiving 75 mg clopidogrel and aspirin, whereas 19 patients (27.9%) in the aspirin group (aspirin alone vs copidogrel 50 mg plus aspirin; 95% confidence intervals 1.704-23.779, P < 0.05; aspirin alone vs copidogrel 75 mg plus aspirin; 95% confidence intervals 1.190-13.240, P < 0.05). There were more hemorrhagic events among recipients (3 patients [2.3%]) in the copidogrel plus aspirin group than aspirin recipients (0 patient [0%]), including 1 subcutaneous hemorrhage in the group of 50 mg clopidogrel and aspirin, doubling the number of nasal and gum bleeding in the group of 75 mg clopidogrel and aspirin (P > 0.05). No intracranial hemorrhage and gastro-intestinal hemorrhage occurred in these 3 groups. CONCLUSION: Accordingly, 50 mg clopidogrel plus aspirin, and 75 mg clopidogrel plus aspirin were all superior to aspirin alone as stroke prevention in patients with cerebral infarction or transient ischemic attack combined with intracranial and extracranial arteriostenosis. The effect of secondary stroke prevention was similar between 50 mg clopidogrel plus aspirin and 75 mg clopidogrel plus aspirin. The therapy of 75 mg clopidogrel plus aspirin resulted in a worrisome tread in bleeding events.

Water-soluble acacetin prodrug confers significant cardioprotection against ischemia/reperfusion injury.

The morbidity and mortality of patients with ischemic cardiomyopathy resulted from ischemia/reperfusion injury are very high. The present study investigates whether our previously synthesized water-soluble phosphate prodrug of acacetin was cardioprotective against ischemia/reperfusion injury in an in vivo rat model. We found that intravenous administration of acacetin prodrug (10 mg/kg) decreased the ventricular arrhythmia score and duration, reduced ventricular fibrillation and infarct size, and improved the impaired heart function induced by myocardial ischemia/reperfusion injury in anesthetized rats. The cardioprotective effects were further confirmed with the parent compound acacetin in an ex vivo rat regional ischemia/reperfusion heart model. Molecular mechanism analysis revealed that acacetin prevented the ischemia/reperfusion-induced reduction of the anti-oxidative proteins SOD-2 and thioredoxin, suppressed the release of inflammation cytokines TLR4, IL-6 and TNFα, and decreased myocyte apoptosis induced by ischemia/reperfusion. Our results demonstrate the novel evidence that acacetin prodrug confer significant in vivo cardioprotective effect against ischemia/reperfusion injury by preventing the reduction of endogenous anti-oxidants and the release of inflammatory cytokines, thereby inhibiting cardiomyocytes apoptosis, which suggests that the water-soluble acacetin prodrug is likely useful in the future as a new drug candidate for treating patients with acute coronary syndrome.

[Soil nitrogen content and enzyme activities in rhizosphere and non-rhizosphere of summer maize under different nitrogen application rates.] / æ–½æ°®é‡å¯¹å¤çŽ‰ç±³æ ¹é™ å’Œéžæ ¹é™ åœŸå£¤é ¶æ´»æ€§åŠæ°®å«é‡çš„å½±å“.

A field experiment was conducted on fluvo-aquic soil in the North China Plain to study the effects of nitrogen application rate on soil nitrogen contents and enzyme activities in rhizosphere and non-rhizosphere of summer maize. The results showed that the soil enzyme activities under different nitrogen application rates showed similar seasonal patterns. In comparison to no nitrogen ferti-lizer treatment, all nitrogen application treatments significantly increased NO3--N contents in rhizosphere and non-rhizosphere soils, NH4+-N content in rhizosphere soil and the activities of ß-N-acetylglucosaminidase, ß-glucosidase, ß-xylosidase and Cellobiohyrolase. During the whole summer maize growing season, the NO3--N content in non-rhizosphere soil was significantly higher than that in rhizosphere soil. The NH4+-N content in non-rhizosphere soil was also significantly higher than that in rhizosphere soil at filling stage but significantly lower at seedling and maturity stages. Furthermore, soil enzyme activities in rhizosphere soil were significantly higher than those in non-rhizosphere soil. Effect of nitrogen application on soil organic carbon content was not significant. Soil total nitrogen content increased significantly when the nitrogen application rate was 0-180 kg·hm-2 but decreased significantly when the rate was higher than 180 kg·hm-2. Generally, a proper rate of nitrogen fertilizer application could significantly increase soil enzyme activities and total nitrogen content, and then improve soil biochemistry properties.

Control of the Metal-Insulator Transition at Complex Oxide Heterointerfaces through Visible Light.

The coupling of the localized surface plasmon resonance of Au nanoparticles is utilized to deliver a visible-light stimulus to control conduction at the LaAlO3 /SrTiO3 interface. A giant photoresponse and the controllable metal-insulator transition are characterized at this heterointerface. This study paves a new route to optical control of the functionality at the heterointerfaces.

Novel Routes for Improving Biocontrol Activity of Bacillus Based Bioinoculants.

Biocontrol (BC) formulations prepared from plant-growth-promoting bacteria are increasingly applied in sustainable agriculture. Especially inoculants prepared from endospore-forming Bacillus strains have been proven as efficient and environmental-friendly alternative to chemical pesticides due to their long shelf life, which is comparable with that of agrochemicals. However, these formulations of the first generation are sometimes hampered in their action and do not fulfill in each case the expectations of the appliers. In this review we use the well-known plant-associated Bacillus amyloliquefaciens type strain FZB42 as example for the successful application of different techniques offered today by comparative, evolutionary and functional genomics, site-directed mutagenesis and strain construction including marker removal, for paving the way for preparing a novel generation of BC agents.

[Effects of long-term tillage measurements on soil aggregate characteristic and microbial diversity].

Soil aggregate stability and microbial diversity play important roles in nutrient recycling in soil-crop systems. This study investigated the impacts of different soil tillage systems on soil aggregation and soil microbial diversity based on a 15-year long-term experiment on loess soil in Henan Province of China. Treatments included reduced tillage (RT), no-tillage (NT), sub-soiling with mulch (SM), wheat-peanut two crops (TC), and conventional tillage (CT). Soil aggregates were separated by wet sieving method, and soil microbial (bacterial, archaeal and fungal) diversity was examined by using the techniques of denaturing gradient gel electrophoresis (PCR-DGGE) analysis. The results showed that water-stable macroaggregates concent (R0.25) and the mean mass diameter (MWD) in the surface soil significantly increased under NT, SM and TC, R0.25 increased by 21.5%, 29.5% and 69.2%, and MWD increased by 18.0%, 12.2% and 50.4%, respectively, as compared with CT. Tillage practices caused changes in bacterial, archaeal and fungal community compositions. With NT, SM and TC, the bacterial, archaeal and fungal Shannon indices increased by 0.3%, 0.3%, and 0.6%, and 20.2%, 40.5%, and 49.1%, and 23.7%, 19.5%, and 25.8%, respectively, as compared with CT. Both bacterial and archaeal Shannon indices were significantly correlated with the indices of R0.25 and MWD, while the fungal Shannon index was not significantly correlated with these two indices. In conclusion, conservation tillage, including NT and SM, and crop rotation, including TC, improved soil aggregation and soil microbial diversity.

Properties and molecular determinants of the natural flavone acacetin for blocking hKv4.3 channels.

The natural flavone acacetin has been demonstrated to inhibit transient outward potassium current (Ito) in human atrial myocytes. However, the molecular determinants of acacetin for blocking Ito are unknown. The present study was designed to investigate the properties and molecular determinants of this compound for blocking hKv4.3 channels (coding Ito) stably expressed in HEK 293 cells using the approaches of whole-cell patch voltage-clamp technique and mutagenesis. It was found that acacetin inhibited hKv4.3 current by binding to both the closed and open channels, and decreased the recovery from inactivation. The blockade of hKv4.3 channels by acacetin was use- and frequency-dependent, and IC50s of acacetin for inhibiting hKv4.3 were 7.9, 6.1, 3.9, and 3.2 µM, respectively, at 0.2, 0.5, 1, and 3.3 Hz. The mutagenesis study revealed that the hKv4.3 mutants T366A and T367A in the P-loop helix, and V392A, I395A and V399A in the S6-segment had a reduced channel blocking efficacy of acacetin (IC50, 44.5 µM for T366A, 25.8 µM for T367A, 17.6 µM for V392A, 16.2 µM for I395A, and 19.1 µM for V399A). These results demonstrate the novel information that acacetin may inhibit the closed channels and block the open state of the channels by binding to their P-loop filter helix and S6 domain. The use- and rate-dependent blocking of hKv4.3 by acacetin is likely beneficial for managing atrial fibrillation.

Correction: Properties and Molecular Determinants of the Natural Flavone Acacetin for Blocking hKv4.3 Channels.

[This corrects the article DOI: 10.1371/journal.pone.0057864.].