Subtilisin-like proteases from Fusarium graminearum induce plant cell death and contribute to virulence.

Fusarium head blight (FHB), caused by Fusarium graminearum, causes huge annual economic losses in cereal production. To successfully colonize host plants, pathogens secrete hundreds of effectors that interfere with plant immunity and facilitate infection. However, the roles of most secreted effectors of F. graminearum in pathogenesis remain unclear. We analyzed the secreted proteins of F. graminearum and identified 255 candidate effector proteins by liquid chromatography-mass spectrometry (LC-MS). Five subtilisin-like family proteases (FgSLPs) were identified that can induce cell death in Nicotiana benthamiana leaves. Further experiments showed that these FgSLPs induced cell death in cotton (Gossypium barbadense) and Arabidopsis (Arabidopsis thaliana). A signal peptide and light were not essential for the cell death-inducing activity of FgSLPs. The I9 inhibitor domain and the entire C-terminus of FgSLPs were indispensable for their self-processing and cell death-inducing activity. FgSLP-induced cell death occurred independent of the plant signal transduction components BRI-ASSOCIATED KINASE 1 (BAK1), SUPPRESSOR OF BIR1 1 (SOBIR1), ENHANCED DISEASE SUSCEPTIBILITY 1 (EDS1), and PHYTOALEXIN DEFICIENT 4 (PAD4). Reduced virulence was observed when FgSLP1 and FgSLP2 were simultaneously knocked out. This study reveals a class of secreted toxic proteins essential for F. graminearum virulence.

Prevalence and resistance characteristics of multidrug-resistant Streptococcus pneumoniae isolated from the respiratory tracts of hospitalized children in Shenzhen, China.

Background: PCV13 introduction in China has led to a significant reduction of vaccine serotype Streptococcus pneumoniae. However, non-vaccine serotypes with highly resistance and invasiveness were often reported in the post-pneumococcal conjugate vaccine era and there was regional differences. Methods: A total of 669 S. pneumoniae strains were collected from the respiratory tracts of hospitalized children at Shenzhen Children's Hospital in 2021 and 2022. Antimicrobial resistance (AMR) characteristics were assessed through antibiotic susceptibility testing performed with the VITEK 2 compact system. AMR genes and single nucleotide polymorphisms (SNPs) in pbp1a, pbp2b, and pbp2x were identified via analysis of whole genome sequencing data. Statistical examination of the data was conducted employing chi-square and Fisher's exact tests. Results: We found that non-vaccine serotypes strains had accounted for 46.6% of all the pneumococcal isolated strains. The most common non-vaccine serotype is 23A, with a prevalence rate of 8.9%, followed by 15A (6.6%), 6E (5.7%), 34 (3.2%), and 15B (2.9%). The multidrug resistance rates (MDR) of vaccine serotypes were 19F (99.36%), 19A (100%), 23F (98.08%), 6B (100%), and 6C (100%). Meanwhile, the MDR of non-vaccine serotypes were 15B (100.00%), 6E (100%), 15C (100%), 34 (95.24%), and 23A (98.31%). Resistance rates of 6E to more than six antibiotic classes reached 89.47%, which is similar to 19F (83.33%) and 19A (90%). Unique resistance profiles were also identified for non-vaccine serotypes, including significantly higher resistance to chloramphenicol in 6E, 15B, and 15C than in 19F and 19A. Furthermore, through genome sequencing, we revealed strong correlation of cat-TC with chloramphenicol resistance, patA/patB with tetracycline resistance, ermB and pmrA with erythromycin resistance. Conclusion: The introduction of PCV13 into China from 2017 has led to a shift in the dominant composition of pneumococcal strains. There has been a notable rise and spread of multidrug-resistant non-vaccine serotypes among children. Specifically, the non-vaccine serotype 6E, which was not widely reported in China previously, has emerged. To comprehend the resistance mechanisms, it is crucial to further investigate the molecular and genetic characteristics of these non-vaccine serotypes.

Transcriptome Profile of Fusarium graminearum Treated by Putrescine.

Fusarium graminearum (F. graminearum) is the main pathogen of Fusarium head blight (FHB) in wheat, barley, and corn. Deoxynivalenol (DON), produced by F. graminearum, is the most prevalent toxin associated with FHB. The wheat defense compound putrescine can promote DON production during F. graminearum infection. However, the underlying mechanisms of putrescine-induced DON synthesis are not well-studied. To investigate the effect of putrescine on the global transcriptional regulation of F. graminearum, we treated F. graminearum with putrescine and performed RNA deep sequencing. We found that putrescine can largely affect the transcriptome of F. graminearum. Gene ontology (GO) and KEGG enrichment analysis revealed that having a large amount of DEGs was associated with ribosome biogenesis, carboxylic acid metabolism, glycolysis/gluconeogenesis, and amino acid metabolism pathways. Co-expression analysis showed that 327 genes had similar expression patterns to FgTRI genes and were assigned to the same module. In addition, three transcription factor genes were identified as hub genes in this module, indicating that they may play important roles in DON synthesis. These results provide important clues for further analysis of the molecular mechanisms of putrescine-induced DON synthesis and will facilitate the study of the pathogenic mechanisms of FHB.

Separation and identification of polymeric dispersants in detergents by two-dimensional liquid chromatography.

Polymeric dispersants are an important ingredient in many consumer products. Their separations and identifications in final product formulation can be very challenging due to the presence of multiple polymeric dispersants at different levels and the presence of other polymeric and small-molecule components. In this study, using nearly comprehensive two-dimensional liquid chromatography (2D-LC), various water-soluble polymer and co-polymer dispersants were separated with aqueous size exclusion chromatography (SEC) in the first dimension (1D) and gradient elution reversed-phase liquid chromatography (RPLC) in the second dimension (2D). Detection of the polymeric dispersants was accomplished by evaporative light scattering detector (ELSD). A large ID (8.0 mm) SEC column used in common one-dimensional SEC practices was directly adopted in the 2D setup for rapid method development. A close representation of fully comprehensive 2D separation was achieved even with 60% of 1D eluent diverted to waste, demonstrating the flexibility and versatility of having SEC in 1D for two dimensional separation of polymers. Important method parameters, such as 2D column dimensions and flow rate, gradient conditions, and buffer pH were studied. Practical aspects of routine industrial applications such as solvent consumption and analysis time were also considered. This method was exploited for quick identification of polymeric dispersants in commercial detergent samples. Nine detergent samples were screened and polymeric dispersants and additional polymer features were detected in the samples.

Viscoelastic diamine surfactant for stable carbon dioxide/water foams over a wide range in salinity and temperature.

HYPOTHESIS: The viscosity and stability of CO2/water foams at elevated temperature can be increased significantly with highly viscoelastic aqueous lamellae. The slow thinning of these viscoelastic lamellae leads to greater foam stability upon slowing down Ostwald ripening and coalescence. In the aqueous phase, the viscoelasticity may be increased by increasing the surfactant tail length to form more entangled micelles even at high temperatures and salinity. EXPERIMENTS: Systematic measurements of the steady state shear viscosity of aqueous solutions of the diamine surfactant (C16-18N(CH3)C3N(CH3)2) were conducted at varying surfactant concentrations and salinity to determine the parameters for formation of entangled wormlike micelles. The apparent viscosity and stability of CO2/water foams were compared for systems with viscoelastic entangled micellar aqueous phases relative to those with much less viscous spherical micelles. FINDINGS: We demonstrated for the first time stable CO2/water foams at temperatures up to 120 °C and CO2 volumetric fractions up to 0.98 with a single diamine surfactant, C16-18N(CH3)C3N(CH3)2. The foam stability was increased by increasing the packing parameter of the surfactant with a long tail and methyl substitution on the amine to form entangled viscoelastic wormlike micelles in the aqueous phase. The foam was more viscous and stable compared to foams with spherical micelles in the aqueous lamellae as seen with C12-14N(EO)2 and C16-18N(EO)C3N(EO)2.

Phase behavior and interfacial properties of a switchable ethoxylated amine surfactant at high temperature and effects on CO2-in-water foams.

The interfacial properties for surfactants at the supercritical CO2-water (C-W) interface at temperatures above 80°C have very rarely been reported given limitations in surfactant solubility and chemical stability. These limitations, along with the weak solvent strength of CO2, make it challenging to design surfactants that adsorb at the C-W interface, despite the interest in CO2-in-water (C/W) foams (also referred to as macroemulsions). Herein, we examine the thermodynamic, interfacial and rheological properties of the surfactant C12-14N(EO)2 in systems containing brine and/or supercritical CO2 at elevated temperatures and pressures. Because the surfactant is switchable from the nonionic state to the protonated cationic state as the pH is lowered over a wide range in temperature, it is readily soluble in brine in the cationic state below pH 5.5, even up to 120°C, and also in supercritical CO2 in the nonionic state. As a consequence of the affinity for both phases, the surfactant adsorption at the CO2-water interface was high, with an area of 207Å(2)/molecule. Remarkably, the surfactant lowered the interfacial tension (IFT) down to ∼5mN/m at 120°C and 3400 psia (23MPa), despite the low CO2 density of 0.48g/ml, indicating sufficient solvation of the surfactant tails. The phase behavior and interfacial properties of the surfactant in the cationic form were favorable for the formation and stabilization of bulk C/W foam at high temperature and high salinity. Additionally, in a 1.2 Darcy glass bead pack at 120°C, a very high foam apparent viscosity of 146 cP was observed at low interstitial velocities given the low degree of shear thinning. For a calcium carbonate pack, C/W foam was formed upon addition of Ca(2+) and Mg(2+) in the feed brine to keep the pH below 4, by the common ion effect, in order to sufficiently protonate the surfactant. The ability to form C/W foams at high temperatures is of interest for a variety of applications in chemical synthesis, separations, materials science, and subsurface energy production.

Modified montmorillonite clay microparticles for stable oil-in-seawater emulsions.

Environmentally benign clay particles are of great interest for the stabilization of Pickering emulsions. Dodecane-in-synthetic seawater (SSW) emulsions formed with montmorillonite (MMT) clay microparticles modified with bis(2-hydroxyethyl)oleylamine were stable against coalescence, even at clay concentrations down to 0.1% w/v. Remarkably, as little as 0.001% w/v surfactant lowered the hydrophilicity of the clay to a sufficient level for stabilization of oil-in-SSW emulsions. The favorable effect of SSW on droplet size reduction and emulsion stability enhancement is hypothesized to be due to reduced electrostatic repulsion between adsorbed clay particles and a consequent increase in the continuous phase (an aqueous clay suspension) viscosity. Water/oil (W/O) emulsions were inverted to O/W either by decreasing the mass ratio of surfactant-to-clay (transitional inversion) or by increasing the water volume fraction (catastrophic inversion). For both types of emulsions, coalescence was minimal and the sedimentation or creaming was highly correlated with the droplet size. For catastrophic inversions, the droplet size of the emulsions was smaller in the case of the preferred curvature. Suspensions of concentrated clay in oil dispersions in the presence of surfactant were stable against settling. The mass transfer pathways during emulsification of oil containing the clay particles were analyzed on the droplet size/stability phase diagrams to provide insight for the design of dispersant systems for remediating surface and subsurface oceanic oil spills.

Nanoparticle-stabilized carbon dioxide-in-water foams with fine texture.

The concept of hydrophilic/CO(2)-philic balance (HCB) was extended to describe stabilization of carbon dioxide-in-water (C/W) foams (also called emulsions) with silica nanoparticles adsorbed at the CO(2)-water interface. Opaque, white C/W foams (bubble diameter <100 µm) were generated with either PEG-coated silica or methylsilyl modified silica nanoparticles in a beadpack with CO(2) densities between 0.2 and 0.9 g mL(-1). For methylsilyl modified silica nanoparticles, 50% SiOH modification provided an optimal HCB for generation and stabilization of viscous C/W foams with high stability. The apparent viscosity measured with a capillary tube viscometer reached 120-fold that of a CO(2)-water mixture without nanoparticles, a consequence of the small bubble size and the energy required to deform a high density of aqueous lamellae between CO(2) bubbles. Air-in-water (A/W) foams stabilized with nanoparticles were used to gain insight into the relationship between nanoparticle surface properties and adsorption of the nanoparticles at various types of interfaces. With suitable nanoparticles, A/W foams were stable for at least 7 days and C/W foams were stable for at least 23 h. The ability to achieve long term stability for nanoparticle stabilized C/W foams could offer an alternative to conventional surfactants, which are known to have much lower adsorption energies.

Graphene oxide nanoplatelet dispersions in concentrated NaCl and stabilization of oil/water emulsions.

Stable dispersions of graphene oxide nanoplatelets were formed in water at pH 2-10 even with 5 wt% NaCl. For these conditions, oil-in-water emulsions stabilized with graphene oxide nanoplatelets remained partially stable for 1 year. The droplet sizes were as small as ~1 µm with a low nanoplatelet concentration of 0.2 wt%. The emulsions were stable even for nanoplatelet concentrations down to 0.001 wt%. The stabilities of the emulsions even at high salinity may be attributed to the high anion density at the graphene oxide nanoplatelet edges which protrude into the water phase. Furthermore, the graphene oxide nanoplatelets are shown to adsorb on the surfaces of the oil droplets. The conceptual picture of graphene oxide nanoplatelets adsorbed to a greater extent on the water side of the oil/water interface, along with the high density of anions on their edges, cause the oil/water interface to curve about the oil phase, resulting in oil-in-water emulsion droplets. The dispersion stability with a very small amount of graphene oxide-based stabilizer, offers an intriguing opportunity for applications including CO2 sequestration and enhanced oil recovery in deep subsurface formations, which generally contain high-salinity brines.