Outer membrane vesicles produced by Gram-negative bacteria have been studied for half a century but the possibility that Gram-positive bacteria secrete extracellular vesicles (EVs) was not pursued ...until recently due to the assumption that the thick peptidoglycan cell wall would prevent their release to the environment. However, following their discovery in fungi, which also have cell walls, EVs have now been described for a variety of Gram-positive bacteria. EVs purified from Gram-positive bacteria are implicated in virulence, toxin release, and transference to host cells, eliciting immune responses, and spread of antibiotic resistance. Listeria monocytogenes is a Gram-positive bacterium that causes listeriosis. Here we report that L. monocytogenes produces EVs with diameters ranging from 20 to 200 nm, containing the pore-forming toxin listeriolysin O (LLO) and phosphatidylinositol-specific phospholipase C (PI-PLC). Cell-free EV preparations were toxic to mammalian cells, the murine macrophage cell line J774.16, in a LLO-dependent manner, evidencing EV biological activity. The deletion of plcA increased EV toxicity, suggesting PI-PLC reduced LLO activity. Using simultaneous metabolite, protein, and lipid extraction (MPLEx) multiomics we characterized protein, lipid, and metabolite composition of bacterial cells and secreted EVs and found that EVs carry the majority of listerial virulence proteins. Using immunogold EM we detected LLO at several organelles within infected human epithelial cells and with high-resolution fluorescence imaging we show that dynamic lipid structures are released from L. monocytogenes during infection. Our findings demonstrate that L. monocytogenes uses EVs for toxin release and implicate these structures in mammalian cytotoxicity.
The formation of patterns after the evaporation of colloidal droplets deposited on a solid surface is an everyday natural phenomenon. During the past two decades, this topic has gained broader ...audience due to its numerous applications in biomedicine, nanotechnology, printing, coating, etc. This paper presents a detailed review of the experimental studies related to the formation of various deposition patterns from dried droplets of complex fluids (i.e., nanofluids, polymers). First, this review presents the fundamentals of sessile droplet evaporation including evaporation modes and internal flow fields. Then, the most observed dried patterns are presented and the mechanisms behind them are discussed. The review ends with the categorisation and exhaustive investigation of a wide range of factors affecting pattern formation.
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•A review of the studies related to the formation of various deposition patterns from dried colloidal droplets is presented.•The most observed dried patterns are presented and the mechanisms behind them are discussed.•The effects of key factors on desiccation patterns are elucidated.
Epigenetic modifications such as DNA methylation contribute to progression of hepatitis C virus (HCV) infection to life‐threatening hepatocellular carcinoma (HCC) by promoting the silencing of tumor ...suppressor genes through DNA hypermethylation and by causing genomic instability through global hypomethylation. However few studies have addressed the promoter region hypomethylation status of the oncogenes involved in HCV derived HCC. In this study, we analyzed the promoter region methylation pattern of RAS oncogenes (HRAS, KRAS, and NRAS) using methylation‐specific PCR for 50 chronic HCV patients infected with genotype 3a (27 HCC patients and 23 control non‐HCC patients). Methylation‐specific polymerase chain reaction analysis revealed that the NRAS oncogene promoter (P = .0025) was significantly hypomethylated in HCC patients compared to the non‐HCC patients suggesting its contribution to the progression of HCV towards HCC. To identify the agent for alteration in the RAS oncogene expression, 7 HCV genes were expressed in the Huh‐7 cell line followed by measurement of the NRAS expression level in Huh‐7 by a quantitative real‐time polymerase chain reaction. An increase in the messenger RNA level of the NRAS gene was detected when Huh‐7 were transfected with Core, NS5a, and NS2 genes. Our findings suggest the involvement of NRAS oncogene in the pathogenesis of HCV3a derived HCC in Pakistani population and also identifies the HCV genes responsible for its enhanced expression. Our study raises the hypothesis that a single HCV gene may increase the chances of malignancy. Therefore, our study may have identified a useful epigenetic biomarker of HCC progression in HCV patients and may help to develop novel diagnostic tools.
This study investigates pattern formation during evaporation of water-based nanofluid sessile droplets placed on a smooth silicon surface at various temperatures. An infrared thermography technique ...was employed to observe the temperature distribution along the air–liquid interface of evaporating droplets. In addition, an optical interferometry technique is used to quantify and characterize the deposited patterns. Depending on the substrate temperature, three distinctive deposition patterns are observed: a nearly uniform coverage pattern, a “dual-ring” pattern, and multiple rings corresponding to “stick–slip” pattern. At all substrate temperatures, the internal flow within the drop builds a ringlike cluster of the solute on the top region of drying droplets, which is found essential for the formation of the secondary ring deposition onto the substrate for the deposits with the “dual-ring” pattern. The size of the secondary ring is found to be dependent on the substrate temperature. For the deposits with the rather uniform coverage pattern, the ringlike cluster of the solute does not deposit as a distinct secondary ring; instead, it is deformed by the contact line depinning. In the case of the “stick–slip” pattern, the internal flow behavior is complex and found to be vigorous with rapid circulating flow which appears near the edge of the drop.
Understanding nanoscale thermal transport is of substantial importance for designing contemporary semiconductor technologies. Heat removal from small sources is well established to be severely ...impeded compared to diffusive predictions due to the ballistic nature of the dominant heat carriers. Experimental observations are commonly interpreted through a reduction of effective thermal conductivity, even though most measurements only probe a single aggregate thermal metric. Here, we employ thermoreflectance thermal imaging to directly visualise the 2D temperature field produced by localised heat sources on InGaAs with characteristic widths down to 100 nm. Besides displaying effective thermal performance reductions up to 50% at the active junctions in agreement with prior studies, our steady-state thermal images reveal that, remarkably, 1-3 μm adjacent to submicron devices the crosstalk is actually reduced by up to fourfold. Submicrosecond transient imaging additionally shows responses to be faster than conventionally predicted. A possible explanation based on hydrodynamic heat transport, and some open questions, are discussed.
In this study, pattern formation during evaporation of bidispersed drops (containing 1 and 3.2 μm particles) placed on a smooth substrate at different temperatures is investigated. Five distinctive ...deposition patterns are observed depending on the substrate temperature: a relatively uniform pattern enclosed by a disk-shaped ring, a nearly nonuniform pattern inside a thick outer ring, a “dual-ring” pattern, a “rose-like” pattern, and a set of concentric rings corresponding to the “stick–slip” pattern. At drops edge, the particle size effect leads to the formation of three rings: an outermost ring formed by the nonvolatile additives smaller than 1 μm, a middle ring built by particles with size of 1 μm, and an innermost ring formed by the mixture of 1 and 3.2 μm. For temperatures between 64 and 99 °C, the depinning of the contact line causes the same particle sorting at the other deposition lines in the interior of the drop. However, the width of the zone between the outermost ring and the middle ring at the initial edge of the drop is found to be smaller than that at the other deposition lines. The size of the width is found to be dependent on the contact angle. Particle velocity is measured by tracking particles during the evaporation. It is shown that particle velocity slightly increases with time, but it rapidly increases at the last stage of the drying process, known as “rush-hour” behavior. The sudden change in the increase of the velocity occurs between the normalized time of 0.7 and 0.8 for temperatures from 22 to 81 °C. The increasing trend of velocity with time matches well with the theoretical model. The tracer particles are also used to measure the distance between the contact line and the nearest turning point of those particles return back toward the top of the drop due to the inward Marangoni flow. It is found that this distance decreases with increasing the substrate temperature.
Patterns from dried water-butanol binary-based nanofluid drops Parsa, Maryam; Boubaker, Riadh; Harmand, Souad ...
Journal of nanoparticle research : an interdisciplinary forum for nanoscale science and technology,
08/2017, Letnik:
19, Številka:
8
Journal Article
Odprti dostop
In this work, the behavior of evaporating binary-based nanofluid sessile droplets deposited on a smooth silicon substrate at different temperatures is explored. The formation of deposition patterns ...during the evaporation is studied by tracking particle clusters using optical microscopy. Similarly to evaporation of pure water-based nanofluid droplets, three distinctive deposition patterns are left behind the complete evaporation: a relatively uniform coverage pattern (on a nonheated surface); a “dual-ring” pattern at higher temperature, i.e., 81 °C; and a “stick-slip” pattern at 99 °C. Infrared thermography technique was employed to visualize the evolution of thermal patterns on the surface of the drying droplets. Thermal imaging shows that the evaporation of binary mixture droplets can be classified into three regimes. In the first regime, multiple convection vortices can be observed at the droplet interface, corresponding to the chaotic motion of nanoparticles captured by video microscopy. This flow regime is believed to be driven by surface tension gradients arising from local concentration gradients. As evaporation time proceeds, the number of convection vortices decreases in regime I, and a few numbers of those are left in the second regime. The flow slows down and a rapid transition (the second regime) occurs; this is followed by the last regime. At the two highest temperatures of 81 and 99 °C, the end of the transition regime is associated with the existence of two distinctive counter-rotating vortices. For the third regime, the results from both infrared thermography and video microscopy show identical behavior to those of water-based nanofluid droplets at the same substrate temperatures. This reveals that most of the more volatile component (not all) has evaporated after the first two regimes; hence, the solutal Marangoni driven by local concentration gradients is significantly weakened and has no further role in the flow structure in the last regime. Instead, the thermocapillary effect and continuity are the underlying reasons for the internal flow structure of the evaporating droplets during the last regime.
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The growing population increases the need to develop advanced biological methods for utilizing renewable and sustainable resources to produce environmentally friendly biofuels. Currently, energy ...resources are limited for global demand and are constantly depleting and creating environmental problems. Some higher chain alcohols, like butanol and ethanol, processing similar properties to gasoline, can be alternate sources of biofuel. However, the industrial production of these alcohols remains challenging because they cannot be efficiently produced by microbes naturally. Therefore, butanol is the most interesting biofuel candidate with a higher octane number produced naturally by microbes through Acetone–Butanol–Ethanol fermentation. Feedstock selection as the substrate is the most crucial step in biobutanol production. Lignocellulosic biomass has been widely used to produce cellulosic biobutanol using agricultural wastes and residue. Specific necessary pretreatments, fermentation strategies, bioreactor designing and kinetics, and modeling can also enhance the efficient production of biobutanol. The recent genetic engineering approaches of gene knock in, knock out, and overexpression to manipulate pathways can increase the production of biobutanol in a user friendly host organism. So far various genetic manipulation techniques like antisense RNA, TargeTron Technology and CRISPR have been used to target Clostridium acetobutylicum for biobutanol production. This review summarizes the recent research and development for the efficient production of biobutanol in various aspects.
Omega-3 fatty acids, including docosahexaenoic acid (DHA), eicosapentaenoic acid (EPA), and α-linolenic acid (ALA), are essential polyunsaturated fatty acids with diverse health benefits. The limited ...conversion of dietary DHA necessitates its consumption as food supplements. Omega-3 fatty acids possess anti-arrhythmic and anti-inflammatory capabilities, contributing to cardiovascular health. Additionally, DHA consumption is linked to improved vision, brain, and memory development. Furthermore, omega-3 fatty acids offer protection against various health conditions, such as celiac disease, Alzheimer’s, hypertension, thrombosis, heart diseases, depression, diabetes, and certain cancers. Fish oil from pelagic cold-water fish remains the primary source of omega-3 fatty acids, but the global population burden creates a demand–supply gap. Thus, researchers have explored alternative sources, including microbial systems, for omega-3 production. Microbial sources, particularly oleaginous actinomycetes, microalgae like
Nannochloropsis
and among microbial systems,
Thraustochytrids
stand out as they can store up to 50% of their dry weight in lipids. The microbial production of omega-3 fatty acids is a potential solution to meet the global demand, as these microorganisms can utilize various carbon sources, including organic waste. The biosynthesis of omega-3 fatty acids involves both aerobic and anaerobic pathways, with bacterial polyketide and PKS-like PUFA synthase as essential enzymatic complexes. Optimization of physicochemical parameters, such as carbon and nitrogen sources, pH, temperature, and salinity, plays a crucial role in maximizing DHA production in microbial systems. Overall, microbial sources hold significant promise in meeting the global demand for omega-3 fatty acids, offering an efficient and sustainable solution for enhancing human health.
Annexins are multifunctional proteins that bind to phospholipid membranes in a calcium-dependent manner. Annexins play a myriad of critical and well-characterized roles in mammals, ranging from ...membrane repair to vesicular secretion. The role of annexins in the kingdoms of bacteria, protozoa and fungi have been largely overlooked. The fact that there is no known homologue of annexins in the yeast model organism Saccharomyces cerevisiae may contribute to this gap in knowledge. However, annexins are found in most medically important fungal pathogens, with the notable exception of Candida albicans. In this study we evaluated the function of the one annexin gene in Cryptococcus neoformans, a causative agent of cryptococcosis. This gene CNAG_02415, is annotated in the C. neoformans genome as a target of calcineurin through its transcription factor Crz1, and we propose to update its name to cryptococcal annexin, AnnexinC1. C. neoformans strains deleted for AnnexinC1 revealed no difference in survival after exposure to various chemical stressors relative to wild-type strain, as well as no major alteration in virulence or mating. The only alteration observed in strains deleted for AnnexinC1 was a small increase in the titan cells' formation in vitro. The preservation of annexins in many different fungal species suggests an important function, and therefore the lack of a strong phenotype for annexin-deficient C. neoformans indicates either the presence of redundant genes that can compensate for the absence of AnnexinC1 function or novel functions not revealed by standard assays of cell function and pathogenicity.
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