Single-cell level LasR-mediated quorum sensing response of Pseudomonas aeruginosa to pulses of signal molecules.

Quorum sensing (QS) is a communication form between bacteria via small signal molecules that enables global gene regulation as a function of cell density. We applied a microfluidic mother machine to study the kinetics of the QS response of Pseudomonas aeruginosa bacteria to additions and withdrawals of signal molecules. We traced the fast buildup and the subsequent considerably slower decay of a population-level and single-cell-level QS response. We applied a mathematical model to explain the results quantitatively. We found significant heterogeneity in QS on the single-cell level, which may result from variations in quorum-controlled gene expression and protein degradation. Heterogeneity correlates with cell lineage history, too. We used single-cell data to define and quantitatively characterize the population-level quorum state. We found that the population-level QS response is well-defined. The buildup of the quorum is fast upon signal molecule addition. At the same time, its decay is much slower following signal withdrawal, and the quorum may be maintained for several hours in the absence of the signal. Furthermore, the quorum sensing response of the population was largely repeatable in subsequent pulses of signal molecules.

Left Ventricular and Atrial Deformation in Patients with Acute Decompensated Heart Failure: A Pilot Study.

AIMS: The aims of this study were to compare global longitudinal strain of the left ventricle (LV-GLS) and reservoir strain of the left atrium (R-LAS) values between patients with acute decompensation of chronic heart failure (HF) and a control group. METHODS: Sixteen patients admitted to our ward for acute decompensation of HF were enrolled in this study. Transthoracic echocardiography (TTE) with two-dimensional speckle-tracking analysis (2D ST) was performed in each patient. The patients were divided into two subgroups according to the value of left ventricular ejection fraction (EF) using a cut-off value of ≤40% to distinguish heart failure with reduced ejection fraction (HFrEF) from heart failure with preserved ejection fraction (HFpEF). The control group consisted of 16 individuals without a history of cardiovascular disease, each of whom underwent 2D ST analysis as well. RESULTS: We found that LV-GLS and R-LAS were significantly lower in both the HFrEF and HFpEF subgroups in comparison with the control group (LV-GLS: -13.4 ± 4.7% vs. -19.7 ± 2.5%, p ˂ 0.05; R-LAS: +12.2 ± 6.9% vs. +40.3 ± 7.4%, p ˂ 0.05). Furthermore, there was a significant difference in LV-GLS (-9.6 ± 3.2% vs. -15.2 ± 4.3%, p ˂ 0.05) but not in R-LAS (+13.7 ± 8.6% vs. +11.4 ± 6.2%) between the HFrEF and HFpEF subgroups. CONCLUSIONS: Our study demonstrated a significant difference in LV-GLS and R-LAS in all enrolled HF patients compared to the control group. There was also a significant difference in LV-GLS between the HFrEF and HFpEF subgroups.

Obesity as a risk factor in atrial fibrillation and heart failure.

Objectives: The aim of this article is to provide an insight into the role of obesity as a risk factor, and as a potential etiologic agent of atrial fibrillation (AF) and heart failure (HF). Methods: A narrative (non-systematic) review article summarizing currently available data regarding the interaction between obesity, AF and HF. Results: Obesity is considered a risk factor of AF and chronic HF. Multiple recent studies indicate that obesity is also a potential causal factor in the development of AF and HF, the elucidation of pathological mechanisms of which could help devise new diagnostic and therapeutic modalities for these conditions. The discussion about obesity in relation to HF cannot omit the so-called obesity paradox, which represents a dilemma for clinicians, and it is still a source of irregularities regarding the strategy of weight reduction in obese patients with HF. Recently, the obesity paradox has also been assumed to play a role in the relationship between obesity and thromboembolic complications of AF. Conclusions: Obesity is an independent and modifiable risk factor for AF and HF. In addition, there is an increasing volume of experimental and clinical data that suggests an important role of the epicardial adipose tissue in the pathophysiology of AF. However, several issues, such as the issue of optimal pharmacotherapy and weight reduction strategy in obese patients with HF remains still unanswered, and open for future investigation.

Microfluidic Ecology Unravels the Genetic and Ecological Drivers of T4r Bacteriophage Resistance in E. coli: Insights into Biofilm-Mediated Evolution.

We use a microfluidic ecology which generates non-uniform phage concentration gradients and micro-ecological niches to reveal the importance of time, spatial population structure and collective population dynamics in the de novo evolution of T4r bacteriophage resistant motile E. coli. An insensitive bacterial population against T4r phage occurs within 20 hours in small interconnected population niches created by a gradient of phage virions, driven by evolution in transient biofilm patches. Sequencing of the resistant bacteria reveals mutations at the receptor site of bacteriophage T4r as expected but also in genes associated with biofilm formation and surface adhesion, supporting the hypothesis that evolution within transient biofilms drives de novo phage resistance.

Chemotactic Interactions of Scenedesmus sp. and Azospirillum brasilense Investigated by Microfluidic Methods.

The use of algae for industrial, biotechnological, and agricultural purposes is spreading globally. Scenedesmus species can play an essential role in the food industry and agriculture due to their favorable nutrient content and plant-stimulating properties. Previous research and the development of Scenedesmus-based foliar fertilizers raised several questions about the effectiveness of large-scale algal cultivation and the potential effects of algae on associative rhizobacteria. In the microbiological practice applied in agriculture, bacteria from the genus Azospirillum are one of the most studied plant growth-promoting, associative, nitrogen-fixing bacteria. Co-cultivation with Azospirillum species may be a new way of optimizing Scenedesmus culturing, but the functioning of the co-culture system still needs to be fully understood. It is known that Azospirillum brasilense can produce indole-3-acetic acid, which could stimulate algae growth as a plant hormone. However, the effect of microalgae on Azospirillum bacteria is unclear. In this study, we investigated the behavior of Azospirillum brasilense bacteria in the vicinity of Scenedesmus sp. or its supernatant using a microfluidic device consisting of physically separated but chemically coupled microchambers. Following the spatial distribution of bacteria within the device, we detected a positive chemotactic response toward the microalgae culture. To identify the metabolites responsible for this behavior, we tested the chemoeffector potential of citric acid and oxaloacetic acid, which, according to our HPLC analysis, were present in the algae supernatant in 0.074 mg/ml and 0.116 mg/ml concentrations, respectively. We found that oxaloacetic acid acts as a chemoattractant for Azospirillum brasilense.

Gastrointestinal Complications of Mitochondrial Encephalomyopathy, Lactic Acidosis and Stroke-Like Episodes (MELAS) Syndrome Managed By Parenteral Nutrition.

MELAS - an acronym for mitochondrial encephalomyopathy, lactic acidosis and stroke-like episodes - is a multiorgan disease caused by a mutation in mitochondrial DNA (mtDNA). Its clinical manifestations are highly variable; mainly stroke-like episodes, seizures, recurrent headaches, or muscle weakness. However, gastrointestinal complications such as chronic intestinal pseudo-obstruction (IPO), pancreatitis, gastroparesis and hepatopathy are also common. In this report we describe a young patient with gastrointestinal complication of MELAS which led to superior mesenteric artery syndrome (SMAS). It is rare but not surprising combination and should be considered in cases with significant weight loss and resistance to symptomatic treatment. The optimal energy support is the main pillar of the treatment. LEARNING POINTS: Gastrointestinal complications of MELAS such as chronic intestinal pseudo-obstruction, pancreatitis and gastroparesis can lead to undernutrition.Superior mesenteric artery syndrome is a rare condition but should be considered in cases with significant weight loss and resistance to symptomatic treatment.Optimal caloric intake and energy support can improve the condition of patients with MELAS.

Role of Platelets in Rheumatic Chronic Autoimmune Inflammatory Diseases.

Platelets are essential in maintaining blood homeostasis and regulating several inflammatory processes. They constantly interact with immune cells, have immunoregulatory functions, and can affect, through immunologically active substances, endothelium, leukocytes, and other immune response components. In reverse, inflammatory and immune processes can activate platelets, which might be significant in autoimmune disease progression and arising complications. Thus, considering this interplay, targeting platelet activity may represent a new approach to treatment of autoimmune diseases. This review aims to highlight the role of platelets in the pathogenic mechanisms of the most frequent chronic autoimmune inflammatory diseases to identify gaps in current knowledge and to provide potential new targets for medical interventions.

The Anti-Thrombotic Effects of PCSK9 Inhibitors.

Atherosclerosis is the primary process that underlies cardiovascular disease. The connection between LDL cholesterol and the formation of atherosclerotic plaques is established by solid evidence. PCSK9 inhibitors have proven to be a valuable and practical resource for lowering the LDL cholesterol of many patients in recent years. Their inhibitory effect on atherosclerosis progression seems to be driven not just by lipid metabolism modification but also by LDL-independent mechanisms. We review the effect of PCSK9 inhibitors on various mechanisms involving platelet activation, inflammation, endothelial dysfunction, and the resultant clot formation. The main effectors of PCSK9 activation of platelets are CD36 receptors, lipoprotein(a), oxidised LDL particles, tissue factor, and factor VIII. Many more molecules are under investigation, and this area of research is growing rapidly.

MiR-126 and miR-146a as markers of type 2 diabetes mellitus: a pilot study.

INTRODUCTION: Despite known risk factors for developing type 2 diabetes mellitus (T2D), the research community still tries to discover new markers that would widen our diagnostic and therapeutic approach to diabetes. Therefore, research on microRNA (miR) in diabetes thrives. This study aimed to assess the utility of miR-126, miR-146a, and miR-375 as novel diagnostic markers for T2D. METHODS: We examined relative quantities of miR-126, miR-146a, and miR-375 in the serum of patients with established type 2 diabetes mellitus (n = 68) and compared these with a control group (n = 29). We also undertook a ROC analysis of significantly changed miR to examine their use as a diagnostic test. RESULTS: MiR-126 (p < 0.0001) and miR-146a (p = 0.0005) showed a statistically significant reduction in patients with type 2 diabetes mellitus. MiR-126 also proved to be an exceptional diagnostic test in our study cohort, with high sensitivity (91 %) and specificity (97 %). We did not find any difference in our study groups' relative quantities of miR-375. CONCLUSION: The study proved a statistically significant reduction of miR-126 and miR-146a in patients with T2D (Tab. 4, Fig. 6, Ref. 51). Text in PDF www.elis.sk Keywords: microRNA, epigenetics, genomics, type 2 diabetes mellitus, miR-126, miR-146a and miR-375.

COVID-19 and the Response to Antiplatelet Therapy.

The coronavirus SARS-CoV2 disease (COVID-19) is connected with significant morbidity and mortality (3.4%), disorders in hemostasis, including coagulopathy, activation of platelets, vascular injury, and changes in fibrinolysis, which may be responsible for an increased risk of thromboembolism. Many studies demonstrated relatively high rates of venous and arterial thrombosis related to COVID-19. The incidence of arterial thrombosis in severe/critically ill intensive care unit-admitted COVID-19 patients appears to be around 1%. There are several ways for the activation of platelets and coagulation that may lead to the formation of thrombi, so it is challenging to make a decision about optimal antithrombotic strategy in patients with COVID-19. This article reviews the current knowledge about the role of antiplatelet therapy in patients with COVID-19.

Ecological succession and the competition-colonization trade-off in microbial communities.

BACKGROUND: During range expansion in spatially distributed habitats, organisms differ from one another in terms of their patterns of localization versus propagation. To exploit locations or explore the landscape? This is the competition-colonization trade-off, a dichotomy at the core of ecological succession. In bacterial communities, this trade-off is a fundamental mechanism towards understanding spatio-temporal fluxes in microbiome composition. RESULTS: Using microfluidics devices as structured bacterial habitats, we show that, in a synthetic two-species community of motile strains, Escherichia coli is a fugitive species, whereas Pseudomonas aeruginosa is a slower colonizer but superior competitor. We provide evidence highlighting the role of succession and the relevance of this trade-off in the community assembly of bacteria in spatially distributed patchy landscapes. Furthermore, aggregation-dependent priority effects enhance coexistence which is not possible in well-mixed environments. CONCLUSIONS: Our findings underscore the interplay between micron-scale landscape structure and dispersal in shaping biodiversity patterns in microbial ecosystems. Understanding this interplay is key to unleash the technological revolution of microbiome applications.

Recurrent urinary tract infections in kidney transplant patients with polycystic kidneys.

INTRODUCTION: Kidney transplantation is now a routine method used to treat end-stage renal disease. About 10 % of kidney transplant patients are patients with autosomal dominant polycystic kidney disease (ADPKD). After successful kidney transplantation, recurrent urinary tract infections also occur in initially asymptomatic patients. MATERIAL AND METHODS: The group included 320 patients after kidney transplantation. We compared patients with ADPKD versus patients without ADPKD in terms of the presence of recurrent urinary tract infections. THE RESULTS: The incidence of recurrent urinary tract infections (rIMCs) was 18% in patients without ADPKD and 48% in patients without ADPKD. Nephrectomy after kidney transplantation due to recurrent urinary tract infections eliminated this infectious complication (in 86% of patients). CONCLUSION: Kidney transplant patients with ADPKD have a significantly higher incidence of recurrent urinary tract infections. Removal of polycystic kidneys is a suitable solution if the infection persists.

Viable protoplast formation of the coral endosymbiont alga Symbiodinium spp. in a microfluidics platform.

Symbiodiniaceae is an important dinoflagellate family which lives in endosymbiosis with reef invertebrates, including coral polyps, making them central to the holobiont. With coral reefs currently under extreme threat from climate change, there is a pressing need to improve our understanding on the stress tolerance and stress avoidance mechanisms of Symbiodinium spp. Reactive oxygen species (ROS) such as singlet oxygen are central players in mediating various stress responses; however, the detection of ROS using specific dyes is still far from definitive in intact Symbiodinium cells due to the hindrance of uptake of certain fluorescent dyes because of the presence of the cell wall. Protoplast technology provides a promising platform for studying oxidative stress with the main advantage of removed cell wall, however the preparation of viable protoplasts remains a significant challenge. Previous studies have successfully applied cellulose-based protoplast preparation in Symbiodiniaceae; however, the protoplast formation and regeneration process was found to be suboptimal. Here, we present a microfluidics-based platform which allowed protoplast isolation from individually trapped Symbiodinium cells, by using a precisely adjusted flow of cell wall digestion enzymes (cellulase and macerozyme). Trapped single cells exhibited characteristic changes in their morphology, cessation of cell division and a slight decrease in photosynthetic activity during protoplast formation. Following digestion and transfer to regeneration medium, protoplasts remained photosynthetically active, regrew cell walls, regained motility, and entered exponential growth. Elevated flow rates in the microfluidic chambers resulted in somewhat faster protoplast formation; however, cell wall digestion at higher flow rates partially compromised photosynthetic activity. Physiologically competent protoplasts prepared from trapped cells in microfluidic chambers allowed for the first time the visualization of the intracellular localization of singlet oxygen (using Singlet Oxygen Sensor Green dye) in Symbiodiniaceae, potentially opening new avenues for studying oxidative stress.

Variance in Landscape Connectivity Shifts Microbial Population Scaling.

Understanding mechanisms shaping distributions and interactions of soil microbes is essential for determining their impact on large scale ecosystem services, such as carbon sequestration, climate regulation, waste decomposition, and nutrient cycling. As the functional unit of soil ecosystems, we focus our attention on the spatial structure of soil macroaggregates. Emulating this complex physico-chemical environment as a patchy habitat landscape we investigate on-chip the effect of changing the connectivity features of this landscape as Escherichia coli forms a metapopulation. We analyze the distributions of E. coli occupancy using Taylor's law, an empirical law in ecology which asserts that the fluctuations in populations is a power law function of the mean. We provide experimental evidence that bacterial metapopulations in patchy habitat landscapes on microchips follow this law. Furthermore, we find that increased variance of patch-corridor connectivity leads to a qualitative transition in the fluctuation scaling. We discuss these results in the context of the spatial ecology of microbes in soil.

Emergence of Resistant Escherichia coli Mutants in Microfluidic On-Chip Antibiotic Gradients.

Spatiotemporal structures and heterogeneities are common in natural habitats, yet their role in the evolution of antibiotic resistance is still to be uncovered. We applied a microfluidic gradient generator device to study the emergence of resistant bacteria in spatial ciprofloxacin gradients. We observed biofilm formation in regions with sub-inhibitory concentrations of antibiotics, which quickly expanded into the high antibiotic regions. In the absence of an explicit structure of the habitat, this multicellular formation led to a spatial structure of the population with local competition and limited migration. Therefore, such structures can function as amplifiers of selection and aid the spread of beneficial mutations. We found that the physical environment itself induces stress-related mutations that later prove beneficial when cells are exposed to antibiotics. This shift in function suggests that exaptation occurs in such experimental scenarios. The above two processes pave the way for the subsequent emergence of highly resistant specific mutations.

Diabetic Heart Failure with Preserved Left Ventricular Ejection Fraction: Review of Current Pharmacotherapy.

Diabetes is associated with several diabetic-related abnormalities which increase the risk of onset or worsening of heart failure. Recent studies showed that the majority of diabetic patients present with heart failure with preserved ejection fraction (HFpEF), and the prevalence of HFpEF in diabetics is alarming. Moreover, outcomes in HFpEF are poor and could be compared to those of heart failure with reduced ejection fraction (HFrEF), with 1-year mortality ranging between 10 and 30%. In contrast to HFrEF, there is very limited evidence for pharmacologic therapy in symptomatic patients with preserved ejection fraction, and therefore, the optimal selection of treatment for diabetic HFpEF remains challenging. This narrative review article summarizes the currently available data on the pharmacological treatment of HFpEF in patients with diabetes.

Microfluidic Platforms Designed for Morphological and Photosynthetic Investigations of Chlamydomonas reinhardtii on a Single-Cell Level.

Chlamydomonas reinhardtii is a model organism of increasing biotechnological importance, yet, the evaluation of its life cycle processes and photosynthesis on a single-cell level is largely unresolved. To facilitate the study of the relationship between morphology and photochemistry, we established microfluidics in combination with chlorophyll a fluorescence induction measurements. We developed two types of microfluidic platforms for single-cell investigations: (i) The traps of the "Tulip" device are suitable for capturing and immobilizing single cells, enabling the assessment of their photosynthesis for several hours without binding to a solid support surface. Using this "Tulip" platform, we performed high-quality non-photochemical quenching measurements and confirmed our earlier results on bulk cultures that non-photochemical quenching is higher in ascorbate-deficient mutants (Crvtc2-1) than in the wild-type. (ii) The traps of the "Pot" device were designed for capturing single cells and allowing the growth of the daughter cells within the traps. Using our most performant "Pot" device, we could demonstrate that the FV/FM parameter, an indicator of photosynthetic efficiency, varies considerably during the cell cycle. Our microfluidic devices, therefore, represent versatile platforms for the simultaneous morphological and photosynthetic investigations of C. reinhardtii on a single-cell level.

Direct Oral Anticoagulants Plasma Levels in Patients with Atrial Fibrillation at the Time of Bleeding: A Pilot Prospective Study.

ABSTRACT: Patients with atrial fibrillation (AF) on long-term direct oral anticoagulants (DOACs) may be at higher risk of bleeding because of higher anti-Xa or anti-IIa levels. However, there is no postmarketing study investigating these DOAC plasma levels at the time of bleeding. The aim of this study was to evaluate DOAC levels at the time of a bleeding emergency. We analyzed 5440 patients examined at our Emergency Department in from April 1, 2019, to September 30, 2019. During this period, we prospective identified 105 consecutive patients with bleeding while on long-term antithrombotic therapy; 49 patients had AF on DOACs. We compared DOAC levels in patients who bled against a control sample of 55 patients who tolerated long-term high dose DOAC therapy without any emergency. Samples of these patients were tested with drug-specific anti-Xa chromogenic analysis (rivaroxaban and apixaban) and with Hemoclot Thrombin Inhibitor assay (dabigatran). Dabigatran-treated patients who bled had significantly higher anti-IIa levels when compared with trough (261.4 ± 163.7 vs. 85.4 ± 57.2 ng/mL, P < 0.001) and peak samples of controls (261.4 ± 163.7 vs. 138.8 ± 78.7 ng/mL, P < 0.05). Similarly, there were significantly higher anti-Xa levels in rivaroxaban-treated and apixaban-treated patients with bleeding compared with trough control samples (rivaroxaban: 245.9 ± 150.2 vs. 52.5 ± 36.4 ng/mL, P <0.001 and apixaban: 311.8 ± 142.5 vs. 119.9 ± 81.7 ng/mL, P < 0.001), as well as in apixaban-treated patients when compared with peak control samples (311.8 ± 142.5 vs. 210.9 ± 88.7 ng/mL, P < 0.05). Finally, rivaroxaban anti-Xa levels in patients who bled tended to be higher compared with peak control samples (245.9 ± 150.2 vs. 177.6 ± 38.6 ng/mL, P = 0.13). This observational study showed a significant difference in anti-IIa and anti-Xa plasma levels in patients with AF with bleeding complications compared with those who tolerated long-term high-dose DOAC therapy without bleeding complications.