Real-time monitoring of extracellular ATP in bacterial cultures using thermostable luciferase

Rapid enrichment of anaerobic ammonia oxidation bacteria by combining low nitrogen strength with microbial viability

The rapid enrichment of anaerobic ammonia oxidation (anammox) bacteria (AnAOB) is challenging owing to their slow growth rate. Substrate supply strategies influence the AnAOB yield and anammox performance. In this study, a feeding strategy for low nitrogen strength with constant substrate concentrations and a hydraulic retention time decreasing over a gradient was investigated in an up-flow sludge blanket reactor. With increasing nitrogen load, the nitrogen removal rate increased from 0.2 to 6.3 kg-N m-3 day-1, and the ratios among ammonium utilization, nitrite depletion, and nitrate production changed from 1:2.62:2.03 to 1:0.99:0.17. Excessive extracellular adenosine triphosphate (ATP) release occurred under famine conditions, whereas intracellular ATP accumulated under feast conditions. Rapid AnAOB growth, with a doubling time of 2 d, was associated with high microbial viability. A combined strategy of low nitrogen strength and microbial viability was proposed for the rapid growth of AnAOB. These results demonstrate accelerated process start-up and help us to understand anammox metabolism in depth.

Targeting the CD39/CD73 pathway: New insights into cardiac fibrosis and inflammation in female cardiac surgery patients

Women undergoing cardiac surgery suffer from worse outcomes than their male counterparts. The reasons for this disparity are multifactorial, but the loss of the protective effects of estrogen likely plays a role. Estrogen acts on the CD39/CD73 purine pathway, and loss of estrogen effects may contribute to the increased inflammation seen in post-menopausal women. We aimed to compare CD39/CD73 expression and downstream fibrosis, and inflammation in men and women undergoing cardiac surgery and then used an ovariectomy/high fat diet mouse model to approximate women who present for cardiac surgery to test therapeutics. We found decreased CD39 and CD73 in women compared to men, which was associated with increased fibrosis. Apyrase supplementation (a CD39 mimetic) improved ejection fraction and decreased E/e'. Increased CD73 function (via dipyridamole) decreased fibrosis. This study demonstrates the importance of purinergic dysfunction in cardiovascular disease in women and presents two potential therapeutics to improve cardiac health via manipulation of purine pathways.

The impact of common redox mediators on cellular health: a comprehensive study

Electrochemistry has become a key technique for studying biomolecular reactions and dynamics of living systems by using electron-transfer reactions to probe the complex interactions between biological redox molecules and their surrounding environments. To enable such measurements, redox mediators such as ferro/ferricyanide, ferrocene methanol, and tris(bipyridine) ruthenium(II) chloride are used. However, the impact of these exogeneous redox mediators on the health of cell cultures remains underexplored. Herein, we present the effects of three common redox mediators on the health of four of the most commonly used cell lines (Panc1, HeLa, U2OS, and MDA-MB-231) in biological studies. Cell health was assessed using three independent parameters: reactive oxygen species quantification by fluorescence flow cytometry, cell migration through scratch assays, and cell growth via luminescence assays. We show that as the concentration of mediator exceeds 1 mM, ROS increases in all cell types while cell viability plumets. In contrast, cell migration was only hindered at the highest concentration of each mediator. Our observations highlight the crucial role that optimized mediator concentrations play in ensuring accuracy when studying biological systems by electrochemical methods. As such, these findings provide a critical reference for selecting redox mediator concentrations for bioanalytical studies on live cells.

Metabolic modelling reveals the aging-associated decline of host-microbiome metabolic interactions in mice

Aging is accompanied by considerable changes in the gut microbiome, yet the molecular mechanisms driving aging and the role of the microbiome remain unclear. Here we combined metagenomics, transcriptomics and metabolomics from aging mice with metabolic modelling to characterize host-microbiome interactions during aging. Reconstructing integrated metabolic models of host and 181 mouse gut microorganisms, we show a complex dependency of host metabolism on known and previously undescribed microbial interactions. We observed a pronounced reduction in metabolic activity within the aging microbiome accompanied by reduced beneficial interactions between bacterial species. These changes coincided with increased systemic inflammation and the downregulation of essential host pathways, particularly in nucleotide metabolism, predicted to rely on the microbiota and critical for preserving intestinal barrier function, cellular replication and homeostasis. Our results elucidate microbiome-host interactions that potentially influence host aging processes. These pathways could serve as future targets for the development of microbiome-based anti-aging therapies.

Valorizing Banana Peel Waste into Mesoporous Biogenic Nanosilica and Novel Nano-biofertilizer Formulation Thereof via Nano-biopriming Inspired Tripartite Interaction Studies

The present study attempts to valorize banana peel waste (BPW) into high-value precipitated nanosilica-based agri-input. XRD analysis revealed smaller-sized biogenic nanosilica (BNS) with an increase (without heating) or decrease (with heating) in the duration of acid pretreatment during the pre-calcination step. The highest BNS yield was recorded in post-calcinated BPW ash involving simultaneous acid and heat treatment (1 h) (SA-3). FTIR analysis displayed an intense peak at 1078.3 cm-1, indicating "Si-O-Si bond" asymmetric vibrations. FESEM-EDX micrographs revealed high-purity BNS of predominantly spheroid morphology. The BJH plot exhibited mesoporous nanosilica with a median pore diameter of ∼33.82 nm. The bipartite interaction of 0.001 g mL-1 BNS signifies growth-promoting effects on Bacillus subtilis (BS) and Raphanus sativus (RS). The nano-primed RS seeds showed higher germination indices over non-primed seeds at 0.001 g of BNS mL-1. Further, the nano-biopriming studies showed the synergistic response of BNS and BS interaction on RS seeds in terms of higher seedling growth, biomass content, and stress tolerance index. The findings open new avenues for developing nano-biofertilizer formulations that serve multifaceted functions such as waste management and biomass valorization into value-added products and fulfill sustainable development goals.

Understanding the Influence of Rheology on Biofilm Adhesion and Implication for Food Safety

Understanding biofilm rheology is crucial for industrial and domestic food safety practices. This comprehensive review addresses the knowledge gap on the rheology of biofilm. Specifically, the review explores the influence of fluid flow, shear stress, and substrate properties on the initiation, structure, and functionality of biofilms, as essential implications for food safety. The viscosity and shear-thinning characteristics of non-Newtonian fluids may impact the attachment and detachment dynamics of biofilms, influencing their stability and resilience under different flow conditions. The discussion spans multiple facets, including the role of extracellular polymeric substances (EPSs) in biofilm formation, the impact of rheological attributes of biofilm on their adhesion to surfaces, and the influence of shear forces between biofilms and substrate's surface characteristics on biofilm stability. Analytical techniques, encompassing rheometry, microscopy, and molecular biology approaches, are scrutinized for their contributions to understanding these interactions. The paper delves into the implications for the food industry, highlighting potential risks associated with biofilm formation and proposing strategies for effective control and prevention. Future research directions and the integration of rheological considerations into food safety regulations are underscored as pivotal steps in mitigating biofilm-related risks. The synthesis of microbiology, materials science, and engineering perspectives offers a multidimensional exploration of rheology-biofilm interactions, laying the groundwork for informed interventions in diverse industrial settings.

Concentration vs. Optical Density of ESKAPEE Bacteria: A Method to Determine the Optimum Measurement Wavelength

Optical density measurement has been used for decades to determine the microorganism concentration and more rarely for mammalian cells. Although this measurement can be carried out at any wavelength, studies report a limited number of measurement wavelengths, mainly around 600 nm, and no consensus seems to be emerging to propose an objective method for determining the optimum measurement wavelength for each microorganism. In this article, we propose a method for analyzing the absorbance spectra of ESKAPEE bacteria and determining the optimum measurement wavelength for each of them. The method is based on the analysis of the signal-to-noise ratio of the relationships between concentrations and optical densities when the measurement wavelength varies over the entire spectral range of the absorbance spectra measured for each bacterium. These optimum wavelengths range from 612 nm for Enterococcus faecium to 705 nm for Acinetobacter baumannii. The method can be directly applied to any bacteria, any culture method, and also to any biochemical substance with an absorbance spectrum without any particular feature such as an identified maximum.

Purinergic control of apical ion conductance by luminal ATP in rat colonic epithelium

ATP, released e.g. after cell damage or during inflammation, can alter ion transport across the intestinal mucosa via stimulation of purinergic receptors in the basolateral as well as in the apical membrane of epithelial cells. When ATP acts from the serosal side, it induces an increase in short-circuit current (Isc) via Cl- secretion across the colonic epithelium. In contrast, mucosal ATP or its derivative, BzATP, predominantly stimulating ionotropic P2X4 and P2X7 receptors, evoke an increase in Isc, which could not be explained by Cl- secretion. The underlying ion currents after stimulation of apical purinergic receptors in rat distal colon are still unclear and were investigated in the present study. Ussing chamber experiments revealed that the Isc induced by mucosal ATP was dependent on the presence of mucosal Ca2+ and inhibited by the K+ channel blocker, Ba2+, indicating the involvement of Ca2+-dependent K+ channels. Blockade of the transepithelial Isc by lanthanides (La3+, Gd3+) suggests that Ca2+ enters the epithelium via nonselective cation channels. Experiments with basolaterally depolarized epithelia confirmed the activation of apical lanthanide-sensitive Na+- and Ca2+-permeable cation channels by ATP. Putative candidates might be TRP channels, from which several subtypes were detected in colonic tissue in RT-PCR experiments. In addition, the activation of an apical Cl- conductance was observed when suitable Cl- concentration gradients were applied. Consequently, mucosal ATP, acting as 'danger signal', stimulates cation and anion channels in the apical membrane to induce a secretory response as part of the local defence mechanism in the intestinal epithelium.

Released bacterial ATP shapes local and systemic inflammation during abdominal sepsis

Sepsis causes millions of deaths per year worldwide and is a current global health priority declared by the WHO. Sepsis-related deaths are a result of dysregulated inflammatory immune responses indicating the need to develop strategies to target inflammation. An important mediator of inflammation is extracellular adenosine triphosphate (ATP) that is released by inflamed host cells and tissues, and also by bacteria in a strain-specific and growth-dependent manner. Here, we investigated the mechanisms by which bacteria release ATP. Using genetic mutant strains of Escherichia coli (E. coli), we demonstrate that ATP release is dependent on ATP synthase within the inner bacterial membrane. In addition, impaired integrity of the outer bacterial membrane notably contributes to ATP release and is associated with bacterial death. In a mouse model of abdominal sepsis, local effects of bacterial ATP were analyzed using a transformed E. coli bearing an arabinose-inducible periplasmic apyrase hydrolyzing ATP to be released. Abrogating bacterial ATP release shows that bacterial ATP suppresses local immune responses, resulting in reduced neutrophil counts and impaired survival. In addition, bacterial ATP has systemic effects via its transport in outer membrane vesicles (OMV). ATP-loaded OMV are quickly distributed throughout the body and upregulated expression of genes activating degranulation in neutrophils, potentially contributing to the exacerbation of sepsis severity. This study reveals mechanisms of bacterial ATP release and its local and systemic roles in sepsis pathogenesis.

Single-Use, Metabolite Absorbing, Resonant Transducer (SMART) Culture Vessels for Label-Free, Continuous Cell Culture Progression Monitoring

Secreted metabolites are an important class of bio-process analytical technology (PAT) targets that can correlate to cell conditions. However, current strategies for measuring metabolites are limited to discrete measurements, resulting in limited understanding and ability for feedback control strategies. Herein, a continuous metabolite monitoring strategy is demonstrated using a single-use metabolite absorbing resonant transducer (SMART) to correlate with cell growth. Polyacrylate is shown to absorb secreted metabolites from living cells containing hydroxyl and alkenyl groups such as terpenoids, that act as a plasticizer. Upon softening, the polyacrylate irreversibly conformed into engineered voids above a resonant sensor, changing the local permittivity which is interrogated, contact-free, with a vector network analyzer. Compared to sensing using the intrinsic permittivity of cells, the SMART approach yields a 20-fold improvement in sensitivity. Tracking growth of many cell types such as Chinese hamster ovary, HEK293, K562, HeLa, and E. coli cells as well as perturbations in cell proliferation during drug screening assays are demonstrated. The sensor is benchmarked to show continuous measurement over six days, ability to track different growth conditions, selectivity to transducing active cell growth metabolites against other components found in the media, and feasibility to scale out for high throughput campaigns.

Rapid Phenotypic Antibiotics Susceptibility Analysis by a 3D Printed Prototype

One of the most important public health concerns is the increase in antibiotic-resistant pathogens and corresponding treatment of associated infections. Addressing this challenge requires more efficient use of antibiotics, achievable by the use of evidence-based, effective antibiotics identified by antibiotic susceptibility testing (AST). However, the current standard method of phenotypic AST used for this purpose requires 48 h or more from sample collection to result. Until results are available, broad-spectrum antibiotics are used to avoid delaying treatment. The turnaround time must therefore be shortened in order for the results to be available before the second administration of antibiotics. The phenotypic electrochemical AST method presented here identifies effective antibiotics within 5-10 h after sampling. Spiked serum samples, including polymicrobial samples, with clinically relevant pathogens and respective concentrations commonly found in bloodstream infections (Escherichia coli, Staphylococcus aureus, Klebsiella pneumoniae, and Pseudomonas aeruginosa) are used. Direct loading of the test with diluted serum eliminates the need for a pre-culture, as required by existing methods. Furthermore, by combining several electrochemical measurement procedures with computational analysis, allowing the method to be used both online and offline, the AST achieves a sensitivity of 94.44% and a specificity of 95.83% considering each replicate individually.

Antibacterial Activity and Mechanism of Action of Osthole against Listeria monocytogenes

The purpose of this study was to investigate the antibacterial activity and mechanism of action of osthole against Listeria monocytogenes. The antibacterial activity of osthole was evaluated by determining the minimum inhibitory concentration (MIC) and growth curve. Cell morphology, membrane permeability, membrane integrity, bacterial physiology, and metabolism were explored using different methods to elucidate the mechanism of action of osthole. It was shown that the MIC of osthole against L. monocytogenes was 62.5 μg/mL and it inhibited the growth of L. monocytogenes effectively in a concentration-dependent manner. Scanning electron microscopy (SEM) images demonstrated morphology changes of L. monocytogenes, including rough surface, cell shrinkage, and rupture. It was found that extracellular conductivity and macromolecule content were increased significantly in the presence of osthole, indicating the disruption of cell membrane integrity and permeability. Laser confocal microscopy results supported the conclusion that osthole caused severe damage to the cell membrane. It was also noticed that osthole depleted intracellular adenosine triphosphate (ATP), inhibited Na+-K+-ATPase and Ca2+-Mg2+-ATPase activity, and promoted the accumulation of intracellular reactive oxygen species (ROS), leading to cell death. This study suggests that osthole is a promising antibacterial agent candidate against L. monocytogenes, and it shows potential in the prevention and control of foodborne pathogens.

MS, Pires MM. Bioluminescence-Based Determination of Cytosolic Accumulation of Antibiotics in Escherichia coli

Antibiotic resistance is an alarming public health concern that affects millions of individuals across the globe each year. A major challenge in the development of effective antibiotics lies in their limited ability to permeate cells, noting that numerous susceptible antibiotic targets reside within the bacterial cytosol. Consequently, improving the cellular permeability is often a key consideration during antibiotic development, underscoring the need for reliable methods to assess the permeability of molecules across cellular membranes. Currently, methods used to measure permeability often fail to discriminate between the arrival within the cytoplasm and the overall association of molecules with the cell. Additionally, these techniques typically possess throughput limitations. In this work, we describe a luciferase-based assay designed for assessing the permeability of molecules in the cytosolic compartment of Gram-negative bacteria. Our findings demonstrate a robust system that can elucidate the kinetics of intracellular antibiotic accumulation in live bacterial cells in real time.

A novel rapid bioluminescence-based antimicrobial susceptibility testing method based on adenosine triphosphate consumption

Introduction

Standard, phenotypic antimicrobial susceptibility testing (AST) methods require 16-20 h of incubation and are considered as the bottleneck in providing timely input for appropriate antimicrobial treatment. In this study, a novel adenosine triphosphate (ATP)-bioluminescence-based method which allows rapid AST within 3 h was described.

Methods

Standard AST was performed for 56 Enterobacterales isolates using EUCAST disk diffusion (DD) methodology. For the bioluminescence-based rapid AST, suspensions of bacteria were prepared using Mueller-Hinton broth to obtain a turbidity of 0.5 McFarland. The suspensions were distributed into 96-well microtiter plates. ATP (20 mM) and fixed concentrations of different antibiotics were added. Following incubation at 37°C for 1 h, a luminescent reaction mixture, including the substrate luciferin and luciferase enzyme solutions, was added. The chemiluminescence was monitored using an imaging system. Light production demonstrated the presence of ATP, indicating that the isolate was susceptible to the antibiotic in the well. Absence or decrease of light intensity, compared with the growth control well, indicated the use of ATP as an indirect measure of bacterial growth, and therefore resistance to the antibiotic in the well.

Results

The novel AST method was tested using a total of 348 test wells. Concordance was achieved for 290 (83.3%) of the tests, whereas 52 (14.9%) and 6 (1.7%) tests caused minor and major errors, respectively.

Discussion

In this study, a bioluminescence-based rapid AST was developed based on the consumption of ATP by bacteria. Our method's uniqueness relies on determining ATP consumption by microorganisms in the presence or absence of an antibiotic. The novel AST method described in this study lays the groundwork for obtaining rapid results, which should be considered as a proof of concept. With further optimization studies, this novel method can provide higher accuracy and be introduced into clinical practice as a routine AST method.

Bioluminescence-Based Determination of Cytosolic Accumulation of Antibiotics in Escherichia coli

Antibiotic resistance is an alarming public health concern that affects millions of individuals across the globe each year. A major challenge in the development of effective antibiotics lies in their limited ability to permeate into cells, noting that numerous susceptible antibiotic targets reside within the bacterial cytosol. Consequently, improving cellular permeability is often a key consideration during antibiotic development, underscoring the need for reliable methods to assess the permeability of molecules across cellular membranes. Currently, methods used to measure permeability often fail to discriminate between arrival within the cytoplasm and the overall association of molecules with the cell. Additionally, these techniques typically possess throughput limitations. In this work, we describe a luciferase-based assay designed for assessing the permeability of molecules into the cytosolic compartment of Gram-negative bacteria. Our findings demonstrate a robust system that can elucidate the kinetics of intracellular antibiotics accumulation in live bacterial cells in real time.

Evaluating the Sensitivity of Different Molecular Techniques for Detecting Mycobacterium tuberculosis Complex in Patients with Pulmonary Infection

This study aimed to evaluate the accuracy of detecting drug-resistant Mycobacterium tuberculosis complex (MTBC)-specific DNA in sputum specimens from 48 patients diagnosed with pulmonary tuberculosis. The presence of MTBC DNA in the specimens was validated using the GeneXpert MTB/RIF system and compared with a specific PCR assay targeting the IS6110 and the mtp40 gene sequence fragments. Additionally, the results obtained by multiplex PCR assays to detect the most frequently encountered rifampin, isoniazid, and ethambutol resistance-conferring mutations were matched with those obtained by GeneXpert and phenotypic culture-based drug susceptibility tests. Of the 48 sputum samples, 25 were positive for MTBC using the GeneXpert MTB/RIF test. Nevertheless, the IS6110 and mtp40 single-step PCR revealed the IS6110 in 27 of the 48 sputum samples, while the mtp40 gene fragment was found in only 17 of them. Furthermore, multiplex PCR assays detected drug-resistant conferring mutations in 21 (77.8%) of the 27 samples with confirmed MTBC DNA, 10 of which contained single drug-resistant conferring mutations towards ethambutol and two towards rifampin, and the remaining nine contained double-resistant mutations for ethambutol and rifampin. In contrast, only five sputum specimens (18.5%) contained drug-resistant MTBC isolates, and two contained mono-drug-resistant MTBC species toward ethambutol and rifampin, respectively, and the remaining three were designated as multi-drug resistant toward both drugs using GeneXpert and phenotypic culture-based drug susceptibility tests. Such discrepancies in the results emphasize the need to develop novel molecular tests that associate with phenotypic non-DNA-based assays to improve the detection of drug-resistant isolates in clinical specimens in future studies.

Absorption/Attenuation Spectral Description of ESKAPEE Bacteria: Application to Seeder-Free Culture Monitoring, Mammalian T-Cell and Bacteria Mixture Analysis and Contamination Description

Despite numerous innovations, measuring bacteria concentrations on a routine basis is still time consuming and ensuring accurate measurements requires careful handling. Furthermore, it often requires sampling small volumes of bacteria suspensions which might be poorly representative of the real bacteria concentration. In this paper, we propose a spectroscopy measurement method based on a description of the absorption/attenuation spectra of ESKAPEE bacteria. Concentrations were measured with accuracies less than 2%. In addition, mixing the mathematical description of the absorption/attenuation spectra of mammalian T-cells and bacteria allows for the simultaneous measurements of both species' concentrations. This method allows real-time, sampling-free and seeder-free measurement and can be easily integrated into a closed-system environment.

Undesirable consequences of the metallic nanoparticles action on the properties and functioning of Escherichia coli, Bacillus cereus and Staphylococcus epidermidis membranes

Controversial and inconsistent findings on the toxicity of metallic nanoparticles (NPs) against many bacteria are common in recorded studies; therefore, further advanced experimental work is needed to elucidate the mechanisms underlying nanotoxicity. This study deciphered the direct effects of Ag-NPs, Cu-NPs, ZnO-NPs and TiO₂-NPs on membrane permeability, cytoplasmic leakage, ATP level, ATPase activity and fatty acid profiling of Escherichia coli, Bacillus cereus and Staphylococcus epidermidis as model microorganisms. A multifaceted analysis of all collected results indicated the different influences of individual NPs on the measured parameters depending on their type and concentration. Predominantly, membrane permeability was correlated with increased cytoplasmic leakage, reduced total ATP levels and ATPase activity. The established fatty acid profiles were unique and concerned various changes in the percentages of hydroxyl, cyclopropane, branched and unsaturated fatty acids. Decisively, E. coli was more susceptible to changes in measured parameters than B. cereus and S. epidermidis. Also, it was established that ZnO-NPs and Cu-NPs had a major differentiating impact on studied parameters. Additionally, bacterial cell imaging using scanning electron microscopy elucidated different NPs distributions on the cell surface. The presented results are believed to provide novel, valuable and accumulated knowledge in the understanding of NPs action on bacterial membranes.

Conventional methods and future trends in antimicrobial susceptibility testing

Antimicrobial susceptibility testing is an essential task for selecting appropriate antimicrobial agents to treat infectious diseases. Constant evolution has been observed in methods used in the diagnostic microbiology laboratories. Disc diffusion or broth microdilution are classical and conventional phenotypic methods with long turnaround time and labour-intensive but still widely practiced as gold-standard. Scientists are striving to develop innovative, novel and faster methods of antimicrobial susceptibility testing to be applicable for routine microbiological laboratory practice and research. To meet the requirements, there is an increasing trend towards automation, genotypic and micro/nano technology-based innovations. Automation in detection systems and integration of computers for online data analysis and data sharing are giant leaps towards versatile nature of automated methods currently in use. Genotypic methods detect a specific genetic marker associated with resistant phenotypes using molecular amplification techniques and genome sequencing. Microfluidics and microdroplets are recent addition in the continuous advancement of methods that show great promises with regards to safety and speed and have the prospect to identify and monitor resistance mechanisms. Although genotypic and microfluidics methods have many exciting features, however, their applications into routine clinical laboratory practice warrant extensive validation. The main impetus behind the evolution of methods in antimicrobial susceptibility testing is to shorten the overall turnaround time in obtaining the results and to enhance the ease of sample processing. This comprehensive narrative review summarises major conventional phenotypic methods and automated systems currently in use, and highlights principles of some of the emerging genotypic and micro/nanotechnology-based methods in antimicrobial susceptibility testing.

Physiological relevance of in-vitro cell-nanoparticle interaction studies as a predictive tool in cancer nanomedicine research

Cell uptake study is a routine experiment used as a surrogate to predict in vivo response in cancer nanomedicine research. Cell culture conditions should be designed in such a way that it emulates 'real' physiological conditions and avoid artefacts. It is critical to dissect the steps involved in cellular uptake to understand the physical, chemical, and biological factors responsible for particle internalization. The two-dimensional model (2D) of cell culture is overly simplistic to mimic the complexity of cancer tissues that exist in vivo. It cannot simulate the critical tissue-specific properties like cell-cell interaction and cell-extracellular matrix (ECM) interaction and its influences on the temporal and spatial distribution of nanoparticles (NPs). The three dimensional model organization of heterogenous cancer and normal cells with the ECM acts as a formidable barrier to NP penetration and cellular uptake. The three dimensional cell culture (3D) technology is a breakthrough in this direction that can mimic the barrier properties of the tumor microenvironment (TME). Herein, we discuss the physiological factors that should be considered to bridge the translational gap between in and vitro cell culture studies and in-vivo studies in cancer nanomedicine.

Immobilization of Firefly Bioluminescent System: Development and Application of Reagents

The present study describes the method of preparing reagents containing firefly luciferase (FLuc) and its substrate, D-luciferin, immobilized into gelatin gel separately or together. The addition of stabilizers dithiothreitol (DTT) and bovine serum albumin (BSA) to the reagent is a factor in achieving higher activity of reagents and their stability during storage. The use of immobilized reagents substantially simplifies the procedure of assay for microbial contamination. The mechanism of action of the reagents is based on the relationship between the intensity of the bioluminescent signal and the level of ATP contained in the solution of the lysed bacterial cells. The highest sensitivity to ATP is achieved by using immobilized FLuc or reagents containing separately immobilized FLuc and D-luciferase. The limit of detection of ATP by the developed reagents is 0.3 pM, which corresponds to 20,000 cells·mL-1. The linear response range is between 0.3 pM and 3 nM ATP. The multicomponent reagent, containing co-immobilized FLuc and D-luciferin, shows insignificantly lower sensitivity to ATP-0.6 pM. Moreover, the proposed method of producing an immobilized firefly luciferin-luciferase system holds considerable promise for the development of bioluminescent biosensors intended for the analysis of microbial contamination.

Luciferase-free Luciferin Electrochemiluminescence

Luciferin is one of Nature's most widespread luminophores, and enzymes that catalyze luciferin luminescence are the basis of successful commercial "glow" assays for gene expression and metabolic ATP formation. Herein we report an electrochemical method to promote firefly's luciferin luminescence in the absence of its natural biocatalyst-luciferase. We have gained experimental and computational insights on the mechanism of the enzyme-free luciferin electrochemiluminescence, demonstrated its spectral tuning from green to red by means of electrolyte engineering, proven that the colour change does not require, as still debated, a keto/enol isomerization of the light emitter, and gained evidence of the electrostatic-assisted stabilization of the charge-transfer excited state by double layer electric fields. Luciferin's electrochemiluminescence, as well as the in situ generation of fluorescent oxyluciferin, are applied towards an optical measurement of diffusion coefficients.

Advances in chilling injury of postharvest fruit and vegetable: Extracellular ATP aspects

Due to the global use of cold chain, the development of postharvest technology to reduce chilling injury (CI) in postharvest fruits and vegetables during storage and transport is needed urgently. Considerable evidence shows that maintaining intracellular adenosine triphosphate (iATP) in harvested fruits and vegetables is beneficial to inhibiting CI occurrence. Extracellular ATP (eATP) is a damage-associated signal molecule and plays an important role in CI of postharvest fruits and vegetables through its receptor and subsequent signal transduction under low-temperature stress. The development of new aptasensors for the simultaneous determination of eATP level allows for better understanding of the roles of eATP in a myriad of responses mediated by low-temperature stress in relation to the chilling tolerance of postharvest fruits and vegetables. The multiple biological functions of eATP and its receptors in postharvest fruits and vegetables were attributed to interactions with reactive oxygen species (ROS) and nitric oxide (NO) in coordination with phytohormones and other signaling molecules via downstream physiological activities. The complicated interconnection among eATP in relation to its receptors, eATP/iATP homeostasis, ROS, NO, and heat shock proteins triggered by eATP recognition has been emphasized. This paper reviews recent advances in the beneficial effects of energy handling, outlines the production and homeostasis of eATP, discusses the possible mechanism of eATP and its receptors in chilling tolerance, and provides future research directions for CI in postharvest fruits and vegetables during low-temperature storage.

Bioluminescent test systems based on firefly luciferase for studying stress effects on living cells

The bioluminescent luciferin-luciferase reaction is based on the oxidation of D-luciferin by oxygen in the presence of ATP and magnesium ions, catalyzed by firefly luciferase. The possibilities of using this reaction to study the influence of external effectors of a physical and chemical nature (temperature exposure, additions of drugs, membrane-active compounds, etc.) on living cells (prokaryotes and eukaryotes) are considered. Examples of the use of test systems based on living cells producing thermostable firefly luciferase for monitoring cellular homeostasis are given. The study of the kinetics of changes in the concentration of ATP and luciferase inside and outside cells made it possible to determine in dynamics the metabolic activity, cytotoxicity, and survival of cells under conditions of cellular stress, to study the processes of ATP synthesis/hydrolysis, and to evaluate the effectiveness of lytic agents in changing the permeability of the cell membrane.

Examining Skin Recovery After a 3% Aqueous Hydrogen Peroxide (H2O2) Treatment Using ATP Biofluorescence

Introduction

Since its complete mapping, the human skin microbiome has become an important area of research related to skin health. The human skin is populated by an environment of microorganisms, fungi, insects, and viruses that is collectively known as the microbiota, and the complete genomic contribution to the skin is called the microbiome. The terms are different but frequently used interchangeably. Measuring the skin’s microbial diversity can be done, but it is a sophisticated technique that is performed using expensive instruments that can sequence the 16S ribosomal RNA of the microorganisms. Finding more rapid and less costly methods to analyze the changes in the skin’s microbial biome is desirable.

Methods

A study was conducted on thirty (30) inner volar forearms to see if ATP biofluorescence could be employed to examine skin microbial dysbiosis caused by the application of 3% hydrogen peroxide. Fifteen individuals were examined on both arms for a total of thirty inner volar forearms using a Charm Science^® NovaLum^® ATP analyzer to examine in a broad sense the skin’s total microbial population and how it is affected after surface treatment with 3% hydrogen peroxide over a 24-hour period.

Results

It was found that surface treatment of the skin with three cotton swab applications of 3% hydrogen peroxide five minutes apart was able to statistically significantly suppress the expression of ATP biofluorescence compared against un-swabbed sites and the effects remained significant for six hours following the H₂O₂ treatment. After 8 hours, and into the 24th hour, the ATP biofluorescence difference returns to non-statistical significance indicating potential return of the stable microbiota.

Discussion

Using ATP biofluorescence to detect possible sanitizer-induced microbial dysbiosis may be a rapid way to examine how skin treatments may impact the return of microbially disrupted skin to its normal state and how surface treatments may impact the rate of return to normal after a disruptive event.

Application of Bioluminescent Methods to Study the Effect of the Membrane-active Antibiotic Colistin on Bacterial Cells

For the first time, recombinant Escherichia coli cells expressing thermostable Luciola mingrelica firefly luciferase were used to study the effect of the membrane-active antibiotic colistin on live cells. Simple, fast and highly sensitive bioluminescent methods were developed for measurement of luciferase activity and ATP concentration inside and outside E. coli cells incubated in a nutrient medium, or in saline. Luciferase proved to be an informative protein marker for detecting the irreversible changes in cell membrane permeability. The study of kinetics of intra- and extracellular ATP concentration at different concentrations of colistin showed that the rate of decrease in intracellular ATP concentration significantly exceeded the rate of accumulation of extracellular ATP concentration. This fact could not be explained only by the release of ATP from the cell with an increase in the permeability of the outer cell membrane under the action of colistin. The loss of a significant part of intracellular ATP in presence of the colistin is probably due to a decrease in the activity of the respiratory chain enzymes and ATP synthase which operate in the cytoplasmic cell membrane, which leads to a decrease in the rate of ATP synthesis or even to its halt.

Comparison of the bacterial viability assessments for the disinfected quarantined water along with an effect of total residual oxidants

The water discarded from the quarantine station inspecting aquatic products can be served as an influx channel of invasive microorganisms to our own ecosystem. This study thus compared the viability of three different pathogenic bacteria (Escherichia coli, Vibrio harveyi, and Enterococcus faecalis) in either seawater or freshwater after their disinfection. For that, they were treated by ozonation (2.08 mM of ozone), ultraviolet irradiation (UVC-254), or thermal treatment (90℃) for 10 min, during which their resultant viability was monitored using colorimetric ATP assay, colony counting, and real-time quantitative RT-PCR. From this, ATP measurement and real-time quantitative RT-PCR have proved to be a much stronger correlation built in the fraction of each of their assays versus the colony counting, although they differed in the type of disinfection implemented. Especially, ATP assay was the most sensitively influenced by high levels of total residual oxidants (TRO) undesirably produced during the ozonation of V. harveyi and E. faecalis in seawater, although easily and shortly measured within 1 h, with higher accuracy. Aside from that, the real-time quantitative RT-PCR had a stronger correlation versus either that of seawater ozonation or thermal treatment. It is decided referring to measurement time and convenience in the field that ATP assay can be more reliably used in bacterial cell viability measurement in the quarantine after the ozonation in seawater to specifically allow the bacterial deactivation, not to overwhelmingly produce TRO due to the residual ozone provided.

Comparing the bacterial growth potential of ultra-low nutrient drinking water assessed by growth tests based on flow cytometric intact cell count versus adenosine triphosphate

The bacterial growth potential (BGP) of drinking water is widely assessed either by flow cytometric intact cell count (BGP_ICC) or adenosine triphosphate (BGP_ATP) based methods. Combining BGP_ICC and BGP_ATP measurements has been previously applied for various types of drinking water having high to low growth potential. However, this has not been applied for water with ultra-low nutrient content, such as remineralised RO permeate. To conduct a sound comparison, conventionally treated drinking water was included in this study, which was also used as an inoculum source. BGP_ICC, BGP_ATP, intact cell-yield (Y_ICC), and ATP-yield (Y_ATP) were determined for conventionally treated drinking water (Tap-water) and remineralised RO permeate (RO-water). In addition, both BGP_ICC and BGP_ATP methods were used to identify the growth-limiting nutrient in each water type. The results showed that the BGP_ICC ratio between Tap-water/RO-water was ∼7.5, whereas the BGP_ATP ratio was only ∼4.5. Moreover, the Y_ICC ratio between Tap-water/RO-water was ∼2 (9.8 ± 0.6 × 10⁶ vs. 4.6 ± 0.8 × 10⁶ cells/µg-C), whereas the Y_ATP ratio was ∼1 (0.39 ± 0.12 vs. 0.42 ± 0.06 ng ATP/µg-C), resulting in a consistently higher ATP per cell in RO-water than that of Tap-water. Both BGP_ICC and BGP_ATP methods revealed that carbon was the growth-limiting nutrient in the two types of water. However, with the addition of extra carbon, phosphate limitation was detected only with the BGP_ICC method, whereas BGP_ATP was not affected, suggesting that a combination of carbon and phosphate is essential for biomass synthesis, whereas carbon is probably utilised for cellular activities other than cell synthesis when phosphate is limited. It was estimated that the intact cell-yield growing on phosphate would be 0.70 ± 0.05 × 10⁹ cells/µg PO₄-P.

Recent Advances in the Detection of Antibiotic and Multi-Drug Resistant Salmonella: An Update

Antibiotic and multi-drug resistant (MDR) Salmonella poses a significant threat to public health due to its ability to colonize animals (cold and warm-blooded) and contaminate freshwater supplies. Monitoring antibiotic resistant Salmonella is traditionally costly, involving the application of phenotypic and genotypic tests over several days. However, with the introduction of cheaper semi-automated devices in the last decade, strain detection and identification times have significantly fallen. This, in turn, has led to efficiently regulated food production systems and further reductions in food safety hazards. This review highlights current and emerging technologies used in the detection of antibiotic resistant and MDR Salmonella.