EDTA-induced membrane fluidization and destabilization: biophysical studies on artificial lipid membranes

Surface display provides an efficient expression system for production of recombinant proteins and bacterial whole cell biosensor in E. coli

A novel bacterial display vector based on Escherichia coli has been engineered for recombinant protein production and purification. Accordingly, a construct harboring the enhanced green fluorescent protein (EGFP) and the ice nucleation protein (INP) was designed to produce EGFP via the surface display in E. coli cells. The fusion EGFP-expressed cells were then investigated using fluorescence measurement, SDS- and native-PAGE before and after TEV protease digestion. The displayed EGFP was obtained with a recovery of 57.7 % as a single band on SDS-PAGE. Next, the efficiency of the cell surface display for mutant EGFP (EGFP S202H/Q204H) was examined in sensing copper ions. Under optimal conditions, a satisfactorily linear range for copper ions concentrations up to 10 nM with a detection limit of 0.073 nM was obtained for cell-displayed mutant EGFP (mEGFP). In the presence of bacterial cell lysates and purified mEGFP, response to copper was linear in the 2-10 nM and 0.1-2 μM concentration range, respectively, with a 1.3 nM and 0.14 μM limit of detection. The sensitivity of bacterial cell lysates and surface-displayed mEGFP in the detection of copper ions is higher than the purified mEGFP.

Engineering a tunable micropattern-array assay to sort single extracellular vesicles and particles to detect RNA and protein in situ

The molecular heterogeneity of extracellular vesicles (EVs) and the co-isolation of physically similar particles, such as lipoproteins (LPs), confounds and limits the sensitivity of EV bulk biomarker characterization. Herein, we present a single-EV and particle (siEVP) protein and RNA assay (siEVP PRA) to simultaneously detect mRNAs, miRNAs, and proteins in subpopulations of EVs and LPs. The siEVP PRA immobilizes and sorts particles via positive immunoselection onto micropatterns and focuses biomolecular signals in situ. By detecting EVPs at a single-particle resolution, the siEVP PRA outperformed the sensitivities of bulk-analysis benchmark assays for RNA and protein. To assess the specificity of RNA detection in complex biofluids, EVs from various glioma cell lines were processed with small RNA sequencing, whereby two mRNAs and two miRNAs associated with glioblastoma multiforme (GBM) were chosen for cross-validation. Despite the presence of single-EV-LP co-isolates in serum, the siEVP PRA detected GBM-associated vesicular RNA profiles in GBM patient siEVPs. The siEVP PRA effectively examines intravesicular, intervesicular, and interparticle heterogeneity with diagnostic promise.

Combination Therapy with Ciprofloxacin and Pentamidine against Multidrug-Resistant Pseudomonas aeruginosa: Assessment of In Vitro and In Vivo Efficacy and the Role of Resistance-Nodulation-Division (RND) Efflux Pumps

The aim of this work was to (i) evaluate the efficacy of a combination treatment of pentamidine with ciprofloxacin against Galleria mellonella larvae infected with an MDR strain of P. aeruginosa and (ii) determine if pentamidine acts as an efflux-pump inhibitor. Resistant clinical isolates, mutant strains overexpressing one of three RND efflux pumps (MexAB-OprM, MexCD-OprJ, and MexEF-OprN), and a strain with the same three pumps deleted were used. MIC assays confirmed that the clinical isolates and the mutants overexpressing efflux pumps were resistant to ciprofloxacin and pentamidine. The deletion of the three efflux pumps induced sensitivity to both compounds. Exposure to pentamidine and ciprofloxacin in combination resulted in the synergistic inhibition of all resistant strains in vitro, but no synergy was observed versus the efflux-pump deletion strain. The treatment of infected G. mellonella larvae with the combination of pentamidine and ciprofloxacin resulted in enhanced efficacy compared with the monotherapies and significantly reduced the number of proliferating bacteria. Our measurement of efflux activity from cells revealed that pentamidine had a specific inhibitory effect on the MexCD-OprJ and MexEF-OprN efflux pumps. However, the efflux activity and membrane permeability assays revealed that pentamidine also disrupted the membrane of all cells. In conclusion, pentamidine does possess some efflux-pump inhibitory activity, in addition to a more general disruptive effect on membrane integrity that accounts for its ability to potentiate ciprofloxacin activity. Notably, the enhanced efficacy of combination therapy with pentamidine and ciprofloxacin versus MDR P. aeruginosa strains in vivo merits further investigation into its potential to treat infections via this pathogen in patients.

Engineered nickel bioaccumulation in Escherichia coli by NikABCDE transporter and metallothionein overexpression

Mine wastewater often contains dissolved metals at concentrations too low to be economically extracted by existing technologies, yet too high for environmental discharge. The most common treatment is chemical precipitation of the dissolved metals using limestone and subsequent disposal of the sludge in tailing impoundments. While it is a cost-effective solution to meet regulatory standards, it represents a lost opportunity. In this study, we engineered Escherichia coli to overexpress its native NikABCDE transporter and a heterologous metallothionein to capture nickel at concentrations in local effluent streams. We found the engineered strain had a 7-fold improvement in the bioaccumulation performance for nickel compared to controls, but also observed a drastic decrease in cell viability due to metabolic burden or inducer (IPTG) toxicity. Growth kinetic analysis revealed the IPTG concentrations used based on past studies lead to growth inhibition, thus delineating future avenues for optimization of the engineered strain and its growth conditions to perform in more complex environments.

A multi-functional reagent suitable for 1-step rapid DNA intercalation fluorescence-based screening of total bacteria in drinking water

The prerequisites for rapid screening of total bacteria in drinking water are low detection limit and convenience. Inspired by commercial adenosine 5'-triphosphate (ATP) based total bacterial detection kits, we pursued likewise convenience but with much lower detection limit. Existing intercalation fluorescence-based techniques employ multiple reagents to permeate the cell membrane and intercalate dye into the DNA in discrete sequential steps. A simple multi-functional reagent is proposed to do the same within one step. Surfactants (TritonX and SDS), and intercalating dyes (SYBR green, SYBR gold) were examined for their mutual compatibility and augmented with EDTA. Evaluation was performed with Gram negative Escherichia coli K12 (E. coli K12) and Gram positive Bacillus subtilis (B. subtilis) at serial dilution ratios from 10^-6 to 10^-2. Comparison was made with absorbance (600 nm) measurements and a commercial ATP kit. Using charge integrated photodetection, the proposed 1-step reagent achieved an LOD (1.00 × 10^-6, B. subtilis) that is two orders of magnitude lower than that of ATP kit (LOD = 1.06× 10^-4). This means it could detect minute quantity of total bacteria that is otherwise undetected by the ATP kit.

A novel sustainable platform for scaled manufacturing of double-stranded RNA biopesticides

RNA interference (RNAi) represents one of the most conserved pathways evolved by eukaryotic cells for regulating gene expression. RNAi utilises non-translatable double-stranded RNA (dsRNA) molecules to sequester or degrade mRNA molecules gene. In RNAi, specifically designed exogenous dsRNA delivered to the cell can silence a target gene, a phenomenon that has been exploited in many functional studies and explored in biopesticide applications. The search for safe and sustainable crop pest management options drives the need to offset the effect of inorganic pesticides on biodiversity. The prospect of replacing inorganic pesticides with dsRNA crop spray is gaining popularity, enhanced by its high-target specificity and low environmental impact. However, for dsRNA to reach the pesticide market, it must be produced cost-effectively and sustainably. In this paper, we develop a high-yield expression media that generates up to 15-fold dsRNA yield compared to existing expression media utilising 1 mM IPTG. We also optimise a low-cost purification method that generates high-quality and purified dsRNA. The developed method circumvents the need for hazardous chemical reagents often found in commercial kits or commercial nucleases to eliminate contaminating DNA or single-stranded RNA (ssRNA) species. We also demonstrate that the production platform is scalable, generating 6.29 mg dsRNA from 259 mg wet E. coli cell pellet. The results also provide structural insights into the heterogeneous dsRNA species within the microbial-derived dsRNA pool. Finally, we also show that the purified 'naked' dsRNA, without prior formulation, can induce insect toxicity under field conditions. This study provides a novel, complete, low-cost process dsRNA platform with potential for application in industrial dsRNA production.

sPLA2 Wobbles on the Lipid Bilayer between Three Positions, Each Involved in the Hydrolysis Process

Secreted phospholipases A2 (sPLA2s) are peripheral membrane enzymes that hydrolyze phospholipids in the sn-2 position. The action of sPLA2 is associated with the work of two active sites. One, the interface binding site (IBS), is needed to bind the enzyme to the membrane surface. The other one, the catalytic site, is needed to hydrolyze the substrate. The interplay between sites, how the substrate protrudes to, and how the hydrolysis products release from, the catalytic site remains in the focus of investigations. Here, we report that bee venom PLA2 has two additional interface binding modes and enzyme activity through constant switching between three different orientations (modes of binding), only one of which is responsible for substrate uptake from the bilayer. The finding was obtained independently using atomic force microscopy and molecular dynamics. Switching between modes has biological significance: modes are steps of the enzyme moving along the membrane, product release in biological milieu, and enzyme desorption from the bilayer surface.

Role of detergents and nuclease inhibitors in the extraction of RNA from eukaryotic cells in complex matrices

The potential for liquid biopsy samples to be used in place of more invasive tissue biopsies has become increasingly revalent as it has been found that nucleic acids (NAs) present in the blood of cancer patients originate from tumors. Nanomagnetic extraction has proven to be a highly effective means to rapidly prepare NA from clinical samples for molecular diagnostics. In this article, the lysis reaction used to extract RNA from the human epithelial melanoma cells have been optimized using silica coated superparamagnetic nanoparticles (SPM NP). The lysis buffer (LB) is composed of several agents that denature cells, i.e., surfactant and guanidinium isothiocyanate (GITC), and agents that inhibit the degradation of circulated nucleic acids (cfNAs). The surfactant Triton X-100 has been widely used in LB but has been placed on the European Union REACH list. We have compared the qRT-PCR sensitivity resulting from LBs composed of Triton X-100 to several sustainable surfactants, i.e., Tergitol 15-S-7, Tergitol 15-S-9 and Tween-20. Surprisingly, the inclusion of these surfactants in the LB was not found to significantly improve cell lysis, and subsequently the sensitivity of qRT-PCR. The role of the sample matrix was also examined by performing extractions from solutions containing up to 30 mg mL^-1 serum albumin. The qRT-PCR sensitivity was found to decrease as the concentration of this protein was increased; however, this was linked to an increased RNase activity and not the concentration of the protein itself. These results lead us to recommend a reformulation of LB for clinical samples, and to conclude that sensitive qRT-PCR RNA analysis can be performed in serum with the timely addition of an RNase inhibitor.

Effects of Supplemental Drugs on Hexaminolevulinate (HAL)-Induced PpIX Fluorescence in Bladder Cancer Cell Suspensions

Seven different inhibitors of the heme metabolic pathway were applied in combination with HAL to study the formation of PpIX in bladder cancer HT1197 and normal fibroblast HFFF2 cells ex vivo, specifically with the aim to increase the fluorescence contrast between cancer and non-cancer cells. The mRNA expression of enzymes involved in the heme biosynthesis pathway were measured via PCR following incubation with the drugs in order to link the fluorescence levels and metabolic activity. The exogenous administration of HAL does lead to cancer-specific PpIX accumulation. However, the contrast between cancer and normal cells in suspension was not enhanced by the enzyme inhibitors and iron-chelating agents tested, nor did the mRNA expression necessarily correlate with the fluorescence intensity. The results indicate that a difference in the metabolic activity of cells in suspension may limit the applicability of exogenous enzyme inhibitor administration as a mean to improve the fluorescence-based detection of cancer cells shed in body fluids.

Chemical Reporters for Bacterial Glycans: Development and Applications

Bacteria possess an extraordinary repertoire of cell envelope glycans that have critical physiological functions. Pathogenic bacteria have glycans that are essential for growth and virulence but are absent from humans, making them high-priority targets for antibiotic, vaccine, and diagnostic development. The advent of metabolic labeling with bioorthogonal chemical reporters and small-molecule fluorescent reporters has enabled the investigation and targeting of specific bacterial glycans in their native environments. These tools have opened the door to imaging glycan dynamics, assaying and inhibiting glycan biosynthesis, profiling glycoproteins and glycan-binding proteins, and targeting pathogens with diagnostic and therapeutic payload. These capabilities have been wielded in diverse commensal and pathogenic Gram-positive, Gram-negative, and mycobacterial species─including within live host organisms. Here, we review the development and applications of chemical reporters for bacterial glycans, including peptidoglycan, lipopolysaccharide, glycoproteins, teichoic acids, and capsular polysaccharides, as well as mycobacterial glycans, including trehalose glycolipids and arabinan-containing glycoconjugates. We cover in detail how bacteria-targeting chemical reporters are designed, synthesized, and evaluated, how they operate from a mechanistic standpoint, and how this information informs their judicious and innovative application. We also provide a perspective on the current state and future directions of the field, underscoring the need for interdisciplinary teams to create novel tools and extend existing tools to support fundamental and translational research on bacterial glycans.

Bacterial safety study of the production process of hemoglobin-based oxygen carriers

Hemoglobin microparticles (HbMP) produced with a three-step procedure, including coprecipitation of hemoglobin with manganese carbonate, protein cross-linking, and dissolution of the carbonate template were shown to be suitable for application as artificial oxygen carriers. First preclinical safety investigations delivered promising results. Bacterial safety plays a decisive role during the production of HbMP. Therefore, the bioburden and endotoxin content of the starting materials (especially hemoglobin) and the final particle suspension are intensively tested. However, some bacteria may not be detected by standard tests due to low concentration. The aim of this study was to investigate how these bacteria would behave in the fabrication process. Biocidal effects are known for glutaraldehyde and for ethylenediaminetetraacetic acid, chemicals that are used in the fabrication process of HbMP. It was shown that both chemicals prevent bacterial growth at the concentrations used during HbMP fabrication. In addition, the particle production was carried out with hemoglobin solutions spiked with Escherichia coli or Staphylococcus epidermidis. No living bacteria could be detected in the final particle suspensions. Therefore, we conclude that the HbMP fabrication procedure is safe in respect of bacterial contamination.

Tolerance and safety evaluation of L-glutamic acid, N,N-diacetic acid as a feed additive in broiler diets

The novel chelator, L-glutamic acid, N,N-diacetic acid (GLDA) can be used as a dietary ingredient to safely reduce Zn supplementation in complete feed, without compromising the Zn status of farm animals. The objective of this study was to study dietary tolerance, bioaccumulation, and evaluate the safety of GLDA when supplemented in broiler diets at 0, 100, 300, 1000, 3,000, and 10,000 mg/kg. A total of 480 one-day-old Ross 308 male broilers were randomly allocated to 48 pens and fed one of the 6 experimental diets. Production performance was used to assess tolerance to the additive. At trial end, toxicity was evaluated using hematology, plasma biochemistry (n = 144) and gross necropsy (n = 48). Residue levels of GLDA were assessed in liver, kidney and breast tissue of birds used for necropsy. Performance showed an increase (P < 0.05) in body weight for GLDA inclusion at 300 mg/kg. A decrease on the measured performance parameters was found for the 10,000 mg/kg GLDA inclusion level (P < 0.05). The additive was added as a tetra-sodium salt, leading to sodium levels being 2.5 times higher in the latter treatment compared to the control diet which may have led to impaired intestinal barrier function. Mortality was not different between treatments. Residue levels for GLDA at the highest inclusion indicate that 0.0005% of total GLDA consumption is accumulated in breast tissue. Higher values of GLDA were found in kidney and liver at the highest inclusion level, potentially confirming that the small fraction of GLDA absorbed was readily excreted by the animal. At 100 and 300 mg/kg GLDA inclusion there were negligible amounts of GLDA present in all tissues measured. The present experiment demonstrated a high dietary tolerance to GLDA in broilers and indicated that GLDA does not pose a significant risk to food safety when supplemented below 3,000 mg/kg.

Insights into the antibacterial mechanism of action of chelating agents by selective deprivation of iron, manganese and zinc

Bacterial growth and proliferation can be restricted by limiting the availability of metal ions in their environment. Humans sequester iron, manganese, and zinc to help prevent infection by pathogens, a system termed nutritional immunity. Commercially used chelants have high binding affinities with a variety of metal ions, which may lead to antibacterial properties that mimic these innate immune processes. However, the modes of action of many of these chelating agents in bacterial growth inhibition and their selectivity in metal deprivation in cellulo remain ill-defined. We address this shortcoming by examining the effect of 11 chelators on Escherichia coli growth and their impact on the cellular concentration of five metals. The following four distinct effects were uncovered: (i) no apparent alteration in metal composition, (ii) depletion of manganese alongside reductions in iron and zinc levels, (iii) reduced zinc levels with a modest reduction in manganese, and (iv) reduced iron levels coupled with elevated manganese. These effects do not correlate with the absolute known chelant metal ion affinities in solution; however, for at least five chelators for which key data are available, they can be explained by differences in the relative affinity of chelants for each metal ion. The results reveal significant insights into the mechanism of growth inhibition by chelants, highlighting their potential as antibacterials and as tools to probe how bacteria tolerate selective metal deprivation.

IMPORTANCE Chelating agents are widely used in industry and consumer goods to control metal availability, with bacterial growth restriction as a secondary benefit for preservation. However, the antibacterial mechanism of action of chelants is largely unknown, particularly with respect to the impact on cellular metal concentrations. The work presented here uncovers distinct metal starvation effects imposed by different chelants on the model Gram-negative bacterium Escherichia coli. The chelators were studied both individually and in pairs, with the majority producing synergistic effects in combinations that maximize antibacterial hostility. The judicious selection of chelants based on contrasting cellular effects should enable reductions in the quantities of chelant required in numerous commercial products and presents opportunities to replace problematic chemistries with biodegradable alternatives.

Development of Drug-Resistant Klebsiella pneumoniae Vaccine via Novel Vesicle Production Technology

Drug resistance of Klebsiella pneumoniae severely threatens human health. Overcoming the mechanisms of K. pneumoniae resistance to develop novel vaccines against drug-resistant K. pneumoniae is highly desired. Here, we report a technology platform that uses high pressure to drive drug-resistant K. pneumoniae to pass through a gap, inducing the formation of stable artificial bacterial biomimetic vesicles (BBVs). These BBVs had little to no bacterial intracellular protein or nucleic acid and had high yields. BBVs were efficiently taken up by dendritic cells to stimulate their maturation. BBVs as K. pneumoniae vaccines had the dual functions of inducing bacteria-specific humoral and cellular immune responses to increase animals' survival rate and reduce pulmonary inflammation and bacterial loads. We believe that BBVs are new-generation technology for bacterial vesicle preparation. Establishment of this BBV vaccine platform can maximally expand preparation technology for vaccines against drug-resistant K. pneumoniae.

Subcompartmentalization and Pseudo-Division of Model Protocells

Membrane enclosed intracellular compartments have been exclusively associated with the eukaryotes, represented by the highly compartmentalized last eukaryotic common ancestor. Recent evidence showing the presence of membranous compartments with specific functions in archaea and bacteria makes it conceivable that the last universal common ancestor and its hypothetical precursor, the protocell, may have exhibited compartmentalization. To the authors' knowledge, there are no experimental studies yet that have tested this hypothesis. They report on an autonomous subcompartmentalization mechanism for protocells which results in the transformation of initial subcompartments to daughter protocells. The process is solely determined by the fundamental materials properties and interfacial events, and does not require biological machinery or chemical energy supply. In the light of the authors' findings, it is proposed that similar events may have taken place under early Earth conditions, leading to the development of compartmentalized cells and potentially, primitive division.

Evaluation of Cell-detaching Effect of EDTA in Combination with Oxaliplatin for a Possible Application in HIPEC After Cytoreductive Surgery: A Preliminary in-vitro Study

BACKGROUND

Ethylenediaminetetraacetic acid (EDTA), a commonly used compound in laboratory medicine, is known for its membrane-destabilization capacity and cell-detaching effect. This preliminary study aims to assess the potential of EDTA in removing residual tumor cell clusters. Using an in-vitro model, this effect is then compared to the cytotoxic effect of oxaliplatin which is routinely administered during HIPEC procedures. The overall cell toxicity and cell detaching effects of EDTA are compared to those of Oxaliplatin and the additive effect is quantified.

METHODS

HT-29 (ATCC® HTB-38™) cells were treated with A) EDTA only B) Oxaliplatin only and C) both agents using an in-vitro model. Cytotoxicity and cell detachment following EDTA application were measured via colorimetric MTS assay. Additionally, detached cell groups were visualized using light microscopy and further analyzed by means of electron microscopy.

RESULTS

When solely applied, EDTA does not exhibit any cell toxicity nor does it add any toxicity to oxaliplatin. However, EDTA enhances the detachment of adherent colon carcinoma cells by removing up to 65% (p<0.05) of the total initial cell amount. In comparison, the sole application of highly concentrated oxaliplatin induced cell mortality by up to 66% (p<0.05). While detached cells showed no mortality after EDTA treatment, cell clusters exhibited a decreased amount of extracellular and adhesive matrix in-between cells. When combined, Oxaliplatin and EDTA display a significant additive effect with only 30% (mean p <0.01) of residual vitality detected in the initial well. EDTA and Oxaliplatin remove up to 81% (p <0.01) of adhesive HT-29 cells from the surface either by cytotoxic effects or cell detachment.

CONCLUSION

Our data support EDTA's potential to remove microscopical tumor cell clusters from the peritoneum and possibly act as a supplementary agent in HIPEC procedures with chemotherapy. While adding EDTA to HIPEC procedures may significantly decrease the risk of PM recurrence, further in-vivo and clinical trials are required to evaluate this effect.

A General Workflow for Characterization of Nernstian Dyes and Their Effects on Bacterial Physiology

The electrical membrane potential (V_m) is one of the components of the electrochemical potential of protons across the biological membrane (proton motive force), which powers many vital cellular processes. Because V_m also plays a role in signal transduction, measuring it is of great interest. Over the years, a variety of techniques have been developed for the purpose. In bacteria, given their small size, Nernstian membrane voltage probes are arguably the favorite strategy, and their cytoplasmic accumulation depends on V_m according to the Nernst equation. However, a careful calibration of Nernstian probes that takes into account the tradeoffs between the ease with which the signal from the dye is observed and the dyes’ interactions with cellular physiology is rarely performed. Here, we use a mathematical model to understand such tradeoffs and apply the results to assess the applicability of the Thioflavin T dye as a V_m sensor in Escherichia coli. We identify the conditions in which the dye turns from a V_m probe into an actuator and, based on the model and experimental results, propose a general workflow for the characterization of Nernstian dye candidates.

Isolation and Profiling of Circulating Tumor-Associated Exosomes Using Extracellular Vesicular Lipid-Protein Binding Affinity Based Microfluidic Device

Extracellular vesicles (EVs) are emerging as a potential diagnostic test for cancer. Owing to the recent advances in microfluidics, on-chip EV isolation is showing promise with respect to improved recovery rates, smaller necessary sample volumes, and shorter processing times than ultracentrifugation. Immunoaffinity-based microfluidic EV isolation using anti-CD63 is widely used; however, anti-CD63 is not specific to cancer-EVs, and some cancers secrete EVs with low expression of CD63. Alternatively, phosphatidylserine (PS), usually expressed in the inner leaflet of the lipid bilayer of the cells, is shown to be expressed on the outer surface of cancer-associated EVs. A new exosome isolation microfluidic device (new ExoChip), conjugated with a PS-specific protein, to isolate cancer-associated exosomes from plasma, is presented. The device achieves 90% capture efficiency for cancer cell exosomes compared to 38% for healthy exosomes and isolates 35% more A549-derived exosomes than an anti-CD63-conjugated device. Immobilized exosomes are then easily released using Ca2+ chelation. The recovered exosomes from clinical samples are characterized by electron microscopy and western-blot analysis, revealing exosomal shapes and exosomal protein expressions. The new ExoChip facilitates the isolation of a specific subset of exosomes, allowing the exploration of the undiscovered roles of exosomes in cancer progression and metastasis.

Changes in the Expression of Aquaporin-3 in the Gastrointestinal Tract Affect Drug Absorption

Aquaporin-3 (AQP3) plays an important role in water transport in the gastrointestinal (GI) tract. In this study, we conducted a Caco-2 cell permeability assay to examine how changes in the expression and function of AQP3 affect the rate at which a drug is absorbed via passive transport in the GI tract. When the function of AQP3 was inhibited by mercuric chloride or phloretin, there was no change in warfarin permeability. In contrast, when the expression of AQP3 protein was decreased by prostaglandin E₂ (PGE₂) treatment, warfarin permeability increased to approximately twice the control level, and membrane fluidity increased by 15%. In addition, warfarin permeability increased to an extent comparable to that after PGE₂ treatment when cell membrane fluidity was increased by 10% via boric acid/EDTA treatment. These findings suggest the possibility that the increased drug absorption under decreased AQP3 expression was attributable to increased membrane fluidity. The results of this study demonstrate that the rate of water transport has little effect on drug absorption. However, our findings also indicate that although AQP3 and other similar transmembrane proteins do not themselves transport drugs, changes in their expression levels can cause changes in cell membrane fluidity, thus affecting drug absorption rates.

Development and Optimization of the Biological Conversion of Ethane to Ethanol Using Whole-Cell Methanotrophs Possessing Methane Monooxygenase

The biological production of ethanol from ethane for the utilization of ethane in natural gas was investigated under ambient conditions using whole-cell methanotrophs possessing methane monooxygenase. Several independent variables including ethane concentration and biocatalyst amounts, among other factors, were optimized for the enhancement of ethane-to-ethanol bioconversion. We obtained 0.4 g/L/h of volumetric productivity and 0.52 g/L of maximum titer in optimum batch reaction conditions. In this study, we demonstrate that the biological gas-to-liquid conversion of ethane to ethanol has potent technical feasibility as a new application of ethane gas.

Transparent Copper-Based Antibacterial Coatings with Enhanced Efficacy against Pseudomonas aeruginosa

Bacterial surface contamination is a major cause of hospital-associated infections. Antibacterial coatings can play an important role in reducing bacterial transmission via inanimate surfaces in healthcare settings. In this work, transparent copper-based antibacterial coatings were fabricated on commercial poly(vinyl fluoride) and stainless steel. Acrylated quaternized chitosan and ethylenediaminetetraacetic acid were covalently grafted on the substrate for complexation with copper ions. The number of viable Staphylococcus aureus in a droplet [containing ∼10⁴ colony forming units (CFU)], deposited on the copper-containing coating decreased by ∼96% within 60 min at 25 °C. With Pseudomonas aeruginosa, one of the most virulent and hardest to kill bacteria, no CFU could be observed within the same time span (killing efficacy >99.8% based on the detection limit). An increase in copper release from the coating was observed in the presence of P. aeruginosa, which was postulated to be due to the proteolytic activity of P. aeruginosa. The higher efficacy of the coating against P. aeruginosa compared to S. aureus is thus attributed to this increased copper release from the coating, which resulted in extensive bacterial membrane damage and death. The copper-containing coating on poly(vinyl fluoride) retained its antibacterial efficacy after 100 wipes with a water-wetted cloth or isopropanol wipes, demonstrating its durability and long-term efficacy. The coating did not exhibit significant cytotoxicity toward mammalian fibroblasts, further demonstrating its potential for mitigating bacterial transmission in a clinical setting.

A trivalent Apx-fusion protein delivered by E. coli outer membrane vesicles induce protection against Actinobacillus pleuropneumoniae of serotype 1 and 7 challenge in a murine model

Actinobacillus pleuropneumoniae (APP) causes serious economic losses in the swine industry, and is the etiologic agent of porcine pleuropneumonia. In this study we have engineered a trivalent Apx fusion protein enclosed in outer membrane vesicles (Apxr-OMV) and studied its immunoprotective efficacy against APP serotypes 1 and 7 challenge in mice. The results showed that the IgG levels in the Apxr-OMVs immune group were significantly higher than those of the negative control (P < 0.05). Up-regulation of both Th1 (IFN-γ, IL-2) and Th2 (IL-4) cytokines were detected in splenocytes of Apxr-OMVs immune group. The survival rates 87.5% and 62.5% were observed against APP strain 1516 of serotype 7 and APP strain 2701 of serotype 1 in the groups of Apxr-OMVs immune group, respectively. Histopathological lesions of the pulmonary structure alveoli were found to be minimal in APX-OMV group challenged with APP serotypes 1 and 7. These results strongly indicated that engineered OMVs could effectively induce specific humoral or cellular immune responses. Moreover, Apxr-OMVs used as novel vaccine provides cross-protective immunity against different serotype 1 and 7 of APP infection in a mouse model. In contrast, the OMV-empty and PBS as negative controls or inactivated strain of APP-2701 and APP-1516 as positive controls for the animal study cannot provide protection or cross-protection.

H+- and Na+- elicited rapid changes of the microtubule cytoskeleton in the biflagellated green alga Chlamydomonas

Although microtubules are known for dynamic instability, the dynamicity is considered to be tightly controlled to support a variety of cellular processes. Yet diverse evidence suggests that this is not applicable to Chlamydomonas, a biflagellate fresh water green alga, but intense autofluorescence from photosynthesis pigments has hindered the investigation. By expressing a bright fluorescent reporter protein at the endogenous level, we demonstrate in real time discreet sweeping changes in algal microtubules elicited by rises of intracellular H⁺ and Na⁺. These results from this model organism with characteristics of animal and plant cells provide novel explanations regarding how pH may drive cellular processes; how plants may respond to, and perhaps sense stresses; and how organisms with a similar sensitive cytoskeleton may be susceptible to environmental changes.

Antimicrobial activity of coriander oil and its effectiveness as food preservative

ABTRACT Foodborne illness represents a major economic burden worldwide and a serious public health threat, with around 48 million people affected and 3,000 death each year only in the USA. One of the possible strategies to reduce foodborne infections is the development of effective preservation strategies capable of eradicating microbial contamination of foods. Over the last years, new challenges for the food industry have arisen such as the increase of antimicrobial resistance of foodborne pathogens to common preservatives and consumers demand for naturally based products. In order to overcome this, new approaches using natural or bio-based products as food preservatives need to be investigated. Coriander (Coriandrum sativum L.) is a well-known herb widely used as spice, or in folk medicine, and in the pharmacy and food industries. Coriander seed oil is the world's second most relevant essential oil, exhibiting antimicrobial activity against Gram-positive and Gram-negative bacteria, some yeasts, dermatophytes and filamentous fungi. This review highlights coriander oil antimicrobial activity and possible mechanisms of action in microbial cells and discusses the ability of coriander oil usage as a food preservative, pointing out possible paths for the successful evolution for these strategies towards a successful development of a food preservation strategy using coriander oil.

Increased Uptake of Chelated Copper Ions by Lolium perenne Attributed to Amplified Membrane and Endodermal Damage

The contributions of mechanisms by which chelators influence metal translocation to plant shoot tissues are analyzed using a combination of numerical modelling and physical experiments. The model distinguishes between apoplastic and symplastic pathways of water and solute movement. It also includes the barrier effects of the endodermis and plasma membrane. Simulations are used to assess transport pathways for free and chelated metals, identifying mechanisms involved in chelate-enhanced phytoextraction. Hypothesized transport mechanisms and parameters specific to amendment treatments are estimated, with simulated results compared to experimental data. Parameter values for each amendment treatment are estimated based on literature and experimental values, and used for model calibration and simulation of amendment influences on solute transport pathways and mechanisms. Modeling indicates that chelation alters the pathways for Cu transport. For free ions, Cu transport to leaf tissue can be described using purely apoplastic or transcellular pathways. For strong chelators (ethylenediaminetetraacetic acid (EDTA) and diethylenetriaminepentaacetic acid (DTPA)), transport by the purely apoplastic pathway is insufficient to represent measured Cu transport to leaf tissue. Consistent with experimental observations, increased membrane permeability is required for simulating translocation in EDTA and DTPA treatments. Increasing the membrane permeability is key to enhancing phytoextraction efficiency.

Exploring the chemical space of aromatase inhibitors

Aromatase, a rate-limiting enzyme catalyzing the conversion of androgen to estrogen, is overexpressed in human breast cancer tissue. Aromatase inhibitors (AIs) have been used for the treatment of estrogen-dependent breast cancer in post-menopausal women by blocking the biosynthesis of estrogen. The undesirable side effects in current AIs have called for continued pursuit for novel candidates with aromatase inhibitory properties. This study explores the chemical space of all known AIs as a function of their physicochemical properties by means of univariate (i.e., statistical and histogram analysis) and multivariate (i.e., decision tree and principal component analysis) approaches in order to understand the origins of aromatase inhibitory activity. Such a non-redundant set of AIs spans a total of 973 compounds encompassing both steroidal and non-steroidal inhibitors. Substructure analysis of the molecular fragments provided pertinent information on the structural features important for ligands providing high and low aromatase inhibition. Analyses were performed on data sets stratified according to their structural scaffolds (i.e., steroids and non-steroids) and bioactivities (i.e., actives and inactives). These analyses have uncover a set of rules characteristic to active and inactive AIs as well as revealing the constituents giving rise to potent aromatase inhibition.

Influence of chelation on Cu distribution and barriers to translocation in lolium perenne

Strong chelating agents are reported to enhance Cu translocation in plants; however, the mechanisms responsible have not yet been fully established. In this study, both ethylenediaminetetraacetic acid (EDTA) and diethylenetriamine pentaacetic acid (DTPA) were found to increase Cu translocation to shoot tissue, while citric acid did not. Although all three amendments decreased Cu sorption to roots, which should cause greater Cu mobility within plants, this did not correspond with translocation. Energy-dispersive X-ray analysis of root cell walls showed that the endodermis presented a barrier (albeit partial) to the movement of free Cu ions, but this effect was negated by amendment addition. With EDTA, Cu levels in the stele were higher than those in the cortex after 1 week of exposure. Using Si deposition as an indicator, the presence of free Cu increased endodermal development, while amendments prevented this effect. Confocal microscopy and lipid peroxidation observations show that Cu and citric acid increased membrane damage, while EDTA and DTPA had transient effects. Strong chelating agents are less damaging alone than when present in conjunction with elevated Cu levels. Chelating amendments are proposed to enhance Cu phytoextraction by facilitating transport across the endodermis, ostensibly by influencing both membrane integrity and endodermal development.

Cysteine depletion causes oxidative stress and triggers outer membrane vesicle release by Neisseria meningitidis; implications for vaccine development

Outer membrane vesicles (OMV) contain immunogenic proteins and contribute to in vivo survival and virulence of bacterial pathogens. The first OMV vaccines successfully stopped Neisseria meningitidis serogroup B outbreaks but required detergent-extraction for endotoxin removal. Current vaccines use attenuated endotoxin, to preserve immunological properties and allow a detergent-free process. The preferred process is based on spontaneously released OMV (sOMV), which are most similar to in vivo vesicles and easier to purify. The release mechanism however is poorly understood resulting in low yield. This study with N. meningitidis demonstrates that an external stimulus, cysteine depletion, can trigger growth arrest and sOMV release in sufficient quantities for vaccine production (±1500 human doses per liter cultivation). Transcriptome analysis suggests that cysteine depletion impairs iron-sulfur protein assembly and causes oxidative stress. Involvement of oxidative stress is confirmed by showing that addition of reactive oxygen species during cysteine-rich growth also triggers vesiculation. The sOMV in this study are similar to vesicles from natural infection, therefore cysteine-dependent vesiculation is likely to be relevant for the in vivo pathogenesis of N. meningitidis.

Formation of supported lipid bilayers at surfaces with controlled curvatures: influence of lipid charge

We have developed and characterized novel biomimetic membranes, formed at nanostructured sensor substrates with controlled curvatures, motivated by the many biological processes that involve membrane curvature. Model systems with convex nanostructures, with radii of curvatures (ROCs) of 70, 75, and 95 nm, were fabricated utilizing colloidal assembly and used as substrates for supported lipid bilayers (SLBs). The SLBs were formed via vesicle adsorption and rupture, and the vesicle deposition pathway was studied by means of quartz crystal microbalance with dissipation (QCM-D) and fluorescence microscopy. SLBs conforming to the underlying nanostructured surfaces, which exhibit increased surface area with decreased ROC, were confirmed from excess mass, monitored by QCM-D, and excess total fluorescence intensities. The formation of SLBs at the nanostructured surfaces was possible, however, depending on the ROC of the structures and the lipid vesicle charge the quality varied. The presence of nanostructures was shown to impair vesicle rupture and SLB formation was progressively hindered at surfaces with structures of decreasing ROCs. The introduction of a fraction of the positively charged lipid POEPC in the lipid vesicle membrane allowed for good quality and conformal bilayers at all surfaces. Alternatively, for vesicles formed from lipid mixtures with a fraction of the negatively charged lipid POPS, SLB formation was not at all possible at surfaces with the lowest ROC. Interestingly, the vesicle adsorption rate and the SLB formation were faster at surfaces with nanostructures of progressively smaller ROCs at high ratios of POPS in the vesicles. Development of templated SLBs with controlled curvatures provides a new experimental platform, especially at the nanoscale, at which membrane events such as lipid sorting, phase separation, and protein binding can be studied.

Molecular Docking of Aromatase Inhibitors

Aromatase is an enzyme that plays a critical role in the development of estrogen receptor positive breast cancer. As aromatase catalyzes the aromatization of androstenedione to estrone, a naturally occurring estrogen, it is a promising drug target for therapeutic management. The undesirable effects found in aromatase inhibitors (AIs) that are in clinical use necessitate the discovery of novel AIs with higher selectivity, less toxicity and improving potency. In this study, we elucidate the binding mode of all three generations of AI drugs to the crystal structure of aromatase by means of molecular docking. It was demonstrated that the docking protocol could reliably reproduce the interaction of aromatase with its substrate with an RMSD of 1.350 Å. The docking study revealed that polar (D309, T310, S478 and M374), aromatic (F134, F221 and W224) and non-polar (A306, A307, V370, L372 and L477) residues were important for interacting with the AIs. The insights gained from the study herein have great potential for the design of novel AIs.

Lateral organization of membrane proteins: tetraspanins spin their web

Despite high expression levels at the plasma membrane or in intracellular vesicles, tetraspanins remain among the most mysterious transmembrane molecules 20 years after their discovery. Several genetic studies in mammals and invertebrates have demonstrated key physiological roles for some of these tetraspanins, in particular in the immune response, sperm-egg fusion, photoreceptor function and the normal function of certain epithelia. Other studies have highlighted their ability to modulate cell migration and metastasis formation. Their role in the propagation of infectious agents has drawn recent attention, with evidence for HIV budding in tetraspanin-enriched plasma membrane domains. Infection of hepatocytic cells by two major pathogens, the hepatitis C virus and the malaria parasite, also requires the tetraspanin CD81. The function of tetraspanins is thought to be linked to their ability to associate with one another and a wealth of other integral proteins, thereby building up an interacting network or 'tetraspanin web'. On the basis of the biochemical dissection of the tetraspanin web and recent analysis of the dynamics of some of its constituents, we propose that tetraspanins tightly regulate transient interactions between a variety of molecules and as such favour the efficient assembly of specialized structures upon proper stimulation.

A strategic crossflow filtration methodology for the initial purification of promegapoietin from inclusion bodies

A novel crossflow filtration methodology is demonstrated for the initial purification of the therapeutic protein, promegapoietin-1a (PMP), produced as inclusion bodies (IBs) in a recombinant Escherichia coli bioprocess. Two strategic separation steps were performed by utilizing a filtration unit with a 1000 kDa polyethersulphone membrane. The first step, aiming for separation of soluble contaminants, resulted in a 50% reduction of the host cell proteins, quantified by total amino acid analysis and a 70% reduction of all DNA, quantified by fluorometry, when washing the particulate material with a 10mM EDTA in 50mM phosphate buffer, pH 8. The second step, aiming for separation of particulate contaminants from solubilized IBs, resulted in a 97-99.5% reduction of endotoxin, used as a marker for cell debris, and was quantified by the kinetic turbidimetric LAL endotoxin assay. The overall PMP yield was 58% and 33% respectively for the two solubilizations investigated, guanidine hydrochloride and arginine, as measured by RP-HPLC. The scope was also to investigate the physical characteristics of the intermediate product/s with regard to the choice of IB solvent. Preliminary results from circular dichroism spectroscopy measurements indicate that the protein secondary structure was restored when arginine was used in the second step.