ABSTRACT
Simultaneous water and ethanol-based synthesis and coating of copper and zinc oxide (CuO/ZnO) nanoparticles (NPs) on bandages was carried out by ultrasound irradiation. High resolution-transmission electron microscopy demonstrated the effects of the solvent on the particle size and shape of metal oxide NPs. An antibacterial activity study of metal-oxide-coated bandages was carried out against Staphylococcus aureus (Gram-positive) and Escherichia coli (Gram-negative). CuO NP-coated bandages made from both water and ethanol demonstrated complete killing of S. aureus and E. coli bacteria within 30 min., whereas ZnO NP-coated bandages demonstrated five-log reductions in viability for both kinds of bacteria after 60 min of interaction. Further, the antibacterial mechanism of CuO/ZnO NP-coated bandages is proposed here based on electron spin resonance studies. Nanotoxicology investigations were conducted via in vivo examinations of the effect of the metal-oxide bandages on frog embryos (teratogenesis assay-Xenopus). The results show that water-based coatings resulted in lesser impacts on embryo development than the ethanol-based ones. These bandages should therefore be considered safer than the ethanol-based ones. The comparison between the toxicity of the metal oxide NPs prepared in water and ethanol is of great importance, because water will replace ethanol for bulk scale synthesis of metal oxide NPs in commercial companies to avoid further ignition problems. The novelty and importance of this manuscript is avoiding the ethanol in the typical water:ethanol mixture as the solvent for the preparation of metal oxide NPs. Ethanol is ignitable, and commercial companies are trying the evade its use. This is especially important these days, as the face mask produced by sonochemistry (SONOMASK) is being sold all over the world by SONOVIA, and it is coated with ZnO.
ABSTRACT
Wastewater effluents are a reliable water source for non-potable water reuse including unrestricted crop irrigation in arid regions suffering from water scarcity. This study was performed to develop and optimize a procedure to concentrate coliphages from 100 L of treated effluent. Moreover, the reduction of coliphages by filtration and disinfection by either chlorine or UV was compared with that of fecal coliform (FC). The adsorption efficiency of MS2 and Qß coliphages by the NanoCeram filter was similar and reached 99.8%. Elution efficiency of MS2 coliphage from the NanoCeram filters by a solution of 1% NaPP and 0.05 M glycine, pH 9.5, was 74 ± 9.5%. The highest reconcentration efficiency of MS2 and Qß coliphages was obtained with polyethylene glycol (PEG) precipitation and reached 76 ± 28% and 90 ± 11%, respectively. In comparison, the reconcentration efficiency of organic flocculation was 0% and 1.3% for Qß and MS2 coliphages, respectively. The overall recovery efficiency of MS2 coliphages from 100 L tertiary effluent was 57 ± 1.5%. Poor reduction was observed for coliphages compared to FC by filtration and chlorine disinfection although; the reduction of FC, as measured by cultivation, was satisfactory and within the guidelines for unrestricted irrigation. High correlation between the reduction of FC and coliphages was recorded for tertiary effluent disinfected by UV irradiation. Monitoring the microbial quality of tertiary effluent using qPCR for the enumeration of FC was found unsuitable, because DNA levels were unaffected by the treatment processes. The results of this study demonstrated that monitoring the microbial quality of tertiary effluent by FC may not reflect the health risks encountered by the application of these effluents and the addition of coliphages to the monitoring programs may allow for accurate assessment of the health risks introduced by the application of tertiary effluent.
Subject(s)
Chlorine/pharmacology , Coliphages/drug effects , Coliphages/radiation effects , Disinfectants/pharmacology , Disinfection/methods , Wastewater/virology , Water Purification/methods , Coliphages/genetics , Coliphages/growth & development , Disinfection/instrumentation , Filtration , Ultraviolet Rays , Wastewater/chemistry , Water Purification/instrumentationABSTRACT
To interact with the egg, the spermatozoon must undergo several biochemical and motility modifications in the female reproductive tract, collectively called capacitation. Only capacitated sperm can undergo acrosomal exocytosis, near or on the egg, a process that allows the sperm to penetrate and fertilize the egg. In the present study, we investigated the involvement of cyclic adenosine monophosphate (cAMP)-dependent processes on acrosomal exocytosis. Inhibition of protein kinase A (PKA) at the end of capacitation induced acrosomal exocytosis. This process is cAMP-dependent; however, the addition of relatively high concentration of the membrane-permeable 8-bromo-cAMP (8Br-cAMP, 0.1 mmol l-1) analog induced significant inhibition of the acrosomal exocytosis. The induction of acrosomal exocytosis by PKA inhibition was significantly inhibited by an exchange protein directly activated by cAMP (EPAC) ESI09 inhibitor. The EPAC selective substrate activated AE at relatively low concentrations (0.02-0.1 µmol l-1), whereas higher concentrations (>5 µmol l-1) were inhibitory to the AE induced by PKA inhibition. Inhibition of PKA revealed about 50% increase in intracellular cAMP levels, conditions under which EPAC can be activated to induce the AE. Induction of AE by activating the actin severing-protein, gelsolin, which causes F-actin dispersion, was inhibited by the EPAC inhibitor. The AE induced by PKA inhibition was mediated by phospholipase C activity but not by the Ca2+-channel, CatSper. Thus, inhibition of PKA at the end of the capacitation process induced EPAC/phospholipase C-dependent acrosomal exocytosis. EPAC mediates F-actin depolymerization and/or activation of effectors downstream to F-actin breakdown that lead to acrosomal exocytosis.
Subject(s)
Acrosome Reaction/drug effects , Cyclic AMP-Dependent Protein Kinases/antagonists & inhibitors , Exocytosis/drug effects , Guanine Nucleotide Exchange Factors/metabolism , Protein Kinase Inhibitors/pharmacology , Spermatozoa/drug effects , 8-Bromo Cyclic Adenosine Monophosphate/pharmacology , Acrosome/drug effects , Acrosome/metabolism , Calcimycin/pharmacology , Cyclic AMP/metabolism , Humans , Male , Signal Transduction/drug effects , Spermatozoa/metabolism , Thapsigargin/pharmacologyABSTRACT
The organization and expression of Pseudomonas stutzeri ST-9 genes related to toluene catabolism and porin synthesis was investigated. Toluene-degrading genes were found to be localized in the chromosome close to a phage-type integrase. A regulatory gene and 21 genes related to an aromatics degradation pathway are organized as a putative operon. These proteins are upregulated in the presence of toluene. Fourteen outer membrane proteins were identified as porins in the ST-9 genome. The identified porins showed that the main detected porins are related to the OmpA and OprD superfamilies. The percentage of porins in the outer membrane protein fraction, as determined by mass spectrometry, was 73% and 54% when the cells were cultured with toluene and with glucose, respectively. Upregulation of OmpA and downregulation of OprD occurred in the presence of toluene. A porin fraction (90% OprD) from both cultures was isolated and examined as a toluene uptake system using the liposome-swelling assay. Liposomes were prepared with the porin fraction from a culture that was grown on toluene (T-proteoliposome) or glucose (G-proteoliposome). There was no significant difference in the permeability rate of the different solutes through the T-proteoliposome and the G-proteoliposome.
Subject(s)
Porins/biosynthesis , Proteomics , Pseudomonas stutzeri/genetics , Toluene/metabolism , Bacterial Outer Membrane Proteins/biosynthesis , Bacterial Outer Membrane Proteins/genetics , Gene Expression Regulation, Bacterial/drug effects , Glucose/metabolism , Glucose/pharmacology , Liposomes/metabolism , Mass Spectrometry , Porins/genetics , Pseudomonas stutzeri/growth & development , Pseudomonas stutzeri/metabolism , Toluene/pharmacologyABSTRACT
Advanced wastewater treatment processes are applied to prevent the environmental dissemination of pathogenic microorganisms. Giardia lamblia causes a severe disease called giardiasis, and is highly prevalent in untreated wastewater worldwide. Monitoring the microbial quality of wastewater effluents is usually based on testing for the levels of indicator microorganisms in the effluents. This study was conducted to compare the suitability of fecal coliforms, F+ coliphages and sulfide reducing clostridia (SRC) as indicators for the reduction of Giardia cysts in two full-scale wastewater treatment plants. The treatment process consists of activated sludge, coagulation, high rate filtration and either chlorine or UV disinfection. The results of the study demonstrated that Giardia cysts are highly prevalent in raw wastewater at an average concentration of 3600 cysts/L. Fecal coliforms, F+ coliphages and SRC were also detected at high concentrations in raw wastewater. Giardia cysts were efficiently removed (3.6 log10) by the treatment train. The greatest reduction was observed for fecal coliforms (9.6 log10) whereas the least reduction was observed for F+ coliphages (2.1 log10) following chlorine disinfection. Similar reduction was observed for SRC by filtration and disinfection by either UV (3.6 log10) or chlorine (3.3 log10). Since F+ coliphage and SRC were found to be more resistant than fecal coliforms for the tertiary treatment processes, they may prove to be more suitable as indicators for Giardia. The results of this study demonstrated that advanced wastewater treatment may prove efficient for the removal of Giardia cysts and may prevent its transmission when treated effluents are applied for crop irrigation or streams restoration.
Subject(s)
Giardia/physiology , Wastewater/parasitology , Water Microbiology , Water Purification/methods , Clostridium/physiology , Coliphages/physiology , Humans , Waste Disposal, Fluid/methodsABSTRACT
Isolated toluene-degrading Pseudomonas stutzeri ST-9 bacteria were grown in a minimal medium containing toluene (100 mg·L(-1)) (MMT) or glucose (MMG) as the sole carbon source, with specific growth rates of 0.019 h(-1) and 0.042 h(-1), respectively. Scanning (SEM) as well as transmission (TEM) electron microscope analyses showed that the bacterial cells grown to mid-log phase in the presence of toluene possess a plasmolysis space. TEM analysis revealed that bacterial cells that were grown in MMT were surrounded by an additional "material" with small vesicles in between. Membrane integrity was analyzed by leakage of 260 nm absorbing material and demonstrated only 7% and 8% leakage from cultures grown in MMT compared with MMG. X-ray microanalysis showed a 4.3-fold increase in Mg and a 3-fold increase in P in cells grown in MMT compared with cells grown in MMG. Fluorescence-activated cell sorting (FACS) analysis indicated that the permeability of the membrane to propidium iodide was 12.6% and 19.6% when the cultures were grown in MMG and MMT, respectively. The bacterial cell length increased by 8.5% ± 0.1% and 17% ± 2%, as measured using SEM images and FACS analysis, respectively. The results obtained in this research show that the presence of toluene led to morphology changes, such as plasmolysis, cell size, and formation of outer membrane vesicles. However, it does not cause significant damage to membrane integrity.
Subject(s)
Carbon/metabolism , Extracellular Vesicles/drug effects , Glucose/metabolism , Pseudomonas stutzeri/drug effects , Toluene/toxicity , Cell Membrane/drug effects , Cell Membrane/ultrastructure , Cell Size/drug effects , Flow Cytometry , Osmotic Pressure , Pseudomonas stutzeri/ultrastructureABSTRACT
Wastewater disposal may be a source of environmental contamination by Cryptosporidium and Giardia. This study was conducted to evaluate the prevalence of Cryptosporidium oocysts and Giardia cysts in raw and treated wastewater effluents. A prevalence of 100% was demonstrated for Giardia cysts in raw wastewater, at a concentration range of 10 to 12,225 cysts L(-1), whereas the concentration of Cryptosporidium oocysts in raw wastewater was 4 to 125 oocysts L(-1). The removal of Giardia cysts by secondary and tertiary treatment processes was greater than those observed for Cryptosporidium oocysts and turbidity. Cryptosporidium and Giardia were present in 68.5% and 76% of the tertiary effluent samples, respectively, at an average concentration of 0.93 cysts L(-1) and 9.94 oocysts L(-1). A higher detection limit of Cryptosporidium oocysts in wastewater was observed for nested PCR as compared to immune fluorescent assay (IFA). C. hominis was found to be the dominant genotype in wastewater effluents followed by C. parvum and C. andersoni or C. muris. Giardia was more prevalent than Cryptosporidium in the studied community and treatment processes were more efficient for the removal of Giardia than Cryptosporidium. Zoonotic genotypes of Cryptosporidium were also present in the human community. To assess the public health significance of Cryptosporidium oocysts present in tertiary effluent, viability (infectivity) needs to be assessed.
Subject(s)
Cryptosporidium/isolation & purification , Giardia/isolation & purification , Wastewater/parasitology , Water Purification/methods , Animals , Coloring Agents/isolation & purification , Cryptosporidium/cytology , Enterobacteriaceae/cytology , Enterobacteriaceae/isolation & purification , Feces/microbiology , Feces/parasitology , Giardia/cytology , Humans , Oocysts/cytology , Recycling/methods , SeasonsABSTRACT
Strain ST-9 was isolated from toluene-contaminated soil (Samaria, Israel). The draft genome has an estimated size of 4.8 Mb, exhibits an average G+C content of 60.37%, and is predicted to encode 4,183 proteins, including a gene cluster for aromatic hydrocarbon degradation. It is assigned to genomovar 3 of Pseudomonas stutzeri.
ABSTRACT
The spread of antibiotic-resistant bacteria and parasites calls for the development of new therapeutic strategies with could potentially reverse this trend. Here, a proposal is presented to exploit a sonochemical method to restore the antibiotic activity of tetracycline (TTCL) against resistant bacteria by converting the antibiotic into a nanoparticulate form. The demonstrated sonochemical method allows nanoscale TTCL assembly to be driven by supramolecular hydrogen bond formation, with no further modification to the antibiotic's chemical structure. It is shown that tetracycline nanoparticles (TTCL NPs) can act as antibacterial agents, both against TTCL sensitive and against resistant bacterial strains. Moreover, the synthesized antibiotic nanoparticles (NPs) can act as effective gene-silencing agents through the use of a TTCL repressor in Trypanosome brucei parasites. It is demonstrated that the NPs are nontoxic to human cells and T. brucei parasites and are able to release their monomer components in an active form in a manner that results in enhanced antimicrobial activity relative to a homogeneous solution of the precursor monomer. As the TTCL NPs are biocompatible and biodegradable, sonochemical formation of TTCL NPs represents a new promising approach for generation of pharmaceutically active nanomaterials.
Subject(s)
Anti-Bacterial Agents/chemistry , Gene Silencing/drug effects , Nanoparticles/chemistry , Tetracycline/chemistry , Anti-Bacterial Agents/pharmacology , Cell Line , Humans , Microbial Viability/drug effects , Tetracycline/pharmacology , Trypanosoma brucei brucei/drug effects , Trypanosoma brucei brucei/genetics , Trypanosoma brucei brucei/metabolismABSTRACT
Aliphatic amines, including methylamine, are air-pollutants, due to their intensive use in industry and the natural degradation of proteins, amino acids, and other nitrogen-containing compounds in biological samples. It is necessary to develop systems for removal of methylamine from the air, since airborne methylamine has a negative effect on human health. The primary amine oxidase (primary amine : oxygen oxidoreductase (deaminating) or amine oxidase, AMO; EC 1.4.3.21), a copper-containing enzyme from the thermotolerant yeast Hansenula polymorpha which was overexpressed in baker's yeast Saccharomyces cerevisiae, was tested for its ability to oxidize airborne methylamine. A continuous fluidized bed bioreactor (CFBR) was designed to enable bioconversion of airborne methylamine by AMO immobilized in calcium alginate (CA) beads. The results demonstrated that the bioreactor with immobilized AMO eliminates nearly 97% of the airborne methylamine. However, the enzymatic activity of AMO causes formation of formaldehyde. A two-step bioconversion process was therefore proposed. In the first step, airborne methylamine was fed into a CFBR which contained immobilized AMO. In the second step, the gas flow was passed through another CFBR, with alcohol oxidase from the yeast H. polymorpha immobilized in CA, in order to decompose the formaldehyde formed in the first step. The proposed system provided almost total elimination of the airborne methylamine and the formaldehyde.
Subject(s)
Air Pollutants/metabolism , Amine Oxidase (Copper-Containing)/metabolism , Methylamines/metabolism , Pichia/metabolism , Amine Oxidase (Copper-Containing)/genetics , Amine Oxidase (Copper-Containing)/isolation & purification , Biodegradation, Environmental , Cloning, Molecular , Enzymes, Immobilized/metabolism , Gene Expression , Gene Order , Genetic Vectors , Pichia/genetics , Recombinant Proteins/metabolism , Saccharomyces cerevisiae/genetics , Saccharomyces cerevisiae/metabolismABSTRACT
The antibacterial effects of a new organo-tellurium compound [Octa-O-bis-(R,R)-tartarate ditellurane (OTD)] on Escherichia coli isolates as a model are shown. OTD was found to be a bactericidal drug. It exhibits inhibition zones on a protein-rich agar medium but not in a protein-poor medium unless a thiol is added. When applied at the lag phase, OTD inhibits more efficiently than at the log phase. Thiols enhance the efficiency at the log phase. OTD inhibits biofilm formation of E. coli. X-ray microanalysis demonstrated damage caused to the Naâº/K⺠pumps and leakage of potassium and phosphorous. Scanning electron microscopy demonstrated an incomplete surface of the bacterial cell wall with a concavity in the center that looks like a hole. Transmission electron microscopy demonstrated severe damage, such as depletion, perforation, and holes in the inner membrane. These results indicate for the first time that the new tellurium compound has antibacterial activities.
Subject(s)
Anti-Bacterial Agents/pharmacology , Escherichia coli/drug effects , Organometallic Compounds/pharmacology , Tartrates/pharmacology , Biofilms/drug effects , Cell Wall/drug effects , Escherichia coli/growth & development , Microbial Sensitivity Tests , Microscopy, Electron, Scanning , Microscopy, Electron, TransmissionABSTRACT
A laboratory prototype of a microcomputer-based analyzer was developed for quantitative determination of formaldehyde in liquid samples, based on catalytic chemosensing elements. It was shown that selectivity for the target analyte could be increased by modulating the working electrode potential. Analytical parameters of three variants of the amperometric analyzer that differed in the chemical structure/configuration of the working electrode were studied. The constructed analyzer was tested on wastewater solutions that contained formaldehyde. A simple low-cost biosensor was developed for semi-quantitative detection of airborne formaldehyde in concentrations exceeding the threshold level. This biosensor is based on a change in the color of a solution that contains a mixture of alcohol oxidase from the yeast Hansenula polymorpha, horseradish peroxidase and a chromogen, following exposure to airborne formaldehyde. The solution is enclosed within a membrane device, which is permeable to formaldehyde vapors. The most efficient and sensitive biosensor for detecting formaldehyde was the one that contained alcohol oxidase with an activity of 1.2 U·mL-1. The biosensor requires no special instrumentation and enables rapid visual detection of airborne formaldehyde at concentrations, which are hazardous to human health.
ABSTRACT
Zinc-doped copper oxide nanoparticles are synthesized and simultaneously deposited on cotton fabric using ultrasound irradiation. The optimization of the processing conditions, the specific reagent ratio, and the precursor concentration results in the formation of uniform nanoparticles with an average size of ≈30 nm. The antibacterial activity of the Zn-doped CuO Cu0.88Zn0.12O in a colloidal suspension or deposited on the fabric is tested against Escherichia coli (Gram negative) and Staphylococcus aureus (Gram positive) bacteria. A substantial enhancement of 10,000 times in the antimicrobial activity of the Zn-CuO nanocomposite compared to the pure CuO and ZnO nanoparticles (NPs) is observed after 10 min exposure to the bacteria. Similar activities are observed against multidrug-resistant bacteria (MDR), (i.e., Methicillin-resistant S. aureus and MDR E. coli) further emphasizing the efficacy of this composite. Finally, the mechanism for this enhanced antibacterial activity is presented.
Subject(s)
Anti-Bacterial Agents/pharmacology , Copper/chemistry , Nanocomposites/chemistry , Zinc Oxide/chemistry , Anti-Bacterial Agents/chemistry , Drug Resistance, Multiple, Bacterial , Escherichia coli/drug effects , Microbial Sensitivity Tests , Staphylococcus aureus/drug effectsABSTRACT
Antibiotic resistance of pathogenic bacteria is a major concern and presents a special challenge for development of alternative antibacterial modalities. One of these alternative approaches is based on using the photodynamic therapy (PDT) for eradicating bacteria. Photosensitizer-induced PDT exhibits unique properties and demonstrates efficient microbe-killing effects. The efficient and irreversible antimicrobial effects of PDT are not dependent on the antibiotic susceptibility of the pathogenic bacteria to antibiotics. Gram-positive bacteria exhibit efficient binding of the photosensitizer to the bacterial barriers, leading to immediate photoinactivation of the bacteria. Photoinactivation of Gram-positive bacteria by various photosensitizers has become a high priority, since these bacteria are responsible for life-threatening infections in humans, especially in the elderly and in compromised hosts in whom they cause hospital-acquired infections. The present review concentrates on the photoinactivation of Staphylococi, Streptococci, Propionibacterium acnes, Deinococcus radiodurans, aerobic spore-forming Bacilli by various photosensitizers and by various methods described in numerous works and patents.
Subject(s)
Gram-Positive Bacteria/drug effects , Photosensitizing Agents/pharmacology , Biofilms/drug effects , Deinococcus/drug effects , Humans , Patents as Topic , Photochemotherapy/methods , Photosensitizing Agents/chemistry , Propionibacterium acnes/drug effects , Solubility , Staphylococcus/drug effects , Staphylococcus/physiology , Streptococcus/drug effects , WaterABSTRACT
Photodynamic antimicrobial chemotherapy based on photosensitizers activated by illumination is limited by poor penetration of visible light through skin and tissues. In order to overcome this problem, Rose Bengal was excited in the dark by 28 kHz ultrasound and was applied for inactivation of bacteria. It is demonstrated, for the first time, that the sonodynamic technique is effective for eradication of gram-positive Staphylococcus aureus and gram-negative Escherichia coli. The net sonodynamic effect was calculated as a 3-4 log10 reduction in bacteria concentration, depending on the cell and the Rose Bengal concentration and the treatment time. Sonodynamic treatment may become a novel and effective form of antimicrobial therapy and can be used for low-temperature sterilization of medical instruments and surgical accessories.
Subject(s)
Gram-Negative Bacteria/drug effects , Gram-Positive Bacteria/drug effects , Photosensitizing Agents/pharmacology , Rose Bengal/pharmacology , Sterilization/methods , Anti-Infective Agents/pharmacology , Cold Temperature , Escherichia coli/drug effects , Fluorescent Dyes/pharmacology , Light , Staphylococcus aureus/drug effects , Stem CellsABSTRACT
A microbial fuel cell (MFC) was operated with a pure culture of Cupriavidus basilensis bacterial cells growing in the anode compartment in a defined medium containing acetate or phenol. Operating this mediator-less MFC under a constant external resistor of 1 kΩ with acetate or phenol led to current generation of 902 and 310 mA m(-2) respectively. In the MFC which was operated using acetate or phenol, the current density measured from the plankton bacterial cells with a fresh electrode was 125 and 109 mA m(-2), respectively, whereas the current obtained with biofilm-covered electrodes in sterile medium was 541 and 228 mA m(-2) respectively. After 72 h in the MFC, 86% of the initial phenol concentration was removed, while only 64% was removed after the same time in the control MFC which was held at an open circuit potential (OCP). Furthermore, SEM and confocal microscopy analyses demonstrated a developed biofilm with a live C. basilensis population. In conclusion, in this study we demonstrated, for the first time, use of C. basilensis facultative aerobe bacterial cells in a MFC using acetate or phenol as the sole carbon source which led to electricity generation.
Subject(s)
Acetates/metabolism , Bioelectric Energy Sources , Carbon/metabolism , Cupriavidus/growth & development , Cupriavidus/metabolism , Electricity , Phenol/metabolism , Aerobiosis , Biofilms/growth & development , Culture Media/chemistry , Cupriavidus/physiology , Electrodes/microbiologyABSTRACT
Cyt1Aa is the major and most active component of the parasporal crystal of the Gram-positive soil entomopathogenic bacterium Bacillus thuringiensis subsp. israelensis. The Cyt1Aa protoxin exhibits some hemolytic and cytolytic activity. However, highly active 22-25 kDa toxins are obtained after proteolysis of Cyt1Aa from both the N- and the C-termini. As shown in this study, preliminary binding of the protoxin to polylamellary liposomes or partial denaturation of Cyt1Aa and further processing by several exogenous proteases yielded short 4.9-11.5 kDa cytolytic peptide fragments of Cyt1Aa. The shortest 51 amino acid peptide was obtained after pre-incubation of Cyt1Aa with SDS and proteolysis with proteinase K. This peptide was purified, identified as the Ile87-Asp137 fragment of Cyt1Aa and was shown to exhibit more than 30 % hemolysis of rabbit erythrocytes.
Subject(s)
Bacillus thuringiensis/metabolism , Bacterial Proteins/metabolism , Endotoxins/metabolism , Hemolysin Proteins/metabolism , Peptide Fragments/metabolism , Amino Acid Sequence , Animals , Bacillus thuringiensis Toxins , Bacterial Proteins/chemistry , Electrophoresis, Polyacrylamide Gel , Endopeptidase K/metabolism , Endotoxins/chemistry , Hemolysin Proteins/chemistry , Hemolysis/drug effects , Liposomes/metabolism , Molecular Sequence Data , Peptide Fragments/isolation & purification , Peptide Fragments/pharmacology , Protein Binding , Proteolysis , RabbitsABSTRACT
Immobilization of photosensitizers in polymers opens prospects for their continuous and reusable application. Methylene blue (MB) and Rose Bengal were immobilized in polystyrene by mixing solutions of the photosensitizers in chloroform with a polymer solution, followed by air evaporation of the solvent. This procedure yielded 15-140 µm polymer films with a porous surface structure. The method chosen for immobilization ensured 99% enclosure of the photosensitizer in the polymer. The antimicrobial activity of the immobilized photosensitizers was tested against Gram-positive and Gram-negative bacteria. It was found that both immobilized photosensitizers exhibited high antimicrobial properties, and caused by a 1.5-3 log10 reduction in the bacterial concentrations to their total eradication. The bactericidal effect of the immobilized photosensitizers depended on the cell concentration and on the illumination conditions. Scanning electron microscopy was used to prove that immobilized photosensitizers excited by white light caused irreversible damage to microbial cells. Photosensitizers immobilized on a solid phase can be applied for continuous disinfection of wastewater bacteria.
Subject(s)
Anti-Bacterial Agents/pharmacology , Escherichia coli/drug effects , Methylene Blue/pharmacology , Photosensitizing Agents/pharmacology , Polystyrenes/chemistry , Rose Bengal/pharmacology , Staphylococcus aureus/drug effects , Adsorption , Anti-Bacterial Agents/chemistry , Disinfection/methods , Dose-Response Relationship, Radiation , Escherichia coli/growth & development , Escherichia coli/radiation effects , Light , Methylene Blue/chemistry , Microbial Viability/drug effects , Microbial Viability/radiation effects , Photosensitizing Agents/chemistry , Rose Bengal/chemistry , Staphylococcus aureus/growth & development , Staphylococcus aureus/radiation effectsABSTRACT
Silver nanoparticles (NPs) were synthesized sonochemically by the reduction of silver ions with ethylene glycol and simultaneously deposited on different forms of TiO2 powders (commercial Degussa P-25, synthetic anatase and mesoporous titania). The Ag-TiO2 nanocomposites were characterized by X-ray electron diffraction (XRD), transmission electron microscopy (TEM), energy-dispersed X-ray analysis (EDX), UV absorption spectroscopy (UV), Z-potential measurements and electron paramagnetic resonance (EPR). The results demonstrated homogeneous distribution of silver nanoparticles â¼3 nm in size, strongly attached to the surface of titania. The antimicrobial properties of Ag-TiO2 were tested against a number of Gram-positive and Gram-negative bacteria. A high bactericidal effect was found in the absence of UV light. The reduction in bacterial viability was between 3 and 4.2 logs. Based on the experimental data it was concluded that enhanced antimicrobial activity of the Ag-TiO2 originated from both the oxidative stress generated by silver nanoparticles and the presence of silver ions on the surface of the silver-titania composite.
ABSTRACT
To date, there is still a lack of definite knowledge regarding the interaction of CuO nanoparticles with bacteria and the possible permeation of the nanoparticles into bacterial cells. This study was aimed at shedding light on the size-dependent (from the microscale down to the small nanoscale) antibacterial activity of CuO. The potent antibacterial activity of CuO nanoparticles was found to be due to ROS-generation by the nanoparticles attached to the bacterial cells, which in turn provoked an enhancement of the intracellular oxidative stress. This paradigm was confirmed by several assays such as lipid peroxidation and reporter strains of oxidative stress. Furthermore, electron microscopy indicated that the small nanoparticles of CuO penetrated the cells. Collectively, the results reported herein may reconcile conflicting concepts in the literature concerning the antibacterial mechanism of CuO nanoparticles, as well as highlight the potential for developing sustainable CuO nanoparticles-based devices for inhibiting bacterial infections.