Gram-positive Bacteria Bacillus Subtilis Research Articles

Profiling of Silk Sericin from Cocoons of Three Southern African Wild Silk Moths with a Focus on Their Antimicrobial and Antioxidant Properties.

Silk sericin was extracted from the cocoons of three Southern African wild silk moth species, namely Gonometapostica, G. rufobrunnae (Lepidoptera: Lasiocampidae), and Argema mimosae (Lepidoptera: Saturniidae); these three sericin extracts were analysed to determine the relationship that exists between their chemical structures and their functional properties. The relationship was investigated by utilising several methods that include the determination of the amino acid composition, and characterisation of the secondary structures with Fourier transformation infrared spectroscopy (FTIR) and X-ray diffraction (XRD). The antibacterial properties of these three sericin extracts were evaluated by an agar well diffusion assay with three Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, and Staphylococcus epidermidis) as test microorganisms; and, lastly, the antioxidant properties of the three sericin extracts were determined using several scavenging methods that include the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH), 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS˙+), and the ferric reducing antioxidant power (FRAP) assay. The amino acid composition in the silk sericin extracts from G. postica, G. rufobrunnea, and Argema mimosa in terms of the polar/non-polar ratio (P/NP) was found to be 65:35, 56:44, and 59:41, respectively. The FTIR spectra of these three silk sericin extracts showed distinct major bands such as amide A (3265 cm−1), amide B (3062 cm−1), amide I (1644 cm−1), amide II (1538 cm−1), and amide III (1244 cm−1). The XRD patterns of the silk sericin extracts revealed both amorphous and α-helical structures, with small crystalline regions. All three silk sericin extracts presented potent antibacterial efficacy against the three Gram-positive bacteria and were found to have excellent antioxidant activities against the tested free radicals.

Novel Biodegradable Starch Film for Food Packaging with Antimicrobial Chicory Root Extract and Phytic Acid as a Cross-Linking Agent.

The aim of the study was to obtain and evaluate the properties of biodegradable starch film with the addition of phytic acid (0.05%) as a cross-linking agent and chicory root extract (1–5%) as an antimicrobial agent. To prepare biodegradable film, extracts from chicory root obtained with water or methanol were used. The content of bioactive compounds (sesquiterpene lactones and total polyphenols) was evaluated in chicory extracts. The antibacterial activity of the extracts was tested against Gram-negative bacteria (Pseudomonas fluorescens, Escherichia coli) and Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) using the microculture method. The extracts acted as bacteriostatic agents, decreasing the growth rate (µmax), and extending the lag phase (tlag). The most sensitive bacterium in terms of film bacteriostatic activity was P. fluorescens; all extracts, irrespective of the solvent used, decreased its µmax value. S. aureus was the least sensitive. The obtained films were tested for their properties as food packaging (color, thickness, permeability, mechanical strength). Phytic acid improved the tensile strength and barrier properties of the films. The antimicrobial activity of the films was studied by the disk diffusion method against Gram-negative (P. fluorescens, E. coli) and Gram-positive (B. subtilis, S. aureus) bacteria, as well as fungi (Candida albicans, Aspergillus niger). The growth-inhibiting activity of each obtained film was observed for all tested microorganisms, and the most beneficial effect was observed for films with the 5% level of added extracts obtained with water. The growth-inhibiting activity for fungi, in particular for the yeast C. albicans, was low.

Facile synthesis of new composite, Ag-Nps-loaded core/shell CdO/Co3O4 NPs, characterization and excellent performance in antibacterial activity

Here, we report for the first time the synthesis of new composite Ag-NPs-loaded core/shell mixed oxides NPs, CdO/Co3O4. First, nano-precursors (1) and (2) consist of mixed (cadmium oxalate/cobalt oxalate) and (silver oxalate/cadmium oxalate/cobalt oxalate), respectively, have been synthesized and characterized. Then, thermal treatment of 1 and 2 at 400 °C resulted in the formation of composites CdO/Co3O4 (3) and Ag-NPs@CdO/Co3O4 (4), respectively. The materials have been characterized by IR, SEM, TEM, TGA and XRD. The morphologies of the materials were described from SEM images. TEM images revealing the formation of core–shell structure with average particles size 5–20 nm. The crystal sizes were calculated from XRD patterns and resulted in 14.21, 14.65, 15.06 and 15.79 nm for 1, 2, 3 and 4, respectively. All the materials undergo tests as antibacterial agents against Gram-positive bacteria (Bacillus subtilis and Enterococcus spp.) and Gram-negative bacteria (E. coli and Pseudomonas aeruginosa). Precursor 2 and composite 4 impart higher inhibition against all the bacterial strains compared to precursor 1 and composite 3.

Antioxidant and antibacterial properties of lemon, sweet, and cereal grasses

Total phenolic content (TPC), antioxidant and antibacterial activity of ethanol, water, and water:ethanol (50/50 vol/vol) extracts from wheat, spelt, rye, barley, sweet, and lemon grasses were studied. Both grass type and solvent used significantly (p < .05; MANOVA) affected the extracts’ properties. The water:ethanol extract from lemon grass showed the highest TPC (107.24 ± 2.22 mg GAE/g d.m.), DPPH radical scavenging activity (87.8% inhibition), and FRAP value (1,445.2 ± 14.1 µmol Trolox/g d.m.). Rye and barley grass extracts also exhibited strong antioxidant potential. Spelt and lemon grass demonstrated the highest antimicrobial activity among the ethanol and water:ethanol extracts, whereas among the water extracts, only rye grass showed antibacterial activity against all of the tested indicator microorganisms. Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) were inhibited by extracts at a concentration of 0.3 mg/ml, whereas gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) needed higher extract concentrations (5–20 mg/ml). Grass extracts are thus a potential source of biologically functional compounds. Practical applications There is an ongoing, extensive search for natural ingredients that either prevent or retard undesirable changes, such as oxidation or microbiological contamination, which take place in food products. In this study, extracts from different types of grasses exhibited strong and moderate antioxidant and antibacterial activities, which thus makes it possible to use them as additives (antioxidants or preservatives) in the design of novel beverages and food products. The results obtained in this study could be an important asset to the food industry, as they provide new insight into plant extracts that have the potential to be used in food supplements, health drinks, or food products with enhanced health properties.

Evaluation of Antibacterial Activity Expression of the Hinokitiol/Cyclodextrin Complex Against Bacteria.

The purpose of this study was to assess the antimicrobial activity of a solid dispersion prepared by mixing and grinding hinokitiol (HT) with α-cyclodextrin (αCD), β-cyclodextrin (βCD), or γ-cyclodextrin (γCD). Antimicrobial activity was evaluated by calculating the minimum inhibitory concentration (MIC) and evaluating the change in the number of bacteria over time. The test microbes used were two Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus), two Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa), and two fungi (Candida albicans and Aspergillus brasiliensis). Calculation of the MIC value of HT using the agar dilution method revealed that the MIC of HT/CD inclusion complexes was lower than that of HT alone. HT irreversibly inhibited the growth of microorganisms in a short amount of time. HT/CD complexes retained the antimicrobial activity of HT as a result of including HT in a CD complex. These results suggest that inclusion of HT, an antimicrobial component, using CDs could lead to appropriate control of the drug release rate and efficient display of antimicrobial activity.

Facile Synthesis of SiO₂/CMC/Ag Hybrids Derived from Waste Biomass (Sugarcane Bagasse) Having Special Medical Application.

This research is focused on the use of sol gel technique to synthesize amorphous SiO₂ hybrids derived from lab made CMC (made from sugarcane bagasse) and tetraethoxysilane (TEOS) comprising silver nanoparticles (Ag-NPs). The dominant absorption peak in the order of 425 nm confirms the presence of Ag-NPs hybrid group owing to the surface Plasmon resonance (SPR). Ag-NPs hybrid characterization of was performed by Ultra violet-visible spectra (UV-Vis), Scanning electronic microscopy (SEM), Transmission electron microscopy (TEM), Particle size analyser (PSA), Energy Dispersive X-ray spectroscopy (EDX), X-ray diffractometer (XRD) and Fourier transform infrared spectroscopy (FTIR). The antibacterial action of Ag-NPs in contrast to Gram-negative bacteria (Escherichia coli) (ATCC 433) and Gram-positive bacteria (Bacillus subtilis) (ATCC 1688) was analyzed by using the method of agar disk diffusion technique. Ag-NPs hybrids extracted from lab-made CMC confirm higher adverse bacterial action through Gram-positive bacteria as well as Gram-negative bacteria related to synthetic CMC acquired from the market.

Isolation and identification of antibacterial compound from common name Holothuria leucospilota in the Persian Gulf

Echinodermata are one of the most important branches of invertebrate in marine ecosystems, which today are also known as a rich source of natural products with biological properties. Most of these properties belong to compounds with a terpenoid structure. According to the biological properties of sea cucumbers in the Persian Gulf, this scientific study investigates the antibacterial properties of lanosterol compounds extracted from Holothuria leucospilota of Hengam Island in Persian Gulf. The cucumber powder was extracted using acetone, then the extract purified by silica gel column chromatography with n-hexane and ethyl acetate combination to isolate the terpenoid compounds. Isolated compound were run through TLC and sprayed with vanillin-sulphuric acid reagent for detection of terpenoid compound and profile of isolated compound obtained by gas chromatography (GC). The lanosterol triterpenoid compound in column fraction was identified by GC. Antimicrobial properties were evaluated by dilution test on bacterial strain Escherichia coli, Pseudomonas aeruginosa, Klebsiella nemonya, Proteus vulgaris, Salmonella typhi, Staphylococcus aureus, Bacillus subtilis, Bacillus cereus and Nocardia brazilinus. This compound has antibacterial effects on gram-positive bacteria (Bacillus subtilis, Bacillus cereus and Staphylococcus aureus). Antibacterial effects of the lanosterol indicate that it can be very effective in antibiotics production.

Polyphenols profile of pomegranate leaves and their role in green synthesis of silver nanoparticles

The current study reports on polyphenols profile of pomegranate leaves (PL) Punica granatum grown in Egypt and exhibiting their role in development of an eco-friendly method of green synthesis of silver nanoparticles (AgNPs). PL aqueous alcohol extract was fractionated, the major phenolic compound was isolated from the polyphenols rich fraction (ethyl acetate fraction) and identified by conventional and spectroscopic methods of analysis as ellagic acid. Furthermore, the fraction was standardized and analysed using UPLC-PDA-UV and LC–MS-MS techniques revealing tentative identification of 23 polyphenolic compounds, quantifying ellagic acid as 43.14 ± 0.57 μg/mg of the fraction. AgNPs were successfully synthesized with the aid of polyphenols rich fraction. This is the first report revealing the systematic optimization of the green synthesis process using various independent variables. AgNPs were characterized by adopting UV–Vis spectroscopy, FTIR, XRD, and SEM, which revealed strong SPR band within average of λ max 425 nm and polygonal shaped nanoparticles of 26.22 nm size, respectively. The antimicrobial efficacies of AgNPs and polyphenols rich fraction were tested against Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, and Sarcina lutea), Gram-negative bacteria (Salmonella paratyphi, Escherichia coli, and Pseudomonas aeruginosa) and fungi (Candida albicans). AgNPs showed a concentration-dependent activity against all the tested microorganisms.

Chemical Composition and Antimicrobial Activity of Essential Oil Extracted from Eucalyptus citriodora Leaf

Eucalyptus oil is a rich source of bioactive compounds with a variety of biological activities and is widely used in traditional medicine. Eucalyptus citriodora is cultivated for the production of essential oils. However, the mode of antibacterial action of essential oils from E. citriodora is not well-known. This study aimed to determine the chemical components, microbial inhibitory effect, and mechanism of action of the essential oil from E. citriodora. The oil was extracted from E. citriodora leaves by hydro-distillation and the chemical components were analyzed using gas chromatography-mass spectrometry. The antibacterial activities of eucalyptus oil against gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus, and Staphylococcus intermedius) and gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) were screened by disc diffusion method and quantitative analysis was conducted by the microdilution method. The mechanism of action of the extracted essential oil was observed using SEM and analyzed by SDS-PAGE. The major components of E. citriodora oil were citronellal (60.55 ± 0.07%), followed by dl-isopulegol (10.57 ± 0.02%) and citronellol (9.04 ± 0.03%). The antibacterial screening indicated that E. citriodora oil exhibited prominent activity against all tested strains. The minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) against B. subtilis were 0.5% and 1.0%, respectively. The MIC and MBC concentrations against S. aureus, S. intermedius, E. coli, and P. aeruginosa were 1% and 2%, respectively. As observed by SEM, the antibacterial mechanism of E. citriodora oil involved cell wall damage; SDS-PAGE revealed decrease in protein bands compared to untreated bacteria. Thus, E. citriodora oil showed significant antimicrobial properties and caused cellular damage.

An antibacterial study of a new magnetic carbon nanotube/core-shell nanohybrids

Abstract A new magnetic carbon nanotube/core-shell nanohybrid synthesized using Co0.7Zn0.3Fe2O4 as a magnetic core, polyethylene terephthalate (PET) as a binder shell, Silver nanoparticles as antibacterial agents grafted to the shell and carbon nanotube (CNT) as a multifunctional substrate. The synthesized Co0.7Zn0.3Fe2O4/PET/Ag/CNT was characterized using field emission – scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD) spectroscopy, energy-dispersive X-ray spectroscopy (EDS), Furrier –transform infrared (FT-IR) spectroscopy and Brunauer-Emmett-Teller (BET). FESEM and TEM results confirmed the formation of spherical-like core – shell structures and their distribution on the CNTs. The spinel structure of magnetic ferrite core was demonstrated by XRD analysis. A specific surface area of 58.74 m2/g was recorded by BET measurement. A vibrating sample magnetometer (VSM) was used to determine the magnetic properties of the samples. The saturation magnetization of the nanohybrid was 44.5 emu/g showing its ferro-magnetic behavior. Antibacterial activity of the synthesized nanohybrid against two Gram-negative bacteria (Escherichia coli, Pseudomonas aeruginosa) and two Gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus) was assessed by disk diffusion standard and minimal inhibitory concentration method. The zones of inhibition were 14.3 ± 0.6, 15.1 ± 0.6, 18.1 ± 0.6 and 18.2 ± 0.6 mm zone of inhibition (ZOI) for Bacillus subtilis, Staphylococcus aureus, Escherichia coli and Pseudomonas aeruginosa, respectively. Also, Zeta potential analysis indicated the good stability of the nanohybrid (100 mV). These finding show that the Co0.7Zn0.3Fe2O4/PET/Ag/CNT nanohybrid is a promising water-dispersible antibacterial material that can easily be removed by applying a suitable magnetic field.

Impact of high salinity and the compatible solute glycine betaine on gene expression of Bacillus subtilis

The Gram-positive bacterium Bacillus subtilis is frequently exposed to hyperosmotic conditions. In addition to the induction of genes involved in the accumulation of compatible solutes, high salinity exerts widespread effects on B. subtilis physiology, including changes in cell wall metabolism, induction of an iron limitation response, reduced motility and suppression of sporulation. We performed a combined whole-transcriptome and proteome analysis of B. subtilis 168 cells continuously cultivated at low or high (1.2 M NaCl) salinity. Our study revealed significant changes in the expression of more than one-fourth of the protein-coding genes and of numerous non-coding RNAs. New aspects in understanding the impact of high salinity on B. subtilis include a sustained low-level induction of the SigB-dependent general stress response and strong repression of biofilm formation under high-salinity conditions. The accumulation of compatible solutes such as glycine betaine aids the cells to cope with water stress by maintaining physiologically adequate levels of turgor and also affects multiple cellular processes through interactions with cellular components. Therefore, we additionally analysed the global effects of glycine betaine on the transcriptome and proteome of B. subtilis and revealed that it influences gene expression not only under high-salinity, but also under standard growth conditions.

Development of Copper Loaded Nanoparticles Hydrogel Made from Waste Biomass (Sugarcane Bagasse) for Special Medical Application

This research is based on the creation of copper oxide nanoparticles (CuO-NPs) hydrogel through in situ method. The effective UV-Vis spectroscopy absorption peak of 610 nm indicates the existence of copper oxide nanoparticles (CuO-NP) group because of surface Plasmon resonance (SPR). Characterization of CuO-NPs was carried out by SEM, TEM, EDX, and XRD. However, the action of prepared nanocomposite hydrogels swelling was examined at different pH and saline solutions. In addition, CuO-NPs were also tested using the disk plate diffusion method by means of adverse effect of bacteria Gram-positive bacteria (Bacillus subtilis) as well as Gram-negative bacteria (Escherichia coli). The CuO-NPs hydrogels isolated from lab-made CMC (made from sugarcane bagasse) indicates that the Bacillus subtilis as well as Escherichia coli have greater antibacterial activity compared with synthetic CMC purchase from the market. CuO-NPs can be used effectively in biomedical applications with the production of hydrogels.

Antimicrobial and wound healing activities of certain Sudanese medicinal plants.

The emergence of drug-resistant organisms have been increasing globally; therefore, it is a burning need to find an alternative drug to get rid of the diseases caused by resistant strains. This study aims to evaluate the antimicrobial and wound healing activities of Loranthus acacia, Cassia obtusifolia and Cymbopogon proximus plants. All the plants were collected and extracted — by maceration method. Antimicrobial activities determined using standard ATCC strain for Gram-positive bacteria (Bacillus subtilis, Bacillus crew, Methicillin-resistant Staphylococcus aureus, Staphylococcus aureus) and Gram-negative bacteria (Shigella sonnnei, Salmonella Typhimurium, Salmonella typhi, Klebsiella pnuemoniae, Escherichia coli and Pseudomonas aeruginosa) following agar well diffusion method. Plants extracts were prepared as gel and investigated for in vivo wound healing activities in rats. Histological studies were performed on animals’ skin. The results showed that all tested plants have various antimicrobial and wound healing activities. Out of these plants, L. acacia exhibited the best result; it revealed a significant result for antimicrobial activities counter to all Gram-positive, Gram-negative bacteria and wound healing activities in comparing with the reference drug. Thus, it is essential to consider L. acacia as a prospective source in progress in the synthesis of a new antimicrobial drug for the treatment of infectious diseases.

Ilex khasiana - The silent holly species of Aquifoliaceae on its pharmacognostical importance as a free radical scavenger and antibacterial agent

Ilex khasiana is a rare and endangered medicinal plant endemic to northeast India. Remaining largely unexplored,it is purported to have a range of medicinal values and may soon join the medicinal plant hall of fame.Extracts of the leaves were prepared using solvents of increasing polarity, namelypetroleum ether (IKP), chloroform (IKC) and methanol (IKM).The preliminary phytochemical screening indicated the presence of alkaloids, phytosterols, triterpenoids, saponins, reducing sugars, glycosides and carbohydrates. Free radical-scavenging activity was assessed using2,2-diphenyl-1-picrylhydrazyl(DPPH). IKC exhibited the highest activity with an IC50 of 17.22 ± 1.87, followed by IKM with an IC50 of 26.93 ± 5.14 and IKP with an IC50 of 37.16 ± 5.11. Butylated hydroxytoluene (BHT)was used as the standard DPPH scavenger and showed an IC50 of 8.31 ±0.72. IKM and IKC also showed positive antibacterial activity againstGram-negative bacteria such asEscherichia coli, Pseudomonas aeruginosa, andKlebsiella pneumoniae, and a Gram-positive bacteriaBacillus subtilis. IKP did not indicate any inhibition against the selected bacteria. Our findings substantiate the basis for further investigations on the medicinal potentials of the plant.&#x0D;

Extracellular synthesis of silver nanoparticles by Thiosphaera pantotropha and evaluation of their antibacterial and cytotoxic effects.

Extracellular biosynthesis of silver nanoparticles (AgNPs) was explored using Thiosphaera pantotropha since this strain exhibits both nitrate- and nitrite-reductase enzyme activity (NaR and NiR, respectively). Optimal AgNP synthesis was achieved using 2mM AgNO3, culture supernatant of nutrient broth grown T. pantotropha, and incubation at 37°C and 180rpm. Under these conditions, the localized surface plasmon resonance peak of silver at 404nm matched well with the average size of the spherical AgNPs based on FEG-TEM micrographs, i.e., 14.6nm (range: 5-51nm). The zeta potential of -33.6mV indicated good stability of the biosynthesized nanoparticles. The XRD spectra demonstrated the simultaneous presence of face-centered cubic crystal structure of AgNPs and AgCl NPs. Ag+ ions were possibly reduced by the NaR and NiR enzymes released into the culture media. The FTIR spectra confirmed the stabilization of the AgNPs by biomolecules present in the culture supernatant of T. pantotropha. The synthesizedAg/AgCl NPs exhibited good antibacterial efficacy against both Gram-negative (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis and Staphylococcus aureus). The minimum inhibitory concentration (MIC) was 2.5µg/ml for all the bacteria except B. subtilis (MIC of 10µg/ml). The minimum bactericidal concentration (MBC) was 2.5, 10, 20, and 5µg/ml for E. coli, P. aeruginosa, B. subtilis, and S. aureus, respectively. At MBC and higher AgNP concentration, both plating and CLSM imaging confirmed the absence of viable bacteria in treated water. The biogenic AgNPs depicted IC50 of 34.8µg/ml for MCF-7 cells.

EVALUATION OF ANTIOXIDANT AND ANTIMICROBIAL PROPERTIES OF Opuntia ficus-indica, SEEDS AND PEELS EXTRACTS

The biologically active compounds isolated from plants are known to be efficient as antibacterial and antioxidants. The antioxidant and antibacterial activities of total phenols and flavonoids drived from the petroleum ether, ethyl acetate and ethanol extracts of Opuntia ficus-indicaseeds and peels were performed using DPPH and modified Kirby-Bauer disc diffusion technique against gram-positive bacteria (Bacillus subtilis) and gram-negative bacteria (Serratia marcescens), respectively. In the present study, it is demonstrated that, both alcohol and ethyl acetate extracts show the best antioxidant and antibacterial activities than the petroleum ether extracts. This is consistent with the results of the chemical analyses of both extracts.

Synthesis, crystal structures, catalytic application and antibacterial activities of Cu(II) and Zn(II) complexes bearing salicylaldehyde-imine ligands

Three novel copper(II) and zinc(II) complexes based on salicylaldehyde-imine ligands, namely [Cu(HL1)(CH3CH2OH)]·(CH3COO) (1), [Zn3(HL1)2(CH3COO)4] (2), and [Zn2(L2)]·(CH3COO) (3) [H2L1 = N,N′-bis(salicylidene)diethylenetriamine and H3L2 = 2,2′-(1E,1′E)-(2,2′-(2-(2-hydroxyphenyl)imidazolidine-1,3-diyl)bis(ethane-2,1-diyl))bis(azan-1-yl-1-ylidene)bis(methan-1-yl-1-ylidene)diphenol] have been synthesized. The complexes were characterized by IR, melting point, and elemental analyses, and the crystal structures were further determined by single crystal X-ray diffraction. These three complexes demonstrated excellent catalytic activities in the decomposition reaction of H2O2, and the decomposition percent of the H2O2 ranged from 89% to 98% under the optimized reaction conditions. Additionally, the compounds were screened as antibacterial agents against three gram-negative bacteria (Escherichia coli, Klebsiella pneumoniae and Pseudomonas aeruginosa) and three gram-positive bacteria (Bacillus subtilis, Staphylococcus aureus and Corynebacterium xerosis). The results showed that complex 2 possessed stronger antibacterial activities than the two ligands and other two complexes.

Synthesis, Characterization and Antibacterial Activity of Schiff Base, 4-Chloro-2-{(E)-[(4-Fluorophenyl)imino]methyl}phenol Metal (II) Complexes

A new series of Mn (II), Co (II), Ni (II), Cu (II), and Zn (II) complexes of the Schiff base ligand, 4-chloro-2-{(E)-[(4-fluorophenyl)imino]methyl}phenol (C13H9ClFNO), was synthesized in a methanolic medium. The Schiff base was derived from the condensation reaction of 5-chlorosalicylaldehyde and 4-fluoroaniline at room temperature. Elemental analysis, FT-IR, UV-Vis, and NMR spectral data, molar conductance measurements, and melting points were used to characterize the Schiff base and the metal complexes. From the elemental analysis data, the metal complexes formed had the general formulae [M(L)2(H2O)2], where L = Schiff base ligand (C13H9ClFNO) and M = Mn, Co, Ni, Cu, and Zn. On the basis of FT-IR, electronic spectra, and NMR data, “O” and “N” donor atoms of the Schiff base ligand participated in coordination with the metal (II) ions, and thus, a six coordinated octahedral geometry for all these complexes was proposed. Molar conductance studies on the complexes indicated they were nonelectrolytic in nature. The Schiff base ligand and its metal (II) complexes were tested in vitro to evaluate their bactericidal activity against Gram-negative bacteria (Escherichia coli and Pseudomonas aeruginosa) and Gram-positive bacteria (Bacillus subtilis and Staphylococcus typhi) using the disc diffusion method. The antibacterial evaluation results revealed that the metal (II) complexes exhibited higher antibacterial activity than the free Schiff base ligand.

Disinfection performance and mechanism of the carbon fiber-based flow-through electrode system (FES) towards Gram-negative and Gram-positive bacteria

The disinfection performance of a carbon fiber-based flow-through electrode system (FES) towards Gram-negative bacteria (Escherichia coli and fecal coliform) and Gram-positive bacteria (Enterococcus faecalis and Bacillus subtilis) in normal saline was systematically investigated over a wide range of applied voltages (1–5 V) and hydraulic retention times (HRTs) (1–10 s). It was revealed that the Gram-negative bacteria were more vulnerable to FES for their thinner cell walls, and over 6.5 log removal (no live bacteria detected) was achieved at the applied voltage of 2 V and HRT of 2 s; while Gram-positive bacteria were inactivated at slightly higher voltages (3 V, 2 s) or longer HRTs (2 V, 5 s). Bacterial inactivation was attributed to the change and rupture of cell membrane mainly by anode direct oxidation without bacterial regrowth/reactivation. In addition, negligible generation of the free chlorine at low voltages (≤2 V) can avoid the formation of potential chlorinated disinfection byproducts (DBPs). Hence, FES can offer a potential alternative to conventional disinfection methods for bacterial inactivation in natural and contaminated water.

Electrochemical cell lysis of gram-positive and gram-negative bacteria: DNA extraction from environmental water samples

Cell lysis is an essential step for the nucleic acid-based surveillance of bacteriological water quality. Recently, electrochemical cell lysis (ECL), which is based on the local generation of hydroxide at a cathode surface, has been reported to be a rapid and reagent-free method for cell lysis. Herein, we describe the development of a milliliter-output ECL device and its performance characterization with respect to the DNA extraction efficiency for gram-negative bacteria (Escherichia coli and Salmonella Typhi) and gram-positive bacteria (Enterococcus durans and Bacillus subtilis). Both gram-negative and gram-positive bacteria were successfully lysed within a short but optimal duration of 1 min at a low voltage of ∼5 V. The ECL method described herein, is demonstrated to be applicable to various environmental water sample types, including pond water, treated wastewater, and untreated wastewater with DNA extraction efficiencies similar to a commercial DNA extraction kit. The ECL system outperformed homogeneous chemical lysis in terms of reaction times and DNA extraction efficiencies, due in part to the high pH generated at the cathode surface, which was predicted by simulations of the hydroxide transport in the cathodic chamber. Our work indicates that the ECL method for DNA extraction is rapid, simplified and low-cost with no need for complex instrumentation. It has demonstrable potential as a prelude to PCR analyses of waterborne bacteria in the field, especially for the gram-negative ones.