Leakage Of Cellular Components Research Articles

Unraveling Multicopper [Cu3] and [Cu6] Clusters with Rare μ3-Sulfato and Linear μ2-Oxido-Bridges as Potent Antibiofilm Agents against Multidrug-Resistant Staphylococcus aureus.

In this research article, two multicopper [Cu3] and [Cu6] clusters, [Cu3(cpdp)(μ3-SO4)(Cl)(H2O)2]·3H2O (1) and [Cu6(cpdp)2(μ2-O)(Cl)2(H2O)4]·2Cl (2) (H3cpdp = N,N'-bis[2-carboxybenzomethyl]-N,N'-bis[2-pyridylmethyl]-1,3-diaminopropan-2-ol), have been explored as potent antibacterial and antibiofilm agents. Their molecular structures have been determined by a single-crystal X-ray diffraction study, and the compositions have been established by thermal and elemental analyses, including electrospray ionization mass spectrometry. Structural analysis shows that the metallic core of 1 is composed of a trinuclear [Cu3] assembly encapsulating a μ3-SO42- group, whereas the structure of 2 represents a hexanuclear [Cu6] assembly in which two trinuclear [Cu3] motifs are exclusively bridged by a linear μ2-O2- group. The most striking feature of the structure of 2 is the occurrence of an unusual linear oxido-bridge, with the Cu3-O6-Cu3' bridging angle being 180.00°. Whereas 1 can be viewed as an example of a copper(II)-based compound displaying a rare μ3:η1:η1:η1 bridging mode of the SO42- group, 2 is the first example of any copper(II)-based compound showing an unsupported linear Cu-O-Cu oxido-bridge. Employing variable-temperature SQUID magnetometry, the magnetic susceptibility data were measured and analyzed exemplarily for 1 in the temperature range of 2-300 K, revealing the occurrence of antiferromagnetic interactions among the paramagnetic copper centers. Both 1 and 2 exhibited potent antibacterial and antibiofilm activities against methicillin-resistant Staphylococcus aureus (MRSA BAA1717) and the clinically isolated culture of methicillin-resistant S. aureus (MRSA CI1). The mechanism of antibacterial and antibiofilm activities of these multicopper clusters was investigated by analyzing and determining the intracellular reactive oxygen species (ROS) generation, lipid peroxidation, microscopic observation of cell membrane disruption, membrane potential, and leakage of cellular components. Additionally, 1 and 2 showed a synergistic effect with commercially available antibiotics such as vancomycin with enhanced antibacterial activity. However, 1 possesses higher antibacterial, antibiofilm, and antivirulence actions, making it a potent therapeutic agent against both MRSA BAA1717 and MRSA CI1 strains.

Combined transcriptomics and metabolomics analysis reveals the antifungal activity and mechanism of Enterococcus faecium cell-free supernatant against Alternaria alternata

Certain lactic acid bacteria have been utilized as bacteriostatic agents in the context of fruit and vegetable spoilage fungi. Although Enterococcus faecium is a member of the lactic acid bacteria group, its application in the prevention of post-harvest fruit spoilage remains largely unexplored. We investigated the activity of E. faecium cell-free supernatant (CFS) against fruit and vegetable spoilage fungi and probed the possible fungistatic mechanisms involved. The in vitro results showed that CFS possessed significant antifungal activity against Alternaria alternata with a MIC of 20%, which resulted in distorted rupture of A. alternata cell membranes and leakage of cellular components in a dose-dependent manner. In addition, transcriptomics and metabolomics results showed that CFS could also inhibit the growth of A. alternata by altering energy metabolism, impairing intracellular antioxidant function, reducing intracellular hormone biosynthesis, and slowing down or stopping asymmetric cell division. In summary, E. faecium CFS has been shown to effectively inhibit A. alternata.

Anti bacterial function of secreted human FABP3

FABP3 belongs to a large family of cytoplasmic fatty acid binding proteins that are expressed in a tissue-specific manner. It is predominantly expressed in breast, muscle and heart. During our exploratory studies on the role of FABP3 in tumorigenesis and our consequent attempts to study the molecular mechanism responsible for the oncogenic potential of FABP3, we came across an unexpected role of FABP3 as an anti-bacterial protein. Presence of the protein was detected in culture media of cell lines stably over-expressing human FABP3. Conditioned medium from these FABP3 over-expressing cells exerted a distinct anti-bacterial activity against E. coli. Our results indicate that binding of FABP3 to the bacterial cell surface contributes to its anti-bacterial activity. Incubation of E. coli bacterial cells with FABP3 protein led to disruption of the physical integrity of bacterial cell membrane causing leakage of cellular components. Further, in silico analysis predicted strong binding of FABP3 to the antibiotic binding sites on the bacterial ribosome. Interestingly, we found that FABP3 is a naturally occurring secretory protein present in milk in abundance as confirmed by western blot and ELISA. Thus, our experimental data together with in silico analysis suggests that FABP3 is secreted in milk, has an anti-bacterial function, shows activity against E. coli by disrupting bacterial membrane and targeting the ribosome, and may play a protective role against bacterial infection in newborns.

Antifungal activity of star anise extract against Penicillium roqueforti and Aspergillus niger for bread shelf life

Because star anise is underutilized in the baking sector and the antifungal targets are unclear, this study aimed to investigate the antifungal effect and mechanism of star anise extract (SAE) on spoilage fungi in bread. SAE was prepared by ethanol extraction and 31 substances were identified by GC-MS, among which trans-anethole (62.62%), estragole (7.82%) and linalool (4.66%) were the major components. The antifungal activity of SAE and the three main components against Penicillium roqueforti and Aspergillus niger were determined by using the Oxford cup method and the sesqui-dilution method. The inhibition zones were 9.88 mm and 15.09 mm, while the minimum inhibitory concentrations were 125.00 μL/mL and 31.25 μL/mL. Trans-anethole and estragole both showed antifungal activity against Penicillium roqueforti and Aspergillus niger, while linalool only showed antifungal activity against Aspergillus niger. Propidium iodide and fluorescein diacetate staining analysis, leakage of cellular components (nucleic acids and proteins) and rise in ergosterol content indicated that SAE disrupted the integrity and permeability of the cell membrane. Malondialdehyde was increased after SAE treatment, indicating that SAE caused lipid peroxidation in the cell membrane, further confirming that it disrupted the cell membrane. At the same time, SAE interacted with membrane proteins and altered their conformation, resulting in cell membrane dysfunction. Finally, the shelf life test showed that SAE extended the shelf life of the bread by up to 6 days. In general, this study highlights the antifungal effect of SAE against Penicillium roqueforti and Aspergillus niger, which indicated that SAE can be used as an antifungal agent to extend the shelf life of bread.

Repurposing the Hedgehog pathway inhibitor, BMS-833923, as a phosphatidylglycerol-selective membrane-disruptive colistin adjuvant against ESKAPE pathogens

The rapid emergence and spread of multi-drug- or pan-drug-resistant bacterial pathogens, such as ESKAPE, pose a serious threat to global health. However, the development of novel antibiotics is hindered by difficulties in identifying new antibiotic targets and the rapid development of drug resistance. Drug repurposing is an effective alternative strategy for combating antibiotic resistance that both saves resources and extends the life of existing antibiotics in combination treatment regimens. Screening of a chemical compound library identified BMS-833923 (BMS), a smoothened antagonist that kills Gram-positive bacteria directly, and potentiates colistin to destroy various Gram-negative bacteria. BMS did not induce detectable antibiotic resistance in vitro, and showed effective activity against drug-resistant bacteria in vivo. Mechanistic studies revealed that BMS caused membrane disruption by targeting the membrane phospholipids phosphatidylglycerol and cardiolipin, promoting membrane dysfunction, metabolic disturbance, leakage of cellular components, and, ultimately, cell death. This study describes a potential strategy to enhance the efficacy of colistin and combat multi-drug-resistant ESKAPE pathogens.

Citrus Aurantifolia Essential Oil Composition, Bioactivity, and Antibacterial Mode of Action on Salmonella Enterica, a Foodborne Pathogen

Salmonella enterica is a well-known pathogenic bacterium that can cause intracellular illness and food poisoning in humans, especially salmonellosis. In the present study, 20 essential oils of aromatic plants were screened for their antibacterial activity against S. enterica. Among the essential oils screened, Citrus aurantifolia essential oil (CAEO) demonstrated most efficient activity against S. enterica. CAEO had minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of 8 and 16 μl/mL, respectively. A significant scavenging of radical cations was observed with CAEO using 2, 2'-diphenyl-1-picryl hydrazyl with an IC50 of 0.2147 mg/mL. Total phenolic content of CAEO was 10.90 mg GAE/100 μL. The treatment of bacterium with CAEO caused the leakage of cellular components, i.e., both nucleic acids and proteins. Furthermore, scanning electron microscopy (SEM) was used to measure the ultrastructure of control and treated bacterium (due to CAEO). The results of SEM reveal a loss of cellular integrity and function of bacterial cell membrane. The GC/GC-MS analysis of CAEO revealed E-citral (67.97%) as a major chemical component. CAEO may be considered as a safe antibacterial agent against foodborne S. enterica. The present study investigated a detailed analysis of antibacterial activity of C. aurantifolia essential oil, which can provide insight for further studies.

Photo-Responded Antibacterial Therapy of Reinfection in Percutaneous Implants by Nanostructured Bio-Heterojunction.

Percutaneous implants may experience infection for several times during their servicing periods. They need antibacterial activity and durability to reduce recurrent infection and cytocompatibility to reconstruct biosealing. A novel photoresponse bio-heterojunction (PCT) is developed herein. It consists of TiO2 nanotubes loaded with CuS nanoparticles and wrapped with polydopamine (PDA) layer. In PCT, a built-in electric field directing from TiO2 to CuS and then to PDA is formed, and with near-infrared (NIR) irradiation, it drives photoexcited electrons to transfer in opposite direction, resulting in the separation of electron-hole pairs and formation of reactive oxygen species (ROS). Simultaneously, PCT shows photothermal effect due to nonradiative relaxation of photoexcited electrons and thermal vibration of lattices. The synergic effect of photogenerated ROS and hyperthermia increases bacterial membrane permeability and leakage of cellular components, endowing PCT with outstanding antibacterial performance. More importantly, PCT has good antibacterial durability and cytocompatibility due to the inhibited leaching of CuS by PDA layer. In reinfected models, with NIR irradiation, PCT sterilizes bacteria, reduces inflammatory response and enhances re-integration of soft tissue efficiently. This work provides an outstanding bio-heterojunction for percutaneous implants in treating reinfection by NIR irradiation and rebuilding biosealing.

Allylamines, Benzylamines, and Fungal Cell Permeability: A Review of Mechanistic Effects and Usefulness against Fungal Pathogens.

Allylamines, naftifine and terbinafine, and the benzylamine, butenafine, are antifungal agents with activity on the fungal cell membrane. These synthetic compounds specifically inhibit squalene epoxidase, a key enzyme in fungal sterol biosynthesis. This results in a deficiency in ergosterol, a major fungal membrane sterol that regulates membrane fluidity, biogenesis, and functions, and whose damage results in increased membrane permeability and leakage of cellular components, ultimately leading to fungal cell death. With the fungal cell membrane being predominantly made up of lipids including sterols, these lipids have a vital role in the pathogenesis of fungal infections and the identification of improved therapies. This review will focus on the fungal cell membrane structure, activity of allylamines and benzylamines, and the mechanistic damage they cause to the membrane. Furthermore, pharmaceutical preparations and clinical uses of these drugs, mainly in dermatophyte infections, will be reviewed.

Genomic and Biocontrol Potential of the Crude Lipopeptide by Streptomyces bikiniensis HD-087 Against Magnaporthe oryzae

Rice blast caused by Magnaporthe oryzae is one of the most destructive plant diseases. The secondary metabolites of Streptomyces have potential as biological control agents against M. oryzae. However, no commercial secondary antimicrobial products of Streptomyces have been found by gene prediction, and, particularly relevant for this study, a biocontrol agent obtained from Streptomyces bikiniensis has yet to be found. In this research, genomic analysis was used to predict the secondary metabolites of Streptomyces, and the ability to develop biocontrol pharmaceuticals rapidly was demonstrated. The complete genome of the S. bikiniensis HD-087 strain was sequenced and revealed a number of key functional gene clusters that contribute to the biosynthesis of active secondary metabolites. The crude extract of lipopeptides (CEL) predicted by NRPS gene clusters was extracted from the fermentation liquid of S. bikiniensis HD-087 by acid precipitation followed by methanol extraction, and surfactins, iturins, and fengycins were identified by liquid chromatography-mass spectrometry (LC–MS). In vitro, the CEL of this strain inhibited spore germination and appressorial formation of M. oryzae by destroying membrane integrity and through the leakage of cellular components. In vivo, this CEL reduced the disease index of rice blast by approximately 76.9% on detached leaves, whereas its control effect on leaf blast during pot experiments was approximately 60%. Thus, the S. bikiniensis CEL appears to be a highly suitable alternative to synthetic chemical fungicides for controlling M. oryzae.

Unravelling the pore formation mechanism of the bi-partite YaxAB toxin in the presence of cholesterol

Pore-forming toxins are a class of proteins secreted by various bacterial strains that form pores on the target cell membranes, cause leakage of cellular components, and result in cell death. Upon encounter with the lipid membrane, the water-soluble monomeric form of the toxin undergoes significant conformational changes necessary to oligomerize and form pores. This study examines the process of pore formation of the two-component α-helical bacterial pore-forming toxin, YaxAB, in molecular detail using molecular dynamics (MD) simulations.

English

Ozone is active against a broad spectrum of microorganisms. Ozone treatment can enhance safety and increase shelf life with limited impact on product quality. Ozone is known to be one of the strongest oxidizers that can have applications in foods. In the gaseous state, ozone is denser than air, colorless at lower concentrations and possesses a distinct odor. Ozone can be generated using a few methods, by photochemical procedures specifically UV light, electrolysis of water, with corona discharge being the most common method. In the food processing industry, ozone acts as a powerful sterilizer against both Gram-positive and Gram-negative bacteria, bacterial spores, fungi, viruses, and protozoa. Ozone affects the unsaturated lipids in the cell membrane causing leakage of cellular components that can lead to cell death. There are numerous examples to show that ozone has been successfully applied in food processing, specifically in sanitation by disinfecting food plant equipment and contact surfaces, packaging materials, water, air in storage and refrigeration systems, and for foods such as dried and fresh fruits and vegetables. The shelf life and quality of different food products can be maintained using ozone through reduction of spoilage microorganisms. Key words: Ozone, food, inactivation, sanitation, bacteria.

Mutual influence of polyphenols and Lactobacillus spp. bacteria in food: a review

This paper presents the effect of polyphenols on microorganisms inhabiting the human gastrointestinal tract (mainly bacteria belonging to the Lactobacillus genus) and pathogenic microorganisms classified as the most common food contaminants. Plant secondary metabolites have the ability to modulate the growth of many microorganisms. Due to the metabolic changes induced by their presence in the environment, many pathogenic microorganisms are unable to grow, which in turn cause a significant reduction in their pathogenic potential. These processes include primarily the induction of ruptures in the cell membrane and disturbance of cell respiration. Often, the lack of integrity of cell membranes also leads to the disturbance of intracellular homeostasis and leakage of cellular components, such as proteins, ATP molecules or intracellular ions. Autoxidizing polyphenols also act as pro-oxidative substances. Hydrogen peroxide formed in the process of oxidation of polyphenolic compounds acts as a bactericidal substance (by induction of DNA breaks). With regard to intestinal microbiota, polyphenols are considered prebiotic substances that increase the number of commensal bacteria. They can positively influence the growth of Lactobacillus bacteria, which have the ability to metabolize undigested antioxidants in the digestive tract of humans and animals. Depending on the pH of the environment and the presence of ions, plant polyphenols in the human digestive tract can act as substances with antioxidant potential or become pro-oxidants. Thus, combining functional food with polyphenols and Lactobacillus bacteria not only protects food products against the development of undesirable and pathogenic microbiota, but also has a positive effect on human health. The paper also describes the possibility of changes in the genome of Lactobacillus bacteria (under the influence of polyphenols) and the influence of Lactobacillus spp. bacteria on the antimicrobial properties of polyphenols. The enzymatic abilities of bacteria of the genus Lactobacillus, which influence the transformation of polyphenolic compounds, were also described.

Methanolic Extract of the Herb Ononis spinosa L. Is an Antifungal Agent with no Cytotoxicity to Primary Human Cells.

Ononis spinosa L. is a plant traditionally used as folk remedy. There are numerous studies regarding chemical constituents and health beneficial properties of Ononidis Radix. The following study was designed to investigate chemical composition and antifungal potential of the methanolic extract obtained from the O. spinosa L. herb. Chemical analyses regarding phenolic compounds of O. spinosa were performed by liquid chromatography with mass spectrometry (LC-DAD-ESI/MSn). Antifungal activity, antibiofilm properties and antifungal mode of action of the extract were evaluated, as well as cytotoxicity. Chemical analyses revealed the presence of flavonoids, isoflavonoids and phenolic acids in O. spinosa, with kaempherol-O-hexoside-pentoside being the most abundant compound (5.1 mg/g extract). Methanolic extract was active against all of the tested microfungi with Penicillium aurantiogriseum being the most sensitive to the extract inhibitory effect at 0.02 mg/mL; and effectively inhibited biofilms formed by Candida strains. Minimum fungicidal concentrations of extract rose in the presence of ergosterol and leakage of cellular components was detected. The extract showed no cytotoxicity to human gingival fibroblast (HGF-1) cells. This study significantly contributes to overall knowledge about medicinal potential of O. spinosa herbal extract and enlightens previously unrevealed properties. O. spinosa aerial parts seem to be an interesting candidate for the development of antifungal preparations, non-toxic to human cells.

Inhibitory effect and possible mechanism of carvacrol against Colletotrichum fructicola

Carvacrol (CVR) is an essential oil and has been reported to exhibit significant inhibitory effects against a wide range of microorganisms. Anthracnose, which is caused by Colletotrichum fructicola is one of the most serious postharvest diseases in pitaya fruit. In this study, we investigate the inhibitory effect of CVR against C. fructicola and elucidate the possible modes of action. The results from our study showed that treatment with CVR could effectively inhibit mycelial growth, spore germination and germ tube elongation of C. fructicola in vitro, significantly reducing the onset and development of anthracnose in red pitaya fruit. Membrane permeability and leakage of cellular components in the hyphae of C. fructicola increased as the concentrations of CVR increased. The results from microscopy indicated that CVR treatment caused abnormalities of hyphal morphology, disruption of cytoplasmic membranes, and disorganization of intracellular organelles. Moreover, CVR treatments induced the generation of reactive oxygen species (ROS), which caused oxidative injury to the cell membrane vialipid peroxidation. The antifungal mechanism of CVR against C. fructicola may be attributed to induced ROS production, increased membrane permeability, abnormalities of ultrastructure, and loss of intracellular contents.

Efficacy of aroma compounds for postharvest management of mango anthracnose

Anthracnose is a severe disease of mango caused by Colletotrichum gloeosporioides Penz. The antifungal effects of the aroma compounds (trans-cinnamaldehyde, citral, and phenylacetaldehyde) were tested against the pathogen. These compounds exhibited complete inhibition of visual spore germination and the mycelial growth under in vitro conditions. Complete inhibition of mycelial growth of C. gloeosporioides was observed by trans-cinnamaldehyde (TCA) at 500 mg L−1 followed by citral (CT) at 750 mg L−1 and phenylacetaldehyde (PAA) at 2000 mg L−1. The effect of aroma compounds on the morphology and membrane lesion of C. gloeosporioides mycelia was studied through scanning electron microscopy (SEM). SEM observations revealed withered hyphae. Further experiments confirmed that aroma compounds inhibited the ergosterol synthesis and also triggered the membrane-active mechanism. Results on testing the efficacy of the aroma compounds through the fungal pectinase inhibition study confirmed that these aroma compounds have potential to damage plasma membrane integrity and cause membrane lesion of C. gloeosporioides, thereby causing the delayed anthracnose incidence in treated mango fruits as compared to control fruits. The antifungal activity of these aroma compounds could be attributed to the disruption of membrane integrity and leakage of cellular components. Results of the in vivo study showed that postharvest treatment of these compounds revealed that both disease incidence and severity efficiently managed in a dosage-dependent manner. The aroma compounds TCA, CT, and PAA might be an excellent natural and biodegradable bio-fungicides for the control of anthracnose disease in mango after harvest.

IFST Winning Articles

IFST Winning Articles

Antimicrobial activity of Arg–Ser–Ser against the food‐borne pathogen Pseudomonas aeruginosa

SummaryWe had previously reported a peptide sequence, Arg–Ser–Ser (RSS), which was identified after coincubation of an edible orchid species, Dendrobium aphyllum, with Lactobacillus amylolyticus. In this study, we investigated the potential mechanism of the antibacterial effect of RSS on the pathogen Pseudomonas aeruginosa. The minimum inhibitory concentration of RSS for P. aeruginosa was 6.3%, and the peptide was shown to induce morphological damage to bacterial cells. RSS treatment increased the cell surface zeta potential, hydrophobicity and cell membrane permeability, indicating that the positively charged RSS likely interacted with the negatively charged bacterial membrane. Moreover, leakage of potassium ions and proteins from bacterial cells was increased by RSS by 30 ppm and 13.5 μg mL−1, respectively. In conclusion, RSS treatment caused leakage of cellular components from P. aeruginosa cells, mainly through damaging the cell membrane by electrostatic action. Thus, RSS may be a potent new antimicrobial agent.

Synergistic effect of tea tree oil on fungi causing vaginal thrush in pregnant women

Background: Vulvovaginal candidiasis(VVC), or Vaginal thrush, is a vaginitis caused by the overgrowth of some opportunistic yeasts of the genus Candida spp. Australian Tea Tree Oil (TTO) is one of the most important essential oils that contain many compounds that are effective against many bacteria and fungi, which may match the effect of common antibiotics.
 Objective: The aim of this study was to isolate and diagnose fungi that causing vaginal thrush, in pregnant women and to study the effect of (pregnancy and pregnancy sequence and age) on the rate of infection compared to non-pregnant, as well as to study the drug sensitivity of isolates towards a number of antifungal and compared that with the inhibitory effectiveness of tea tree oil.
 Material and Methods: 75 vaginal swabs from pregnant women and 50 from non-pregnant women were collected at ages ranging from 17-65 years. The isolates were diagnosed using several methods, including the Vitek2 Compact system. 17 isolates were selected to study the inhibitory effect of ten antifungal agents, six of them were automatically tested by the Vitek 2 compact system, which contains a sensitivity test kit (AST-YS07 Card). The essential oil (TTO) was analyzed by GC-MS to detect its content of active compounds. The inhibitory effect of TTO was studied according to "Broth dilution" method to determine minimum inhibitory concentration (MIC) for it, the inhibitory effect of four concentrations of TTO (100%, 50%, 25%, 12.5 %) was also tested according to "well diffusion" method. This investigation also included a study of the mechanism of action (TTO).
 RESULTS: The rate of infection among pregnant women was (41%) with the highest rate of infection during the third trimester of pregnancy, while the percentage of non-pregnant women was only 8%. Vaginal infection was also prevalent in the age group ranged between (17-29 years).The isolates showed resistance to (Ketoconazol, Terbinafine) while they were sensitive to (Nystatin, clotrimazol), as well as sensitive to all antifungal of (AST-YS07 Card). The analysis of the TTO using chromatogram showed that it contains 32 chemical compounds, most of them are monoterpene like (Terpinen-4-ol, 1, 8-Cineol). The MIC of TTO ranged between (4 - < 2 µl/ ml). The function of TTO is to destroy the structural structure of the cell membrane and change its permeability, thereby leakage of cellular components and cell death. 
 Conclusion: Pregnancy increases the rate of vaginal candidiasis in women, especially during the third trimester. TTO is highly effective in inhibiting the growth of opportunistic candida yeasts.
 

Leakage Induced in Eschericia coli Cells by Secondary Metabolites of the J7 Bacterial Isolates from the Rhizosphere of Zingiber officinale Roscoe var. Rubrum

Isolate J7 is a bacterial strain separated from the rhizosphere of Zingiber officinale Roscoe var. Rubrum that potentially produces antibacterial compounds against Escherichia coli . The study aimed to determine the antibacterial activity of the most active fraction of this isolate from its capacity to induce leakage in E. coli cells. The secondary metabolites were extracted from Isolate J7 using ethyl acetate solvent and then fractionated with different ratios of hexane and ethyl acetate solvents―1:0, 9:1, 8:2, 7:3, 6:4, 5:5, 4:6, 3:7, 2:8, 1:9, and 0:1 (v/v), ethyl acetate and methanol with 1:1 (v/v) ratio, and methanol 100%. Fractions were identified based on the spotting on the Thin-Layer Chromatography (TLC) plate. Only the most active fraction was tested to define its ability to cause leakage of cellular components like nucleic acid and protein. The leakage was scanned with a UV-Vis spectrophotometer at wavelengths of 260 and 280 nm. The results showed that F2 was the fraction that prevented the growth of E. coli most actively because it created a zone of inhibition sized 11.58±0.95 mm in diameter with the lowest MIC among the other fractions (10%). Also, based on the spectrophotometric analysis, the addition of F2 at concentrations of 10% and 20% resulted in higher levels of protein, DNA, and RNA than the negative control. In conclusion, F2 can cause plasma membrane leakage in E. coli at a concentration of 10%. Another fraction that exhibited antibacterial activity was F3. In the spotting analysis of the TLC plate, F3 appeared to have a spot profile and R f that were similar to F2 but considerably different from the inactive fractions (i.e., showing no antibacterial activity). Observed with multiple wavelengths, the R f values of F2 and F3 spots varied between 0.56-0.57 and 0.61-0.62 (254 nm) and 0.47-0.48 and 0.56-0.57 (366 nm), respectively. Because these spot profiles did not appear in the inactive fractions, compounds with this range of R f values are, thereby, suspected as the active substances that inhibit the growth of E. coli .

Antifungal activity and possible mechanisms of submicron chitosan dispersions against Alteraria alternata

Abstract Submicron chitosan dispersions (SCD) are effective in controlling postharvest decay. The anti-fungal activity of SCD against A. alternata both in vivo and in vitro was evaluated, and possible inhibition mechanisms were explored. Results indicated that SCD markedly inhibited the growth of the pathogenic mycelium in medium, with minimum inhibitory concentration and minimum fungicidal concentration of 0.313 g L−1 and 1.250 g L−1, respectively. The inhibition of spore germination was correlated with SCD dosage when above the concentration of 0.625 g L−1. The decay of black spot rot in jujube fruit was significantly decreased by using SCD at both 0.313 g L−1 and 1.250 g L−1. The antifungal effect of SCD involved an intracellular mode of action via penetration into pathogenic cells instead of accumulating on or combining with cell walls, cell membranes, or septa. The cell membrane permeability was altered by ion exchange or loss of cytoplasmic contents followed by leakage of cellular components, such as proteins and nucleic acids, leading to cell structure breakdown. Given the above, SCD would be a promising alternative control of postharvest diseases of fruit caused by A. alternata, and the value of this approach would be directly attributed to the penetration of pathogenic fungal cells. This effect is due to the dispersion’s small size, increased membrane permeability of fungal cells, and subsequent loss of cytoplasmic contents from the fungal hyphae.