Effect of allyl-isothiocyanate on survival and antimicrobial peptide expression following oral bacterial infections in Drosophila melanogaster.

Since infections with antibiotic-resistant bacteria cause increasing problems worldwide, the identification of alternative therapies is of great importance. Plant-derived bioactives, including allyl-isothiocyanate (AITC), have received attention for their antimicrobial properties. The present study therefore investigates the impact of AITC on survival and antimicrobial peptide (AMP) levels in Drosophila melanogaster challenged with the fly pathogenic bacteria Pectobacterium carotovorum subsp. carotovorum and Leuconostoc pseudomesenteroides. AITC, a sulfur-containing compound derived from glucosinolates, exhibits antimicrobial properties and has been suggested to modulate AMP expression. By using D. melanogaster, we demonstrate that AITC treatment resulted in a concentration-dependent decrease of survival rates among female flies, particularly in the presence of the Gram-negative bacterium Pectobacterium carotovorum subsp. carotovorum, whereas AITC did not affect survival in male flies. Despite the ability of isothiocyanates to induce AMP expression in cell culture, we did not detect significant changes in AMP mRNA levels in infected flies exposed to AITC. Our findings suggest sex-specific differences in response to AITC treatment and bacterial infections, underlining the complexity of host-pathogen interactions and potential limitations of AITC as a preventive or therapeutic compound at least in D. melanogaster models of bacterial infections.

Green synthesis of metal nanoparticles and study their anti-pathogenic properties against pathogens effect on plants and animals.

According to an estimate, 30% to 40%, of global fruit are wasted, leading to post harvest losses and contributing to economic losses ranging from $10 to $100 billion worldwide. Among, all fruits the discarded portion of oranges is around 20%. A novel and value addition approach to utilize the orange peels is in nanoscience. In the present study, a synthesis approach was conducted to prepare the metallic nanoparticles (copper and silver); by utilizing food waste (Citrus plant peels) as bioactive reductants. In addition, the Citrus sinensis extracts showed the reducing activity against metallic salts copper chloride and silver nitrate to form Cu-NPs (copper nanoparticles) and Ag-NPs (Silver nanoparticles). The in vitro potential of both types of prepared nanoparticles was examined against plant pathogenic bacteria Erwinia carotovora (Pectobacterium carotovorum) and pathogens effect on human health Escherichia coli (E. coli) and Staphylococcus aureus (S. aureus). Moreover, the in vivo antagonistic potential of both types of prepared nanoparticles was examined by their interaction with against plant (potato slices). Furthermore, additional antipathogenic (antiviral and antifungal) properties were also examined. The statistical analysis was done to explain the level of significance and antipathogenic effectiveness among synthesized Ag-NPs and Cu-NPs. The surface morphology, elemental description and size of particles were analyzed by scanning electron microscopy, transmission electron microscopy, energy-dispersive spectroscopy and zeta sizer (in addition polydispersity index and zeta potential). The justification for the preparation of particles was done by UV-Vis Spectroscopy (excitation peaks at 339 nm for copper and 415 nm for silver) and crystalline nature was observed by X-ray diffraction. Hence, the prepared particles are quite effective against soft rot pathogens in plants and can also be used effectively in some other multifunctional applications such as bioactive sport wear, surgical gowns, bioactive bandages and wrist or knee compression bandages, etc.

Orostachys malacophylla (pall.) fisch extracts alleviate intestinal inflammation in Drosophila.

ETHNOPHARMACOLOGICAL RELEVANCE: Orostachys malacophylla (Pall.) Fisch (O. malacophylla) is a succulent herbaceous plant that is the Orostachys genus of Crassulaceae family. O. malacophylla has been widely used as a traditional Chinese medicine with antioxidant, anti-inflammatory, anti-febrile, antidote, anti-Toxoplasma gondii properties. However, the biological function of alleviating intestinal inflammation and key bioactive compounds were still unknown. AIM OF THE STUDY: We used a Drosophila model to study the protective effects and bioactive compounds of O. malacophylla water extract (OMWE) and butanol extract (OMBE) on intestinal inflammation. MATERIALS AND METHODS: Drosophila intestinal inflammation was induced by oral invasion of dextran sodium sulfate (DSS) or Erwinia carotovora carotovora 15 (Ecc15). We revealed the protective effects of two extracts by determining intestinal reactive oxygen species (ROS) and antimicrobial peptide (AMP) levels and intestinal integrity, and using network pharmacology analysis to identify bioactive compounds. RESULTS: We demonstrated that both OMWE and OMBE could ameliorate the detrimental effects of DSS, including a decreased survival rate, elevated ROS levels, increased cell death, excessive proliferation of ISCs, acid-base imbalance, and disruption of intestinal integrity. Moreover, the overabundance of lipid droplets (LDs) and AMPs by Ecc15 infection is mitigated by these extracts, thereby enhancing the flies' resistance to adverse stimuli. In addition, we used widely targeted metabolomics and network pharmacology analysis to identify bioactive compounds associated with IBD healing that are present in OMWE and OMBE. CONCLUSIONS: In summary, our research indicates that OMWE and OMBE significantly mitigate intestinal inflammation and have the potential to be effective therapeutic agents for IBD in humans.

Fruit juice mediated multicomponent reaction for the synthesis of substituted isoxazoles and their in vitro bio-evaluation.

A simple, efficient and eco-friendly procedure for the synthesis of isoxazole derivatives (4a-4h) using one-pot three-component reaction between substituted aldehydes (1a), methyl acetoacetate (2a) and hydroxylamine hydrochloride (3a) has been achieved in presence of Cocos nucifera L. juice, Solanum lycopersicum L. juice and Citrus limetta juice respectively. The homogeneity of synthesized compounds was confirmed by melting point and thin layer chromatography. The synthesized compounds were characterized by using 1H NMR, FTIR and CHN analyses and evaluated for in vitro herbicidal activity against Raphanus sativus L. (Radish seeds). The compounds (4a-4h) were also screened for their fungicidal activity against Rhizoctonia solani and Colletotrichum gloeosporioides. Antibacterial activity was also tested against Erwinia carotovora and Xanthomonas citri. From bio-evaluation data, it was found that compound 4b was most active against Raphanus sativus L. (root) and Raphanus sativus L. (shoot) respectively. Compound 4b was also found most active against both the fungus viz. R. solani and C. gloeosporioides showing maximum percentage growth inhibition i.e. 90.00 against R. solani and 82.45 against C. gloeosporioides at 2000 µg/mL concentration. Compound 4 h has shown maximum inhibition zone i.e. 3.00-9.60 mm against Erwinia carotovora at 2000 µg/mL concentration. Maximum Xanthomonas citri growth was also inhibited by compound 4 h showing inhibition zone 1.00-5.00 mm at highest concentration.

Activity of Adesmia boronioides resinous exudate against phytopathogenic bacteria.

Resinous exudate obtained from the aerial parts of Adesmia boronioides Hook.f. were evaluated to determine anti-phytopathogenic effects. Briefly, resinous exudate was obtained by dipping fresh plant material in dichloromethane; chemical composition was determined by GC-MS; and minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) were evaluated against four phytopathogenic bacteria. Resinous exudate yield was 8.5% (resin/fresh plant), of which esquel-6-en-9-one (14.25%), esquel-7-en-9-one (5.86%), and veratric acid (2.59%) were the effective antibacterial compounds. Tested against Pectobacterium carotovorum subsp. carotovora, Erwinia amylovora, Bacillus subtilis, and Pseudomonas syringae, MICs and MBCs ranged from 16 to 128 µg/mL and 32-256 µg/mL, respectively. These results provide initial evidence that resinous bush A. boronioides is a new and alternative source of substances with agricultural interest.

Application of natural-based nanocoatings for extending the shelf life of green bell pepper fruit.

Pectobacterium carotovorum is a phytopathogenic bacteria that causes significant economic loses in food crops, such as bell pepper, which is of special significance in the value of production and trade in Mexico. Therefore, a solution for fruit conservation must be sought. Due to environmental concerns, it is necessary the use of environmentally-friendly active packaging. In this article, chitosan and chitosan-thyme essential oil nanocoatings were used for the preservation of green bell pepper. Different formulations based on chitosan nanoparticles (CSNPs) and chitosan-thyme essential oil nanoparticles (15, 30, and 45%) were prepared. For uncoated and coated bell peppers, the quality and physiological variables of inoculated and uninoculated fruit with P. carotovorum during 12-day storage period were assessed. According to the results, the weight loss of the fruit remained almost constant over the storage days for the different formulations. A decrease in fruit firmness and an increase in the respiration rate and ascorbic acid content until day 8 with a decrease at the end of the storage period were observed. Of all the evaluated nanocoatings, the fruit treated with the formulation containing 15% CSNPs showed the lowest colony-forming units and disease incidence. Also, the coated bell peppers with this formulation had lower CO2 production compared to the remaining treatments, and the weight loss and firmness were maintained. Therefore, the use of CSNP coatings could represent a good alternative for the protection of bell pepper against the pathogenic bacteria P. carotovorum. PRACTICAL APPLICATION: The results of the application of nanocoatings based on chitosan and chitosan-thyme essential oil as an antibacterial agent against P. carotovorum on green bell pepper during 12-day storage period suggest that nanoparticle-based coatings can be a natural option for the preservation of fruit quality during ripening.

Non-hydrolytic synthesis of caprylate capped cobalt ferrite nanoparticles and their application against Erwinia carotovora and Stenotrophomonas maltophilia.

Magnetic cobalt Ferrite nanoparticles capped with caprylate groups, CH3(CH2)6CO2-, have been synthesized using a novel non-hydrolytic coprecipitation method under inert conditions. Particle diameter was characterized using dynamic light scattering (DLS) and transmission electron microscopy (TEM). The spinel ferrite crystal phase was verified using X-ray diffraction (XRD), and the presence of the capping agent was confirmed using Fourier Transform Infrared spectroscopy (FTIR). Bactericidal effects of the particles were tested against broth cultures of Erwinia carotovora and Stenotrophomonas maltophilia. The final particles had an average diameter of 3.81 nm and readily responded to a neodymium magnet. The particles did have a significant effect on the OD600 of both broth cultures.

Efficacy of Argentinean propolis extracts on control of potato soft rot caused by Erwinia carotovora subsp.

BACKGROUND: Erwinia carotovora subsp. cause the potato soft rot, which is a major disease in agriculture. Antibacterial agents currently applied on potato soft rot often offer a restricted control and have several disadvantages. Propolis has shown a wide range of antimicrobial activity, although its effect has not been investigated on E. carotovora subsp. In this work, we tested extracts from propolis samples of Northwest Argentina against E. carotovora subsp. RESULTS: Ethanolic propolis extracts (EPEs) from samples of Santiago del Estero province, particularly from sample 4 (EPE4), showed the highest antibacterial activity, which was associated with the highest content of flavonoids. 2',4'-Dihydroxychalcone, 2',4'-dihydroxy-3'-methoxychalcone, galangin, and pinocembrin were identified as antibacterial constituents of EPE4. 2',4'-Dihydroxychalcone showed an antibacterial activity (minimum inhibitory concentration, MIC = 0.3-1.2 µg gallic acid equivalents (GAE) mL-1 ; minimum bactericidal concentration, MBC = 0.6-4.8 µg GAE mL-1 ) lower than that of bacterimycin (MIC = 2.4-9.6 µg mL-1 ; MBC = 19.2-38.4 µg GAE mL-1 ) and streptocycline (MIC = 19.2-38.4 µg mL-1 ; MBC = 38.4-76.8 µg mL-1 ). Preventive assays on unwounded and wounded potatoes showed that their immersion in EPE4 containing 87.5 µg GAE mL-1 or streptocycline containing 40 µg mL-1 was equally effective in controlling potato soft rot, reducing the disease incidence by 64.6-67.0% (unwounded tubers) and 88.0-86.0% (wounded tubers) and the disease severity by 49.8-49.8% (unwounded tubers) and 54.5-68.5% (wounded tubers). CONCLUSIONS: Flavonoid-rich propolis extracts from Northwest Argentina efficiently reduced in vivo the incidence and severity of potato soft rot caused by E. carotovora subsp.

Linolenic fatty acid hydroperoxide acts as biocide on plant pathogenic bacteria: Biophysical investigation of the mode of action.

Fatty acid hydroperoxides (HPO) are free phyto-oxylipins known for their crucial role as signalling molecules during plant defense mechanisms. They were also demonstrated to have direct biocidal activities against plant pathogens including gram negative bacteria. In the present work, the biocidal effect of one linolenic fatty acid hydroperoxide, namely 13-HPOT has been investigated on three plant pathogen gram negative bacteria: Pectobacterium carotovorum, Pseudomonas syringae and Xanthomonas translucens. We showed that 13-HPOT has a strong dose response effect on those phytopathogens. In a second part, the molecular mechanism behind the antibacterial effect of 13-HPOT was investigated at a molecular level using an integrative biophysical approach combining in vitro and in silico methods. Since other antimicrobial amphiphilic molecules have been shown to target the lipid membrane of the organisms they act on, we focused our study on the interaction of 13-HPOT with biomimetic membranes. In a first step, we hypothesized that the inner membrane of the bacteria was the main site of action of 13-HPOT and hence we used lipids representative of this membrane to form our models. Our results indicated that 13-HPOT can interact with the lipid representative of the inner bacterial plasma membrane. A strong membrane insertion is suggested but no major permeabilization of the membrane is observed. Phosphatidylethanolamine (PE) and cardiolipin (CL), present in the bacterial plasma membrane, appear to play important roles in this interaction. We suggest that the mode of action of 13-HPOT should involve either subtle changes in membrane properties, such as its lateral organization and distribution, and/or interactions with membrane proteins.

Needle in a haystack: Antibacterial activity-guided fractionation of a potato wound tissue extract.

Erwinia carotovora is a major cause of potato tuber infection, which results in disastrous failures of this important food crop. There is currently no effective antibiotic treatment against E. carotovora. Recently we reported antibacterial assays of wound tissue extracts from four potato cultivars that exhibit a gradient of russeting character, finding the highest potency against this pathogen for a polar extract from the tissue formed immediately after wounding by an Atlantic cultivar. In the current investigation, antibacterial activity-guided fractions of this extract were analyzed by liquid chromatography-mass spectrometry (LC-MS) utilizing a quadrupole-time-of-flight (QTOF) mass spectrometer. The most active chemical compounds identified against E. carotovora were: 6-O-nonyl glucitol, Lyratol C, n-[2-(4-Hydroxyphenyl)] ethyldecanamide, α-chaconine and α-solanine. Interactions among the three compounds, ferulic acid, feruloyl putrescine, and α-chaconine, representing metabolite classes upregulated during initial stages of wound healing, were also evaluated, offering possible explanations for the burst in antibacterial activity after tuber wounding and a chemical rationale for the temporal resistance phenomenon.

Polyphenols, Antioxidant, Antibacterial, and Biofilm Inhibitory Activities of Peel and Pulp of Citrus medica L., Citrus bergamia, and Citrus medica cv. Salò Cultivated in Southern Italy.

The aim of this paper was to study the polyphenols of peel and pulp of three Citrus taxa-Citrus medica, Citrus bergamia, and Citrus medica cv. Salò-cultivated in the Cosenza province, Southern Italy, and to evaluate their antioxidant and antibacterial activity, performed against Escherichia coli, Listeria monocytogenes, Pseudomonas aeruginosa, Staphylococcus aureus, and Pectobacterium carotovorum. Furthermore, we assessed the inhibitory effect of the extracts on bacterial capacity to form biofilm, and on the metabolic activity of the cells present therein. The results indicated that such extracts could find new potential applications in the field of natural antioxidant and anti-bacterial agents in pharmaceutics, agriculture, and food fields.

AhlX, an N-acylhomoserine Lactonase with Unique Properties.

N-Acylhomoserine lactonase degrades the lactone ring of N-acylhomoserine lactones (AHLs) and has been widely suggested as a promising candidate for use in bacterial disease control. While a number of AHL lactonases have been characterized, none of them has been developed as a commercially available enzymatic product for in vitro AHL quenching due to their low stability. In this study, a highly stable AHL lactonase (AhlX) was identified and isolated from the marine bacterium Salinicola salaria MCCC1A01339. AhlX is encoded by a 768-bp gene and has a predicted molecular mass of 29 kDa. The enzyme retained approximately 97% activity after incubating at 25 °C for 12 days and ~100% activity after incubating at 60 °C for 2 h. Furthermore, AhlX exhibited a high salt tolerance, retaining approximately 60% of its activity observed in the presence of 25% NaCl. In addition, an AhlX powder made by an industrial spray-drying process attenuated Erwinia carotovora infection. These results suggest that AhlX has great potential for use as an in vitro preventive and therapeutic agent for bacterial diseases.

Cellular alterations in Pectobacterium carotovorum treated with nanostructured formulations during the incubation time.

Pectobacterium carotovorum was incubated in formulations of chitosan nanoparticles or thyme essential oil-loaded chitosan nanoparticles for a maximum period of 48 h time. The cellular changes and viability were evaluated by transmission electron microscopy (TEM), and two colorimetric assays 3-(4,5 dimethylthiazol-2-yl)-2,5diphenyl tetrazolium bromide (MTT) and alamar blue (AMB), respectively. The incubation time and the addition of the secondary metabolite to the formulation were key factors to the cell damage and cell inhibitory effects on P. carotovorum, TEM observations overall demonstrated on the treated bacterium, cell surface alterations such as deforming and disappearance of the cell wall and the plasmatic membrane, with agglomeration of nanoparticles outside and inside of the cells, loss of cell content and lysis. Cell viability was reduced about 80% (MTT) and 100% (AMB) in the applied treatment of chitosan-loaded thyme essential oil nanoparticles after 48 h incubation, in addition, the total cell inhibition was shown from 6 h incubation onwards with the AMB assay. The TEM micrographs and the cell viability assays provided enough evidence of the antimicrobial activity of the nanostructured formulations compared with the control where no damage was observed.

Temporal resistance of potato tubers: Antibacterial assays and metabolite profiling of wound-healing tissue extracts from contrasting cultivars.

Solanum tuberosum, commonly known as the potato, is a worldwide food staple. During harvest, storage, and distribution the crop is at risk of mechanical damage. Wounding of the tuber skin can also become a point of entry for bacterial and fungal pathogens, resulting in substantial agricultural losses. Building on the proposal that potato tubers produce metabolites to defend against microbial infection during early stages of wound healing before protective suberized periderm tissues have developed, we assessed extracts of wound tissues from four potato cultivars with differing skin morphologies (Norkotah Russet, Atlantic, Chipeta, and Yukon Gold). These assays were conducted at 0, 1, 2, 3 and 7 days post wounding against the plant pathogen Erwinia carotovora and a non-pathogenic Escherichia coli strain that served as a control. For each of the potato cultivars, only polar wound tissue extracts demonstrated antibacterial activity. The polar extracts from earlier wound-healing time points (days 0, 1 and 2) displayed notably higher antibacterial activity against both strains than the later wound-healing stages (days 3 and 7). These results support a burst of antibacterial activity at early time points. Parallel metabolite profiling of the extracts revealed differences in chemical composition at different wound-healing time points and allowed for identification of potential marker compounds according to healing stage for each of the cultivars. It was possible to monitor the transformations in the metabolite profiles that could account for the phenomenon of temporal resistance by looking at the relative quantities of various metabolite classes as a function of time.

Biological control of the soft rot bacterium Pectobacterium carotovorum by Bacillus amyloliquefaciens strain Ar10 producing glycolipid-like compounds.

Four hundred and fifty bacteria were evaluated for antagonistic activity against bacterial soft rot of potato caused by Pectobacterium carotovorum sp strain II16. A strain Ar10 exhibiting potent antagonist activity has been identified as Bacillus amyloliquefaciens on the basis of biochemical and molecular characterization. Cell free supernatant showed a broad spectrum of antibacterial activity against human and phytopathogenic bacteria in the range of 10-60 AU/mL. Incubation of P. carotovorum cells with increasing concentrations of the antibacterial compound showed a killing rate of 94.8 and 96% at MIC and 2xMIC respectively. In addition, the antibacterial agent did not exert haemolytic activity at the active concentration and has been preliminary characterized by TLC and GC-MS as a glycolipid compound. Treatment of potato tubers with strain Ar10 for 72 h significantly reduced the severity of disease symptoms (100 and 85.05% reduction of necrosis deep / area and weight loss respectively). The same levels in disease symptoms severity was also recorded following treatment of potato tubers with cell free supernatant for 1 h. Data suggest that protection against potato soft rot disease may be related to glycolipid production by strain Ar10. The present study affords new alternatives for anti-Pectobacterium carotovorum bioactive compounds against the soft rot disease of potato.

Aspergoterpenins A⁻D: Four New Antimicrobial Bisabolane Sesquiterpenoid Derivatives from an Endophytic Fungus Aspergillus versicolor.

Aspergoterpenins A⁻D (1⁻4), four new bisabolane sesquiterpenoid derivatives, were obtained from the endophytic fungus, Aspergillus versicolor, together with eight known compounds (5⁻12), and their structures were elucidated by a comprehensive analysis of their NMR (Nuclear Magnetic Resonance), MS (Mass Spectrum) and CD (Circular Dichroism) spectra. Aspergoterpenin A (1) was the first example with a characteristic ketal bridged-ring part in the degraded natural bisabolane-type sesquiterpene structures. The compounds 1⁻12 displayed no significant activities against four cancer cell lines (A549, Caski, HepG2 and MCF-7). Further, the antimicrobial activities to Erwinia carotovora sub sp. Carotovora were evaluated, and the results showed that compounds 1⁻12 displayed antimicrobial activities with MIC values ranging from 15.2 to 85.2 µg/mL.

Efficient antibacterial nanosponges based on ZnO nanoparticles and doxycycline.

Bacterial soft rot is responsible for the loss of about 25% of worldwide production in vegetables and fruits. Efforts have been made to develop an effective nanosponge with the capacity to load and release antibacterial drugs to protect plants. Based on the potential of the ZnO nanoparticles (ZnO-NPs) to achieve this goal, this study synthesized NP via the sol-gel and hydrothermal methods by controlling native defects, such as oxygen vacancies, using thermal treatments and reduced atmospheres. To characterize the ZnO NPs, X-ray diffraction (XRD), Raman spectroscopy, transmission electron microscopy (TEM), optical spectroscopy, electron paramagnetic resonance (EPR), Zeta Potential measurements and surface area with the Brunauer-Emmett-Teller (BET) method were used. The photophysical and photochemical properties via spin trapping method aligned with EPR using UVA light showed a greater formation of electron-hole pairs and hydroxyl radicals for the reduced ZnO NPs when compared with the oxidized ones. Additionally, we found that reduced ZnO-NPs have high effectively against Escherichia coli, Erwinia carotovora and Pantoea sp. bacteria using the photocatalytic effect in the UV range. Moreover, ZnO-NPs loaded with DOX release profile enables the release of DOX within 46days, where 25% was released during the first 10h followed by a second delivery phase with an interesting short-term efficacy (<1day) against E. carotovora and Pantoea sp. Bacteria. For the first time, it was demonstrated that ZnO-NPs and ZnO-NPs loaded with DOX have efficient UV photocatalytic activities against bacterial soft rot infections.

Antibacterial activities of the phytochemicals-characterized extracts of Callistemon viminalis, Eucalyptus camaldulensis and Conyza dioscoridis against the growth of some phytopathogenic bacteria.

Three bacterial isolates were isolated from infected potato tubers showing soft and brown rots like symptoms as well as one isolate from infected peach tree showing crown gall symptom. The morphological, biochemical and molecular assays proved that bacterial isolates belonging to Pectobacterium carotovorum subsp. carotovorum, Ralstonia solanacearum, Dickeya spp. and Agrobacterium tumefaciens. The acetone (AcE) and n-butanol (ButE) extracts of Callistemon viminalis flowers and essential oil from aerial parts of Conyza dioscoridis as well as ButE of Eucalyptus camaldulensis bark are evaluated at different concentrations against the growth of the isolated bacteria. The diameter of inhibition zone (IZ) and the minimum inhibitory concentrations (MICs) are compared. Results indicated that the highest IZ values were 20.0 mm and 18.3 mm for E. camaldulensis bark ButE and C. viminalis flower ButE, respectively, against P. carotovorum; 16.3 mm and 16.0 mm for E. camaldulensis bark ButE and C. viminalis flower ButE, respectively, against R. solanacearum; 18.5 mm for C. viminalis flower AcE and C. dioscoridis aerial parts EO against Dickeya spp.; and 15.0 mm for C. viminalis flower AcE against A. tumefaciens. MICs ranged from <16 µg/mL for D. solani to >4000 µg/mL for A. tumefaciens. It was proved that C. viminalis flowers AcE contains mainly 5-hydroxymethylfurfural (20.6%), palmitic acid (18.5%), and pyrogallol (16.4%); while C. viminalis flower ButE contains palmitic acid (36.3%), 2-hydroxymyristic acid (9.4%), 5-hydroxymethylfurfural (7.2%), and shikimic acid (6.6%); whereas E. camaldulensis bark ButE contains 8-nonynoic acid methyl ester (45.6), camphor (30.9%), menthol (8.8%), and 1,8-cineole (eucalyptol) (8.2%), whilst the EO of C. dioscoridis aerial parts comprises Z-(13,14-epoxy)tetradec-11-en-1-ol acetate (11.6%), γ-elemene (10.2%), tau.-muurolol (7.1%), and cadina-3,9-diene (4.7%). It can be concluded that phytochemical extracts of C. viminalis, E. camaldulensis and C. dioscoridis demonstrated strong to moderate antibacterial effects against the studied plant bacterial pathogens.

Effect of Salicylic Acid on the Growth and Chemical Responses of Pectobacterium carotovorum subsp. carotovorum.

BACKGROUND AND OBJECTIVE: Salicylic acid is a signal molecule which activates plant defense against plant pathogens such as the soft rot enterobacterium Pectobacterium carotovorum subsp. carotovorum. The objectives of study were to determine bactericidal effects of salicylic acid on the growth of P. carotovorum subsp. carotovorum and secondly, assess chemical responses of P. carotovorum subsp. carotovorum to salicylic acid. MATERIALS AND METHODS: Pectobacterium carotovorum subsp. carotovorum was grown in lysogeny broth amended with salicylic acid at concentrations of 0, 100, 200, 400, 800 and 1200 mg L-1. The P. carotovorum subsp. carotovorum cultures were incubated at 25°C and sampled at two time points, 0 h (sampled before incubation) and 24 h. Bacterial counts were done at the onset of the incubation (0 h) and after the 24 h incubation. The set which was incubated for 24 h was split into two, one subset was centrifuged and the other was not. From the centrifuged subset the supernatant was recovered and was, together with all the other samples (0 and 24 h not centrifuged), analyzed with1H nuclear magnetic resonance and gas chromatography. RESULTS: Bacterial counts done before and after incubation showed that the lower concentrations of salicylic acid, 0, 100, 200 and 400 mg L-1, supported the growth of P. carotovorum subsp. carotovorum whereas the higher concentrations of 800 and 1200 mg L-1 inhibited the growth of the bacterium completely. Nuclear magnetic resonance results showed either slight or no differences in the metabolite profiles and gas chromatography showed different responses without a clearly defined pattern among the experimental treatments. However, methanethiol was detected by both nuclear magnetic resonance and gas chromatography in all the treatments and was probably formed as a result of the breakdown of lysogeny broth. CONCLUSION: From the results obtained it was concluded that salicylic acid promotes the growth of P. carotovorum subsp. carotovorum at lower concentrations of 0-400 mg L-1 but higher concentrations of salicylic acid of 800 and 1200 mg L-1 inhibit bacterial growth. All the tested salicylic acid concentrations (0-1200 mg L-1) cause only slight chemical shifts in the bacterial culture. Methanethiol was detected in all treatments and it is probably formed from the breakdown of lysogeny broth.

Pectin-conjugated silica microcapsules as dual-responsive carriers for increasing the stability and antimicrobial efficacy of kasugamycin.

Kasugamycin is an aminoglycoside antibiotic originally isolated from Streptomyces kasugaensis, which has been widely used for the management of plant diseases. However, photo-thermal instability and low efficiency limit its application. Therefore, it is an urgent task to prevent unwanted loss of kasugamycin and ensure maximum bioactivity at target site. In this work, a novel formulation of kasugamycin that responds to different biological stimuli produced by pests was prepared using silica microcapsules crosslinked with pectin via special disulfide bonds. The results demonstrated that the silica-SS-pectin microcapsules had a high loading efficiency (20% w/w) and could effectively enhance the thermal and light stability of kasugamycin. The microcapsules displayed excellent pectinase and glutathione dual-responsive properties and the release kinetics investigated by Riger-Peppas model suggested combination of various release mechanisms. Compared with kasugamycin wettable powder, the microcapsules possessed sustained and improved antimicrobial efficacy against Erwinia carotovora. Thus, the dual-responsive microcapsules potentially have agricultural application as a controlled release system.