RESUMEN
The development of alternatives for the use of chemical pesticides for plant disease control is the present-day and ongoing challenge for achieving sustainable agriculture. Pseudomonas fluorescens SF4c, native strain from wheat, produces tailocins (phage-tail-like bacteriocins) with antimicrobial activity against several phytopathogenic strains. We thus investigated the efficacy of foliar application of these bacteriocins to control the bacterial-spot disease in tomato caused by Xanthomonas vesicatoria Xcv Bv5-4a. The disease severity and incidence index were reduced by 44 and 36%, respectively; while the number of viable cells of X. vesicatoria Xcv Bv5-4a decreased after bacteriocin treatment. Furthermore, bacteriocin was effective in reducing bacterial-spot-disease symptoms on tomato fruits even when applied 12â¯h after infection. Tailocin activity was not affected by abiotic influences such as adjuvant, light and temperature and, biotic factors such as apoplastic-fluids. In contrast, no antibacterial activity of these tailocins was observed when the bacteriocin was exposed to extremely dry conditions. Finally, that no cytotoxic effects on mammalian cells were observed with this representative tailocins is highly significant and demonstrates the safety of such compounds in humans. All these findings indicate that the SF4c tailocins represent an attractive alternative to copper-containing bactericides for use in the control of bacterial spot.
Asunto(s)
Infecciones Bacterianas/tratamiento farmacológico , Bacteriocinas/farmacología , Enfermedades de las Plantas/microbiología , Enfermedades de las Plantas/terapia , Pseudomonas fluorescens/metabolismo , Solanum lycopersicum/microbiología , Xanthomonas vesicatoria/efectos de los fármacos , Animales , Antibacterianos/biosíntesis , Antibacterianos/farmacología , Antibiosis , Bacteriocinas/química , Bacteriocinas/aislamiento & purificación , Bacteriocinas/metabolismo , Agentes de Control Biológico/metabolismo , Agentes de Control Biológico/farmacología , Chlorocebus aethiops , Eritrocitos/efectos de los fármacos , Luz , Solanum lycopersicum/crecimiento & desarrollo , Hojas de la Planta/citología , Hojas de la Planta/efectos de los fármacos , Hojas de la Planta/microbiología , Ovinos , Temperatura , Células Vero/efectos de los fármacos , Xanthomonas vesicatoria/patogenicidadRESUMEN
Among many sources of natural bioactive substances, mushrooms constitute a huge and mostly unexplored group. Biologically active secondary metabolites of Ganoderma, a group of wood-degrading mushrooms, have recently been reviewed. Our previous study revealed the antimicrobial activity of extracts from G. resinaceum grown in submerged culture against phytopathogens. Different factors can influence the production of secondary metabolites, including nutritional factors. In this study we evaluated the influence of different culture conditions on the antimicrobial activity of extracts from liquid cultures of G. resinaceum, through use of a factorial design. Minimum inhibitory concentrations for extracts produced under different culture conditions were determined against Staphylococcus aureus and Xanthomonas vesicatoria. Based on the results of these assays, larger-scale cultures in malt extract broth supplemented with 20 g/L glucose and a 15-day incubation time should be performed in order to isolate from G. resinaceum antibiotic compound(s) that are potentially useful against S. aureus. In addition, pH 5 should be considered for the production of antimicrobial metabolites against X. vesicatoria from supernatant broths or extracts from G. resinaceum.
Asunto(s)
Antibacterianos/metabolismo , Técnicas de Cultivo , Ganoderma/metabolismo , Antibacterianos/aislamiento & purificación , Antibacterianos/farmacología , Medios de Cultivo , Ganoderma/crecimiento & desarrollo , Staphylococcus aureus/efectos de los fármacos , Temperatura , Xanthomonas vesicatoria/efectos de los fármacosRESUMEN
A bioassay-guided fractionation of the ethyl acetate extract from the twigs of the hybrid poplar 'Neva', Populus nigra L. × Populus deltoides Marsh, led to the isolation of three flavonoids, which were identified by means of spectrometric and physicochemical analysis as 5-hydroxy-7-methoxy-flavone (1), 5,7-dihydoxy-flavone (2) and 5,7-dihydroxy-flavonol (3). These compounds were further screened for their antimicrobial activity against plant pathogens, including three bacteria (Pseudomonas lachrymans, Ralstonia solanacearum and Xanthomonas vesicatoria) and one fungus (Magnaporthe oryzae). Compounds 2 and 3 showed significant antibacterial activity, with minimum inhibitory concentrations (MICs) ranging from 15 to 25 µg mL(-1), and median inhibitory concentrations (IC(50) values) from 4 to 18 µg mL(-1). The results obtained provide promising baseline information for the potential use of the extract and flavonoids from this plant as antimicrobial agents to help control plant diseases.
Asunto(s)
Antiinfecciosos/farmacología , Flavonoides/farmacología , Populus/química , Relación Dosis-Respuesta a Droga , Evaluación Preclínica de Medicamentos , Flavonoides/química , Concentración 50 Inhibidora , Magnaporthe/efectos de los fármacos , Pruebas de Sensibilidad Microbiana , Estructura Molecular , Pseudomonas/efectos de los fármacos , Ralstonia/efectos de los fármacos , Xanthomonas vesicatoria/efectos de los fármacosRESUMEN
This study was to isolate antibacterial compounds from Gleditsia sinensis Lam. spines through bioassay-guided fractionation (against a Gram-positive bacterium Xanthomonas vesicatoria and a Gram-negative bacterium Bacillus subtilis). The crude ethanol extract of G. sinensis spines was partitioned sequentially with solvents of increasing polarity. The ethyl acetate fraction, which exhibited the most significant antibacterial activities among all the solvent fractions, was further separated by column chromatograph, yielding seven phenolic compounds including ethyl gallate (1) and caffeic acid (7), and five flavonoids, dihydrokaempferol (2), eriodictyol (3), quercetin (4), 3,3',5',5,7-pentahydroflavanone (5) and (-)-epicatechin (6). Compounds 4, 5 and 7 showed moderate inhibitory activities against both bacterial species, with compound 7 having the lowest minimal inhibitory concentration (MIC) of 0.125 mg mL(-1), while compounds 1 and 2 showed a weak inhibitory activity only against B. subtilis (MIC 1.00 mg mL(-1)), and compounds 3 and 6 showed insignificant activity against the two bacteria.