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1.
Food Microbiol ; 87: 103395, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-31948636

RESUMO

Volatile compounds produced by L1 and L8 strains were assayed against mycelia and conidia growth of Monilinia laxa, M. fructicola, M. polystroma, and M. fructigena of stone fruits. Results showed that volatile metabolites inhibited significantly pathogens growth, in particular M. fructigena mycelium growth (70% by L1 and 50% by L8) and M. fructicola conidia germination (85% by L1 and 70% by L8) compared to the control. Moreover, the antagonistic activity was enhanced by the addition of asparagine (120 mg L-1) in the culture media composition. Synthetic pure compounds were tested in vitro on pathogens mycelial and conidia growth and their EC50 values were estimated, confirming 2-phenethyl as the most active compound. For this reason 2-phenethyl and VOCs of both yeast strains were assayed in vivo on cherry, peach, and apricot fruits. Regarding peach fruit, both treatments, yeasts and pure compounds, displayed the best inhibiting action against all the pathogens especially against M. laxa (100% by L1, 84% by L8 and 2-phenethyl). ATR/IR spectroscopy analysis showed how VOCs produced by both strains increase the fruit waxes complexity reducing the pathogens attack so playing an essential role in the antagonistic activity of both yeast strains and on fruit structural composition.


Assuntos
Ascomicetos/química , Fungicidas Industriais/farmacologia , Doenças das Plantas/microbiologia , Compostos Orgânicos Voláteis/farmacologia , Ascomicetos/crescimento & desenvolvimento , Ascomicetos/metabolismo , Frutas/microbiologia , Fungicidas Industriais/química , Fungicidas Industriais/metabolismo , Micélio/efeitos dos fármacos , Micélio/crescimento & desenvolvimento , Prunus persica/microbiologia , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento , Compostos Orgânicos Voláteis/química , Compostos Orgânicos Voláteis/metabolismo
2.
World J Microbiol Biotechnol ; 36(1): 4, 2019 Dec 12.
Artigo em Inglês | MEDLINE | ID: mdl-31832786

RESUMO

Colletotrichum gloeosporioides, one of the main agents of mango anthracnose, causes latent infections in unripe mango, and leads to huge economic losses during storage and transport. Dimethyl trisulfide (DMTS), one of the main volatile compounds produced by some microorganisms or plants, has shown antifungal activity against some phytopathogens in previous studies, but its effects on C. gloeosporioides and mechanisms of action have not been well characterized. In fumigation trials of conidia and mycelia of C. gloeosporioides for 2, 4, 6, 8, or 10 h, at a concentration of 100 µL/L of air space in vitro, DMTS caused serious damage to the integrity of plasma membranes, which significantly reduced the survival rate of spores, and resulted in abnormal hyphal morphology. Moreover, DMTS caused deterioration of subcellular structures of conidia and mycelia, such as cell walls, plasma membranes, Golgi bodies, and mitochondria, and contributed to leakage of protoplasm, thus promoting vacuole formation. In addition, to better understand the molecular mechanisms of the antifungal activity, the global gene expression profiles of isolate C. gloeosporioides TD3 treated in vitro with DMTS at a concentration of 100 µL/L of air for 0 h (Control), 1 h, or 3 h were investigated by RNA sequencing (RNA-seq), and over 62 Gb clean reads were generated from nine samples. Similar expressional patterns for nine differentially expressed genes (DEGs) in both RNA-seq and qRT-PCR assays showed the reliability of the RNA-seq data. In comparison to the non-treated control groups, we found DMTS suppressed expression of ß-1, 3-D-glucan, chitin, sterol biosynthesis-related genes, and membrane protein-related genes. These genes related to the formation of fungal cell walls and plasma membranes might be associated with the toxicity of DMTS against C. gloeosporioides. This is the first study demonstrating antifungal activity of DMTS against C. gloeosporioides on mango by direct damage of conidia and hyphae, thus providing a novel tool for postharvest control of mango anthracnose.


Assuntos
Antifúngicos/farmacologia , Colletotrichum/efeitos dos fármacos , Mangifera/microbiologia , Sulfetos/farmacologia , Quitina/metabolismo , Colletotrichum/isolamento & purificação , Contaminação de Alimentos , Microbiologia de Alimentos , Regulação Fúngica da Expressão Gênica , Hifas/efeitos dos fármacos , Proteínas de Membrana/metabolismo , Viabilidade Microbiana , Microscopia Eletrônica de Transmissão , Micélio/efeitos dos fármacos , Doenças das Plantas/microbiologia , RNA Fúngico/genética , RNA Fúngico/isolamento & purificação , Reprodutibilidade dos Testes , Alinhamento de Sequência , Análise de Sequência de RNA , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/isolamento & purificação , Esteróis/metabolismo , beta-Glucanas/metabolismo
3.
Phytopathology ; 109(12): 2116-2123, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31600112

RESUMO

Fusarium head blight (FHB) is one of the most important cereal diseases worldwide, causing yield losses and contamination of harvested products with mycotoxins. Fusarium graminearum is one of the most common FHB-causing species in wheat and barley cropping systems. We assessed the ability of different botanical extracts to suppress essential stages of the fungal life cycle using three strains of F. graminearum (FG0410, FG2113, and FG1145). The botanicals included aqueous extracts from white mustard (Sinapis alba) seed flour (Pure Yellow Mustard [PYM] and Tillecur [Ti]) as well as milled Chinese galls (CG). At 2% concentration (wt/vol), PYM and Ti completely inhibited growth of mycelium of all F. graminearum strains whereas, at 1%, CG reduced the growth by 65 to 83%, depending on the strain. While PYM and Ti reduced the germination of both conidia and ascospores at 2% (wt/vol), CG was only effective in reducing conidia germination. Perithecia formation of FG0410 but not FG2113 was suppressed by all botanicals. Moreover, application of botanicals on mature perithecia led to a two- to fourfold reduction in discharge of ascospores. Using liquid chromatography (LC) with diode array detection, we quantified the principal glucosinolate component sinalbin of PYM and Ti. LC time-of-flight mass spectrometry was used to demonstrate that the bioactive matrix of CG contains different gallotannins as well as gallic and tannic acids. Possible antifungal mechanisms of the botanical matrices are discussed. The results of this study are promising and suggest that PYM, Ti, and CG should be explored further for efficacy at managing FHB.[Formula: see text] Copyright © 2019 The Author(s). This is an open access article distributed under the CC BY-NC-ND 4.0 International license.


Assuntos
Fusarium , Micotoxinas , Extratos Vegetais , Antifúngicos/química , Antifúngicos/farmacologia , Fusarium/efeitos dos fármacos , Doenças das Plantas/microbiologia , Extratos Vegetais/química , Extratos Vegetais/farmacologia , Esporos Fúngicos/efeitos dos fármacos
4.
Int J Food Microbiol ; 309: 108311, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31499266

RESUMO

Botrytis cinerea causes postharvest spoilage in important crops such as strawberry and other berries. Pulsed light (PL) treatment could be an environmentally friendly postharvest alternative to synthetic fungicides in berries. Cultivability, physiological state, ultrastructure of Botrytis cinerea suspended in peptone water and irradiated with PL (fluence = 1.2 to 47.8 J/cm2) were investigated by using conventional plate count technique, flow cytometry analysis (FCM) and transmission electron microscopy. In addition, PL effect on B. cinerea development in artificially contaminated strawberries throughout storage at (5 ±â€¯1) °C was evaluated. PL reduced fungus' ability to form colonies on agarized culture media. Survival curve fitted with the Weibullian model evidenced a wide distribution of conidia sensitivity to PL. FCM showed that most of irradiated conidia entered in a viable non-culturable state, although a subpopulation without esterase activity and compromised membranes and a subpopulation with active esterase and intact membranes were also detected. PL attacked multiple targets in B. cinerea. Ultrastructural changes varied with the dose and within the conidia population, supporting FCM results. Damage included plasmalemma detachment from cell wall, cytoplasm collapse, and vacuolization of cytoplasm, disruption of cell wall and plasmalemma with massive loss of cytoplasm and/or disruption of organelles. In strawberries artificially contaminated with B. cinerea, a 2-day delay on the onset of the infection and a lower incidence in PL-treated strawberries (11.9 and 23.9 J/cm2) compared to control (16-20%) up to 10 days of cold storage was observed. Results indicated that PL significantly reduces B. cinerea growth in peptone water and in inoculated strawberries. However, other preservation factor(s) in combination would be needed to increase PL action for a better control of this fungus.


Assuntos
Botrytis/crescimento & desenvolvimento , Botrytis/efeitos da radiação , Fragaria/microbiologia , Luz , Doenças das Plantas/terapia , Frutas/microbiologia , Fungicidas Industriais/farmacologia , Doenças das Plantas/microbiologia , Esporos Fúngicos/efeitos dos fármacos
5.
Can J Microbiol ; 65(12): 904-912, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31479614

RESUMO

Lysobacter antibioticus HS124 inhibited mycelial growth of Fusarium graminearum (74.66%) under the dual culture method. Microscopic investigation clearly showed that amendment with different concentrations (10%, 30%, and 50%) of HS124 bacterial culture filtrate on potato dextrose agar plates caused abnormal hyphal structures, including swelling and distortion. Its inhibition toward mycelial growth of F. graminearum was increased with increasing concentration of n-butanol crude extract of HS124. The highest inhibition (43.14%) was detected at a crude concentration of 10 mg/disc, whereas the lowest inhibition (21.57%) was observed at 2 mg/disc. Although mycelial growth of F. graminearum was promoted by volatile organic compounds (VOCs) produced by HS124 as compared with the control, these VOCs clearly decreased fungal pigmentation resulting in a reduction of fungal sporulation. Microscopic investigation revealed hyphal deformation of F. graminearum due to VOCs. These compounds also had a negative effect on spore germination of F. graminearum. In vivo evaluations demonstrated that HS124 inoculation of wheat plants reduced crown rot disease incidence by 73.70% as compared with the control. HS124 inoculation of wheat plants also promoted most of the growth characteristics compared with the control or fungicide-treated plants. Our results provide strong evidence that HS124 could control F. graminearum infections and promote growth of wheat plants as part of management strategies for crown rot disease.


Assuntos
Agentes de Controle Biológico/farmacologia , Fusarium/efeitos dos fármacos , Lysobacter/fisiologia , Doenças das Plantas/prevenção & controle , Triticum/crescimento & desenvolvimento , Triticum/microbiologia , Fusarium/crescimento & desenvolvimento , Fusarium/fisiologia , Hifas/efeitos dos fármacos , Hifas/crescimento & desenvolvimento , Hifas/fisiologia , Lysobacter/metabolismo , Doenças das Plantas/microbiologia , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/fisiologia , Compostos Orgânicos Voláteis/metabolismo , Compostos Orgânicos Voláteis/farmacologia
6.
Food Chem Toxicol ; 134: 110821, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31533060

RESUMO

The antifungal activity of plant essential oils (EOs) extracted by steam distillation from seven different species (Cinnamon, Anise, Clove, Citronella, Peppermint, Pepper, and Camphor) was investigated. Three common fungi were isolated from moldy wheat bread, which were identified as Aspergillus niger, A. oryzae, and A. ochraceus. The antifungal activity of anise, peppermint, clove, cinnamon, pepper, citronella, and camphor EOs from seven different spices was confirmed by agar diffusion assay against three fungi. Among all the EOs, the cinnamon EO showed the highest antifungal activity for all the fungi strains with the largest inhibition zone at the concentration of 800 mg/mL and lowest MIC ranging from 0.0625 to 0.125 mg/mL, followed by clove EO. The remaining EOs exerted moderate inhibitory effects. Further research indicated the substantial inhibitory activities of cinnamon and clove EOs on mycelial growth and spore germination in a dose-dependent manner. Further, the in vivo inhibitory activity of selected EOs on naturally infected bread demonstrated that cinnamon and clove EOs can as be used as natural antifungal agents.


Assuntos
Antifúngicos/farmacologia , Fungos/efeitos dos fármacos , Óleos Voláteis/farmacologia , Plantas/química , Fungos/classificação , Fungos/genética , Genes Fúngicos , Germinação , Testes de Sensibilidade Microbiana , Filogenia , Especificidade da Espécie , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/fisiologia
7.
Appl Microbiol Biotechnol ; 103(18): 7663-7674, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31297555

RESUMO

The inhibitory effect of Bacillomycin D, a cyclic lipopeptide, on Rhizopus stolonifer colonization of cherry tomato was studied, and its possible mechanism of action was explored. Bacillomycin D showed a direct inhibitory effect on R. stolonifer spore germination and mycelial growth in vitro. It conferred both a direct inhibitory effect on R. stolonifer growth in cherry tomato in vivo and induced host resistance in cherry tomato. Moreover, Bacillomycin D treatment significantly increased the activities of plant defense-related enzymes, including chitinase (CHI), ß-1,3-glucanase (GLU), phenylalanine ammonia-lyase (PAL), and peroxidase (POD). Real-time PCR (RT-PCR) showed that defense-related genes involved in the salicylic acid defense signaling pathway and genes encoding pathogenesis-related proteins were up-regulated in Bacillomycin D treatment. Furthermore, Bacillomycin D-C16 resulted in direct inhibition and a remarkable induced resistance to R. stolonifer which was higher than as induced by Bacillomycin D-C14. Together, the data indicated that Bacillomycin D can control the growth of R. stolonifer through both the direct inhibition of the fungus and the activation of defense-related genes and enzymes in cherry tomato.


Assuntos
Peptídeos Catiônicos Antimicrobianos/farmacologia , Frutas/microbiologia , Lycopersicon esculentum/microbiologia , Rhizopus/efeitos dos fármacos , Rhizopus/crescimento & desenvolvimento , Quitinases/metabolismo , Frutas/enzimologia , Glucana 1,3-beta-Glucosidase/metabolismo , Lycopersicon esculentum/enzimologia , Peroxidase/metabolismo , Fenilalanina Amônia-Liase/metabolismo , Doenças das Plantas/microbiologia , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento
8.
J Environ Sci Health B ; 54(9): 781-790, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31264925

RESUMO

The toxicity of four essential oils extracted from Baccharis articulata, Baccharis ochracea, Baccharis psiadioides and Baccharis trimera was tested against the phytopathogen Alternaria alternata, which causes Alternaria stem canker on tomatoes. Diseases caused by Alternaria fungi are responsible for great economic losses in terms of production and are controlled by synthetic fungicides; however, essential oils offer an alternative, since they have been proven to be effective for controlling against various plant pathogens. In this way, the antifungal activity of Baccharis essential oils was tested using potato dextrose agar medium with concentrations ranging from 0.1 to 20.0 µL mL-1. Baccharis trimera and Baccharis ochracea essential oils presented 100% mycelial growth inhibition of A. alternata and were also able to control Alternaria stem canker disease under greenhouse conditions. Tomato plants treated with these essential oils exhibited area under the disease progress curve (AUDPC) values of 230.10 and 241.42, differing from the control condition, which showed an AUDPC value of 268.92. The essential oils of B. trimera and B. ochracea can be an alternative for controlling Alternaria stem canker disease of tomatoes and should be formulated as a potential fungicide against the A. alternata pathogen.


Assuntos
Alternaria/efeitos dos fármacos , Baccharis/química , Fungicidas Industriais/farmacologia , Lycopersicon esculentum/microbiologia , Óleos Voláteis/farmacologia , Doenças das Plantas/microbiologia , Extratos Vegetais/farmacologia , Óleos Vegetais/farmacologia , Alternaria/crescimento & desenvolvimento , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento
9.
Int J Food Microbiol ; 306: 108258, 2019 Oct 02.
Artigo em Inglês | MEDLINE | ID: mdl-31362161

RESUMO

Propionic acid is widely used as a preservative in (poultry) feed. In this study we have isolated and identified fungal strains from nine samples poultry feed originating from different countries. The majority of the strains were Aspergilli with a eurotium-morph, such as Aspergillus proliferans and A. chevalieri. These and three other species were selected and tested for their sensitivity towards the feed preservative propionic acid, among them Penicillium lanosocoeruleum. The determined MIC values of 6.1-31 mM of these poultry feed specific fungi were well in the range as described in literature. Propionic acid (at 31 mM) damages conidia (spores) in a species dependent fashion after a 24-hour-treatment. The majority of the conidia (over 70%) of P. lanosocoeruleum germinated within 60 h on agar medium, while 50 and 80% of the A. chevalieri and A. proliferans conidia did not, respectively. Dependent on the species, cell damage was visible after incubation with propionic acid. Germ tubes of P. lanosocoeruleum in a biofilm showed extensive (85%) cell death after a 30 min treatment with propionic acid and slightly lower sensitivity was observed with A. proliferans (62% cell death). Microscopic analysis of these fungal biofilms revealed extensive damage to the cell membrane and showed distorted intracellular structures. Fluorescent life-dead staining of the germ tubes showed a clear dose response of propionic acid indicating a fungicidal effect on these growing cells. These results show that conidia can be inactivated by propionic acid, but that germ tubes show a much higher sensitivity. These observations shed new light on the mode of action of this important preservative to prevent fungal contamination of feed.


Assuntos
Ração Animal/microbiologia , Aspergillus/efeitos dos fármacos , Fungicidas Industriais/farmacologia , Penicillium/efeitos dos fármacos , Propionatos/farmacologia , Esporos Fúngicos/efeitos dos fármacos , Animais , Aspergillus/classificação , Aspergillus/isolamento & purificação , Biofilmes/efeitos dos fármacos , Meios de Cultura/farmacologia , Eurotium , Microbiologia de Alimentos/métodos , Testes de Sensibilidade Microbiana , Penicillium/classificação , Penicillium/isolamento & purificação , Aves Domésticas
10.
Nat Microbiol ; 4(10): 1654-1660, 2019 10.
Artigo em Inglês | MEDLINE | ID: mdl-31235957

RESUMO

Arbuscular mycorrhizal (AM) fungi are obligate symbionts that depend on living host plants to complete their life cycle1,2. This feature, which leads to their unculturability in the absence of plants, strongly hinders basic research and agricultural application of AM fungi. However, at least one AM fungus can grow and develop fertile spores independently of a host plant in co-culture with the bacterium Paenibacillus validus3. The bacteria-derived substances are thought to act as stimulants or nutrients for fungal sporulation, but these molecules have not been identified. Here, we show that (S)-12-methyltetradecanoic acid4,5, a methyl branched-chain fatty acid isolated from bacterial cultures, stimulates the branching of hyphae germinated from mother spores and the formation of secondary spores in axenic culture of the AM fungus Rhizophagus irregularis. Extensive testing of fatty acids revealed that palmitoleic acid induces more secondary spores than the bacterial fatty acid in R. irregularis. These induced spores have the ability to infect host plant roots and to generate daughter spores. Our work shows that, in addition to a major source of organic carbon6-9, fatty acids act as stimulants to induce infection-competent secondary spores in the asymbiotic stage and could provide the key to developing the axenic production of AM inoculum.


Assuntos
Ácidos Graxos/farmacologia , Glomeromycota/efeitos dos fármacos , Micorrizas/efeitos dos fármacos , Meios de Cultivo Condicionados , Ácidos Graxos/metabolismo , Ácidos Graxos Monoinsaturados/farmacologia , Regulação Fúngica da Expressão Gênica , Glomeromycota/genética , Glomeromycota/crescimento & desenvolvimento , Glomeromycota/fisiologia , Hifas/efeitos dos fármacos , Hifas/genética , Hifas/crescimento & desenvolvimento , Hifas/fisiologia , Micorrizas/genética , Micorrizas/crescimento & desenvolvimento , Micorrizas/fisiologia , Paenibacillus/metabolismo , Raízes de Plantas/microbiologia , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/genética , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/fisiologia
11.
Fungal Biol ; 123(7): 489-496, 2019 07.
Artigo em Inglês | MEDLINE | ID: mdl-31196518

RESUMO

To develop an antimicrobial agent for preventing the devasting damage caused by rice blast, a novel peptide aptamer was identified to interact with calmodulin (CaM) for the inhibition of the spore development in the pathogen Magnaporthe oryzae. A peptide aptamer designated as SNP-D4, consisted of the scaffold protein Staphylococcus aureus nuclease (SN) and an exposed surface loop of 16 random amino acids, was screened from the constructed peptide aptamer libraries by bacterial two-hybrid system using CaM of M. oryzae as the bait. The preliminary inhibition in the sporulation development was observed after treating with the crude extracts expressing SNP-D4. The inhibition efficacies of the purified SNP-D4 were quantified at the stages of conidial germination, germ tube elongation, and appressorium formation in M. oryzae. The binding affinity analysis revealed that SNP-D4 interacted with CaM at a dissociation constant (Kd) of about 20 µM. Moreover, the N-terminus of CaM was identified as the key binding region.


Assuntos
Antifúngicos/metabolismo , Antifúngicos/farmacologia , Aptâmeros de Peptídeos/metabolismo , Aptâmeros de Peptídeos/farmacologia , Calmodulina/metabolismo , Proteínas Fúngicas/metabolismo , Magnaporthe/efeitos dos fármacos , Sequência de Aminoácidos , Antifúngicos/química , Aptâmeros de Peptídeos/química , Sítios de Ligação , Calmodulina/química , Proteínas Fúngicas/química , Magnaporthe/crescimento & desenvolvimento , Oryza/microbiologia , Biblioteca de Peptídeos , Doenças das Plantas/microbiologia , Ligação Proteica , Engenharia de Proteínas , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento
12.
Mar Drugs ; 17(5)2019 May 20.
Artigo em Inglês | MEDLINE | ID: mdl-31137530

RESUMO

Water extracts and polysaccharides from Anabaena sp., Ecklonia sp., and Jania sp. were tested for their activity against the fungal plant pathogen Botrytis cinerea. Water extracts at 2.5, 5.0, and 10.0 mg/mL inhibited B. cinerea growth in vitro. Antifungal activity of polysaccharides obtained by N-cetylpyridinium bromide precipitation in water extracts was evaluated in vitro and in vitro at 0.5, 2.0, and 3.5 mg/mL. These concentrations were tested against fungal colony growth, spore germination, colony forming units (CFUs), CFU growth, and on strawberry fruits against B. cinerea infection with pre- and post-harvest application. In in vitro experiments, polysaccharides from Anabaena sp. and from Ecklonia sp. inhibited B. cinerea colony growth, CFUs, and CFU growth, while those extracted from Jania sp. reduced only the pathogen spore germination. In in vitro experiments, all concentrations of polysaccharides from Anabaena sp., Ecklonia sp., and Jania sp. reduced both the strawberry fruits infected area and the pathogen sporulation in the pre-harvest treatment, suggesting that they might be good candidates as preventive products in crop protection.


Assuntos
Anabaena/química , Antifúngicos/farmacologia , Botrytis/efeitos dos fármacos , Fragaria/efeitos dos fármacos , Fragaria/microbiologia , Feófitas/química , Rodófitas/química , Antifúngicos/isolamento & purificação , Botrytis/fisiologia , Polissacarídeos/isolamento & purificação , Polissacarídeos/farmacologia , Esporos Fúngicos/efeitos dos fármacos , Água/química
13.
J Agric Food Chem ; 67(22): 6212-6221, 2019 Jun 05.
Artigo em Inglês | MEDLINE | ID: mdl-31099566

RESUMO

Common soil fungi, Aspergillus flavus and Aspergillus parasiticus, are opportunistic pathogens that invade preharvest peanut seeds. These fungi often produce carcinogenic aflatoxins that pose a threat to human and animal health through food chains and cause significant economic losses worldwide. Detection of aflatoxins and further processing of crops are mandated to ensure that contaminated agricultural products do not enter food channels. Under favorable conditions, the fungus-challenged peanut seeds produce phytoalexins, structurally related stilbenoids, capable of retarding fungal development. The purpose of the present study was to evaluate the potential influence of peanut phytoalexins on fungal development and aflatoxin formation in the course of peanut-fungus interaction. The present research revealed that during such interaction, aflatoxin formation was completely suppressed in A. flavus and A. parasiticus strains tested, when low concentrations of spores were introduced to wounded preincubated peanuts. In most of the experiments, when fungal spore concentrations were 2 orders of magnitude higher, the spores germinated and produced aflatoxins. Of all experimental seeds that showed fungal growth, 57.7% were aflatoxin-free after 72 h of incubation. The research provided new knowledge on the aflatoxin/phytoalexin formation in the course of peanut-fungus interaction.


Assuntos
Aflatoxinas/biossíntese , Arachis/microbiologia , Aspergillus/metabolismo , Sementes/química , Estilbenos/farmacologia , Arachis/química , Arachis/metabolismo , Aspergillus/efeitos dos fármacos , Aspergillus/crescimento & desenvolvimento , Interações Hospedeiro-Parasita , Doenças das Plantas/microbiologia , Sementes/metabolismo , Sementes/microbiologia , Sesquiterpenos/metabolismo , Sesquiterpenos/farmacologia , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/metabolismo , Estilbenos/metabolismo
14.
Enzyme Microb Technol ; 126: 50-61, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31000164

RESUMO

The biocontrol activity of some soil strains of Chromobacterium sp. against pathogenic fungi has been attributed to secreted chitinases. The aim of this work was to characterize biochemically a recombinant chitinase (CvChi47) from C. violaceum ATCC 12472 and to investigate its effects on phytopathogenic fungi. CvChi47 is a modular enzyme with 450 amino acid residues, containing a type I signal peptide at the N-terminal region, followed by one catalytic domain belonging to family 18 of the glycoside hydrolases, and two type-3 chitin-binding domains at the C-terminal end. The recombinant enzyme was expressed in Escherichia coli as a His-tagged protein and purified to homogeneity. The native signal peptide of CvChi47 was used to direct its secretion into the culture medium, from where the recombinant product was purified by affinity chromatography on chitin and immobilized metal. The purified protein showed an apparent molecular mass of 46 kDa, as estimated by denaturing polyacrylamide gel electrophoresis, indicating the removal of the signal peptide. CvChi47 was a thermostable protein, retaining approximately 53.7% of its activity when heated at 100 °C for 1 h. The optimum hydrolytic activity was observed at 60 °C and pH 5. The recombinant chitinase inhibited the conidia germination of the phytopathogenic fungi Fusarium oxysporum and F. guttiforme, hence preventing mycelial growth. Furthermore, atomic force microscopy experiments revealed a pronounced morphological alteration of the cell surface of conidia incubated with CvChi47 in comparison to untreated cells. Taken together, these results show the potential of CvChi47 as a molecular tool to control plant diseases caused by these Fusarium species.


Assuntos
Antifúngicos/farmacologia , Quitinases/metabolismo , Chromobacterium/enzimologia , Fusarium/crescimento & desenvolvimento , Doenças das Plantas/prevenção & controle , Proteínas Recombinantes/metabolismo , Sequência de Aminoácidos , Domínio Catalítico , Quitinases/química , Quitinases/genética , Clonagem Molecular , Estabilidade Enzimática , Fusarium/efeitos dos fármacos , Doenças das Plantas/microbiologia , Conformação Proteica , Proteínas Recombinantes/química , Proteínas Recombinantes/genética , Homologia de Sequência , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento , Temperatura Ambiente
15.
Analyst ; 144(9): 3136-3143, 2019 Apr 23.
Artigo em Inglês | MEDLINE | ID: mdl-30941383

RESUMO

Nosema bombycis (Nb) is the pathogen that causes pebrine in silkworms. Aldehydes are effective disinfectants commonly used in sericulture. However, the precise mechanism of their action on Nb spores remains unclear. Here, we used laser tweezers Raman spectroscopy to investigate the effects of glutaraldehyde and formaldehyde on individual Nb spores, as well as phase contrast microscopy imaging to monitor the germination dynamics of individual treated spores, to acquire a deeper understanding of the mechanism of action of aldehydes and to provide a theoretical reference for establishing an effective strategy for disease control in sericulture. The positions of the Raman peaks remained constant during treatment. The Raman intensity was enhanced and the germination rate of the spores significantly decreased with treatment time. Tlag, the time when individual spores begin to germinate, and Tgerm, the time for complete germination, increased with enhanced treatment. The germination time (ΔTgerm) showed no significant difference from that for untreated spores. Heterogeneity was shown, which is relevant to the resistance of Nb spores to aldehydes. The results indicate that glutaraldehyde and formaldehyde do not destroy the spore wall and plasma membrane, do not cause the leakage of intracellular components, and might not damage the extrusion apparatus. The effects of aldehydes on Nb spores are mainly on the spore coat. They may block the external factors that stimulate spore germination. Single-cell analysis based on novel optical techniques reveals the action of chemical sporicides on microsporidia spores in real time and explains the heterogeneity of cell stress resistance. These applications of new techniques offer new insight into traditional disinfectants.


Assuntos
Desinfetantes/farmacologia , Formaldeído/farmacologia , Glutaral/farmacologia , Nosema/efeitos dos fármacos , Esporos Fúngicos/efeitos dos fármacos , Microscopia de Contraste de Fase/métodos , Pinças Ópticas , Análise de Célula Única/métodos , Análise Espectral Raman/métodos
16.
Microb Pathog ; 131: 197-204, 2019 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-30980879

RESUMO

The compatibility of the entomopathogenic fungus Metarhizium anisopliae ICIPE 30 which was proved to be pathogenic to adult Spoladea recurvalis, and phenylacetaldehyde (PAA) floral attractant for lepidopteran moths, was investigated under laboratory and field conditions through spatial and temporal separations. Horizontal transmission of M. anisopliae ICIPE 30 between adult S. recurvalis and the number of conidia picked up by a single moth from the autoinoculation device were also determined under laboratory tests. When freshly emerged moths were inoculated with fungal conidia ("donors") and maintained together with an equal number of untreated freshly emerged moths ("recipients") in the laboratory, they were able to transmit infection to untreated moths resulting to 76.9% mortality with an LT50 value of 6.9 days. The quantity of conidia a moth could acquire and retain from the autoinoculation device in the laboratory was assessed at 0, 24, 48, and 72 h post-inoculation. The overall mean number of conidia acquired by a single moth was significantly higher immediately after exposure (0 h) (14.3 ±â€¯2.5 × 105) than at 24, 48, and 72 h after inoculation (F = 10.26, Df = 3,8, P = 0.003), though a single moth still retained 4.6 ±â€¯0.9 × 105 conidia 72 h post inoculation. Laboratory results showed that PAA completely inhibited the germination of the conidia 8 days post exposure, while the conidial viability was not affected in the control treatment without PAA. Under field conditions, the inhibitory effects of PAA on conidial germination was minimized by placing it at a distance of 5-10 cm from M. anisopliae isolate ICIPE 30 conidia. There was no significant difference in conidial germination in the control treatment and in treatments where PAA was placed at 5 cm and 10 cm away from M. anisopliae isolate ICIPE 30. Conidial germination was low in the autoinoculation device that had PAA directly exposed to the fungus. PAA is therefore compatible with M. anisopliae ICIPE 30 for use in integrated management of S. recurvalis, if spatially separated 5 cm away from the fungus and could thus be combined in an autocontamination devices for the control of S. recurvalis.


Assuntos
Acetaldeído/análogos & derivados , Transmissão de Doença Infecciosa/prevenção & controle , Metarhizium/efeitos dos fármacos , Metarhizium/patogenicidade , Mariposas/microbiologia , Micoses/transmissão , Acetaldeído/farmacologia , Animais , Agentes de Controle Biológico , Inseticidas/química , Inseticidas/farmacologia , Larva/crescimento & desenvolvimento , Larva/microbiologia , Micoses/microbiologia , Micoses/prevenção & controle , Controle Biológico de Vetores/métodos , Feromônios/farmacologia , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/crescimento & desenvolvimento
17.
Food Microbiol ; 82: 82-88, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31027823

RESUMO

Different methods have been applied in controlling contamination of foods and feeds by the carcinogenic fungal toxin, aflatoxin, but nevertheless the problem remains pervasive in developing countries. Curcumin is a natural polyphenolic compound from the spice turmeric (Curcuma longa L.) that has been identified as an efficient photosensitiser for inactivation of Aspergillus flavus conidia. Curcumin mediated photoinactivation of A. flavus has revealed the potential of this technology to be an effective method for reducing population density of the aflatoxin-producing fungus in foods. This study demonstrates the influence of pH and temperature on efficiency of photoinactivation of the fungus and how treating spore-contaminated maize kernels affects aflatoxin production. The results show the efficiency of curcumin mediated photoinactivation of fungal conidia and hyphae were not affected by temperatures between 15 and 35 °C or pH range of 1.5-9.0. The production of aflatoxin B1 was significantly lower (p < 0.05), with an average of 82.4 µg/kg as compared to up to 305.9 µg/kg observed in untreated maize kept under similar conditions. The results of this study indicate that curcumin mediated photosensitization can potentially be applied under simple environmental conditions to achieve significant reduction of post-harvest contamination of aflatoxin B1 in maize.


Assuntos
Aflatoxina B1/metabolismo , Aspergillus flavus/efeitos dos fármacos , Aspergillus flavus/efeitos da radiação , Curcumina/farmacologia , Transtornos de Fotossensibilidade , Zea mays/microbiologia , Concentração de Íons de Hidrogênio , Hifas/efeitos dos fármacos , Hifas/efeitos da radiação , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/efeitos da radiação , Temperatura Ambiente
18.
Microbiol Res ; 221: 60-69, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30825942

RESUMO

Bacteria isolated from different environments can be exploited for biocontrol purposes by the identification of the molecules involved in the antifungal activity. The present study was aimed at investigating antifungal protein compounds purified from a previously identified plant growth promoting bacterium, Pseudomonas protegens N isolated from agricultural land in northern Algeria. Therefore, a novel protein was purified by chromatographic and ultrafiltration steps and its antifungal activity together with growth-inhibition mechanism was evaluated against different fungi by plate-based assays. In addition, stereomicroscopy and transmission electron microscopy (TEM) was performed to explore the inhibition activity of the compound on spore germination processes. The protein, showing a molecular mass of about 100 kDa under native conditions, was revealed to be in the surface-membrane fraction and displayed an efficient activity against a variety of phytopathogenic fungi, being Alternaria the best target towards which it exhibited a marked fungicidal action and inhibition of spore germination. Moreover, the compound was able to significantly decrease fungal infection on tomato fruits producing also morphological aberrations on conidia. The obtained results suggested that the isolated compound could represent a promising agent for eco-friendly management of plant pathogens in agriculture.


Assuntos
Alternaria/crescimento & desenvolvimento , Antifúngicos/farmacologia , Agentes de Controle Biológico/farmacologia , Pseudomonas/metabolismo , Esporos Fúngicos/crescimento & desenvolvimento , Argélia , Alternaria/efeitos dos fármacos , Lycopersicon esculentum/microbiologia , Testes de Sensibilidade Microbiana , Desenvolvimento Vegetal/fisiologia , Reguladores de Crescimento de Planta/metabolismo , Plantas/microbiologia , Pseudomonas/isolamento & purificação , Rizosfera , Microbiologia do Solo , Esporos Fúngicos/efeitos dos fármacos
19.
Sci Total Environ ; 671: 59-65, 2019 Jun 25.
Artigo em Inglês | MEDLINE | ID: mdl-30927728

RESUMO

Exposure to viable bacterial and fungal spores re-aerosolized from air handling filters may create a major health risk. Assessing and controlling this exposure have been of interest to the bio-defense and indoor air quality communities. Methods are being developed for inactivating stress-resistant viable microorganisms collected on ventilation filters. Here we investigated the inactivation of spores of Bacillus thuringiensis var. kurstaki (Btk), a recognized simulant for B. antracis, and Aspergillus fumigatus, a common opportunistic pathogen used as an indicator for indoor air quality. The viability change was measured on filters treated with ultraviolet (UV) irradiation and gaseous iodine. The spores were collected on high-efficiency particulate air (HEPA) and non-HEPA filters, both flattened for testing purposes to represent "surface" filters. A mixed cellulose ester (MCE) membrane filter was also tested as a reference. Additionally, a commercial HEPA unit with a deep-bed (non-flattened) filter was tested. Combined treatments of Btk spores with UV and iodine on MCE filter produced a synergistic inactivation effect. No similar synergy was observed for A. fumigatus. For spores collected on an MCE filter, the inactivation effect was about an order of magnitude greater for Btk compared to A. fumigatus. The filter type was found to be an important factor affecting the inactivation of Btk spores while it was not as influential for A. fumigatus. Overall, the combined effect of UV irradiation and gaseous iodine on viable bacterial and fungal spores collected on flat filters was found to be potent. The benefit of either simultaneous or sequential treatment was much lower for Btk spores embedded inside the deep-bed (non-flattened) HEPA filter, but for A. fumigatus the inactivation on flattened and non-flattened HEPA filters was comparable. For both species, applying UV first and gaseous iodine second produced significantly higher inactivation than when applying them simultaneously or in an opposite sequence.


Assuntos
Filtros de Ar/microbiologia , Poluição do Ar em Ambientes Fechados/análise , Desinfecção/métodos , Iodo/administração & dosagem , Esporos Bacterianos/efeitos dos fármacos , Esporos Fúngicos/efeitos dos fármacos , Raios Ultravioleta , Aspergillus fumigatus/efeitos dos fármacos , Aspergillus fumigatus/fisiologia , Bacillus thuringiensis/efeitos dos fármacos , Bacillus thuringiensis/fisiologia , Gases/administração & dosagem , Esporos Bacterianos/fisiologia , Esporos Fúngicos/fisiologia
20.
Food Microbiol ; 81: 108-114, 2019 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-30910081

RESUMO

Fungi are able to grow on diverse food products and contribute to food spoilage worldwide causing food loss. Consumers prefer freshly squeezed fruit juices, however, the shelf life of these juices is limited due to outgrowth of yeast and fungi. The shelf life of pulsed electric field (PEF) treated juice can be extended from 8 days up to a few weeks before spoilage by moulds becomes apparent. Conidia produced by three Penicillium ssp. (Penicillium expansum, Penicillium buchwaldii and Penicillium bialowiezense), previously isolated from spoiled PEF treated fruit juice and smoothie, were characterized for resistance towards selected mild physical processing techniques in orange juice and toward sanitizers on surfaces. The results show that Penicillium spp. conidia are susceptible to mild heat, high pressure pasteurization (HPP), PEF, cold atmospheric plasma (CAP), UV, and chemical sanitizers chlorine dioxide and hypochlorite albeit with different susceptibility. Treatment with mild heat, HPP, PEF, or chlorine dioxide reduced conidia by more than 5 log. For hypochlorite, UV, and CAP the reduction was between 1 and 3 log. Together, this study provides data for the development of intervention strategies to eliminate spoilage mould conidia in fruit juices.


Assuntos
Desinfecção/métodos , Conservação de Alimentos/métodos , Sucos de Frutas e Vegetais/microbiologia , Penicillium/efeitos dos fármacos , Penicillium/efeitos da radiação , Esporos Fúngicos/efeitos dos fármacos , Esporos Fúngicos/efeitos da radiação , Compostos Clorados/farmacologia , Citrus sinensis , Eletricidade , Manipulação de Alimentos , Armazenamento de Alimentos , Temperatura Alta , Ácido Hipocloroso/farmacologia , Testes de Sensibilidade Microbiana , Óxidos/farmacologia , Pasteurização/métodos , Penicillium/crescimento & desenvolvimento , Penicillium/isolamento & purificação , Gases em Plasma/farmacologia , Esporos Fúngicos/crescimento & desenvolvimento , Esporos Fúngicos/isolamento & purificação , Raios Ultravioleta
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