Inhibition Of Fungal Spore Germination Research Articles

Application of Pinhole Plasma Jet Activated Water against Escherichia coli, Colletotrichum gloeosporioides, and Decontamination of Pesticide Residues on Chili (Capsicum annuum L.).

Plasma activated water (PAW) generated from pinhole plasma jet using gas mixtures of argon (Ar) and 2% oxygen (O2) was evaluated for pesticide degradation and microorganism decontamination (i.e., Escherichia coli and Colletotrichum gloeosporioides) in chili (Capsicum annuum L.). A flow rate of 10 L/min produced the highest concentration of hydrogen peroxide (H2O2) at 369 mg/L. Results showed that PAW treatment for 30 min and 60 min effectively degrades carbendazim and chlorpyrifos by about 57% and 54% in solution, respectively. In chili, carbendazim and chlorpyrifos were also decreased, to a major extent, by 80% and 65% after PAW treatment for 30 min and 60 min, respectively. E. coli populations were reduced by 1.18 Log CFU/mL and 2.8 Log CFU/g with PAW treatment for 60 min in suspension and chili, respectively. Moreover, 100% of inhibition of fungal spore germination was achieved with PAW treatment. Additionally, PAW treatment demonstrated significantly higher efficiency (p < 0.05) in controlling Anthracnose in chili by about 83% compared to other treatments.

Penicillium growth inhibition, fruit decay reduction, and polymethoxyflavones and scoparone induction in satsuma mandarin irradiated with ultraviolet-A light-emitting diodes

In this study, we investigated the effects of ultraviolet (UV)-A light-emitting diodes (LEDs) on the inhibition of fungal spore germination, fruit decay, and accumulation of secondary metabolites, including phytoalexins, in satsuma mandarin. We examined the growth and development of blue (Penicillium italicum) and green (Penicillium digitatum) molds exposed to UV-A LED irradiation in vitro and found that UV-A LEDs with an emission peak of 375 nm and light intensity of 9.4 W m−2 significantly reduced the growth of both these fungi. In addition, wounded fruits inoculated with P. digitatum were irradiated with UV-A LEDs for 6 days, and we monitored the subsequent changes in green mold symptoms. The results indicated that low-intensity UV-A LED treatment significantly reduced green mold symptoms in fruit, being the effect most pronounced inhibitory on Penicillium sporulation. Furthermore, wounded fruits subjected to UV-A LED treatment were found to have significantly higher contents of the coumarin compound scoparone than fruits maintained in the dark. Contrastingly, scoparone was barely detectable in non-wounded fruits, irrespective of UV-A LED irradiation. The contents of nobiletin, tangeretin, and hesperidin were likewise found to be higher in wounded fruits treated with UV-A LED than in either non-wounded or non-irradiated fruits. These results indicate that treatment with low-intensity UV-A LED irradiation is sufficient to reduce mold symptom development, and accordingly could represent a promising safe approach to the control of post-harvest decay in citrus fruits. On the basis of our observations, we speculate that the biosynthesis of scoparone, polymethoxyflavones, and flavanones could be induced when the peel is injured and irradiated with UV-A contributing to a reduction in fruit decay.

Biocontrol potential of Streptomyces sp. CACIS-1.5CA against phytopathogenic fungi causing postharvest fruit diseases

BackgroundFungi are one of the microorganisms that cause most damage to fruits worldwide, affecting their quality and consumption. Chemical controls with pesticides are used to diminish postharvest losses of fruits. However, biological control with microorganisms or natural compounds is an increasing alternative to protect fruits and vegetables. In this study, the antifungal effect of Streptomyces sp. CACIS-1.5CA on phytopathogenic fungi that cause postharvest tropical fruit rot was investigated.Main bodyAntagonistic activity was evaluated in vitro by the dual confrontation over fungal isolates obtained from grape, mango, tomato, habanero pepper, papaya, sweet orange, and banana. The results showed that antagonistic activity of the isolate CACIS-1.5CA was similar to the commercial strain Streptomyces lydicus WYEC 108 against the pathogenic fungi Colletotrichum sp., Alternaria sp., Aspergillus sp., Botrytis sp., Rhizoctonia sp., and Rhizopus sp. with percentages ranging from 30 to 63%. The bioactive extract obtained from CACIS-1.5 showed a strong inhibition of fungal spore germination, with percentages ranging from 92 to 100%. Morphological effects as irregular membrane border, deformation, shrinkage, and collapsed conidia were observed on the conidia. Molecularly, the biosynthetic clusters of genes for the polyketide synthase (PKS) type I, PKS type II, and NRPS were detected in the genome of Streptomyces sp. CACIS-1.5CA.ConclusionsThis study presented a novel Streptomyces strain as a natural alternative to the use of synthetic fungicides or other commercial products having antagonistic microorganisms that were used in the postharvest control of phytopathogenic fungi affecting fruits.

Isolation of a Novel Kluyveromyces marxianus Strain QKM-4 and Evidence of Its Volatilome Production and Binding Potentialities in the Biocontrol of Toxigenic Fungi and Their Mycotoxins

To overcome the economic losses associated with fungi and their toxic metabolites, environmentally safe and efficient approaches are needed. To this end, biological control using yeasts and safe bacterial strains and their products are being explored to replace synthetic fungicides. In the present study, the biocontrol effect of a yeast strain of Kluyveromyces marxianus, QKM-4, against the growth and mycotoxin synthesis potential of key toxigenic fungi was evaluated. In vitro assays were performed to find the application of yeast volatile organic compounds (VOCs) against fungal contamination on important agricultural commodities. The removal of ochratoxin A (OTA) and deoxynivalenol (DON) by living and heat-inactivated yeast cells was also explored. VOCs produced by strain QKM-4 were able to significantly limit the fungal growth of 17 fungal species belonging to genera Aspergillus, Penicillium, and Fusarium. Yeast VOCs were able to reduce OTA biosynthesis potential of Penicillium verrucosum and Aspergillus carbonarius by 99.6 and 98.7%, respectively. In vivo application of QKM-4 VOCs against Fusarium oxysporum and A. carbonarius infection on tomatoes and grapes, respectively, determined a complete inhibition of fungal spore germination. GC/MS-based analysis of yeast VOCs identified long-chain alkanes, including nonadecane, eicosane, docosane, heptacosane, hexatriacontane, and tetracosane. In vitro testing of the mycotoxin-binding potential of the living and heat-inactivated QKM-4 cells showed a reduction of OTA and DON up to 58 and 49%, respectively, from artificially contaminated buffers. Our findings clearly demonstrate the strong antifungal potential of K. marxianus QKM-4 and propose this strain as a strong candidate for application in agriculture to safeguard food and feed products.

Biocontrol ability and action mechanisms of Aureobasidium pullulans GE17 and Meyerozyma guilliermondii KL3 against Penicillium digitatum DSM2750 and Penicillium expansum DSM62841 causing postharvest diseases.

Epiphytic yeasts were isolated from different cultivars of apples and lemons and identified by a combination of PCR-RFLP of 5.8S rRNA region and sequencing of D1/D2 domain of the 26S rRNA gene. Among 69 isolates, Aureobasidium pullulans GE17 and Meyerozyma guilliermondii KL3 strains showed the greatest antagonistic activity against two significant apple and lemon postharvest pathogens, Penicillium expansum DSM62841 (blue mold) and Penicillium digitatum DSM2750 (green mold), after preliminary screening. Yeasts were applied as single and mixed cultures with two different cell concentrations of 106 and 108 cells/ml in the present study. It was determined that antagonistic activity of two yeast strains studied emerged with a combination of several mechanisms of action including competition for space and nutrients, production of volatile organic compounds (VOCs), secretion of extracellular lytic enzymes and inhibition of fungal spore germination. The highest inhibition of mycelial growth on P. expansum DSM62841 and P. digitatum DSM2750 (83.4% and 74.7%, respectively) was achieved by utilization of single culture of A. pullulans GE17. Otherwise, the application of mixed culture at the ratio of 108 cells/ml inhibited spore germination of both pathogens from 86% to 95%. Results of this study suggest that an increase in yeast cell concentrations positively affected their biocontrol activity against blue and green molds. According to the results, employing single culture of M. guilliermondii KL3 did not exhibit effective antagonistic activity against blue and green molds. However, utilization of A. pullulans GE17 alone and mixed culture showed succesfull controlling against both P. expansum DSM62841 and P. digitatum DSM2750.

Evaluation of Inhibition of Fungal Spore Germination by Rhizospheric Bacterial Extracts

Evaluation of Inhibition of Fungal Spore Germination by Rhizospheric Bacterial Extracts

Optimizing Crops for Biocontrol of Pests and Disease.

Volatile compounds and extrafloral nectar are common defenses of wild plants; however, in crops they bear an as-yet underused potential for biological control of pests and diseases. Odor emission and nectar secretion are multigene traits in wild plants, and thus form difficult targets for breeding. Furthermore, domestication has changed the capacity of crops to express these traits. We propose that breeding crops for an enhanced capacity for tritrophic interactions and volatile-mediated direct resistance to herbivores and pathogens can contribute to environmentally-friendly and sustainable agriculture. Natural plant volatiles with antifungal or repellent properties can serve as direct resistance agents. In addition, volatiles mediating tritrophic interactions can be combined with nectar-based food rewards for carnivores to boost indirect plant defense.

Antifungal modes of action of Saccharomyces and other biocontrol yeasts against fungi isolated from sour and grey rots

The aim of this study was to determine the putative modes of action of 59 viticultural yeasts (31 Saccharomyces and 28 non-Saccharomyces) that inhibited fungi isolated from sour and grey rot in grapes. Inhibition of fungal mycelial growth by metabolites, enzyme activities (laminarinases, chitinases), antifungal volatiles, competition for nutrients (siderophores, Niche Overlap Index (NOI)), inhibition of fungal spore germination and decreased germinal tube length and induction of resistance were assayed. Biofungicide yeasts were classified into “antifungal patterns”, according to their mechanisms of action. Thirty isolates presented at least two of the mechanisms assayed. We propose that inhibition of fungal mycelial growth by metabolites, laminarinases, competition for nutrients, inhibition of fungal spore germination and decreased germinal tube length, and antifungal volatiles by Saccharomyces and non-Saccharomyces viticultural yeasts is used as putative biocontrol mechanisms against phytopathogenic fungi. Twenty-four different antifungal patterns were identified. Siderophore production (N)and a combination of siderophore production and NOI>0.92 (M)were the most frequent antifungal patterns observed in the biofungicide yeasts assayed. Elucidation of these mechanisms could be useful for optimization of an inoculum formulation, resulting in a more consistent control of grey and sour rot with Saccharomyces and non-Saccharomyces biocontrol yeasts.

The Effect of Various Thymus pulegioides Chemotypes Essential Oils and pH on Food Spoilage Microorganisms

:In this study, we determined the antimicrobial activity of Thymus pulegioides L. chemotypes geraniol/geranial/neral (G/G/N), carvacrol/γ-terpinene/p-cymeme (C/γT/pC) and linalool (L) essential oils. We observed the effect of pH and of the essential oils on microorganisms. Activities of essential oils of different Thymus pulegioides chemotypes were tested with three pH's, i.e. 3, 6, and 9. The essential oils from T. pulegioides chemotype G/G/N were the most active, L – least active. The results of the bioassays showed a significant inhibition of fungal spore germination by different concentration of G/G/N chemotype. The studied chemotypes were more active than the synthetic preservative (potassium sorbate and sodium benzoate) which displayed an antifungal activity at pH 3 and 6. The statistically significant effect of pH increases with decreasing of essential oil concentration of C/γT/pC chemotype, while the statistically significant effect of pH decreases with decreasing of essential oil concentration of L chemotype.

Anti-dermatophytic activity of marine sponge, Sigmadocia carnosa (Dendy) on clinically isolated fungi

ObjectiveTo screen the anti-fungal effects and find out the active metabolites from sponge, Sigmadocia carnosa (S. carnosa) against four dermatophytic fungi. MethodsThe methanol, ethyl acetate and acetone extract of marine sponge, S. carnosa was examined against Trichophyton mentagrophytes (T. mentagrophytes), Trichophyton rubrum (T. rubrum), Epidermophyton floccosum (E. floccosum) and Microsporum gypseum (M. gypseum) and qualitative analysed to find out the active molecules. ResultsThe methanol extract of sponge was expressed significant activity than ethyl acetate and acetone. The minimum inhibitory concentration (MIC) of methanol extract of sponge that resulted in complete growth inhibition of T. mentagrophytes, T. rubrum, E. floccosum and M. gypseum were found to 125, 250, 250 and 250 μg/mL respectively. But, 100 % inhibition of fungal spore germination was observed in T. mentagrophytes at 500 μg/mL concentration followed by T. rubrum, E. floccosum and M. gypseum at 1 000 μg/mL concentration. Other two extracts showed weak anti spore germination activity against the tested dermatophytic fungi. Methanol extracts showed presence of terpenoids, steroids, alkaloids, saponins and glycosides. ConclusionBased on the literature, this is the first study which has conducted to inhibit the growth and spore germination of dermatophytic fungi with S. carnosa. Further research also needs to purify and characterize the secondary metabolites from the sponge, S. carnosa for the valuable source of novel substances for future drug discovery.

A study on trypsin, Aspergillus flavus and Bacillus sp. protease inhibitory activity in Cassia tora (L.) syn Senna tora (L.) Roxb. seed extract.

BackgroundProteases play an important role in virulence of many human, plant and insect pathogens. The proteinaceous protease inhibitors of plant origin have been reported widely from many plant species. The inhibitors may potentially be used for multiple therapeutic applications in viral, bacterial, fungal diseases and physiological disorders. In traditional Indian medicine system, Cassia tora (Senna tora) is reportedly effective in treatment of skin and gastrointestinal disorders. The present study explores the protease inhibitory activity of the above plant seeds against trypsin, Aspergillus flavus and Bacillus sp. proteases.MethodsThe crushed seeds of Cassia tora were washed thoroughly with acetone and hexane for depigmentation and defatting. The proteins were fractionated by ammonium sulphate (0-30, 30-60, 60-90%) followed by dialysis and size exclusion chromatography (SEC). The inhibitory potential of crude seed extract and most active dialyzed fraction against trypsin and proteases was established by spot test using unprocessed x-ray film and casein digestion methods, respectively. Electrophoretic analysis of most active fraction (30-60%) and SEC elutes were carried employing Sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE) and Gelatin SDS-PAGE. Inhibition of fungal spore germination was studied in the presence of dialyzed active inhibitor fraction. Standard deviation (SD) and ANOVA were employed as statistical tools.ResultsThe crude seeds' extract displayed strong antitryptic, bacterial and fungal protease inhibitory activity on x-ray film. The seed protein fraction 30-60% was found most active for trypsin inhibition in caseinolytic assay (P < 0.001). The inhibition of caseinolytic activity of the proteases increased with increasing ratio of seed extract. The residual activity of trypsin, Aspergillus flavus and Bacillus sp. proteases remained only 4, 7 and 3.1%, respectively when proteases were incubated with 3 mg ml-1 seed protein extract for 60 min. The inhibitory activity was evident in gelatin SDS-PAGE where a major band (~17-19 kD) of protease inhibitor (PI) was detected in dialyzed and SEC elute. The conidial germination of Aspergillus flavus was moderately inhibited (30%) by the dialyzed seed extract.ConclusionsCassia tora seed extract has strong protease inhibitory activity against trypsin, Aspergillus flavus and Bacillus sp. proteases. The inhibitor in Cassia tora may attenuate microbial proteases and also might be used as phytoprotecting agent.

New Caloporoside Derivatives and their Inhibition of Fungal Spore Germination

In our ongoing screening culture fluid extracts of Gloeoporus (Caloporus) dichrous strain 83065 inhibited the germination of Magnaporthe grisea and Fusarium graminearum spores. While isolating the active metabolites two new caloporosides, caloporoside G and caloporoside H, in addition to the known caloporoside derivatives F-16438G, caloporoside A, and 2-hydroxy-6-(16-hydroxyheptadecyl)benzoic acid were obtained.

Inhibitory activity of Indian spice plant Cinnamomum zeylanicum extracts against Alternaria solani and Curvularia lunata, the pathogenic dematiaceous moulds

BackgroundDematiaceous moulds are pathogenic microorganisms and act as etiological agents of mycoses with different degrees of severity in humans and animals. These moulds also cause loss of food crops and storage food products. The information regarding antimicrobial efficacy of the plant preparations on these moulds is scanty. The present study reveals phytochemical characterization and the effect of bark and leaf extracts of Indian spice plant, Cinnamomum zeylanicum (Cz), against the growth of two species of dematiaceous moulds, Alternaria solani and Curvularia lunata.MethodsCz bark and leaf samples were sequentially extracted in different solvents using Soxhlet apparatus. Phytochemical analyses of extracts were done as per standard protocols. The antifungal bioassay of extracts was done by hanging drop technique. The inhibition of fungal spore germination was monitored under influence of three different concentrations of extracts.ResultsThe lowest test concentration (50 μg/ml) of extracts of Cz bark prepared into acetone and that of Cz leaf into petroleum ether and ethanol exhibited complete inhibition (100%) of spore germination in both the moulds. At 100 μg/ml concentration all the extracts showed about 50 to 100% inhibition. However, the treatment of the spores of the two fungal species with highest concentration (500 μg/ml) of bark and leaf extracts in all the solvents showed 100% fungicidal activity as it completely arrested the germination of spores. Relatively lower activity of aqueous extracts at 50 and 100 μg/ml concentrations suggests that the antifungal ingredients present in Cz bark and leaf are more soluble in organic solvents than water.ConclusionThe results demonstrated that the Cz bark and leaves contain certain fungicidal constituents exhibiting potential antimould activity against A. solani and C. lunata.

Induction of systemic disease resistance and pathogen defence responses in Asparagus officinalis inoculated with nonpathogenic strains of Fusarium oxysporum

The ability of nonpathogenic isolates of Fusarium oxysporum (npFo) to induce systemic resistance and defence responses against subsequent challenge with a pathogenic strain of F. oxysporum f. sp. asparagi (Foa) was examined in Asparagus officinalis. In a split‐root experiment, roots inoculated with npFo exhibited a hypersensitive response and those subsequently inoculated with Foa displayed resistance. Induction of systemic resistance in npFo‐treated plants led to significantly fewer necrotic lesions (P = 0·05) and reduced Foa disease severity compared with plants not treated with npFo. In hyphal‐sandwich root inoculation experiments, activities of peroxidase and phenylalanine ammonia‐lyase and lignin content were higher in npFo‐treated plants and increased more rapidly than in npFo‐untreated plants after Foa inoculation. Antifungal activity (inhibition of fungal spore germination and germ‐tube growth) from exudates of roots inoculated with Foa were observed for npFo‐treated plants but not for npFo‐untreated plants. Thus, isolates of npFo may function as inducers of systemic acquired resistance (SAR) and defence responses against Foa invasion in A. officinalis.

Inhibition of fungal spore germination by Nasutitermes: evidence for a possible antiseptic role of soldier defensive secretions.

The antifungal property of two of the principal components of the terpenoid frontal gland secretions of nasute termite soldiers was studied by incubating spore suspensions of the fungus Metarhizium anisopliae with α-pinene and limonene singly or in combination at different concentrations. In vitro assays showed that these substances reduced spore germination through direct and indirect (vapor) contact. To determine if the frontal gland secretions protected termites from fungal infection in vivo, the effect of M. anisopliae on the time course of survival of Nasutitermes costalis and N. nigriceps was studied by exposing termites to either a 4.3 × 107 spores/ml or a control sporeless suspension. The caste composition of experimental groups was manipulated to create mixed-caste subcolonies and monocaste groups. Relative to Coptotermes formosanus, a species that relies on the mechanical defenses of soldiers, N. costalis and N. nigriceps were less susceptible to fungal infection. Spore-exposed N. costalis and N. nigriceps termites had 1.2 times the hazard ratio of death of controls, while the hazard ratio of death of spore-exposed C. formosanus was 11.4 times that of controls. Although the lower susceptibility to infection in Nasutitermes may be explained in part by the antifungal properties of α-pinene and limonene, group composition also played a major role in the survival of spore-exposed termites. Mixed-caste and soldier monocaste groups had 3.4 and 4.7 times the hazard ratio of death, respectively, relative to the worker monocaste treatment. These results suggest that although Nasutitermes terpenoid secretions may have antifungal properties, the caste composition of groups and the social interactions of termites also play a role in determining susceptibility to fungal infection.

A comparison of two methods for testing defined formulations of PVC for resistance to fungal colonisation with two methods for the assessment of their biodegradation

Using plasticised PVC of defined formulation containing a biocide, a comparison has been made of two methods used to assess resistance to fungal colonisation (inhibition of fungal spore germination and use as a carbon source by test fungi) with two physical methods used to assess biodegradation (changes in tensile strength and in extension under load). The results of the first two methods were easier to interpret, but there was general agreement with the results of the measurements of physical characteristics. There are however problems with the choice of methods for the assessment of bioresistance and biodegradation and these are discussed.

Isolation and characterization of genes encoding two chitinase enzymes from Serratia marcescens

Analysis of clones isolated from a cosmid DNA library indicates that the Serratia marcescens chromosome contains at least two genes, chiA and chiB, which encode distinct secreted forms of the enzyme chitinase. These genes have been characterized by inspection of chitinase activity and secreted proteins in Escherichia coli strains containing subclones of these cosmids. The two chitinase genes show no detectable homology to each other. DNA sequence analysis of one of the genes predicts an amino acid sequence with an N-terminal signal peptide typical of genes encoding secreted bacterial proteins. This gene was mutagenized by cloning a neomycin phosphotransferase gene within its coding region, and the insertion mutation was recombined into the parental S. marcescens strain. The resulting chiA mutant transconjugant showed reduced chitinase production, reduced inhibition of fungal spore germination and reduced biological control of a fungal plant pathogen.

Inhibition of fungal spore germination by gramicidin S and its potential use as a biocontrol against fungal plant pathogens

Gramicidin S, as well as being sporicidal to Bacillus spores, also inhibits germination and emergence of fungal-like spores of Dictyostelium discoideum. The fungal plant pathogen Fusarium nivale is also inhibited and gramicidin S, therefore, is a sporicidal and antifungal antibiotic. Considering these findings the potential use of this antibiotic and its producer organism Bacillus brevis as a biocontrol is discussed.

Activation of Soil Microflora by Fungus Spores in Relation to Soil Fungistasis

Summary: Bacterial numbers in natural soil supplemented with living fungus spores or cell-free aqueous washings of spores, then incubated for 8 hr or more, were several-fold higher than those in non-supplemented soil. Rates of oxygen uptake in natural soil supplemented with washed or unwashed fungus spores, cell-free aqueous washings of spores, killed spores, or diluted nutrients, were several-fold higher than those in non-supplemented soil. Increased respiration occurred rapidly on addition of these supplements to soil. A single brief water washing of urediospores of Puccinia rubigo-vera or of conidia of Neurospora sp. extracted about 10% of the spore dry weight. Washed bacteria or Streptomyces spp., when incubated with fungus spores in absence of added nutrients, inhibited fungus spore germination, whereas sterile filtrates of bacteria were not inhibitory. The results indicate that fungus spores, by virtue of nutrients in their exudates, stimulate rapid activity of microbes in soil, and that the enhanced microbial activity causes inhibition of fungal spore germination.

The relationship of pteridine biosynthesis to the action of copper 8-hydroxyquinolate on fungal spores

A study has been made of the mechanism of inhibition of fungal spore germination by copper-8-hydroxyquinolate (copper oxinate). It has been found that pteridines and their possible precursors can antagonize the inhibitory action. Guanine, xanthine. and 2, 4, 5-triamino-6-oxypyrimidine are active antagonists of copper oxinate. Adenine and 4, 5-diamino-2, 6 dioxypyrimidine are inactive. Riboflavin and several pteridines were active. Copper oxinate and 4-aminofolic acid act synergistically in the inhibition of germination. It is proposed that copper oxinate can interfere with pteridine biosynthesis by interfering with the copper-mediated conversion of a purine precursor to 4, 5-diaminopyrimidine.