Search

Late leaf spot of groundnut is caused by the fungal pathogen of Cercosporidium personatum. Efforts to prevent this disease generally use synthetic fungicides that can cause environmental pollution. This study aims to identify the fungal pathogen of groundnut late leaf spot and study the antifungal effect of leaf extract of some plants for leaf spot intensity suppression. Late leaf spot pathogen was identified based on morphological characteristics of hyphae and conidia. The leaf extracts of butterfly pea (Clitoria ternatea), Mexican sunflower (Tithonia diversifolia), basil (Ocimum gratissimum), and sugar apple (Annona squamosa) at a concentration of 25% against C. personatum were evaluated in vitro based on growth inhibition. The growth and intensity of groundnut disease attacks were assessed for seven weeks by inoculating C. personatum and application of the leaf extracts. Results showed that the pathogen was identified as C. personatum with conidia characteristics of cylindrical to obclavate, short and slightly curved with four septa, and 35.75 × 7.11 µm in size. The percentage of inhibition of C. personatum in vitro reached 94.03% by leaf extract of C. ternatea, 88.56% by T. diversifolia, 87.20% by O. gratissimum, and 84.10% by A. squamosa. Treatment of C. ternatea increased plant height up to 12.85% and reduced the most optimal percentage of the infected leaves up to 61.53%. C. ternatea leaf extract was found to be the most effective extract to suppress C. personatum infection by 77.94%, while T. diversifolia, O. gratissimum, and A. squamosa reduced disease severity by 70.15%, 65.43%, and 57.76%, respectively.

Ganoderma boninense , the causative agent behind basal stem rot (BSR) disease in oil palm, instigated a pressing need for innovative and ecologically sustainable strategies to counter its impact. Biological control strategies, particularly employing bio-fungicides, have emerged as environmentally friendly alternatives for managing oil palm plant diseases. This study delved into harnessing the biocontrol potential of Indigenous bacterial isolate by investigating and evaluating its bioactive compounds of ethyl acetate extract with the capacity to suppress G. boninense growth in oil palm plants. Molecular identification was utilized to identify of bacterial isolate using 16S rRNA primers (5′- AGA GTT TGA TCC TGG CTC AG– 3′) and (5′- GGA TAC CTT GTT ACG ACT T– 3′). The agar well diffusion technique and scanning electron microscopy (SEM) were utilized to assess the inhibitory effects of bacterial ethyl acetate extract against G. boninense. A comprehensive analysis of the bacterial ethyl acetate extracts was conducted by gas chromatography - mass spectrometry (GC–MS). Molecular identification confirmed that the bacterial isolate was Bacterium strain BS1727. By employing SEM, the ethyl acetate extracts had influenced on G. boninense mycelial architecture. The exposure to the bacterial ethyl acetate extracts induced degradation and morphological distortion of the mycelial structure, serving as an indicator of its impact on the mycelium's structural modulation. Noteworthy, the spectrum of bioactive compounds was a subset of aromatic hydrocarbons, encompassing volatile organic compounds (VOCs). Based on GC–MS analysis, among the VOCs, acetic acid butyl ester and toluene showed the highest relative peak areas, 46.34 % for acetic acid butyl ester and 31.82 % for toluene, respectively. Ethylbenzene had a relative peak area of 5.4 %, 1,1,2-trichloroethane 4.41 %, and allyldimethyl (prop-1-ynyl) silane 3.17 %. The remaining compounds were 6-undecyl-5,6-dihydro-2H-pyran-2-one, 3-decen-5-one, 2-methyl-, and o-cymene, with the relative peak areas were below 1 %. These findings explained the inherent capacity of antifungal compounds as a viable strategy in inhibiting the growth of G. boninense. [ABSTRACT FROM AUTHOR]

Abstract Cytospora canker has become a devastating disease of apple species worldwide, and in severe cases, it may cause dieback of entire trees. The aim of this study was to characterize the diversity of cultivable bacteria from the wild apple microbiota and to determine their antifungal ability against the canker-causing pathogenic fungi Cytospora mali and C. parasitica. Five bacterial strains belonging to the species Bacillus amyloliquefaciens, B. atrophaeus, B. methylotrophicus, B. mojavensis, and Pseudomonas synxantha showed strong antagonistic effects against pathogenic fungi. Therefore, since the abovementioned Bacillus species produce known antifungal compounds, we characterized the antifungal compounds produced by Ps. synxantha. Bacteria grown on nutritional liquid medium were dehydrated, and the active compound from the crude extract was isolated and analysed via a range of chromatographic processes. High-performance liquid chromatography, mass spectrometry, and nuclear magnetic resonance analyses revealed a bioactive antifungal compound, phenazine-1-carboxylic acid (PCA). The minimum inhibitory concentration (MIC) demonstrated that PCA inhibited mycelial growth, with a MIC of 10 mg mL−1. The results suggested that PCA could be used as a potential compound to control C. mali and C. malicola, and it is a potential alternative for postharvest control of canker disease.

Late leaf spot of groundnuts is caused by the fungal pathogen Cercosporidium personatum. Efforts to prevent this disease generally use synthetic fungicides that can pollute the environment. This study aims to identify the fungal pathogen of groundnut late leaf spot and determine the antifungal effect of leaf extract from several plants on leaf spot disease suppression. Late leaf spot pathogen was identified based on hyphae and conidia morphological characteristics. Growth inhibition of leaf extracts from butterfly pea (Clitoria ternatea), Mexican sunflower (Tithonia diversifolia), basil (Ocimum gratissimum), and sugar apple (Annona squamosa) at aconcentration of 25%were tested against C. personatum in vitro. The growth and intensity of groundnut disease attackswere assessed for seven weeks by inoculating C. personatum and applied with several leaf extracts. Results showed that the pathogen was identified as C. personatum with conidia characteristics of cylindrical to obclavate, short and slightly curved with four septa, and 35.75 × 7.11 µm in size. The inhibition percentage of C. personatum in vitro reached 94.03% by leaf extract of C. ternatea, 88.56% by T. diversifolia, 87.20% by O. gratissimum, and 84.10% by A. squamosa. Treatment of C. ternatea increased plant height by up to 12.85% and showed the highest reduction of infected leaves by up to 61.53%. C. ternatea leaf extract was found to be the most effective leaf extract to suppress C. personatum infection by 77.94%, while T. diversifolia, O. gratissimum, and A. squamosa reduced disease severity by 70.15%, 65.43%, and 57.76%, respectively. [ABSTRACT FROM AUTHOR]

Plant pathogens are responsible for important damages to valuable crops causing important economic losses. Agrobiodiversity protection is crucial for the valorization of local varieties that could possess higher resistance to biotic and abiotic stress. At the beginning of germination, seeds are susceptible to pathogens attacks, thus they can release endogenous antimicrobial compounds of different natures in the spermosphere, to contrast proliferation of microorganisms. The work aimed at characterizing the maize of local variety Nostrano di Storo seed exudates secreted during the first phases of germination, to identify compounds active in the defense towards pathogens. Storo seed exudates were proven to inhibit F. verticilloides germination. In order to investigate the cause of the described effect, compositional profiling of the exudates was performed through NMR, lipidomic, and proteomic analyses. This study suggests an important role of microbial endophytic communities in the protection of the seed during the early phases of the germination process and their interplay with fatty acids released by the seeds, rather than a specific antifungal compound. The valorization of agronomically acceptable maize lines with pre-harvest enhanced resistances to pathogens contamination could lead, in the near future, to commercially available varieties potentially requiring more limited chemical protective treatments. [ABSTRACT FROM AUTHOR]

Here we report the discovery and identification of antibacterial substances from the secondary metabolites of a new strain Bacillus velezensis BA-26. The whole genome of B. velezensis BA-26 was sequenced. Its genome data were annotated, and four potentially unknown gene clusters and nine known secondary metabolite synthetic gene clusters were analyzed and excavated by antiSMASH software. Based on the predicted secondary metabolites from the genome of strain BA-26, the material identification of isolated and purified extracellular secondary metabolites was conducted in combination with mass spectrometry data. A total of 24 antifungal compounds were identified, namely, iturin and various fengycins. The minimum inhibitory concentration (MIC) of iturin to Botrytis cinerea was 62.50 µg·mL−1. The MICs of C14 fengycin A, C16 fengycin A and C18 fengycin A were 62.50, 31.25 and 0.49 µg·mL−1, respectively, indicating that the increase in the number of carbon atoms in side chain fatty acids of fengycin improves its biological activity. Two kinds of anti-disease fungal compounds from B. velezensis BA-26, namely, iturin and fengycin, were purified and identified; they were found to have antibacterial activities against common pathogenic fungi. Therefore, B. velezensis BA-26 may be potentially used as a biological control agent. This study enriches the genome information on B. velezensis, elucidates the active components of B. velezensis BA-26 antibacterial substances, and provides a useful reference for using strain BA-26 as a biological control agent. Supplemental data for this article is available online at https://doi.org/10.1080/13102818.2021.1934540 .

Bacillus siamensis LDR was tested for its potential as a biocontrol agent against the phytopathogenic fungi Curvularia lunata BM and Ganoderma sp. TB4. Fermentation of B. siamensis LDR for the production of antifungal compound was performed in modified Czapex- Dox broth using hanjeli (Coix lacryma-jobi L.) starch as carbon source. The Bacillus siamensis LDR inoculum was 105 CFU/ mL, and fermentation was conducted for up to 16 days. Antibiosis assay conducted to test the antifungal activity of filtrate medium. The results showed inhibition of C. lunata BM and Ganoderma sp. TB4 were 47.08% and 85.99%, respectively on 14th day of fermentation. Antifungal assay of the crude extract from filtrate medium revealed growth inhibition of C. lunata BM (60.70%) and Ganoderma sp. TB4 (65.25%). Thin layer chromatography of the crude extract revealed pink-colored spots indicative of lipopeptide compounds. Analysis of the crude extract by ultraperformance liquid chromatography-mass spectrometry was tentatively identified as iturin A, bacillomycin F, and surfactin. [ABSTRACT FROM AUTHOR]

Abstract Background “Bayoud” disease caused by Fusarium oxysporum f. sp. albedinis (Foa) poses a serious threat to date palm (Phoenix dactylifera L.) in Morocco. However, research studies performed to discover biological methods to control this disease remain limited. The present study has set objectives to determine antifungal activity of five plants extracts (Acacia cyanophylla, Cupressus atlantica, Eucalyptus torquata, Nerium oleander, and Schinus molle) against Foa and link this effect to their content in polyphenols and flavonoids as well as their antioxidant properties. Results Plant extracts showed significant differences (p < 0.05) regarding their antifungal activity. The extracts of E. torquata and C. atlantica showed the strongest antifungal effect resulting in the inhibition of mycelial growth, sporulation, and spore germination in a dose-dependent manner. In addition, there were significant differences among the examined plant extracts in respect to their total polyphenols (1.536–7.348 g GAE/100 g DW), flavonoids (0.986–5.759 g RE/100 g DW), and antioxidant properties measured by Trolox equivalent antioxidant capacity (TEAC) (7.47–38.97 mmol TE/100 g DW) and ferric-reducing antioxidant power (FRAP) assay (8.95–47.36 mmol TE/100 g DW). Moreover, the antifungal potential of plant extracts was found to be moderately to strongly correlated with their polyphenol and flavonoid contents as well as their antioxidant activity, implying that the effective inhibitory activity of these plant extracts is partly due to their richness in antioxidative secondary metabolites. Conclusion Our findings shed further light on plants as a-yet-untapped resource of bioactive compounds and constructed the foundation for the development of new biological approaches to best manage Bayoud disease.

The gut microflora of insects plays important roles throughout their lives. Different foods and geographic locations change gut bacterial communities. The invasive wood-borer Agrilus mali causes extensive mortality of wild apple, Malus sieversii , which is considered a progenitor of all cultivated apples, in Tianshan forests. Recent analysis showed that the gut microbiota of larvae collected from Tianshan forests showed rich bacterial diversity but the absence of fungal species. In this study, we explored the antagonistic ability of the gut bacteria to address this absence of fungi in the larval gut. The results demonstrated that the gut bacteria were able to selectively inhibit wild apple tree-associated fungi. Among them, Pseudomonas synxantha showed strong antagonistic ability, producing antifungal compounds. Using different analytical methods, such as column chromatography, mass spectrometry, HPLC, and NMR, an antifungal compound, phenazine-1-carboxylic acid (PCA), was identified. Activity of the compound was determined by the minimum inhibitory concentration method and electron microscopy. Moreover, our study showed that the gut bacteria could originate from noninfested apple microflora during infestation. Overall, the results showed that in newly invaded locations, A. mali larvae changed their gut microbiota and adopted new gut bacteria that prevented fungal colonization in the gut. [ABSTRACT FROM AUTHOR]

The gut microflora of insects plays important roles throughout their lives. Different foods and geographic locations change gut bacterial communities. The invasive wood-borer Agrilus mali causes extensive mortality of wild apple, Malus sieversii, which is considered a progenitor of all cultivated apples, in Tianshan forests. Recent analysis showed that the gut microbiota of larvae collected from Tianshan forests showed rich bacterial diversity but the absence of fungal species. In this study, we explored the antagonistic ability of the gut bacteria to address this absence of fungi in the larval gut. The results demonstrated that the gut bacteria were able to selectively inhibit wild apple tree-associated fungi. Among them, Pseudomonas synxantha showed strong antagonistic ability, producing antifungal compounds. Using different analytical methods, such as column chromatography, mass spectrometry, HPLC, and NMR, an antifungal compound, phenazine-1-carboxylic acid (PCA), was identified. Activity of the compound was determined by the minimum inhibitory concentration method and electron microscopy. Moreover, our study showed that the gut bacteria could originate from noninfested apple microflora during infestation. Overall, the results showed that in newly invaded locations, A. mali larvae changed their gut microbiota and adopted new gut bacteria that prevented fungal colonization in the gut.

In the search for antifungal agents from marine resources, we recently found that the culture filtrate of Trichoderma longibrachiatum SFC100166 effectively suppressed the development of tomato gray mold, rice blast, and tomato late blight. The culture filtrate was then successively extracted with ethyl acetate and n-butanol to identify the fungicidal metabolites. Consequently, a new compound, spirosorbicillinol D (1), and a new natural compound, 20,30 -dihydro-epoxysorbicillinol (2), together with 11 known compounds (3–13), were obtained from the solvent extracts. The chemical structures were determined by spectroscopic analyses and comparison with literature values. The results of the in vitro antifungal assay showed that of the tested fungal pathogens, Phytophthora infestans was the fungus most sensitive to the isolated compounds, with MIC values ranging from 6.3 to 400 µg/mL, except for trichotetronine (9) and trichodimerol (10). When tomato plants were treated with the representative compounds (4, 6, 7, and 11), bisvertinolone (6) strongly reduced the development of tomato late blight disease compared to the untreated control. Taken together, our results revealed that the culture filtrate of T. longibrachiatum SFC100166 and its metabolites could be useful sources for the development of new natural agents to control late blight caused by P. infestans. [ABSTRACT FROM AUTHOR]

Here we report the discovery and identification of antibacterial substances from the secondary metabolites of a new strain Bacillus velezensis BA-26. The whole genome of B. velezensis BA-26 was sequenced. Its genome data were annotated, and four potentially unknown gene clusters and nine known secondary metabolite synthetic gene clusters were analyzed and excavated by antiSMASH software. Based on the predicted secondary metabolites from the genome of strain BA-26, the material identification of isolated and purified extracellular secondary metabolites was conducted in combination with mass spectrometry data. A total of 24 antifungal compounds were identified, namely, iturin and various fengycins. The minimum inhibitory concentration (MIC) of iturin to Botrytis cinerea was 62.50 µg·mL−1. The MICs of C14 fengycin A, C16 fengycin A and C18 fengycin A were 62.50, 31.25 and 0.49 µg·mL−1, respectively, indicating that the increase in the number of carbon atoms in side chain fatty acids of fengycin improves its biological activity. Two kinds of anti-disease fungal compounds from B. velezensis BA-26, namely, iturin and fengycin, were purified and identified; they were found to have antibacterial activities against common pathogenic fungi. Therefore, B. velezensis BA-26 may be potentially used as a biological control agent. This study enriches the genome information on B. velezensis, elucidates the active components of B. velezensis BA-26 antibacterial substances, and provides a useful reference for using strain BA-26 as a biological control agent. Supplemental data for this article is available online at https://doi.org/10.1080/13102818.2021.1934540. [ABSTRACT FROM AUTHOR]

Information on microbial genome sequences is a powerful resource for accessing natural products with significant activities. We herein report the unveiling of lucensomycin production by Streptomyces achromogenes subsp. streptozoticus NBRC14001 based on the genome sequence of the strain. The genome sequence of strain NBRC14001 revealed the presence of a type I polyketide synthase gene cluster with similarities to a biosynthetic gene cluster for natamycin, which is a polyene macrolide antibiotic that exhibits antifungal activity. Therefore, we investigated whether strain NBRC14001 produces antifungal compound(s) and revealed that an extract from the strain inhibited the growth of Candida albicans. A HPLC analysis of a purified compound exhibiting antifungal activity against C. albicans showed that the compound differed from natamycin. Based on HR-ESI-MS spectrometry and a PubChem database search, the compound was predicted to be lucensomycin, which is a tetraene macrolide antibiotic, and this prediction was supported by the results of a MS/MS analysis. Furthermore, the type I polyketide synthase gene cluster in strain NBRC14001 corresponded well to lucesomycin biosynthetic gene cluster (lcm) in S. cyanogenus, which was very recently reported. Therefore, we concluded that the antifungal compound produced by strain NBRC14001 is lucensomycin.

Summary: Many types of yeast have been studied in the last few years as potential biocontrol agents against different phytopathogenic fungi. Their ability to control plant diseases is mainly through combined modes of action. Among them, antibiosis, competition for nutrients and niches, induction of systemic resistance in plants and mycoparasitism have been the most studied. In previous work, we have established that the epiphytic yeast Pseudozyma aphidis inhibits Botrytis cinerea through induced resistance and antibiosis. Here, we demonstrate that P. aphidis adheres to B. cinerea hyphae and competes with them for nutrients. We further show that the secreted antifungal compounds activate the production of reactive oxygen species and programmed cell death in B. cinerea mycelium. Finally, P. aphidis and its secreted compounds negatively affect B. cinerea hyphae, leading to morphological alterations, including hyphal curliness, vacuolization and branching, which presumably affects the colonization ability and infectivity of B. cinerea. This study demonstrates additional modes of action for P. aphidis and its antifungal compounds against the plant pathogen B. cinerea. [ABSTRACT FROM AUTHOR]

An antifungal compound 9, 10-dihydrophenanthrene - 2 - carboxylic acid was isolated from a marine derived bacterium Pseudomonas putida isolated from surface water samples of Karachi fish harbor coast line. The structure was explored using extensive ID- and 2D-NMR spectroscopic techniques. The compound was found to be active against fungal strains obtained from clinical samples whereas strong activity was noted against Candida albicans with a MIC value of 20μg/ml, as the purified compound showed promising anticandidal activity a multidisciplinary approach is needed to explore further this compound as potential pharmacological lead compound against Candida spp and will add in the global hunt for clinically functional antifungal agents. [ABSTRACT FROM AUTHOR]

Endophytic bacteria have been reported to produce metabolite as antifungal compound. This study was aimed to obtain endophytic bacteria which are able to produce metabolite to control Fusarium sp., a potential seedborne fungi on maize. Endophytic bacteria were screened by hypersensitive test on tobacco leaves and antagonistic test. Endophytic bacteria isolates with high growth inhibitor activity were selected and examined for their metabolite compound. Thre isolates, i.e. Lactobacillus sp. isolate EF14III, Pseudomonas sp. isolate ER1I, dan Aeromonas sp. isolate ER10I has the potential to inhibit Fusarium sp.. Metabolite compound of Pseudomonas sp. isolates ER1I was able to decrease the infection Fusarium sp. by 65.0% in blotter test and decreased infection of Fusarium sp. up to 59.5% and 60.5% in growing on test using water agar and sterile soil, respectively. Cyclohexanone with concentration of 9.68% produced by Pseudomonas sp. isolat ERI1 may play a role as antifungal compound.

The release of pharmaceuticals into environment has become an increasing concern in recent years. Fungi are part of the microbial flora of many animals, humans and foodstuffs, and some species can cause disease. An antimycotic or antifungal product is one that is used in the treatment of fungal infections. Even at low concentrations, antifungals exert an action against micro-organisms and exhibit selective toxicity towards them. The use of antimicrobials selects for resistant populations of micro-organisms. Development of resistance to antifungals is an increasing problem in veterinary and human medicine.

In this study, we investigated the antifungal activity and mechanism of action of (+)-pinoresinol, a biphenolic compound isolated from the herb Sambucus williamsii,used in traditional medicine. (+)-Pinoresinol displays potent antifungal properties without hemolytic effects on human erythrocytes. To understand the antifungal mechanism of (+)-pinoresinol, we conducted fluorescence experiments on the human pathogen Candida albicans. Fluorescence analysis using 1,6-diphenyl-1,3,5-hexatriene (DPH) indicated that the (+)-pinoresinol caused damage to the fungal plasma membrane. This result was confirmed by using rhodamine-labeled giant unilamellar vesicle (GUV) experiments. Therefore, the present study indicates that (+)-pinoresinol possesses fungicidal activities and therapeutic potential as an antifungal agent for the treatment of fungal infectious diseases in humans.

Pseudomonas fluorescens FD6 has been shown to possess many beneficial traits involved in the biocontrol of fungal plant pathogens, such as Botrytis cinerea and Monilinia fructicola . Vfr (virulence factor regulator) a highly conserved global regulator of gram-negative bacteria, such as the human pathogen Pseudomonas aeruginosa , is required for the expression of many important virulence traits. The role of Vfr in the regulation of biocontrol traits, such as the production of antibiotics to control fungal pathogens by antagonistic bacteria, has not been elucidated. This study investigated the effect of a vfr mutant derived from P. fluorescens FD6 to better understand the regulation of some important biocontrol traits associated with the bacterium. Biochemical studies indicated that the production of the antibiotics 2,4-diacetylphloroglucinol, pyrrolnitrin and pyoluteorin, was markedly enhanced in the vfr mutant. The vfr mutation also increased biofilm production, swimming motility and the expression of exopolysaccharide-associated gene ( pelA , pslA and pslB ) transcripts, but reduced protease production. Wheat rhizosphere and root tip colonization by the vfr mutant was higher than that by the wild type at 7 and 21 days after inoculation. These findings demonstrate that Vfr modulates the expression of several key traits and the production of important antibiotics involved in the biocontrol potential of P. fluorescens FD6. [ABSTRACT FROM AUTHOR]

In agriculture, biocontrol agents have been emerged as safe alternative to chemical pesticides where Streptomyces spp. and their metabolites constitute a great potential for their exploration as potent agents for controlling various fungal phytopathogens. The present study reports an antifungal compound purified from Streptomyces hydrogenans strain DH16, a soil isolate, using silica gel chromatography and semi preparative HPLC. The compound was characterized using various spectroscopic techniques (IR, ¹H and 13C NMR) and named 10-(2,2-dimethyl-cyclohexyl)-6,9-dihydroxy-4,9-dimethyl-dec-2-enoic acid methyl ester (SH2). Compound (SH2) showed significant inhibitory activity against fungal phytopathogens and resulted in severe morphological aberrations in their structure. Minimal inhibitory and minimal fungicidal concentrations of the compound ranged from 6.25 to 25 µg/ml and 25 to 50 µg/ml, respectively. In vivo evaluation of the compound showed strong control efficacy against Alternaria brassicicola, a seed borne pathogen, on radish seeds. In comparison to mancozeb and carbendazim, the compound was more effective in controlling damping off disease. Additionally, it promoted plant growth with increased rate of seed germination, and displayed no phytotoxicity. The compound retained its antifungal activity after its exposure to temperature of 100°C and sunlight for 1 h. Furthermore, the compound (SH2) when tested for its biosafety was found to be non-cytotoxic, and non-mutagenic against Salmonella typhimurium TA98 and TA100 strains. This compound from S. hydrogenans strain DH16 has not been reported earlier, so this new compound can be developed as an ideal safe and superior biofungicide for the control of various fungal plant diseases. [ABSTRACT FROM AUTHOR]

Effects of anthocyanins from purple sweet potato (APSP) against the fungal growth of Geotrichum candidum and Candida albicans were assessed. Response surface methodology was applied for optimization of proportions of sodium benzoate, potassium sorbate, and APSP. Optimum concentrations against G. candidum were 0.300 mg/mL of sodium benzoate, 0.290mg/mL of potassium sorbate, and 13.9mg/mL of APSP. Optimum concentrations against C. albicans were 0.380 mg/mL of sodium benzoate, 0.240 mg/mL of potassium sorbate, and 3.56 mg/mL of APSP. APSP exhibited enhanced antifungal properties in the presence of food preservatives. [ABSTRACT FROM AUTHOR]

In the present study, Lactobacillus pentosus, L. plantarum, L. fermentum, L. brevis, L. paraplantarum, L. buchneri, and L. acidipiscis, which are strains capable of producing antifungal metabolites against food-spoilage fungi, were isolated and identified based on 16S rRNA gene sequencing from different traditional pickles. L. brevis P68 exhibited significant antifungal activity, and it's in vitro antioxidant and probiotic properties were investigated. The antifungal compound was characterized based on C nuclear magnetic resonance (NMR), H NMR, infrared, and mass spectral data. The minimum inhibitory concentration (MIC) of the compounds was assessed using the broth micro-dilution technique. The MIC of the compounds against Penicillium chrysogenum and P. roqueforti was 2.5 mg mL and that against Gibberella moniliformis and Aspergillus clavatus was 5.0 mg mL. In addition, the HO (1.0 mM) hydroxyl radical, and DPPH scavenging activity inhibition rates were 32.76 and 48.63 %, respectively, and the activities toward the glutathione peroxidase and superoxide dismutase enzymes were high. This strain tolerated low pH and bile salt, exhibited bile salt hydrolase and extracellular enzyme activities, and was sensitive to common antibiotics with high hydrophobicity. This study revealed that the antifungal, antioxidant, and probiotic properties of L. brevis P68 confirmed its application to the food industry. [ABSTRACT FROM AUTHOR]

Pseudomonas aeruginosa PNA1, isolated from the rhizosphere of chickpea in India, suppressed Fusarium wilt of chickpea, caused by Fusarium oxysporum f. sp. ciceris, and Pythium damping-off of bean, caused by Pythium splendens. When grown in culture, PNA1 produced the phenazine antibiotics phenazine-1-carboxylic acid and oxychloraphine, and inhibited mycelial growth of F. oxysporum f. sp. ciceris, P. splendens, and certain other phytopathogenic fungi. Two mutants (FM29 and FM13) deficient in phenazine production were obtained following transposon mutagenesis of PNA1. The transposon in the genome of FM29 was localized to phnA, which is thought to encode a subunit of anthranilate synthase II involved in the phenazine biosynthesis. The FM13 mutation was complemented by trpC, which encodes indole glycerol phosphate synthase in the tryptophan biosynthesis pathway; consequently, FM13 could not grow on a minimal medium in the absence of tryptophan. Neither FM29 nor FM13 suppressed Fusarium wilt of chickpea to the level achieved by the wild-type strain, indicating that phenazine production contributed to the biocontrol of this disease by P. aeruginosa PNA1. FM29 was also less effective than the phenazine-producing parental strain in biological control of Pythium damping-off of bean, but FM13 was as effective as the parental strain in suppressing this disease. Anthranilate, an intermediate in the tryptophan biosynthesis pathway, suppressed mycelial growth of Pythium spp. in culture and Pythium damping-off of bean and lettuce. Anthranilate, excreted by FM13 as a consequence of the trpC mutation, may have contributed to the suppression of Pythium damping-off by the mutant.

Background Green and blue mold decay, caused by Penicillium digitatum and P. italicum, respectively, are important postharvest diseases of citrus. Biocontrol by microbes is an alternative to synthetic fungicide application. In this study, the antagonistic yeast strain Kloeckera apiculata 34-9 was used to investigate the action mechanisms involved in the biocontrol of postharvest diseases. Results An antifungal substance, 2-phenylethanol (PEA), was isolated from K. apiculata and demonstrated to have antimicrobial activity against selected phytopathogenic fungi. Experiments on P. italicum cells identified the mitochondria and the nucleus as particularly sensitive to inhibition. Regulation of P. italicum gene expression was investigated using RNA-Seq. PEA up-regulated genes involved with the peroxisome, regulation of autophagy, phosphatidylinositol signaling system, protein processing in endoplasmic reticulum, fatty acid metabolism, and inhibited ribosome, RNA polymerase, DNA replication, amino acid biosynthesis, aminoacyl-tRNA biosynthesis and cell cycle. Inhibitory responses revealed by RNA-Seq suggest that PEA might compete for attachment on the active site of phenylalanyltRNA synthetase (PheRS). Conclusion This study provided new insight on the mode of action of biocontrol yeast agents in controlling postharvest pathogenic fungi. [ABSTRACT FROM AUTHOR]

This study aimed to describe the diversity of antifungal lactic acid bacteria (LAB) in popular traditional Korean fermented food. A total of 22 LAB strains was selected and subjected to a monophasic identical approach using 16S rRNA gene sequence analysis. Antifungal LAB associated with fermented food was identified as Lactobacillus plantarum (9), Lactobacillus graminis (5), Lactobacillus pentosus (4), Lactobacillus sakei (2), Lactobacillus paraplantarum (1), and Leuconostoc mesenteroides subsp. mesenteroides (1). Novel Lactobacillus plantarum strain K46 exhibited comparatively better antifungal activity against several spoilage fungi, and was deposited in the Korean Collection for Type Cultures (KACC91758P). Antifungal substances from the spent medium in which K46 was cultivated were extracted with ethyl acetate. Antifungal activity was assessed using the broth micro dilution technique. Compounds were characterized based on infrared, C nuclear magnetic resonance (NMR), and H NMR spectral data. The minimum inhibitory concentration (MIC) of the compounds against Aspergillus clavatus, Aspergillus oryzae, Penicillium chrysogenum and Penicillium roqueforti was 2.5 mg/mL and that against Aspergillus fumigatus, Aspergillus niger, Curvularia lunata and Gibberella moniliformis was 5.0 mg/mL. K46 was able to survive gastrointestinal conditions simulating the stomach and the duodenum passage with the highest percentage of hydrophobicity. In addition, its resistance to hydrogen peroxide and highest hydroxyl radical and 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activities, with inhibition rates of 43.53 % and 56.88 %, respectively, were to its advantage. An antimicrobial susceptibility pattern was an intrinsic feature of this strain, thus consumption does not represent a health risk to humans. The results showed the potential of K46 strain as an antifungal, probiotic and antioxidant culture, and hence it was determined to be suitable for application in functional foods. [ABSTRACT FROM AUTHOR]

Abstract: The morbidity, mortality and economic burden associated with fungal infections, together with the emergence of fungal strains resistant to current antimicrobial agents, necessitate broadening our understanding of fungal pathogenesis and discovering new agents to treat these infections. Using invertebrate hosts, especially the nematode Caenorhabditis elegans and the model insects Drosophila melanogaster and Galleria mellonella, could help achieve these goals. The evolutionary conservation of several aspects of the innate immune response between invertebrates and mammals makes the use of these simple hosts an effective and fast screening method for identifying fungal virulence factors and testing potential antifungal compounds. The purpose of this review is to compare several model hosts that have been used in experimental mycology to-date and to describe their different characteristics and contribution to the study of fungal virulence and the detection of compounds with antifungal properties. This article is part of a Special Issue entitled: Animal Models of Disease. [Copyright &y& Elsevier]

Abstract: The aims of this study were to investigate the antifungal activity as a bioactive property of dihydrodehydrodiconiferyl alcohol 9′-O-β-d-glucoside (DDDC9G) and the mode of action(s) involved in its effect. Antifungal susceptibility testing showed that DDDC9G possessed potent antifungal activities toward various fungal strains with almost no hemolytic effect. To understand the antifungal mechanism(s) of DDDC9G, we conducted the following experiments in this study using Candida albicans. Fluorescence experiments using the probes, 1, 6-diphenyl-1, 3, 5-hexatriene (DPH) and propidium iodide suggested that DDDC9G perturbed the fungal plasma membrane. Consecutively, the analysis of the transmembrane electrical potential (ΔΨ) with 3, 3′-dipropylthiadicarbocyanine iodide [DiSC3(5)] and bis-(1, 3-dibutylbarbituric acid) trimethine oxonol [DiBAC4(3)] indicated that DDDC9G induced membrane-depolarization. Furthermore, model membrane studies were performed with rhodamine-labeled giant unilamellar vesicles (GUVs), calcein encapsulating large unilamellar vesicles (LUVs), and FITC-dextran (FD) loaded LUVs. These results demonstrated that the antifungal effects of DDDC9G upon the fungal plasma membrane were through the formation of pores with the radii between 0.74nm and 1.4nm. Finally, in three dimensional (3D) flow cytometric contour plots, a reduced cell size was observed as a result of osmolarity changes from DDDC9G-induced structural and functional membrane damages. Therefore, the present study suggests that DDDC9G exerts its antifungal effect by damaging the membrane through pore formation in the fungal plasma membrane. [Copyright &y& Elsevier]

Information on microbial genome sequences is a powerful resource for accessing natural products with significant activities. We herein report the unveiling of lucensomycin production by Streptomyces achromogenes subsp. streptozoticus NBRC14001 based on the genome sequence of the strain. The genome sequence of strain NBRC14001 revealed the presence of a type I polyketide synthase gene cluster with similarities to a biosynthetic gene cluster for natamycin, which is a polyene macrolide antibiotic that exhibits antifungal activity. Therefore, we investigated whether strain NBRC14001 produces antifungal compound(s) and revealed that an extract from the strain inhibited the growth of Candida albicans. A HPLC analysis of a purified compound exhibiting antifungal activity against C. albicans showed that the compound differed from natamycin. Based on HR-ESI-MS spectrometry and a PubChem database search, the compound was predicted to be lucensomycin, which is a tetraene macrolide antibiotic, and this prediction was supported by the results of a MS/MS analysis. Furthermore, the type I polyketide synthase gene cluster in strain NBRC14001 corresponded well to lucesomycin biosynthetic gene cluster (lcm) in S. cyanogenus, which was very recently reported. Therefore, we concluded that the antifungal compound produced by strain NBRC14001 is lucensomycin. [ABSTRACT FROM AUTHOR]

Abstract: Pseudomonas sp. M18 can suppress certain soil-borne phytopathogenic fungi by producing two antibiotics, pyoluteorin (Plt) and phenazine-1-carboxylic acid (PCA). pltR encodes an LysR-type transcriptional activator required for expression of divergently transcribed Plt biosynthetic genes. Here we provide evidence that Plt biosynthesis is negatively regulated by the quorum-sensing (QS) signal molecule (N-acyl homoserine lactone, AHL) synthase gene lasI and positively regulated by the orphan LuxR-type regulatory gene vqsR. pltR expression is modulated by four important global regulators including the two-component response regulatory gene gacA, the RNA-binding repressor RsmA, and the QS signal molecule synthase genes lasI and rhlI. pltR translation was almost completely inhibited in the gacA mutant M18G when compared with that in the wild-type strain of M18. We also observed significant enhancement of pltR translation in the rsmA mutant compared with wild-type strain M18. Moreover, mutation in lasI or rhlI gave rise to a significantly elevated level of pltR transcription in strain M18. However, no obvious difference was observed in pltR expression between the vqsR mutant and the wild-type of strain M18. These results highlight the fact that PltR likely at least partly plays an important mediator role in Gac/Rsm and the Las/Rhl regulatory pathways involved in Plt biosynthesis. [Copyright &y& Elsevier]

A Bacillus strain, denoted as PY-1, was isolated from the vascular bundle of cotton. Biochemical, physiological and 16S rDNA sequence analysis proved that it should belong to Bacillus subtilis. The PY-1 strain showed strong ability against many common plant fungal pathogens in vitro. The antibiotics produced by this strain were stable in neutral and basic conditions, and not sensitive to high temperature. From the culture broth of PY-1 strain, five antifungal compounds were isolated by acidic precipitation, methanol extraction, gel filtration and reverse-phase HPLC. Advanced identification was performed by mass spectrometry and nuclear magnetic resonance spectroscopy. These five antifungal compounds were proved to be the isomers of iturin A: A2, A3, A4, A6 and A7. In fast atom bombardment mass spectrometry/mass spectrometry collision-induced dissociation spectra, fragmentation ions from two prior linear acylium ions were observed, and the prior ion, Tyr-Asn-Gln-Pro-Asn-Ser-βAA-Asn-CO+, was first reported. Edited by Ming-Hua XU [ABSTRACT FROM AUTHOR]

Information on microbial genome sequences is a powerful resource for accessing natural products with significant activities. We herein report the unveiling of lucensomycin production by Streptomyces achromogenes subsp. streptozoticus NBRC14001 based on the genome sequence of the strain. The genome sequence of strain NBRC14001 revealed the presence of a type I polyketide synthase gene cluster with similarities to a biosynthetic gene cluster for natamycin, which is a polyene macrolide antibiotic that exhibits antifungal activity. Therefore, we investigated whether strain NBRC14001 produces antifungal compound(s) and revealed that an extract from the strain inhibited the growth of Candida albicans . A HPLC analysis of a purified compound exhibiting antifungal activity against C. albicans showed that the compound differed from natamycin. Based on HR-ESI-MS spectrometry and a PubChem database search, the compound was predicted to be lucensomycin, which is a tetraene macrolide antibiotic, and this prediction was supported by the results of a MS/MS analysis. Furthermore, the type I polyketide synthase gene cluster in strain NBRC14001 corresponded well to lucesomycin biosynthetic gene cluster ( lcm ) in S. cyanogenus , which was very recently reported. Therefore, we concluded that the antifungal compound produced by strain NBRC14001 is lucensomycin.

Pyridine nucleotides such as a nicotinamide adenine dinucleotide (NAD) are known as plant defense activators. We previously reported that nicotinamide mononucleotide (NMN) enhanced disease resistance against fungal pathogen Fusarium graminearum in barley and Arabidopsis. In this study, we reveal that the pretreatment of nicotinamide (NIM), which does not contain nucleotides, effectively suppresses disease development of Fusarium Head Blight (FHB) in wheat plants. Correspondingly, deoxynivalenol (DON) mycotoxin accumulation was also significantly decreased by NIM pretreatment. A metabolome analysis showed that several antioxidant and antifungal compounds such as trigonelline were significantly accumulated in the NIM-pretreated spikes after inoculation of F. graminearum. In addition, some metabolites involved in the DNA hypomethylation were accumulated in the NIM-pretreated spikes. On the other hand, fungal metabolites DON and ergosterol peroxide were significantly reduced by the NIM pretreatment. Since NIM is relative stable and inexpensive compared with NMN and NAD, it may be more useful for the control of symptoms of FHB and DON accumulation in wheat and other crops. [ABSTRACT FROM AUTHOR]

The production of 4-hydroxyphenyllactic acid (4-HO-PLA), a novel antifungal compound, was studied in Lactobacillus sp. SK007 growth. When grown in MRS broth, the strain could produce 75 μg/ml HO-4-PLA, which was the highest reported so far. Tyrosine and 4-hydroxyphenylpyruvic acid (HO-4-PPA) supplements during fermentation could both increase the HO-4-PLA production yield, and the effect of HO-4-PPA on HO-4-PLA production was remarkably better than that of tyrosine. Using HO-4-PPA as substrate could effectively produce HO-4-PLA, which reached 1.26 mg/ml. [Copyright &y& Elsevier]

In the search for antifungal agents from marine resources, we recently found that the culture filtrate of Trichoderma longibrachiatum SFC100166 effectively suppressed the development of tomato gray mold, rice blast, and tomato late blight. The culture filtrate was then successively extracted with ethyl acetate and n-butanol to identify the fungicidal metabolites. Consequently, a new compound, spirosorbicillinol D ( 1 ), and a new natural compound, 2',3'-dihydro-epoxysorbicillinol ( 2 ), together with 11 known compounds ( 3 - 13 ), were obtained from the solvent extracts. The chemical structures were determined by spectroscopic analyses and comparison with literature values. The results of the in vitro antifungal assay showed that of the tested fungal pathogens, Phytophthora infestans was the fungus most sensitive to the isolated compounds, with MIC values ranging from 6.3 to 400 µg/mL, except for trichotetronine ( 9 ) and trichodimerol ( 10 ). When tomato plants were treated with the representative compounds ( 4 , 6 , 7 , and 11 ), bisvertinolone ( 6 ) strongly reduced the development of tomato late blight disease compared to the untreated control. Taken together, our results revealed that the culture filtrate of T. longibrachiatum SFC100166 and its metabolites could be useful sources for the development of new natural agents to control late blight caused by P. infestans .