Solaniol, a toxic metabolite of Fusarium solani

The Outstanding Chemodiversity of Marine-Derived Talaromyces

Fungi in the genus Talaromyces occur in every environment in both terrestrial and marine contexts, where they have been quite frequently found in association with plants and animals. The relationships of symbiotic fungi with their hosts are often mediated by bioactive secondary metabolites, and Talaromyces species represent a prolific source of these compounds. This review highlights the biosynthetic potential of marine-derived Talaromyces strains, using accounts from the literature published since 2016. Over 500 secondary metabolites were extracted from axenic cultures of these isolates and about 45% of them were identified as new products, representing a various assortment of chemical classes such as alkaloids, meroterpenoids, isocoumarins, anthraquinones, xanthones, phenalenones, benzofurans, azaphilones, and other polyketides. This impressive chemodiversity and the broad range of biological properties that have been disclosed in preliminary assays qualify these fungi as a valuable source of products to be exploited for manifold biotechnological applications.

4-O-Glucosylation of Trichothecenes by Fusarium Species: A Phase II Xenobiotic Metabolism for t-Type Trichothecene Producers

The t-type trichothecene producers Fusarium sporotrichioides and Fusarium graminearum protect themselves against their own mycotoxins by acetylating the C-3 hydroxy group with Tri101p acetylase. To understand the mechanism by which they deal with exogenously added d-type trichothecenes, the Δtri5 mutants expressing all but the first trichothecene pathway enzymes were fed with trichodermol (TDmol), trichothecolone (TCC), 8-deoxytrichothecin, and trichothecin. LC-MS/MS and NMR analyses showed that these C-3 unoxygenated trichothecenes were conjugated with glucose at C-4 by α-glucosidic linkage. As t-type trichothecenes are readily incorporated into the biosynthetic pathway following the C-3 acetylation, the mycotoxins were fed to the ΔFgtri5ΔFgtri101 mutant to examine their fate. LC-MS/MS and NMR analyses demonstrated that the mutant conjugated glucose at C-4 of HT-2 toxin (HT-2) by α-glucosidic linkage, while the ΔFgtri5 mutant metabolized HT-2 to 3-acetyl HT-2 toxin and T-2 toxin. The 4-O-glucosylation of exogenously added t-type trichothecenes appears to be a general response of the ΔFgtri5ΔFgtri101 mutant, as nivalenol and its acetylated derivatives appeared to be conjugated with hexose to some extent. The toxicities of 4-O-glucosides of TDmol, TCC, and HT-2 were much weaker than their corresponding aglycons, suggesting that 4-O-glucosylation serves as a phase II xenobiotic metabolism for t-type trichothecene producers.

Napthoquinones from Neocosmospora sp.-Antibiotic Activity against Acidovorax citrulli, the Causative Agent of Bacterial Fruit Blotch in Watermelon and Melon

Bacterial fruit blotch (BFB) is a bacterial disease that devastates Cucurbitaceae crops worldwide, causing significant economic losses. Currently, there is no means to treat or control the disease. This study focused on exploring the antibacterial properties of endophytic fungi against Acidovorax citrulli (Aac), the causative agent of BFB. Based on disc diffusion, time kill and MIC microdilution broth assays, four endophytes showed promise in controlling Aac. Nonetheless, only one strain, Neocosmospora sp. MFLUCC 17-0253, reduced the severity of disease on watermelon and melon seedlings up to 80%. Structure analysis revealed production of several compounds by the fungus. Three of these secondary metabolites, including mixture of 2-methoxy-6-methyl-7-acetonyl-8-hydroxy-1,4-maphthalenedione and 5,8-dihydroxy-7-acetonyl-1,4-naphthalenedione, anhydrojavanicin, and fusarnaphthoquinones B exhibited antagonistic activity against Aac. The chemical profile data in planta experiment analyzed by LC-Q/TOF-MS suggested successful colonization of endophytic fungi in their host plant and different metabolic profiles between treated and untreated seedling. Biofilm assay also demonstrated that secondary metabolites of Neocosmospora sp. MFLUCC 17-0253 significantly inhibited biofilm development of Aac. To the best of our knowledge, secondary metabolites that provide significant growth inhibition of Aac are reported for the first time. Thus, Neocosmospora sp. MFLUCC 17-0253 possesses high potential as a biocontrol agent for BFB disease.

Effect of Medium pH and Light on Quinidine Production in Cinchona calisaya Wedd. Endophytic Fungi

Objectives

Quinidine has pharmaceutical importance as an antimalarial, antiarrhythmia, antimicrobial, anticancer, antioxidant, astringent, and bitter flavoring agent. Quinidine is in high demand, yet its production from the bark of the quina tree (Cinchona calisaya) is limited. Quinidine production from quina tree fungal endophytes, namely Aspergillus sydowii, Diaporthe sp., Diaporthe lithicola, Fusarium oxysporum, and F. solani is lower than the quinidine content of the tree bark. This study attempted to increase quinidine production from these fungi. This research aimed to determine the optimum culture conditions for quinidine production from endophytic fungi.

Materials and Methods

Quinidine was produced by in vitro culturing of the fungal endophytes in potato dextrose broth (PDB) medium under different culture conditions, i.e., a combination of an initial medium pH of 6.2 or 6.8, with or without light, in a static condition for 21 days of incubation at room temperature. Production under natural daylight in PDB medium without pH modification was used as the control. At the end of the incubation period, the mycelial mass was separated from the filtrate. The dried biomass and chloroform-extracted filtrate were weighed. Quinidine in the extract was analyzed qualitatively and quantitatively using high-performance liquid chromatograph.

Results

Quinidine production was affected by both light and the initial pH of the medium, depending on the fungal strain used. A significant increment in quinidine production, approximately 1.1-9.3-fold relative to its respective control was obtained from all fungi under their optimum conditions. Quinidine production in most of the fungi was significantly correlated with their biomass production but not with their extract production. Of those five fungi, F. solani that was cultured in PDB medium with an initial pH of 6.2 and incubated under continuous light produced the highest concentration of quinidine with low biomass.

Conclusion

The quinidine production of all fungal endophytes studied was affected by the culture conditions. F. solani is the most promising fungus for use as a quinidine production agent.

Back to the roots: a reappraisal of Neocosmospora

The genus Neocosmospora (Fusarium solani species complex) contains saprobes, plant endophytes and pathogens of major economic significance as well as opportunistic animal pathogens. Advances in biological and phylogenetic species recognition revealed a rich species diversity which has largely remained understudied. Most of the currently recognised species lack formal descriptions and Latin names, while the taxonomic utility of old names is hampered by the lack of nomenclatural type specimens. Therefore, to stabilise the taxonomy and nomenclature of these important taxa, we examined type specimens and representative cultures of several old names by means of morphology and phylogenetic analyses based on rDNA (ITS and LSU), rpb2 and tef1 sequences. Sixty-eight species are accepted in Neocosmospora, 29 of them described herein as new; while 13 new combinations are made. Eleven additional phylogenetic species are recognized, but remain as yet undescribed. Lectotypes are proposed for eight species, seven species are epitypified and two species are neotypified. Notes on an additional 17 doubtful or excluded taxa are provided.

Isolation and characterization of a cytotoxic metabolite of Talaromyces bacillosporus

A cytotoxic metabolite, talarotoxin, was isolated from a fungus, Talaromyces bacillosporus IFO 8397, cultured on rice. The structure of the toxin was elucidated and found to contain a pyrrolizidinedione connected with a trans delta 1-octalin through a conjugated triene.

Comparative yields of T-2 toxin and related trichothecenes from five toxicologically important strains of Fusarium sporotrichioides

The range and comparative yields of T-2 toxin and related trichothecenes from five toxicologically important strains of Fusarium sporotrichioides, i.e., NRRL 3299, NRRL 3510, M-1-1, HPB 071178-13, and F-38, were determined. Lyophilized cultures of the five strains maintained in the International Toxic Fusarium Reference Collection were used to inoculate autoclaved corn kernels. Corn cultures were incubated at 15 degrees C for 21 days and analyzed for trichothecenes by thin-layer chromatography and capillary gas chromatography. All five strains produced T-2 toxin, HT-2 toxin, T-2 triol, and neosolaniol. Two strains also produced T-2 tetraol, and two others produced diacetoxyscirpenol. The highest producer of T-2 toxin (1,300 mg/kg), HT-2 toxin (200 mg/kg), T-2 triol (1.9 mg/kg), and neosolaniol (170 mg/kg) was NRRL 3510, which was originally isolated from millet associated with outbreaks of alimentary toxic aleukia in the USSR. The second highest producer of T-2 toxin (930 mg/kg) was NRRL 3299. The other three strains produced T-2 toxin at levels ranging from 130 to 660 mg/kg. Thus, the five strains differed considerably in the amounts of T-2 toxin and other trichothecenes produced under identical laboratory conditions. These strains are being maintained under optimal conditions for the preservation of Fusarium cultures and are available from the Fusarium Research Center, The Pennsylvania State University, University Park.

Actual situation in Fusarium taxonomy

The importance of choosing the proper systematic system in Fusarium taxonomy is stated and a comparative listing of synonyms of the sections Sporotrichiella, Roseum, Liseola, Discolor, Gibbosum, Martiella, as used by various authors in three monographs, is given (2, 4, 9).

Isolation and characterization of two new trichothecenes from Fusarium sporotrichioides strain M-1-1

Two new trichothecenes were isolated along with T-2 toxin, neosolaniol, and HT-2 toxin from the culture filtrate of Fusarium sporotrichioides strain M-1-1. The structures of the new toxins were characterized to be 4 beta, 8 alpha-diacetoxy-12,13-epoxytrichothec-9-ene-3 alpha, 15-diol (designated NT-1) and 4 beta-acetoxy-12,13-epoxy-trichothec-9-ene-3 alpha,8 alpha,15-triol (designated NT-2).

Mycotoxicosis produced in rats by cultural products of an isolate of Aspergillus ochraceus

The toxicity of an isolate of Aspergillus ochraceus was examined in weanling male Sprague-Dawley rats fed diets containing a rice culture or fungal mat of the organism for 5 wk. The ground rice culture was mixed with a commercial purified diet at concentrations of 5, 7·5 and 10% and the fungal mat at concentrations of 1, 2 and 3%. In groups fed the rice-culture diets, weight gains were reduced and all the rats in the group fed the 10% diet died. Rats fed fungal-mat diets showed a marked reduction in weight gain, and the death rate was high (about 83%) in groups fed the 2 or 3% diet. Gross lesions found in groups fed either type of diet included focal necrosis in the liver, greenish discoloration of the kidneys, gastric ulceration, ulceration of the scrotal epidermis and corneal opacity. Histological changes in the liver included necrosis of the epithelium of biliary ducts, periductal oedema, pericholangitis, periductal fibrosis and disseminated focal hepatocellular necrosis. Necrosis of epithelium occurred also in the extraheptic ducts and was accompanied by an interstitial pancreatitis in certain rats. Foci of leucocytes and macrophages were found in the dermis of the scrotum and in the epididymal adipose connective tissue. Ulceration of the epidermis occurred late in the sequence of scrotal changes. Ocular lesions comprised corneal oedema, interstitital keratitis, iridocyclitis and hypopyon. Renal lesions consisted of tubular necrosis and hyaline and biliary casts within convoluted tubules.

Distribution of zearalenone-producing Fusarium species in Japan

One hundred sixty-six isolates of Fusarium spp. from domestic cereal grains, feed, and other sources were examined for their ability to produce zearalenone on autoclaved moist rice grains. They belonged to the following species (number of producers/number tested): F. roseum (9/28), F. roseum (Culmorum) (3/4), F. roseum (Gibbosum) (2/5), F. roseum (Avenaceum) (1/2), F. roseum (Scirpi) (0/1), F. tricinctum (1/4), F. tricinctum (Sporotrichiella) (0/7), F. lateritium (1/1), F. episphaeria (0/2), F. moniliforme (0/3), F. oxysporum (0/12), F. rigidiusculum (0/4), F. solani (0/4), F. splendens (0/1), F. nivale (0/2), and Fusarium spp. (15/86). Zearalenone was isolated from molded rice by ethanol extraction and purified by column chromatography. Selected isolates of F. roseum M-3-2 and F. roseum (Gibbosum) A-O-2 produced 50 to 100 mg of zearalenone per kg of rice. Increased yields (250 to 407 mg/kg of rice) were obtained by F. roseum M-3-2 when the substrate was supplemented with 1% peptone.

Biological and chemical detection of trichothecene mycotoxins of Fusarium species

The procedure for biological and chemical detection of trichothecene-type mycotoxins and its application to the screening of Fusarium for toxic strains were described.

Severe oral lesions in chickens caused by ingestion of dietary fusariotoxin T-2

Fusariotoxin T-2 is a mycotoxin produced by Fusarium tricinctum which was implicated in moldy corn toxicosis of farm animals. Graded concentrations of dietary fusariotoxin T-2 (0, 1, 2, 4, 8, and 16 mug/g, respectively) were given to groups of 40 chickens. Raised yellowish-white lesions on the mouth parts were produced by all concentrations, and the size of the lesions was dose-related. The growth rate was reduced significantly (P < 0.05) by concentrations of 4, 8, and 16 mug/g. The mouth fluid of the affected birds contained greatly increased numbers of bacteria, including Staphylococcus epidermidis and Escherichia coli, which proved avirulent when inoculated into scarified tissue of control birds. Microscopy examinations of the lesions revealed a fibrinous surface layer, intermediate layers containing invaginations filled with rods and cocci, and a heavy infiltration of the underlying tissues with granular leukocytes. These data suggest that the role of fusariotoxin T-2 in field cases of moldy corn toxicosis should be reinvestigated since oral lesions were not mentioned in the original descriptions of the disease. However, the lesions bear some features of those characteristic of the third or septic angina stage of alimentary toxic aleukia, a nutritional toxicosis of humans produced by eating grains infested with F. tricinctum.