Detection of toxigenic Fusarium isolates by thin layer chromatography

A simple screening method was used to investigate mycotoxin production among 114 Fusarium isolates. Zearalenone, T-2 toxin, HT-2 toxin, diacetoxyscirpenol, neosolaniol, deoxynivalenol, nivalenol, fusarenon-X, butenolide, moniliformin and equisetin were detected. The importance of the use of a range of different substrates for mycotoxin production was proved.     

Fusarin C production by North American isolates of Fusarium moniliforme

A liquid culture medium was developed to screen North American isolates of Fusarium moniliforme Sheldon and Fusarium subglutinans (Wollenw. and Reink.) Nelson, Toussoun, and Marasas for their ability to produce fusarin C. Parameters which were important for the optimal biosynthesis of fusarin C included pH (3.0 to 4.0), aeration, and sugar concentration (30 to 40%). Of seven sugars tested, sucrose and glucose were the best carbohydrate sources for mycotoxin production, resulting in levels of fusarin C of greater than 60 ppm (greater than 60 micrograms/g) in liquid culture (28 degrees C; 7 days). A time-course study of fusarin C production was done over a 21-day period, during which time pH values, glucose concentrations, nitrogen levels, and fungal biomass were determined. Of the two Fusarium spp. studied, 13 of 16 isolates of F. moniliforme produced fusarin C in liquid medium (14 of 16 in corn), while none of the 15 isolates of F. subglutinans studied was found to produce the compound. Levels of fusarin C produced by Fusarium sp. isolates growing on corn ranged from 18.7 to 332.0 micrograms/g.     

Differential cytotoxicity and mycotoxin content among isolates of Fusarium moniliforme

Curvularia lunata was found causing (disseminated phaeohyphomycosis among a group of Nezara viridula (Insecta:Heteroptera) parasitizing vegetable crop Vigna unguiculata. Dark lesions were seen on pronotum and abdominal sterna. Experimental lesions were produced by applying 0.1 ml of 6.2 × 10⁸cfu/ml^–1 on abdominal sterna. Histopathology revealed that almost all internal organs and tissues showed extensive damage. It is interesting to note that C. lunata exhibited predeliction for chitinous tissues and elicited cellular immune response by granulocytes (phagocytosis). This is the first report of phaeohyphomycosis of an insect, extending the disease to invertebrates.A promising research career of one of the authors (Mrs. Vinita Dubey) was cut short by untimely death. This paper is dedicated to her memory.     

Fusarin C production by North American isolates of Fusarium moniliforme.

A liquid culture medium was developed to screen North American isolates of Fusarium moniliforme Sheldon and Fusarium subglutinans (Wollenw. and Reink.) Nelson, Toussoun, and Marasas for their ability to produce fusarin C. Parameters which were important for the optimal biosynthesis of fusarin C included pH (3.0 to 4.0), aeration, and sugar concentration (30 to 40%). Of seven sugars tested, sucrose and glucose were the best carbohydrate sources for mycotoxin production, resulting in levels of fusarin C of greater than 60 ppm (greater than 60 micrograms/g) in liquid culture (28 degrees C; 7 days). A time-course study of fusarin C production was done over a 21-day period, during which time pH values, glucose concentrations, nitrogen levels, and fungal biomass were determined. Of the two Fusarium spp. studied, 13 of 16 isolates of F. moniliforme produced fusarin C in liquid medium (14 of 16 in corn), while none of the 15 isolates of F. subglutinans studied was found to produce the compound. Levels of fusarin C produced by Fusarium sp. isolates growing on corn ranged from 18.7 to 332.0 micrograms/g.     

Mutagenic activity of Fusarium moniliforme isolates in the Salmonella typhimurium assay.

A total of 33 isolates of Fusarium moniliforme from several food or feed crops were grown on sterile cracked corn, and chloroform-isopropanol extracts were assayed for mutagenic activity in the Salmonella typhimurium-microsome system by using tester strain TA98 or TA100 or both. Extracts of 21 (64%) of the isolates assayed against TA100 were mutagenic. Activities of seven of these extracts were increased markedly with incorporation of the liver homogenate (S-9) into the assay. Seven (33%) of the isolates assayed against TA98 were weakly active, with the liver homogenate having little effect on reversion rates.     

Mutagenic activity of Fusarium moniliforme isolates in the Salmonella typhimurium assay.

A total of 33 isolates of Fusarium moniliforme from several food or feed crops were grown on sterile cracked corn, and chloroform-isopropanol extracts were assayed for mutagenic activity in the Salmonella typhimurium-microsome system by using tester strain TA98 or TA100 or both. Extracts of 21 (64%) of the isolates assayed against TA100 were mutagenic. Activities of seven of these extracts were increased markedly with incorporation of the liver homogenate (S-9) into the assay. Seven (33%) of the isolates assayed against TA98 were weakly active, with the liver homogenate having little effect on reversion rates.     

串珠镰刀菌产生毒素条件研究

从培养基种类和培养方法等方面对串珠镰刀菌产生毒素条件进行了较系统的研究。结果表明串珠镰刀菌的最佳产生毒素条件为马铃薯 葡萄糖培养液、pH 91、2 h光暗交替、25℃、培养10 d。     

Production of fumonisins by Fusarium moniliforme and Fusarium proliferatum isolates associated with equine leukoencephalomalacia and a pulmonary edema syndrome in swine

Fumonisin B1 (FB1) and FB2 were isolated from corn cultures of both Fusarium moniliforme and Fusarium proliferatum. Respective concentrations in culture materials of FB1 and FB2 ranged from 960 to 2,350 and 120 to 320 micrograms/g for F. moniliforme and from 1,670 to 2,790 and 150 to 320 micrograms/g for F. proliferatum. Thin-layer chromatography, gas chromatography-mass spectroscopy, high-performance liquid chromatography, and liquid secondary ion mass spectroscopy were used for detection. Fumonisins from F. proliferatum have not previously been reported.     

Production of Alanine by Fusarium moniliforme

Fusarium moniliforme grown in a chemically defined medium in submerged culture accumulated amino acids extracellularly. Alanine and glutamic acid were present in greatest amounts, with traces of glycine, lysine, threonine, and valine detectable. Increasing the glucose and urea concentrations of the medium increased yields of alanine. Further increases in alanine production occurred with elevated levels of mineral salts in the medium, whereas the addition of a vitamin mixture proved to be inhibitory. Chemical changes resulting from the growth of F. moniliforme in the final fermentation medium disclosed maximal alanine production, mycelial weight, and glucose consumption after 72 hr of incubation at 28.5 C. Total soluble nitrogen, by contrast, was minimal at the same time period. The pH remained in the alkaline range throughout the fermentation.     

Production of fumonisins by Fusarium moniliforme and Fusarium proliferatum isolates associated with equine leukoencephalomalacia and a pulmonary edema syndrome in swine.

Fumonisin B1 (FB1) and FB2 were isolated from corn cultures of both Fusarium moniliforme and Fusarium proliferatum. Respective concentrations in culture materials of FB1 and FB2 ranged from 960 to 2,350 and 120 to 320 micrograms/g for F. moniliforme and from 1,670 to 2,790 and 150 to 320 micrograms/g for F. proliferatum. Thin-layer chromatography, gas chromatography-mass spectroscopy, high-performance liquid chromatography, and liquid secondary ion mass spectroscopy were used for detection. Fumonisins from F. proliferatum have not previously been reported.     

Variability in the production of trichothecenes by Fusarium sporotrichioides

Production of trichothecenes as with all secondary metabolites, will vary from one producing strain to another. If a particular metabolite is produced at all it may be assumed that the part of the genome involved is intact and it would seem most likely that the quantitative variation observed from strain to strain might arise from modifications in metabolic control. An opportunity to study this phenomenon is presented by the existence of cultures of Fusarium sporotrichioides descended from the original T-2 toxin producing strain isolated in 1965 from French corn by W.C. Snyder and originally referred to as F. tricinctum and since then maintained independently by different culture collections. These strains continue to be T-2 toxin producers but are now morphologically distinct on media such as potato sucrose agar.Preliminary results are reported in studies designed to detail the differences in toxigenicity between these strains.     

Characterization of an Extracellular Dextranase from Fusarium moniliforme

An extracellular dextranase (EC 3.2.1.11) was purified approximately 75-fold from cell-free culture filtrates of Fusarium moniliforme. The purified dextranase was of the endo type, and isomaltose was identified as the primary end product of dextran hydrolysis. The molecular weight of the dextranase was determined to be 39,000 by gel permeation chromatography. The enzyme was most active at pH 5.5, and the temperature optimum was near 55 C. Activity was not inhibited by either ethylenediaminetetraacetic acid or iodoacetate. The Km for dextran with an average molecular weight of 10,000 was estimated to be 1.1 X 10(-4) M. The electrophoretic mobility of the dextranase was distinctly different from that of a Penicillium-derived commercial dextranase. The F. moniliforme dextranase was also found to differ from the commercial preparation by its greater relative activity against glucans isolated from Streptococcus mutans.     

Mycotic pneumonia caused by Fusarium moniliforme in an alligator

Fatal pulmonary infection in a captive alligator (Alligator mississippiensis) is reported. At necropsy, the animal appeared to be in excellent nutritional condition, but a severe necrotizing bronchitis with bronchiectasis was present. Histological examination revealed numerous branched, septate, hyaline hyphae within the necrotic debris lining the bronchi and rarely infiltrating into the adjacent stroma. The fungus cultured from the lung was identified as F. moniliforme.     

Biosynthesis of labeled fumonisins in liquid cultures of Fusarium moniliforme

Fumonisins were readily produced in cultures of Fusarium moniliforme using a defined liquid medium. Addition of 200 mg of d₃-methyl L-methionine to 100-ml cultures of F. moniliforme gave increased overall yields and high levels of deuterium (²H) incorporation into fumonisin B₁. Approximately 90% of the resulting fumonisin B₁ contained 6 deuterium atoms, while 9% of the product contained 3 deuterium atoms. Deuterium was shown to be incorporated exclusively in the methyl groups of the fumonisin backbone. The addition of as little as 5 mg of labeled methionine stimulated fumonisin production, but only about 5% of the fumonisin produced contained 3 deuterium atoms.Abbreviations ELEM equine leukoencephalomalacia Mention of companies or products by name does not imply their endorsement by the US Department of Agriculture over others not cited.     

Microbiological Aspects in the Hydroxylation of Estrogens by Fusarium moniliforme

A strain of Fusarium moniliforme (IH4), isolated from soil, showed outstanding enzymatic abilities to hydroxylate a number of estrogens. Estrone and estradiol were transformed into the 15alpha-hydroxy derivatives, and estradiol 3-methyl ether was transformed into the corresponding 6beta-hydroxy derivative. Delta(6)-Estrone was not hydroxylated. The accumulation of 15alpha-hydroxyestrone was influenced by the nutritional conditions of the fungus. Maximal yield was obtained when the organism grew in Czapek solution supplemented with yeast extract, although good conversion was also found in a peptone-corn molasses medium. Substitution of NO(3)-N in Czapek medium with NH(4)-N, lactalbumin hydrolysate, Casitone, or Casamino Acids resulted in limited hydroxylation of estrone. A remarkable strain specificity was demonstrated in this conversion. Of 13 strains of F. moniliforme and Gibberella fujikuroi under investigation, only 2 strains (IH4 and ATCC 9851) accumulated substantial amounts of the 15alpha-hydroxylated product. However, marked quantitative variations were observed which are attributable to a different ability of the organisms to degrade the steroid nucleus. Biochemical instabilities were also found through the appearance of spontaneous variants lacking steroid-hydroxylating activity. Replacement culture studies revealed that 15alpha-hydroxylation of estrone was dependent on the supply of external phosphate; exogenous nitrogen or energy sources were not required. Most of the enzymatic activity was confined to the mycelia. Microconidia showed a very limited hydroxylating activity, even in the presence of supplements or energy sources.     

Maize Response to Salicylic Acid and Fusarium moniliforme

Effects of salicylic acid and Fusarium moniliformeon trypsin inhibitor activity, lectin activity, lectin carbohydrate specificity, and salicylic acid content in maize seedlings were studied. Changes in trypsin inhibitor activity, lectin activity, and the content of endogenous salicylic acid after administration of exogenous salicylic acid or a pathogen were shown to depend on the resistance of maize strains to Fusarium. The data suggest that salicylic acid is involved in the induction of trypsin and lectin inhibitors that are important in the formation of defenses against abiotic and biotic factors in maize sprouts.     

D-泛解酸内酯水解酶产生菌的筛选及产酶条件研究

筛选到一株产D-泛解酸内酯水解酶的菌株,经鉴定为串珠镶孢霉菌（Fusarium monili-forme)SW-902。产酶条件研究表明,用甘油作碳源,蛋白胨作氮源,初始pH8.0,温度26℃,摇瓶培养3d,产酶量最高,在60L发酵罐中通风发酵45h,产菌丝体生物量7.18g干菌体/L,D-泛解酸内酯水解酶酶活力达到0.92IU/g干菌体。