Investigations of the capability of Fusarium isolates from corn for biosynthesis of fusariotoxins

The aim of this paper was to investigate the potential of zearalenone (ZEN) and type A trichothecenes (T-2 toxin and diacetoxyscirpenole - DAS) for biosynthesis by Fusarium spp. isolated from corn kernels contaminated by mycotoxins. The samples of corn kernels (2004 and 2005 harvest) originating in different regions of Backa (Vojvodina, Serbia) were tested. Mycotoxicological investigations showed in most cases a significant contamination with deoxynivalenol (DON 200 - 2,460 ?g/kg) and ZEA (520 1,680 ?g/kg). Isolations and identifications of fusaria established only the presence of species F. verticillioides, after one month storage in freezer conditions, in fusariotoxin positive samples. The control cultures known as ZEA producers - F. graminearum GZ-LES, i.e. T-2 toxin and DAS producer - F. sporotrichioides KF-38/1/R were also tested. In vitro toxicological investigations of isolated fusaria were performed in liquid semisynthetic media (GPK or SPK), and on wet sterilized corn kernels, respectively. Under testing conditions, analyzed F. verticillioide and F. sporotrishioides isolates were not ZEA producers. Contrary to them, F. graminearum GZ-LES pure culture was very good producer of fusariotoxins; it biosynthesized max. 465,900 ?g/kg DON, and 4,416 ?g/kg ZEA, respectively. Cultivation conditions influenced a great deal of T-2 toxin production under laboratory conditions. In most cases, higher yields were obtained during the cultivation of F. verticillioides in liquid glucose medium (80-240 ?g/L). Contrary to the control strain F. sporotrichioides KF-38/1/R that under the same conditions synthesized, besides T-2 toxin (4.000 ?g/L) and DAS (240 ?g/L), isolates of F. verticillioides from corn grain did not show that ability.

25-hydroxyvitamin D3 metabolism by isolated perfused rat kidney

Kidneys of adult rats were removed and perfused with semisynthetic media with the object of elucidating the separate actions of factors implicated as modulators of renal metabolism of 25-hydroxyvitamin D3 (25(OH)D3). During a 3-h perfusion with 3[H]25(OH)D3, the kidney produced high yields of 24,25-dihydroxyvitamin D3 (24,25(OH)2D3) or 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) depending on whether the rat had previously been, respectively, normocalcemic, normophosphatemic, vitamin D-replete or hypocalcemic, hypophosphatemic, vitamin D-deplete. With longer perfusion (up to 12 h), kidneys from normocalcemic, normophosphatemic, vitamin D-replete rats mainly produced 24,25(OH)2D3 but also amounts of 1,25(OH)2D3. This pattern was unaltered by reducing Ca or Pi concentrations of perfusate or by adding parathyroid hormone. Kidneys of hypocalcemic, hypophosphatemic, vitamin D-deplete rats perfused with low Ca, low Pi medium for 12 h at first produced 1,25(OH)2D3 exclusively. However, 24,25(OH)2D3 appeared after 4 h and accumulated thereafter, whereas 1,25(OH)2D3 synthesis ceased after 7 h, a metabolic pattern unaffected by the concentration of substrate or end products in the perfusate or by addition of cyclic AMP. The model shows promise for studying regulation of 25(OH)D3 metabolism by the kidney.

Rubratoxin Formation in Soybean Substrates

Sterile soybeans, low and full fat soy meal, soy residue, soy curd, and soy whey fortified with different nutritional supplements were inoculated with spore suspensions of Penicillium rubrum P-3290. Yeast extract-sucrose (YES); glucose-malt extract; maltose-soytone; soy whey containing 1.75, 3.5, and 5.5% dissolved solids; and a maltose-salts medium were also inoculated. Cultures were incubated quiescently at 28 C for 7, 10, or 14 days. Rubratoxins were extracted with ethyl acetate and diethyl ether and resolved by thin-layer chromatography. Greatest yields of toxin were obtained from natural rather than chemically defined media. Semisynthetic media supported formation of moderate amounts of rubratoxins. Malt extract and glucose supported greatest production of both rubratoxins A and B. Unsupplemented soy whey or soy milk did not support rubratoxin production. Although soy meal supported production of both rubratoxins A and B (0.12–0.24 mg/g and 0.55–0.71 mg/g), low fat soy meal was more suitable for toxin formation than was full fat meal. Both rubratoxins A and B were produced by P. rubrum grown in soy whey fortified with soytone, malt extract, or glucose; only rubratoxin B was produced when yeast extract or sucrose served as supplements. YES broth supported formation of only rubratoxin B. Production of toxin in soybeans was influenced by time of incubation and temperature. Maximum yields of toxin on soybeans were obtained after 14 days of incubation at 25 C, after 28 days at 28 C, after 7 days at 32 C, and after 3 days at 37 C. Rubratoxin was not produced at 40 C. Yields of rubratoxin A in soy whey media ranged from 35–40 and from 15–28 mg/100 ml when malt extract or glucose were added; values for rubratoxin B ranged from 55–100 mg/100 ml and 65–125 mg/100 ml.

Cultural characterization and differentiation of nocardiae

Cultural and colonial morphology of 120 strains of nocardiae had been determined in three different semisynthetic media. On the basis of ability or inability to grow in the most reduced medium, and of growth pattern observed in the other liquid media, the nocardiae were categorized in six cultural groups. The reproducible and clear-cut cultural properties are considered a useful criterion for species differentiation.

THE INFLUENCE OF LIGHT AND OTHER ENVIRONMENTAL FACTORS ON MYCELIAL GROWTH AND SCLEROTIAL PRODUCTION BY BOTRYTIS SQUAMOSA

A monoconidial Isolate of Botrytis squamosa Walker was cultured on two semisynthetic media; modified White's medium permitted rapid and uniform mycelial growth; Czapek's medium supported abundant proliferation of sclerotia. When the fungus was cultured on White's medium and exposed to specific levels of incandescent irradiance, mycelial growth was arrested. The temperature inside Petri plates exposed to incandescent radiant energy was determined with the aid of thermocouples. Aeration and nutritional factors were found to influence the production of sclerotia. Concentric rings of sclerotia were produced on Czapek's agar when the fungus was exposed to periods of darkness alternated with periods of incandescent and/or fluorescent radiant energy.