Tf-26Vx, an antibiotic produced by a thermophilic fungus.

Thermophilic fungi are commonly found in self-heated habitats, such as composts, and help to decompose various plant materials. However, there have been few reports describing production of biologically active substances by these fungi. During a screening programme for new antibiotics produced by thermophilic microorganisms, a substance with activity against Gram-positive and strictly anaerobic Gramnegative bacteria was isolated from the mycelium of a thermophilic fungus. The present paper deals with rhe production, isolation, identification and biological activity of the antibiotic, Tf26Vx. The fungus, strain No. 26, was isolated from compost and was identified as Malbranchea prdchella SACCARDO and PENZIC var. sulfurea (MiEHE) COONEY and EMERSON, a member of the thermophilic Fungi Imperfecti which has been reported to produce several hydrolases and penicillin". On yeast-glucose agar, strain No. 26 grows at ter.iperatures ranging from 28° to 55°C. The optimum is between 45 and 50°C and growth was very slow at the lower limit. Marked changes were observed in the surface of arthrospores grown at different temperatures. Viewed under the scanning electron microscope, those grown at 50°C were cylindrical or oblong and their surface was smooth. Arthrospores grown at 37°C were cylindrical with distinctly rough walls (Fig. 1). For the production of Tf-26Vx, Malbranchea pulchella var. sulfurea strain No. 26 was cultured at 45°C with aeration and agitation in the following medium: glucose 3.0%, yeast extract 0.5'11malt extract 0.5'/',, NaNO3 0.3%, KCI 0.05 K 2HPO, 0.1%, MgSO., • 7H 2O 0.05%, FeSO, • 4H_,O 0.001'/,,, Adecanol (Asahi Denka Co., non-ionic detergent) 0.01 , (pH 6.5 before sterilization). Tf-26Vx was produced mainly in the mycelium and was extracted with 80% acetone. The extraction and purification procedure is summarized in Fig. 2. Tf-26Vx is pale yellow, crystalline, and melts at 332°C with decomposition. It shows [aj; + 3.46 (c 0.95, CHCI3). A molecular formula of C3oH2 O,o was established by elemental analysis and by mass spectrometric determination of the molecular weight (M.W. 546). Tf-26Vx is soluble in chloroform or dimethylformamide, and insoluble in water, methanol or ethyl acetate. The UV spectrum in chloroform has absorption maxima at 273 and 385 rim. The IR spectrum (KBr) shows characFig. 1. Difference of the surface of arthrospores of 41albranchea puk•hella var. sulfurea strain No. 26 grown on yeast-malt extract agar at 37 C and 50°C. (A) 37'C