INFLUENCE OF A SUBINHIBITORY DOSE OF ANTIFUNGAL FATTY-ACIDS FROM SPOROTHRIX FLOCCULOSA ON CELLULAR LIPID-COMPOSITION IN FUNGI

Antifungal fatty acids produced by the biocontrol fungus Sporothrix fl occulosa were studied on the basis of their effect on growth and cellu lar lipid composition of three fungi, Cladosporium cucumerinum, Fusari um oxysporum, and S. flocculosa, whose growth was decreased by 51, 33, and 5%, respectively, when exposed to 0.4 mg fatty acid per ml. The s ensitivity to fatty acid antibiotics from S. flocculosa was related to a high degree of unsaturation of phospholipid fatty acids and a low p roportion of sterols. The major responses of sensitive fungi to sublet hal doses of antifungal fatty acids from liquid culture of S. flocculo sa were: (i) a decrease in total lipid; (ii) an increase in the degree of fatty acid unsaturation (18:1 > 18:2 > 18:3); (iii) an increase in free fatty acids and phosphatidic acid and a decrease in total phosph olipids; and (iv) an increase in sterol/phospholipid ratio. These modi fications in lipid composition led to an increase in membrane fluidity in sensitive fungi, as demonstrated by assessment of fluoresence anis otropy using liposomes and 1,6-diphenyl-1,3,5-hexatriene probe. This a lteration in the physical state of lipids appears to be responsible fo r the previously demonstrated alteration of membrane structure and fun ction in fungi confronted to S. flocculosa.