The lipid content and composition of four strains of Paracoccidioides brasiliensis were analysed to determine any possible correlation with their virulence for hamsters and mice. Two strains, Pb168 and Pb141, were equal in virulence, Pb9 was slightly virulent and Pb140 was avirulent under the experimental conditions. No correlation was observed between virulence and the total lipid or phospholipid content of the strains. The lipid yield was highest in Pb9 and lowest in Pb168. Polar lipids were highest in Pb9 and least in Pb140. Phosphatidylcholine was the dominant phospholipid in all strains but its percentage was lower in the avirulent strain Pb140. Diphosphatidylglycerol, the least saturated lipid in all strains, was less abundant in Pb140 than in the virulent strains Pb168 and Pb141. In all four strains, neutral lipids constituted the major fraction of total lipids and triglycerides were the predominant individual lipid class, being more abundant in the avirulent and slightly virulent strains that in the virulent strains. The fatty acid profiles of total lipids and individual lipid classes of neutral and polar lipids obtained from the four strains were similar; however, the individual lipid classes showed patterns of preferential distribution of these fatty acids.

Differences in cell wall structure of Paracoccidioides brasiliensis strains isolated from localized or disseminated cases of paracoccidioidomycosis and from soil emphasize the importance of standardization if results obtained in different laboratories are to be compared.The cell wall of Paracoccidioides brasiliensis is a changing structure whose composition depends not only on the morphological phase, yeast or mycelium, from which the wall is isolated [4] but also on the origin of the strain and culture conditions [6].To confirm the last statement, five P. brasiliensis strains of different origin were studied with respect to their yeast cell wall structure. Strains IVIC Pb281, IVIC Pb282, and IVIC Pb289, are derivatives of strains 8285, 9570 and 6688 from the Instituto Nacional de Dermatologia, Caracas, Venezuela. These strains were isolated 1-3 years ago from patients with disseminated paracoccidioidomycosis. Strain IVIC Pb294 is a derivative of strain 7861 from the same source, isolated from a patient with a localized paracoccidioidomycosis. Strain IVIC Pb292 is a derivative of strain T1 isolated from mice inoculated with a soil suspension [1]. All these strains were maintained in vitro in GGY agar medium [1].To obtain cell walls from the yeast phases of these strains, PGY medium (peptone, 5 g l-I; yeast extract, 5 g l-I; glucose, 15 g 1 -l) was used. Cells were grown for 5-6 days on a gyratory shaker at 37°C. Ceils were collected, and w,alls isolated and fractionated as previously described [5]. Analysis of hexoses, aminoacids, and aminosugars were done as before [5]. Sugars were identified by thin layer chromatography in silica gel, using n-butanol: acetic acid: water (6:3:1, v/v/v) as the solvent and naphthoresorcinol (20 mg) in ethanol (10 ml) and concentrated H2SO, (0-2 ml) as developer.Results are summarized in Table 1. Alkali-insoluble fraction 1High amounts of this fraction were found in all strains. They were composed of variable quantities of hexoses (exclusively as glucose), amino sugars (as glucosamine)

N-methyl-N'-nitro-N-nitrosoguanidine, which is known to be a very effective mutagen in many systems, was used to induce mutants in the yeastlike form of Paracoccidioides brasiliensis strain IVIC Pb9, an imperfect fungus. Forty-three auxotrophic and 27 prototrophic morphological mutants were isolated after treatment with 50 ug of nitrosoguanidine per ml in 0.1 M citrate buffer, pH 5.0. Auxotrophic mutants required primarily either amino acids, purines, or pyrimidines. Some auxotrophs were also morphological mutants. The main morphological difference from the parental strain was the texture or the color of the yeastlike colonies. Only one prototrophic morphological mutant differed in the size and form of the yeastlike cells when compared with the parental strain. Auxotrophic mutants were used in pairwise combinations to attempt heterokaryon formation without success.