LIPID CONTENT OF FOUR STRAINS OF BLASTOMYCES DERMATITIDIS OF DIFFERENT MOUSE VIRULENCE

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Abstract
Four strains of Blastomyces dermatitidis showing marked differences in virulence for mice were studied to determine whether there was any relationship between lipid content and virulence. Replicate samples of heat-killed yeast and mycelial cells, after rupturing by grinding, were extracted with a chloroform-methanol mixture (2:1) in a Soxhlet apparatus for 48 hr. Total extractable lipid was computed by evaporating samples of the extracts to dryness and weighing; the phospholipid fraction was determined by a modified photometric technique. The amount of lipid in the yeast phase of each strain was relatively constant and characteristic as determined by extraction of four samples of each. The extractable lipid increased from 6.8% in the avirulent strain Ga-1 to 12.3% in the highly virulent strain SL-1, the lipid content correlating directly with increased mouse virulence. There was no similar correlation of phospholipid content with mouse virulence. The mycelial phases of two strains contained more than double the lipid and phospholipid present in the corresponding yeast phases. Data presented suggest that the lipid fraction of the yeast phase of B. dermatitidis, in addition to being related to the granulomatous reaction, is possibly related to virulence.