77 - BIOCHEMICAL AND MORPHOLOGICAL CORRELATIONS IN THE THERMOPHILIC ENTERIC YEASTS, SACCHAROMYCES TELLURIS, CANDIDA SLOOFFII, TORULOPSIS BOVINA and T. PINTOLOPESII

Abstract

Spontaneous respiratory-deficient mutants were isolated from the respiratory-competent thermophilic enteric yeasts, Torulopsis bovina and Saccharomyces telluris. A morphological and biochemical comparison was made of these yeasts with the naturally occurring respiratory-deficient thermophilic yeasts, Candida slooffii and T. pintolopesii. There were significant differences in cell size, temperature limits of growth and the effect of lipid supplement to the growth medium. Low temperature difference spectra revealed the presence of cytochromes aa3, b, c1 and c in T. bovina and S. telluris, cytochromes b, c1 and c in C. slooffii and T. pintolopesii and cytochromes c1 and c in the spontaneous respiratory deficient mutants. A light buoyant density (1.6785-1.6870) DNA band was present in all the yeasts. The mitochondrial origin of this DNA was indicated by its selective elimination on treatment of cells with ethidium bromide. The latter result suggested that the respiratory-deficient yeasts were analogous to cytoplasmic petite, mutants of S. cerevisiae. Although classical assimilation and fermentation tests indicated that the spontaneous respiratory-deficient mutants were strains of T. pintolopesii, it was concluded, on the basis of marked morphological and biochemical differences, that this was not the case.