Soil streptomycetes and bacteria related to lysis ofBlastomyces dermatitidis

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Abstract
Twenty-eight microorganisms (22 streptomycetes and 6 bacteria) isolated from unsterilized soils baited with yeast cells of B. dermatitidis were purified on a mineral agar containing B. dermatitidis yeast cells as a carbon source. Twenty of these Streptomyces spp. and 2 species of the genus Bacillus when streaked individually on Sabouraud's Dextrose Agar, previously seeded with living B. dermatitidis yeast cells, inhibited mycelial growth. One species of Streptomyces was shown to be as inhibiting as Streptomyces nodosus Trejo (the Amphotericin-producing streptomycete). Six of the lytic Streptomyces spp. were individually shown to inhibit the growth of B. dermatitidis when they were introduced into sterile soil. Our limited experiments did not show that antibiotics caused inhibition of B. dermatitidis in media or in soil, but it was thought that the disappearance of B. dermatitidis from natural soils might be caused by inhibition of growth by antibiotics (or other metabolites), by enzymatic degradation of dead cells, and by autolysis from nutrient deprivation. Since living B. dermatitidis cells were not lysed directly by inhibitory microorganisms from natural soils, chemical soil factors essential for the destruction of walls of living fungal cells could have been destroyed in the sterilization of the soil.