Growth and Sporulation of Thermophilic Fungi and Actinomycetes in O₂-N₂ Atmospheres

SUMMARY

Six species of actinomycetes and 12 species of fungi were studied. The actinomycetes were: Pseudonocardia thermophila, Streptomyces rectus, Thermoactinomyces glaucus, T. vulgaris (two isolates), Thermomonospora curvata, and Thermopolyspora polyspora. The fungi were: Chaetomium thermophile var. coprophile, Humicola grisea var. thermoidea, H. insolens, H. lanuginosa, Malbranchea pulchella var. sulfurea, Mucor miehei, M. pusillus, Myriococcum albomyces, Stilbella thermophila, Talaromyces thermophilus, Thermoascus aurantiacus, and Torula thermophila. None of these organisms grew in atmospheres of pure nitrogen. The minimum O₂ concentrations that allowed trace growth to occur were lower than those that allowed measurable growth (determined by measuring colony diameter). When the YGS medium was used the fungi could grow and sporulate in atmospheres containing less O₂ than when the basal medium (synthetic) was used. Neither the fungi nor the actinomycetes sporulated when only trace growth was observed. The actinomycetes and fungi required more O₂ for sporulation than for growth. Growth of the fungi and actinomycetes in low O₂ atmospheres was less than that of the controls incubated in air. All of the fungi and actinomycetes survived incubation for 10 days in most of the atmospheres containing low O₂. Use of the YGS medium improved the survival of the fungi.