. The actinomycetes. Actinomycetales. 64 THE ACTINOMYCETES, Vol. I name Microhispora, with the type species M. rosea. These investigators proposed divi- sion of the family Streptomycetaceae as fol- lows : I. Spores formed in chains from aerial hyphae Streptomyces II. Spores formed in pairs on aerial hyphae Microhispora III. Spores formed singly on sporophores. 1. Mesophilic Micromonospora 2. Thermophilic. .Thermoactinomyces IV. Sclerotic granules produced (conidial forms unknown) Chainia According to Henssen (1957), the majority of thermophilic actinomycetes thrive better under anaerobic than
. The actinomycetes. Actinomycetales. 64 THE ACTINOMYCETES, Vol. I name Microhispora, with the type species M. rosea. These investigators proposed divi- sion of the family Streptomycetaceae as fol- lows : I. Spores formed in chains from aerial hyphae Streptomyces II. Spores formed in pairs on aerial hyphae Microhispora III. Spores formed singly on sporophores. 1. Mesophilic Micromonospora 2. Thermophilic. .Thermoactinomyces IV. Sclerotic granules produced (conidial forms unknown) Chainia According to Henssen (1957), the majority of thermophilic actinomycetes thrive better under anaerobic than under aerobic condi-. FiGURE 32. Waksmania rosea {Microhispora rosea), showing tho formation of pairs of spores either directly on the spore-hearing hyphae or on short side branches (Reproduced from: Lecheva- lier, M. P. and Lechevalier, H. J. Gen. Microbiol. 17: 104, 1957). tions; they may, therefore, be designated as facultative aerobes. The preference for anaerobic conditions varies with the species, especially in the case of freshly isolated cul- tures. When originally isolated under exclu- sion of oxygen, cultures grow well later also in presence of oxygen, but only at optimum temperature. Production of aerial mycelium is closely bound to optimum temperature. For example, Thermopolyspora bispora grows and produces aerial mycelium at 50 to 60°C under aerobic and anaerobic conditions; below that temperature, growth takes place only under anaerobic conditions; at 70°C, growth is good but aerial mycelium and spores are no longer produced. Henssen proposed division of the family Streptomycetaceae into the following genera, taking into consideration the thermophilic forms: A. Substrate mycelium nonseptate, spores pro- duced on aerial or substrate mycelium. I. Spores produced on substrate mycelium, mesophilic forms Micromonospora 0rskov II. Spores produced on aerial mycelium. 1. Aerial hyphae develop only as side or terminal branches of the substrate mycelium. a. Aerial hyphae
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