Thermoactinomyces Tsiklinsky, a Genus of Thermophilic Actinomycetes

There has been considerable confusion con-cerning the nature and classification of thermo-philic actinomycetes. Beginning with the early studies of Kedzoir (1896), Berestnev (1897), Tsiklinsky (1899), Gilbert (1904), and Miehe (1907), it was recognized that the actinomycetes capable of growing at higher temperatures (50 to 65 C) represent two distinct groups or types: (1) One group produces a true aerial mycelium and forms spores in chains, either straight or spiral forming; some strains produce whorls of sporophores of the Streptomyces reticuli type. The members of this group definitely belong to the genus now recognized as Streptomyces. (2) The second group comprises forms which produce single spores on short branches arising from the mycelium. These forms were included originally by Tsiklinsky (1899) in a genus which was desig-nated as Thermoactinomyces. Since the introduc-tion by Qrskov (1923) of the name Micromono-spora for the single-spore-producing forms, the tendency has been to include the thermophilic forms with this genus (Waksman et al., 1939). The thermophilic cultures described by Miehe