Thermoactinomyces Tsiklinsky, a genus of thermophilic actinomycetes.

There has been considerable confusion concerning the nature and classification of thermophilic 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 designated as Thermoactinomyces. Since the introduction by Qrskov (1923) of the name Micromonospora 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 (1907) and Bruini (1905) under the name Actinomyces thermophilus Berestnev belong definitely to the Thermoactinomyces-Micromonospora group. On the other hand, Krassilnikov (1941) and Mishustin (1950) speak of A. thermophilus Berestnev as a spiral producing form, which would place it in the Streptomyces group. Waksman, Umbreit, and Cordon (1939) used the name Streptomyces thermophilus for the culture originally described by Gilbert (1904), with straight and not spiral forming conidiophores (Noack, 1912). Krassilnikov (1941), therefore, was right in concluding that the name A. thermophilus was used in designating a number of different organisms. No attempt will be made here to review in detail the literature on thermophilic actinomycetes. This was done to some extent by Waksman, Umbreit, and Cordon in 1939, by Krassilnikov in 1941, and by Mishustin in 1950. It was recognized