[13] Some Siberian or Antarctic Actinomycetota are said to be the oldest living organism on Earth, frozen in permafrost at around half a million years ago.

[16] Most Actinomycetota of medical or economic significance are in class Actinomycetia, and belong to the order Actinomycetales.

[17] Actinomycetota, especially Streptomyces spp., are recognized as the producers of many bioactive metabolites that are useful to humans in medicine, such as antibacterials,[18] antifungals,[19] antivirals, antithrombotics, immunomodifiers, antitumor drugs, and enzyme inhibitors; and in agriculture, including insecticides, herbicides, fungicides, and growth-promoting substances for plants and animals.

[20] Actinomycetota-derived antibiotics that are important in medicine include aminoglycosides, anthracyclines, chloramphenicol, macrolide, tetracyclines, etc.

[23] Rubrobacteria Thermoleophilia Coriobacteriia Acidimicrobiia Nitriliruptoria Actinomycetia Chloroflexota Rubrobacteria Thermoleophilia Coriobacteriia Acidimicrobiia Nitriliruptoria Actinomycetia "Humimicrobiia" "Aquicultoria" Coriobacteriia "Geothermincolia" Rubrobacteria Thermoleophilia Acidimicrobiia Nitriliruptoridae Actinobacteridae The currently accepted taxonomy is based on the List of Prokaryotic names with Standing in Nomenclature (LPSN)[2] and National Center for Biotechnology Information (NCBI).