On the Classification of Actinomycetes

Abstract

The exact position of the actinomycetes or ray-fungi in the kingdom of lower forms of life has attracted considerable attention and has been a subject of much speculation. These organisms have been classified as bacteria, as fungi, and as a special group, either derived from one of the above or giving rise to both. With the accumulated knowledge concerning the morphology of the actinomycetes, it is being recognized more and more that they are an independent group of organisms, which is closely related to the bacteria through some of the constituent forms, but which has adopted a fungus-like form of growth. A brief description of the mode of growth and spore formation of these organisms will suffice to indicate their exact taxonomic position. Actinomycetes are characterized by the formation of normally branching threads or rods, frequently giving rise to a typical mycelium which is unicellular, especially during the early stages of growth. The hyphae are generally non-septate; under certain special conditions, septa may be observed in some forms. The mycelium is either vegetative and growing in the substrate, or aerial, where a special mycelium is produced above the vegetative growth. Actinomycetes reproduce through special sporulating bodies or from parts of the vegetative mycelium. The spore-bearing hyphae are produced on the mycelium either singly and monopodially, or in broom-like or cluster-like formations, or in verticilliate-like tufts or whorls upon the mycelium. The sporo-phores vary from long to very short forms. The spores may also