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Organisms having a complex life cycle similar to the animal pathogen Dermatophilus congolensis have been isolated from soils of the United States. The soil isolates grow readily on agar media producing a black, friable, or sooty colony; in broth, the isolates produce a thick sediment with a clear supernatant fluid and occasionally a black surface pellicle. The generic taxon Geodermatophilus is proposed for these soil isolates. Geodermatophilus differs morphologically from Dermatophilus in thallus shape, ensheathment, and branching, and physiologically in respect to blood hemolysis, casein hydrolysis, carbohydrate utilization, acid production, and media requirements. The type species proposed is G. obscurus. Three subspecies are recognized.

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The use of whole mounts in the electron microscope study of Micromonospora chalcea is a rapid and simple method for obtaining morphologic information about both the spore and sporophore. Spore anomalies were observed by this method, and their anatomical basis was confirmed by thin sections. Spore shape and surface ornamentation varied with the age of the spore and should be taken into consideration when characterizing and comparing the spores of various isolates. The spore of M. chalcea is not an endospore as found either in the bacilli or in the thermoactinomycetes; it lacks the multilaminar inner coat found in these thermoresistant spores. The spore of M. chalcea appears to contain an outer coat, or possibly coats, and a less electron-dense, thick inner coat or cortex. The spore of M. chalcea differs from the spore of streptomycetes in lacking a sheath around the hyphal wall. This sheath surrounding the hyphal wall in streptomycetes contains the spore ornamentation such as spines or hairs, but in M. chalcea spore ornamentation arises in the outer portion of the spore wall as wart-like protuberances. The spore of M. chalcea appears t o develop its coats in a centripetal fashion similar t o streptomycetes.Cross walls in M. chalcea are double and appear to develop in a manner similar t o streptomycetes in which the hyphal wall appears to "peel apart," the inner portions being continuous with the cross walls. Mesosomes and nuclei found in thin sections of M. chalcea appear similar to those found in streptomycetes and other gram-positive bacteria. The electron microscope data obtained for M. chalcea ATCC 12452 in this study appear to be representative of the morphologic and anatomical features found in other species of Micromonospora that we have studied.Spore silhouettes made by direct electron microscope observations of unfixed, unstained, or shadowed whole specimens have been used for characterization and comparison of the spores of species of actinomycete genera, in particular the genus Streptomyces (41, 44). These silhouettes, while useful for characterization and comparison of morphology, leave unanswered a number of anatomical questions as to what is internally responsible for the external morphology. These anatomical questions can be answered through the time-consuming method of fixation, embedding, thin sectioning, and staining. In this study an attempt was made to correlate morphology Micromonospora chalcea is the type species of the genus Micrornonospora (drskov (27), and ATCC 12452 has been designated as the neotype strain (29). Since the type species usually has an important bearing on our concept of the genus, we have studied in detail the structures and anomalies observed in this strain. Based upon this information and other workers' observations (M. W. Rancourt, Ph.D. thesis, Rutgers Univ., New Brunswick, N.J., 1963; references 1, 2, 20), an expanded descriptio:, for the genus Micromonospora is recommended. MATERIALS AND METHODS(silhouettes) with anatomy (thin sections), for this is important if the...

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