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GeodermatophilusRANK: GenusTAXONOMY: Bacteria -> Terrabacteria group -> Actinobacteria -> Actinobacteria -> Geodermatophilales -> Geodermatophilaceae -> Geodermatophilus OVERVIEW: Morphology is similar to that of Dermatophilus, a group of actinobacteria that have rudimentary hyphae (Figure 1) that eventually develop into complex sporangia (Figure 2). Geodermatophilus strains have been isolated from relatively extreme environments such as desert or high altitude soils. They also appear to resist gamma irradiation and have been recovered from desert soils after exposure to 30 kGy, along with strains of Deinococcus that are more noted for radiation resistance (Rainey et al., 2005). They have been recovered during programs aimed at isolating bacteria, in particular motile ones (Hayakawa et al., 2000), that have atypical metabolic features such as manganese-oxidizing ability, and are frequently associated with “varnish” formation, the black to brown coatings found on rocks in a diverse range of environments (Hungate et al., 1987) and, more surprisingly, in biofilm formation (Singh et al., 2003). Despite several trials, pathogenic lesions have not been produced by inoculation of Geodermatophilus isolates into rabbits (Gordon and Perrin, 1971). These trials had been attempted given the morphological and ontogenetic similarities with Dermatophilus. It is now known these morphological similarities constitute a case of convergent evolution of a few remarkable features rather than phylogenetic similarity. DNA G+C content (mol%): 72.9–74.6. Type species: Geodermatophilus obscurus |