A total of 1191 actinomycetes were selectively isolated from ten soil samples collected from five different Egyptian Governorates including Alexandria, Qalubiya, Giza, Asuit and Sinai. Selective isolation was carried out by using five different pretreatment techniques including physical and chemical treatment. One hundred and eighty three isolates of rare actinomycetes were recovered. Dry heat treatment at 120ºC for 1 hour was the most effective method. Starch casein agar was the best medium which recovered the highest colony number of rare actinomycetes. The isolates were identified according to phenotypic and chemotaxonomic criteria. Genus Micromonospora was the most common and dominant non-streptomycete actinomycetes in soil. Genera such as Actinoplanes, Actinomadura, Saccharomonospora and Nocardioides were also recovered. Genus Actinoplanes was concomitant with clay soil as it was not isolated from sandy soil. Variation in the distribution of non-streptomycete indicates that soil properties play an important role for survival and propagation of non-streptomycete actinomycetes.
Key words: Rare actinomycetes, selective isolation, pretreatment, soil
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