Optimized fertile compost is one of the critical factors in promoting yield of button mushroom, Agaricus bisporus. During the process of compost preparation, certain thermophilic microorganisms including Actinomycetes, fungi and other thermophilic bacteria are involved which play an important role in self warming of organic materials, among which Actinomycetes, especially thermophilic species have been recognized as the main component. This research was conducted to evaluate the effect of compost micro flora on compost curing, with emphasis on the Actinomycetes. In order to study mycelial growth of mushroom, sterilized compost was separately incubated with 10 thermophilic bacterial isolates belonging to genera Streptomyces, Sachromonospora , Thermomonobispora, Nocardioides, Saccharopolyspora, Microbispora, Glycomyces and were incubated for 5 days at temperature 47ºC to 49 ºC. At the end of 5th day, temperature was reduced to 24ºC; mushroom spawn was added and kept within the same temperature. Growth rate of mushroom mycelia in each compost container was calculated 4 and 10 days after inoculation. Bacterial isolates from genera Streptomyces and Termonospora revealed a good support of mycelial growth; however Sterptomyces isolates stood in the second place, after those of Termonospora. It seems that Termonospora species can well adapt to environmental conditions of composting procedure. According to our data providing a medium growth for optimum growth of Actinomycetes during composting and artificial inoculation of compost with specific Actinomycetes in the early stages of phase II of composting, will greatly assist the directed degradation of compost raw materials which in turn will result in significant increase of well cured compost.

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