the thermophilic species are found widely in nature but are most numerous in molding hay and cereal greins and in decaying vegetable and composts that have heated spontaneously to cemperatures of 50 or more. themophilic thermoactinomycetes are morphologically similar to thermomonospora spp. which thate many of their habitata, thermoactinomycetes can be readily differentiated from other thermophilic actinoycetes by the heat resistance properties of their spores (90 for 30 min) and resistance to novobiocin (25ml).(cel.lulolytic activity is absenr in thermoactinomycetes but common in thermomonospora) thermoactinomycetes spore are extrely long-lived and can be isolared from soi and sediment cores. they have been implicated in various forms of hypersensivity pneumonisis (extrinsic allergic alveolitis). especially farmer's lung disease. the single mesophilic species, T.peptonophilus has rarely been isolated and only from soil; it is not well characteried. Characteristics useful in distinguisshing thermoactinomycetes from other monosporic actinomycete genera aer given in table 27