In vitro production of the spherule phase of Coccidioides iiiiniitis

The in vitro growth of the spherule (sporangium) phase of Coccidioides immitis has posed a problem of prime interest in the study of the disease coccidioidomycosis. The fungus is dimorphic in that it has a cultural, or sapro-phytic, phase in which growth consists of my-celium and arthrospores, and a tissue or par-asitic phase consisting of thick-walled nonbudding spherules (sporangia) varying in size from 20 to 80, in diameter. Endospores measuring 2 to 5,u in diameter are developed in the mature spherules by cleavage planes, released into the tissues by rupture of the spherule wall, and serve as a means of reproduction and dispersal. The freed endospores enlarge and develop into the characteristic endospore-containing spherules. The physiological requirements for the pro-duction of the tissue phase are not known, al-though studies have been made concerning the developmental stages of spherules in the tissues of mice, along with their relation to host reaction (Tarbet, Wright, and Newcomer, 1952). In vitro production of the spherule phase has been achieved with some degree of success by several investigators by means of special media (Bake