Cultivation,serology, ultrastructure,and virus-like particles of spiroplasma 277F

Spiroplasma 277F, a helical, motile mycoplasma from rabbit ticks in Montana, was cloned and cultivated in liquid and solidified spiroplasma or mycoplasma media. Serum was required, glucose was fermented, and digitonin inhibited growth. Colonies of spiroplasma 277F possessed granular centers and were surrounded by smaller, subsurface “satellite” colonies. Cloned agent 277F was antigenically distinct from the suckling mouse cataract agent, the corn stunt organism, andSpiroplasma citri by growth inhibition and deformation tests, but exhibited weak cross-reactivity withS. citri in the precipitin ring tests. Although current passage levels did not cause cataracts in neonatal rats, kill embryonated hen's eggs, or cause bovine mastitis, definitive tests must await the availability of fresh isolates. Ultrastructurally, 277F closely resembledS. citri but displayed a system of 3-nm threadlike filaments in the exterior layer of its membranous covering. Two phagelike entities, similar to viruses associated withS. citri, were present.