Use of cell cultures to study spiroplasma infections.

Invertebrate and mammalian cell cultures have been utilized to study various properties of spiroplasmas. Recent studies have focused on the interaction of Spiroplasma mirum with AG-4676, a cell line derived from the rat eye lens. S. mirum produced cytotoxicity in this cell line, consisting of vacuolization and an increase in the number of binucleated cells. The number of S. mirum organisms attached to the cell increased with increased age of infection. S. mirum does not grow in Dulbecco's modified Earle's medium + 10% fetal bovine serum, the growth medium for AG-4676. It does, however, grow in conditioned medium obtained as supernatant of 1- to 5-day-old AG-4676. This conditioned medium from AG-4676 also supported growth of S. mirum (GT-48), corn stunt spiroplasmas (Rio Grande) and the following unspeciated strains: M-55 (I-6), N-525 (I-7), CN-5 (IX) and AES-1 (X). It did not support S. citri, honeybee BC-3, EA-1 (VIII), MQ-6 (XII) or CC-1 (XIII). The growth promotion titer for S. mirum was 1:8, but this varied with the lot of fetal bovine serum. Biochemical characterization of this growth-promoting factor is in progress.