Abstract

A very slow-growing micro-organism has been isolated from the synovial fluid of patients suffering from rheumatoid arthritis. This organism exhibits some of the properties of a mycoplasma such as growth in the presence of penicillin, and the requirement of serum and yeast, but generally does not behave like any known species of this group. Colonies resemble some types of T-mycoplasma in morphology and size. Scanning electron microscopy showed that the size of the components of these colonies was exceedingly small.