Fixed Pathogenic L Forms of Agrobacterium tumefaciens

UNSTABLE L forms of Agrobacterium tumefaciens (strain B .38) induced by glycine have been described by Rubio-Huertos and Desjardins 1 . In the present work two strains, A.T.B. and A.T. isolated from grapes, were grown in agar plates with 4 per cent glycine, where they readily formed typical L colonies. These were transferred simultaneously at intervals of 2–3 days to new plates of agar–glycine and glucose–agar without glycine. On the fiftieth transfer no reversion to the normal bacillary form was observed even after 32 further transfers in medium without glycine. The fixed colonies, formed by spherically dense elements, have the same macroscopical appearance as the normal colonies of A. tumefaciens grown in the same medium and have lost the typical features of the L colonies.