Ultrastructural observations of the process of Agrobacterium tumefaciens biovar 3 infection of grape cv. Chancellor

Abstract

Ultrastructural observations of Agrobacterium tumefaciens during pathogenesis indicated that the bacteria became pleomorphic and formed inclusions that migrated to polar positions which at lysis were discharged with other cellular contents into the environment of the xylem vessel lumen. Pleomorphism and the development of the inclusions which precede lysis suggest that the lytic process provides a manner in which T-DNA may be released. Lysis also appears to be the cause of the observed large reduction in bacterial numbers detected in xylem vessels 48–60 h after inoculation. In contrast, A. tumefaciens cells in vitro do not lyse during a 60 h incubation period, nor do they form inclusions.