The preparation of antigens of Rhizobium meliloti by ultrasonic disruption: an anomaly.

Abstract

Diffusible external antigens of whole cells of Rhizobium meliloti PDD1322 lost the capacity to precipitate with homologous antibodies in the gel diffusion test, when the cells were disrupted by ultrasonic oscillation. Sonicated cell preparations caused diminution of the homologous precipitin reaction when mixed with suspensions of whole cells. Sonicates contained a new, faster-diffusing antigen component, probably of intracellular origin. The serological inactivity of these sonicates was reversed by boiling. Diffusible antigens of whole cells of R. meliloti SU388, a strain closely related serologically to PDD1322, behaved similarly, whereas the cross-reacting antigens of strain CC8, of distant serological relationship to PDD 1322, were not affected by sonication. It is suggested that the external antigens and some intracellular compound released by sonication form a heat-labile, relatively nonspecific complex which will not take part in the precipitin reaction. Antibodies to sonicates of PDD1322 reacted strongly with the diffusible external antigens of whole cells of this strain. The same antigens of homologous sonicates reacted very feebly, but the new faster-diffusing component was evident.