ASSOCIATION OF BACTERIOPHAGE PARTICLES WITH TOXIN PRODUCTION BY CLAVIBACTER-TOXICUS, THE CAUSAL AGENT OF ANNUAL RYEGRASS TOXICITY

The association between Clavibacter toxicus, the causal agent of annua l ryegrass toxicity in Australia, and a bacteriophage specific to the bacterium was examined. Wild-type C toxicus strains (designated type 1 ) did not produce corynetoxin, the toxin responsible for annual ryegra ss toxicity. When bacteria were infected with the bacteriophage, two t ypes of colonies resulted. One type (type 2) produced toxin and the ot her (type 3) did not. Antiserum was raised to purified bacteriophage p articles. Type 2 bacteria reacted positively to the antiserum in enzym e-linked immunosorbent assay (ELISA) but type 1 and 3 colonies did not . Culture of toxin-producing (type 2) bacteria with antiphage antiseru m restored normal colony morphology and eliminated activity in the cor ynetoxin bioassay. DNA hybridization revealed that bacteriophage DNA w as not present in type 1 strains but was present in type 2 and 3 strai ns. Bacteriophage DNA was not integrated into bacterial DNA and was pr esent in high copy number. Toxin-producing strains had an unusual morp hology, and when examined by electron microscopy, the bacterial capsul e and cell membrane appeared disrupted. Intact phage particles were vi sible in transmission electron micrographs of the infected bacteria. E vidence indicated that bacteriophage in toxin-producing bacteria (type 2 colonies) was in a phage-carrier state with C. toxicus, and bacteri ophage presence was correlated with production of corynetoxin.