Specialized Transduction of a Cysteine Marker by Rhizobium meliloti Phage 16-3

Abstract

Specialized transduction by phage 16-3 of 1 of the cys markers of R. meliloti is described. The frequency of transduction was 10-6 to 10-7/plaque-forming unit. About 2/3 of the transductants were heterogenotes, unstable for the cys+ marker, and yielded high frequency transducing lysates (10-2/plaque-forming unit). In phage lysates, plaque-forming transducing particles were directly demonstrated while non-plaque-forming particles were only detected indirectly via complementation of defective lysogenic transductants. In the defective transductants, the 2 distal ends of the vegetative phage map were lacking. By plasmid transfer, the attachment site of phage 16-3 was located close to the cys-46 and met-5 markers. Transduction of the met-5 marker could not be demonstrated.