We have previously shown that some strains of can serve as recipients in conjugation (Con) with while others cannot (Con). To determine if a replication defect contributes to the inability of certain strains of to serve as recipients in conjugation, we attempted to introduce a naturally occurring gonococcal β-lactamase plasmid into by transformation. Various methods were employed, and all proved unsuccessful. Since specific sequences are required for DNA uptake in transformation of , we constructed a number of hybrid plasmids containing chromosomal DNA inserted into the β-lactamase shuttle vector, pLES2. When nine randomly selected plasmids with inserts were used to transform an strain which did not accept the gonococcal β-lactamase plasmid by conjugation, transformants were observed with four of the hybrid plasmids. The presence of one of the hybrid plasmids, pCAG9, in transformants was confirmed by agarose gel electrophoresis, Southern hybridization, and β-lactamase production. When an donor strain containing pCAG9 was used in conjugation with several strains, only those strains that were previously shown to act as recipients could accept and maintain pCAG9. The ability of pCAG9 and the other three hybrid plasmids to transform Con strains demonstrates that the β-lactamase plasmid can replicate in Con strains, and, therefore, the Con phenotype is due to a block in some other stage of the conjugation process.


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