In vivo transcription and translation of R-plasmid 538-1 DNA in Escherichia coli.

In vivo transcription and translation of R-plasmid 538-1 in E. coli was analyzed. Transcription of individual restriction fragments was determined qualitatively by utilizing the techniques developed by Southern (27), and quantitatively by carrying out DNA-RNA filter hybridization. The most active region of R-plasmid transcription in strains repressed for conjugal transfer was found to occur in the region of the R-plasmid carrying the antibiotic resistance genes. In plasmids derepressed for conjugal transfer, a high level of transcription from the transfer gene region was also observed. When strains carrying R538-1drd were induced with Hg++ a high level of transcription was observed from the region of the R-plasmid carrying the genes for Hgr. Hybrid ColE1 plasmids carrying restriction fragments from the antibiotic resistance region of R538-1 were segregated into minicells. Labeling of the minicells with 35S-methionine allowed identification of the proteins coded by the fragments. A limited number of proteins were detected, and several of these have been correlated with the antibiotic resistance genes carried by R538-1.