Plasmid-Associated Functions of a Stable F lac

Abstract

Several functions associated with the stable plasmid, F lac S, have been examined. Our results indicate that the sex pili synthesized by Escherichia coli strains carrying F lac S are altered in some manner as evidenced by a very inefficient adsorption of male-specific phages. On the other hand, F lac S-mediated entry exclusion of related plasmids and plasmid incompatibility function(s) appear normal. The presence of covalently closed circular deoxyribonucleic acid in E. coli strains harboring F lac S indicates that it is an autonomously replicating plasmid. Based on β-galactosidase levels and the percentage of covalently closed circular deoxyribonucleic acid, it appears that the stability of the F lac S is not the result of multiple copies of this plasmid. F lac S appears larger than its precursor, F ts114 lac , in sedimentation through alkaline sucrose gradients.