Abstract
Bacterial mutants defective in plasmid formation were selected for their inability to be transduced to chloramphenicol resistance by bacteriophage PlCM. The mutants isolated are indistinguishable from a lon mutant strain. Both the lon strain and the mutants isolated here show very poor lysogenization by P1 and very low transduction to Gal+ by the plasmid formation of the λgal8-Nam7am53cI857. The lon+ gene function of the host bacteria is indispensable for plasmid formation, even though P1 and λ+ can grow normally on the lon strains and λ+ can be integrated normally in lon as well as in the lon+ bacteria. Phage mutants that can persist as plasmids in lon strains were isolated from P1CM. The function of the lon+ gene is discussed with regard to plasmid formation.