Conjugational Complementation Analysis of Transfer-Deficient Mutants of F lac in Escherichia coli

A series of 102 transfer-deficient (tra(-)) mutants of Flac (84 of which have been previously described) were classified as carrying frameshift, amber, ochre, UGA, and nonsuppressible mutations. Techniques were evolved for using cultures of F prime strains as efficient recipients in matings, for measuring the number of (F'/F') heterozygote cells in transient populations, and for measuring complementation between different Flac tra(-) mutants. These techniques were used to define nine tra cistrons and to assign most of the tra(-) mutations to one or other of these.