Abstract
SUMMARY: The properties of two transfer-deficient Flacmutants (inEscherichia coliK12) carrying mutations in the cistrontraLare described. ThetraLproduct is needed for conjugational DNA transfer and for pilus formation, but not for surface exclusion; it is not plasmid-specific.traLmaps betweentraAandtraE; one of thetraLmutations is apparently polar ontraA. The properties of Tra+revertants of this mutation suggest that thetraLproduct is directly required for F-specific phage infection.