I-like resistance factors with the<i>fi</i>⁺character

Abstract

SUMMARY The fi + (fertility inhibition+) property was originally described in R factors related to F (F-like factors). The original fi − factors, in contrast, were related to the transfer factor of a colicin I factor (I-like factors). We describe here a group of R factors which are fi + but I-like. It is suggested that all the terms fi + , fi − , F-like and I-like be used in the description of transferable plasmids.