Chloramphenicol acetyltransferases specified by fi minus R factors

Chloramphenicol acetyltransferases specified by fi(-) (F fertility-noninhibiting) R factors were compared with those specified by the fi(+) R factors R1, 222, and R6-S. Three classes of enzyme were distinguished: class I was determined by group N fi(-) R factors and was indistinguishable from the enzyme determined by fi(+) R factors, class II was correlated with group W fi(-) R factors, and class III was determined by R387, an unclassified fi(-) R factor.