Genetic andPhysical Studies ofRecombinant Plasmids FormedBetween an RPlasmid ofCompatibility GroupFIand SexFactor FofHfrH

Received forpublication 29April 1975 Recombinant plasmids between anR plasmid oftheFIgroup(R162/3) andthe sexfactor FofHfrHwereproduced after theconjugal transfer ofthis Rplasmid intoHfrH.Threetypesofrecombinant plasmids wereidentified after themating ofHfrH(R162/3) withrecAandrec+recipients. Onespecimen ofeachtype (pIP218, pIP222, pIP226) was studied inthisreport. Allthreerecombinant plasmids carry thesame genetic information forresistance toantibiotics (CSSuT)retained fromR162/3. pIP218 retained alltheother properties fromFof HfrH:derepression forpilus synthesis, mobilization ofthechromosome forthe proximally transferred HfrH genes (thrleu,proA),interference withT7 propagation, andability tobecuredbyacridine orange.pIP222 retained fromF ofHfrHthederepression forpilus synthesis andthesame polarity ofchromosome transfer (thrleu,proA),whilepIP226retained theinterference withT7 propagation andacridine orangecuring. Physical studies revealed thatreplica- tioncontrol and/or recoveryofF andpIP218 ascovalent circles ofdeoxyribonu- cleic acidaresimilar, andaredifferent fromR162/3. Thenew plasmids aremore likely theresult ofa substitutive recombination eventthana fusion. We propose genetic maps ofthese recombinant plasmids, showing theunequal participation oftheparental plasmids intheir formation. F-like Rplasmids havebeenclassified into six compatibility groups, FltoFVI(15, 25). TheFl groupincludes F,ColV2,ColV3(22), R386(8), R455(16), andR162,a plasmid isolated in