HIROTA, Y.,  6enettcr lbpartaent, Stanford Unlverri ty, Stanford,
   -. _,
Callfornla: mtants of the P factor In Oschertchia coIi K-13. -- A
contaglous plemld f which occurs in the wlid type strrfn K-i2 confers
the GapecIty to act as DA In r-w! conjugatfon on rtr8ln8 of Lschortchfa
col I (Laderborg, Caval I 1, and Laderberg).  Recentt yI Melberg end burns

(these sbrtractr) foumd a mutant of F teraod f' whfeh conveys the
Hfr chrwtw (High frequency of r*cmbtnation). On tha basis of this
flndfng, we hwe isolated dlsttnctlve f' mutants from old broth cultures

of revrret Hfr 8tr8ln8.  The I` mutants mro dotectad by the conversion

of F- strains wtth which thay mro Ifmbted. Each Fe rutant controls
* chrrect*rlrtle prttem of tranrfer of loci from th8 ~7chrommme in

the llnkago soqwnce rImlIar to that of the ortglnel Hfr from which

was derived.  Llko stedard F+ the new F' can be dtslnfected by rcridlne
treatment (Htrota and r1jlaa) and passed to other F- rtralns. ---- These

results suggested that the f * factor fs spl t 2 off from thf6 Hfr lows

and Ilberatod Into ths cytoplasm.  Although free of the ehrmsomaI
site, It still detemlner tramfer of the chroa~~ with hfgh frequency,.
the point of chromosome breakage, and controls the oequema of wlefited

transfer of genes of the donor chmmmme during conjugation.  Its

speciflclty might be from the retention of a chromoroma segment of a
chmau~ome segment of the Hfr prrem from uhfch the F' orfglnater.

DaubIe infection as well es mutual wcInlon heve been observed In

coqblrprtlon of rmtdentlcal F frctorr.


Added note: XRX   F1 is used fn this abstract as a class term for F mutants

of wni ch F2 (kdel berg and Burns) i I an example.  F' (F-prime) should not be
confused with F' (F-one) as they use to denote the wild type F factor.  The    i

notation is being rectified.                                                                  -,