Columbia Gniversity
inthe Citpof Hew Pork

[NEW YorK 27,N, ¥.]

DEPARTMENT OF ZOOLOGY

February 11,1949
Dear [r, becerberg,

iis fell I erete to ssk you ebout tue possibility of
recombination in E. coli strein 1£, and since vou wad net been
successful with that strain, T have cencentratead my stucies
on F128, under the Gireetion of Prof. F.J. hyan.

The problem in wuien Loum interested grew cut of some
observations I meade on struin 15 lust sumer wien 1 cbservec
changes in phage sensitivity apparently arising concurrently
with spontenecus loss cf a growth-facter re.uirement. Strain

FE, as you may know, is resistant to all 7 "T" phages, ville
kK1° is sensitive. In an attempt to repest my results in_Fl®%,

I have been selecting varicus phege-resistent mutants. in yceur
1947 Genetics peper, you mention the mutants Vy", Vy,r and
V.b, a very mucoid type. I nave elso repeetedly isolated a
muccid type, unc find tuat it is resistent to all the p.aces.
Moreover, 1 have wlse observed what ray be tne "instsebility”
you wentioned. Pernars this is tue save mutent; 1f you still
gave a strain containing Vypr, I woule very rucn ep ,-reciete it
if you ec.uld sené me a culture. Under viat concéiticns is
Vips selected, in your experience ?

Since you have not, I believe, publisuec your cata on
plage-resistence patterns in 41°, I wencer “netser Io mwizht ask
you abcut your results, to evceic 5 Guplication cf effcrt. tne
patterns I neve found repeatedly ure as follews:

1,5

1-7 (muccic) Seems to also be resistant te some “h"

° puage nutants
26,7

Oo fz >

OR 4,657

The mucoic mutent cen be vicked up efter plating with eny puasge,
cut it is mucn rsrer tnen 1,8. After plating witn Tz, the
remeining cells ure almost ell cf the mucoie type.

Are my results in agreement wits. your cboservaticns 3 +re
any of tnese nutents the Ve" mentienec in y Cur paper? I em

very intereste¢ also in your recombination stucies of tre leci

of priaze-resistent mutents, since 4 am plenuing to use whet may
be Vypand otner mutants in cresses.

I reslize tuat if you nave cuite #n accumulation of Cate,
my re-uest may be unreascneble, but 4 siiall be very -rateful fer
any bit cf informetion perteining to tunis prehlem.

Smads yours >
WMarqarsk fat