#,.

Februsry ii, 1947.

iiss dargaret Lieb,
berertuent of Loulou,
Coluiwis University,

Meu York 27, “4,

Yeas cigs Lieb,
‘

“ . e143 Yr :
ae Your meuld resistnt’ls very Likely the sane ss “ib - It is of course,

very Giificult:te secure for sensitivity to this strain, and it usu lly

seems to be resistant te ull 7 phages. However, Or, aro. “ovlek, ot the -
drotitute of “udlublulugy acc bieopnyeics, U. of Chicuze, tells we thut he

met ney TE Dep cages Sper ost qeq of ee hts at peg Ses
hos o¢cusion wll seucn uo few plu Wes oF ubner phages pec lou vi. iac siurain,

‘

wd a uve bud a sinllor diuceusistent oxperiaces. V_ Seams vw oc ch budned

ib
most often from ured cultures, and from old pactes: on which acid orocuebtion

has odcurved, ¢ewe On Lactuso- OP, Sinply cultivating it, using young transfers,
in nutrient broth, rapiday 2: ea bux ves sV,,°, aathowsh the r forn qu. be maintsadned
by continucus ssiection of meoid colonies. T hive nut been acle to Keep
a stuck culture of it, and have let ti au.

2. Ur. “Yowick cun probably add tewhit IT hive tc suy bout te wesistunce

patterns of K=12, In seneral, your date jibe with ours, exeeot th .t ve huve

recoversd severwl V. leew /l (sensitive to 15). In addition, a Ye (which

ia’
aay be an allel of VJ has been found which is partiuily sensitive to Tl, Tih,
and 75, dicre: wing in that order However, I have not seen a comlex type
such as /2,354,6,7. Gan you give me any nore particulars about 4t? If you
have produced * in a blo¢hemical mtunt, could you send mea transfer?

3. T3 and tT | usually give mucoid~like cultures, but these are rather dif-

ferent from Vip
A/ These have sometimes behaved inconsistentiy, .8 if they were reverting

to s, but the variability my be in the phage stocks. There are 2 systea

of T7 mitants which rapidiy ineerconvert, and Luria tells me that K«12 13
not sensitive to T3 itself, but only to a frajuent mtant which can be
called T3k. However, some of the biochsmic.l mutants, especially 679<680
and Y-1O0 are sensitive to 13 itself. Movie and Szilard have been working

on this, and I recomuondsthat you correspond with thom.

4. as IL remember, vr is specifically resistant to 6. But we nv longer have
our origing: stocks.

5. 48 far as nutcitional correlations go, dir. Zinder hers 212 so. rather
extensive exneriments iast suaner to see whether we could find any resistant
matants corre:ated with new nutrition.i rocuirenents, Live those for trip toe
Phane in £/i wad for proline in other B/- . All the T1-7 phages vere used,
butsmothing turned up. if you find anything, olense let ae uno.

6. The recombination data for ¥

ib

i and ve nave been nublishe:. Vl, is croebsably
too unstabie to be reliably usefus.in crosses, -Lthough by considerin: yaly
those orototrophs which ure still mmecoid, you cin set some infore ticn, ¥ 4
has not been definitely ‘Located, but is promibly to the left of Vi: between

it and Lacy. The other faetors have not been wnned yet, although ther havs

been used desultorily in sone erosses, and found to scera7 ite.

7. while there is no reason why you shouid not go uhend with Parthoy reeombinae

tion studies in theses strains, we have had some hints that the "stunc.cd stosks"
usec da crosses auy curry tae oyudvaieat of ehrososon.i woeeritioss. :2 are starting
fron senateh with .. new set of biochemical mutants from K-12 to try to straighten
out the situ.ticn. thecdiscrepaneies might affect the details of the iinkave

map, but nothing that can't be exsily rectified,

8. Please let me know if I ean be of help in any way.

Best rerarda, -

Sincerely,

‘ Joshua Lederbers
Assistant Profassor of Genetics