January 13, 1952
Ref. yra. 12/30&31/52

Dear Norton:
Just some notes in passing:

1) Method for studying adsorption of FA, phage similtanaously. Use heat-killed
cells of various types for the adsorption. Fairly dilute celle can probably be
used. Then add living cekis, e.g., SW-4k4 to adsorb remaining phage. Plate at
high concentration for transductions, dilute out to count infective senters.

2) What are you going to label in a tracer experiment to identify the cchorts!
You can't presuppose that only phage particles will labelled, and if you could
what would you measure. Can you dilute the tracer 107° or more from a single
phage particle? |

3) Am running into some obscurities on the role of XII, as receptor. E.0., a

paratyphi A that can be transinduced. Did you complete experiments on non-XIT
variant S. typhi and 8. pullorum? Do you have comparable data on the receptor
range of any other transducing phages, e.g.PLT~7?

4) Have just sent. a batch of reprints, labelled for local distribution. I hope

I haven't overlooked anyone—nlease remind me if I have. Also, have sent a few
mimeographed ciroularse-—use at your own discretion. By all means go ahead with
your distribution, but it would be well to collate the lists. What EF sent is

fairly complete, but some shipments'axm recorded are buried in another file, and

I sould only cheek individual ly.

5) H- of SW-414 seems to have an extraordinarily high rate of transinduction to +.
Am checking with further titrations. ‘

6) The lytic variant 22V picked up here probably is distinct from yours. It gives
clear plaqudes on LT-2. Lysogenization-protection exp't completed in a preliminary

way (I hope you know what I'm talking about), and shows that all (or as nearly all
4s can be measured) transductions occur in phage-infected bacteria. Further experi-

ments should tie this down to the infected clones of the progeny of infected
bacteria, I finally wolds yp that S. gal meant S. gallinarum and not EMS galac
tose! Would you like to have 22V?7 Although it gives muddy plaques on 38-666,
unfortunately it does not induce lysogenicity, so cannot be used as a marker in
substitution experiments.

?) SW-435 1s giving som reversions or near-reversions on D(O). Is this your exper-
ence?

8) UV'd PLT22 seems to give transductiona separable from plaques on SW—414, or bet~
ter, a new Gal- deriv. from SH-414, SW~950. I suppose it's just a matter of dose.
The transductions here are non~lysogenic.

9) Adaptation of PLT22 to paraB is only partly reversible by cultivation back on

LT2. Two mechanisms may be superimposed.

10) Levinthal suggests following for differential centrifugation. Use capillary
tubing. Break into segments after centrifugation. Assay.

Sincerely,

Joshua Lederberg
P.S. Am leaving for Chamblee ca. 1/26. Returning directly, hl —