March 5, 1953

Dear Al:
I enclose the following cultures and phages:

Salmonella typhimurium, LT-2 (Lilleengen's type 2, #85)
Salmonella typhimurium S¥-912 (= Boyd's #1404)

Salmonella gallinarum, idwards 3728~52

PLT-22 (extracted from S. typhimurium L1T-22, and grown on LT-2)
22¥ a lytic variant of PLT-22,

I have been working extensively only with LT2, of these ecvltures.
PLT-22 can be grown to a respectable titre (4 x 1040) on broth cultures
of LT-~2 with no difficulty; agar plute cultures should give even higher
yields (Zinder has been playing with this). PLT-22 will induce lysogenicity
readily in both typhimurium strains; I am just about to examine the S. gallinarum.
Promptly after infeotion with PLT-22, LT~2 becomes resistant to lysis by 22V:
one can in fact titrate PLT~22 by the count of surviving bacteria. The fact that
almost ali cf the transductions 68 LT-2 mtanta are protected against 22V, under
conditions cf low miltiplicity cf the transducing phage PLT-22, 1s possibly the
strongest evidence that the transducing particle is also an active virus particle.

S. gallinarum is sent as being supposedly much less pathogenic for man.
It serves as a satisfactory indicator for the twomphages, but has not yet been
studied in detail. PLT-22 displays a wide range of "host~induced" modifications
whhn adapted in different hosts, but this is of no great nresent concern,

Cultures of the phages can be heated to 60° for 30-60 minutes to sterilize
them before further handling, as a safety measure. My routine procedure has been
to heat the (fully turbid) "lysates", sediment the killed bacteria, and preserve
the supernatant with chloroform. PLT-22 is quite rugged, ard can most easily be
concentrated and purified by precipitation with cold alcohol or saturated ammonium
sulfate.

Yours sincerely,

a