THE ROCKEFELLER INSTITUTE FOR MEDICAL RESEARCH

66TH STREET AND YORK AVENUE
NEW YORK @1,N_Y.

Jan 5, 1956

Dear Joshua,
i have sent you today a package containing:

1. Bresch agar dyes; Alizarol yellow GW cone.
Hational Fast ool Blue 2
These are vat dyes frou National Aniline
Instructions:

To 300 ec of bottom agar (any couplete medium) add just before
pouring 7.5 ce of a glucose solution (60g glucose + 100 ce water); 1.5 cc
of blue dye solution (2% w/v); %.5 cc of yellow dye suspension (2.5% w/v). The
yellow dye precipitates at roon temperature. Shake to resuspend before adding
and it will dissolve in the warm agar. No dye is added to the top jayer. The
dyes 1 assume are self sterilizing. The slucose can be autoclaved. he major
difficulty with this mediwn id the depression of plaque size, with lambda this
could be serious. However most of this is probably due to the excess acid from
the glueose fermentation, It is my own feeling that the glucose concentration
could be considerebly reduced without affecting the unknown reactions.

2. Sw665 and Sr6é0 and a scoring rezegent.

Sr60 is lysogenic derivative of 665 for a phage intentionally not quite
"type" (y not +). It is stable and can be induced as well es T’2 lysogenic.

i am obviously retracting what I wrove in my last letter, “he difficulty
lay in certain peculizrities in the cross streak reactioh for im-unity and
lysogenicity. :t high multiplicities of phage the lysogenic is inhibited giving
a pseudosensitive response. Still contaainated clones do not; thus the apparent
segre.ation. The solution I have emektmex: enclosed should easily differentiate
sensitives and lysogenics. As the phage put xk out by the lyserenic does not
crow well on parental 665 the Qnsmeemiez interaction on cross-streeking is poor
but scoreable, Can't use T.2 as 605 carries a phage attacking it as does the

ysog¢enic . All scoring should be done on EMS O or “4B xylose, c65 and its
derivatives grow slowly on this medium and will necessitate 45 hour or more
incubation. This slow growth came in with the xyicse mutation. You may recall
that 541 was a mixture of xyl + and slow. ihe «x l- mutation was obviously in the
xyl slow stocka as it can be shown by transduction to differ fron type by two
genes. The phage mutational capacities are exhibited by all mbes members of
the 541 line. Have too much data with 665 to switch to 541.

Because of the critical nature of the experiment I shall also try my
hand at delysozenizing & SroO and will let you know immediately if I succedd.
Hope one of us does.

Sincerely
)

LS
of
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