~ DEPARTME

UNIVERSITY OF CALIFORNIA

OF BACTERIOLOGY Address Reply to:

NAVAL BIOLOGICAL LABORATORY
NAVAL SUPPLY CENTER
OAKLAND 4, CALIFORNIA

26 April 1951
Dear Joshua,

This maxes the second letter this week but the
information herein may be worth your while. Streptomycin-
resistance mutation rates are so low in my problem that the
L&D graph is useless. also, the methods of approximation
are sort of cumbersome. I had our physicist crepare both
a table and graph which permits ranid calculation of "a"
from the second of L&D's methcds. The table requires the
following data:

Yr =- mean number of mutant colonies
C =~ number of cultures

N - mean number of viable cells/ml
X = 1.443 CNa

r G re x

0.01 100 1 1.78

0.02 ” 2 2.35

0.03 " 3 2.88

0.04 ” 4 Bed

0.05 "*" 5 3-80

0.06 " 6 4.20

0.07 * 7 4.60

0.08 * 8 5.00

0.09 * 9 5.40

0.10 ” 10 5-80

We have altered the L&D graph so that "re™ and "x"
represent the coordinates. They have separate curves and the
the intercept with the svecific curve (c) reoresents the de-
sired value. In this way we could handle any value of "rc"
and could extend the graph. Should you want a copy of the

graph, I*’1ll send one along.