UNIVERSITY OF CALIFORNIA

DEPARTMENT OF BACTERIOLOGY Address Reply to:
NAVAL BIOLOGICAL LABORATORY
NAVAL SUPPLY CENTER
OAKLAND 4, CALIFORNIA

23 April 1951

Dear Joshua,

Some results of recent work may be worth mentioning. As usual,
good old security makes me ask that you not disouss the work or the organism.

I have been working on streptomycin resistance since this anti-
biotic is the ne plus ultra for treatment. It is surely the mriracle drug
for the disease. The following data are extracted from results for a paper.
The L&D methods were used for calculating mutation rates,

48 hrs' incub: both methods gave essentially similar results: 0.6-2.1lx10711
72 hra' incub: both methods gave essentially the same results: 0.2=,07x10721,

The 72 hrs' incubation before plating on the streptomycin medium
yielded consistently lower values so that it would appear the longer incuba-
tion yielded greated viable counts but essentially no greater number of mutants.

I am testing the 2 premises involved in the formulae for mutation
rates. One has been finished: mutants and non-mutants grow and die at similar
rates. The calculations as well as design of experiment waretkken from the
Newcombe and Hawirko paper. The following data are expressed in their form:

initial inoculum contained 2.0x10*/n1 sensitive cells and 2.5x104/nl resis~
tant cells, After 24 hrs'incubation, there were 6.0x107/ml sensitive cells
and 7.0x10'/ml resistant cells; after 5 days' incubation, there were
3.0x108 /m1 sensitive cells and 1.1108 /m1 resistant cells, It appears that
there is a selection against resistant cells,

In checking the correlation between resistance and virulence,
a virulent strain was studied. To date, it appears that among resistant
colonies, there may be both virulent and avirulent celanies, We are getting

a reasonable sample, Therapy is being checked against resistant, virulent
clonese

I have finally convinced these ruteridden people that I should
go to the microbial genetics course given at Cold Spring Harbor this summer.
So, that will give me plenty of chance to get the techniques and methodology.
IT plan to have at least 1 full time and 1 part time helper assigned to me
on my return, One more species of the pathogens will be added to my project.
This one, perhaps K. pneumoniae, should parallel the E. coli work,

oa Sun -
Me bat p eur rie eH

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