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E. Current directions

The following items indicate lines of work which are in active progress
subsequent to the formal date of termination of this report, and beyond thise
lines which are already implicit in the previous investi gations. . |

Le Microscepic isolation of zygotes in BE. coli. ee

Techniques are being assimilated and ethers develeped for the direct
microscopic isolation of sygotes. Already a few linked pairs of bacteria from
mixed culture have been separated and proven to be, indeed, relevant to the
sexual process. These studies should make possible & correlation ef the ap-
pearance of living cultures ef the stained and fixed material, but it is not
yet possible to asseverate the role ef the apparent conjugal pairs in figure
1. | .

2. In connection with a temporary visit of Professor S. Rubbe (Departnent
of Bacteriology, University of Melbourne) @ few experiments are being carried
out in yeast. The main burden of these experiments 10/teespompari sen of the
conjugal precesses in yeast with these of bacteria, and attempts to separate
the mechanisms of transfer of nuclear and cy toplasnic elements.in the sexual
process, based on the work of Ephrassi in Paris. |

3. In previous studies on the genetic control of the formation of the ensyne
lactase in Escherichia coli it had been noted that the living bacteria displayed
@ much lower level of activity than they did after treatment with such agents
as bensene. Dr. Boris Rotman, in collaboration with Professor H. A. Lardy of
the Enzyme Institute and myself, has taken up this problem, again, of the
apparent regulation of intracellular lactase. The bensene treatment appears
to result in the separation of large amounts of nucleic acid while the ensyne
is left behind in the bacteria, and it appears likely that the activation by
benzene is the result ef the release of either nucleic acid or some other ‘ype

of specific regulator from the bacterium. Previous studies by enayme cheat sta

a
~2-

have told us much more about the eccurrence of enzymes and their vehavior in
isolated systema than their integrated functioning mumk with intact cells, and

. e
this system may have unusual advantages for consideration of the latter problem.

4. Dr. Aleck Bernstein is proceeding with a comparison of the physico-chemical
properties of the two antigenic types of flagella found in Salmonella, {¥ deus i t/
"specific" and "group" phase. Cells carrying these faagella differ in their
agglutinability by acriflavine ayes, Pu the chemical basis of this difference,

not yet elucidated, may help tbe understanding of the genetic differentiation

between them.

5. Dr. L. L. Weed(at Ratkimoxm the @M&% AMS Graduate School, Washington} had discovered
and privately reported to us that copper had a remarfable effect of Ninduedng"
small.colony variants in E. coli. As he is primarily interested in the biochemical
alterations, we agreed to collaborate on the genetic aspects. Miss Helen Byers in
this laboratory has reproduced en findings » but it is not yet established ©
with whether the copper is ac tively inducing the genetic defect, or whether spontaneous
copper-resistant mutants happen also to have the small-colony metabolic defect.

As mentioned elsewhere, most cases of specific induced mutations in bacteria (as
distinct from transductions) have evaporated on careful analysis, but this case

has not yet been sufficiently studied.