In our first recombination expt. with your strain, 58-161 and W-677 were grown with a heavy mol[?]. (1 mol. of an overnight
culture of each separately and together) in 5 mol. of minimal medium and 0.2% yeast extract (Difeo[?]) and 0.2% casein hydrolysate
(Sheffield NS-case) and 50 mL/mol. biotin. After 6 hours of cultivation at 35 degrees C. Without shaking, the cells were
worked in the manner described in your paper, and 10-0, 10-1 and 10-2 mol. of the heavily turbid suspensions plated in 10
mol. of our minimal agar (of PNAS) on top of 15 mol. of socal.[ ? ] The results obtained were as follows (vertical columns
of successive colony counts at 1,2,3, and 4 days).
The irregularity that disturbed us in this expt. is the large drop from 10-0 to 10-1 inst. In a second expt. the results were
smoother ; in this we used a
medium with 0.5 % YE and 50 mL/mol. niotin, but no NZ.
At 48 hrs. incub. of the plates, the plate mixture gave 4 cols. from 10-0 of each of the two strains, 1 col. from 10-1 of
each, whereas the tube mixture (4 hrs, growth) gave 141 from 10-0 55 from 3X10-1, 17 from 10-1, and 8 from 10-2. There were
all nucloid[?] on further incubation, smaller non-nucloid[?] colonies continued to appear.
In another expt. which used your mutants with the same requirements but without the superposed heterozygosity for virus[ ?]
and fermentation. (I don't have
the sheet here - I think it was Y-10 instead of one of the above),
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the prototrophs obtained were not nucloid[?] but the results were otherwise much the same - very few prototrophs from plate
mixtures, perhaps 50 X as many from tube mixtures grown a few hours.
I see no obvious reason why this phenomenon should have turned up in our experiments but not in yours. Tho [SIC] there's
nothing special about our minimal medium, I suppose you'll have to try it if you want to duplicate out conditions. The
other factors seem pretty standard.
If you feel this presents a serious problem, I'd be glad in September to set up any parallel expts. that you believe would
help clarify it.
I'm glad Gordon Allen in definitely going to your lab at the beginning of August. I'm sure he'll learn a lot,
and I hope you enjoy the visit.