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UNIVERSITY INSTITUTE OF MICROBIOLOGY

USTER FARIMAGSGADE 2A + DK-1353 COPENHACE™N K » DENMARK

7 122-9-+72
Dear Dr. Bachmann

I am writing you in. the hope that you can help me with some
E, coli strains, namely strains carrying deletions of the
operator distal part of the z-gene in the lactose operon. Since
I want the strains: for complementation of beta-galactosidase
the deletions should not stretch into the alpha part of the
z~gene,.

I would very much appreciate the strain W 46830 described
by Cook & Lederberg: Genetics 47 (1962),1335 and if possible
also the strain U 163 isolated by Jacob, Ullmann & Monod,
| Providing you have got the two strains I would be most

grateful if you will be kind enough to send them to me.

Yours sincerely

Mospus MS Ky. Khan

Mogens Trier Hansen.

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