An improved selection method for λlacZ- phages based on galactose sensitivity

Edwin J. Mientjes, Joost H.M. van Delft, Brenda M. op't Hof, Jan A. Gossen, Jan Vijg, Paul H.M. Lohman, Robert A. Baan

Research output: Contribution to journalArticlepeer-review

47 Scopus citations


The determination of the lacZ mutant frequency in λgt10lacZ phage vectors isolated from the transgenic mouse strain 40.6 (MutaMouse), requires the screening of large numbers of phages on β-galactosidase activity. Existing methods rely on distinguishing a few white plaques on X-gal containing plates amongst a multide of blue ones which is both time-consuming and expensive. The new screening method described here employs the galactose sensitive Escherichia coli C lacZ recA galE strain into which a multicopy plasmid has been introduced, which results in over-expression of the galK and galT genes. In the presence of phenyl-β-d-galactopyranoside, a substrate for β-galactosidase, this leads to the suppression of λlacZ+ phage propagation without affecting the ability of λlacZ- phages to form plaques. With this method it is possible to screen 1.5×106 phages on a single 9-cm Petri dish. Furthermore, the need for blue/white screening has been eliminated.

Original languageEnglish (US)
Pages (from-to)67-69
Number of pages3
JournalTransgenic Research
Issue number1
StatePublished - Jan 1994
Externally publishedYes


  • 40.6 transgenic mouse
  • MutaMouse
  • galE
  • mutant selection
  • λgt10lacZ phage

ASJC Scopus subject areas

  • Genetics
  • Animal Science and Zoology
  • Agronomy and Crop Science
  • Biotechnology


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