Transduction in Escherichia Coli K-12.

SYSTEM of genetic transduction has been discovered in the sexually fertile A K-12 strain of Escherichia coli. This transduction is mediated by lambda, a temperate phage for which K-12 is normally lysogenic. The distinctive features of the lambda-K-12 system include the following: (1) The transductions are limited to a cluster of genes for galactose fermentation. The GaZ loci are closely linked to each other and to Lp, the locus for lambda-maintenance. (2) The transducing competence of lambda depends on how it is prepared. Competent lambda is produced by induction of lysogenic bacteria; lambda harvested from infected, sensitive hosts is incompetent. (3) The transduction clones are often heterogenotic, that is, heterozygous for the Gal genes which they continue to segregate. Technical advantages of the lambda system include recombinational analysis by the sexual cycle and the availability of lysates in which nearly every lambda particle is competent.