Q22

MORSE, M. L. (Introduced by M. R. Irwin.), University
of Wisconsin, Madison, Wis.--Iransduction of certain loci
an Escherichia coli K-]2.--Lysogenicity for the phage lambda
is determined by a muclear gene closely linked to a cluster
of loci affecting galactose fermentation (Lederberg and
Lederberg, Genetics 38, 51), A small fraction of the cells
in galactose-negative cultures can be transformed to fer~
menters by lambda lysates from positive, or from non-
homologous negative, cells. The interactions between cells
and lysates are concordant with allelism tests by crossing.
With excess assay cells the number of transformations is
proportional to the amount of lysate added, with an effici-
ency of about one transduction per million plaque forming
particles. Most transformed clones are unstable for galace
tose fermentation and contime to segregate galactose
negative cells after many single colony isolations, When
Gal,” cells are transformed with wild type lysates the
negative segregants from the "heterozygous" positives are
Gal)“. When Gal,” cells are transformed with a lysate of
Galo” cells, the negative segregants are usually Galy~,
occasionally Galo", ani rarely Gal,"Galo~. Similar
results have been observed with various combinations of
Gal), Galo, and Galj,. Exceptional jysates transduce
with an efficiency greater than 107+, These lysates are
capable of (1) transforming a large fraction of a cell
population, (2) transducing Gal- as well as Gal* alleles,
and (3) showing that adsorption of lambda to a cell is
necessary, but not sufficient for transformation, The
phage here, as in Salmonella (Zinder and Lederberg, J.
Bact. 64, 679), acts as a passive vector of genetic
material. Other loci tested, not linked to Gal, are not
transduced by lambda,

Reprinted from Genetics, 39298h<5, 195).