Q26

LEDERBERG, JOSHUA and BRUCE STOCKER, University of
Wisconsin, Madison, Wis. 4 ant Lister Tneti tate, Lonion,
Eng.--"Phenotypic’ transductiong of motility in Salmonella.
=—The formation of genetically Stable rast otmed slanss by
transduction of genetic fragments from one Salmonella strain
te another has been well established for a wide range of
markers, including motility. The possibility of scoring the
motility of single cells has allowed the detection of a mode
of transduction invelving a determinant which is not regularly
horitable, Motile celle were individually isolated within
three hours of mixing a nomaotile strain with competent
phage, Only five percent of the motile initials gave stably
motile subclones, usually in mixture with co-segregant par-
ental nonmotile celle. Ths remainder formed predominantly
nomotile clones containing no more than, at most, 100
motile individuals, Ths latter, when reiselated usually
trananitted motility to only one daughter at each suceessive
fission as if they carried a non-replicating determinant of
motility, The exact nature of these determinants is de-
batable: they might be erstwhile genes that had been dan-
aged or misplaced, or they might be persistent gene products
or both, The nomramion partition of motile pregeny in sub-
clones from carly coll lineages suggests two levels of de-
termination, either in organization or kind of motdlity~
conferring "particles", The emergence of a motile phenotype
and its transmission ts a single chain of descent occurs
spontansously in a few cells of certain strains.

Reprinted from Genetics, 02581, 1955,