Transduction by Pl of gal and Lp regions from heterogenotic donors.

Joint transduction of gal region and site of A prophage attach-
ment by phage Pl is found approximately as frequent as transduction
for gal alone or Lp alone. The game prportions are found for (A)” and
(x)* donors; heteroplasmic induction does not seem to influence much
either the rate of transduction or the relative proportion of joint
and simple transduction, although it is known that heteroplasmic in-
duction is the normal response on transfer of \ prophage (2 x 107+
per active Pl) and transduction by integration is rather exceptional
(107? to 107’), Furthermore transductants from lysates obtained on
X doubly lysogenic donors are usually singly lysogenic for one parti-
cular prophage genome.

It was a&tempted to use Pl transduction to explore the site of
fixation of Adg on the bacterial chromosome; it may be assumed to be
either Lp or gal in comsidering only the two simplest hypothesis. In
marking endogenote and exogenote adequately it should be possibie to

distinguish the two alternatives;

Co Be gonor acceptor gal transductants expected to be
ay bt | ~ $*
et Re C — AP all def lys
x + 4 j=
i oe some A-sens, but more def lys
a BT all def lys
4 oL+ - +
— ° 7 c or all \-sens
dg j ot bo”
fen sentence cspeneenene about 1/2 j-sens, 1/2 def lys
orb about 1/2 a-sens, 1/2 def lys

etc

but if Adg is fixed on gal region: then transductants should always be

ab Lp
acne def lys, except the ones ori-
hoo .

ginating from Pl having been
\

co. ‘(Ahead

multiplied on gal’, A-Sens segregant
In all experiments carried out with several donor and several acceptor
strains A-sensitive transductants are found, although at variable rates
for different acceptors. But the analysis of the results - although
being not in favor of the hypothesis that Adg is fixed on the gal region-
does not permit clearcut interpretations for several reasons: frequent
recombination between homologous regions, apparently especially in

the processus of integration of the exogenote into the chromosome;
segregants present in the donor culture; rate of transferred exoge-

notes which do lead to stable transduction is relatively low, and it

is not known if this event is selecting some particular exogenotes.

Some experimental data:

assumed donor acceptor frequency of gal* AX lysogeny test
per active Pl sens / def lys

1727 /ex gal*-,dg 1-27 2x 1076 sens present
ut27 /ex 172*-,ag 17 107? 5/15

2" 1,2x 107? 0 / 20

1727 107? 8/12
1*27 fex 12*-xdg 27 7x 107° 10 / 23

2” 5x i078 12 / 16

1727 1078 2/10
12* /ex 1727 -rag 17 5 x 107° 2/8

27 1,5 x10 0 / 20

1-27 3x 1078 3/7

November 10, 1959 W. Arber