INN { which a strain lives, one of the phases 1s selected and displaces the

uce Wethace, other. The unique feature is the convergence observed in the rough

JAN -3 1982 phase resulting in an apparent loss of the distinctions between the

i types. The mutations from smooth to rough seem to be physical

aA losses of the distinctive features of the cells expressed in the poly-

D NPs ay VT er yerre 4 saccharide ‘envelope, as though the germ plasm of this organism

contained a certain stable nucleus and a variable periphery which

te : may be disposed of altogether. Still more extravagant, and yet con-

( The 7 clusively proved, phenomena are enacted if a culture of the rough

AL Sete 77 Da ao “fe : phase is added to a vaccine consisting of dead cells of the smooth
CotnrAn : phase with a trace of the antirough serum. For in this case rough
herr “re \ x ° LH : = reverts to smooth of the same type to which the cells in the vaccine

had belonged. Thus, if a small amount of the rough culture derived

a = from the normal (smooth) line of Type II is added to a suspension

ae bt Ae =. of smooth cells of Type HI devitalized by heating, a smooth line
Annee BON = of Type III, not of Type I, is produced. By this method it seems
boarte bogota : . ot to be possible to convert at least many of the thirty-two types of the
: pneumococci into many other types. The transformation of the

Awotk bauer D _ rough into the smooth of the same type from which the rough had
on wy 1 J ns ‘ _ *  .been originally derived is, of course, also accomplished by the same

 

AAA . * method, if a vaccine of that type is used. The vaccines lose their 2

fr : On clin erttel awe transforming effectiveness after being heated to the boiling point, _

» (fee Ay + tg. rharre - but cell suspensions heated to 60°C. and subsequently frozen and a
Jt LAr Cc oo thawed are effective. El
forrssed D NA . mo The strains “transformed” from one type into another retain their 4

new properties after cultivation on suitable media or after passage Pe
through animal hosts. Hence, they acquire not merely a temporary €
. , polysaccharide envelope of a kind different from that which their o:
bah Aen Hardt Eetinuoer) NAL ancestors have had, but are able to synthesize the new polysaccha- :
. a wrens Mot ride indefinitely. If this transformation is described as a genetic
. ; mutation—and it is difficult to avoid so describing it—we are deal-
ing with authentic cases of induction of specific mutations by specific
treatments—a feat which geneticists have vainly tried to accomplish
in higher organisms. Admittedly, there are many obscurities in the
situation which ought to be cleared up. For example, it seems to be B,
unknown whether the transformation affects every cell in the culture EE
or whether only some cells mutate and others are destroyed; whether &

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