we ‘ a 0% - ~~ we rn os c ‘ . cA Sh ge Bo! . Soe 7; = July 5> 1954 ‘Dear Professor Hinshelweod: » 5, - . .... I have been. struck by the degree to which current controversies on - the mechanism ef bacterial adaptation may be at cross—purposes owing to - the divergence of experimental material, a situation. that might be readily _correg ted, If I may: take the liberty-of. the remark, your observationa on '. the adaptation of B, lactis aerogenes to the utilization of D-arabinose _ * represenot-the clearest support of your argumentss the: multistep variations involved in resistance to proflavine would remire a much more elaborate’ review, At any rate; if I can find the time, I would like the opportunity: of reviewing the situation dn my own laboratory bench— particularly the experiment represented by figure 1 in the paper by Baskett and yourself, PRS,B139:58, May I ask your assistance in furnishing the strain you used for these experiments? To avoid any confusion, I should also like to have for comparison a subculture of what you would certify to be an irreversibly "trained" strain. The S.E.B. issue on Evolution has just come to our library, and I was most pleased to see the clarity with which you presented the issus (though I will not pretend that your argument and conclusion are such that I can fully accuiesce in them), especially at page 32, that we ure comcerned at the means of irrever-— sibility. Noone has questioned that physiological adaptations occur, aor that they ure represented in your experiments, but this very fact tends to confuse the experimental decision. In most of your wrk, my attempted intern etation (as you know) would be that induced physiological adaptations had permitted the development of populations large enough thet spontaneous variations might then occur and be selectively fixed, « mechanism hardly distinguishable from Wadding-— tons findings on Drosophila (at pp.194-198 of the same sympusium). I would not argue that genetic factors are required by natural law to be so insulated from the day to day history of the cell; but my reading of the evidence is that this is what happens to have come sbout during the evolution of living forms. I can assure you that I would be quite prepared to entertain evidence to the contrary, but so far (with som tortuosity to be sure!) the mutation theory does not seem to me to have failed. However, I could coment on this with less prejudice if I could reexamine relevant material with my ow hand. May I take the occasion to renew my remest for reprints, a favor I am haopy to reciprocate. I lack the following that have appeared in the Proc. Roy. Soc.: (Dean and Hinshelwood) 1952 140:339; (Hinshelwood and Jackson) 137:88; 136:562:; and(Kilkenny and Hinshelwood) 139:575, in addition thd? other that may have ap— peared subsenuently. I have noted your correction in Nature as to your "disregard" of selection mechanism. If "Bacterial Physiology" could be revised, I would rewrite this chapter to fit more closely to your current views 3 I have had an opportunity . ‘to substitute "minimized" in later printings, which I hope does not effect . ‘too much of a distortion. I should have auoted your letter of 16 Feb 1949 _ da the wording “to explore ‘the potentialities" in place of ‘to bolster the : applicabikity": perhaps I wag influenced by your paper with Peacocke(1948) which seemed, in a very different spirit (and to my mind wholly without | justification) to deny the materiality ofthe aumotrophic mutants that are the daily utensils of microbial genetics: However, your subsequent writings, including the letter to Nature seem to have adopted a "more eclectic outlook", so I trust there need be no further quarrel. By the way, you dco me too much honor .in attributing "Bacterial Physiology" to my authppship. I do not have the final corrected volume, but the proofs of the $.G.M. Symposium of last year contained in line (vour naner with Dean. the tarminal paragraph) that was entirely mystifying— perhups you would be kind enough to clarify it. "A synthetic agar plate was spread with @x10' [sie} cells.... single colonies were fpyddd visible on this plate". Can you distinguish so many single colonies on a plate, or is the figure a typographical error? If so few cells were inoculated that single colonies y¥x¢/ developed, the experiment is indecisive (from the selectionist viewpoint) since any mtants transfsrmed to the replica plate mst have constituted a negligible proportion of the colony during whose growth they mist have arisen. If there were 2x10/ colonies (#hich:I suppose could be: distingu- ished under the microscope), I don't see how one could maintain so precise 4 cor- respondene, after two replicas, that éne could expect congruehce by a factor of 5/2x 107, that ts-a:res ution of this fraction. x the-atea of a Petri dish, =75.om*, or about. (0.4. mm)%3.But eveniaccepting thie technical ‘tour de férce, the next’ plating suggasts .that thesé 5: ¢olonies altogether had less thai 1% mitant célls, wiich 1s quite compatible: with the possibility: of-'a mitant having arisen. some tind’ &fte@ the:16«32 cell stage of any. of the colonies. The later histery ‘of: the single colony. of tha 100 :-whese replica did: show a resistant shows that this colony did not come from a mutant cell, but that a new: mtation had a SE EE ges ty * : r r ay wy ae a a © . ; . ~ i } ES “Ee sa em ” + . . we a s . : oa ~ “ : ms whe “ “5 * a WEES can ot (tl Bag 7, : oe et my f a : TE 7 : PR Da Sde% ¥ ! : . . wots 0 ate : oo ” eee ceo - ca tle fa. : . A feos os - ree L . ha ES i an as ee: : ~ og Kony Be, ot we BD das ~ ma LF t og : . > . he, wees FB i aie aa o T . Pa FES ay hoe . m 7 Phe aed . a wf i 7 a wa 3 in te we - - 7 Ye ts c cat - 2 ~ ah ae g a eee 4 we ° + te " a, ¥ ~ f ext ~ geet vecpe Ps me ; eee eh ' in Qecurred during Lts déveldpment,.:.\I can asmure you that lag I followad a similar protacek,' would 0% Jhaw:olbkeined dndird tly delested strdptonyetn-resisatant mrtanta either. The smaxtimat oneichamdtt thab. we ifound could be.-eipscted' in prac- tice wae about 100-fold. at -each stage,-:and. this has tobe followed by. sample platings to be sure dne bas -recovered ‘the nmtantJclone,; unisss relatively large areas are xe-picked fren the plates. 95). f © : be oka 1% ae : * Mp PS LL es ~ 4 wD PE La eyed oe eee rt Yours sithoately-,: IE Date, CP ge es bey Peles om a ‘Lederberg ..~ Professor of Genetics