ANDRE LWOFF AND ANTOINETTE GUTMANN 



strains of E. coli conserve their lysogenic nature after numerous passages in the 

 presence of an antibacteriophage serum. Analogous results had been obtained 

 by F. Burnet and M. McKie for various bacteria (1929a,b) and by E. and E. 

 Wollman (1936) for B. megaterium. Since the antibacteriophage serum neutral- 

 izes free bacteriophages, these experiments demonstrate that lysogeny can 

 maintain itself in the absence of free bacteriophages, provided that the concen- 

 tration of antibacteriophage serum during the entire length of the experiment is 

 sufficient to immediately inactivate all bacteriophages. In other words, one must 

 be sure that, under the conditions of these experiments, there is no possibility of 

 a free bacteriophage infecting a bacterium before being neutralized by the serum. 

 This condition was probably met in some of these experiments, but this is not 

 a priori certain. And nothing enables us to state categorically that bacterio- 

 phages which adsorb to bacteria are actually inactivated by serum. 



It is also known that lysogeny maintains itself equally well in cultures growing 

 in media supposedly deprived of calcium; in fact, in media containing oxylate or 

 citrate (E. and E. Wollman, A. Gratia). But numerous organic substances 

 possess the power to form complexes with calcium; these complexes could then 

 dissociate, and, in organic media, it is difficult to ascertain the absence of free 

 Ca"''"'' ions. The fact that lysogeny of a culture maintains itself in a citrate 

 medium, whereas the adsorption of bacteriophage does not take place except in 

 the presence of calcium, is but an argument in favor of its endomicrobial perpet- 

 uation. 



Finally, it was shown by Den Dooren de Jong that the lysogenic function of 

 B. megaterium is transmitted in cultures which have been derived from a spore, 

 and even from a heated spore. This is true for all sporogenic lysogenic strains. 

 This is, thus, an additional argument in favor of the endomicrobial transmission 

 of the bacteriophage. But, unfortunately, the form of the bacteriophage within 

 the interior of the spore is not known. If one adds to all of these considerations 

 the fact that in a lysogenic culture every colony — supposedly obtained from a 

 single cell — is lysogenic, one sees that a considerable accumulation of facts 

 favors the conception that the faculty to form bacteriophages is hereditary, that 

 is to say, independent of any exogenous reinfection. In our experiments, lysogeny 

 is maintained in the course of 19 divisions in the absence of free bacteriophage. 

 If the bacteriophage does not multiply within the bacterium and if the mainte- 

 nance of lysogeny proceeds from particles adsorbed on the original diplo-bacillus 

 and distributed equally over the daughter bacteria, then that diplo-bacillus must 

 have carried a minimum of 2^^ or 524,288 bacteriophages at the onset. The 

 chance of an unequal repartition over the daughter cells in combination with our 

 selection of that bacterium which happened to have inherited the smallest 

 number of bacteriophages after each such division is so small that it need not be 

 taken into consideration. 



S. Bayne-Jones and L. A. Sandholzer (1933) estimated the average volume of a 

 single B. megaterium as 2.5 n^. Let us assume the value of 6 m^ for the average 

 diplo-bacillus. According to McLauchlan, E. M. Clark, and F. W. Boswell 

 (1947), the dimensions of the head of the bacteriophage of Bacillus megaterium 



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