TRANSDUCTION OF LYSOGENY IN ESCHERICHIA COLI 219 



fore exactly like any other genetic character. These results confirm pre- 

 vious findings of Lederberg and Lederberg (1953) and of Wollman (1953), 

 gained by means of bacterial recombination and showing that lysogeny 

 is controlled by a genetic determinant of the bacterium. In transduction 

 experiments the same efficiency is found in the transfer of lysogeny to 

 nonlysogenic bacteria and of prophage markers to already lysogenic 

 bacteria, proof that the genetic determinant of the bacterium which 

 controls lysogeny is the prophage itself. The three prophages which have 

 been used in this study are likely to be located at closely linked loci. 

 Their relationship is now the subject of more detailed investigation. 



Although we know little about the orientation of the prophage with 

 respect to the bacterial chromosome, data concerning prophage re- 

 combination during transduction seem to indicate that the m, end of the 

 \ prophage is the closest to the Gah locus. If the size of the transducing 

 piece is not too widely distributed and if recombination inside the pro- 

 phage region behaves in the same way as in other regions, such an ex- 

 periment may allow us to estimate the genetic size of the prophage as 

 compared to that of the adjacent bacterial region. In the case of the ex- 

 periment previously described and in spite of the small numbers in- 

 volved, the mi-rris distance may be estimated at about 4 to 6% of the 

 Galh-nii distance. Such an estimation is probably premature, because 

 we still lack a definite picture of the relationship between the prophage 

 and the bacterial chromosome. 



The case of bacteria found after transduction or mixed infection, which 

 carry several pairs of prophage alleles that segregate during bacterial 

 multiplication, is unclear. In such bacteria, the two prophages are likely 

 to be located on the same region of the bacterial chromosome, since both 

 additions and substitutions of prophage alleles are found in a single 

 transduction experiment. 



One of the most striking facts derived from transduction of lysogeny 

 is that a phage coat can contain, besides homologous genetic material, 

 the genetic material of one or more other viruses. 



ACKNOWLEDGMENT 



The author wishes to thank Mile Y. Nicolas for valuable technical assistance 

 and Dr. C. Levinthal for criticisms and help in the preparation of the manuscript. 



REFERENCES 



Appleyard, R. K. (1954a). Segregation of lambda lysogenicity during bacterial 

 recombination in Escherichia coli K12. Genetics 39, 429-439. 



351 



