FOREWORD 



In 1951, the collection Papers in Microbial Genetics; Bacteria and Bacterial 

 Viruses appeared under the editorship of Joshua Lederberg. That collection 

 has been an indispensable aid to us and many others in the teaching of micro- 

 bial genetics. It has enabled every student to read a cross-section of the 

 original literature and thus become directly acquainted with the basic experi- 

 mental data that often outlive the conclusions based upon them. 



The Lederberg collection, however, appeared just at the eve of great dis- 

 coveries which, since that time, have enormously advanced our understanding 

 of the structure and function of the hereditary substance of bacteria and their 

 viruses. The transduction of bacterial genes by bacteriophages, the polarity of 

 bacterial conjugation, the role of DNA as the germinal substance of bacterial 

 viruses, the structure of DNA itself — all of these were discovered within the 

 two-year period following the publication of Lederberg's collection. New 

 techniques have also greatly changed the course and nature of research in 

 microbial genetics; in particular, the use of isotopic tracers in bacterial virus 

 research and the development of recombination tests of high resolving power 

 for the analysis of genetic fine structure have brought microbial genetics to the 

 molecular level. 



Hence it seemed urgent that a new, more up to date, collection should now 

 be made available; we have decided to assume this task, and hope that the 

 present book and its companion volume, Papers on Bacterial Genetics, will 

 answer the needs of at least the immediate future. The extent of the changes 

 that have taken place is indicated by the fact that of the more than fifty papers 

 we have selected for the present two volumes, only five have been retained 

 from the twenty papers of Lederberg's collection. 



In addition to the reprinted papers, each volume contains an introductory 

 text with its own bibliography, in order to compensate for the necessarily in- 

 complete and arbitrary nature of the selections. The selections themselves were 

 made for the sole purpose of providing students with a cross-section of the 

 literature, at a reasonable cost; in the words of Professor Lederberg "no 

 apologies need be offered for a selection which must be largely arbitrary." 



In conclusion, we would like to express our deep appreciation to the copy- 

 right owners and the authors who permitted us to reprint these papers, as well 

 as to those who have supplied us with rare reprints from which some of the 

 copy has been made. 



GuNTHER S. Stent 

 Edward A. Adelberg 

 Berkeley, California, 1960 



