vi THE ACTINOMYCES ;s, Vol. II 



open to question. The chief reason for this uncertainty is that although much 

 knowledge has since accumulated, especially during the last 20 years when many 

 Streptomyces species became known as antibiotic-producing organisms, taxonomic 

 work was largely neglected excepl by a few dedicated investigators. Recently. 

 however, several important contributions (Hesseltine et ah, 1954; Flaig and 

 Kutzner, 1954; Kutzner, 1956; Waksman, 1957; Ettlinger et al., 1958; Pridham, 

 L959) to this subject have appeared. A survey of the recent literature shows that 

 morphological characters are tending to replace physiological and cultural proper- 

 ties as the leading criteria in species characterization. It may be said that we are 

 now in a transitional stage in which our ideas are changing, not only concerning 

 the usefulness of criteria for species differentiation, but also with regard to the 

 species concept. Since ;i classification of a group of living organisms is always only 

 "preliminary," based upon the current knowledge of these organisms, I believe 

 that, in summarizing the subject at present, and in trying to combine the older 

 and newer ideas, I have presented useful criteria for species differentiation and 

 an outline of species concept for the genera Actinomyces, Nocardia, Streptomyces, 

 Micromonospora, and certain others. 



The rapidly accumulating information about the separation of some of the 

 genera into distinct groups or sections, the recent introduction of several new 

 genera, and the description of numerous new species, all necessitated a complete 

 recasting of the material presented in the last edition of Bergey's Manual and in 

 other treatises. This volume is largely the result. An attempt has been made to 

 bring together in this volume all the information required for the identification 

 of newly isolated cultures of actinomycetes. All descriptions and names for which 

 insufficient data have been provided, especially when no reproducible media have 

 been employed, have been placed in a separate chapter as "incompletely de- 

 scribed." Descriptions in which excessive and often confusing information has 

 been presented, have been abbreviated to tit a certain "standard." Often, this 

 standard has turned out to lie a Procrustean bed. I beg forgiveness, both from 

 the "reader" and from the preservers of the Code (International Code of Nomen- 

 clature of Bacteria and Viruses). My sole apology is that it is my sincere hope 

 that it would serve the purpose. 



The author wishes to acknowledge his sincere indebtedness to Dr. Norvel M. 

 McClung of the University of Georgia, to Dr. R. E. Buchanan of Iowa State 

 University, and to Dr. Ruth E. Cordon and Dr. Hubert A. Lechevalier of this 

 Institute, for reading individual chapters and for making valuable suggestions; 

 to Dr. Hans J. Kutzner of this Institute and Dr. Thomas G. Pridham of the 

 Northern Regional Research Laboratory, for reading the major portions of this 

 volume and for suggesting numerous corrections and modifications; to Miss Alma 

 Dietz of the Upjohn Company, Dr. Edward J. Backus of the Lederle Labora- 

 tories, and all others who kindly supplied photographs; to Mrs. Herminie B. 

 Kitchen for editorial work, and to Mr. Robert A. Day for assistance in the prep- 

 aration of the various illustrations and for reading the entire manuscript, 



Selman A. Waksman 



