When Antibiotics I was published in 1967, the teleological view was held by some that" antibiotics" were substances elaborated by certain microorgan isms for the purpose of competing with other microorganisms for survival in mixed ecological environments. However, not only had J. EHRLICH and his associates shown 15 years earlier that chloramphenicol was produced by Strepto myces venezuelae in cultures of sterilized soils but not in parallel cultures of the same soils which were not sterilized, but operationally, the search for anti cancer antibiotics was actively under way (Antibiotics I reporting on numerous such substances), although the concept of antibiosis could not logically justify such undertakings. This editor hesitates to accept the use of the term "antibiotic" for anti microbial agents of non microbiological origins which is sometimes encountered, but neither does he subscribe to the view that antibiotics are in some fundamental manner different from chemotherapeutic substances of other origins. Modes and mechanisms of action of chemotherapeutic compounds are not systematic functions of their origins nor of the taxonomical position of the target organisms. Consequently, in the selection of topics for Antibiotics III (published in 1975), synthetic drugs and natural products of higher plants (alkaloids) were represented, along with antibiotics in the strict sense of the definition. We now present Antibiotics V, for whose assembly the same selection criteria were applied as for Antibiotics Ill. The aggregate length of the contributions rendered it impractical to place the entire text between the covers of one book."

The first volume of Antibiotics was published in 1967 and contained a series of review papers on antibiotic actions. The editors, Drs. GOTTLIEB and SHAW, were aware of the rapid development of this field of study and provided a number of addenda in an effort to keep knowledge up to date while the book was in production. One year after the publication of Antibiotics I, this editor had a conference with Dr. KONRAD F. SPRINGER in which it became clear that another volume on actions of antibiotics would be necessary. For a variety of reasons, this was delayed until 1975 and became Antibiotics III. It did not contain addenda since it was recognized by the editors, Drs. CORCORAN and HAHN, that still another volume would have to follow and that in a moving field, such as the study of the actions of antibacterial drugs, no publication can be definitive or remain current, except for a limited period of time. The editors of Volume III grouped the contributions into sections: 1. Inter ference with nucleic acid biosyntheses, 2. Interference with protein biosynthesis, and 3. Interference with cell wall/membrane biosynthesis, specific enzyme sys tems, and those in which the mode of action was not known with certainty."

It is not certain that the editors of Antibiotics I (1967), Drs. GOTTLffiB and SHAW, fully realized that they were laying the foundation for an entire series of which we present here Vol. VI. For some time to come, this will be the last volume of the Antibiotics series. There are several reasons for this. Firstly, the discovery of medicinally useful antibiotics has leveled off, because the number of microbiological products with antimicrobial properties is not infinite. In 1972 some 2500 antibiotic substances were known, of which approximately one per cent are clinically useful. Further search for antibiotics has led to increasing frequency of rediscoveries and drasti cally decreasing frequency of discoveries of new antibiotics. As the search for antibiotics with a standard methodology in conventional ecological niches has exhausted itself, there is a paucity of new and interesting substances on which to undertake modes/mechanisms of action studies. Secondly, the mechanism of action field has come of age and its results are now academic knowledge. This also holds true for synthetic chemothera peutic drugs and becomes the case rapidly for toxic substances with anti-eukar yotic action. The study of mechanisms of action was undertaken for two reasons: one was the basic scientific desire to know how antimicrobial substances inter fered with microbial biochemistry; the second one was the hope that such infor mation would be useful in the premeditated design of synthetic antimicrobials."