ABSTRACT
Accordingly, the “cryptogram” for phage T4 would read D/2: 169/40 : X/X : B/0, where D signifies DNA, X indicates a complex shape, and 0 means that no vector is known. This type of name was clearly unpronounceable, and the idea of a cryptogram was soon abandoned. Almost simultaneously, Bradley (1967) proposed a phage classification scheme based on nucleic acid type and gross morphology. His approach grouped phages into six basic types (A to F) consisting of (i) phages with contractile, long noncontractile, and short tails, (ii) cubic phages with DNA or RNA, and (iii) filamentous phages. Tikhonenko (1968) subsequently proposed a similar scheme, and Bradley’s scheme was later expanded to include various cubic, filamentous, and pleomorphic phages of recent discovery (Ackermann and Eisenstark, 1974).
