1128 MANUAL OF DETERMINATIVE BACTERIOLOGY 



ORDER VIRALES Breed, Murray and Kitchens. 



(Jour. Bact., J^^ , 1944, 421.) 



Viruses. Etiological agents of disease, typically of small size and capable of 

 passing filters that retain bacteria, increasing only in the presence of living cells, 

 giving rise to new strains by mutation, not arising de novo. A considerable num- 

 ber of viruses have not been proved filterable; it is nevertheless customary to in- 

 clude these viruses with those known to be filterable, because of similarities in 

 other attributes and in the diseases induced. Some not known to be filterable are 

 inoculable only by special techniques, as by grafting or by use of insect vectors, 

 and suitable methods for testing their filterability have not been developed; more- 

 over, it is not certain that so simple a criterion as size measured in terms of filter- 

 ability will prove to be an adequate indicator of the limits of the natural group. 

 Cause diseases of bacteria, plants and animals. 



Key to the suborders of order Virales. 



I. Infecting bacteria. 



Suborder I. Phagineae, p. 1128. 

 II. Infecting higher plants. 



Suborder II. Phytophagineae p. 1145. 

 III. Infecting animals (insects, mammals). 



Suborder III. Zoophagineae, p. 1225. 



Suborder I. Phagineae subordo novus. 



Viruses pathogenic in bacteria; bacteriophages. Containing at present only one 

 family, the Phagaceae. 



FAMILY I. PHAGACEAE HOLMES. 

 (Handb. Phytopath. Viruses,* 1939, 1.) 



Characters those of the suborder. There is a single genus. 



Genus I. Phagus Holmes. 

 (Lac. cit., 1.) 



Characters those of the family. Generic name from Greek phagein, to eat. 



The type species is Phagus minimus Holmes. 



Note: Bacteriophagum d'Herelle (Cempt. rend. Soc. Biol., Paris, 81, 1918, 1161) 

 a genus name applied in connection with early studies of bacteriophages, had as its 

 type species Bacteriophagum intestinale d'Herelle, a bacteriophage that is not now 

 identifiable or, more probably, a mixture of such unidentifiable bacteriophages, for 

 filtrates containing it were said to be capable of killing outright a culture of bacteria 

 (iftid., 1160). The genus name Bacierzop/iagfMm is, therefore, regarded as a nomen du- 

 bium, if not also a nomen confusum; subsequently it was abandoned by its author, for 

 reasons that are not clear, in favor of the genus name Protobios d'Herelle 1924 (Im- 

 munity in natural infectious disease ; pagF 343 of authorized English edition by George 

 H. Smith, Baltimore, Williams & Wilkins Co., 1924, 399 pp). Protobios protobios 



* Holmes, F. O., Handbook of Phytopathogenic Viruses, Burgess Publishing Com- 

 pany, Minneapolis, Minn., 1939, 221 pp. 



