Bacteria and Viruses 51 



Recommendation 8a. Sect. 1. Naming of Taxa 



RECOMMENDATION 8a (4). The designation phase should be restricted to 

 well-defined stages of a naturally occurring alternating variation. 



ANOTATIONS 



Recommendation 8a (4) . Andrewes described diphasic \ariation of 

 the flagella of many serotypes of SalmoneUa. This form of variation 

 appears to be limited to the H (flagellar antigens) of species of 

 Salmonella and certain closely related bacteria (Arizona group 

 [Edwards]) . The use of the term "phase" for a more permanent vari- 

 ation (e.g., S — ^R, V — ^W, "phases" of Haemophilus pertussis) is un- 

 desirable. Phase Aariation as here defined is thus far unknown outside 

 the family Enterobacteriaceae. 



RECOMMENDATION 8a (5). A form (forma) or special form (forma specialis) 

 is a subdivision of a species of a parasitic or symbiotic microorganism dis- 

 tinguished primarily by adaptation to a particular host. It is named prefer- 

 ably from the scientific name of the host written in the genitive. 



ANNOTATIONS 



Recommendation 8a (5) . This recommendation has proved useful 

 in the naming of certain fungi which are selective as to host plant, 

 but which show little or no consistent morphological differences. 

 Some plant rusts, for example, are to be found on a number of 

 species of grasses or \arieties of the grasses, but they are physiologic- 

 ally so specialized or adapted that the forma found on one species or 

 variety of host will not grow on some other. No adequate morpho- 

 logical distinguishing character is known. A form so specialized as 

 to pathogenicity may be termed a forma specialis, designated by 

 "f. sp.," followed by the name of the host species to which it is 

 adapted. This method of identification has only occasionally been 

 used in naming bacteria, though it may be useful in distinguishing 

 bacterial plant parasites or symbionts. For example. Fang, Allen, 

 Riker and Dickson noted a forma specialis, Xanthomonas translucens 

 f. sp. phlei-pratensis on the grass timothy {Phleum pratense) . 



RECOMMENDATION 8a (6). State (or stage) is the name given to the 

 rough, smooth, mucoid and similar variants which arise in cultures of many 

 species of bacteria. These are usually regarded as alternating states which 

 are often reversible, and indeed by some authors considered as part 

 of a pleomorphic life cycle. They may be designated by some vernacular 

 descriptive name. 



