PROSPECTS FOR A NATURAL SYSTEM OF CLASSIFICATION OF BACTERIA 



In several instances this classification does not involve any difficulty, 

 because the energetic requirements of many bacteria can be met by 

 only one type of katabolic reaction. There are, however, also numerous 

 cases in which it is clear that the organism can derive its energy from 

 two or even more clearly distinct types of katabolism. This holds e.g. 

 for the so-called facultatively anaerobic bacteria which in the presence 

 of air are characterized by an oxidative katabolism (respiration), but 

 which, under anaerobic conditions, depend upon some special type 

 of fermentation. In those cases it is, of course, desirable to classify the 

 organism in question according to its most characteristic type of kata- 

 bolism, that is the type which permits the distinction from otherwise 

 related organisms. This implies that for organisms capable of develop- 

 ment under anaerobic conditions the katabolic process involved in 

 this mode of life has been determinative, regardless of the question 

 whether or not the organism also possesses a respiratory mechanism. 

 If two different types of anaerobic katabolism, e.g. saccharolytic and 

 proteolytic, are represented, the latter, as being the rarer, has been 

 decisive. 



In this way the system of classification represented in table I has 

 been obtained. 



The principles underlying this system would logically imply the 

 creation of new generic names for all actually occurring combinations 

 of fundamental morphological characters and special katabolic types. 

 Experience shows, however, that in the majority of cases the natural 

 groups obtained in this way coincide in all major points with various 

 genera recognized in the systems now in use, at the same time demon- 

 strating that our classificatory principles have, more or less unconsci- 

 ously, already been applied by many of our predecessors. In all these 

 cases we have, for practical reasons, maintained these current generic 

 names, although naturally the generic diagnoses had to be amended 

 more or less considerably. 



In a few instances we have rejected a current generic name, although 

 its diagnosis was sufficiently suited to justify its use. This was done 

 because the generic name in question might give rise to confusion as a 

 result of current nomenclature. Thus we have dropped the names 

 Thiobacillus and Rho do bacillus, since these names wrongly suggest that 

 they cover sporeforming bacteria. On analogous grounds we have 

 used the generic name Sulfospirillum instead of Thiospira. 



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