PROSPECTS FOR A NATURAL SYSTEM OF CLASSIFICATION OF BACTERIA 



diagnosis of the order as outlined in Bergey's manual. It is therefore 

 perplexing to find in the family Mycobacteriaceae Gram-negative as well 

 as motile organisms. Any one isolating an organism answering the 

 diagnostic requirements of the genera Mycoplana, Cellvibrio and Actino- 

 bacillus would not hesitate a moment to include his organism in the 

 order of the Eubacteriales. 



A similar example is furnished by the species Leptothrix hyalina 

 which, although it is stated not to form a sheath, is incorporated in 

 the order of the Chlamydobacteriales regardless of the fact that in the 

 key to the orders the occurrence of a sheath is decisive for including the 

 organism in the order in question. 



As for the next order, Thiobacteriales, we will only state that here, in 

 contradistinction to what holds for the foregoing orders, morpho- 

 logical characters are fully left out of consideration in delimiting the 

 order. The essential metabolic function of the sulfur or (and) the 

 photosynthetic activity with the aid of the bacteriopurpurin pigment 

 complex serve to characterize the order. Considered from this point of 

 view it is rather surprising that the genus Thiobacillus is not included 

 in this group. 



With these comments on one of the most widely used systems the 

 deplorable present state of bacterial classification is sufficiently illus- 

 trated. 



During the course of the development of the American system a 

 number of important studies on bacterial taxonomy appeared. One 

 of the most outstanding contributions to a solution of the problem is 

 undoubtedly the paper by Pringsheim [1923]. This publication con- 

 tains several very sound general considerations on the principles of 

 taxonomy with corresponding critical remarks on the previously pro- 

 posed systems. We will confine ourselves to a brief review of the scheme 

 as advocated by the author. Then we meet with a first subdivision of 

 the bacteria into five orders, each one of which may be called homo- 

 geneous and homologous. 



The principal feature of Pringsheim's subdivision of the first order, 

 Eubacteriales, is unquestionably the fact that the usual, somewhat 

 primitive, classification on the basis of spheres, rods and spirals is not 

 strictly maintained inasmuch as the Spirillaceae also include the rod- 

 shaped bacteria with polar fiagella, i.e. the genus Pseudomonas Migula. 

 The natural affinities of the representatives of this genus to those of the 



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