133 



substantial treatise on the acetic acid bacteria was published by Ho- 

 YER who had been working on this subject under Beijerinck's super- 

 vision i). 



Both Hoyer's and Beijerinck's pubhcationshave, as central featu- 

 re, the idea that the various acetic acid bacteria constitute a natural 

 group, and should, therefore, be sharply differentiated from the 

 numerous other sporeless, rod-shaped bacteria which also have an 

 oxidative metabolism. In this respect the ability of the acetic acid 

 bacteria to produce in suitable media high amounts of acid is a decis- 

 ive characteristic ; this property is accompanied by an adaptation to 

 life in acid culture media. For this reason it is surprizing that neither 

 Beijerinck nor Hoyer proposed in their publications the creation of 

 a new genus for the acetic acid bacteria. At least they neglected to do 

 so formally, but there is sufficiënt evidence that soon afterwards 

 Beijerinck introduced the generic name Acetohacter 2) into his con- 

 versations and private correspondence. In various papers which ap- 

 peared shortly af ter 1898, the name Acetohacter is used without any 

 further explanation 3). There can be no doubt that in any case morally, 

 but probably also according to the letter of the code of Botanical 

 Nomenclature, Beijerinck is to be considered as the author of the 

 genus Acetohacter, as it occurs in most of the recent bacterial systems. 



Another characteristic element in both Beijerinck's and Hoyer's 

 publications was the tendency to restrict as much as possible the 

 number of the species to be distinguished within the group. Both 

 authors were fully aware that a systematic study of the group leads to 

 the isolation of numerous non-identical strains, but since these differ- 

 ences are often limited to characters of minor importance, the authors 

 emphasized the necessity of distinguishing only a small number of 

 species which may then each embrace a certain number of varieties. A 

 more general application of this principle in bacterial classification 

 would have saved this science from much confusion. For the acetic 

 acid bacteria the result was that only four species — B. aceti, B. 

 rancens, B. Pasteurianum and B. xylinum — were recognized and 

 clear differential characters were given for each. 



In this respect special mention may be made of the important ob- 

 servation that, in contradistinction to other species, the organism 

 active in the quick acetification process, Bacterium aceti, is able to 

 proliferate in a medium containing acetate and ethyl alcohol with 

 ammonium phosphate as the only nitrogen source. Since then this 

 medium, unchanged or only slightly modified, has been used for 



1) D. P. Hoyer, Bijdrage tot de kennis van de azijnbacteriën. Delft, 1898. - 



2) Initially: Acetohacterium. 



3) The first instance of this generic name in a printed publication we have been able 

 to tracé is to be found in a footnote in the paper on indigo fermentation published in 

 Proc. Kon. Akad. v. Wet. Amsterdam 2, 495, 1900. A second example occurs m the 

 paper on the lactic acid bacteria in industry published^in Arch. néerl. d. sciences ex- 

 actes et naturelles Sér. II, 6, 212, 1901. 



