on the life cycle of bacteria, that a single species of Azotobacter may pass 

 through as many as twelve to fourteen morphological forms including 

 spores, is not particularly relevant with respect to Bad. coli, the life cycle 

 of which has been carefully studied by Kellerman and Scales who note 

 specifically that spores were not observed. It is conceivable that unfavor- 

 able environment may lead to spore formation by members of the colon- 

 jerogenes group but the writer has never encountered nor heard of such 

 a transformation, although he has observed a large number of cultures 

 kept under various unfavorable conditions, nor does he anticipate such a 

 fundamental and radical change in form. 



These spore forming, aerobic, lactose fermenters confuse the ordin- 

 ary tests for Bact. coli and must be taken into consideration in interpreting 

 water analyses, just as it is essential to differentiate the anaerobic spore 

 forming lactose fermenters which confuse, the presumptive test for Bact. 

 coli, but there is no logical reason nor justification for placing them in the 

 colon group. 



Clark and Lubs raise the question as to the reliability of lactose fer- 

 mentation as a primary criterion. They say, "If a fundamental cultural 

 requirement of the members of the colon-aerogenes family is that it shall 

 ferment lactose, there is imposed the same sort of requirement for the 

 characterization of a whole family as is imposed by the MacConkey scheme 

 when groups within the family are separated on the basis of the fermentation 

 of another sugar, sucrose." 



They point out that the fermentation of sucrose, which was formerly 

 employed to subdivide the colon group into species and varieties (Mac- 

 Conkey's scheme), has been found less desirable than differentation on 

 more recently devised tests, such as the gas ratio, the methyl -red reaction, 

 and the Voges Proskauer test. They raise the question as to whether it is 

 not possible that in the near future a test may be discovered which will 

 supplant lactose fermentation as the salient and fundamental requirement 

 for the whole colon-aerogenes family. We may well agree with Clark and 

 Lubs that the future holds out to us promises of improved differential 

 tests but we do not feel that, in consequence, we shall not utilize such 

 means as are now available. Surely the classification of the organisms of 

 this group to the best of our abiltiy on tests which are now known and 

 used, would simplify a reclassification when these more fundamental, and 

 we hope more reliable reactions of the future are brought out. The fact 

 remains that the fermentation of lactose has been successfully employed 

 for the separation of the non-pathogenic colon group from the disease pro- 

 ducing para-typhoid and typhoid groups. Until a test is developed which 

 will adequately supplant this, the fermentation of lactose with acid and 

 gas production is considered a convenient and reasonably reliable criterion 

 for members of the colon group of bacteria. 



The colon group will therefore be considered to include non-sporing, 

 Gram negative bacilli which ferment lactose with the production of acid 

 and gas and which are capable of growing aerobically. The statement 



