32 



III. CLASSIFICATIONS OF THE COLON GROUP 

 OF BACTERIA. 



Several attempts have been made to classify the numerous organisms 

 of the colon group for the most part on the basis of acid and gas produc- 

 tion from various carbohydrates. The reliability of such studies is some- 

 times questioned on the ground that fermentation reactions are inconstant 

 and may be easily acquired -or lost. 



Smirnow grew colon strains in media containing various chemicals 

 (3.0% glucose, 4.0% sodium chloride, 0.5% sodium sulphate, and 0.25 to 

 0.75% phenol) and found that after successive transfers, for periods of one 

 to three months, indol formation and later fermentation of carbohydrates 

 were suppressed. Reversion to the original characteristics took place rapidly, 

 however, when grown on ordinary media. 



Bronfenbrenner and Davis found colon organisms in food which fer- 

 mented lactose slowly when first isolated but after cultivation on lactose 

 media the rate of decomposition of this substance became normal. 



Twort, Penfold, and others, observed spontaneous mutations such as 

 the loss or acquistion of the ability to ferment various carbohydrates. 



After a careful survey of the data on biological variations and muta- 

 tions, Winslow concludes that "Taking the great mass of colon typhoid 

 strains, as they are isolated from the bodies or intestines of man and 

 animals, and cultivated under standard conditions, fermentative character- 

 istics exhibit a high degree of constancy and what is even more important 

 a higher degree of correlation with other biochemical and serological and 

 pathogenic properties." 



From the practical water analysis view point, we are especially in- 

 terested in the effect of a long sojourn in water or soil on the biological 

 activities of Bact. coli. 



Houston repeatedly found that the proportion of strains not forming 

 indol was much greater among those isolated from purified than from 

 raw waters. He thought this was due to a loss of indol producing power 

 as a result of unfavorable conditions encountered in water. He speaks 

 of such indol negative forms or strains, which differ from the supposedly 

 original Bact. coli commune, as "atypical" Bact. coli. 



Horrocks in 1903 exposed Bact. coli in various types of soils and 

 waters for two to three months, and Savage in 1905 observed the effect 

 of tidal mud. They came to the conclusion that alterations in character- 

 istics were not induced and that there was no evidence that Bact. coli ever 

 becomes "atypical." 



MacConkey placed a broth culture of Bact. coli in a sterile Pasteur 

 candle which was then suspended in tap water. The water was changed 

 occasionally. Fact, coli was isolated from the candle at irregular inter- 

 vals up to 358 days and examined biologically and biochemically. In 

 no instance was a loss or gain of a character detected. 



It seems that the remarkable facts are not that an organism may oc- 

 casionlly show a biological variation, but that, considering the simplicity 

 of the bacterial cell, such variations are so infrequent. 



