Decomposition of Glucose and Mannitol by B. coli communis. 473 



by one enzyme, unless these two substances can replace one another to a 

 certain extent owing to secondary reactions. 



Isolation of the Organism. 



B. coli communis (Escherich) was chosen for this work since the first 

 observations made by Penfold (1911) on the disappearance of the gas- 

 producing power by growth in the presence of sodium chloroacetate were 

 made with this organism. It was found, however, that very many strains 

 of B. coli communis could be isolated, showing not only differences in degree 

 (which need not be considered here), but also of kind. 



The organisms were isolated from human faeces in the ordinary way. A 

 broth culture was made and from this bile salt cane-sugar neutral red agar 

 plates were inoculated ; after incubation for one or two days at 37°, a 

 number of white colonies (cane-sugar non-fermenters) were removed to tubes 

 containing lactose peptone water coloured with litmus, and provided with 

 Durham gas tubes. Those tubes which on incubation produced acid and gas 

 (lactose fermenters) were iased to inoculate a series of tubes containing 

 dulcitol peptone water. By these three operations organisms were obtained 

 which according to MacConkey (1905) belonged to the B. coli communis 

 (Escherich) group. The general characteristics of the four varieties which 

 were found will be seen by reference to Table L 



Table I. — Characters of Strains of B. coli communis occurring together in 



Normal Fseces. 



Motility. 



Indole pro- 

 duction. 



Milk 

 clotting. 



Fermentation of sugars, etc. 



Glucose. 



Lactose. 



Mannitol. | Cane-sugar. 



1. Rapid 



2. Slight 



3. Slight 



4. Rapid 



Strong 

 Medium 

 Strong 

 Nil 



24 hrs. 

 24 „ 



5 days 

 24 hrs. 



A, G 

 A, G 

 A, G 

 A, G 



A, G 

 A, G 

 A, G 

 A, G 



A, G 

 A, G 

 A, G 

 A, G 



Nil 

 Nil 

 Nil 

 Nil 



A = acid. G = gas. 



All the above strains were Gram negative, did not liquefy gelatin and did 

 not give the Voges and Proskauer reaction. Very many examinations were 

 made of the motility in from 3 to 10 hours' cultures. 



The most striking difference is that between the rapidly motile 

 No. 1 and the practically non-motile No. 2. These were chosen, therefore, 

 for further study, since it seemed possible that the motile organism might 

 differ considerably in its metabolism from that which was slightly motile. 



2 N 2 



