GREEN FLUORESCENT BACTERIA FROM WATER 85 



was taken. By that time a constant reaction had been estab- 

 hshed, and continued incubation simply increased it in the same 

 direction. 



Growth in litmus milk 



This medium was prepared after the same method that was 

 used in the preparation of plain milk. KahJbaum's azolitmin 

 was used as the indicator. The milk was inoculated from a 

 twenty-four-hour broth culture by means of a platinum loop, 

 and incubated at 37°C. for twenty-five days. A detailed ac- 

 count of all the changes in this medium will not be included. 

 In many cases the tubes turned alkaline at the surface and the 

 blue color gradually extended downward until the whole tube 

 was changed. When peptonization occurred this continued 

 until the whole tube had turned to an orange color. 



Many of the strains possessed no proteolytic enzyme and thus 

 produced no change in plain milk. Some of the strains formed 

 alkali which soon gave way to a permanent acid. In many 

 cases the curdling of the milk could not be entirely explained 

 by the concentration of the acid. It was doubtless due to the 

 presence of a rennin-like enzyme. 



Pe'ptonization of casein 



With most of the strains casein peptonization was apparent 

 in the flasks used in the titration of the acidity of milk, but with 

 the others it was impossible to tell whether the casein was at- 

 tacked. In order to determine this character, Hasting's (1904) 

 milk agar was used. This was prepared by cooling a tube of 

 melted agar and adding to it 1 cc. of sterile skimmed milk. This 

 was then poured into a sterile Petri dish and thoroughly stirred. 

 When solidified, it was inoculated bjy making streaks on the 

 surface, after which the plates were incubated for five days at 

 37°C. A clear zone appeared around the line of inoculation on 

 those plates which were inoculated with the strains capable of 

 peptonizing the casein. To verify this conclusion, dilute acetic 

 acid was added to the plate, and if the zone remained clear the 

 strain was recorded as one which would peptonize. 



THE JOURNAL OF BACTERIOLOGT, VOL. Ill, NO. 1 



