GREEN FLUORESCENT BACTERIA FROM WATER 77 



characteristic must be improved, however, in order that compar- 

 able results may be secured by workers from the different labora- 

 tories. Diagram I indicates the incidence of gelatin liquefac- 

 tion, among the strains studied. 



Growth in nutrient broth 



Good growth was secured with all strains when grown in 

 nutrient broth at 37 °C. The medium was practically always 

 cloudy, with a pellicle and sediment. Varying degrees of fluo- 

 rescence were manifested by the cultures. A few were viscid' 

 and strung out when a platinum needle was used. This has 

 been mentioned above under the head of Staining Properties. 

 The growth in nutrient broth was not especially characteristic. 



Indol formation 



A 1 per cent solution of Witte's peptone was used in this test. 

 The tubes were inoculated from a twenty-four-hour broth cul- 

 ture and were incubated at 37°C. for ten days. At the end of 

 this incubation period, 1 cc. of paradimethylamidobenzaldehyde 

 was added to the culture tube. None of the cultures formed 

 indol. With the strains which produced a large amount of 

 fluorescent pigment a red color was very often secured, but this 

 was not due to indol since the culture tubes did not have the 

 characteristic odor of putrefaction. This red color may have 

 been due to the pigment. 



Formation of hydrogen sulfide 



To study this characteristic, a special medium prepared by 

 Redfield (1912) was used. This was made by adding 300 grams 

 of Witte's peptone and 75 grams of potassium chloride to 700 cc. 

 of boihng tap water. This mixture was heated to dissolve as 

 much peptone as possible, and the solution was then cooled and 

 diluted, to 1 liter. It was again boiled, plugged with cotton 

 and allowed to stand in an ice box for at least twenty-four hours. 

 At the end of this time the medium was filtered and transferred 

 to special flasks used in the routine analysis of water. 



