GREEN FLUORESCENT BACTERIA FROM WATER 79 



The method here used was a modification of Redfield's, be- 

 cause the flasks used by him in routine water analysis could 

 not readily be adapted to the study of pure cultures. In his 

 method, 10 cc. of his special medium were diluted to 100 cc. in a 

 special flask with 90 cc. of the sample under investigation. This 

 flask was fitted with a ground glass stopper which held the lead 

 acetate paper. In order to adapt this medium to the study of 

 pure cultures, it was made up one-tenth as strong as given above 

 and put into a test tube fitted with a one-hole rubber stopper 

 carrjdng a piece of glass tubing. A strip of lead acetate paper 

 was held in this tube by means of cotton. Tin foil was twisted 

 about the end of the glass tube. After inoculation from a 

 twenty-four hour cultiu-e the tubes were incubated at 37°C. for 

 thirty days. At the end of this period darkening of the paper 

 indicated hydrogen sulfide formation. 



Some of the strains studied in this series produced large 

 amounts of hydrogen sulfide. Strains 12, 19, 23, 30, 43, 45, 47, 

 48, and 52, produced sufficient hydrogen sulfide at 37°C. in 

 much less time than thirty days to darken 2 cm. of a strip of 

 paper 25 by 2 mm. Forty-six of the cultures produced hydro- 

 gen sulfide from Redfield's medium. 



Redfield has collected the names of the bacteria which have 

 been reported to produce hydrogen sulfide. The following 

 fluorescent bacteria are included. 



In two days, Bacillus fiuorescens-non-liquefaciens; in three 

 days. Bacillus pyocyaneus; in ten days. Bacillus fluorescens- 

 liquefaciens; in ihiviy days. Bacillus cyanogenus (Fluorescent?); 

 in varying lengths of time, Bacterium immobile, Pseudomonas 

 fiuorescens (Fliigge), Pseudomonas pilocyanea. 



Edson and Carpenter secured hydrogen sulfide formation in 

 20 of the 42 cultures which were isolated from maple sap. This 

 gives a percentage of approximately 48, while that obtained 

 with our cultures from water was 46 per cent. The method of 

 Edson and Carpenter consisted in suspending a strip of lead 

 acetate paper above an ordinary broth culture. From these 

 two investigations it would seem that plain broth was about as 

 efficient as Redfield's medium for observing the formation of 



