184 DIFCO MANUAL 



merit of a distinct yellow color in the lower portion of the tube, the surface zone 

 remaining red. 



To rehydrate the medium, suspend 40 grams of Bacto-Phenol Red Tartrate 

 Agar in 1000 ml. of cold distilled water and heat to boiling to dissolve the 

 medium completely. The solution is distributed in tubes which are stoppered 

 with cotton plugs or loosely fitting caps. Sterilize in the autoclave for 15 minutes 

 at 15 pounds pressure (121°G.). Allow the tubes to cool in an unslanted position. 

 The medium will have a final reaction of pH 7.6. 



One pound of Bacto-Phenol Red Tartrate Agar will make 11.3 liters of 

 medium. 



^J. Hyg., 23:1:1924. ^ J. Infectious Diseases, 42:238:1928. 



BACTO 



MOTILITY TEST MEDIUM (B105) 



DEHYDRATED 



Bacto-Tryptose 10 g. 



Sodium Chloride 5 g. 



Bacto-Agar 5 g. 



Bacto-Motility Test Medium, a modification of the formula of Tittsler and 

 Sandholzer,^ as suggested by Darby,^ is a semisolid medium employed in the 

 testing of bacteria for motility. The sterile medium is inoculated by stabbing 

 through the center of the medium and is incubated at the proper temperature 

 for the organism under consideration and examined at the end of 8, 24 and 48 

 hours. Motility is manifested macroscopically by a diffuse zone of growth spread- 

 ing from the line of inoculation. Certain species of motile bacteria will show 

 diffuse growth throughout the entire medium, while others may show diffusion 

 from one or two points only, appearing as nodular outgrowths along the stab. 

 Tittsler and Sandholzer reported that tubes incubated for one day gave identical 

 results with the hanging drop method and that incubation for two days permitted 

 them to demonstrate motility in an additional 4 per cent of the cultures tested. 



Bacto-S I M Medium as discussed on page 173 is also recommended for 

 determination of motility. In addition to motility, hydrogen sulfide production 

 and the production of indole may be determined on Bacto-S I M Medium. 



To rehydrate the medium, suspend 20 grams of Bacto-Motility Test Medium 

 in 1000 ml. of cold distilled water and heat to boiling to dissolve the medium 

 completely. Distribute in tubes and sterilize by autoclaving for 15 minutes at 

 15 pounds pressure (121°G.). Allow the medium to cool with the tubes in an up- 

 right position. The medium will have a final reaction of pH 7.2. 



One pound of Bacto-Motility Test Medium will make 22.7 liters of medium. 



*J. Bact.j 31:575:1936. 2 Personal Communication. 



BACTO 



NITRATE BROTH (B268) 



DEHYDRATED 



Bacto-Beef Extract 3 g. 



Bacto-Peptone 5 g. 



Potassium Nitrate 1 g. 



Bacto-Nitrate Broth is recommended for testing the ability of bacteria to reduce 

 nitrate to nitrite, a characteristic which often has differential value. The medium 



