24 LABORATORY MANUAL OF MICROBIOLOGY 



Tube the agar in 10-cubic centimeter portions and sterilize. 

 To this melted agar, at 45°C. in tubes or Petri dishes, add 1- 

 cubic centimeter portion of the following salts. 



1. Dipotassium phosphate (K2HPO4) 1.5 gm. 



Water 100.0 cc. 



2. Ammonium sulphate ((NH4)2S04) 1.5 gm. 



Magnesium sulphate (MgS04-7H20) 0.75 gm. 



Ferric sulphate (Fe2(S04)3-9H20) 0.02 gm. 



Water 100.0 cc. 



3. Sodium chloride (NaCl) 3.0 gm. 



Sodium carbonate (Na2C03) 1.5 gm. 



Tap water 100.0 cc. 



4. Sodium nitrite (NaN02) 1.5 gm. 



Sodium carbonate (Na2C03) 1.5 gm. 



Water 100.0 cc. 



5. Magnesium sulphate (MgS04-7H20) 0.45 gm. 



Sodium chlorid (NaCl) . 75 gm. 



Ferric sulphate (Fe2(S04)3-9H20) 0.02 gm. 



Water 100.0 cc. 



For ammonia oxidation add 1 cubic centimeter of the stock 

 solutions numbers 1, 2, and 3, to 10 cubic centimeters of the 

 melted agar. 



For the nitrite oxidation, add 1 cubic centimeter of stock 

 solutions numbers 1, 4, and 5. 



Agar media prepared in this way should remain clear. 



Medium 54 

 SiLicio AoiD Gel for Nitrite-forming Bacteria 



Prepare a series of silica-gel plates, according to the method 

 outlined on p. 6. To each plate add 2.5 cubic centimeters of 

 the medium (a), 1 cubic centimeter of medium (6), 1 drop of 

 (c) and a few drops of (d) to give a milky appearance. Mix 

 the solutions and place the open plates in incubator, at 60°C., 

 to evaporate excess of surface liquid. 



(a) Ammonium sulphate ((NH4)2S04) 1.5 gm. 



Dipotassium phosphate (K2HPO4) 0.5 gm. 



Magnesium sulphate (MgS04-7HoO) . 25 gm. 



Distilled water 100.0 cc. 



(6) Ferrous sulphate (FeS04-7H20) 1.0 gm. 



Distilled water 100 . cc. 



(c) Saturated sodium chloride solution. 



(d) A suspension of powdered MgC03 in distilled water. 



