ASPARAGIN-DEXTROSE AGAR FOR SOIL BACTERIA 95 



1. Dissolve the agar in 900 c.c. of water by heating in 

 the steamer for one hour or longer. Add 100 c.c. of the 

 stock soil-extract solution. 



2. Add the dextrose just prior to tubing. 



3. The reaction should be (+0.5) or nearly neutral. 



Note. — Stock Solution of Soil Extract. — ^This is prepared by heating 1000 

 grams of garden soil with 1000 c.c. of tap- water in the autoclave at 5 to 10 

 pounds* pressure for thirty minutes. A small amount of calcium carbonate 

 is added and the whole is filtered through a double paper filter. The turbid 

 filtrate should be poured back on to the filter until it comes through clear. 



. Medium 7 

 Soil-extract Gelatin 



Gelatin 100 to 150 gm. 



Dextrose (CeHizOe) i gm. 



Soil extract 100 c.c. 



Water 900 c.c. 



1. Dissolve the gelatin in the diluted soil-extract solution 

 by heating slowly in the steamer. 



2. Clarify the medium with egg-albumen. 



3. Add I gram of dextrose and adjust the reaction to 



(+0.5). 



Conn, H. J., Bui. 38, N, Y. Agr. Exp. Sta., 1914. 



Medium 8 

 Asparagin-dextrose Agar for Soil Bacteria 



Agar 15.0 gm. 



Dibasic potassium phosphate (K2HPO4). 0.5 gm. 



Magnesium sulphate (MgS04 + 7H2O) 0.2 gm, 



Asparagin (C4H8N2O8 + H2O) i.o gm. 



Dextrose (C6H12O6) i.o gm. 



Distilled water looo.o c.c. 



