SOIL ACTINOMYCES 



291 



by Lieske was due to the use of non-synthetic nutrient agar, which is 

 variable in composition. Two media made up exactly alike, but 

 differing merely in the amount of boiling, period of sterilization, a 

 slight change in ratio between the carbon and nitrogen sources, or in 

 reaction and concentration of nutrients, will show distinctive differences 

 for the various organisms. By growing these on synthetic media, 

 with due allowance to variability, certain definite characters may be 

 established. 



Methods of study. For determining the abundance of actinomyces 

 in the soil, the general media used for the determination of numbers of 

 bacteria can be employed (p. 16). For the study of cultural and 

 morphological characters, several media have been suggested: 



Glucose agar: 5 



10 grams glucose 

 0.5 gram K 2 HP0 4 

 0.5 gram asparagine 



15 grams agar 

 1000 cc. distilled water 

 Malate-glycerin agar: 5,7 



10 grams calcium malate 

 0.5 gram NH 4 C1 

 0.5 gram K 2 HPO« 

 10 grams glycerin 

 15 grams agar 

 1000 cc. distilled water 

 Reaction adjusted by means of 



NaOH to pH = 7.0 

 Citrate-glycerin agar: 7 

 Same as 2, except that calcium 

 citrate is used in place of 

 malate 



4. Czapek's agar: 6 

 2 grams NaN0 3 

 1 gram K 2 HP0 4 



0.5 gram MgS0 4 

 0.5 gram KC1 

 0.01 gramFeSO, 

 30 grams sucrose 

 15 grams agar 

 1000 cc. distilled water 



5. Starch agar: 6 

 10 grams starch is suspended in 



800 cc. of water and boiled 

 down to 500 cc. 500 cc. 

 water to which are added 1 

 gram K 2 HP0 4 , 1 gram 

 MgS0 4 , 1 gram NaCl, 2 grams 

 (NH 4 ) 2 S0 4 , 3 grams CaC0 3 , 

 10 grams agar. The two solu- 

 tions are mixed and tubed. 



6. Gelatin: 



15 per cent Gold Label gelatin 

 in distilled water. 



The first four media are used for the study of general cultural characters of 

 the organisms and are well suited for morphological studies; the starch and 

 gelatin media supply information on two of the most important physiological 

 properties of the organisms, namely the diastatic and proteolytic. 



For microscopic examinations, one of the two following methods may 

 be used: 



1. Method of Henrici: 19 Melted and cooled agar is inoculated with the specific 

 organism and spread in a thin film on flamed slides, which are then incubated in 



19 Personal communication. 



