196 PRINCIPLES OF SOIL MICROBIOLOGY 



filamentous cell (3 to 10 by 0.3 to 0.4/z), which appears to go through 

 a number of phases terminating in the production of a spherical body 

 (sporoid). This differs in a number of respects from the true spores of 

 bacteria; germination of the sporoid again gives rise to the filamentous 

 form which possesses perfect flexibility and is feebly motile although 

 no flagella were observed. 



The organism is aerobic, with an optimum at 30°C, and is destroyed when 

 kept at 60°C. for ten minutes. It does not grow in nutrient agar or gelatin, and 

 is injuriously affected by concentrations of peptone above 0.025 per cent. As 

 sources of nitrogen, ammonium salts, nitrates, amides and amino acids can be 

 used, while cellulose is the only source of carbon. The soluble carbohydrates 

 are more or less toxic. The following medium was used for the isolation and 

 cultivation of the organism: 



K 2 HP0 4 1.0 gram Fe 2 Cl 6 0.01 gram 



CaCl 2 0.1 gram NaN0 3 2.5 grams 



MgS0 4 0.3 gram Cellulose 10. grams 



NaCl 0.1 gram H 2 1000 cc. 



The same organism was found to occur in the soil and to decompose 

 cellulose readily. 14 By the use of the silica gel method suggested by 

 Winogradsky, the Sp. cytophaga can be shown to be very abundant in 

 the soil, especially soils receiving applications of farmyard manure and 

 straw. 15 



The gel is prepared by placing a mixture of equal parts of a normal solution 

 of HC1 and its equivalent of potassium silicate solution into Petri dishes. After 

 the gel has formed, the dishes are placed in running tap water for 24 hours, then 

 several times in boiled distilled water until free from chlorides. Five grams of 

 ground filter paper are then suspended in 100 cc. of medium containing 5 grams 

 (NH 4 ) 2 HP04, 1 gram MgS0 4 , 1 gram KC1, 0.02 gram FeS0 4 , in 1000 cc. distilled 

 water; about 2 cc. portions of the suspension are spread over the surface of each 

 plate and a small amount of CaC0 3 is dusted on. The plates are then placed 

 in the thermostat at 60°C, until the surface of the gel becomes free from excess of 

 liquid. Small particles of soil can then be inoculated directly upon the plate 

 which is then covered and incubated. After 2 to 4 days, yellow and orange 

 growth will be found to develop from the soil into the medium. Transfers are 

 then made into flasks containing 1 gm. of filter paper and 25 cc. of above solution. 

 The organisms will begin to develop in the form of yellow specks, forming a yellow 

 slimy mass all over the paper in 2 to 4 days. By repeated dilutions, the organism 

 can be isolated pure. 



14 Lohnis, F., and Lochhead, G. Experiments on the decomposition of cellu- 

 lose by aerobic bacteria. Centrbl. Bakt. II, 58: 430^34. 1923. 



15 Waksman, S. A., and Carey, C. On the use of the silica gel plate for the 

 isolation of cellulose-decomposing bacteria. Jour. Bact. 12: 87-95. 1926. 



