298 PRINCIPLES OF SOIL MICROBIOLOGY 



on the plate; the form of the crystals depends on the nature of the fat 

 used. Some actinomyces can utilize rubber as a source of carbon. 30 

 Lantzsch 31 isolated an Actinomyces growing in distilled water contain- 

 ing quartz or in a medium very poor in organic matter; this organism 

 was found to be identical with Bac. oligocarbophilus of Beijerinck and it 

 could assimilate CO as well as the higher aliphatic hydrocarbons, except 

 benzol and xylol. 



Actinomyces are among the very few organisms in nature which are 

 capable of utilizing lignins and soil "humus" as sources of carbon. This 

 can be readily demonstrated both in liquid media and by the use of 

 silica gel plates. 32 



Nitrogen utilization. Proteins form good sources of nitrogen, the 

 same is true of peptones and various amino acids. Gelatin (15 per cent 

 in distilled water, neutralized or reaction unadjusted) is liquefied 

 in 3 to 5 days, at 18° to 20°C, but some species will produce only a very 

 narrow liquefied zone after 30 to 40 days. Some do not form any pig- 

 ment, others form a brown to purple-brown soluble pigment on the gela- 

 tin. A number of species can also hemolyze red blood cells and produce a 

 clear zone around the colony when grown on blood agar. The acti- 

 nomyces can be divided into several groups on the basis of milk 

 coagulation. 33 



1. Rapid coagulation of milk, followed by rapid liquefaction of the coagulum, 

 so that the tube of milk becomes clear in 6 to 7 days. 



2. Rapid coagulation of the milk followed by slow liquefaction. 



3. Slow coagulation followed by a rapid liquefaction. 



4. Digestion of the milk proteins without any previous coagulation. This 

 tends to indicate that the rennet-like and proteolytic enzymes are distinct. 



Among the inorganic compounds, ammonium salts are utilized well, 

 especially in the presence of sufficient buffer, especially silicates. 34 The 

 same is true of nitrates; they are reduced first to nitrites before they 

 are assimilated. Nitrites themselves, when used in very low concen- 



30 Sohngen, N. L., and Fol, J. G. Die Zersetzung des Kautschuks durch 

 Mikroben. Centrbl. Bakt. II, 40: 87-98. 1914. 



31 Lantzsch, K. Actinomyces oligocarbophilus (Bacillus oligocarbophilus 

 Beij.), sein Formwechsel und seine Physiologic Centrbl. Bakt. II, 57: 309-319. 

 1922. 



32 Unpublished data. 



33 Waksman, S. A. Studies in the metabolism of actinomycetes. I. Jour. 

 Bact., 4: 189-216. 1919. 



34 Miinter, F. Uber Stickstoffumsetzungen einiger Aktinomyceten. Centrbl. 

 Bakt. II, 39: 561-583. 1914. 



