ACTINOMYCES 363 



The biochemical activities of the actinomycetes (Streptomyces) 

 have been extensively investigated by Waksman,^^ whose papers 

 should be consulted for detailed information. A wide variety of 

 organic substrates may be utilized by this group of microorganisms. 

 The simple sugars are readily utilized without fermentation, the 

 media generally becoming alkaline in reaction. Sucrose is rarely 

 inverted and is not a good source of carbon. Nearly all are actively 

 diastatic, breaking up starch with great rapidity. Many species 

 also split cellulose and some split agar-agar. Proteins are digested 

 by most species, gelatin, casein, and blood serum being liquefied. 

 Egg albumen, on the other hand, is not digested by most varieties. 

 Chitin is utilized by a number of species. The breaking down of 

 proteins to amino acids may proceed rapidly; the conversion of the 

 latter to ammonia takes place much more slowly and may com- 

 pletely fail with some species. Nitrates seem to be more readily 

 utilized than ammonium salts, possibly because utilization of ni- 

 trates makes the medium more alkaline, whereas utilization of 

 ammonia makes the medium more acid. The majority of species 

 can reduce nitrates to nitrites, but not to ammonia or free nitrogen. 

 Some species are hemolytic. A number of forms produce a rennin 

 coagulation of milk. Fat-splitting enzymes may be demonstrated 

 in a number of species. No work which bears critical chemical 

 scrutiny shows any nitrogen-fixing ability. Higher hydrocarbons 

 of the paraffin series are oxidized by several pathogenic and non- 

 pathogenic species. 



Actinomyces [sensu stricto). This genus is largely, if not ex- 

 clusively, parasitic, living on tooth surfaces, in carious teeth, and in 

 tonsillar crypts of man and probably of lower animals, and causing 

 infections under exceptional conditions. Only one species, Actino- 

 myces bovis may be recognized with certainty, although other species 

 are named. The use of the specific name Israeli for the causative 

 agent of common actinomycosis is incorrect unless it is shown that 

 bovine and human actinomycosis are caused by different species. 

 Present indications are that there is but one species. If Actinomyces 

 is accepted as a generic name, A. bovis must be the type species. The 

 outstanding characters, the intolerance of free oxygen, the rapidity 

 with which the mycelium fragments into arthrospores, the failure to 

 grow in the usual Sabouraud or other slightly acid media, make this 

 genus quite different from the other actinomycetes. The most im- 

 portant genus medically, and the one first named and studied ex- 

 tensively, it has been much misunderstood. For many years, cultures 

 labeled A. (or Streptothrix) hominis or A. bovis have been in culture 



