42 PHARMACEUTICAL BACTERIOLOGY 



pounds of nitrogen. Produce nodules upon the roots of leguminous 

 plants, 1 



The type species is Rhizobium leguminosarum Frank. 



II. Family MYCOBACTERIACE.E Chester, 1897. Cells usually elon- 

 gated, frequently filamentous and with a decided tendency to the develop- 

 ment of branches, in some genera giving rise to the formation of a definite 

 branched mycelium. Cells frequently show swellings, clubbed or irregu- 

 lar shapes. Endospores not produced, but conidia developed in some 

 genera. Usually Gram-positive. Non-motile. Many species are para- 

 sitic in animals or plants. Complex proteins usually required. As a 

 rule strongly aerobic (except for some species of Actinomyces and the 

 genera Fusiformis and Leptotrichia) , and oxidative. Growth on culture 

 media often slow; some genera show mold-like colonies. 



1. Actinomyces. Harz, 1877. Synonyms: Streptothrix Cohn 1875, 

 not Streptothrix Cor da 1839; Discomyces Rivolta and Micellone 1878; 

 Micromyces Gruber 1891, not Micromyces Dangeard 1888; Ob'spora Sauva- 

 geau and Radais 1892; not Ob'spora Wallroth 1833; Cohnistreptothrix 

 Pinoy 1913. 



Organism growing in form of a much-branched mycelium, which may 

 break up into segments that function as conidia. Usually parasitic, with 

 clubbed ends of radiating threads conspicuous in lesions in animal body. 

 No earial hyphae or conidia. Some species are microaerophilic or anae- 

 robic. Non-motile. 



The type species is Actinomyces boms Harz. 



2. Nocardia. Trevisan, 1889. Synonyms: Actinomyces of many 

 authors; Streptothrix of many authors; Thermoactinomyces Tsilinsky 

 1899. 



Branched filaments, resembling a mycelium, readily breaking up into 

 segments, usually saprophytic soil forms. Differs primarily from Acti- 

 nomyces in the development of aerial hyphae and conidia. Usually 

 aerobic. Many are pigment formers. Colonies as a rule mold-like on 

 culture media. 



3. Mycobacterium. Lehmann and Neumann, 1896. Synonyms: 

 Sclerothrix Metschnikoff 1888, not Sclerothrix Kuetzing 1849; Coccothrix 

 Lutz 1886; Mycomonas Jensen 1909. 



Slender rods which are stained with difficulty, but when once stained 

 are acid-fast. Cells sometimes show swollen, clavate or cuneate forms, 

 and occasionally even branched filaments. Non-motile, Gram-positive. 

 No endospores. Growth on media slow. Aerobic. Several species 

 pathogenic to animals. 



1 True nodule forming bacteria occur in the shrub Ceanothus integerrimus and 

 probably ether non-leguminous plants. Author. 



