696 ORDER V. ACTINOMYCETALES 



ultraviolet light (Richards, Chapter on Fluorescent Microscopy, in Analytical Cytology, 

 ed. by R. C. Mellors, New York, 1953). 



The members of this genus are arranged as a natural spectrum, starting with the sapro- 

 phytes (some of which may be potentially parasitic) and proceeding through the tubercle 

 bacilli to the highly host-dependent leprosy bacilli. 



The tj-pe species is Mycobacterium tuberculosis (Zopf) Lehmann and Neumann. 



Key to the species of genus Mycobacterium. 



I. Saprophytes, including potential parasites; grow rapidly on most media at 28° C. 

 Strains recovered from tuberculosis of cold-blooded animals and from ulcers, skin le- 

 sions and other infections in mammals tend, after artificial cultivation, to be indistin- 

 guishable from the saprophytes found in soil, water, plants, etc. Cells acid-fast when 

 grown under proper conditions. 



A. Growth at 45° C* 



1. Growth at 52° C; no acid from rhamnose or inositol. 



1. Mycobacterium phlei. 



2. No growth at 52° C; acid from rhamnose and inositol. 



2. Mycobacterium smegmatis. 



B, No growth at 45° C. 



3. Mycobacterium fortuitum,. 



4. Mycobacterium, marinum. 



5. Mycobacterium thamnopheos. 



6. Mycobacterium platypoecilus . 

 II. Parasites on warm-blooded animals. Cells usually acid-fast. 



A. Growth on ordinary or special media. 



1. No growth at temperatures above 33° C; not pathogenic for guinea pigs or rab- 

 bits, experimentally produces cutaneous lesions in rats and mice; causes ulcerous 

 lesions on the lower extremities of man. 



7. Mycobacterium ulccrans. 



2. Growth at 37° C. 



a. Slow growth on all media. 



b. Experimentally produces generalized tuberculosis in guinea pigs. 



c. Experimentally does not produce generalized tuberculosis in rabbits 

 or fowls. Growth enhanced by the addition of glycerol to most me- 

 dia. Generally pale yellow to orange pigmentation, especially on 

 media containing serum. 



8. Mycobacterium tuberculosis. 



cc. Experimentally produces generalized tuberculosis in rabbits but not 

 in fowls. Growth not enhanced by the addition of glycerol to media. 

 Not pigmented. 



9. Mycobacterium bovis. 



bb. Experimentally does not produce generalized tuberculosis in guinea pigs, 

 c. Experimentally produces generalized tuberculosis in voles, but not 

 in rabbits or fowls. 



10. Mycobacterium microti. 



cc. Experimentally produces generalized tuberculosis in fowls. 



11. Mycobacterixim avium. 



aa. Growth in primary cultures only when heat-killed, acid-fast bacteria or ex- 

 tracts of acid-fast bacteria are added to the media. Experimentally fails to 

 infect guinea pigs or fowls. 



12. Mycobacterium paratuberculosis . 



* All temperatures above 37° C. are water-bath temperatures. 



