DESCRIPTION OF SPECIES 



451 



Biology : cultural characters {includ- 

 ing biocheynical features). 



Gelatine — Gelatine is slowly 

 liquefied, with formation of a white 

 surface pellicle. 



Potato — Sparse growth of dull 

 whitish appearance. 



Milk — Formation of surface 

 pellicle, ver>' resistant, and com- 

 posed of felted filaments. Light 

 coagulation ; the precipitate is 

 dissolved, and the liquid becomes 

 yellow and transparent. From the 

 first days of fermentation, the liquid 

 develops an odour similar to that 

 observed in cheese-maturing cellars. 

 The liquid is alkaline, containing 

 carbonate and butyrate of ammonia. 

 This last is gradually consumed 

 during the fermentation process. 

 Leucine and tjTosine are also 

 found in the liquid. 



Aerobic. 



Non-pathogenic. 



TYROTHRIX UROCEPHALUM 



(Duclaux). 



Source and habitat — Cheese. Wide- 

 spread in nature, "one of the princi- 

 pal agents of putrefaction in animal 

 matter." 



Morphology — Bacillus ; i m broad, 3 m 

 in length or more. Isolated in 

 pairs or united in long chains. 



Motility — Actively motile. 



Spore formation — Spherical spore 

 formation at one extremity. 



Biology : cultural characters {includ- 

 ing biochemical features). 



Gelatine — Gelatine stab-cultures; 

 at first a white growth along the 

 needle track followed by forma- 

 tion of gas bubbles right through 

 the medium. Liquefaction com- 

 mences late and proceeds slowly. 

 Formation of gas bubbles on sur- 

 face of liquid. 



Potato — Yellowish white shining 



growth, turning to a brown colour 

 with age. 



Milk — Surface formation of small 

 transparent gelatinous particles 

 which may invade the whole mass, 

 without, however, making it of a 

 gelatinous consistency. After some 

 time the milk liquid becomes 

 muddy with a thick flocculent 

 deposit formed chiefly of spores. 

 Disengagement of gas when culture 

 is made in CO.2, the liquid having 

 disagreeable garlic - like flavour 

 when there is entire absence of 

 oxygen. 



Anaerobic or aerobic — Faculta- 

 tive anaerobic, but develops better 

 in the absence of free oxygen. 



Vitality — The organism is killed 

 between 90° C. and 95° C. The 

 spores perish at from 100° C. to 

 105° C. in a neutral liquid ; at from 

 95° C. to 100° C. in a liquid 

 slightly acid. 



TYROTHRIX VIRGUIiA 



(Duclaux). 



Source and habitat — Cheese. 

 Morphology — Bacillus ; 5 /x broad, about 

 2 /x long. Isolated, or in chains 

 composed of a small number of 

 elements. 

 Motility — Non-motile. 

 Spore fomuition — Spores form at one 

 extremity ; spherical and the same 

 size as the mother cell. 

 Biology : cultural characters {includ- 

 ing biochemical features'). 



Bouillon — Grows well in 

 bouillon. 



Gelatine — Grows with difficulty 

 in gelatine. 



It plays a role in the maturation 

 of cheese, but only after other 

 organisms have prepared a 

 pabulum for it. 

 Aerobic. 

 Non-pathogenic. 



