QUALITATIVE BACTERIOLOGICAL ANALYSIS. 6l 



B. Rubidus. 



Found in water by Eisenberg. It is a medium-sized, motile 

 bacillus. It does not form spores and will only grow at room 

 temperature. The colonies in gelatine plates are round, finely 

 granular, and have a brownish-red colour in the centre. The 

 gelatine is gradually liquefied. On agar and potato it forms a 

 brownish-red growth. 



GROUP VI. 



In this group are contained the bacilli which produce a 

 yellowish or orange coloured pigment; some of them liquefy 

 gelatine, others do not. 



B. Arborescens. 



This organism is common both in surface and deep well-waters. 

 It has the following cultural characteristics. 



Colonies on Gelatine Plates. The colonies have a golden yellow 

 col our, under a low power they resemble a wheat-sheaf; some small 

 growths are also seen consisting of a rod branching at the ends. 

 Sometimes the wheat-sheaf is surrounded by a thin film with 

 fine processes projecting from the margin. Very often the 

 colonies consist simply of a mass of threads spreading out in 

 every direction through the gelatine. 



Gelatine-stab. The gelatine is liquefied in the form of a cup 

 with an accumulation of orange pigment at the bottom. 



Agar-slope. A thick golden-yellow growth. 



Glucose-gelatine* No gas formation. 



Peptone. No indol produced. 



Potato. A thick coarsely granular deep orange-coloured 

 growth. 



Nitrate-broth. Nitrates are reduced to ammonia. 



Milk. After seven days incubation at 22 C. the medium is 

 unchanged. 



Litmus-wliey. After seven days incubation at 22 C. the 

 medium is distinctly alkaline. 



Microscopical Appearance. A thin slender bacillus which does 

 not form spores and possesses only rotatory movement. It grows 

 feebly at 37 C. It is decolorised by Gram. The bacillus 



