BACILLI 209 



The gelatine is very quickly liquefied. On agar-agar a massive dark 

 red substance is formed, while the nutrient medium itself is not coloured. 

 When cultivated in the incubator for several generations, the prodigiosus 

 loses the red pigment. In the cultures on potatoes it also forms, besides 

 the red pigment, trimethylamin. 



Milk is coagulated. Media containing sugar are fermented. The 

 prodigiosus grows also in the absence of oxygen, but no red pigment 

 is produced. It is somewhat pathogenic ; after the introduction of 

 large doses the inoculated animals die with symptoms of poisoning. 



Other chromogenic bacteria occur, distinguished only by the colour 

 of the cultures. Bacillus ruber balticus, ruber aquatilis, caeruleus, pavo- 

 ninus, amethystinus. 



(b.) NON-CHROMOGENIC. 



Bacillus Liquefaciens. One of the most common and widely 

 distributed water bacilli. Strongly motile rods, often arranged in chains 

 of four or more joints. Gelatine media are liquefied very quickly. 



On Plate Cultures, in the form of scales. 



In Stab Cultures, in the form of a stocking, with the upper portion 

 distended. The cultures give off an unpleasant stench. It is a faculta- 

 tive anaerobe, and in nutrient media containing nitrates it produces 

 nitric acid. 



Bacillus Liquidus. (This is also a water bacillus.) Short, plump, 

 slightly motile bacilli, liquefying gelatine very quickly ; in tubes the 

 grey liquefied gelatine is covered with a thin membrane, which, when 

 the tube is shaken, sinks to the bottom of the medium. 



Bacillus Aquatilis. (Another water bacillus.) Thin motile rods, 

 which liquefy the gelatine slowly (according to some authorities, not at 

 all). In gelatine tube cultures they grow on the surface of the medium 

 as small yellow colonies, and on potatoes with a scanty yellowish coating. 



Bacillus Mycoides Wurzel, or Root Bacillus. Found in the 

 earth and in certain kinds of forage ; thick, slightly motile bacilli with 

 rounded poles. Spores are formed in the middle of the rods. Grows 

 only in the presence of oxygen. The greyish-white colonies consist of a 

 net of fine twisted threads. The gelatine is liquefied. 



In Stab Cultures the growth resembles a pine tree placed upside down. 



On Agar-Agar the growth exhibits a texture like the branching of 

 the roots of a tree. There is another species called the Bacillus mycoides 

 roseus, which morphologically resembles the Bacillus anthracis ; it grows 

 best at room temperature. On gelatine plates it forms round, scanty, 

 quickly liquefying, red-coloured colonies. On agar-agar a red-coloured 

 growth ; the pigment is only formed in the dark ; exposed to the light, 

 the growth is white. The pigment is soluble in water. 



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