108 BACTERIA AND FERMENTATION 



which is followed by the fermentation of the lactic acid: 



2C 3 H 6 O 3 = C 4 H 8 O 2 + 2CO 2 + 2 H 2 . 



Lactic acid. Butyric acid. Carbonic Free hydrogen. 



acid gas. 



Previously to 1880, the only work which had been done in the 

 elucidation of the bacterial origin of butyric fermentation had been 

 accomplished by Prazmowski and Pasteur; the former designating 

 the organism he found Clostridium lutyricum, and the latter naming 

 his "infusoires" Vibrion lutyrique. Prazmowski emphasised the 

 motility and resistance of the bacillus, and found that the latter was 

 due to the spores produced by the organism. These spores were 

 able to withstand boiling for several minutes. Fitz went so far as 

 to say that butyric spores could resist boiling for twenty minutes. 

 Prazmowski was unable to obtain pure cultures. Clostridium buty- 

 ricum grows most readily at a temperature of about 40 C., and is 

 very widely distributed in nature. It is capable of dissolving cellu- 

 lose, and therefore plays a part in the cellulose fermentation, which 

 is employed in various maceration industries. It is generally held 

 that in such fermentations there is symbiotic action between the 

 butyric bacillus and an organism incapable of causing " retting " by 

 itself. The organisms discovered by Prazmowski and Pasteur were 

 anaerobic. But Fitz and Hueppe isolated an aerobic butyric bacillus. 

 This fact was confirmed by Gruber, working with a pure culture in 

 1887, and it was at the same time demonstrated that the Clostridium 

 lutyricum of Prazmowski consists of a number of closely allied, but 

 distinct, species. Lafar states that nearly related to this is a ferment 

 isolated by Liborius from old cheese, and introduced into literature 

 under the name of Clostridium fcetidum. This organism liberates 

 foul-smelling gases, in addition to producing butyric acid, and forms 

 one of the many connecting links between the butyric acid bacteria 

 and the so-called " potato " bacilli. No sharply defined limit can be 

 drawn between these two groups. 



The following are the three chief organisms of butyric acid : 



1. Bacillus Butyricus (Botkin) 



Source and habitat Widely distributed in milk, water, soil, dust. 



Morphology Hods, 1 to 3 ^ long, 0'5 ^ thick. Sometimes in threads, sometimes 

 in chains. 



Staining reaction Stains by Gram's method. 



Motility Motile. 



Spore formation Spores in middle or at end of bacillus ; about 1 /x thick 

 (provisional) ; sporulation not proved (Botkin). 



Biology : cultural characters (including biochemical features') Favourable tempera- 

 ture 37 C. ; organism contains starch granules. 



Bouillon Slight growth ; at 18 C. involution forms may occur. Vigorous 

 growth if glucose present, with opaque turbidity. 



Gelatine plates and tubes Round or oval colonies with sinuous edges ; medium 



