86 BACTERIAL METABOLISM PRODUCTS 



products. The mechanism of the fermentation as outlined by 

 Harden is illustrated by the reaction. 



CH..OH CHsCHsOH + SC'Oz + 3H- 



CHOHCHaOH COOH 



CH OH CH OH CH 3 CH 

 CHOHCHOH CHOH + CH? 

 CH OH CH OH COOH COOH 



CHO CH OH 



CHO 



Glucose. Lactic acid. Succinic acid. 



Unless some base be added to neutralize the acid as formed, the 

 lactose of milk is never completely converted into lactic acid because 

 the accumulation of the acid is sufficient to stop most bacterial 

 growth, as is seen by the fact that meat placed in buttermilk will 

 keep for some time. 



Butyric Acid. Under certain conditions a further decomposition 

 of the lactic acid may occur with the formation of butyric acid 

 according to the following equation: 



2C 3 H 6 3 C 4 H 8 2 + 2C0 2 + 2H 2 



Lactic acid. Butyric acid. 



However, the butyric acid bacteria possess the power of ferment- 

 ing sugar with the formation of butyric acid. 



+ O 2 = CH 3 CH 2 CH 2 COOH + 2CO 2 + 2H 2 O 

 Glucose. Butyric acid. 



Although the number of organisms which possess the power of 

 producing butyric acid are large, they are not as numerous as those 

 which possess the power of forming lactic acid. They are usually 

 anaerobic spore-bearers with a tendency to form spindle-shaped 

 cells, for which reason they have been given the name Clostridium. 

 Many members of this group possess the power of fixing nitrogen; 

 they probably play an important part in maintaining the nitrogen 

 supply of the soil. B. bofodinus, the causative agent in meat poison- 

 ing, forms butyric acid as does also B. tetani. 



In the great majority of cases bacteria produce a number of differ- 

 ent products; for instance, Azotobacter chroococcum produces from 

 the carbohydrates, ethyl alcohol, glycocoll, acetic acid, butyric acid, 

 lactic acid, carbon dioxid, and hydrogen. The quantity and quality 

 of the different products vary with the species and with the carbo- 

 hydrate used. 



Bacterium pasteuriamim grows in wine and cider vinegars. It 

 produces a variety of products, depending upon the specific sub- 

 stance acted upon. It produces gluconic acid CH 2 OH (CHOH) 4 - 

 COOH from dextrose, propionic acid (C 2 H 5 COOH) from propyl 



