350 MANUAL OF DETERMINATIVE BACTERIOLOGY 



Key to the species of genus Lactobacillus. 



I. Produce only traces of by-products other than lactic acid. Homofermentative. 

 A. Optimum temperature 37° to 60°C or higher. Sub-genus Thermobacterium 

 Orla-Jensen (The Lactic Acid Bacteria, 1919, 160). 



1. Acid from lactose. 



a. Optimum temperature 37° to 45°C. 

 b. Produce levo lactic acid. 



1. Lactobacillus caucasicus. 



2. Lactobacillus lactis. 

 bb. Produce inactive or dextro lactic acid. 



c. Microaerophilic. 



3. Lactobacillus helveticus. 



4. Lactobacillus acidophilus. 

 cc. Anaerobic in freshly isolated cultures. 



5. Lactobacillus bifidus, 



aa. Optimum temperature 45° to 62°C; usually no acid from maltose. 



6. Lactobacillus bulgaricus. 



7. Lactobacillus thermophilus . 

 2. No acid from lactose. 



8. Lactobacillus delbrueckii. 



]i. Optimum temperature 28° to 32°C. Sub-genus Streptobacteriuvi Orla-Jensen 

 {loc. cit., 166). 



1. Acid from lactose. 



a. Produces de.xtro lactic acid. Often prefers lactose to sucrose and 

 maltose. 



9. Lactobacillus casei. 

 aa. Produces inactive lactic acid. 



10. Lactobacillus plantarum. 



2. No acid from lactose. 



11. Lactobacillus Icichnianyiii . 



II. Produce considerable amounts of by-products other than lactic acid (carbon 

 dioxide, alcohol and acetic acid ; mannitol from fructose) . Heterofermentative. 

 Sub-genus Betabacterium Orla-Jensen {loc. cit., 175).* 



A. Optimum temperature 28° to 32°C. Usually ferment arabinose. 



1 . Does not ferment rafhnose, and usually does not ferment sucrose or lactose. 



12. Lactobacillus brevis. 



2. Ferment raffinose, sucrose and lactose. 



13. Lactobacillus buchneri. 



14. Lactobacillus pastorianus. 



B. Optimum temperature 35° to 40°C or higher. Usually does not ferment 



arabinose. 



15. Lactobacillus Jermenti. 



* Also see discussion of Betabacterium caucasicum, p. 358. 



