184 



106 



Key to Identification 



The lactic acid bacteria ferment carbohydrates and higher alcohols to lactic acid. They do not grow 

 acids therein contained. They are Gram-positive, immotile, sporeless rod- or sphere-forms. We cannot here repea 

 nearest related forms. 



Rod Forms. 



A. Without eatalase. rediu 

 a. Produce only a trace ol 



Genls: Thermobacterium. Form laevo- or inactive lactic acid. Except Tbm. cereale they strongly break down 

 casein and thrive well in j'east extract. They never ferment pentoses and frequently not 

 salicin. Long-rods, which grow at 50° or more, but do not on the other hand grow at 

 lower than 22°. 



Tbm. helveticum. Inactive lactic acid. Ferments maltose, but not saccharose. Able to form more than 2,7 lactic 

 acid in milk. 



Jngurt. Inactive lactic acid. Does not ferment either saccharose or maltose. Able to form more than 

 2.7 " .. lactic acid in milk 



bulgariciim. Laevo lactic acid. Does not ferment either saccharose or maltose. Forms at most 1,7 lactic , 

 acid in milk. 



lactis. Laevo-lactic acid_ Ferments both saccharose and maltose. Forms at most 1,7 lactic acid in 

 milk. 



cereale. Laevo-lactic acid. Ferments as a rule both saccharose and maltose. Does not curdle milk. 



Genls: Streptobacterium. Form inactive or dextro-lactic acid. Thrive well in yeast extract and as a rule 

 also in milk. Alwajs ferment maltose and salicin and only exceptionally not lactose 

 Shorter or longer chains of shorter or longer links. Maximum temperature as a rule 



35=-40°. 



Sbm. plantarum. Mostly inactive lactic acid and no breaking down of casein. As a rule prefers maltose and 

 saccharose to lactose and frequently ferments rafifinose, inulin and pentoses. 



Sbm. casei. 



Mostly dextro-lactic acid and breaking down of casein. Prefers as a rule lactose especially in 

 milk) to saccharose and maltose and only exceptionally ferments raffinose, inulin and pentoses. 



Genls: Betabaoterium. 



Bbm. cancasicum. 

 » breve. 

 > longum. 



b. As a rule produce perceivable amoiu 

 .Almost always form inactive lactic acid. Thrive well in yeast extract, but as a rule 

 badly in milk. Never ferment considerable amounts of mannite. inulin, dextrin, starch 

 or salicin. Have a comparatively small mannose fermentation. 

 Prefers arabinose. Ferments no disaccharides out of the Kefir grain 

 Ferments arabinose with predilection, frequently xylose too. Maximum temperature 38^. 

 Never ferments arabinose, but frequently .xylose, and as a rule raffinose. Maximum 

 temperature ih-. 



B. As a rule catalasc. n>du 

 E5LS: Microbacteriuiu. Tiie undermentioned strains form dextro lactic acid. Thrive badly in yeast extract. Very 



small rods, only exceptionally more than 0,5 ;x thick. 

 Mbm. laclicum. Ferments maltose and frequently some starch Slight, often greenish yellow surface growth. 

 mesentericiim Ferments maltose, raffinose and starcii. Strongly curled, white surface gro\*-th. 

 • ßaviim. Does not ferment any di- or polysaccharides. N'igorous yellow surface growth. 



