424 DESCRIPTION OF SOME SPECIES OF MILK BACTERIA 



Milk, slow peptonisation, finally 

 flocculent coagulation of milk ; 

 develops an aromatic smell. If 

 the milk is warmed a coagulation 

 of tough consistency results through 

 free rennet fermentation. 



BACIIiliUS LAOTIS iEROGBNES 



(Escherich and Kruse). 



Source and habitat — Milk ; milk stools 

 of infants (Escherich). 



Morphology — Short, thick rods with 

 round ends. -5 to -8 ii broad, i to 2 

 /i long ; usually in pairs or irregular 

 heaps. 



Staining reaction — Does not stain by 

 Gram's method. 



Flagella; motility — No flagella ; non- 

 motile. 



Spore formation — N one. 



Biology : cultural characters {includ- 

 ing biochemical features) — Grows 

 best at 37° C. 



Gelatine plates and tubes — Lux- 

 uriant shiny growth upon surface 

 in gelatine stab-culture ; growth 

 like B. colij raised, white, shining 

 moist colonies ; porcelain-like ; an 

 abundant nail-shaped growth in 

 stab-cultures. No liquefaction. 



Potato — White raised colonies 

 appear which coalesce and form a 

 creamy layer. Gas bubbles. 



Blood serum — A raised, moist, 

 shining white growth. 



Other media — In milk sugar and 

 grape solution it produces gas. 



Pathogenic — For rabbits and 

 guinea-pigs. 



BACILLUS LACTIS ALBUS (LOffler). 



Source and habitat — Milk. 



Morphology — This is amongst the 

 largest of known bacilli, resem- 

 bling the B. subtilis. Rods, 4 m 

 long, 0-9 to I M broad ; forms long 

 translucent threads, especially in 

 milk. 



Gelatine — Rapid liquefaction without 



formation of surface membrane. 

 Agar — A thick growth. 



Potato — Flat, dry, white colonies with 

 ill-defined edges. 



Milk — Coagulated by lab fermentation 

 with subsequent peptonisation and 

 the setting free of lactic acid salts 

 with production of butyric acid. 

 Produces bitter milk. 

 Non-pathogenic. 



BACILLUS LACTIS BRYTHRO- 

 GENBS (Grotenfeld). 



Source and habitat — Milk. 



Morphology — Rods and sometimes 

 filaments. o-8 yu to 3 m long, -5 to 

 I ji. broad. 



Staining reaction — Stains by Gram's 

 method. 



Motility — Non-motile. 



Spore formation — Absent. 



Biology: cultural characters {includ- 

 ing biochemical features). 



Bouillon - — Produces abundant 

 indol, and turbidity of medium. 



Gelatitie plates and tubes — Small 

 circular greyish-yellow colonies, 

 sinking on liquefaction. At first 

 resemble B. coli, after liquefaction 

 border appears hairy and irregular. 

 Degree and rapidity of liquefaction 

 varies. A sulphur yellow growth 

 becoming red in stab-culture 

 liquefaction cylindrical, turbid and 

 pink. 



Agar plates and tubes — Moist 

 yellow growth, medium becomes 

 rose -red in diffuse daylight. 

 Grotenfelt states that the pigment 

 presents two lines between D. and 

 E. and one in blue part of spec- 

 trum. 



Potato — Sulphur yellow ; elevated 

 growth. 



Milk — The cream is separated 

 and casein forms a flocculent pre- 



