DESCRIPTION OF SOME SPECIES OF MILK BACTERIA 



Motility — Feebly motile. 

 Spore formation — Oval spores in pre- 

 sence of oxygen. 

 Biology : cultural characters {includ- 

 ing biochemical features). 



Bouillon — Bouillon becomes 

 cloudy with formation of surface 

 pellicle. 



Gelatine tubes ; agar tubes — Stab- 

 cultures resemble those of the hay 

 bacillus. 



Potato — Growth moist, smooth, 

 without lustre and without wrinkle. 

 Milk — Is coagulated in about 24 

 hours, the coagulum being subse- 

 quently dissolved after about 43 

 hours. There is a strong, genuine 

 odour of Emmenthaler cheese, and 

 this also occurs upon sterilised 

 casein precipitated by rennet. 

 Facultative anaerobe. 

 Non-pathogenic. 



BACILLUS BUTYBIOUS (Botkin). 



Source afid habitat — Widely distri- 

 buted in milk, water, soil, dust. 



Morphology — Rods, i to 3 u long, 0-5 

 M thick. Sometimes in threads, 

 sometimes in chains. 



Staining reaction — Stains by Gram's 

 method. 



Motility — Motile. 



Spore formatio?t — Spores in middle or 

 at end of bacillus ; about i fj. thick 

 (provisional) ; sporulation not 

 proved (Botkin). 



Biology : cultural characters {includ- 

 ing biochemical features) — Favour- 

 able temperature 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 is rapidly liquefied ; gas 

 development ; slight undulating 



colonies as if consisting of mass of 

 felted threads. No odour. 



Agar plates and tubes — A luxuri- 

 ant growth with gas development 

 and ramifications in medium. 

 Odour present. 



Potato — Growth extends into 

 potato substance ; smell of alcohol. 



Milk— Ax 37° C., after 15 hours 

 casein precipitated and butyric 

 acid is formed without intermediate 

 formation of lactic acid. Coagulum 

 eventually dissolves ; before that 

 stage the appearance is very 

 characteristic ; there is a spongy 

 fatty layer on surface, then clear 

 fluid, and then a white deposit. 

 The presence of this organism is 

 readily proved in almost all milk. 

 Fill a half litre flask with milk, and 

 steam at 100° C. for half an hour. 

 Incubate at 37° C. In less than 24 

 hours the characteristic changes 

 will occur, with strong odour of 

 butyric acid. Care must be taken 

 that the gas pressure does not 

 burst the flask. There is a marked 

 odour of butyric acid. Other acids 

 present are acetic, formic, and 

 lactic. 



Anaerobic or aerobic — Facultative 

 anaerobe. 



Non-pathogenic — It has been 

 suggested that the B. enteritidis 

 sporogenes of Klein is a pathogenic 

 form of this bacillus. 



BACILLUS BUTYRICUS (Hiippe). 



Source atid habitat — Milk. 

 Morphology — Slender rods ; i-2 to 4 



/tt long, 0-5 At thick ; round ends. 



May grow into filaments ; rods 



slightly bent; 2-1 /* long, 0-3 /u 



broad. 



Staining reaction — Stains by Gram's 

 method. 



Flagellaj motility — Many flagella ; 

 actively motile. 



