4o8 DESCRIPTION OF SOME SPECIES OF MILK BACTERIA 



Agar plates and tubes — White, 

 moist, irregular colonies spreading 

 in streaks over the medium. 



Potato — Dry, thin growth ; 

 lemon-yellow in colour. 



Milk — No effect, except alkaline 

 reaction. 



Aerobic. 



Non-pathogenic. 



BACIIiLUS OITREUS LACTIS, 

 Nos. 1 and 2 (Conn). 



Source and habitat — Milk. 

 Morphology — Rod i m long by -7 /t 



broad ; with round ends. 

 Staining reaction — Ordinary aniline 



stain. 

 Capsule — A slimy capsule connects 

 the rods when grown on potato and 

 agar. 

 Biology : cultural characters {includ- 

 ing biochemical features'). 



Gelatine plates and tubes — 

 Small raised lemon-yellow colonies, 

 smooth and clear. (No. 2 only 

 liquefies gelatine.) In stab-culture 

 a rough surface growth, thick, 

 but transparent. Moderate needle 

 growth. 



Agar plates and tubes — A thin, 

 moist, transparent, lemon - yellow 

 growth. 



Potato — A thick lemon-yellow 

 growth. 



Milk — No effect is produced by 



No. 1 on milk or cream. No. 2 



curdles milk, producing a weak, 



alkaline curd at room temperature. 



Aerobic. 



Non-pathogenic. 



BACILLUS COLI COMMUNIS 



(Escherich). 



Source and habitat — An organism 

 of wide distribution, normally 

 present in the excreta of man 

 and animals. Abundant in crude 

 sewage (ioo,oco per c.c. in London 



sewage, Houston). In polluted 

 water, milk, soil, etc. 



Morphology — A short rod with round 

 ends ; size and shape may vary 

 in same colony ; polymorphism, 

 depending upon age of culture, 

 products of culture, composition 

 of medium, etc. 2 to 3 m long, 

 0'5 to 0-6 M broad ; sometimes oval, 

 hardly longer than broad. Usually 

 single, but occasionally in pairs, 

 bundles, or even chains and 

 threads. 



Staining reaction— Ordinary aniline 

 dyes. Decolorised by Gram. 

 (Schmidt stated that B. coli from 

 fatty stools of infants holds the 

 Gram.) 



Capsule — Present. 



Flagella — 3 or 4 in number, fragile, 

 short, and not wavy. Sometimes 

 only a terminal one ; sometimes 

 several long ones ; but polar stain- 

 ing and vacuolation frequently 

 present in old cultures, or cultures 

 grown under unfavourable con- 

 ditions. 



Motility — Present, especially in young 

 cultures, but not, as a rule, so 

 active as B. typhosus; oscillatory 

 rather than progressive. 



Spore formation — None. 



Biology : cultural characters {includ- 

 ing biochemical features) — Grows 

 best at 37° C., but will also grow 

 at room temperature. Gordon 

 showed that many varieties of 

 B. coli exist, with many minor 

 modifications {Jour, of Path, and 

 Bact.^ 1897). 



In gelatifte plate cultures the 

 colonies appear generally within 

 24 hours at 20° C. The deep 

 colonies appear as small white 

 dots, the surface colonies as 

 delicate, slightly granular films of 

 an irregularly circular shape. 

 They are bluish-white by reflected, 

 and amber colour by transmitted 



