430 DESCRIPTION OF SOME SPECIES OF MILK BACTERIA 



Blood serum — A wrinkled growth 

 develops. 



Facultative anaerobe. 

 Non-pathogenic. 



BACILLUS SYNCYANEUS 



(Ehrenberg). 



B. cyanogenes of Fliigge — Bacillus of 

 blue milk. The typical organism 

 of chromogenic milk. 



Source and habitat — M i Ik, an d probably 

 soil, dust, water, etc. 



Morphology ; form and difnensions — 

 Rod varying in length from 2 ya to 

 4 fi, and 0-5 ix in breadth, with 

 rounded ends ; no threads. 



Manner of groupi7ig — Form zooglea 

 with a hyaline aureola ; a sort of 

 gelatinous capsule. 



Spore formation — Ovoid spores a little 

 larger than the rods, which swell 

 at the point of production have 

 been described (Hiippe). Probably 

 they do not occur (Heim). 



Polymorphism— \n cultures on liquid 

 media involution forms are pro- 

 duced. 



Staining reaction — Easily stained by 

 aniline dyes and Gram's method. 



Flagella J motility — Special methods 

 disclose from two to five flagella 

 at ends of the rod ; bacillus actively 

 motile. 



Biology — Cultures are easily obtained 

 in the usual media ; the microbe 

 is exclusively aerobic. It grows 

 well at the ordinary temperature, 

 and less well towards 30° ; at 40° 

 the cultures often die. The media 

 soon give an alkaline reaction, even 

 those which are acid. The pro- 

 duction of pigment appears to de- 

 pend, at least within certain limits, 

 on the nutriment which the species 

 has at its disposition, none being 

 formed under special conditions. 

 The shade of the coloration may 

 vary ; sometimes it is of a very 

 decided blue, sometimes slightly 



violet. This microbe can also, 

 under conditions still undeter- 

 mined, lose the power of producing 

 pigment and give a series of colour- 

 less cultures. This is a fact which 

 has been observed with regard to 

 many of the chromogenic bacteria. 

 It is possible, by making this 

 bacterium live under eminently 

 favourable conditions, to make it 

 recover its chromogenic power. 



Gelatine plates — At the end of 2 

 days, small, whitish, moist colonies 

 are seen, rounded and granular. 

 The gelatine takes a blue-grey tint 

 and is not liquefied. Grows better 

 on acid gelatine than on that with 

 a slight alkaline reaction (0-2 to 

 0-3 per cent, of lactic acid). 



Gelatine tubes — In j/«(5-cultures 

 in gelatine tubes a thin whitish 

 growth is seen in the needle track, 

 and on the surface a small white 

 disc ; the gelatine takes a greenish- 

 blue colour which turns brown with 

 age. Culture grows least in depth 

 of medium. In ^/r^/(v - cultures, 

 small white colonies develop along 

 the line of inoculation, round which 

 the gelatine takes a greenish tint 

 which may turn into grey-blue. In 

 these gelatine cultures the organisms 

 taken from the centre are much 

 smaller than those on the edges ; 

 the first may measure only from 

 I yu to 1-4 M, whilst the others can 

 be from 2-3 /x to 3-5 /x in length ; 

 the breadth is about the same, from 

 0-4 [L to 0-5 i*.. On lactose gelatine 

 a bluish-white growth is produced, 

 with brown coloration of medium. 



Agar — Shiny growth occurs ; 

 brown pigment may be markedly 

 developed. 



Potato — A band or series of 

 yellowish-brown patches is pro- 

 duced ; the substance of the potato 

 is deeply coloured grey - blue. 

 Sometimes the colour of the growth 



