BACTERIA 45 



not spoil butter under normal conditions. In addition to a 

 fluorescence, this organism produces a blue colour (which is soluble 

 in chloroform and is turned red by acids). It is often found as 

 one of the active organisms in inflammations, when it imparts a 

 blue or green colour, to the pus. A similar but Gram-positive, 

 lofotrich and non-liquefying species is the bacterium of blue milk, 

 Bacterium syncyaneum (Fig. 26), which in addition to a fluorescence 

 produces a grey colour which is turned blue by acids ; it can 

 therefore only colour milk blue in the presence of lactic acid 

 bacteria. A peptonising rod form which colours neutral milk blue 

 was isolated by Carl Lind, working in the author's laboratory. 

 In all cases the blue coloration starts on the surface of the milk. 

 The last- mentioned organism is perhaps identical with the water 

 bacterium, B.cyaneofuscus, isolated by Beijerinck 1 , which produces 

 blue spots in cheese. 



The group most nearly allied to the fluorescent bacteria are the 

 marine phosphorescent bacteria, which cause dead 1 fish to become 

 luminous. Being marine organisms, they require a nutrient 

 medium containing sodium chloride. 



2. Peptonising Cocci. The liquefying micrococci and sarcina 

 forms, especially those which do not produce acid, generally take 

 part in putrefactive processes. Several of the colour-producing 

 varieties thrive well in the outer paste which becomes the rind of 

 many cheeses. 



3. Coli Bacteria. As mentioned above, these are intestinal 

 organisms which find their way into milk from the excreta. Being 

 acid-producers, they will generally retard rather than promote 

 putrefaction, as carbohydrates are present in sufficient quantity 

 both in the intestine and in milk. In the absence of carbo- 

 hydrates, however, they act as typical putrefactive bacteria, 

 decomposing amino acids. 



4. The Proteus Bacteria. As their name implies, these rod 

 forms may assume many different shapes and sizes, sometimes 

 growing out into long threads which may form a tangled network. 

 They form no spores, and do not show any uniformity in their 

 behaviour towards Gram's stain ; as a rule they are actively 

 motile, being plentifully supplied with flagellse all over the cell. 

 The proteus bacteria mostly ferment sugars, especially dextrose, 

 with the production of succinic and acetic acids and various gases, 

 and they generally liquefy gelatine. A non-liquefying form, 

 Bacterium Zopfii, whose colonies ramify so freely on gelatine that 

 it might easily be mistaken for a mould, is frequently found in 

 milk. The most typical of the aerobic putrefactive bacteria is 



1 "Botaiiische Zeituiig," 1891, Bd. XLIX., p. 704. 



