164 



86 



The bacteria of mash are noted in the literature under the little characteristic names 

 of Bacillus Delbriicki' and Bacillus acidificans longissimus. As they are derived from the 

 mashed grain, I propose to call them Thermobacterium cereale. There may possibly be 

 several species (as for instance lactose-fermenting and non-lactose-fermenting), and I 

 Would in this connection refer to Henneberg i), "who has made a very thorough study 

 of the lactic acid bacteria of mash. The common thermobacteria of milk (Nos. 6 — 11) 

 should of course be termed Thermobacterium lactis. Here also it is possible that there 

 may be several species (the three first, for instance, which are isolated from milk, grow 

 more strongly in agar than the three last, which Were isolated from Emmental cheese). 

 They have all, however, one point in common: like the mash bacteria, they form lævo- 

 lactic acid. This is also the case with No. 14, which is an even more pronounced milk-rod 

 than the foregoing, and therefore does not ferment maltose. As we have always found 

 this rod in genuine Bulgarian yoghurt, whether obtained through Professor Metschni- 

 KOFF or directly from Professor Prantschoff of Sofia, I consider myself justified in cal- 

 ling it Thermobacterium bulgaricum. The bacterium of Swiss cheese, No. 12, which we have 

 formerly called Bacterium casei e, I now propose to call Thermobacterium helveticum. Related 

 to this bacterium is No. 13, from, the fact of its forming inactive lactic acid, from the strong 

 acid formation in milk, and from its morphological features. It differs,, however, in the 

 fact that like No. 14, it does not ferment maltose, and in the far greater difficulty it 

 finds in growing in artificial substrates, as also by its markedly radiating colonies. We 

 consider therefore, that it should be established as a separate species, and as it is said 

 to occur in yoghurt, we can call it Thermobacterium Jugurt^). 



Appendix to Thermobacteria. 



We may here mention an interesting lactic acid bacterium which we have come across 

 during our controlling Work with commercial starters for creamsouring. Even where these 

 have proved pure by direct investigation they may nevertheless contain a trace of mould, 

 yeast, or rod-shaped lactic acid bacteria, which can gradually develop in the dairy. 

 We therefore always make the additional test of leaving an unopened jar of the culture 

 to stand for a week at 25°, Which is the highest 'temperature used in the souring of the 

 dairy starter or the cream. The detrimental contamination will thus accumulate, while 

 the good acid bacteria (5c. cremoris) perish in their oWn acid. It may then chance, that 

 the starter, instead of becoming sterile by this treatment, as it properly should, becomes 

 transformed to a pure culture of a long-rod form, which in milk forms over 2 % inactive 

 lactic acid, and which also attacks casein (12,3 % SN and 13,5 % DN). Even at the 

 optimal temperature, 30^^, it does not curdle milk until after 2 — 3 days, and is inclined 

 to render it slimy. It is such a pronounced milk bacteria that in artificial substrates, it 

 ferments practically no sugars at all. In older cultures, it is no longer so markedly a long- 

 rod form, but breaks up into chains of short segments, which can be over 1 /a thick. It 



') W. Henneberg: Gärungsbakteriologisches Praktikum. lierliii 1900. 



') In Bulgarian, Yoghurt is called simply „sour milk" (kisselo mleko) but in Turkish, .higurt, anti 

 it is this word which has passed over, under various forms, into the other languages 



