280 



Accumulation and occurrence. 



Long ago the following experiment for the accumulation of this 

 S|)ecies was described '). 



Coarsely gioiind rje with some chalk and inoculated with fertile 

 garden soil is mixed with water in a deep beaker to a thick solid 

 paste, boiled during some seconds to kill the non-spore-formers and 

 cultivated at 25° to 30° C. As the spores of B. polymyxa soon die 

 at boiling, the heating must last but a short time. After a few days 

 the surface is covered with a coherent film of B. mesentericiis *) and 

 other closely related species, while in the depth a butyric-acid fer- 

 mentation takes place, usually simultaneously with butylic-alcohol- 

 and poly my xa fermentation. 



It is clear that this accumulation reposes essentially on a tempo- 

 rary anaërobiosis of B. polymyxa, wliich can also grow aerobic and 

 so behaves like the sAq.o\\q\ }Qn.^i M\iM\\e Aërobacter-Coligroup mwow^ 

 the bacteria. The rye produces the sugar causing the fermentation, 

 i.e. the soui-ce of energy, which makes the anaërobiosis possible so 

 long as the "excitation oxygen" is still sufficiently present, albeit 

 chemically non-demonstrable, whereas the want of "oxidation 

 oxygen", which is required for aërobiosis in much larger quantity 

 as source of energy, is temporarily excluded. Pasteur's statement: 

 "la fermentation est la vie sans air" is evidently applicable to B. 

 'polymyxa. 



By sowing out the fermenting matter from the depth on wort- 

 agar, ordinarily already after few days the polymyxa colonies become 

 visible as lumps of slime, together with the unavoidable flat spread- 

 ing colonies of B. mesentericus. 



This method can only produce those varieties of B. polymyxa 

 which are able to resist a relatively high concenti-alion of the food. 

 Another accumulation method by which also forms adapted to a 

 lower concentration of food are obtained is based on the aërobiosis 

 of our bacterium. 



After the observation had been made tiiat flasks of boiled wort, not 

 sufficiently sterilised, were not seldom spoiled at the low temperature 

 of 15° C by the development of B. megatherium and never by B. 

 mesentericus, whose germs were certainly also present, the question 



1) M. W, Beijerinck. De butylalcoholgisting en het butylferment. Academy of Sciences. 

 Amsterdam 1893. 



^) This film may be colourless, brown, red, and even jet black according to the 

 accidentally present varieties of B. mesentericus . The black form is rare and 

 sometimes obtained by the "mesentericus experiment" with unwashed currants 

 (boiling with chalk, cultivating at aeration at 30° to 40° C). 



