78 HIGH TEMPERATURE ORGANISM OP FERMENTING TAN-BARK, 



gas bubbles.* The mixed culture had decomposed the saccharose with evolution 

 of gas. From this culture other slopes were smeared and a number of colonies 

 were obtained. Although these grew well at 60°, tliey failed to produce gas. A 

 more vigorous gas formation was obtained from the mixed culture derived from 

 another flask of bark which had been covered with N/100 sodium hydrate and 

 which itself showed signs of gas formation, although it was doubtful whether the 

 bubbles entrapped in the bark were derived from the fermentation of the bark 

 or from the air absorbed or caught in the spaces of the bark. The examination 

 of the gassy agar-tubes, by tube and by jalate culture at 60°, showed only one 

 kind of colony and the organism was not a saccharose fermenter. 



Although the fermentation) of saccharose was not the object of the research, 

 it seemed probable that a definite saccharose-fermenting bacterium would be more 

 likely to be able to ferment cellulose than one which could not do so. Conse- 

 quently a rather extended search was made for tliis active organism, and gradually 

 it was determined that the gas fermentation of saccharo.se (and of dextrose) was 

 the result of a condition and not due to an admixture with an unknown organism. 

 During the search, notes were made upon the nature and activities of the tlier- 

 mophilic bacterium. 



It is a stout rod of a general length of from 3 to 4.5yn but varying from 

 1.5 up to 15ja or longer. Its breadth is 0.7ju,. Spores are formed terminally; 

 they are oval at fli'st, but become rounded. Their general size is 0.9 X 1-5 /x. 

 The rods when grown in saccharose media at 60° were Gram negative ; at 37° 

 they were Gram positive. Although non-motile in fluid media, the rods were 

 studded with many peritrichous flagella. 



The colonies on saccharose agar were white and rounded and often l)ecame 

 irregular with age. They were either translucent white or semi-opaque and 

 j'ough 01'' terraced (button-like) . Microscopically, they had generally a granular 

 centre which gradually thinned off to a clear margin. Sometimes the structure 

 appeared rippled or wavy and sometimes faintly radial. The edge was sometimes 

 smooth, sometime.'^ lacerate. Much seemed to depend upon the amount of spore 

 formation that had taken jilace, and the consistency of the agar. An almost 

 Iranslucent colony with a wavy structure when transferred to sloped agar gave an 

 opaque rough stroke and, conversely, an opaque colony gave a smooth translucent 

 expansion . 



Some races of the bacteria grew slowly at 37° while others did not. They 

 all grew well at 60° and not (|uite so strongly at 65° or at 70°. At tlu' latter 

 temperature some races failed to grow, and this raised the suspicion that much 

 had yet to be learned about the acclimatisation of llie bacteria and their spores. 

 Throughout the research there was always a doubt as to whether a particular 

 culture would transfer. An actively growing culture would always transfer but 

 the same could not be said of a culture whicli had been at laboratory temperature 

 for days or weeks or at 60° for a few days. 



When grown upon saccharose-agar coloured with litmus, the bacteria seemed 

 fo h;i\(' a double artiou (see )). S3). Witli gradually increasing acidity, the 



* This production of gas was an exceptional case, for later tests showed that a 

 preliminary treatment in an alkaline liquid or the presence of alkali in the agar 

 itself was necessary. But it must he borne in mind that when bacteria have been 

 recently isolated from what may be called their natural habitat, they may be and 

 probably are more vigorous than after a spell of subcultivation in the laboratory. 



