492 



PRINCIPLES OF SOIL MICROBIOLOGY 



acids. In the presence of a mixture of the two organisms, the pro- 

 tein is rapidly changed to ammonia. Thus there is a possibility that 

 various organisms take an active part in the various stages of the 

 process; organisms like Bac. cereus may be active in the first stages of 

 hydrolysis and organisms like Bad. fluorescens, in the latter stages 

 leading to the formation of ammonia (fig. 27). This confirmed the 

 earlier investigations of Tissier and Martelly, 60 who found that the 

 action of Bad. colt, various micrococci and Bad. filiformis aerobius 

 upon natural proteins was nil, or almost nil; but they acted very readily 



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'-Sfisa-^ 



Fig. 27. Course of accumulation of amino- and ammonia-nitrogen from casein 

 by Bac. cereus and Bad. fluorescens (from Waksman and Lomanitz). 



upon the hydrolytic products of proteins. The same was true of 

 certain anaerobic bacteria and even the action of Bad. vulgare upon 

 pure proteins has been doubted. However, various spore-forming 

 bacteria, especially anaerobes, like Bac. gracilis putidus, Bac. putrificus 

 and also Bac. perfn'ngens, Bac. bifermentans and Bac. sporogenes rapidly 

 attacked native proteins. They suggested, therefore, to divide the 

 bacteria into two groups, on this basis. 



The number of soil bacteria capable of forming ammonia from pro- 



60 Tissier, H., and Martelly. Recherches sur la putrefaction de la viande 

 de boucherie. Ann. Inst. Past., 16: 865-903. 1902. 



