170 PHYSIOLOGY OF BACTERIA 



ammonia will make the neutral solution acid, and 

 Wehmer found that a Penicillium species was readily 

 killed by prolonged growth on ammonium sulphate 

 merely by accumulation of acid. Accumulation of 

 alkali by nitrate-consuming organisms has never been 

 reported harmful, perhaps on account of the formation 

 of the organic acids. 



As a curiosity, B. hiltneri which can oxidize HCN to 

 CO2, H2O and N, according to Kaserer (1907), should 

 be mentioned. 



The organisms which depend upon organic matter for 

 their energy supply, seem to prefer organic nitrogen also. 

 The usefulness of amines for cell construction has not 

 been studied extensively, but we know that methylamine 

 can be used by Aspergillus and Penicillium; that the 

 mono-amine is the best, and trimethylamine the poorest 

 source of nitrogen, and that tetramethyl ammonium 

 hydroxide is not suitable for cell construction, den 

 Dooren de Jong (1927) has given the genus name 

 Protaminohacter to a group of bacteria which were able 

 to assimilate amines. 



Urea can be used by quite a large number of bacteria 

 as a source of nitrogen. This faculty is not limited to the 

 urea-fermenting organisms. Some yeasts and many 

 molds can also live on urea as the only nitrogen source 

 (Lindner, 1905). 



Next in simplicity of composition are the amino - 

 derivatives. Alkaloids do not seem to be sufficient for 

 growth, at least not for the common molds, though they 

 are decomposed, perhaps for energy purposes only. 

 Amino-acids such as glycol, leucin, aspartic acid etc. 

 are good nitrogen sources for many organisms but some 

 thrive well only if they have a better source of energy 

 (or of carbon) such as dextrose or mannite. That the 



