60 



€loudy and the odor of pyridine disappeared. The 

 solution was plated out and three isolations were made, 

 one of which proved to be an organism which destroyed 

 pyridine. With this bacterium present the odor of 

 pyridine disappeared in five days and was replaced 

 by a characteristic sour smell. As the pyridine was 

 the only source of nitrogen in this solution it is evident 

 that pyridine is a very favorable source of nitrogen for 

 this organism. No attempt was made to determine 

 whether the pyridine might not also serve as an energy 

 source for this organism. 



Qiiinoline. Attempts were also made by the same 

 methods to secure an organism acting on quinoline, 

 but thus far none such has been found. 



These three organisms, one acting on cumarin, one 

 on vanillin and one on pyridine are different species. 

 They also seem to be specific inasmuch as, with the 

 solutions and concentrations used, the organism acting 

 on vanillin will not act on cumarin or pyridine and 

 vice versa. 



It has also been demonstrated by water culture and 

 soil experiments that the bacterium feeding on vanillin 

 will in pure culture entirely destroy the toxicity of 

 vanillin for wheat plants. It has also been found that 

 the bacterium feeding on cumarin will in pure culture 

 destroy the toxicity of that compound for wheat plants. 

 Further work on the physiology of these organisms is 

 being undertaken. 



Discussion. The enormous increase of bacteria in 

 the vanillin, cumarin or pyridine treated soils, the dis- 

 appearance of the toxic effects of the compounds in 

 inoculated soil, but not in sterile soil, and the isolation 

 of specific microorganisms using thein as food would 

 seem to indicate that their disappearance in the soils 

 used in this investigation is due to the fact that they 

 serve as very favorable food sources to definite species 

 of bacteria. While no specific organism using quino- 

 line was isolated, the effect of quinoline on the micro- 

 organisms in the pots and the results secured with the 

 sterile and inoculated soils would seem to indicate that 

 quinoline, in the soils used, suffers the same fate. 



The relation of this data to the phenomena found in 

 "partial sterilization" may be pointed out. The initial 

 decrease in numbers noted in the vanillin and quino- 

 line treated soils is probably due to the toxic action of 

 the compound on some species of the bacteria present. 



