THE NON-PERSISTENCE OF BACTERIO-TOXINS 

 IN THE SOIL. 



By HENRY BROUGHAM HUTCHINSON 

 AND AAGE CHRISTIAN THAYSEN. 



(Rothamsted Experimental Station.) 



(With Four Curves in text.) 



Since the soil is the abode of a considerable bacterial population and 

 the seat of innumerable bacterial changes it might be supposed that 

 bacterial toxins would occur there. It is of fundamental importance to 

 soil bacteriology to settle this point and to discover whether there is 

 any evidence that such toxins exist, for any depression of cell growth 

 owing to their presence must obviously be reflected in a limitation of 

 plant food production. 



If a strict analogy coidd be drawn between pure culture and soil 

 conditions the question would present little difficulty, but there are 

 several reasons why this is not permissible. Because a pure culture of 

 an organism growing in an artificial medium sooner or later begins to 

 suffer from an accumulation of its own products, it must not be hastily 

 inferred that a similar check occurs in the soil. In the first instance the 

 bacterial flora of the soil is exceedingly complex and many of the ob- 

 served organisms are largely dependent on the products of the activity 

 of other species or physiological groups. In the second place the soil 

 flora is remarkable for its potency and its power of transforming a 

 considerable range of compounds. Thus there obtains a chain of con- 

 structive and destructive processes operating from nitrogen to proteins 

 and back again on the one hand, and from carbon dioxide to cellulose 

 and back on the other, while even such unlikely compounds as phenol, 

 pyridene and carbon bisulphide are not immune from attack. The 

 end products of this collective action are water, carbon dioxide and 

 nitrates which do not accumulate in normal soils but are removed by 

 natural processes. There are of course intermediate products — protein 



