MICHIGAN ACADEMY OF SCIENCE. 
05 
THE ENVIRONMENT OF SOIL BACTERIA. 
BY DR. F. H. HESSELINK VAN SUCH TELEX. 
In physiology we recognize the influence of environment on the single 
cell. Not only if we take the high water content of the living sub- 
stance into consideration, hut also if we consider metabolism as Ihe 
phenomena of life, the importance of water in the life process is made 
clear. Without water there is no life. By adding to or diminishing Ihe 
water of the living substance within certain limits, we increase, di- 
minish, and limit the intensity of life processes. The environment of 
bacteria is water, and soil bacteria form no exception. There, where 
there is little or no water at their disposal, the metabolic processes are 
reduced to a minimum. Spores, cysts, and other defensive organs are the 
results of the dryness of the medium. In a former publication,* the 
author has tried to make a numerical comparison between the water 
content of the soil and the activity of the soil bacteria. As an indicator 
the carbon dioxide production in soils was chosen, a metabolic product 
that is formed in nearly all life processes in comparatively large quan- 
tities, and in easily detected form. Without going into detail with 
these experiments, I will say that if the soil contained only 4.4% of 
water, the soil bacteria would be unable to attack the easily broken 
down dextrose which was added to the soil. I take this as an example 
illustrating the overwhelming importance of the water content fer- 
tile biochemical action in soils. 
From the foregoing it is clear that water is the medium of soil bac- 
teria. Although one cannot make in proxi a sharp distinction between 
the quantity and the nature of the water, I should like to cite the ex- 
periments of Beyerinckf as evidence of the influence of the nature of 
the water, on the microorganisms. His experiments deal chiefly with 
unicellular organisms, and let us say here that the Oecologieal Method 
proved to be of especial value, in tire case of the lower organisms, be- 
cause they are unicellular and expose in comparison with their con- 
tent such an enormous surface, on which the medium can act. 
In his classical investigations Beyerinck showed Ihe dominating in- 
fluence of the nature of the water environment on the behavior of the 
microorganisms. How uniform was the material with which he started 
must be noted, for it was in many cases the mud of the canal in Delft. 
By influencing intelligently the life conditions of bacteria, such as oxygen 
and food supply, temperature and many other factors, lie was able to 
predict and to obtain with mathematical surety the predominating 
flora. 
In such experiments as this on (lie nature of the water. Soil Bac- 
teriological Science finds its greatest promise. 
If we ask ourselves, “what is the ultimate aim of the applied science 
*F. Hesselink van Suchtelen: Centr. Bl. f. Bakl. II Abt. Bd. 28 S. 45. 
tF. Stockhausen: Oekologie AuhaOfungen nach Beyerinck. 
9 
