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THE INFLUENCE OF LOW TEMPERATUR4 
ON SOIL BACTERIA 
A. F. Vass 
Temperature is one of the most important factors influencing the 
growth and reproduction of microorganisms. Considerable work has 
been done in studying the effect of low temperature on the vitality and 
growth of bacteria, but the results have varied so greatly that it is difficult 
to draw any very definite conclusions from them. Certain investigators 
have found in frozen soils what they believed to be bacterial growth and 
reproduction to an even greater extent than is found at temperatures 
usually considered most favorable for protoplasmic activity. 
The increased use of ice and the knowledge of water-borne epidemics 
have stimulated investigation in regard to the ability of the pathogenic 
bacteria to withstand freezing and storage in ice. In the work with pure 
cultures of pathogenic and nonpathogenic bacteria a great variation in 
results has been obtained. The natural ice dealer can find plenty of 
evidence to support his theory that the pathogenic bacteria in water 
are killed when the water is frozen and the ice stored for summer use. 
On the other hand, the public health officer can present equally strong 
evidence to show that the bacteria are not killed by freezing. 
HISTORICAL 
The literature herein reviewed deals with the ability of the pathogenic 
and the nonpathogenic bacteria to withstand exposure to low tempera- 
ture, the influence of low temperature on the bacterial flora of the soil, 
and the cause of the death of the cell upon exposure to low temperature 
together with the factors that influence it. 
PURE CULTURES 
In the work with pure cultures both the pathogenic and the non- 
pathogenic forms were used. In some cases, however, there may be 
some doubt as to the purity of the cultures. 
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