Section IV, 1917 [15] Trans. R.S.C. 



Bacteria of Frozen Soils in Quebec. 

 By J. Vanderleck, Ch.E. 



Presented by F. C. Harrison, D.Sc., F. R.S.C. 

 (Read May Meeting, 1917). 



Introduction. 



During the years 1909-1913 the numbers of bacteria present 

 in frozen soils were investigated by H. J. Conn ^ W. M. Esten-, 

 P. G. Brown and R. G. Smith^ E. C. Harden^ and others. 



Their observations, contrary to prevailing ideas, indicate the 

 presence of large numbers of bacteria in such soils. Conn explains 

 his results and gives the following summary of his analyses: — • 



1. "Quantitative determinations carried on in the same field as that 



sampled in 1909-10 have shown during the following year an 

 increase in numbers of bacteria in frozen soil almost as great 

 as that noticed during the first winter. 



2. During the second winter the numbers have increased while the 



soil has been well frozen, but have decreased whenever it thawed. 



3. Throughout most of the year the numbers of bacteria have been 



nearly parallel with the moisture content; but these fluctuations 

 in winter as the soil was frozen and thawed have shown no re- 

 lation to the moisture. 



4. This increase during the winter seems to be due to an actual multi- 



plication of the bacteria, rather than to a mere rise of the organ- 

 isms from lower depths brought about by mechanical forces 

 alone. 



5. The greatest increase during the winter occurs in a group of bac- 



teria called here slow growers, a group readily distinguished 

 by its gelatin colonies from the two other large groups, rapid 

 liquefaction and Actinomycetes. 



6. Qualitative work with pure cultures has shown that certain types 



of soil bacteria occur throughout the year; but that others 

 apparently exist in the soil investigated for short periods only, 

 and tend to recur at other times under similar weather condi- 

 tions. The greatest variety of these types has been found in 

 fall and winter. 



7. This seasonal variation suggests a possible explanation for the in- 



crease during the winter. It is probable that a different class 



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