SEPARATION OF SOIL PROTOZOA' 



By Nicholas Kopelofp, H. Clay Lint, and David A. Coleman, 

 Research Fellows, The New Jersey College for the Benefit of Agriculture and Mechanic Arts 



Some interesting problems have been suggested by the contention of 

 Russell and Hutchinson (9, lo)^ that protozoa are one of the limiting 

 factors in soil fertiUty, because they feed upon and consequently limit 

 the numbers of soil bacteria. Before the agricultural scientist can 

 successfully formulate a complete explanation of the phenomena con- 

 cerned with the function of protozoa in soils it is essential to establish 

 certain fundamentals in methodology. Russell and Hutchinson (9, 10) 

 and Cunningham (2, 3) have presented some valuable information con- 

 cerning the depression of bacterial numbers as a result of inoculation 

 with cultures of protozoa. The writers entered upon an investigation of 

 a similar nature, with an attempt to base their work upon the use of 

 protozoa-free cultures of bacteria, and bacteria-free cultures of protozoa. 



But little mention is to be found in the literature regarding the separa- 

 tion of the different kinds of protozoa from each other and from bacteria. 

 Russell and Hutchinson (9, 10) and Fred (4) have employed an efficient 

 method of filtration for obtaining cultures of protozoa, but they do not 

 offer any further experimental data concerning such separations. Cun- 

 ningham (2, 3) has made use of a single-drop method for obtaining 

 protozoa-free cultures of bacteria, based on the transfer to a suitable 

 medium of a drop from a protozoan culture which upon microscopic 

 examination revealed no protozoa. On the other hand, he does not 

 describe any direct method for obtaining a bacteria-free culture of 

 protozoa. Jordan (5, p. 469) mentions a method which might prove 

 somewhat tedious — that is, having protozoa pass through concentric 

 rings of dead bacteria on a culture plate until they had no living adher- 

 ing bacteria. He refers also to Frosch's ^ method of separation by 

 means of a sodium-carbonate solution. Richter (8) suggests the use of 

 a high-gelatin medium which would suppress the bacterial growth of 

 liquefying organisms. Biffi and Razzeto (i) give an account of the 

 passage of protozoa through semipermeable filters after a considerable 

 period of time has elapsed. 



The writers are in agreement with Biffi and Razzeto regarding the 

 importance of the time element in filtration, since it has been observed 

 that protozoa have been able to work through the pores of a filter in a 

 short time. 



In the work under consideration — namely, the separation of flagellates 

 from ciliates — an 8-day-old culture of soil organisms was employed. 



1 From tJie Departments of Soil Chemistry and Bacteriology, New Jersey Experiment Station, New 

 Bnmswick, N. J. 



2 Reference is made by number to " Literature cited," p. 139-140. 



5 Frosch, P. Zur Frage der Reinziichtung der Amoben. In Centbl. Bakt. [etc.], Abt. i, Bd. 21, No. 

 24/25. P- 926-932. 1897. 



Journal of Agricultural Research, Vol. V, No. 3 



Dept. of Agriculture, Washington, D. C. Oct. 18, 1915 



ah N. J.— 2 



(137) 



