437 



Investigations on Protozoa in Relation to the Factor Limiting 

 Bacterial Activity in Soil. 



By T. Goodey, M.Sc., Protozoologist, Eesearch Laboratory in Agricultural 

 Zoology, University of Birmingham. 



(Communicated by Prof. F. W. Gamble, F.E.S. Eeceivecl December 3, 1914.) 



Introduction. 



In the course of my work on soil protozoa particularly in relation to the 

 question of the partial sterilisation of soil, I had occasion to work with some 

 of the old stored soils kept at the Eothamsted Experimental Station, 

 Harpenden, at which laboratory the work here recorded was commenced. 

 These soils are remarkable for the length of time they have been stored, 

 67 years being the longest period, and for the fact that in many cases the 

 original samples put up in large bottles have remained untouched since the 

 day on which they were bottled. 



Preliminary cultures of some of these soils in hay-infusion were begun in 

 1912 to ascertain the character of the protozoan fauna, if such still persisted 

 in them. From these cultures it was found that in a mixed sample from 

 Broadbalk, bottled in 1846 and containing about 3 per cent, of water by 

 weight, no protozoa were present, whilst in another mixed sample taken from 

 six bottles of Barnfield soil, put up in 1870 and containing about 10 per cent, 

 of water by weight, amoebse and flagellates but no ciliates were present. 



Quantities of these two soils were taken and were submitted to partial 

 sterilisation treatment in order to find out if the limiting factor usually 

 eliminated by partial sterilisation was present in them. The results obtained 

 by bacterial counts over a period of about 281 days showed that in the 1846 

 soil no factor limiting bacterial activity was present, whilst in the 1870 soil 

 the limiting factor was present.* 



As a result of this work I decided to use some of the 1846 soil for 

 inoculation with different species of protozoa obtained from soil, in order to test 

 if possible their power to act as the factor limiting bacterial activity. The 

 protozoa selected for culture and inoculation into separate samples of soil were 

 the following : — Colpoda cucullus, Col. maupasii, Col. steinii, and Vorticella 

 microstoma. Amoeba sps. ? and Flagellate sps. ? were obtained by culture 

 from the 1870 soil which, as already mentioned, had been found to contain 



* This work was carried out in collaboration with Dr. H. B. Hutchinson at 

 Eothamsted. 



VOL. LXXXVIII. — B. 2 N 



