762 PRINCIPLES OF SOIL MICROBIOLOGY 



the disinfectant is evaporated, there is a rapid increase in the non-lique- 

 fying forms; the activity of the actinomyces and gelatin liquefying 

 bacteria lags very much behind. After the maximum of bacterial 

 activities is attained, a gradual decrease follows and within about a 

 year the flora of the treated soil has reached the level of the untreated 

 soil. 



The most active bacteria, after partial sterilization, were found 75 

 to be Bac. butyricus, Bac. mycoides, Bac. megatherium, Bac. arborescens, 

 Microc. ochraceus luteus and, to a less extent, Bact. fluoresceins 

 liquefaciens. 



Various other investigators found 76 actinomyces to be decidedly 

 injured by treatment with CS 2 ; the Bac. mycoides group was less affected, 

 the spore formers being especially resistant. Legume bacteria (peas) and 

 denitrifying bacteria (B. stutzeri) are rapidly killed, within two and a 

 half hours; Bact. coli, Bact. prodigiosum, Bact. vulgar e, Micr. ureae 

 survive four hours. Staphylococci are very resistant, surviving 

 forty-eight hours. Az. chroococcum survives in moist soil impregnated 

 with fumes of CS 2 for forty-eight hours, but it is destroyed after a 

 longer treatment. The vegetative forms are destroyed in twenty- 

 four hours, but the spores survive. A comparison of the influence 

 of antiseptics upon bacteria and protozoa brought out the fact that 

 smaller doses are required to kill the organisms in solution than in 

 soil. 77 The actual concentration of the antiseptic required to destroy 

 amoebae in the soil is so large as to become unapplicable for purposes 

 of partial sterilization, which has as its aim the destruction of the 

 protozoa. Even 60 per cent CS 2 did not kill the cysts of amoebae in 

 the soil; the same was true of 15 per cent ether, 6 per cent chloroform, 

 25 per cent CaO, 30 parts per thousand of chlorine water, less than 15 

 per cent toluol and 5 per cent CaS. Bacterial spores were found to 

 be more resistant to the antiseptic than the cysts of amoebae. Active 

 amoebae have a lower resistance than non-spore-forming bacteria, 

 but the latter are more readily destroyed than cysts of amoebae. The 

 data did not justify any claim for an equilibrium between the numbers 

 of amoebae and bacteria in the soil, the fluctuations of the numbers of 



76 Truffaut and Bezssonoff, 1920-21 (p. 37); Compt. Rend. Acad. Agr. France, 

 4: 1049-1057, 1030-103S. 1918. 



76 Maassen and Behn, 1924 (p. 756). 



77 Sewertzoff, L. B. The effect of some antiseptics on soil amoeboe in par- 

 tially sterilized soils. Centrbl. Bakt. II, 65: 278-291. 1925; Ibid I. Or., 92: 

 151-158. 1924. 



