806 PRINCIPLES OF SOIL MICROBIOLOGY 



anthrax organisms through the soil and even isolated the organism from 

 the intestines of the worms. The soil may thus become a carrier of 

 human disease, as demonstrated in the case of V. cholerae and Bad. 

 typhosum. 13 Bac. botulinus is commonly found in the soil; the presence 

 of this organism has been demonstrated not only for soils infested with 

 the organism, but also for various virgin mountain and forest soils. 14 



Bac. tetani appears to be also universally distributed in the soil, es- 

 pecially in soils fertilized with animal manures and subject to the dust 

 of the streets. Nicolaier 15 demonstrated the presence of this organism 

 in over fifty per cent of the soils examined. It was even suggested 16 

 that the organism develops in rotting straw or manure, taking a part in 

 processes of decomposition. The presence of this organism in the soil 

 has also been ascribed to its presence in fecal secretions due to its 

 development in the intestine. 



The soil harbors various bacteria capable of causing plant diseases; 

 these include Bad. tumefaciens, Bad. solanacearum and Bac. phytoph- 

 thorus. 17 It has long been known 18 that the mosaic disease of tobacco 

 is caused by a filterable virus and this has since been found true of a 

 large number of similar plant diseases of the type known as infectious 

 chlorosis. The nature of this virus is problematical. It has been held 

 that in some cases the virus may persist in the soil but this remains as a 

 question deserving further critical study. 



Plant diseases caused by fungi found in the soil. Numerous fungi 

 capable of causing plant diseases find their natural or temporary habitat 

 in the soil. Such fungi have been isolated not only from cultivated 

 soils where they might have been introduced, but also from virgin soils 

 or from soils on which the particular host plant has never been grown 

 before. Fungi, like F. radicicola and Rhizodonia solani known to be 

 parasitic on the Irish potato, were isolated from Idaho soils never cropped 



14 Meyer, K. F., and Dubovsky, B. J. The distribution of the spores of B. 

 botulinus in California. Jour. Inf. Dis., 31: 41-55. 1923; also 56-58, 59-94 

 95-99, 100-109. 



15 Nicolaier, A. Beitrage zur Aetiologie des Wundstarrkrampfen. Inaug. 

 Diss. Gottingen. 1885; (Baumgart. Jahresber., 2: 270-272. 1886). 



16 Vincent, H. Le bacille du tetanos se multiplie-t-il dans le tube digestif 

 des animaux? Compt. Rend. Soc. Biol., 65: 12-14. 190S. 



17 Smith, E. F. An introduction to bacterial diseases of plants. Sanders Co., 

 Philadelphia, 1920. 



18 Beijerinck, M. W. Ueber ein Contagiura vivium fluidum als Ursache der 

 Fleckenkrankheit der Tabaksblatter. Centrbl. Bakt., II, 5: 27. 1899. 



