ARE SPORE-FORMING BACTERIA OF ANY SIGNIFI- 

 CANCE IN SOIL UNDER NORMAL CONDITIONS?^ 



H. JOEL CONN 



Agricultural Experiment Station, Geneva, New York 



Among the best known of the soil microorganisms are the 

 spore-forming bacteria. They have been described as soil- 

 bacteria ever since the first bacteriological investigations of 

 soil were made; and a more thorough taxonomic study has been 

 made of them than of any other bacteria except those which 

 have sanitary significance. It is seldom, however, that they 

 comprise more than 10 per cent of the total flora of soil. Hiltner 

 and Stormer (1903)2 recognizee^ three groups of colonies upon 

 gelatin plates made from soil: hquefiers, non-Hquefiers and 

 Streptothrix forms. The Hquefiers averaged about 5 per cent 

 of the total flora. The ordinary spore-forming bacteria in 

 soil are all rapid liquefiers and must have been included in this 

 5 per cent mentioned by Hiltner and Stormer. Similar results 

 have been obtained by various other investigators. 



The spore-forming bacteria, B. mycoides, B. cereus, and B. 

 megatherium, are practically always present in soil aid have 

 always been considered characteristic and important soil or- 

 ganisms. These bacteria develop on gelatin or agar plates 

 much more rapidly than those which comprise the othei 90 to 

 95 per cent of the soil flora, and form large, striking cdonies. 

 They are among the largest of all bacteria and have an unusually 

 interesting morphology, so it is not surprising that they have 

 been studied most extensively of all the soil organisms groying 



' Presented at Seventeenth Annual Meeting of the Society of American l3ac- 

 teriologists, Urbana, Illinois, December 29, 1915. 



- Hiltner, L. and Stormer, K. Studien fiber die Bakterienflora des Acler- 

 bodens, mit besonderer Beriiclsichtigung ihres Verhaltens nach einer Beha\d- 

 lung mit Schwefelkohlenstoff und nach Brache. Kaiserliches Gesundheitsai^t, 

 Biol. Abt. Land- u. Forstw. 3; ?. 445-545. 1903. 



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