AEROBIC SPORE-BEARING NON-PATHOGENIC BACTERIA 513 

 SPORE-BEARING BACTERIA IN SOIL 



BY C. A. LAUBACH AND J. L. RICE 



In a preliminary investigation of the germ content of soils ob- 

 tained in the neighborhood of Baltimore the attempt was made 

 to verify the results already obtained by the work on milk, dust 

 and water and to determine whether the types previously iso- 

 lated from the other sources could also be found in this environ- 

 ment. Altogether some 63 cultures were obtained and found to 

 consist of the following types : 



Baltimore soil 



Bacillus cereus Frankland 28 



Bacillus mesentericus (Flijgge) Migula 15 



{Bacillus mesentericus fuscus FliJgge.) 



Bacillus subtilis (Ehrenberg) Cohn 8 



Bacillus vulgatus (Fliigge) Trevisan 6 



(Bacillus mesentericus vulgatus Flugge.) 



Bacillus brevis Migula 3 



Bacillus megatherium De Bary 1 



Bacillus mycoides Flugge 1 



Bacillus petasites Gottheil 1 



It is interesting to note the great predominance of Bacillus ce- 

 reus which makes up nearly half the isolations, the relative in- 

 frequency of Bacillus subtilis and the rarity of Bacillus megather- 

 ium, Bacillus petasites, and Bacillus mycoides. Bacillus mesen- 

 tericus appears also as a more frequent isolation than Bacillus 

 vulgatus. 



Eight different samples of raw and heated soil were selected for 

 this examination, some samples being plated immediately, others 

 being incubated at 37°C. for 48 hours before plating. It was 

 hoped that a great diversity of organisms would be obtained by 

 this method and no special attempt was made to estimate with 

 any great accuracy the germ content of any particular sample. 

 In general it was noted however, that heated soil furnished a 

 greater variety of types than unheated soil and that the incuba- 

 tion of the sample was distinctly an unfavorable factor since one 

 type tended to overgrow the other types present. It was thought 

 that the prevalence of Bacillus cereus might be due to its power of 



