CHAPTER XXXVII 



BACILLUS SUBTILIS 



(HAY BACILLUS) 



Bacillus subtilis is present in soil, dust, air and almost constantly upon hay. 

 It is not a pathogenic organism, but may enter chronic, neglected wounds or 

 ulcers and exist there as a saprophyte. Frequently is it found in contaminated 

 milk, blood serum, infusions and laboratory culture media. It is a spore-form- 

 ing bacillus and these spores are very resistant, withstanding boiling for 5 or 10 

 minutes. 



Morphology. Bacillus subtilis is from 4 to 8 ju by about 0.7 /z, has rounded 



FIG. 27. BACILLUS SUBTILIS. STAINED BY GRAM'S METHOD. 

 (4 X eyepiece and Ma oil immersion objective.) 



-ends, is slightly motile, carries spores near, but not exactly, in the middle, and 

 is arranged singly, in pairs and in long filaments. 



Staining. It stains readily with all the usual anilin stains and is Gram 

 positive. 



Growth.' Bacillus subtilis is aerobic, and, to a degree, anaerobic. It grows 

 well between 2oC. and 37C. on all culture media, forming a whitish sediment 

 in fluid media and forming on solid media round, irregular-edged, whitish 

 colonies which tend to coalesce. Gelatin is liquefied. 



To insure sterilization by hot air a temperature of i5oC. must be maintained 

 for several hours. 



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