BACILLUS SUBTILIS 



849 



Fig. 183.—^. subtilis. 



Smooth type of colony. Agar 



24 hours, 37° C. ( X 8). 



Variants I and III formed smooth, circular, shiny colonies with regular margins ; 

 II formed " medusa-head " colonies ; while IV formed slightly irregular colonies 

 with an uneven surface and a rather granular tex- 

 ture. All four variants had the same heat-stable 

 somatic antigen. Variants I and II had in addition 

 a common heat-labile flagellar antigen. 



Bacillus subtilis Cohn emendavit Prazmowski 



Synonyms. — Hay bacillus. 

 Habitat. — Hay, dust, milk, soil, water. 

 Morphology. — Slender rods, 1-5-3 /li X 0-5-0-8 /<, straight 

 or curved, rounded ends, occurring singly or in 

 short chains. Actively motile by 8-12 peritrichate 

 flagella. Non-capsulated. Spores are oval, 1-5 ^m 

 X 0-6 ju, formed sub -terminally, do not cause 

 bulging of the cell, and germinate equatorially 

 without sjihtting along the transverse axis ; appear 

 on agar m 18 hours. Gram-positive. Non-acid-fast. 

 Agar Plate. — Irregularly circular colonies, 4-6 mm. in diameter, slightly raised, greyish- 

 yellow, and having a darker crumbly centre surrounded by a lighter periphery 

 with a curled edge. Surface is finely granular ; membranous or friable consistency ; 

 adherent to medium ; emulsification rather difficult. Resemble anthrax colonies. 

 Agar Slope. — Abundant, confluent, greyish-white, raised, opaque, sometimes wrinkled 

 growth, with an undulate and finely serrated edge and a mealy surface. Mem- 

 branous consistency, adherent to medium, enmlsifying fairly 

 easily. 

 Gelatin Stab. — Filiform growth with rapid infundibuUform or 

 saccate liquefaction ; thick wliite membrane on surface 

 adhering to the sides of the tube. 

 Broth. — Moderate turbidity, slight deposit, with formation of a 

 thick wrinkled surface membrane adhering to the walls of 

 the tube ; pellicle often sinks to the bottom. 

 Blood Serum. — Tliick folded membrane ; liquefaction. 

 Potato. — Thick, yeUowish-white, raised, dull, creamy growth, 

 later sprinkled with dry white granules, giving a mealy 

 appearance. 

 Biochemical. — Acid, no gas, in glucose, maltose and sucrose. 

 Indole — . M.R. — ; V.P. ^ ; nitrates reduced to nitrites. 

 HjS — ; NH3-I-; methylene blue reduced; catalase -f-. 

 Litmus milk partially clotted, peptonized, and decolorized 

 from above downwards. Starch is hydrolysed. 

 Metabolic. — Aerobe, facultative anaerobe. Opt. temp. 37°C. 



Limits 15-55° C. 

 Pigment. — Cream to chestnut-brown. 



Nutritional. — Grows freely on ordinary media ; growth not im- 

 proved by blood, serum, or glucose. 

 Hcemolysis. — (i-type on horse blood agar plates given by some 



strains. 

 Resistance. — Spores withstand boibng for hours. 

 Antigenic Structure. — Little exact knowledge available. Motile 

 strains appear to have a heat-labile flagellar and a heat- 

 stable somatic antigen. Spore antigen is diflFerent from 

 bacillary antigen. 



Fig. ]84.— 5 



tilts. 



sub- 



In gelatin stab cul- 

 ture, 4 days, 20°C., 

 showing infundi- 

 buliform liquefac- 

 tion. 



