764 LACTOBACILLUS 



Agar Plate. — No growth. 



Whey Agar Plate. — Usual type of colony is irregularly round, greyish- white, 0*5-1 -5 mm. 

 in diameter, of loose curled structure with a streaming filamentous edge ; micro- 

 scopically these colonies are typically rhizoid. Sometimes, especially in old labora- 

 tory cultures, a rounder, more regular colony is formed, with a smooth or sUghtly 

 fissured surface and an entire edge. 



Whey Agar Shake Tubes. — Deep colonies are lenticular or umbilicated, whitish incolour, 

 and 1 mm. in diameter. 



Whey Agar Stab. — Fihform growth, beaded, later with horizontal ramifications ; no 

 surface growth ; medium is clouded. 



Gelatin. — Not liquefied. 



2 per cent. Glucose Broth. — Heavy uniform turbidity. 



Potato. — No growth. 



Resistance. — Killed by moist heat at 60° C. in 1 hour. Is very resistant to acids ; glucose 

 broth cultures at 37° C. remain viable for about 6 days. 



Metabolism.— Facvltative anaerobe ; is said by some authors to prefer anaerobic con- 

 ditions. No growth at 15° C. ; grows very slightly at 25° C. ; growth is poor 

 under 35° C. ; optimum temperature for growth is 44-45° C ; usually grows at 

 50° C. No pigment, toxin, or hsemolysin formed. Is resistant to acids, but grows 

 best in a neutral or sUghtly alkaline medium. Difficult to cultivate ; growth in 

 most media is feeble, and when freshly isolated it will grow only on media con- 

 taining whey or malt, or in rmlk. 



Biochemical. — Sugar reactions described differently by different authors. Is generally 

 considered to produce acid in glucose, lactose, and sometimes Isevulose, but not 

 in maltose, sucrose, mannitol, or raffinose. Lactic acid is the chief acid formed 

 from fermentable carbohydrates. L.M. acid and coagulation in 18 hours at 37° C. ; 

 the clot does not contract. Indole negative. White and Avery's Type A in milk 

 produces 2-7-3-7 per cent, of lactic acid of the inactive variety ; Type B produces 

 only 1-2-1 -6 per cent, of lactic acid, of the Isevo-rotatory variety. 



Antigenic Structure. — Nothing known. 



Pathogenicity. — Non-pathogenic to man and animals. 



Grigoroff's Bacillus C. — Isolated from kisselo-mleko, the fermented milk of Bulgaria, 

 by Grigoroff in 1905. Is a streptobacillus forming short rods arranged in chains of foxu" 

 to twenty members. Gram-positive. Cultm-aUy it resembles L. bulgaricus, but is more 

 heat resistant, requiring an exposure of 1 hom- at 70° C. to kill it. Produces acid in glucose, 

 Isevulose, lactose, sucrose, and glycerol, but not in maltose, mannitol, or dulcitol. Pro- 

 duces acid and clot in milk, the acid being inactive lactic acid. 



Lactobacillus exilis. — ^IsoIated by Tissier in 1900 from the faeces of children on milk 

 or mixed diets. It is a thin, straight, slender baciUus, arranged singly, in pairs, or in 

 chains of four or five elements ; non-pleomorphic. Non-motile. Gram-positive. On 

 agar plates it forms very tiny bluish colonies with entire edges in 48 hours, no bigger 

 than the point of a needle. On glucose agar they may reach 0-5 mm. in diameter. In 

 broth there is a slight filamentous deposit without turbidity. No growth in gelatin. 

 In deep glucose agar small, oval, regular colonies with entire edges are formed throughout 

 the tube. Cultures die out in 10 to 15 days. Grows at 20° C., but better at 37° C. Grows 

 both aerobically and anaerobically. Milk is coagulated in 8 to 10 days ; there is no retrac- 

 tion of the clot. Non-pathogenic for mice. Differs from L. acidophilus in being slender 

 and constant in morphology, in forming small regidar colonies in agar shake cultures, 

 and in being less resistant to acid. Cruickshank (1925) regards L. exilis as probably the 

 aerobic phase of L. bifidus. 



The Boas-Oppler Bacillus. — Observed microscopically in the stomach contents of 

 patients with gastric carcinoma by Oppler in 1895, working in Boas' chnic in Berlin. He 

 did not succeed in cultivating it. In stomach contents it occurs as a rather slender bacillus. 



