Lactobacillus acidophilus
Lactobacillus acidophilus Gram-staining
Taxonomy
Morphology
Cultural characteristics
Biochemical characters
Ecology
Pathogenicity
References
Phylum Firmicutes, Class Bacilli, Order Lactobacillales, Family Lactobacillaceae, Genus Lactobacillus [Group A lactobacilli (obligately
homofermentative),
Lactobacillus delbrueckii phylogenetic-group], Lactobacillus acidophilus  [(Moro 1900) Hansen and Mocquot
1970] Johnson, Phelps, Cummins, London and Gasser 1980.

Historical synonyms:  
Bacillus acidophilus Moro 1900, Thermobacterium intestinale Orla-Jensen, Orla-Jensen and Winther 1936.
Gram-positive rods with rounded ends (0.6-0.9  x 1.5-6 μm) occurring singly, in pairs,
and in short chains. Nonmotile (two strains from 89 were motile). Nonsporeforming.
Colonies on trypticase-glucose-agar are rough, showing fuzzy outlines; deep colonies
are irregularly shaped with radiate or ramified projections. No characteristic pigment.
Optimum growth temperature is 35-38 ºC. No growth at 15 ºC. Can grow at 45 ºC.
Variable growth at 22 and 48 ºC. Optimum pH 5.5-6.0. Can grow at pH 5-7.
Growth factor requirements: calcium pantothenate, folic acid, niacin, and riboflavin are
essential.
Isolated from the intestinal tract of humans and animals (turkeys, chickens, rats, hamsters), human mouth, vagina, sourdough, and
wine. It is used in food as feed aditivies, to achieve an improvement of health.
Local / bloodstream infections are very rare.
  1. Hammes W.P. and Hertel C., 2009. Genus I. Lactobacillus Beijerinck 1901. In: (Eds.) P.D. Vos, G. Garrity, D. Jones, N.R. Krieg, W.
    Ludwig, F.A. Rainey, K.-H. Schleifer, W.B. Whitman. Bergey’s Manual of Systematic Bacteriology, Volume 3: The Firmicutes,
    Springer, 465-511.
  2. Rogosa M., 1974. Genus I. Lactobacillus Beijerinck 1901. In: (Eds.) Buchanan R.E. and Gibbons N.E., Bergey’s Manual of
    Determinative Bacteriology, Eighth Edition, The Williams & Wilkins Company, Baltimore, 576-593.
  3. Johnson J.L., Phelps C.F., Cummins C.S., London J. and Gasser F., 1980. Taxonomy of the Lactobacillus acidophilus Group. IJSB
    vol. 30, no. 1, 53-68.
Obligately homofermentative (hexoses are fermented almost exclusively to lactic acid
by the Embden-Meyerhof pathway; pentoses or gluconate are not fermented).

Positive results for fermentation of: cellobiose, esculin, fructose, galactose, glucose
acid (without gas production),  lactose, maltose, mannose, salicin and sucrose.

Negative results for arginine hydrolysis, esculin hydrolysis, gelatin digested, H
2S
production, indole production, lecithinase, lipase, meat digestion, milk digestion,
nitrate reduction, urease,  fermentation of: arabinose, erythritol, gluconate, inositol,
mannitol, melezitose, rhamnose, ribose, sorbitol and xylose.

Variable results for starch hydrolysis, fermentation of: amygdalin, glycogen (weak
reaction), melibiose, raffinose, starch and trehalose.
(c) Costin Stoica
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