LEUCONOSTOC

16 plus species including:

SPECIES

Leuconostoc lactis
Leuconostoc mesenteroides
subsp. cremoris
subsp. dextranicum
subsp. mesenteroides
Leuconostoc oenos
Leuconostoc paramesenteroides

MICROSCOPIC APPEARANCE

Gram Stain: Positive.
Morphology: Spherical, but often lenticular coccoid cells in pairs and chains. Sometimes short rods with rounded ends in long chains.
Size: 0.5-0.7 micrometers by 0.7-1.2 micrometers.
Motility: Non-motile.
Capsules: None.
Spores: None.

MACROSCOPIC APPEARANCE

Leuconostoc grows slow on media containing sucrose, and produces small colonies < 1mm in diameter. Colonies may be slimy, smooth, round, and grayish in nature. Broth cultures often have uniform turbidity but strains forming long chains tend to sediment.

KEY BIOCHEMICAL REACTIONS

METABOLIC PROPERTIES

Facultatively anaerobic. Leuconostoc spp. are Chemoorganotrophic with obligate requirement for a fermentable carbohydrates. They require nutritionally rich media including complex growth factors and amino acids. They are fermentative and respiratory. Glucose is fermented mainly to lactic acid, ethanol and CO 2 . Unlike other gram-positive bacilli, Leuconostoc spp. show resistance to vancomycin.

HABITAT

Leuconostoc are found on plants and to a lesser extent in milk and milk products. L. mesenteroides subsp. cremoris and L. lactis may be components of cheese and butter starters. Dextran-forming species occur on sugar cane and sugar beet where they may cause widespread spoilage. L. oenos is known only in wine and related habitats; no other Leuconostoc has been isolated from these sources.

PATHOGENICITY

Non-pathogenic to plants and animals, but Leuconostoc citreum and Leuconostoc pseudomesenteroides have been isolated from human sources. Wide spread spoilage of sugar cane and sugar beet plants has been noted, where dextran-forming species of Leuconostoc occur.

RECOMMENDED MEDIA

For culture: Skim Milk and MRS Broth, MRS Agar, and Tomato Juice Agar.
For selective isolation: Media containing crystal violet or thallium acetate.
For maintenance: Tomato Juice Agar stabs, Litmus Milk with 0.3% Yeast, 1.0% Glucose, and 1.0% Calcium Carbonate. (2)

INCUBATION

Temperature: 20-30 degrees C.
Time: 24-48 hours under 5% CO 2 .
Atmosphere: Anaerobic; requires fermentable carbohydrate for growth.
Optimum pH: 4.0-6.0 (in Glucose Broth).

REFERENCES

1. Holt, J.G., et al. 1994. Bergey's Manual of Determinative Bacteriology , 9th ed. Williams & Wilkins, Baltimore, MD.

2. Holt, J.G., et al. 1986. Bergey's Manual of Systemic Bacteriology , Vol. I & II. Williams & Wilkins, Baltimore, MD.

3. The Oxoid Vade-Mecum of Microbiology . 1993. Unipath Ltd., Basingstoke, UK.

4. Murray, P.R., et al. 1995. Manual of Clinical Microbiology , 6th ed. American Society for Microbiology, Washington, D.C.

5. Internet: www.hardlink.com /Bacterial Database Search, February, 1998.

6. Hensyl, B.R., et al. 1990. Stedman's Medical Dictionary , 25th ed. Williams & Wilkins, Baltimore, MD.

7. Koneman, et al. 1997. Color Atlas and Textbook of Diagnostic Microbiology , 5th ed. Lippincott, Philadelphia, PA.


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