Lactococcus lactis
Lactococcus lactis subsp. lactis on Blood Agar
Taxonomy
Morphology
Cultural characteristics
Biochemical characters
Ecology
Pathogenicity
References
1873) Schleifer et al. 1986. Type species of the genus.
Old synonyms:
Bacterium lactis Lister 1873, Streptococcus lactis (Lister 1873) Lohnis 1909.
Reacts with Lancefield serological group N antiserum.

Lactococcus lactis subspecies:
1. Lactococcus lactis subsp. cremoris (Orla-Jensen 1919) Schleifer et al. 1986. Old synonyms: Streptococcus cremoris Orla-Jensen
1919,
Streptococcus lactis subsp. cremoris (Orla-Jensen 1919) Garvie and Farrow 1982, Streptococcus hollandicus Scholl 1891,
Streptococcus lactis B Ayers et al. 1924;
2. Lactococcus lactis subsp. hordniae (ex Latorre-Guzman et al. 1977) Schleifer et al. 1986. Old synonym: Lactobacillus hordniae
Latorre-Guzman et al. 1977;
3. Lactococcus lactis subsp. lactis (Lister 1873) Schleifer et al. 1986. Old synonyms: Streptococcus lactis (Lister 1873) Lohnis 1909,
Streptococcus lactis subsp. lactis (Lister 1873) Garvie and Farrow 1982, Bacterium lactis Lister 1873.
4. Lactococcus lactis subsp. tructae Perez et al. 2011.

L. lactis subsp. lactis also includes the strains of Streptococcus lactis subsp.
diacetilactis
(ex Matuszewski et al. 1936) Garvie and Farrow 1982; and the strains
of
Lactobacillus xylosus Kitahara 1938.
Gram-positive ovoid cells elongated in the direction of the chain. Grouped mostly in
pairs or short chains. Nonmotile. Endospores are not formed.
Colonies on blood agar or nutrient agar are nonpigmented, circular, smooth, and
entire. Nonhemolytic, but some strains may produce a weak alpha-hemolysis. Grow
at 10 ºC but not at 45 ºC. Grow in 0.1% methylene blue milk and 2% NaCl.
Facultatively anaerobic.
Subspecies "cremoris" and "lactis" have been isolated from raw milk, dairy products,
whey, milking machines, and the udders, the saliva and on the skin of cows and
bulls, grass, soil, silage, plant material, including fresh and frozen corn, corn silks,
navy beans, cabbage, lettuce, peas, wheat middlings, grass, clover, potatoes,
cucumbers, and cantaloupe.
Strains of
L. lactis subsp. lactis have been also isolated from the intestinal tracts of
freshwater fish, milk from cows with mastitis, tonsils of cats, dogs and goats.
Subspecies "hordniae" has been isolated from the leafhopper
Hordnia circellata.
Subspecies "tructae" has been isolated from the intestinal mucus of brown trout
(
Salmo trutta) and rainbow trout (Oncorhynchus mykiss).

Lactococci are usually not found in fecal material or soil. They can survive only hours
in the intestinal tract.
Several
L. lactis subsp. lactis strains can produce bacteriocins (nisin A and Z) which
can inhibit the growth of a wide range of Gram-positive bacteria.
Subspecies "cremoris" and "lactis" are used as starter cultures for the manufacture of fermented dairy products like cheeses, sour
milk, and sour cream.
Lactococcus lactis subsp. lactis biovar diacetylactis produce diacetyl, an aromatic compound.
Generally they are not pathogenic, but have been rarely isolated from human cases of urinary tract and wound infections, and from
patients with endocarditis.
  1. Tania Perez, Jose Luis Balcazar, Alvaro Peix, Angel Valverde, Encarna Velazquez, Ignacio de Blas, and Imanol Ruiz-Zarzuela
    Lactococcus lactis subsp. tructae subsp. nov. isolated from the intestinal mucus of brown trout (Salmo trutta) and rainbow trout
    (Oncorhynchus mykiss). Int J Syst Evol Microbiol August 2011.
  2. Matters Relating to the International Committee on Systematic Bacteriology: Validation of the Publication of New Names and New
    Combinations Previously Effectively Published Outside the IJSB:List No. 20. Int J Syst Bacteriol April 1986 36:354-356.
  3. Michael Teuber, 2009. Genus II. Lactococcus Schleifer, Kraus, Dvorak, Kilpper-Balz, Collins and Fischer 1986, 354 VP. 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, 711-722.
  4. Ellen I. Garvie and John A. E. Farrow. NOTES: Streptococcus lactis subsp. cremoris (Orla-Jensen) comb. nov. and Streptococcus
    lactis subsp. diacetilactis (Matuszewski et al.) nom. rev., comb. nov. Int J Syst Bacteriol October 1982 32:453-455.
  5. M. D. Collins, J. A. E. Farrow, B. A. Phillips, and O. Kandler. Streptococcus garvieae sp. nov. and Streptococcus plantarum sp. nov.
    J Gen Microbiol November 1983 129:3427-3431.
Positive results for esculin hydrolysis, leucine arylamidase, acid production from:
glucose, fructose, mannose, N-acetylglucosamine, and trehalose. Most strains
produce acid from arbutin, cellobiose, beta-gentiobiose, and salicin. A few strains are
pyrrolidonylarylamidase positive. Some strains (
L. lactis subsp. lactis biotype
diacetilactis
) can utilize citrate.

Negative results for alkaline phosphatase, alpha-galactosidase, beta-galactosidase,
beta-glucuronidase, catalase, acid production from: D- or L-arabinose, D- or
L-arabitol, adonitol, 2-ketogluconate, 5-ketogluconate, dulcitol, erythritol, D-fucose,
L-fucose, gluconate, glycerol, glycogen, inositol, melezitose, alpha-methyl-
D-glucoside, alpha-methyl-D-mannoside, D-lyxose,  rhamnose, L-sorbose, sorbitol,
D-tagatose, D-turanose, xylitol, and L-xylose. Most strains of
L. lactis subsp. cremoris
do not produce acid from beta-gentiobiose, salicin, and trehalose.

Variable results for acid production from inulin, and starch.
(c) Costin Stoica
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Legend: +  positive 90-100%, - negative 90-100%, [+] positive 75-89%, [-] negative 75-89%, d positive 25-74% of strains
Subspecies
Growth in
4% NaCl
Growth at
4 ºC
Arginine
hydrolysis
Hippurate
hydrolysis
Amygdalin
fermentation
Galactose
fermentation
Lactose
fermentation
lactis
+
+
+
+
d
+
+
cremoris
-
-
-
+
-
+
+
hordniae
-
 
+
-
-
-
-
tructae
+
 
+
+
+
+
+
Differential characters of Lactococcus lactis subspecies:
Subspecies
Maltose
fermentation
Melibiose
fermentation
Mannitol
fermentation
Raffinose
fermentation
Ribose
fermentation
Sucrose
fermentation
D-xylose
fermentation
lactis
+
-
d
-
+
d
d
cremoris
-
-
d
-
-
-
-
hordniae
-
-
-
-
-
+
-
tructae
+
[+]
+
[+]
+
+
-